// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2003-2006, Cluster File Systems, Inc, info@clusterfs.com
 * Written by Alex Tomas <alex@clusterfs.com>
 *
 * Architecture independence:
 *   Copyright (c) 2005, Bull S.A.
 *   Written by Pierre Peiffer <pierre.peiffer@bull.net>
 */

/*
 * Extents support for EXT4
 *
 * TODO:
 *   - ext4*_error() should be used in some situations
 *   - analyze all BUG()/BUG_ON(), use -EIO where appropriate
 *   - smart tree reduction
 */

#include <linux/fs.h>
#include <linux/time.h>
#include <linux/jbd2.h>
#include <linux/highuid.h>
#include <linux/pagemap.h>
#include <linux/quotaops.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/fiemap.h>
#include <linux/iomap.h>
#include <linux/sched/mm.h>
#include "ext4_jbd2.h"
#include "ext4_extents.h"
#include "xattr.h"
#include <kunit/static_stub.h>

#include <trace/events/ext4.h>

/*
 * used by extent splitting.
 */
#define EXT4_EXT_MAY_ZEROOUT    0x1  /* safe to zeroout if split fails \
                                        due to ENOSPC */
static struct ext4_ext_path *ext4_split_convert_extents(
        handle_t *handle, struct inode *inode, struct ext4_map_blocks *map,
        struct ext4_ext_path *path, int flags, unsigned int *allocated);

static __le32 ext4_extent_block_csum(struct inode *inode,
                                     struct ext4_extent_header *eh)
{
        struct ext4_inode_info *ei = EXT4_I(inode);
        __u32 csum;

        csum = ext4_chksum(ei->i_csum_seed, (__u8 *)eh,
                           EXT4_EXTENT_TAIL_OFFSET(eh));
        return cpu_to_le32(csum);
}

static int ext4_extent_block_csum_verify(struct inode *inode,
                                         struct ext4_extent_header *eh)
{
        struct ext4_extent_tail *et;

        if (!ext4_has_feature_metadata_csum(inode->i_sb))
                return 1;

        et = find_ext4_extent_tail(eh);
        if (et->et_checksum != ext4_extent_block_csum(inode, eh))
                return 0;
        return 1;
}

static void ext4_extent_block_csum_set(struct inode *inode,
                                       struct ext4_extent_header *eh)
{
        struct ext4_extent_tail *et;

        if (!ext4_has_feature_metadata_csum(inode->i_sb))
                return;

        et = find_ext4_extent_tail(eh);
        et->et_checksum = ext4_extent_block_csum(inode, eh);
}

static struct ext4_ext_path *ext4_split_extent_at(handle_t *handle,
                                                  struct inode *inode,
                                                  struct ext4_ext_path *path,
                                                  ext4_lblk_t split, int flags);

static int ext4_ext_trunc_restart_fn(struct inode *inode, int *dropped)
{
        /*
         * Drop i_data_sem to avoid deadlock with ext4_map_blocks.  At this
         * moment, get_block can be called only for blocks inside i_size since
         * page cache has been already dropped and writes are blocked by
         * i_rwsem. So we can safely drop the i_data_sem here.
         */
        BUG_ON(EXT4_JOURNAL(inode) == NULL);
        ext4_discard_preallocations(inode);
        up_write(&EXT4_I(inode)->i_data_sem);
        *dropped = 1;
        return 0;
}

static inline void ext4_ext_path_brelse(struct ext4_ext_path *path)
{
        brelse(path->p_bh);
        path->p_bh = NULL;
}

static void ext4_ext_drop_refs(struct ext4_ext_path *path)
{
        int depth, i;

        if (IS_ERR_OR_NULL(path))
                return;
        depth = path->p_depth;
        for (i = 0; i <= depth; i++, path++)
                ext4_ext_path_brelse(path);
}

void ext4_free_ext_path(struct ext4_ext_path *path)
{
        if (IS_ERR_OR_NULL(path))
                return;
        ext4_ext_drop_refs(path);
        kfree(path);
}

/*
 * Make sure 'handle' has at least 'check_cred' credits. If not, restart
 * transaction with 'restart_cred' credits. The function drops i_data_sem
 * when restarting transaction and gets it after transaction is restarted.
 *
 * The function returns 0 on success, 1 if transaction had to be restarted,
 * and < 0 in case of fatal error.
 */
int ext4_datasem_ensure_credits(handle_t *handle, struct inode *inode,
                                int check_cred, int restart_cred,
                                int revoke_cred)
{
        int ret;
        int dropped = 0;

        ret = ext4_journal_ensure_credits_fn(handle, check_cred, restart_cred,
                revoke_cred, ext4_ext_trunc_restart_fn(inode, &dropped));
        if (dropped)
                down_write(&EXT4_I(inode)->i_data_sem);
        return ret;
}

/*
 * could return:
 *  - EROFS
 *  - ENOMEM
 */
static int ext4_ext_get_access(handle_t *handle, struct inode *inode,
                                struct ext4_ext_path *path)
{
        int err = 0;

        if (path->p_bh) {
                /* path points to block */
                BUFFER_TRACE(path->p_bh, "get_write_access");
                err = ext4_journal_get_write_access(handle, inode->i_sb,
                                                    path->p_bh, EXT4_JTR_NONE);
                /*
                 * The extent buffer's verified bit will be set again in
                 * __ext4_ext_dirty(). We could leave an inconsistent
                 * buffer if the extents updating procudure break off du
                 * to some error happens, force to check it again.
                 */
                if (!err)
                        clear_buffer_verified(path->p_bh);
        }
        /* path points to leaf/index in inode body */
        /* we use in-core data, no need to protect them */
        return err;
}

/*
 * could return:
 *  - EROFS
 *  - ENOMEM
 *  - EIO
 */
int __ext4_ext_dirty(const char *where, unsigned int line,
                     handle_t *handle, struct inode *inode,
                     struct ext4_ext_path *path)
{
        int err;

        KUNIT_STATIC_STUB_REDIRECT(__ext4_ext_dirty, where, line, handle, inode,
                                   path);

        WARN_ON(!rwsem_is_locked(&EXT4_I(inode)->i_data_sem));
        if (path->p_bh) {
                ext4_extent_block_csum_set(inode, ext_block_hdr(path->p_bh));
                /* path points to block */
                err = __ext4_handle_dirty_metadata(where, line, handle,
                                                   inode, path->p_bh);
                /* Extents updating done, re-set verified flag */
                if (!err)
                        set_buffer_verified(path->p_bh);
        } else {
                /* path points to leaf/index in inode body */
                err = ext4_mark_inode_dirty(handle, inode);
        }
        return err;
}

#define ext4_ext_dirty(handle, inode, path) \
                __ext4_ext_dirty(__func__, __LINE__, (handle), (inode), (path))

static ext4_fsblk_t ext4_ext_find_goal(struct inode *inode,
                              struct ext4_ext_path *path,
                              ext4_lblk_t block)
{
        if (path) {
                int depth = path->p_depth;
                struct ext4_extent *ex;

                /*
                 * Try to predict block placement assuming that we are
                 * filling in a file which will eventually be
                 * non-sparse --- i.e., in the case of libbfd writing
                 * an ELF object sections out-of-order but in a way
                 * the eventually results in a contiguous object or
                 * executable file, or some database extending a table
                 * space file.  However, this is actually somewhat
                 * non-ideal if we are writing a sparse file such as
                 * qemu or KVM writing a raw image file that is going
                 * to stay fairly sparse, since it will end up
                 * fragmenting the file system's free space.  Maybe we
                 * should have some hueristics or some way to allow
                 * userspace to pass a hint to file system,
                 * especially if the latter case turns out to be
                 * common.
                 */
                ex = path[depth].p_ext;
                if (ex) {
                        ext4_fsblk_t ext_pblk = ext4_ext_pblock(ex);
                        ext4_lblk_t ext_block = le32_to_cpu(ex->ee_block);

                        if (block > ext_block)
                                return ext_pblk + (block - ext_block);
                        else
                                return ext_pblk - (ext_block - block);
                }

                /* it looks like index is empty;
                 * try to find starting block from index itself */
                if (path[depth].p_bh)
                        return path[depth].p_bh->b_blocknr;
        }

        /* OK. use inode's group */
        return ext4_inode_to_goal_block(inode);
}

/*
 * Allocation for a meta data block
 */
static ext4_fsblk_t
ext4_ext_new_meta_block(handle_t *handle, struct inode *inode,
                        struct ext4_ext_path *path,
                        struct ext4_extent *ex, int *err, unsigned int flags)
{
        ext4_fsblk_t goal, newblock;

        goal = ext4_ext_find_goal(inode, path, le32_to_cpu(ex->ee_block));
        newblock = ext4_new_meta_blocks(handle, inode, goal, flags,
                                        NULL, err);
        return newblock;
}

static inline int ext4_ext_space_block(struct inode *inode, int check)
{
        int size;

        size = (inode->i_sb->s_blocksize - sizeof(struct ext4_extent_header))
                        / sizeof(struct ext4_extent);
#ifdef AGGRESSIVE_TEST
        if (!check && size > 6)
                size = 6;
#endif
        return size;
}

static inline int ext4_ext_space_block_idx(struct inode *inode, int check)
{
        int size;

        size = (inode->i_sb->s_blocksize - sizeof(struct ext4_extent_header))
                        / sizeof(struct ext4_extent_idx);
#ifdef AGGRESSIVE_TEST
        if (!check && size > 5)
                size = 5;
#endif
        return size;
}

static inline int ext4_ext_space_root(struct inode *inode, int check)
{
        int size;

        size = sizeof(EXT4_I(inode)->i_data);
        size -= sizeof(struct ext4_extent_header);
        size /= sizeof(struct ext4_extent);
#ifdef AGGRESSIVE_TEST
        if (!check && size > 3)
                size = 3;
#endif
        return size;
}

static inline int ext4_ext_space_root_idx(struct inode *inode, int check)
{
        int size;

        size = sizeof(EXT4_I(inode)->i_data);
        size -= sizeof(struct ext4_extent_header);
        size /= sizeof(struct ext4_extent_idx);
#ifdef AGGRESSIVE_TEST
        if (!check && size > 4)
                size = 4;
#endif
        return size;
}

static inline struct ext4_ext_path *
ext4_force_split_extent_at(handle_t *handle, struct inode *inode,
                           struct ext4_ext_path *path, ext4_lblk_t lblk,
                           int nofail)
{
        int flags = EXT4_EX_NOCACHE | EXT4_GET_BLOCKS_SPLIT_NOMERGE;

        if (nofail)
                flags |= EXT4_GET_BLOCKS_METADATA_NOFAIL | EXT4_EX_NOFAIL;

        return ext4_split_extent_at(handle, inode, path, lblk, flags);
}

static int
ext4_ext_max_entries(struct inode *inode, int depth)
{
        int max;

        if (depth == ext_depth(inode)) {
                if (depth == 0)
                        max = ext4_ext_space_root(inode, 1);
                else
                        max = ext4_ext_space_root_idx(inode, 1);
        } else {
                if (depth == 0)
                        max = ext4_ext_space_block(inode, 1);
                else
                        max = ext4_ext_space_block_idx(inode, 1);
        }

        return max;
}

static int ext4_valid_extent(struct inode *inode, struct ext4_extent *ext)
{
        ext4_fsblk_t block = ext4_ext_pblock(ext);
        int len = ext4_ext_get_actual_len(ext);
        ext4_lblk_t lblock = le32_to_cpu(ext->ee_block);

        /*
         * We allow neither:
         *  - zero length
         *  - overflow/wrap-around
         */
        if (lblock + len <= lblock)
                return 0;
        return ext4_inode_block_valid(inode, block, len);
}

static int ext4_valid_extent_idx(struct inode *inode,
                                struct ext4_extent_idx *ext_idx)
{
        ext4_fsblk_t block = ext4_idx_pblock(ext_idx);

        return ext4_inode_block_valid(inode, block, 1);
}

static int ext4_valid_extent_entries(struct inode *inode,
                                     struct ext4_extent_header *eh,
                                     ext4_lblk_t lblk, ext4_fsblk_t *pblk,
                                     int depth)
{
        unsigned short entries;
        ext4_lblk_t lblock = 0;
        ext4_lblk_t cur = 0;

        if (eh->eh_entries == 0)
                return 1;

        entries = le16_to_cpu(eh->eh_entries);

        if (depth == 0) {
                /* leaf entries */
                struct ext4_extent *ext = EXT_FIRST_EXTENT(eh);

                /*
                 * The logical block in the first entry should equal to
                 * the number in the index block.
                 */
                if (depth != ext_depth(inode) &&
                    lblk != le32_to_cpu(ext->ee_block))
                        return 0;
                while (entries) {
                        if (!ext4_valid_extent(inode, ext))
                                return 0;

                        /* Check for overlapping extents */
                        lblock = le32_to_cpu(ext->ee_block);
                        if (lblock < cur) {
                                *pblk = ext4_ext_pblock(ext);
                                return 0;
                        }
                        cur = lblock + ext4_ext_get_actual_len(ext);
                        ext++;
                        entries--;
                }
        } else {
                struct ext4_extent_idx *ext_idx = EXT_FIRST_INDEX(eh);

                /*
                 * The logical block in the first entry should equal to
                 * the number in the parent index block.
                 */
                if (depth != ext_depth(inode) &&
                    lblk != le32_to_cpu(ext_idx->ei_block))
                        return 0;
                while (entries) {
                        if (!ext4_valid_extent_idx(inode, ext_idx))
                                return 0;

                        /* Check for overlapping index extents */
                        lblock = le32_to_cpu(ext_idx->ei_block);
                        if (lblock < cur) {
                                *pblk = ext4_idx_pblock(ext_idx);
                                return 0;
                        }
                        ext_idx++;
                        entries--;
                        cur = lblock + 1;
                }
        }
        return 1;
}

static int __ext4_ext_check(const char *function, unsigned int line,
                            struct inode *inode, struct ext4_extent_header *eh,
                            int depth, ext4_fsblk_t pblk, ext4_lblk_t lblk)
{
        const char *error_msg;
        int max = 0, err = -EFSCORRUPTED;

        if (unlikely(eh->eh_magic != EXT4_EXT_MAGIC)) {
                error_msg = "invalid magic";
                goto corrupted;
        }
        if (unlikely(le16_to_cpu(eh->eh_depth) != depth)) {
                error_msg = "unexpected eh_depth";
                goto corrupted;
        }
        if (unlikely(eh->eh_max == 0)) {
                error_msg = "invalid eh_max";
                goto corrupted;
        }
        max = ext4_ext_max_entries(inode, depth);
        if (unlikely(le16_to_cpu(eh->eh_max) > max)) {
                error_msg = "too large eh_max";
                goto corrupted;
        }
        if (unlikely(le16_to_cpu(eh->eh_entries) > le16_to_cpu(eh->eh_max))) {
                error_msg = "invalid eh_entries";
                goto corrupted;
        }
        if (unlikely((eh->eh_entries == 0) && (depth > 0))) {
                error_msg = "eh_entries is 0 but eh_depth is > 0";
                goto corrupted;
        }
        if (!ext4_valid_extent_entries(inode, eh, lblk, &pblk, depth)) {
                error_msg = "invalid extent entries";
                goto corrupted;
        }
        if (unlikely(depth > 32)) {
                error_msg = "too large eh_depth";
                goto corrupted;
        }
        /* Verify checksum on non-root extent tree nodes */
        if (ext_depth(inode) != depth &&
            !ext4_extent_block_csum_verify(inode, eh)) {
                error_msg = "extent tree corrupted";
                err = -EFSBADCRC;
                goto corrupted;
        }
        return 0;

corrupted:
        ext4_error_inode_err(inode, function, line, 0, -err,
                             "pblk %llu bad header/extent: %s - magic %x, "
                             "entries %u, max %u(%u), depth %u(%u)",
                             (unsigned long long) pblk, error_msg,
                             le16_to_cpu(eh->eh_magic),
                             le16_to_cpu(eh->eh_entries),
                             le16_to_cpu(eh->eh_max),
                             max, le16_to_cpu(eh->eh_depth), depth);
        return err;
}

#define ext4_ext_check(inode, eh, depth, pblk)                  \
        __ext4_ext_check(__func__, __LINE__, (inode), (eh), (depth), (pblk), 0)

int ext4_ext_check_inode(struct inode *inode)
{
        return ext4_ext_check(inode, ext_inode_hdr(inode), ext_depth(inode), 0);
}

static void ext4_cache_extents(struct inode *inode,
                               struct ext4_extent_header *eh)
{
        struct ext4_extent *ex = EXT_FIRST_EXTENT(eh);
        ext4_lblk_t prev = 0;
        int i;

        KUNIT_STATIC_STUB_REDIRECT(ext4_cache_extents, inode, eh);

        for (i = le16_to_cpu(eh->eh_entries); i > 0; i--, ex++) {
                unsigned int status = EXTENT_STATUS_WRITTEN;
                ext4_lblk_t lblk = le32_to_cpu(ex->ee_block);
                int len = ext4_ext_get_actual_len(ex);

                if (prev && (prev != lblk))
                        ext4_es_cache_extent(inode, prev, lblk - prev, ~0,
                                             EXTENT_STATUS_HOLE);

                if (ext4_ext_is_unwritten(ex))
                        status = EXTENT_STATUS_UNWRITTEN;
                ext4_es_cache_extent(inode, lblk, len,
                                     ext4_ext_pblock(ex), status);
                prev = lblk + len;
        }
}

static struct buffer_head *
__read_extent_tree_block(const char *function, unsigned int line,
                         struct inode *inode, struct ext4_extent_idx *idx,
                         int depth, int flags)
{
        struct buffer_head              *bh;
        int                             err;
        gfp_t                           gfp_flags = __GFP_MOVABLE | GFP_NOFS;
        ext4_fsblk_t                    pblk;

        if (flags & EXT4_EX_NOFAIL)
                gfp_flags |= __GFP_NOFAIL;

        pblk = ext4_idx_pblock(idx);
        bh = sb_getblk_gfp(inode->i_sb, pblk, gfp_flags);
        if (unlikely(!bh))
                return ERR_PTR(-ENOMEM);

        if (!bh_uptodate_or_lock(bh)) {
                trace_ext4_ext_load_extent(inode, pblk, _RET_IP_);
                err = ext4_read_bh(bh, 0, NULL, false);
                if (err < 0)
                        goto errout;
        }
        if (buffer_verified(bh) && !(flags & EXT4_EX_FORCE_CACHE))
                return bh;
        err = __ext4_ext_check(function, line, inode, ext_block_hdr(bh),
                               depth, pblk, le32_to_cpu(idx->ei_block));
        if (err)
                goto errout;
        set_buffer_verified(bh);
        /*
         * If this is a leaf block, cache all of its entries
         */
        if (!(flags & EXT4_EX_NOCACHE) && depth == 0) {
                struct ext4_extent_header *eh = ext_block_hdr(bh);
                ext4_cache_extents(inode, eh);
        }
        return bh;
errout:
        put_bh(bh);
        return ERR_PTR(err);

}

#define read_extent_tree_block(inode, idx, depth, flags)                \
        __read_extent_tree_block(__func__, __LINE__, (inode), (idx),    \
                                 (depth), (flags))

/*
 * This function is called to cache a file's extent information in the
 * extent status tree
 */
int ext4_ext_precache(struct inode *inode)
{
        struct ext4_inode_info *ei = EXT4_I(inode);
        struct ext4_ext_path *path = NULL;
        struct buffer_head *bh;
        int i = 0, depth, ret = 0;

        if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
                return 0;       /* not an extent-mapped inode */

        ext4_check_map_extents_env(inode);

        down_read(&ei->i_data_sem);
        depth = ext_depth(inode);

        /* Don't cache anything if there are no external extent blocks */
        if (!depth) {
                up_read(&ei->i_data_sem);
                return ret;
        }

        path = kzalloc_objs(struct ext4_ext_path, depth + 1, GFP_NOFS);
        if (path == NULL) {
                up_read(&ei->i_data_sem);
                return -ENOMEM;
        }

        path[0].p_hdr = ext_inode_hdr(inode);
        ret = ext4_ext_check(inode, path[0].p_hdr, depth, 0);
        if (ret)
                goto out;
        path[0].p_idx = EXT_FIRST_INDEX(path[0].p_hdr);
        while (i >= 0) {
                /*
                 * If this is a leaf block or we've reached the end of
                 * the index block, go up
                 */
                if ((i == depth) ||
                    path[i].p_idx > EXT_LAST_INDEX(path[i].p_hdr)) {
                        ext4_ext_path_brelse(path + i);
                        i--;
                        continue;
                }
                bh = read_extent_tree_block(inode, path[i].p_idx++,
                                            depth - i - 1,
                                            EXT4_EX_FORCE_CACHE);
                if (IS_ERR(bh)) {
                        ret = PTR_ERR(bh);
                        break;
                }
                i++;
                path[i].p_bh = bh;
                path[i].p_hdr = ext_block_hdr(bh);
                path[i].p_idx = EXT_FIRST_INDEX(path[i].p_hdr);
        }
        ext4_set_inode_state(inode, EXT4_STATE_EXT_PRECACHED);
out:
        up_read(&ei->i_data_sem);
        ext4_free_ext_path(path);
        return ret;
}

#ifdef EXT_DEBUG
static void ext4_ext_show_path(struct inode *inode, struct ext4_ext_path *path)
{
        int k, l = path->p_depth;

        ext_debug(inode, "path:");
        for (k = 0; k <= l; k++, path++) {
                if (path->p_idx) {
                        ext_debug(inode, "  %d->%llu",
                                  le32_to_cpu(path->p_idx->ei_block),
                                  ext4_idx_pblock(path->p_idx));
                } else if (path->p_ext) {
                        ext_debug(inode, "  %d:[%d]%d:%llu ",
                                  le32_to_cpu(path->p_ext->ee_block),
                                  ext4_ext_is_unwritten(path->p_ext),
                                  ext4_ext_get_actual_len(path->p_ext),
                                  ext4_ext_pblock(path->p_ext));
                } else
                        ext_debug(inode, "  []");
        }
        ext_debug(inode, "\n");
}

static void ext4_ext_show_leaf(struct inode *inode, struct ext4_ext_path *path)
{
        int depth = ext_depth(inode);
        struct ext4_extent_header *eh;
        struct ext4_extent *ex;
        int i;

        if (IS_ERR_OR_NULL(path))
                return;

        eh = path[depth].p_hdr;
        ex = EXT_FIRST_EXTENT(eh);

        ext_debug(inode, "Displaying leaf extents\n");

        for (i = 0; i < le16_to_cpu(eh->eh_entries); i++, ex++) {
                ext_debug(inode, "%d:[%d]%d:%llu ", le32_to_cpu(ex->ee_block),
                          ext4_ext_is_unwritten(ex),
                          ext4_ext_get_actual_len(ex), ext4_ext_pblock(ex));
        }
        ext_debug(inode, "\n");
}

static void ext4_ext_show_move(struct inode *inode, struct ext4_ext_path *path,
                        ext4_fsblk_t newblock, int level)
{
        int depth = ext_depth(inode);
        struct ext4_extent *ex;

        if (depth != level) {
                struct ext4_extent_idx *idx;
                idx = path[level].p_idx;
                while (idx <= EXT_MAX_INDEX(path[level].p_hdr)) {
                        ext_debug(inode, "%d: move %d:%llu in new index %llu\n",
                                  level, le32_to_cpu(idx->ei_block),
                                  ext4_idx_pblock(idx), newblock);
                        idx++;
                }

                return;
        }

        ex = path[depth].p_ext;
        while (ex <= EXT_MAX_EXTENT(path[depth].p_hdr)) {
                ext_debug(inode, "move %d:%llu:[%d]%d in new leaf %llu\n",
                                le32_to_cpu(ex->ee_block),
                                ext4_ext_pblock(ex),
                                ext4_ext_is_unwritten(ex),
                                ext4_ext_get_actual_len(ex),
                                newblock);
                ex++;
        }
}

#else
#define ext4_ext_show_path(inode, path)
#define ext4_ext_show_leaf(inode, path)
#define ext4_ext_show_move(inode, path, newblock, level)
#endif

/*
 * ext4_ext_binsearch_idx:
 * binary search for the closest index of the given block
 * the header must be checked before calling this
 */
static void
ext4_ext_binsearch_idx(struct inode *inode,
                        struct ext4_ext_path *path, ext4_lblk_t block)
{
        struct ext4_extent_header *eh = path->p_hdr;
        struct ext4_extent_idx *r, *l, *m;


        ext_debug(inode, "binsearch for %u(idx):  ", block);

        l = EXT_FIRST_INDEX(eh) + 1;
        r = EXT_LAST_INDEX(eh);
        while (l <= r) {
                m = l + (r - l) / 2;
                ext_debug(inode, "%p(%u):%p(%u):%p(%u) ", l,
                          le32_to_cpu(l->ei_block), m, le32_to_cpu(m->ei_block),
                          r, le32_to_cpu(r->ei_block));

                if (block < le32_to_cpu(m->ei_block))
                        r = m - 1;
                else
                        l = m + 1;
        }

        path->p_idx = l - 1;
        ext_debug(inode, "  -> %u->%lld ", le32_to_cpu(path->p_idx->ei_block),
                  ext4_idx_pblock(path->p_idx));

#ifdef CHECK_BINSEARCH
        {
                struct ext4_extent_idx *chix, *ix;
                int k;

                chix = ix = EXT_FIRST_INDEX(eh);
                for (k = 0; k < le16_to_cpu(eh->eh_entries); k++, ix++) {
                        if (k != 0 && le32_to_cpu(ix->ei_block) <=
                            le32_to_cpu(ix[-1].ei_block)) {
                                printk(KERN_DEBUG "k=%d, ix=0x%p, "
                                       "first=0x%p\n", k,
                                       ix, EXT_FIRST_INDEX(eh));
                                printk(KERN_DEBUG "%u <= %u\n",
                                       le32_to_cpu(ix->ei_block),
                                       le32_to_cpu(ix[-1].ei_block));
                        }
                        BUG_ON(k && le32_to_cpu(ix->ei_block)
                                           <= le32_to_cpu(ix[-1].ei_block));
                        if (block < le32_to_cpu(ix->ei_block))
                                break;
                        chix = ix;
                }
                BUG_ON(chix != path->p_idx);
        }
#endif

}

/*
 * ext4_ext_binsearch:
 * binary search for closest extent of the given block
 * the header must be checked before calling this
 */
static void
ext4_ext_binsearch(struct inode *inode,
                struct ext4_ext_path *path, ext4_lblk_t block)
{
        struct ext4_extent_header *eh = path->p_hdr;
        struct ext4_extent *r, *l, *m;

        if (eh->eh_entries == 0) {
                /*
                 * this leaf is empty:
                 * we get such a leaf in split/add case
                 */
                return;
        }

        ext_debug(inode, "binsearch for %u:  ", block);

        l = EXT_FIRST_EXTENT(eh) + 1;
        r = EXT_LAST_EXTENT(eh);

        while (l <= r) {
                m = l + (r - l) / 2;
                ext_debug(inode, "%p(%u):%p(%u):%p(%u) ", l,
                          le32_to_cpu(l->ee_block), m, le32_to_cpu(m->ee_block),
                          r, le32_to_cpu(r->ee_block));

                if (block < le32_to_cpu(m->ee_block))
                        r = m - 1;
                else
                        l = m + 1;
        }

        path->p_ext = l - 1;
        ext_debug(inode, "  -> %d:%llu:[%d]%d ",
                        le32_to_cpu(path->p_ext->ee_block),
                        ext4_ext_pblock(path->p_ext),
                        ext4_ext_is_unwritten(path->p_ext),
                        ext4_ext_get_actual_len(path->p_ext));

#ifdef CHECK_BINSEARCH
        {
                struct ext4_extent *chex, *ex;
                int k;

                chex = ex = EXT_FIRST_EXTENT(eh);
                for (k = 0; k < le16_to_cpu(eh->eh_entries); k++, ex++) {
                        BUG_ON(k && le32_to_cpu(ex->ee_block)
                                          <= le32_to_cpu(ex[-1].ee_block));
                        if (block < le32_to_cpu(ex->ee_block))
                                break;
                        chex = ex;
                }
                BUG_ON(chex != path->p_ext);
        }
#endif

}

void ext4_ext_tree_init(handle_t *handle, struct inode *inode)
{
        struct ext4_extent_header *eh;

        eh = ext_inode_hdr(inode);
        eh->eh_depth = 0;
        eh->eh_entries = 0;
        eh->eh_magic = EXT4_EXT_MAGIC;
        eh->eh_max = cpu_to_le16(ext4_ext_space_root(inode, 0));
        eh->eh_generation = 0;
        ext4_mark_inode_dirty(handle, inode);
}

struct ext4_ext_path *
ext4_find_extent(struct inode *inode, ext4_lblk_t block,
                 struct ext4_ext_path *path, int flags)
{
        struct ext4_extent_header *eh;
        struct buffer_head *bh;
        short int depth, i, ppos = 0;
        int ret;
        gfp_t gfp_flags = GFP_NOFS;

        KUNIT_STATIC_STUB_REDIRECT(ext4_find_extent, inode, block, path, flags);

        if (flags & EXT4_EX_NOFAIL)
                gfp_flags |= __GFP_NOFAIL;

        eh = ext_inode_hdr(inode);
        depth = ext_depth(inode);
        if (depth < 0 || depth > EXT4_MAX_EXTENT_DEPTH) {
                EXT4_ERROR_INODE(inode, "inode has invalid extent depth: %d",
                                 depth);
                ret = -EFSCORRUPTED;
                goto err;
        }

        if (path) {
                ext4_ext_drop_refs(path);
                if (depth > path[0].p_maxdepth) {
                        kfree(path);
                        path = NULL;
                }
        }
        if (!path) {
                /* account possible depth increase */
                path = kzalloc_objs(struct ext4_ext_path, depth + 2, gfp_flags);
                if (unlikely(!path))
                        return ERR_PTR(-ENOMEM);
                path[0].p_maxdepth = depth + 1;
        }
        path[0].p_hdr = eh;
        path[0].p_bh = NULL;

        i = depth;
        if (!(flags & EXT4_EX_NOCACHE) && depth == 0)
                ext4_cache_extents(inode, eh);
        /* walk through the tree */
        while (i) {
                ext_debug(inode, "depth %d: num %d, max %d\n",
                          ppos, le16_to_cpu(eh->eh_entries), le16_to_cpu(eh->eh_max));

                ext4_ext_binsearch_idx(inode, path + ppos, block);
                path[ppos].p_block = ext4_idx_pblock(path[ppos].p_idx);
                path[ppos].p_depth = i;
                path[ppos].p_ext = NULL;

                bh = read_extent_tree_block(inode, path[ppos].p_idx, --i, flags);
                if (IS_ERR(bh)) {
                        ret = PTR_ERR(bh);
                        goto err;
                }

                eh = ext_block_hdr(bh);
                ppos++;
                path[ppos].p_bh = bh;
                path[ppos].p_hdr = eh;
        }

        path[ppos].p_depth = i;
        path[ppos].p_ext = NULL;
        path[ppos].p_idx = NULL;

        /* find extent */
        ext4_ext_binsearch(inode, path + ppos, block);
        /* if not an empty leaf */
        if (path[ppos].p_ext)
                path[ppos].p_block = ext4_ext_pblock(path[ppos].p_ext);

        ext4_ext_show_path(inode, path);

        return path;

err:
        ext4_free_ext_path(path);
        return ERR_PTR(ret);
}

/*
 * ext4_ext_insert_index:
 * insert new index [@logical;@ptr] into the block at @curp;
 * check where to insert: before @curp or after @curp
 */
static int ext4_ext_insert_index(handle_t *handle, struct inode *inode,
                                 struct ext4_ext_path *curp,
                                 int logical, ext4_fsblk_t ptr)
{
        struct ext4_extent_idx *ix;
        int len, err;

        err = ext4_ext_get_access(handle, inode, curp);
        if (err)
                return err;

        if (unlikely(logical == le32_to_cpu(curp->p_idx->ei_block))) {
                EXT4_ERROR_INODE(inode,
                                 "logical %d == ei_block %d!",
                                 logical, le32_to_cpu(curp->p_idx->ei_block));
                return -EFSCORRUPTED;
        }

        if (unlikely(le16_to_cpu(curp->p_hdr->eh_entries)
                             >= le16_to_cpu(curp->p_hdr->eh_max))) {
                EXT4_ERROR_INODE(inode,
                                 "eh_entries %d >= eh_max %d!",
                                 le16_to_cpu(curp->p_hdr->eh_entries),
                                 le16_to_cpu(curp->p_hdr->eh_max));
                return -EFSCORRUPTED;
        }

        if (logical > le32_to_cpu(curp->p_idx->ei_block)) {
                /* insert after */
                ext_debug(inode, "insert new index %d after: %llu\n",
                          logical, ptr);
                ix = curp->p_idx + 1;
        } else {
                /* insert before */
                ext_debug(inode, "insert new index %d before: %llu\n",
                          logical, ptr);
                ix = curp->p_idx;
        }

        if (unlikely(ix > EXT_MAX_INDEX(curp->p_hdr))) {
                EXT4_ERROR_INODE(inode, "ix > EXT_MAX_INDEX!");
                return -EFSCORRUPTED;
        }

        len = EXT_LAST_INDEX(curp->p_hdr) - ix + 1;
        BUG_ON(len < 0);
        if (len > 0) {
                ext_debug(inode, "insert new index %d: "
                                "move %d indices from 0x%p to 0x%p\n",
                                logical, len, ix, ix + 1);
                memmove(ix + 1, ix, len * sizeof(struct ext4_extent_idx));
        }

        ix->ei_block = cpu_to_le32(logical);
        ext4_idx_store_pblock(ix, ptr);
        le16_add_cpu(&curp->p_hdr->eh_entries, 1);

        if (unlikely(ix > EXT_LAST_INDEX(curp->p_hdr))) {
                EXT4_ERROR_INODE(inode, "ix > EXT_LAST_INDEX!");
                return -EFSCORRUPTED;
        }

        err = ext4_ext_dirty(handle, inode, curp);
        ext4_std_error(inode->i_sb, err);

        return err;
}

/*
 * ext4_ext_split:
 * inserts new subtree into the path, using free index entry
 * at depth @at:
 * - allocates all needed blocks (new leaf and all intermediate index blocks)
 * - makes decision where to split
 * - moves remaining extents and index entries (right to the split point)
 *   into the newly allocated blocks
 * - initializes subtree
 */
static int ext4_ext_split(handle_t *handle, struct inode *inode,
                          unsigned int flags,
                          struct ext4_ext_path *path,
                          struct ext4_extent *newext, int at)
{
        struct buffer_head *bh = NULL;
        int depth = ext_depth(inode);
        struct ext4_extent_header *neh;
        struct ext4_extent_idx *fidx;
        int i = at, k, m, a;
        ext4_fsblk_t newblock, oldblock;
        __le32 border;
        ext4_fsblk_t *ablocks = NULL; /* array of allocated blocks */
        gfp_t gfp_flags = GFP_NOFS;
        int err = 0;
        size_t ext_size = 0;

        if (flags & EXT4_EX_NOFAIL)
                gfp_flags |= __GFP_NOFAIL;

        /* make decision: where to split? */
        /* FIXME: now decision is simplest: at current extent */

        /* if current leaf will be split, then we should use
         * border from split point */
        if (unlikely(path[depth].p_ext > EXT_MAX_EXTENT(path[depth].p_hdr))) {
                EXT4_ERROR_INODE(inode, "p_ext > EXT_MAX_EXTENT!");
                return -EFSCORRUPTED;
        }
        if (path[depth].p_ext != EXT_MAX_EXTENT(path[depth].p_hdr)) {
                border = path[depth].p_ext[1].ee_block;
                ext_debug(inode, "leaf will be split."
                                " next leaf starts at %d\n",
                                  le32_to_cpu(border));
        } else {
                border = newext->ee_block;
                ext_debug(inode, "leaf will be added."
                                " next leaf starts at %d\n",
                                le32_to_cpu(border));
        }

        /*
         * If error occurs, then we break processing
         * and mark filesystem read-only. index won't
         * be inserted and tree will be in consistent
         * state. Next mount will repair buffers too.
         */

        /*
         * Get array to track all allocated blocks.
         * We need this to handle errors and free blocks
         * upon them.
         */
        ablocks = kzalloc_objs(ext4_fsblk_t, depth, gfp_flags);
        if (!ablocks)
                return -ENOMEM;

        /* allocate all needed blocks */
        ext_debug(inode, "allocate %d blocks for indexes/leaf\n", depth - at);
        for (a = 0; a < depth - at; a++) {
                newblock = ext4_ext_new_meta_block(handle, inode, path,
                                                   newext, &err, flags);
                if (newblock == 0)
                        goto cleanup;
                ablocks[a] = newblock;
        }

        /* initialize new leaf */
        newblock = ablocks[--a];
        if (unlikely(newblock == 0)) {
                EXT4_ERROR_INODE(inode, "newblock == 0!");
                err = -EFSCORRUPTED;
                goto cleanup;
        }
        bh = sb_getblk_gfp(inode->i_sb, newblock, __GFP_MOVABLE | GFP_NOFS);
        if (unlikely(!bh)) {
                err = -ENOMEM;
                goto cleanup;
        }
        lock_buffer(bh);

        err = ext4_journal_get_create_access(handle, inode->i_sb, bh,
                                             EXT4_JTR_NONE);
        if (err)
                goto cleanup;

        neh = ext_block_hdr(bh);
        neh->eh_entries = 0;
        neh->eh_max = cpu_to_le16(ext4_ext_space_block(inode, 0));
        neh->eh_magic = EXT4_EXT_MAGIC;
        neh->eh_depth = 0;
        neh->eh_generation = 0;

        /* move remainder of path[depth] to the new leaf */
        if (unlikely(path[depth].p_hdr->eh_entries !=
                     path[depth].p_hdr->eh_max)) {
                EXT4_ERROR_INODE(inode, "eh_entries %d != eh_max %d!",
                                 path[depth].p_hdr->eh_entries,
                                 path[depth].p_hdr->eh_max);
                err = -EFSCORRUPTED;
                goto cleanup;
        }
        /* start copy from next extent */
        m = EXT_MAX_EXTENT(path[depth].p_hdr) - path[depth].p_ext++;
        ext4_ext_show_move(inode, path, newblock, depth);
        if (m) {
                struct ext4_extent *ex;
                ex = EXT_FIRST_EXTENT(neh);
                memmove(ex, path[depth].p_ext, sizeof(struct ext4_extent) * m);
                le16_add_cpu(&neh->eh_entries, m);
        }

        /* zero out unused area in the extent block */
        ext_size = sizeof(struct ext4_extent_header) +
                sizeof(struct ext4_extent) * le16_to_cpu(neh->eh_entries);
        memset(bh->b_data + ext_size, 0, inode->i_sb->s_blocksize - ext_size);
        ext4_extent_block_csum_set(inode, neh);
        set_buffer_uptodate(bh);
        unlock_buffer(bh);

        err = ext4_handle_dirty_metadata(handle, inode, bh);
        if (err)
                goto cleanup;
        brelse(bh);
        bh = NULL;

        /* correct old leaf */
        if (m) {
                err = ext4_ext_get_access(handle, inode, path + depth);
                if (err)
                        goto cleanup;
                le16_add_cpu(&path[depth].p_hdr->eh_entries, -m);
                err = ext4_ext_dirty(handle, inode, path + depth);
                if (err)
                        goto cleanup;

        }

        /* create intermediate indexes */
        k = depth - at - 1;
        if (unlikely(k < 0)) {
                EXT4_ERROR_INODE(inode, "k %d < 0!", k);
                err = -EFSCORRUPTED;
                goto cleanup;
        }
        if (k)
                ext_debug(inode, "create %d intermediate indices\n", k);
        /* insert new index into current index block */
        /* current depth stored in i var */
        i = depth - 1;
        while (k--) {
                oldblock = newblock;
                newblock = ablocks[--a];
                bh = sb_getblk(inode->i_sb, newblock);
                if (unlikely(!bh)) {
                        err = -ENOMEM;
                        goto cleanup;
                }
                lock_buffer(bh);

                err = ext4_journal_get_create_access(handle, inode->i_sb, bh,
                                                     EXT4_JTR_NONE);
                if (err)
                        goto cleanup;

                neh = ext_block_hdr(bh);
                neh->eh_entries = cpu_to_le16(1);
                neh->eh_magic = EXT4_EXT_MAGIC;
                neh->eh_max = cpu_to_le16(ext4_ext_space_block_idx(inode, 0));
                neh->eh_depth = cpu_to_le16(depth - i);
                neh->eh_generation = 0;
                fidx = EXT_FIRST_INDEX(neh);
                fidx->ei_block = border;
                ext4_idx_store_pblock(fidx, oldblock);

                ext_debug(inode, "int.index at %d (block %llu): %u -> %llu\n",
                                i, newblock, le32_to_cpu(border), oldblock);

                /* move remainder of path[i] to the new index block */
                if (unlikely(EXT_MAX_INDEX(path[i].p_hdr) !=
                                        EXT_LAST_INDEX(path[i].p_hdr))) {
                        EXT4_ERROR_INODE(inode,
                                         "EXT_MAX_INDEX != EXT_LAST_INDEX ee_block %d!",
                                         le32_to_cpu(path[i].p_ext->ee_block));
                        err = -EFSCORRUPTED;
                        goto cleanup;
                }
                /* start copy indexes */
                m = EXT_MAX_INDEX(path[i].p_hdr) - path[i].p_idx++;
                ext_debug(inode, "cur 0x%p, last 0x%p\n", path[i].p_idx,
                                EXT_MAX_INDEX(path[i].p_hdr));
                ext4_ext_show_move(inode, path, newblock, i);
                if (m) {
                        memmove(++fidx, path[i].p_idx,
                                sizeof(struct ext4_extent_idx) * m);
                        le16_add_cpu(&neh->eh_entries, m);
                }
                /* zero out unused area in the extent block */
                ext_size = sizeof(struct ext4_extent_header) +
                   (sizeof(struct ext4_extent) * le16_to_cpu(neh->eh_entries));
                memset(bh->b_data + ext_size, 0,
                        inode->i_sb->s_blocksize - ext_size);
                ext4_extent_block_csum_set(inode, neh);
                set_buffer_uptodate(bh);
                unlock_buffer(bh);

                err = ext4_handle_dirty_metadata(handle, inode, bh);
                if (err)
                        goto cleanup;
                brelse(bh);
                bh = NULL;

                /* correct old index */
                if (m) {
                        err = ext4_ext_get_access(handle, inode, path + i);
                        if (err)
                                goto cleanup;
                        le16_add_cpu(&path[i].p_hdr->eh_entries, -m);
                        err = ext4_ext_dirty(handle, inode, path + i);
                        if (err)
                                goto cleanup;
                }

                i--;
        }

        /* insert new index */
        err = ext4_ext_insert_index(handle, inode, path + at,
                                    le32_to_cpu(border), newblock);

cleanup:
        if (bh) {
                if (buffer_locked(bh))
                        unlock_buffer(bh);
                brelse(bh);
        }

        if (err) {
                /* free all allocated blocks in error case */
                for (i = 0; i < depth; i++) {
                        if (!ablocks[i])
                                continue;
                        ext4_free_blocks(handle, inode, NULL, ablocks[i], 1,
                                         EXT4_FREE_BLOCKS_METADATA);
                }
        }
        kfree(ablocks);

        return err;
}

/*
 * ext4_ext_grow_indepth:
 * implements tree growing procedure:
 * - allocates new block
 * - moves top-level data (index block or leaf) into the new block
 * - initializes new top-level, creating index that points to the
 *   just created block
 */
static int ext4_ext_grow_indepth(handle_t *handle, struct inode *inode,
                                 unsigned int flags)
{
        struct ext4_extent_header *neh;
        struct buffer_head *bh;
        ext4_fsblk_t newblock, goal = 0;
        struct ext4_super_block *es = EXT4_SB(inode->i_sb)->s_es;
        int err = 0;
        size_t ext_size = 0;

        /* Try to prepend new index to old one */
        if (ext_depth(inode))
                goal = ext4_idx_pblock(EXT_FIRST_INDEX(ext_inode_hdr(inode)));
        if (goal > le32_to_cpu(es->s_first_data_block)) {
                flags |= EXT4_MB_HINT_TRY_GOAL;
                goal--;
        } else
                goal = ext4_inode_to_goal_block(inode);
        newblock = ext4_new_meta_blocks(handle, inode, goal, flags,
                                        NULL, &err);
        if (newblock == 0)
                return err;

        bh = sb_getblk_gfp(inode->i_sb, newblock, __GFP_MOVABLE | GFP_NOFS);
        if (unlikely(!bh))
                return -ENOMEM;
        lock_buffer(bh);

        err = ext4_journal_get_create_access(handle, inode->i_sb, bh,
                                             EXT4_JTR_NONE);
        if (err) {
                unlock_buffer(bh);
                goto out;
        }

        ext_size = sizeof(EXT4_I(inode)->i_data);
        /* move top-level index/leaf into new block */
        memmove(bh->b_data, EXT4_I(inode)->i_data, ext_size);
        /* zero out unused area in the extent block */
        memset(bh->b_data + ext_size, 0, inode->i_sb->s_blocksize - ext_size);

        /* set size of new block */
        neh = ext_block_hdr(bh);
        /* old root could have indexes or leaves
         * so calculate e_max right way */
        if (ext_depth(inode))
                neh->eh_max = cpu_to_le16(ext4_ext_space_block_idx(inode, 0));
        else
                neh->eh_max = cpu_to_le16(ext4_ext_space_block(inode, 0));
        neh->eh_magic = EXT4_EXT_MAGIC;
        ext4_extent_block_csum_set(inode, neh);
        set_buffer_uptodate(bh);
        set_buffer_verified(bh);
        unlock_buffer(bh);

        err = ext4_handle_dirty_metadata(handle, inode, bh);
        if (err)
                goto out;

        /* Update top-level index: num,max,pointer */
        neh = ext_inode_hdr(inode);
        neh->eh_entries = cpu_to_le16(1);
        ext4_idx_store_pblock(EXT_FIRST_INDEX(neh), newblock);
        if (neh->eh_depth == 0) {
                /* Root extent block becomes index block */
                neh->eh_max = cpu_to_le16(ext4_ext_space_root_idx(inode, 0));
                EXT_FIRST_INDEX(neh)->ei_block =
                        EXT_FIRST_EXTENT(neh)->ee_block;
        }
        ext_debug(inode, "new root: num %d(%d), lblock %d, ptr %llu\n",
                  le16_to_cpu(neh->eh_entries), le16_to_cpu(neh->eh_max),
                  le32_to_cpu(EXT_FIRST_INDEX(neh)->ei_block),
                  ext4_idx_pblock(EXT_FIRST_INDEX(neh)));

        le16_add_cpu(&neh->eh_depth, 1);
        err = ext4_mark_inode_dirty(handle, inode);
out:
        brelse(bh);

        return err;
}

/*
 * ext4_ext_create_new_leaf:
 * finds empty index and adds new leaf.
 * if no free index is found, then it requests in-depth growing.
 */
static struct ext4_ext_path *
ext4_ext_create_new_leaf(handle_t *handle, struct inode *inode,
                         unsigned int mb_flags, unsigned int gb_flags,
                         struct ext4_ext_path *path,
                         struct ext4_extent *newext)
{
        struct ext4_ext_path *curp;
        int depth, i, err = 0;
        ext4_lblk_t ee_block = le32_to_cpu(newext->ee_block);

repeat:
        i = depth = ext_depth(inode);

        /* walk up to the tree and look for free index entry */
        curp = path + depth;
        while (i > 0 && !EXT_HAS_FREE_INDEX(curp)) {
                i--;
                curp--;
        }

        /* we use already allocated block for index block,
         * so subsequent data blocks should be contiguous */
        if (EXT_HAS_FREE_INDEX(curp)) {
                /* if we found index with free entry, then use that
                 * entry: create all needed subtree and add new leaf */
                err = ext4_ext_split(handle, inode, mb_flags, path, newext, i);
                if (err)
                        goto errout;

                /* refill path */
                path = ext4_find_extent(inode, ee_block, path, gb_flags);
                return path;
        }

        /* tree is full, time to grow in depth */
        err = ext4_ext_grow_indepth(handle, inode, mb_flags);
        if (err)
                goto errout;

        /* refill path */
        path = ext4_find_extent(inode, ee_block, path, gb_flags);
        if (IS_ERR(path))
                return path;

        /*
         * only first (depth 0 -> 1) produces free space;
         * in all other cases we have to split the grown tree
         */
        depth = ext_depth(inode);
        if (path[depth].p_hdr->eh_entries == path[depth].p_hdr->eh_max) {
                /* now we need to split */
                goto repeat;
        }

        return path;

errout:
        ext4_free_ext_path(path);
        return ERR_PTR(err);
}

/*
 * search the closest allocated block to the left for *logical
 * and returns it at @logical + it's physical address at @phys
 * if *logical is the smallest allocated block, the function
 * returns 0 at @phys
 * return value contains 0 (success) or error code
 */
static int ext4_ext_search_left(struct inode *inode,
                                struct ext4_ext_path *path,
                                ext4_lblk_t *logical, ext4_fsblk_t *phys)
{
        struct ext4_extent_idx *ix;
        struct ext4_extent *ex;
        int depth, ee_len;

        if (unlikely(path == NULL)) {
                EXT4_ERROR_INODE(inode, "path == NULL *logical %d!", *logical);
                return -EFSCORRUPTED;
        }
        depth = path->p_depth;
        *phys = 0;

        if (depth == 0 && path->p_ext == NULL)
                return 0;

        /* usually extent in the path covers blocks smaller
         * then *logical, but it can be that extent is the
         * first one in the file */

        ex = path[depth].p_ext;
        ee_len = ext4_ext_get_actual_len(ex);
        if (*logical < le32_to_cpu(ex->ee_block)) {
                if (unlikely(EXT_FIRST_EXTENT(path[depth].p_hdr) != ex)) {
                        EXT4_ERROR_INODE(inode,
                                         "EXT_FIRST_EXTENT != ex *logical %d ee_block %d!",
                                         *logical, le32_to_cpu(ex->ee_block));
                        return -EFSCORRUPTED;
                }
                while (--depth >= 0) {
                        ix = path[depth].p_idx;
                        if (unlikely(ix != EXT_FIRST_INDEX(path[depth].p_hdr))) {
                                EXT4_ERROR_INODE(inode,
                                  "ix (%d) != EXT_FIRST_INDEX (%d) (depth %d)!",
                                  ix != NULL ? le32_to_cpu(ix->ei_block) : 0,
                                  le32_to_cpu(EXT_FIRST_INDEX(path[depth].p_hdr)->ei_block),
                                  depth);
                                return -EFSCORRUPTED;
                        }
                }
                return 0;
        }

        if (unlikely(*logical < (le32_to_cpu(ex->ee_block) + ee_len))) {
                EXT4_ERROR_INODE(inode,
                                 "logical %d < ee_block %d + ee_len %d!",
                                 *logical, le32_to_cpu(ex->ee_block), ee_len);
                return -EFSCORRUPTED;
        }

        *logical = le32_to_cpu(ex->ee_block) + ee_len - 1;
        *phys = ext4_ext_pblock(ex) + ee_len - 1;
        return 0;
}

/*
 * Search the closest allocated block to the right for *logical
 * and returns it at @logical + it's physical address at @phys.
 * If not exists, return 0 and @phys is set to 0. We will return
 * 1 which means we found an allocated block and ret_ex is valid.
 * Or return a (< 0) error code.
 */
static int ext4_ext_search_right(struct inode *inode,
                                 struct ext4_ext_path *path,
                                 ext4_lblk_t *logical, ext4_fsblk_t *phys,
                                 struct ext4_extent *ret_ex, int flags)
{
        struct buffer_head *bh = NULL;
        struct ext4_extent_header *eh;
        struct ext4_extent_idx *ix;
        struct ext4_extent *ex;
        int depth;      /* Note, NOT eh_depth; depth from top of tree */
        int ee_len;

        if (unlikely(path == NULL)) {
                EXT4_ERROR_INODE(inode, "path == NULL *logical %d!", *logical);
                return -EFSCORRUPTED;
        }
        depth = path->p_depth;
        *phys = 0;

        if (depth == 0 && path->p_ext == NULL)
                return 0;

        /* usually extent in the path covers blocks smaller
         * then *logical, but it can be that extent is the
         * first one in the file */

        ex = path[depth].p_ext;
        ee_len = ext4_ext_get_actual_len(ex);
        if (*logical < le32_to_cpu(ex->ee_block)) {
                if (unlikely(EXT_FIRST_EXTENT(path[depth].p_hdr) != ex)) {
                        EXT4_ERROR_INODE(inode,
                                         "first_extent(path[%d].p_hdr) != ex",
                                         depth);
                        return -EFSCORRUPTED;
                }
                while (--depth >= 0) {
                        ix = path[depth].p_idx;
                        if (unlikely(ix != EXT_FIRST_INDEX(path[depth].p_hdr))) {
                                EXT4_ERROR_INODE(inode,
                                                 "ix != EXT_FIRST_INDEX *logical %d!",
                                                 *logical);
                                return -EFSCORRUPTED;
                        }
                }
                goto found_extent;
        }

        if (unlikely(*logical < (le32_to_cpu(ex->ee_block) + ee_len))) {
                EXT4_ERROR_INODE(inode,
                                 "logical %d < ee_block %d + ee_len %d!",
                                 *logical, le32_to_cpu(ex->ee_block), ee_len);
                return -EFSCORRUPTED;
        }

        if (ex != EXT_LAST_EXTENT(path[depth].p_hdr)) {
                /* next allocated block in this leaf */
                ex++;
                goto found_extent;
        }

        /* go up and search for index to the right */
        while (--depth >= 0) {
                ix = path[depth].p_idx;
                if (ix != EXT_LAST_INDEX(path[depth].p_hdr))
                        goto got_index;
        }

        /* we've gone up to the root and found no index to the right */
        return 0;

got_index:
        /* we've found index to the right, let's
         * follow it and find the closest allocated
         * block to the right */
        ix++;
        while (++depth < path->p_depth) {
                /* subtract from p_depth to get proper eh_depth */
                bh = read_extent_tree_block(inode, ix, path->p_depth - depth,
                                            flags);
                if (IS_ERR(bh))
                        return PTR_ERR(bh);
                eh = ext_block_hdr(bh);
                ix = EXT_FIRST_INDEX(eh);
                put_bh(bh);
        }

        bh = read_extent_tree_block(inode, ix, path->p_depth - depth, flags);
        if (IS_ERR(bh))
                return PTR_ERR(bh);
        eh = ext_block_hdr(bh);
        ex = EXT_FIRST_EXTENT(eh);
found_extent:
        *logical = le32_to_cpu(ex->ee_block);
        *phys = ext4_ext_pblock(ex);
        if (ret_ex)
                *ret_ex = *ex;
        if (bh)
                put_bh(bh);
        return 1;
}

/*
 * ext4_ext_next_allocated_block:
 * returns allocated block in subsequent extent or EXT_MAX_BLOCKS.
 * NOTE: it considers block number from index entry as
 * allocated block. Thus, index entries have to be consistent
 * with leaves.
 */
ext4_lblk_t
ext4_ext_next_allocated_block(struct ext4_ext_path *path)
{
        int depth;

        BUG_ON(path == NULL);
        depth = path->p_depth;

        if (depth == 0 && path->p_ext == NULL)
                return EXT_MAX_BLOCKS;

        while (depth >= 0) {
                struct ext4_ext_path *p = &path[depth];

                if (depth == path->p_depth) {
                        /* leaf */
                        if (p->p_ext && p->p_ext != EXT_LAST_EXTENT(p->p_hdr))
                                return le32_to_cpu(p->p_ext[1].ee_block);
                } else {
                        /* index */
                        if (p->p_idx != EXT_LAST_INDEX(p->p_hdr))
                                return le32_to_cpu(p->p_idx[1].ei_block);
                }
                depth--;
        }

        return EXT_MAX_BLOCKS;
}

/*
 * ext4_ext_next_leaf_block:
 * returns first allocated block from next leaf or EXT_MAX_BLOCKS
 */
static ext4_lblk_t ext4_ext_next_leaf_block(struct ext4_ext_path *path)
{
        int depth;

        BUG_ON(path == NULL);
        depth = path->p_depth;

        /* zero-tree has no leaf blocks at all */
        if (depth == 0)
                return EXT_MAX_BLOCKS;

        /* go to index block */
        depth--;

        while (depth >= 0) {
                if (path[depth].p_idx !=
                                EXT_LAST_INDEX(path[depth].p_hdr))
                        return (ext4_lblk_t)
                                le32_to_cpu(path[depth].p_idx[1].ei_block);
                depth--;
        }

        return EXT_MAX_BLOCKS;
}

/*
 * ext4_ext_correct_indexes:
 * if leaf gets modified and modified extent is first in the leaf,
 * then we have to correct all indexes above.
 * TODO: do we need to correct tree in all cases?
 */
static int ext4_ext_correct_indexes(handle_t *handle, struct inode *inode,
                                struct ext4_ext_path *path)
{
        struct ext4_extent_header *eh;
        int depth = ext_depth(inode);
        struct ext4_extent *ex;
        __le32 border;
        int k, err = 0;

        eh = path[depth].p_hdr;
        ex = path[depth].p_ext;

        if (unlikely(ex == NULL || eh == NULL)) {
                EXT4_ERROR_INODE(inode,
                                 "ex %p == NULL or eh %p == NULL", ex, eh);
                return -EFSCORRUPTED;
        }

        if (depth == 0) {
                /* there is no tree at all */
                return 0;
        }

        if (ex != EXT_FIRST_EXTENT(eh)) {
                /* we correct tree if first leaf got modified only */
                return 0;
        }

        /*
         * TODO: we need correction if border is smaller than current one
         */
        k = depth - 1;
        border = path[depth].p_ext->ee_block;
        err = ext4_ext_get_access(handle, inode, path + k);
        if (err)
                return err;
        if (unlikely(path[k].p_idx > EXT_LAST_INDEX(path[k].p_hdr))) {
                EXT4_ERROR_INODE(inode,
                                 "path[%d].p_idx %p > EXT_LAST_INDEX %p",
                                 k, path[k].p_idx,
                                 EXT_LAST_INDEX(path[k].p_hdr));
                return -EFSCORRUPTED;
        }
        path[k].p_idx->ei_block = border;
        err = ext4_ext_dirty(handle, inode, path + k);
        if (err)
                return err;

        while (k--) {
                /* change all left-side indexes */
                if (path[k+1].p_idx != EXT_FIRST_INDEX(path[k+1].p_hdr))
                        break;
                err = ext4_ext_get_access(handle, inode, path + k);
                if (err)
                        goto clean;
                if (unlikely(path[k].p_idx > EXT_LAST_INDEX(path[k].p_hdr))) {
                        EXT4_ERROR_INODE(inode,
                                         "path[%d].p_idx %p > EXT_LAST_INDEX %p",
                                         k, path[k].p_idx,
                                         EXT_LAST_INDEX(path[k].p_hdr));
                        err = -EFSCORRUPTED;
                        goto clean;
                }
                path[k].p_idx->ei_block = border;
                err = ext4_ext_dirty(handle, inode, path + k);
                if (err)
                        goto clean;
        }
        return 0;

clean:
        /*
         * The path[k].p_bh is either unmodified or with no verified bit
         * set (see ext4_ext_get_access()). So just clear the verified bit
         * of the successfully modified extents buffers, which will force
         * these extents to be checked to avoid using inconsistent data.
         */
        while (++k < depth)
                clear_buffer_verified(path[k].p_bh);

        return err;
}

static int ext4_can_extents_be_merged(struct inode *inode,
                                      struct ext4_extent *ex1,
                                      struct ext4_extent *ex2)
{
        unsigned short ext1_ee_len, ext2_ee_len;

        if (ext4_ext_is_unwritten(ex1) != ext4_ext_is_unwritten(ex2))
                return 0;

        ext1_ee_len = ext4_ext_get_actual_len(ex1);
        ext2_ee_len = ext4_ext_get_actual_len(ex2);

        if (le32_to_cpu(ex1->ee_block) + ext1_ee_len !=
                        le32_to_cpu(ex2->ee_block))
                return 0;

        if (ext1_ee_len + ext2_ee_len > EXT_INIT_MAX_LEN)
                return 0;

        if (ext4_ext_is_unwritten(ex1) &&
            ext1_ee_len + ext2_ee_len > EXT_UNWRITTEN_MAX_LEN)
                return 0;
#ifdef AGGRESSIVE_TEST
        if (ext1_ee_len >= 4)
                return 0;
#endif

        if (ext4_ext_pblock(ex1) + ext1_ee_len == ext4_ext_pblock(ex2))
                return 1;
        return 0;
}

/*
 * This function tries to merge the "ex" extent to the next extent in the tree.
 * It always tries to merge towards right. If you want to merge towards
 * left, pass "ex - 1" as argument instead of "ex".
 * Returns 0 if the extents (ex and ex+1) were _not_ merged and returns
 * 1 if they got merged.
 */
static int ext4_ext_try_to_merge_right(struct inode *inode,
                                 struct ext4_ext_path *path,
                                 struct ext4_extent *ex)
{
        struct ext4_extent_header *eh;
        unsigned int depth, len;
        int merge_done = 0, unwritten;

        depth = ext_depth(inode);
        BUG_ON(path[depth].p_hdr == NULL);
        eh = path[depth].p_hdr;

        while (ex < EXT_LAST_EXTENT(eh)) {
                if (!ext4_can_extents_be_merged(inode, ex, ex + 1))
                        break;
                /* merge with next extent! */
                unwritten = ext4_ext_is_unwritten(ex);
                ex->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ex)
                                + ext4_ext_get_actual_len(ex + 1));
                if (unwritten)
                        ext4_ext_mark_unwritten(ex);

                if (ex + 1 < EXT_LAST_EXTENT(eh)) {
                        len = (EXT_LAST_EXTENT(eh) - ex - 1)
                                * sizeof(struct ext4_extent);
                        memmove(ex + 1, ex + 2, len);
                }
                le16_add_cpu(&eh->eh_entries, -1);
                merge_done = 1;
                WARN_ON(eh->eh_entries == 0);
                if (!eh->eh_entries)
                        EXT4_ERROR_INODE(inode, "eh->eh_entries = 0!");
        }

        return merge_done;
}

/*
 * This function does a very simple check to see if we can collapse
 * an extent tree with a single extent tree leaf block into the inode.
 */
static void ext4_ext_try_to_merge_up(handle_t *handle,
                                     struct inode *inode,
                                     struct ext4_ext_path *path)
{
        size_t s;
        unsigned max_root = ext4_ext_space_root(inode, 0);
        ext4_fsblk_t blk;

        if ((path[0].p_depth != 1) ||
            (le16_to_cpu(path[0].p_hdr->eh_entries) != 1) ||
            (le16_to_cpu(path[1].p_hdr->eh_entries) > max_root))
                return;

        /*
         * We need to modify the block allocation bitmap and the block
         * group descriptor to release the extent tree block.  If we
         * can't get the journal credits, give up.
         */
        if (ext4_journal_extend(handle, 2,
                        ext4_free_metadata_revoke_credits(inode->i_sb, 1)))
                return;

        /*
         * Copy the extent data up to the inode
         */
        blk = ext4_idx_pblock(path[0].p_idx);
        s = le16_to_cpu(path[1].p_hdr->eh_entries) *
                sizeof(struct ext4_extent_idx);
        s += sizeof(struct ext4_extent_header);

        path[1].p_maxdepth = path[0].p_maxdepth;
        memcpy(path[0].p_hdr, path[1].p_hdr, s);
        path[0].p_depth = 0;
        path[0].p_ext = EXT_FIRST_EXTENT(path[0].p_hdr) +
                (path[1].p_ext - EXT_FIRST_EXTENT(path[1].p_hdr));
        path[0].p_hdr->eh_max = cpu_to_le16(max_root);

        ext4_ext_path_brelse(path + 1);
        ext4_free_blocks(handle, inode, NULL, blk, 1,
                         EXT4_FREE_BLOCKS_METADATA | EXT4_FREE_BLOCKS_FORGET);
}

/*
 * This function tries to merge the @ex extent to neighbours in the tree, then
 * tries to collapse the extent tree into the inode.
 */
static void ext4_ext_try_to_merge(handle_t *handle,
                                  struct inode *inode,
                                  struct ext4_ext_path *path,
                                  struct ext4_extent *ex)
{
        struct ext4_extent_header *eh;
        unsigned int depth;
        int merge_done = 0;

        depth = ext_depth(inode);
        BUG_ON(path[depth].p_hdr == NULL);
        eh = path[depth].p_hdr;

        if (ex > EXT_FIRST_EXTENT(eh))
                merge_done = ext4_ext_try_to_merge_right(inode, path, ex - 1);

        if (!merge_done)
                (void) ext4_ext_try_to_merge_right(inode, path, ex);

        ext4_ext_try_to_merge_up(handle, inode, path);
}

/*
 * check if a portion of the "newext" extent overlaps with an
 * existing extent.
 *
 * If there is an overlap discovered, it updates the length of the newext
 * such that there will be no overlap, and then returns 1.
 * If there is no overlap found, it returns 0.
 */
static unsigned int ext4_ext_check_overlap(struct ext4_sb_info *sbi,
                                           struct inode *inode,
                                           struct ext4_extent *newext,
                                           struct ext4_ext_path *path)
{
        ext4_lblk_t b1, b2;
        unsigned int depth, len1;
        unsigned int ret = 0;

        b1 = le32_to_cpu(newext->ee_block);
        len1 = ext4_ext_get_actual_len(newext);
        depth = ext_depth(inode);
        if (!path[depth].p_ext)
                goto out;
        b2 = EXT4_LBLK_CMASK(sbi, le32_to_cpu(path[depth].p_ext->ee_block));

        /*
         * get the next allocated block if the extent in the path
         * is before the requested block(s)
         */
        if (b2 < b1) {
                b2 = ext4_ext_next_allocated_block(path);
                if (b2 == EXT_MAX_BLOCKS)
                        goto out;
                b2 = EXT4_LBLK_CMASK(sbi, b2);
        }

        /* check for wrap through zero on extent logical start block*/
        if (b1 + len1 < b1) {
                len1 = EXT_MAX_BLOCKS - b1;
                newext->ee_len = cpu_to_le16(len1);
                ret = 1;
        }

        /* check for overlap */
        if (b1 + len1 > b2) {
                newext->ee_len = cpu_to_le16(b2 - b1);
                ret = 1;
        }
out:
        return ret;
}

/*
 * ext4_ext_insert_extent:
 * tries to merge requested extent into the existing extent or
 * inserts requested extent as new one into the tree,
 * creating new leaf in the no-space case.
 */
struct ext4_ext_path *
ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
                       struct ext4_ext_path *path,
                       struct ext4_extent *newext, int gb_flags)
{
        struct ext4_extent_header *eh;
        struct ext4_extent *ex, *fex;
        struct ext4_extent *nearex; /* nearest extent */
        int depth, len, err = 0;
        ext4_lblk_t next;
        int mb_flags = 0, unwritten;

        KUNIT_STATIC_STUB_REDIRECT(ext4_ext_insert_extent, handle, inode, path,
                                   newext, gb_flags);

        if (gb_flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
                mb_flags |= EXT4_MB_DELALLOC_RESERVED;
        if (unlikely(ext4_ext_get_actual_len(newext) == 0)) {
                EXT4_ERROR_INODE(inode, "ext4_ext_get_actual_len(newext) == 0");
                err = -EFSCORRUPTED;
                goto errout;
        }
        depth = ext_depth(inode);
        ex = path[depth].p_ext;
        eh = path[depth].p_hdr;
        if (unlikely(path[depth].p_hdr == NULL)) {
                EXT4_ERROR_INODE(inode, "path[%d].p_hdr == NULL", depth);
                err = -EFSCORRUPTED;
                goto errout;
        }

        /* try to insert block into found extent and return */
        if (ex && !(gb_flags & EXT4_GET_BLOCKS_SPLIT_NOMERGE)) {

                /*
                 * Try to see whether we should rather test the extent on
                 * right from ex, or from the left of ex. This is because
                 * ext4_find_extent() can return either extent on the
                 * left, or on the right from the searched position. This
                 * will make merging more effective.
                 */
                if (ex < EXT_LAST_EXTENT(eh) &&
                    (le32_to_cpu(ex->ee_block) +
                    ext4_ext_get_actual_len(ex) <
                    le32_to_cpu(newext->ee_block))) {
                        ex += 1;
                        goto prepend;
                } else if ((ex > EXT_FIRST_EXTENT(eh)) &&
                           (le32_to_cpu(newext->ee_block) +
                           ext4_ext_get_actual_len(newext) <
                           le32_to_cpu(ex->ee_block)))
                        ex -= 1;

                /* Try to append newex to the ex */
                if (ext4_can_extents_be_merged(inode, ex, newext)) {
                        ext_debug(inode, "append [%d]%d block to %u:[%d]%d"
                                  "(from %llu)\n",
                                  ext4_ext_is_unwritten(newext),
                                  ext4_ext_get_actual_len(newext),
                                  le32_to_cpu(ex->ee_block),
                                  ext4_ext_is_unwritten(ex),
                                  ext4_ext_get_actual_len(ex),
                                  ext4_ext_pblock(ex));
                        err = ext4_ext_get_access(handle, inode,
                                                  path + depth);
                        if (err)
                                goto errout;
                        unwritten = ext4_ext_is_unwritten(ex);
                        ex->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ex)
                                        + ext4_ext_get_actual_len(newext));
                        if (unwritten)
                                ext4_ext_mark_unwritten(ex);
                        nearex = ex;
                        goto merge;
                }

prepend:
                /* Try to prepend newex to the ex */
                if (ext4_can_extents_be_merged(inode, newext, ex)) {
                        ext_debug(inode, "prepend %u[%d]%d block to %u:[%d]%d"
                                  "(from %llu)\n",
                                  le32_to_cpu(newext->ee_block),
                                  ext4_ext_is_unwritten(newext),
                                  ext4_ext_get_actual_len(newext),
                                  le32_to_cpu(ex->ee_block),
                                  ext4_ext_is_unwritten(ex),
                                  ext4_ext_get_actual_len(ex),
                                  ext4_ext_pblock(ex));
                        err = ext4_ext_get_access(handle, inode,
                                                  path + depth);
                        if (err)
                                goto errout;

                        unwritten = ext4_ext_is_unwritten(ex);
                        ex->ee_block = newext->ee_block;
                        ext4_ext_store_pblock(ex, ext4_ext_pblock(newext));
                        ex->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ex)
                                        + ext4_ext_get_actual_len(newext));
                        if (unwritten)
                                ext4_ext_mark_unwritten(ex);
                        nearex = ex;
                        goto merge;
                }
        }

        depth = ext_depth(inode);
        eh = path[depth].p_hdr;
        if (le16_to_cpu(eh->eh_entries) < le16_to_cpu(eh->eh_max))
                goto has_space;

        /* probably next leaf has space for us? */
        fex = EXT_LAST_EXTENT(eh);
        next = EXT_MAX_BLOCKS;
        if (le32_to_cpu(newext->ee_block) > le32_to_cpu(fex->ee_block))
                next = ext4_ext_next_leaf_block(path);
        if (next != EXT_MAX_BLOCKS) {
                struct ext4_ext_path *npath;

                ext_debug(inode, "next leaf block - %u\n", next);
                npath = ext4_find_extent(inode, next, NULL, gb_flags);
                if (IS_ERR(npath)) {
                        err = PTR_ERR(npath);
                        goto errout;
                }
                BUG_ON(npath->p_depth != path->p_depth);
                eh = npath[depth].p_hdr;
                if (le16_to_cpu(eh->eh_entries) < le16_to_cpu(eh->eh_max)) {
                        ext_debug(inode, "next leaf isn't full(%d)\n",
                                  le16_to_cpu(eh->eh_entries));
                        ext4_free_ext_path(path);
                        path = npath;
                        goto has_space;
                }
                ext_debug(inode, "next leaf has no free space(%d,%d)\n",
                          le16_to_cpu(eh->eh_entries), le16_to_cpu(eh->eh_max));
                ext4_free_ext_path(npath);
        }

        /*
         * There is no free space in the found leaf.
         * We're gonna add a new leaf in the tree.
         */
        if (gb_flags & EXT4_GET_BLOCKS_METADATA_NOFAIL)
                mb_flags |= EXT4_MB_USE_RESERVED;
        path = ext4_ext_create_new_leaf(handle, inode, mb_flags, gb_flags,
                                        path, newext);
        if (IS_ERR(path))
                return path;
        depth = ext_depth(inode);
        eh = path[depth].p_hdr;

has_space:
        nearex = path[depth].p_ext;

        err = ext4_ext_get_access(handle, inode, path + depth);
        if (err)
                goto errout;

        if (!nearex) {
                /* there is no extent in this leaf, create first one */
                ext_debug(inode, "first extent in the leaf: %u:%llu:[%d]%d\n",
                                le32_to_cpu(newext->ee_block),
                                ext4_ext_pblock(newext),
                                ext4_ext_is_unwritten(newext),
                                ext4_ext_get_actual_len(newext));
                nearex = EXT_FIRST_EXTENT(eh);
        } else {
                if (le32_to_cpu(newext->ee_block)
                           > le32_to_cpu(nearex->ee_block)) {
                        /* Insert after */
                        ext_debug(inode, "insert %u:%llu:[%d]%d before: "
                                        "nearest %p\n",
                                        le32_to_cpu(newext->ee_block),
                                        ext4_ext_pblock(newext),
                                        ext4_ext_is_unwritten(newext),
                                        ext4_ext_get_actual_len(newext),
                                        nearex);
                        nearex++;
                } else {
                        /* Insert before */
                        BUG_ON(newext->ee_block == nearex->ee_block);
                        ext_debug(inode, "insert %u:%llu:[%d]%d after: "
                                        "nearest %p\n",
                                        le32_to_cpu(newext->ee_block),
                                        ext4_ext_pblock(newext),
                                        ext4_ext_is_unwritten(newext),
                                        ext4_ext_get_actual_len(newext),
                                        nearex);
                }
                len = EXT_LAST_EXTENT(eh) - nearex + 1;
                if (len > 0) {
                        ext_debug(inode, "insert %u:%llu:[%d]%d: "
                                        "move %d extents from 0x%p to 0x%p\n",
                                        le32_to_cpu(newext->ee_block),
                                        ext4_ext_pblock(newext),
                                        ext4_ext_is_unwritten(newext),
                                        ext4_ext_get_actual_len(newext),
                                        len, nearex, nearex + 1);
                        memmove(nearex + 1, nearex,
                                len * sizeof(struct ext4_extent));
                }
        }

        le16_add_cpu(&eh->eh_entries, 1);
        path[depth].p_ext = nearex;
        nearex->ee_block = newext->ee_block;
        ext4_ext_store_pblock(nearex, ext4_ext_pblock(newext));
        nearex->ee_len = newext->ee_len;

merge:
        /* try to merge extents */
        if (!(gb_flags & EXT4_GET_BLOCKS_SPLIT_NOMERGE))
                ext4_ext_try_to_merge(handle, inode, path, nearex);

        /* time to correct all indexes above */
        err = ext4_ext_correct_indexes(handle, inode, path);
        if (err)
                goto errout;

        err = ext4_ext_dirty(handle, inode, path + path->p_depth);
        if (err)
                goto errout;

        return path;

errout:
        ext4_free_ext_path(path);
        return ERR_PTR(err);
}

static int ext4_fill_es_cache_info(struct inode *inode,
                                   ext4_lblk_t block, ext4_lblk_t num,
                                   struct fiemap_extent_info *fieinfo)
{
        ext4_lblk_t next, end = block + num - 1;
        struct extent_status es;
        unsigned char blksize_bits = inode->i_sb->s_blocksize_bits;
        unsigned int flags;
        int err;

        while (block <= end) {
                next = 0;
                flags = 0;
                if (!ext4_es_lookup_extent(inode, block, &next, &es, NULL))
                        break;
                if (ext4_es_is_unwritten(&es))
                        flags |= FIEMAP_EXTENT_UNWRITTEN;
                if (ext4_es_is_delayed(&es))
                        flags |= (FIEMAP_EXTENT_DELALLOC |
                                  FIEMAP_EXTENT_UNKNOWN);
                if (ext4_es_is_hole(&es))
                        flags |= EXT4_FIEMAP_EXTENT_HOLE;
                if (next == 0)
                        flags |= FIEMAP_EXTENT_LAST;
                if (flags & (FIEMAP_EXTENT_DELALLOC|
                             EXT4_FIEMAP_EXTENT_HOLE))
                        es.es_pblk = 0;
                else
                        es.es_pblk = ext4_es_pblock(&es);
                err = fiemap_fill_next_extent(fieinfo,
                                (__u64)es.es_lblk << blksize_bits,
                                (__u64)es.es_pblk << blksize_bits,
                                (__u64)es.es_len << blksize_bits,
                                flags);
                if (next == 0)
                        break;
                block = next;
                if (err < 0)
                        return err;
                if (err == 1)
                        return 0;
        }
        return 0;
}


/*
 * ext4_ext_find_hole - find hole around given block according to the given path
 * @inode:      inode we lookup in
 * @path:       path in extent tree to @lblk
 * @lblk:       pointer to logical block around which we want to determine hole
 *
 * Determine hole length (and start if easily possible) around given logical
 * block. We don't try too hard to find the beginning of the hole but @path
 * actually points to extent before @lblk, we provide it.
 *
 * The function returns the length of a hole starting at @lblk. We update @lblk
 * to the beginning of the hole if we managed to find it.
 */
static ext4_lblk_t ext4_ext_find_hole(struct inode *inode,
                                      struct ext4_ext_path *path,
                                      ext4_lblk_t *lblk)
{
        int depth = ext_depth(inode);
        struct ext4_extent *ex;
        ext4_lblk_t len;

        ex = path[depth].p_ext;
        if (ex == NULL) {
                /* there is no extent yet, so gap is [0;-] */
                *lblk = 0;
                len = EXT_MAX_BLOCKS;
        } else if (*lblk < le32_to_cpu(ex->ee_block)) {
                len = le32_to_cpu(ex->ee_block) - *lblk;
        } else if (*lblk >= le32_to_cpu(ex->ee_block)
                        + ext4_ext_get_actual_len(ex)) {
                ext4_lblk_t next;

                *lblk = le32_to_cpu(ex->ee_block) + ext4_ext_get_actual_len(ex);
                next = ext4_ext_next_allocated_block(path);
                BUG_ON(next == *lblk);
                len = next - *lblk;
        } else {
                BUG();
        }
        return len;
}

/*
 * ext4_ext_rm_idx:
 * removes index from the index block.
 */
static int ext4_ext_rm_idx(handle_t *handle, struct inode *inode,
                        struct ext4_ext_path *path, int depth)
{
        int err;
        ext4_fsblk_t leaf;
        int k = depth - 1;

        /* free index block */
        leaf = ext4_idx_pblock(path[k].p_idx);
        if (unlikely(path[k].p_hdr->eh_entries == 0)) {
                EXT4_ERROR_INODE(inode, "path[%d].p_hdr->eh_entries == 0", k);
                return -EFSCORRUPTED;
        }
        err = ext4_ext_get_access(handle, inode, path + k);
        if (err)
                return err;

        if (path[k].p_idx != EXT_LAST_INDEX(path[k].p_hdr)) {
                int len = EXT_LAST_INDEX(path[k].p_hdr) - path[k].p_idx;
                len *= sizeof(struct ext4_extent_idx);
                memmove(path[k].p_idx, path[k].p_idx + 1, len);
        }

        le16_add_cpu(&path[k].p_hdr->eh_entries, -1);
        err = ext4_ext_dirty(handle, inode, path + k);
        if (err)
                return err;
        ext_debug(inode, "index is empty, remove it, free block %llu\n", leaf);
        trace_ext4_ext_rm_idx(inode, leaf);

        ext4_free_blocks(handle, inode, NULL, leaf, 1,
                         EXT4_FREE_BLOCKS_METADATA | EXT4_FREE_BLOCKS_FORGET);

        while (--k >= 0) {
                if (path[k + 1].p_idx != EXT_FIRST_INDEX(path[k + 1].p_hdr))
                        break;
                err = ext4_ext_get_access(handle, inode, path + k);
                if (err)
                        goto clean;
                path[k].p_idx->ei_block = path[k + 1].p_idx->ei_block;
                err = ext4_ext_dirty(handle, inode, path + k);
                if (err)
                        goto clean;
        }
        return 0;

clean:
        /*
         * The path[k].p_bh is either unmodified or with no verified bit
         * set (see ext4_ext_get_access()). So just clear the verified bit
         * of the successfully modified extents buffers, which will force
         * these extents to be checked to avoid using inconsistent data.
         */
        while (++k < depth)
                clear_buffer_verified(path[k].p_bh);

        return err;
}

/*
 * ext4_ext_calc_credits_for_single_extent:
 * This routine returns max. credits that needed to insert an extent
 * to the extent tree.
 * When pass the actual path, the caller should calculate credits
 * under i_data_sem.
 */
int ext4_ext_calc_credits_for_single_extent(struct inode *inode, int nrblocks,
                                                struct ext4_ext_path *path)
{
        if (path) {
                int depth = ext_depth(inode);
                int ret = 0;

                /* probably there is space in leaf? */
                if (le16_to_cpu(path[depth].p_hdr->eh_entries)
                                < le16_to_cpu(path[depth].p_hdr->eh_max)) {

                        /*
                         *  There are some space in the leaf tree, no
                         *  need to account for leaf block credit
                         *
                         *  bitmaps and block group descriptor blocks
                         *  and other metadata blocks still need to be
                         *  accounted.
                         */
                        /* 1 bitmap, 1 block group descriptor */
                        ret = 2 + EXT4_META_TRANS_BLOCKS(inode->i_sb);
                        return ret;
                }
        }

        return ext4_chunk_trans_blocks(inode, nrblocks);
}

/*
 * How many index/leaf blocks need to change/allocate to add @extents extents?
 *
 * If we add a single extent, then in the worse case, each tree level
 * index/leaf need to be changed in case of the tree split.
 *
 * If more extents are inserted, they could cause the whole tree split more
 * than once, but this is really rare.
 */
int ext4_ext_index_trans_blocks(struct inode *inode, int extents)
{
        int index;

        /* If we are converting the inline data, only one is needed here. */
        if (ext4_has_inline_data(inode))
                return 1;

        /*
         * Extent tree can change between the time we estimate credits and
         * the time we actually modify the tree. Assume the worst case.
         */
        if (extents <= 1)
                index = (EXT4_MAX_EXTENT_DEPTH * 2) + extents;
        else
                index = (EXT4_MAX_EXTENT_DEPTH * 3) +
                        DIV_ROUND_UP(extents, ext4_ext_space_block(inode, 0));

        return index;
}

static inline int get_default_free_blocks_flags(struct inode *inode)
{
        if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode) ||
            ext4_test_inode_flag(inode, EXT4_INODE_EA_INODE))
                return EXT4_FREE_BLOCKS_METADATA | EXT4_FREE_BLOCKS_FORGET;
        else if (ext4_should_journal_data(inode))
                return EXT4_FREE_BLOCKS_FORGET;
        return 0;
}

/*
 * ext4_rereserve_cluster - increment the reserved cluster count when
 *                          freeing a cluster with a pending reservation
 *
 * @inode - file containing the cluster
 * @lblk - logical block in cluster to be reserved
 *
 * Increments the reserved cluster count and adjusts quota in a bigalloc
 * file system when freeing a partial cluster containing at least one
 * delayed and unwritten block.  A partial cluster meeting that
 * requirement will have a pending reservation.  If so, the
 * RERESERVE_CLUSTER flag is used when calling ext4_free_blocks() to
 * defer reserved and allocated space accounting to a subsequent call
 * to this function.
 */
static void ext4_rereserve_cluster(struct inode *inode, ext4_lblk_t lblk)
{
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
        struct ext4_inode_info *ei = EXT4_I(inode);

        dquot_reclaim_block(inode, EXT4_C2B(sbi, 1));

        spin_lock(&ei->i_block_reservation_lock);
        ei->i_reserved_data_blocks++;
        percpu_counter_add(&sbi->s_dirtyclusters_counter, 1);
        spin_unlock(&ei->i_block_reservation_lock);

        percpu_counter_add(&sbi->s_freeclusters_counter, 1);
        ext4_remove_pending(inode, lblk);
}

static int ext4_remove_blocks(handle_t *handle, struct inode *inode,
                              struct ext4_extent *ex,
                              struct partial_cluster *partial,
                              ext4_lblk_t from, ext4_lblk_t to)
{
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
        unsigned short ee_len = ext4_ext_get_actual_len(ex);
        ext4_fsblk_t last_pblk, pblk;
        ext4_lblk_t num;
        int flags;

        /* only extent tail removal is allowed */
        if (from < le32_to_cpu(ex->ee_block) ||
            to != le32_to_cpu(ex->ee_block) + ee_len - 1) {
                ext4_error(sbi->s_sb,
                           "strange request: removal(2) %u-%u from %u:%u",
                           from, to, le32_to_cpu(ex->ee_block), ee_len);
                return 0;
        }

#ifdef EXTENTS_STATS
        spin_lock(&sbi->s_ext_stats_lock);
        sbi->s_ext_blocks += ee_len;
        sbi->s_ext_extents++;
        if (ee_len < sbi->s_ext_min)
                sbi->s_ext_min = ee_len;
        if (ee_len > sbi->s_ext_max)
                sbi->s_ext_max = ee_len;
        if (ext_depth(inode) > sbi->s_depth_max)
                sbi->s_depth_max = ext_depth(inode);
        spin_unlock(&sbi->s_ext_stats_lock);
#endif

        trace_ext4_remove_blocks(inode, ex, from, to, partial);

        /*
         * if we have a partial cluster, and it's different from the
         * cluster of the last block in the extent, we free it
         */
        last_pblk = ext4_ext_pblock(ex) + ee_len - 1;

        if (partial->state != initial &&
            partial->pclu != EXT4_B2C(sbi, last_pblk)) {
                if (partial->state == tofree) {
                        flags = get_default_free_blocks_flags(inode);
                        if (ext4_is_pending(inode, partial->lblk))
                                flags |= EXT4_FREE_BLOCKS_RERESERVE_CLUSTER;
                        ext4_free_blocks(handle, inode, NULL,
                                         EXT4_C2B(sbi, partial->pclu),
                                         sbi->s_cluster_ratio, flags);
                        if (flags & EXT4_FREE_BLOCKS_RERESERVE_CLUSTER)
                                ext4_rereserve_cluster(inode, partial->lblk);
                }
                partial->state = initial;
        }

        num = le32_to_cpu(ex->ee_block) + ee_len - from;
        pblk = ext4_ext_pblock(ex) + ee_len - num;

        /*
         * We free the partial cluster at the end of the extent (if any),
         * unless the cluster is used by another extent (partial_cluster
         * state is nofree).  If a partial cluster exists here, it must be
         * shared with the last block in the extent.
         */
        flags = get_default_free_blocks_flags(inode);

        /* partial, left end cluster aligned, right end unaligned */
        if ((EXT4_LBLK_COFF(sbi, to) != sbi->s_cluster_ratio - 1) &&
            (EXT4_LBLK_CMASK(sbi, to) >= from) &&
            (partial->state != nofree)) {
                if (ext4_is_pending(inode, to))
                        flags |= EXT4_FREE_BLOCKS_RERESERVE_CLUSTER;
                ext4_free_blocks(handle, inode, NULL,
                                 EXT4_PBLK_CMASK(sbi, last_pblk),
                                 sbi->s_cluster_ratio, flags);
                if (flags & EXT4_FREE_BLOCKS_RERESERVE_CLUSTER)
                        ext4_rereserve_cluster(inode, to);
                partial->state = initial;
                flags = get_default_free_blocks_flags(inode);
        }

        flags |= EXT4_FREE_BLOCKS_NOFREE_LAST_CLUSTER;

        /*
         * For bigalloc file systems, we never free a partial cluster
         * at the beginning of the extent.  Instead, we check to see if we
         * need to free it on a subsequent call to ext4_remove_blocks,
         * or at the end of ext4_ext_rm_leaf or ext4_ext_remove_space.
         */
        flags |= EXT4_FREE_BLOCKS_NOFREE_FIRST_CLUSTER;
        ext4_free_blocks(handle, inode, NULL, pblk, num, flags);

        /* reset the partial cluster if we've freed past it */
        if (partial->state != initial && partial->pclu != EXT4_B2C(sbi, pblk))
                partial->state = initial;

        /*
         * If we've freed the entire extent but the beginning is not left
         * cluster aligned and is not marked as ineligible for freeing we
         * record the partial cluster at the beginning of the extent.  It
         * wasn't freed by the preceding ext4_free_blocks() call, and we
         * need to look farther to the left to determine if it's to be freed
         * (not shared with another extent). Else, reset the partial
         * cluster - we're either  done freeing or the beginning of the
         * extent is left cluster aligned.
         */
        if (EXT4_LBLK_COFF(sbi, from) && num == ee_len) {
                if (partial->state == initial) {
                        partial->pclu = EXT4_B2C(sbi, pblk);
                        partial->lblk = from;
                        partial->state = tofree;
                }
        } else {
                partial->state = initial;
        }

        return 0;
}

/*
 * ext4_ext_rm_leaf() Removes the extents associated with the
 * blocks appearing between "start" and "end".  Both "start"
 * and "end" must appear in the same extent or EIO is returned.
 *
 * @handle: The journal handle
 * @inode:  The files inode
 * @path:   The path to the leaf
 * @partial_cluster: The cluster which we'll have to free if all extents
 *                   has been released from it.  However, if this value is
 *                   negative, it's a cluster just to the right of the
 *                   punched region and it must not be freed.
 * @start:  The first block to remove
 * @end:   The last block to remove
 */
static int
ext4_ext_rm_leaf(handle_t *handle, struct inode *inode,
                 struct ext4_ext_path *path,
                 struct partial_cluster *partial,
                 ext4_lblk_t start, ext4_lblk_t end)
{
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
        int err = 0, correct_index = 0;
        int depth = ext_depth(inode), credits, revoke_credits;
        struct ext4_extent_header *eh;
        ext4_lblk_t a, b;
        unsigned num;
        ext4_lblk_t ex_ee_block;
        unsigned short ex_ee_len;
        unsigned unwritten = 0;
        struct ext4_extent *ex;
        ext4_fsblk_t pblk;

        /* the header must be checked already in ext4_ext_remove_space() */
        ext_debug(inode, "truncate since %u in leaf to %u\n", start, end);
        if (!path[depth].p_hdr)
                path[depth].p_hdr = ext_block_hdr(path[depth].p_bh);
        eh = path[depth].p_hdr;
        if (unlikely(path[depth].p_hdr == NULL)) {
                EXT4_ERROR_INODE(inode, "path[%d].p_hdr == NULL", depth);
                return -EFSCORRUPTED;
        }
        /* find where to start removing */
        ex = path[depth].p_ext;
        if (!ex)
                ex = EXT_LAST_EXTENT(eh);

        ex_ee_block = le32_to_cpu(ex->ee_block);
        ex_ee_len = ext4_ext_get_actual_len(ex);

        trace_ext4_ext_rm_leaf(inode, start, ex, partial);

        while (ex >= EXT_FIRST_EXTENT(eh) &&
                        ex_ee_block + ex_ee_len > start) {

                if (ext4_ext_is_unwritten(ex))
                        unwritten = 1;
                else
                        unwritten = 0;

                ext_debug(inode, "remove ext %u:[%d]%d\n", ex_ee_block,
                          unwritten, ex_ee_len);
                path[depth].p_ext = ex;

                a = max(ex_ee_block, start);
                b = min(ex_ee_block + ex_ee_len - 1, end);

                ext_debug(inode, "  border %u:%u\n", a, b);

                /* If this extent is beyond the end of the hole, skip it */
                if (end < ex_ee_block) {
                        /*
                         * We're going to skip this extent and move to another,
                         * so note that its first cluster is in use to avoid
                         * freeing it when removing blocks.  Eventually, the
                         * right edge of the truncated/punched region will
                         * be just to the left.
                         */
                        if (sbi->s_cluster_ratio > 1) {
                                pblk = ext4_ext_pblock(ex);
                                partial->pclu = EXT4_B2C(sbi, pblk);
                                partial->state = nofree;
                        }
                        ex--;
                        ex_ee_block = le32_to_cpu(ex->ee_block);
                        ex_ee_len = ext4_ext_get_actual_len(ex);
                        continue;
                } else if (b != ex_ee_block + ex_ee_len - 1) {
                        EXT4_ERROR_INODE(inode,
                                         "can not handle truncate %u:%u "
                                         "on extent %u:%u",
                                         start, end, ex_ee_block,
                                         ex_ee_block + ex_ee_len - 1);
                        err = -EFSCORRUPTED;
                        goto out;
                } else if (a != ex_ee_block) {
                        /* remove tail of the extent */
                        num = a - ex_ee_block;
                } else {
                        /* remove whole extent: excellent! */
                        num = 0;
                }
                /*
                 * 3 for leaf, sb, and inode plus 2 (bmap and group
                 * descriptor) for each block group; assume two block
                 * groups plus ex_ee_len/blocks_per_block_group for
                 * the worst case
                 */
                credits = 7 + 2*(ex_ee_len/EXT4_BLOCKS_PER_GROUP(inode->i_sb));
                if (ex == EXT_FIRST_EXTENT(eh)) {
                        correct_index = 1;
                        credits += (ext_depth(inode)) + 1;
                }
                credits += EXT4_MAXQUOTAS_TRANS_BLOCKS(inode->i_sb);
                /*
                 * We may end up freeing some index blocks and data from the
                 * punched range. Note that partial clusters are accounted for
                 * by ext4_free_data_revoke_credits().
                 */
                revoke_credits =
                        ext4_free_metadata_revoke_credits(inode->i_sb,
                                                          ext_depth(inode)) +
                        ext4_free_data_revoke_credits(inode, b - a + 1);

                err = ext4_datasem_ensure_credits(handle, inode, credits,
                                                  credits, revoke_credits);
                if (err) {
                        if (err > 0)
                                err = -EAGAIN;
                        goto out;
                }

                err = ext4_ext_get_access(handle, inode, path + depth);
                if (err)
                        goto out;

                err = ext4_remove_blocks(handle, inode, ex, partial, a, b);
                if (err)
                        goto out;

                if (num == 0)
                        /* this extent is removed; mark slot entirely unused */
                        ext4_ext_store_pblock(ex, 0);

                ex->ee_len = cpu_to_le16(num);
                /*
                 * Do not mark unwritten if all the blocks in the
                 * extent have been removed.
                 */
                if (unwritten && num)
                        ext4_ext_mark_unwritten(ex);
                /*
                 * If the extent was completely released,
                 * we need to remove it from the leaf
                 */
                if (num == 0) {
                        if (end != EXT_MAX_BLOCKS - 1) {
                                /*
                                 * For hole punching, we need to scoot all the
                                 * extents up when an extent is removed so that
                                 * we dont have blank extents in the middle
                                 */
                                memmove(ex, ex+1, (EXT_LAST_EXTENT(eh) - ex) *
                                        sizeof(struct ext4_extent));

                                /* Now get rid of the one at the end */
                                memset(EXT_LAST_EXTENT(eh), 0,
                                        sizeof(struct ext4_extent));
                        }
                        le16_add_cpu(&eh->eh_entries, -1);
                }

                err = ext4_ext_dirty(handle, inode, path + depth);
                if (err)
                        goto out;

                ext_debug(inode, "new extent: %u:%u:%llu\n", ex_ee_block, num,
                                ext4_ext_pblock(ex));
                ex--;
                ex_ee_block = le32_to_cpu(ex->ee_block);
                ex_ee_len = ext4_ext_get_actual_len(ex);
        }

        if (correct_index && eh->eh_entries)
                err = ext4_ext_correct_indexes(handle, inode, path);

        /*
         * If there's a partial cluster and at least one extent remains in
         * the leaf, free the partial cluster if it isn't shared with the
         * current extent.  If it is shared with the current extent
         * we reset the partial cluster because we've reached the start of the
         * truncated/punched region and we're done removing blocks.
         */
        if (partial->state == tofree && ex >= EXT_FIRST_EXTENT(eh)) {
                pblk = ext4_ext_pblock(ex) + ex_ee_len - 1;
                if (partial->pclu != EXT4_B2C(sbi, pblk)) {
                        int flags = get_default_free_blocks_flags(inode);

                        if (ext4_is_pending(inode, partial->lblk))
                                flags |= EXT4_FREE_BLOCKS_RERESERVE_CLUSTER;
                        ext4_free_blocks(handle, inode, NULL,
                                         EXT4_C2B(sbi, partial->pclu),
                                         sbi->s_cluster_ratio, flags);
                        if (flags & EXT4_FREE_BLOCKS_RERESERVE_CLUSTER)
                                ext4_rereserve_cluster(inode, partial->lblk);
                }
                partial->state = initial;
        }

        /* if this leaf is free, then we should
         * remove it from index block above */
        if (err == 0 && eh->eh_entries == 0 && path[depth].p_bh != NULL)
                err = ext4_ext_rm_idx(handle, inode, path, depth);

out:
        return err;
}

/*
 * ext4_ext_more_to_rm:
 * returns 1 if current index has to be freed (even partial)
 */
static int
ext4_ext_more_to_rm(struct ext4_ext_path *path)
{
        BUG_ON(path->p_idx == NULL);

        if (path->p_idx < EXT_FIRST_INDEX(path->p_hdr))
                return 0;

        /*
         * if truncate on deeper level happened, it wasn't partial,
         * so we have to consider current index for truncation
         */
        if (le16_to_cpu(path->p_hdr->eh_entries) == path->p_block)
                return 0;
        return 1;
}

int ext4_ext_remove_space(struct inode *inode, ext4_lblk_t start,
                          ext4_lblk_t end)
{
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
        int depth = ext_depth(inode);
        struct ext4_ext_path *path = NULL;
        struct partial_cluster partial;
        handle_t *handle;
        int i = 0, err = 0;
        int flags = EXT4_EX_NOCACHE | EXT4_EX_NOFAIL;

        partial.pclu = 0;
        partial.lblk = 0;
        partial.state = initial;

        ext_debug(inode, "truncate since %u to %u\n", start, end);

        /* probably first extent we're gonna free will be last in block */
        handle = ext4_journal_start_with_revoke(inode, EXT4_HT_TRUNCATE,
                        depth + 1,
                        ext4_free_metadata_revoke_credits(inode->i_sb, depth));
        if (IS_ERR(handle))
                return PTR_ERR(handle);

again:
        trace_ext4_ext_remove_space(inode, start, end, depth);

        /*
         * Check if we are removing extents inside the extent tree. If that
         * is the case, we are going to punch a hole inside the extent tree
         * so we have to check whether we need to split the extent covering
         * the last block to remove so we can easily remove the part of it
         * in ext4_ext_rm_leaf().
         */
        if (end < EXT_MAX_BLOCKS - 1) {
                struct ext4_extent *ex;
                ext4_lblk_t ee_block, ex_end, lblk;
                ext4_fsblk_t pblk;

                /* find extent for or closest extent to this block */
                path = ext4_find_extent(inode, end, NULL, flags);
                if (IS_ERR(path)) {
                        ext4_journal_stop(handle);
                        return PTR_ERR(path);
                }
                depth = ext_depth(inode);
                /* Leaf not may not exist only if inode has no blocks at all */
                ex = path[depth].p_ext;
                if (!ex) {
                        if (depth) {
                                EXT4_ERROR_INODE(inode,
                                                 "path[%d].p_hdr == NULL",
                                                 depth);
                                err = -EFSCORRUPTED;
                        }
                        goto out;
                }

                ee_block = le32_to_cpu(ex->ee_block);
                ex_end = ee_block + ext4_ext_get_actual_len(ex) - 1;

                /*
                 * See if the last block is inside the extent, if so split
                 * the extent at 'end' block so we can easily remove the
                 * tail of the first part of the split extent in
                 * ext4_ext_rm_leaf().
                 */
                if (end >= ee_block && end < ex_end) {

                        /*
                         * If we're going to split the extent, note that
                         * the cluster containing the block after 'end' is
                         * in use to avoid freeing it when removing blocks.
                         */
                        if (sbi->s_cluster_ratio > 1) {
                                pblk = ext4_ext_pblock(ex) + end - ee_block + 1;
                                partial.pclu = EXT4_B2C(sbi, pblk);
                                partial.state = nofree;
                        }

                        /*
                         * Split the extent in two so that 'end' is the last
                         * block in the first new extent. Also we should not
                         * fail removing space due to ENOSPC so try to use
                         * reserved block if that happens.
                         */
                        path = ext4_force_split_extent_at(handle, inode, path,
                                                          end + 1, 1);
                        if (IS_ERR(path)) {
                                err = PTR_ERR(path);
                                goto out;
                        }
                } else if (sbi->s_cluster_ratio > 1 && end >= ex_end &&
                           partial.state == initial) {
                        /*
                         * If we're punching, there's an extent to the right.
                         * If the partial cluster hasn't been set, set it to
                         * that extent's first cluster and its state to nofree
                         * so it won't be freed should it contain blocks to be
                         * removed. If it's already set (tofree/nofree), we're
                         * retrying and keep the original partial cluster info
                         * so a cluster marked tofree as a result of earlier
                         * extent removal is not lost.
                         */
                        lblk = ex_end + 1;
                        err = ext4_ext_search_right(inode, path, &lblk, &pblk,
                                                    NULL, flags);
                        if (err < 0)
                                goto out;
                        if (pblk) {
                                partial.pclu = EXT4_B2C(sbi, pblk);
                                partial.state = nofree;
                        }
                }
        }
        /*
         * We start scanning from right side, freeing all the blocks
         * after i_size and walking into the tree depth-wise.
         */
        depth = ext_depth(inode);
        if (path) {
                int k = i = depth;
                while (--k > 0)
                        path[k].p_block =
                                le16_to_cpu(path[k].p_hdr->eh_entries)+1;
        } else {
                path = kzalloc_objs(struct ext4_ext_path, depth + 1,
                                    GFP_NOFS | __GFP_NOFAIL);
                path[0].p_maxdepth = path[0].p_depth = depth;
                path[0].p_hdr = ext_inode_hdr(inode);
                i = 0;

                if (ext4_ext_check(inode, path[0].p_hdr, depth, 0)) {
                        err = -EFSCORRUPTED;
                        goto out;
                }
        }
        err = 0;

        while (i >= 0 && err == 0) {
                if (i == depth) {
                        /* this is leaf block */
                        err = ext4_ext_rm_leaf(handle, inode, path,
                                               &partial, start, end);
                        /* root level has p_bh == NULL, brelse() eats this */
                        ext4_ext_path_brelse(path + i);
                        i--;
                        continue;
                }

                /* this is index block */
                if (!path[i].p_hdr) {
                        ext_debug(inode, "initialize header\n");
                        path[i].p_hdr = ext_block_hdr(path[i].p_bh);
                }

                if (!path[i].p_idx) {
                        /* this level hasn't been touched yet */
                        path[i].p_idx = EXT_LAST_INDEX(path[i].p_hdr);
                        path[i].p_block = le16_to_cpu(path[i].p_hdr->eh_entries)+1;
                        ext_debug(inode, "init index ptr: hdr 0x%p, num %d\n",
                                  path[i].p_hdr,
                                  le16_to_cpu(path[i].p_hdr->eh_entries));
                } else {
                        /* we were already here, see at next index */
                        path[i].p_idx--;
                }

                ext_debug(inode, "level %d - index, first 0x%p, cur 0x%p\n",
                                i, EXT_FIRST_INDEX(path[i].p_hdr),
                                path[i].p_idx);
                if (ext4_ext_more_to_rm(path + i)) {
                        struct buffer_head *bh;
                        /* go to the next level */
                        ext_debug(inode, "move to level %d (block %llu)\n",
                                  i + 1, ext4_idx_pblock(path[i].p_idx));
                        memset(path + i + 1, 0, sizeof(*path));
                        bh = read_extent_tree_block(inode, path[i].p_idx,
                                                    depth - i - 1, flags);
                        if (IS_ERR(bh)) {
                                /* should we reset i_size? */
                                err = PTR_ERR(bh);
                                break;
                        }
                        /* Yield here to deal with large extent trees.
                         * Should be a no-op if we did IO above. */
                        cond_resched();
                        if (WARN_ON(i + 1 > depth)) {
                                err = -EFSCORRUPTED;
                                break;
                        }
                        path[i + 1].p_bh = bh;

                        /* save actual number of indexes since this
                         * number is changed at the next iteration */
                        path[i].p_block = le16_to_cpu(path[i].p_hdr->eh_entries);
                        i++;
                } else {
                        /* we finished processing this index, go up */
                        if (path[i].p_hdr->eh_entries == 0 && i > 0) {
                                /* index is empty, remove it;
                                 * handle must be already prepared by the
                                 * truncatei_leaf() */
                                err = ext4_ext_rm_idx(handle, inode, path, i);
                        }
                        /* root level has p_bh == NULL, brelse() eats this */
                        ext4_ext_path_brelse(path + i);
                        i--;
                        ext_debug(inode, "return to level %d\n", i);
                }
        }

        trace_ext4_ext_remove_space_done(inode, start, end, depth, &partial,
                                         path->p_hdr->eh_entries);

        /*
         * if there's a partial cluster and we have removed the first extent
         * in the file, then we also free the partial cluster, if any
         */
        if (partial.state == tofree && err == 0) {
                int flags = get_default_free_blocks_flags(inode);

                if (ext4_is_pending(inode, partial.lblk))
                        flags |= EXT4_FREE_BLOCKS_RERESERVE_CLUSTER;
                ext4_free_blocks(handle, inode, NULL,
                                 EXT4_C2B(sbi, partial.pclu),
                                 sbi->s_cluster_ratio, flags);
                if (flags & EXT4_FREE_BLOCKS_RERESERVE_CLUSTER)
                        ext4_rereserve_cluster(inode, partial.lblk);
                partial.state = initial;
        }

        /* TODO: flexible tree reduction should be here */
        if (path->p_hdr->eh_entries == 0) {
                /*
                 * truncate to zero freed all the tree,
                 * so we need to correct eh_depth
                 */
                err = ext4_ext_get_access(handle, inode, path);
                if (err == 0) {
                        ext_inode_hdr(inode)->eh_depth = 0;
                        ext_inode_hdr(inode)->eh_max =
                                cpu_to_le16(ext4_ext_space_root(inode, 0));
                        err = ext4_ext_dirty(handle, inode, path);
                }
        }
out:
        ext4_free_ext_path(path);
        path = NULL;
        if (err == -EAGAIN)
                goto again;
        ext4_journal_stop(handle);

        return err;
}

/*
 * called at mount time
 */
void ext4_ext_init(struct super_block *sb)
{
        /*
         * possible initialization would be here
         */

        if (ext4_has_feature_extents(sb)) {
#if defined(AGGRESSIVE_TEST) || defined(CHECK_BINSEARCH) || defined(EXTENTS_STATS)
                printk(KERN_INFO "EXT4-fs: file extents enabled"
#ifdef AGGRESSIVE_TEST
                       ", aggressive tests"
#endif
#ifdef CHECK_BINSEARCH
                       ", check binsearch"
#endif
#ifdef EXTENTS_STATS
                       ", stats"
#endif
                       "\n");
#endif
#ifdef EXTENTS_STATS
                spin_lock_init(&EXT4_SB(sb)->s_ext_stats_lock);
                EXT4_SB(sb)->s_ext_min = 1 << 30;
                EXT4_SB(sb)->s_ext_max = 0;
#endif
        }
}

/*
 * called at umount time
 */
void ext4_ext_release(struct super_block *sb)
{
        if (!ext4_has_feature_extents(sb))
                return;

#ifdef EXTENTS_STATS
        if (EXT4_SB(sb)->s_ext_blocks && EXT4_SB(sb)->s_ext_extents) {
                struct ext4_sb_info *sbi = EXT4_SB(sb);
                printk(KERN_ERR "EXT4-fs: %lu blocks in %lu extents (%lu ave)\n",
                        sbi->s_ext_blocks, sbi->s_ext_extents,
                        sbi->s_ext_blocks / sbi->s_ext_extents);
                printk(KERN_ERR "EXT4-fs: extents: %lu min, %lu max, max depth %lu\n",
                        sbi->s_ext_min, sbi->s_ext_max, sbi->s_depth_max);
        }
#endif
}

static void ext4_zeroout_es(struct inode *inode, struct ext4_extent *ex)
{
        ext4_lblk_t  ee_block;
        ext4_fsblk_t ee_pblock;
        unsigned int ee_len;

        ee_block = le32_to_cpu(ex->ee_block);
        ee_len = ext4_ext_get_actual_len(ex);
        ee_pblock = ext4_ext_pblock(ex);

        if (ee_len == 0)
                return;

        ext4_es_insert_extent(inode, ee_block, ee_len, ee_pblock,
                              EXTENT_STATUS_WRITTEN, false);
}

/* FIXME!! we need to try to merge to left or right after zero-out  */
int ext4_ext_zeroout(struct inode *inode, struct ext4_extent *ex)
{
        ext4_fsblk_t ee_pblock;
        unsigned int ee_len;

        KUNIT_STATIC_STUB_REDIRECT(ext4_ext_zeroout, inode, ex);

        ee_len    = ext4_ext_get_actual_len(ex);
        ee_pblock = ext4_ext_pblock(ex);
        return ext4_issue_zeroout(inode, le32_to_cpu(ex->ee_block), ee_pblock,
                                  ee_len);
}

/*
 * ext4_split_extent_at() splits an extent at given block.
 *
 * @handle: the journal handle
 * @inode: the file inode
 * @path: the path to the extent
 * @split: the logical block where the extent is splitted.
 * @flags: flags used to insert new extent to extent tree.
 *
 *
 * Splits extent [a, b] into two extents [a, @split) and [@split, b], states
 * of which are same as the original extent. No conversion is performed.
 *
 * Return an extent path pointer on success, or an error pointer on failure. On
 * failure, the extent is restored to original state.
 */
static struct ext4_ext_path *ext4_split_extent_at(handle_t *handle,
                                                  struct inode *inode,
                                                  struct ext4_ext_path *path,
                                                  ext4_lblk_t split,
                                                  int flags)
{
        ext4_fsblk_t newblock;
        ext4_lblk_t ee_block;
        struct ext4_extent *ex, newex, orig_ex;
        struct ext4_extent *ex2 = NULL;
        unsigned int ee_len, depth;
        int err = 0, insert_err = 0, is_unwrit = 0;

        /* Do not cache extents that are in the process of being modified. */
        flags |= EXT4_EX_NOCACHE;

        ext_debug(inode, "logical block %llu\n", (unsigned long long)split);

        ext4_ext_show_leaf(inode, path);

        depth = ext_depth(inode);
        ex = path[depth].p_ext;
        ee_block = le32_to_cpu(ex->ee_block);
        ee_len = ext4_ext_get_actual_len(ex);
        newblock = split - ee_block + ext4_ext_pblock(ex);
        is_unwrit = ext4_ext_is_unwritten(ex);

        BUG_ON(split < ee_block || split >= (ee_block + ee_len));

        /*
         * No split needed
         */
        if (split == ee_block)
                goto out;

        err = ext4_ext_get_access(handle, inode, path + depth);
        if (err)
                goto out;

        /* case a */
        memcpy(&orig_ex, ex, sizeof(orig_ex));
        ex->ee_len = cpu_to_le16(split - ee_block);
        if (is_unwrit)
                ext4_ext_mark_unwritten(ex);

        /*
         * path may lead to new leaf, not to original leaf any more
         * after ext4_ext_insert_extent() returns,
         */
        err = ext4_ext_dirty(handle, inode, path + depth);
        if (err)
                goto fix_extent_len;

        ex2 = &newex;
        ex2->ee_block = cpu_to_le32(split);
        ex2->ee_len   = cpu_to_le16(ee_len - (split - ee_block));
        ext4_ext_store_pblock(ex2, newblock);
        if (is_unwrit)
                ext4_ext_mark_unwritten(ex2);

        path = ext4_ext_insert_extent(handle, inode, path, &newex, flags);
        if (!IS_ERR(path))
                return path;

        insert_err = PTR_ERR(path);
        err = 0;
        if (insert_err != -ENOSPC && insert_err != -EDQUOT &&
            insert_err != -ENOMEM)
                goto out_path;

        /*
         * Get a new path to try to zeroout or fix the extent length.
         * Using EXT4_EX_NOFAIL guarantees that ext4_find_extent()
         * will not return -ENOMEM, otherwise -ENOMEM will cause a
         * retry in do_writepages(), and a WARN_ON may be triggered
         * in ext4_da_update_reserve_space() due to an incorrect
         * ee_len causing the i_reserved_data_blocks exception.
         */
        path = ext4_find_extent(inode, ee_block, NULL, flags | EXT4_EX_NOFAIL);
        if (IS_ERR(path)) {
                EXT4_ERROR_INODE(inode, "Failed split extent on %u, err %ld",
                                 split, PTR_ERR(path));
                goto out_path;
        }

        depth = ext_depth(inode);
        ex = path[depth].p_ext;
        if (!ex) {
                EXT4_ERROR_INODE(inode,
                                 "bad extent address lblock: %lu, depth: %d pblock %llu",
                                 (unsigned long)ee_block, depth, path[depth].p_block);
                err = -EFSCORRUPTED;
                goto out;
        }

        err = ext4_ext_get_access(handle, inode, path + depth);
        if (err)
                goto out;

fix_extent_len:
        ex->ee_len = orig_ex.ee_len;
        err = ext4_ext_dirty(handle, inode, path + path->p_depth);
out:
        if (err || insert_err) {
                ext4_free_ext_path(path);
                path = err ? ERR_PTR(err) : ERR_PTR(insert_err);
        }
out_path:
        if (IS_ERR(path))
                /* Remove all remaining potentially stale extents. */
                ext4_es_remove_extent(inode, ee_block, ee_len);
        ext4_ext_show_leaf(inode, path);
        return path;
}

static int ext4_split_extent_zeroout(handle_t *handle, struct inode *inode,
                                     struct ext4_ext_path *path,
                                     struct ext4_map_blocks *map, int flags)
{
        struct ext4_extent *ex;
        unsigned int ee_len, depth;
        ext4_lblk_t ee_block;
        uint64_t lblk, pblk, len;
        int is_unwrit;
        int err = 0;

        depth = ext_depth(inode);
        ex = path[depth].p_ext;
        ee_block = le32_to_cpu(ex->ee_block);
        ee_len = ext4_ext_get_actual_len(ex);
        is_unwrit = ext4_ext_is_unwritten(ex);

        if (flags & EXT4_GET_BLOCKS_CONVERT) {
                /*
                 * EXT4_GET_BLOCKS_CONVERT: Caller wants the range specified by
                 * map to be initialized. Zeroout everything except the map
                 * range.
                 */

                loff_t map_end = (loff_t) map->m_lblk + map->m_len;
                loff_t ex_end = (loff_t) ee_block + ee_len;

                if (!is_unwrit)
                        /* Shouldn't happen. Just exit */
                        return -EINVAL;

                /* zeroout left */
                if (map->m_lblk > ee_block) {
                        lblk = ee_block;
                        len = map->m_lblk - ee_block;
                        pblk = ext4_ext_pblock(ex);
                        err = ext4_issue_zeroout(inode, lblk, pblk, len);
                        if (err)
                                /* ZEROOUT failed, just return original error */
                                return err;
                }

                /* zeroout right */
                if (map_end < ex_end) {
                        lblk = map_end;
                        len = ex_end - map_end;
                        pblk = ext4_ext_pblock(ex) + (map_end - ee_block);
                        err = ext4_issue_zeroout(inode, lblk, pblk, len);
                        if (err)
                                /* ZEROOUT failed, just return original error */
                                return err;
                }
        } else if (flags & EXT4_GET_BLOCKS_CONVERT_UNWRITTEN) {
                /*
                 * EXT4_GET_BLOCKS_CONVERT_UNWRITTEN: Caller wants the
                 * range specified by map to be marked unwritten.
                 * Zeroout the map range leaving rest as it is.
                 */

                if (is_unwrit)
                        /* Shouldn't happen. Just exit */
                        return -EINVAL;

                lblk = map->m_lblk;
                len = map->m_len;
                pblk = ext4_ext_pblock(ex) + (map->m_lblk - ee_block);
                err = ext4_issue_zeroout(inode, lblk, pblk, len);
                if (err)
                        /* ZEROOUT failed, just return original error */
                        return err;
        } else {
                /*
                 * We no longer perform unwritten to unwritten splits in IO paths.
                 * Hence this should not happen.
                 */
                WARN_ON_ONCE(true);
                return -EINVAL;
        }

        err = ext4_ext_get_access(handle, inode, path + depth);
        if (err)
                return err;

        ext4_ext_mark_initialized(ex);

        err = ext4_ext_dirty(handle, inode, path + depth);
        if (err)
                return err;

        return 0;
}

/*
 * ext4_split_extent() splits an extent and mark extent which is covered
 * by @map as split_flags indicates
 *
 * It may result in splitting the extent into multiple extents (up to three)
 * There are three possibilities:
 *   a> There is no split required
 *   b> Splits in two extents: Split is happening at either end of the extent
 *   c> Splits in three extents: Somone is splitting in middle of the extent
 *
 */
static struct ext4_ext_path *ext4_split_extent(handle_t *handle,
                                               struct inode *inode,
                                               struct ext4_ext_path *path,
                                               struct ext4_map_blocks *map,
                                               int split_flag, int flags,
                                               unsigned int *allocated, bool *did_zeroout)
{
        ext4_lblk_t ee_block, orig_ee_block;
        struct ext4_extent *ex;
        unsigned int ee_len, orig_ee_len, depth;
        int unwritten, orig_unwritten;
        int orig_err = 0;

        depth = ext_depth(inode);
        ex = path[depth].p_ext;
        ee_block = le32_to_cpu(ex->ee_block);
        ee_len = ext4_ext_get_actual_len(ex);
        unwritten = ext4_ext_is_unwritten(ex);

        orig_ee_block = ee_block;
        orig_ee_len = ee_len;
        orig_unwritten = unwritten;

        /* Do not cache extents that are in the process of being modified. */
        flags |= EXT4_EX_NOCACHE;

        if (map->m_lblk + map->m_len < ee_block + ee_len) {
                path = ext4_split_extent_at(handle, inode, path,
                                            map->m_lblk + map->m_len, flags);
                if (IS_ERR(path))
                        goto try_zeroout;

                /*
                 * Update path is required because previous ext4_split_extent_at
                 * may result in split of original leaf or extent zeroout.
                 */
                path = ext4_find_extent(inode, map->m_lblk, path, flags);
                if (IS_ERR(path))
                        goto try_zeroout;

                depth = ext_depth(inode);
                ex = path[depth].p_ext;
                if (!ex) {
                        EXT4_ERROR_INODE(inode, "unexpected hole at %lu",
                                        (unsigned long) map->m_lblk);
                        ext4_free_ext_path(path);
                        return ERR_PTR(-EFSCORRUPTED);
                }

                /* extent would have changed so update original values */
                orig_ee_block = le32_to_cpu(ex->ee_block);
                orig_ee_len = ext4_ext_get_actual_len(ex);
                orig_unwritten = ext4_ext_is_unwritten(ex);
        }

        if (map->m_lblk >= ee_block) {
                path = ext4_split_extent_at(handle, inode, path, map->m_lblk,
                                            flags);
                if (IS_ERR(path))
                        goto try_zeroout;
        }

        goto success;

try_zeroout:
        /*
         * There was an error in splitting the extent. So instead, just zeroout
         * unwritten portions and convert it to initialized as a last resort. If
         * there is any failure here we just return the original error
         */

        orig_err = PTR_ERR(path);
        if (orig_err != -ENOSPC && orig_err != -EDQUOT && orig_err != -ENOMEM)
                goto out_orig_err;

        /* we can't zeroout? just return the original err */
        if (!(split_flag & EXT4_EXT_MAY_ZEROOUT))
                goto out_orig_err;

        if (flags & EXT4_GET_BLOCKS_CONVERT_UNWRITTEN) {
                int max_zeroout_blks =
                        EXT4_SB(inode->i_sb)->s_extent_max_zeroout_kb >>
                        (inode->i_sb->s_blocksize_bits - 10);

                if (map->m_len > max_zeroout_blks)
                        goto out_orig_err;
        }

        path = ext4_find_extent(inode, map->m_lblk, NULL, flags);
        if (IS_ERR(path))
                goto out_orig_err;

        depth = ext_depth(inode);
        ex = path[depth].p_ext;
        ee_block = le32_to_cpu(ex->ee_block);
        ee_len = ext4_ext_get_actual_len(ex);
        unwritten = ext4_ext_is_unwritten(ex);

        /* extent to zeroout should have been unchanged but its not */
        if (WARN_ON(ee_block != orig_ee_block || ee_len != orig_ee_len ||
                    unwritten != orig_unwritten))
                goto out_free_path;

        if (ext4_split_extent_zeroout(handle, inode, path, map, flags))
                goto out_free_path;

        /* zeroout succeeded */
        if (did_zeroout)
                *did_zeroout = true;

success:
        if (allocated) {
                if (map->m_lblk + map->m_len > ee_block + ee_len)
                        *allocated = ee_len - (map->m_lblk - ee_block);
                else
                        *allocated = map->m_len;
        }
        ext4_ext_show_leaf(inode, path);
        return path;

out_free_path:
        ext4_free_ext_path(path);
out_orig_err:
        return ERR_PTR(orig_err);

}

/*
 * This function is called by ext4_ext_map_blocks() if someone tries to write
 * to an unwritten extent. It may result in splitting the unwritten
 * extent into multiple extents (up to three - one initialized and two
 * unwritten).
 * There are three possibilities:
 *   a> There is no split required: Entire extent should be initialized
 *   b> Splits in two extents: Write is happening at either end of the extent
 *   c> Splits in three extents: Somone is writing in middle of the extent
 *
 * Pre-conditions:
 *  - The extent pointed to by 'path' is unwritten.
 *  - The extent pointed to by 'path' contains a superset
 *    of the logical span [map->m_lblk, map->m_lblk + map->m_len).
 *
 * Post-conditions on success:
 *  - the returned value is the number of blocks beyond map->l_lblk
 *    that are allocated and initialized.
 *    It is guaranteed to be >= map->m_len.
 */
static struct ext4_ext_path *
ext4_ext_convert_to_initialized(handle_t *handle, struct inode *inode,
                        struct ext4_map_blocks *map, struct ext4_ext_path *path,
                        int flags, unsigned int *allocated)
{
        struct ext4_sb_info *sbi;
        struct ext4_extent_header *eh;
        struct ext4_map_blocks split_map;
        struct ext4_extent zero_ex1, zero_ex2;
        struct ext4_extent *ex, *abut_ex;
        ext4_lblk_t ee_block, eof_block;
        unsigned int ee_len, depth, map_len = map->m_len;
        int err = 0;
        unsigned int max_zeroout = 0;

        ext_debug(inode, "logical block %llu, max_blocks %u\n",
                  (unsigned long long)map->m_lblk, map_len);

        sbi = EXT4_SB(inode->i_sb);
        eof_block = (EXT4_I(inode)->i_disksize + inode->i_sb->s_blocksize - 1)
                        >> inode->i_sb->s_blocksize_bits;
        if (eof_block < map->m_lblk + map_len)
                eof_block = map->m_lblk + map_len;

        depth = ext_depth(inode);
        eh = path[depth].p_hdr;
        ex = path[depth].p_ext;
        ee_block = le32_to_cpu(ex->ee_block);
        ee_len = ext4_ext_get_actual_len(ex);
        zero_ex1.ee_len = 0;
        zero_ex2.ee_len = 0;

        trace_ext4_ext_convert_to_initialized_enter(inode, map, ex);

        /* Pre-conditions */
        BUG_ON(!ext4_ext_is_unwritten(ex));
        BUG_ON(!in_range(map->m_lblk, ee_block, ee_len));

        /*
         * Attempt to transfer newly initialized blocks from the currently
         * unwritten extent to its neighbor. This is much cheaper
         * than an insertion followed by a merge as those involve costly
         * memmove() calls. Transferring to the left is the common case in
         * steady state for workloads doing fallocate(FALLOC_FL_KEEP_SIZE)
         * followed by append writes.
         *
         * Limitations of the current logic:
         *  - L1: we do not deal with writes covering the whole extent.
         *    This would require removing the extent if the transfer
         *    is possible.
         *  - L2: we only attempt to merge with an extent stored in the
         *    same extent tree node.
         */
        *allocated = 0;
        if ((map->m_lblk == ee_block) &&
                /* See if we can merge left */
                (map_len < ee_len) &&           /*L1*/
                (ex > EXT_FIRST_EXTENT(eh))) {  /*L2*/
                ext4_lblk_t prev_lblk;
                ext4_fsblk_t prev_pblk, ee_pblk;
                unsigned int prev_len;

                abut_ex = ex - 1;
                prev_lblk = le32_to_cpu(abut_ex->ee_block);
                prev_len = ext4_ext_get_actual_len(abut_ex);
                prev_pblk = ext4_ext_pblock(abut_ex);
                ee_pblk = ext4_ext_pblock(ex);

                /*
                 * A transfer of blocks from 'ex' to 'abut_ex' is allowed
                 * upon those conditions:
                 * - C1: abut_ex is initialized,
                 * - C2: abut_ex is logically abutting ex,
                 * - C3: abut_ex is physically abutting ex,
                 * - C4: abut_ex can receive the additional blocks without
                 *   overflowing the (initialized) length limit.
                 */
                if ((!ext4_ext_is_unwritten(abut_ex)) &&                /*C1*/
                        ((prev_lblk + prev_len) == ee_block) &&         /*C2*/
                        ((prev_pblk + prev_len) == ee_pblk) &&          /*C3*/
                        (prev_len < (EXT_INIT_MAX_LEN - map_len))) {    /*C4*/
                        err = ext4_ext_get_access(handle, inode, path + depth);
                        if (err)
                                goto errout;

                        trace_ext4_ext_convert_to_initialized_fastpath(inode,
                                map, ex, abut_ex);

                        /* Shift the start of ex by 'map_len' blocks */
                        ex->ee_block = cpu_to_le32(ee_block + map_len);
                        ext4_ext_store_pblock(ex, ee_pblk + map_len);
                        ex->ee_len = cpu_to_le16(ee_len - map_len);
                        ext4_ext_mark_unwritten(ex); /* Restore the flag */

                        /* Extend abut_ex by 'map_len' blocks */
                        abut_ex->ee_len = cpu_to_le16(prev_len + map_len);

                        /* Result: number of initialized blocks past m_lblk */
                        *allocated = map_len;
                }
        } else if (((map->m_lblk + map_len) == (ee_block + ee_len)) &&
                   (map_len < ee_len) &&        /*L1*/
                   ex < EXT_LAST_EXTENT(eh)) {  /*L2*/
                /* See if we can merge right */
                ext4_lblk_t next_lblk;
                ext4_fsblk_t next_pblk, ee_pblk;
                unsigned int next_len;

                abut_ex = ex + 1;
                next_lblk = le32_to_cpu(abut_ex->ee_block);
                next_len = ext4_ext_get_actual_len(abut_ex);
                next_pblk = ext4_ext_pblock(abut_ex);
                ee_pblk = ext4_ext_pblock(ex);

                /*
                 * A transfer of blocks from 'ex' to 'abut_ex' is allowed
                 * upon those conditions:
                 * - C1: abut_ex is initialized,
                 * - C2: abut_ex is logically abutting ex,
                 * - C3: abut_ex is physically abutting ex,
                 * - C4: abut_ex can receive the additional blocks without
                 *   overflowing the (initialized) length limit.
                 */
                if ((!ext4_ext_is_unwritten(abut_ex)) &&                /*C1*/
                    ((map->m_lblk + map_len) == next_lblk) &&           /*C2*/
                    ((ee_pblk + ee_len) == next_pblk) &&                /*C3*/
                    (next_len < (EXT_INIT_MAX_LEN - map_len))) {        /*C4*/
                        err = ext4_ext_get_access(handle, inode, path + depth);
                        if (err)
                                goto errout;

                        trace_ext4_ext_convert_to_initialized_fastpath(inode,
                                map, ex, abut_ex);

                        /* Shift the start of abut_ex by 'map_len' blocks */
                        abut_ex->ee_block = cpu_to_le32(next_lblk - map_len);
                        ext4_ext_store_pblock(abut_ex, next_pblk - map_len);
                        ex->ee_len = cpu_to_le16(ee_len - map_len);
                        ext4_ext_mark_unwritten(ex); /* Restore the flag */

                        /* Extend abut_ex by 'map_len' blocks */
                        abut_ex->ee_len = cpu_to_le16(next_len + map_len);

                        /* Result: number of initialized blocks past m_lblk */
                        *allocated = map_len;
                }
        }
        if (*allocated) {
                /* Mark the block containing both extents as dirty */
                err = ext4_ext_dirty(handle, inode, path + depth);

                /* Update path to point to the right extent */
                path[depth].p_ext = abut_ex;
                if (err)
                        goto errout;
                goto out;
        } else
                *allocated = ee_len - (map->m_lblk - ee_block);

        WARN_ON(map->m_lblk < ee_block);
        /*
         * It is safe to convert extent to initialized via explicit
         * zeroout only if extent is fully inside i_size or new_size.
         */
        if (ee_block + ee_len <= eof_block)
                max_zeroout = sbi->s_extent_max_zeroout_kb >>
                        (inode->i_sb->s_blocksize_bits - 10);

        /*
         * five cases:
         * 1. split the extent into three extents.
         * 2. split the extent into two extents, zeroout the head of the first
         *    extent.
         * 3. split the extent into two extents, zeroout the tail of the second
         *    extent.
         * 4. split the extent into two extents with out zeroout.
         * 5. no splitting needed, just possibly zeroout the head and / or the
         *    tail of the extent.
         */
        split_map.m_lblk = map->m_lblk;
        split_map.m_len = map->m_len;

        if (max_zeroout && (*allocated > split_map.m_len)) {
                if (*allocated <= max_zeroout) {
                        /* case 3 or 5 */
                        zero_ex1.ee_block =
                                 cpu_to_le32(split_map.m_lblk +
                                             split_map.m_len);
                        zero_ex1.ee_len =
                                cpu_to_le16(*allocated - split_map.m_len);
                        ext4_ext_store_pblock(&zero_ex1,
                                ext4_ext_pblock(ex) + split_map.m_lblk +
                                split_map.m_len - ee_block);
                        err = ext4_ext_zeroout(inode, &zero_ex1);
                        if (err)
                                goto fallback;
                        split_map.m_len = *allocated;
                }
                if (split_map.m_lblk - ee_block + split_map.m_len <
                                                                max_zeroout) {
                        /* case 2 or 5 */
                        if (split_map.m_lblk != ee_block) {
                                zero_ex2.ee_block = ex->ee_block;
                                zero_ex2.ee_len = cpu_to_le16(split_map.m_lblk -
                                                        ee_block);
                                ext4_ext_store_pblock(&zero_ex2,
                                                      ext4_ext_pblock(ex));
                                err = ext4_ext_zeroout(inode, &zero_ex2);
                                if (err)
                                        goto fallback;
                        }

                        split_map.m_len += split_map.m_lblk - ee_block;
                        split_map.m_lblk = ee_block;
                        *allocated = map->m_len;
                }
        }

fallback:
        path = ext4_split_convert_extents(handle, inode, &split_map, path,
                                          flags | EXT4_GET_BLOCKS_CONVERT, NULL);
        if (IS_ERR(path))
                return path;
out:
        /* If we have gotten a failure, don't zero out status tree */
        ext4_zeroout_es(inode, &zero_ex1);
        ext4_zeroout_es(inode, &zero_ex2);
        return path;

errout:
        ext4_free_ext_path(path);
        return ERR_PTR(err);
}

/*
 * This function is called by ext4_ext_map_blocks() from
 * ext4_get_blocks_dio_write() when DIO to write
 * to an unwritten extent.
 *
 * Writing to an unwritten extent may result in splitting the unwritten
 * extent into multiple initialized/unwritten extents (up to three)
 * There are three possibilities:
 *   a> There is no split required: Entire extent should be unwritten
 *   b> Splits in two extents: Write is happening at either end of the extent
 *   c> Splits in three extents: Somone is writing in middle of the extent
 *
 * This works the same way in the case of initialized -> unwritten conversion.
 *
 * One of more index blocks maybe needed if the extent tree grow after
 * the unwritten extent split. To prevent ENOSPC occur at the IO
 * complete, we need to split the unwritten extent before DIO submit
 * the IO. The unwritten extent called at this time will be split
 * into three unwritten extent(at most). After IO complete, the part
 * being filled will be convert to initialized by the end_io callback function
 * via ext4_convert_unwritten_extents().
 *
 * The size of unwritten extent to be written is passed to the caller via the
 * allocated pointer. Return an extent path pointer on success, or an error
 * pointer on failure.
 */
static struct ext4_ext_path *ext4_split_convert_extents(handle_t *handle,
                                        struct inode *inode,
                                        struct ext4_map_blocks *map,
                                        struct ext4_ext_path *path,
                                        int flags, unsigned int *allocated)
{
        ext4_lblk_t eof_block;
        ext4_lblk_t ee_block;
        struct ext4_extent *ex;
        unsigned int ee_len;
        int split_flag = 0, depth, err = 0;
        bool did_zeroout = false;

        ext_debug(inode, "logical block %llu, max_blocks %u\n",
                  (unsigned long long)map->m_lblk, map->m_len);

        eof_block = (EXT4_I(inode)->i_disksize + inode->i_sb->s_blocksize - 1)
                        >> inode->i_sb->s_blocksize_bits;
        if (eof_block < map->m_lblk + map->m_len)
                eof_block = map->m_lblk + map->m_len;
        depth = ext_depth(inode);
        ex = path[depth].p_ext;
        ee_block = le32_to_cpu(ex->ee_block);
        ee_len = ext4_ext_get_actual_len(ex);

        /* No split needed */
        if (ee_block == map->m_lblk && ee_len == map->m_len)
                goto convert;

        /*
         * It is only safe to convert extent to initialized via explicit
         * zeroout only if extent is fully inside i_size or new_size.
         */
        split_flag |= ee_block + ee_len <= eof_block ? EXT4_EXT_MAY_ZEROOUT : 0;

        /*
         * pass SPLIT_NOMERGE explicitly so we don't end up merging extents we
         * just split.
         */
        path = ext4_split_extent(handle, inode, path, map, split_flag,
                                 flags | EXT4_GET_BLOCKS_SPLIT_NOMERGE,
                                 allocated, &did_zeroout);
        if (IS_ERR(path))
                return path;

convert:
        path = ext4_find_extent(inode, map->m_lblk, path, flags);
        if (IS_ERR(path))
                return path;

        depth = ext_depth(inode);
        ex = path[depth].p_ext;

        /*
         * Conversion is already handled in case of zeroout
         */
        if (!did_zeroout) {
                err = ext4_ext_get_access(handle, inode, path + depth);
                if (err)
                        goto err;

                if (flags & EXT4_GET_BLOCKS_CONVERT)
                        ext4_ext_mark_initialized(ex);
                else if (flags & EXT4_GET_BLOCKS_CONVERT_UNWRITTEN)
                        ext4_ext_mark_unwritten(ex);

                if (!(flags & EXT4_GET_BLOCKS_SPLIT_NOMERGE))
                       /*
                        * note: ext4_ext_correct_indexes() isn't needed here because
                        * borders are not changed
                        */
                        ext4_ext_try_to_merge(handle, inode, path, ex);

                err = ext4_ext_dirty(handle, inode, path + depth);
                if (err)
                        goto err;
        }

        /* Lets update the extent status tree after conversion */
        if (!(flags & EXT4_EX_NOCACHE))
                ext4_es_insert_extent(inode, le32_to_cpu(ex->ee_block),
                                      ext4_ext_get_actual_len(ex),
                                      ext4_ext_pblock(ex),
                                      ext4_ext_is_unwritten(ex) ?
                                              EXTENT_STATUS_UNWRITTEN :
                                              EXTENT_STATUS_WRITTEN,
                                      false);

err:
        if (err) {
                ext4_free_ext_path(path);
                return ERR_PTR(err);
        }

        return path;
}

static struct ext4_ext_path *
ext4_convert_unwritten_extents_endio(handle_t *handle, struct inode *inode,
                                     struct ext4_map_blocks *map,
                                     struct ext4_ext_path *path, int flags)
{
        struct ext4_extent *ex;
        ext4_lblk_t ee_block;
        unsigned int ee_len;
        int depth;

        depth = ext_depth(inode);
        ex = path[depth].p_ext;
        ee_block = le32_to_cpu(ex->ee_block);
        ee_len = ext4_ext_get_actual_len(ex);

        ext_debug(inode, "logical block %llu, max_blocks %u\n",
                  (unsigned long long)ee_block, ee_len);

        return ext4_split_convert_extents(handle, inode, map, path, flags,
                                          NULL);
}

static struct ext4_ext_path *
convert_initialized_extent(handle_t *handle, struct inode *inode,
                           struct ext4_map_blocks *map,
                           struct ext4_ext_path *path,
                           int flags,
                           unsigned int *allocated)
{
        struct ext4_extent *ex;
        ext4_lblk_t ee_block;
        unsigned int ee_len;
        int depth;

        /*
         * Make sure that the extent is no bigger than we support with
         * unwritten extent
         */
        if (map->m_len > EXT_UNWRITTEN_MAX_LEN)
                map->m_len = EXT_UNWRITTEN_MAX_LEN / 2;

        depth = ext_depth(inode);
        ex = path[depth].p_ext;
        ee_block = le32_to_cpu(ex->ee_block);
        ee_len = ext4_ext_get_actual_len(ex);

        ext_debug(inode, "logical block %llu, max_blocks %u\n",
                  (unsigned long long)ee_block, ee_len);

        path = ext4_split_convert_extents(handle, inode, map, path, flags,
                                          NULL);
        if (IS_ERR(path))
                return path;

        ext4_ext_show_leaf(inode, path);

        ext4_update_inode_fsync_trans(handle, inode, 1);

        /*
         * The extent might be initialized in case of zeroout.
         */
        path = ext4_find_extent(inode, map->m_lblk, path, flags);
        if (IS_ERR(path))
                return path;

        depth = ext_depth(inode);
        ex = path[depth].p_ext;

        if (ext4_ext_is_unwritten(ex))
                map->m_flags |= EXT4_MAP_UNWRITTEN;
        else
                map->m_flags |= EXT4_MAP_MAPPED;
        if (*allocated > map->m_len)
                *allocated = map->m_len;
        map->m_len = *allocated;
        return path;
}

static struct ext4_ext_path *
ext4_ext_handle_unwritten_extents(handle_t *handle, struct inode *inode,
                        struct ext4_map_blocks *map,
                        struct ext4_ext_path *path, int flags,
                        unsigned int *allocated, ext4_fsblk_t newblock)
{
        int err = 0;

        ext_debug(inode, "logical block %llu, max_blocks %u, flags 0x%x, allocated %u\n",
                  (unsigned long long)map->m_lblk, map->m_len, flags,
                  *allocated);
        ext4_ext_show_leaf(inode, path);

        /*
         * When writing into unwritten space, we should not fail to
         * allocate metadata blocks for the new extent block if needed.
         */
        flags |= EXT4_GET_BLOCKS_METADATA_NOFAIL;

        trace_ext4_ext_handle_unwritten_extents(inode, map, flags,
                                                *allocated, newblock);

        /* IO end_io complete, convert the filled extent to written */
        if (flags & EXT4_GET_BLOCKS_CONVERT) {
                path = ext4_convert_unwritten_extents_endio(handle, inode,
                                                            map, path, flags);
                if (IS_ERR(path))
                        return path;
                ext4_update_inode_fsync_trans(handle, inode, 1);
                goto map_out;
        }
        /* buffered IO cases */
        /*
         * repeat fallocate creation request
         * we already have an unwritten extent
         */
        if (flags & EXT4_GET_BLOCKS_UNWRIT_EXT) {
                map->m_flags |= EXT4_MAP_UNWRITTEN;
                goto map_out;
        }

        /* buffered READ or buffered write_begin() lookup */
        if ((flags & EXT4_GET_BLOCKS_CREATE) == 0) {
                /*
                 * We have blocks reserved already.  We
                 * return allocated blocks so that delalloc
                 * won't do block reservation for us.  But
                 * the buffer head will be unmapped so that
                 * a read from the block returns 0s.
                 */
                map->m_flags |= EXT4_MAP_UNWRITTEN;
                goto out1;
        }

        /*
         * Default case when (flags & EXT4_GET_BLOCKS_CREATE) == 1.
         * For buffered writes, at writepage time, etc.  Convert a
         * discovered unwritten extent to written.
         */
        path = ext4_ext_convert_to_initialized(handle, inode, map, path,
                                               flags, allocated);
        if (IS_ERR(path))
                return path;
        ext4_update_inode_fsync_trans(handle, inode, 1);
        /*
         * shouldn't get a 0 allocated when converting an unwritten extent
         * unless m_len is 0 (bug) or extent has been corrupted
         */
        if (unlikely(*allocated == 0)) {
                EXT4_ERROR_INODE(inode, "unexpected allocated == 0, m_len = %u",
                                 map->m_len);
                err = -EFSCORRUPTED;
                goto errout;
        }

        map->m_flags |= EXT4_MAP_NEW;
map_out:
        map->m_flags |= EXT4_MAP_MAPPED;
out1:
        map->m_pblk = newblock;
        if (*allocated > map->m_len)
                *allocated = map->m_len;
        map->m_len = *allocated;
        ext4_ext_show_leaf(inode, path);
        return path;

errout:
        ext4_free_ext_path(path);
        return ERR_PTR(err);
}

/*
 * get_implied_cluster_alloc - check to see if the requested
 * allocation (in the map structure) overlaps with a cluster already
 * allocated in an extent.
 *      @sb     The filesystem superblock structure
 *      @map    The requested lblk->pblk mapping
 *      @ex     The extent structure which might contain an implied
 *                      cluster allocation
 *
 * This function is called by ext4_ext_map_blocks() after we failed to
 * find blocks that were already in the inode's extent tree.  Hence,
 * we know that the beginning of the requested region cannot overlap
 * the extent from the inode's extent tree.  There are three cases we
 * want to catch.  The first is this case:
 *
 *               |--- cluster # N--|
 *    |--- extent ---|  |---- requested region ---|
 *                      |==========|
 *
 * The second case that we need to test for is this one:
 *
 *   |--------- cluster # N ----------------|
 *         |--- requested region --|   |------- extent ----|
 *         |=======================|
 *
 * The third case is when the requested region lies between two extents
 * within the same cluster:
 *          |------------- cluster # N-------------|
 * |----- ex -----|                  |---- ex_right ----|
 *                  |------ requested region ------|
 *                  |================|
 *
 * In each of the above cases, we need to set the map->m_pblk and
 * map->m_len so it corresponds to the return the extent labelled as
 * "|====|" from cluster #N, since it is already in use for data in
 * cluster EXT4_B2C(sbi, map->m_lblk).  We will then return 1 to
 * signal to ext4_ext_map_blocks() that map->m_pblk should be treated
 * as a new "allocated" block region.  Otherwise, we will return 0 and
 * ext4_ext_map_blocks() will then allocate one or more new clusters
 * by calling ext4_mb_new_blocks().
 */
static int get_implied_cluster_alloc(struct super_block *sb,
                                     struct ext4_map_blocks *map,
                                     struct ext4_extent *ex,
                                     struct ext4_ext_path *path)
{
        struct ext4_sb_info *sbi = EXT4_SB(sb);
        ext4_lblk_t c_offset = EXT4_LBLK_COFF(sbi, map->m_lblk);
        ext4_lblk_t ex_cluster_start, ex_cluster_end;
        ext4_lblk_t rr_cluster_start;
        ext4_lblk_t ee_block = le32_to_cpu(ex->ee_block);
        ext4_fsblk_t ee_start = ext4_ext_pblock(ex);
        unsigned short ee_len = ext4_ext_get_actual_len(ex);

        /* The extent passed in that we are trying to match */
        ex_cluster_start = EXT4_B2C(sbi, ee_block);
        ex_cluster_end = EXT4_B2C(sbi, ee_block + ee_len - 1);

        /* The requested region passed into ext4_map_blocks() */
        rr_cluster_start = EXT4_B2C(sbi, map->m_lblk);

        if ((rr_cluster_start == ex_cluster_end) ||
            (rr_cluster_start == ex_cluster_start)) {
                if (rr_cluster_start == ex_cluster_end)
                        ee_start += ee_len - 1;
                map->m_pblk = EXT4_PBLK_CMASK(sbi, ee_start) + c_offset;
                map->m_len = min(map->m_len,
                                 (unsigned) sbi->s_cluster_ratio - c_offset);
                /*
                 * Check for and handle this case:
                 *
                 *   |--------- cluster # N-------------|
                 *                     |------- extent ----|
                 *         |--- requested region ---|
                 *         |===========|
                 */

                if (map->m_lblk < ee_block)
                        map->m_len = min(map->m_len, ee_block - map->m_lblk);

                /*
                 * Check for the case where there is already another allocated
                 * block to the right of 'ex' but before the end of the cluster.
                 *
                 *          |------------- cluster # N-------------|
                 * |----- ex -----|                  |---- ex_right ----|
                 *                  |------ requested region ------|
                 *                  |================|
                 */
                if (map->m_lblk > ee_block) {
                        ext4_lblk_t next = ext4_ext_next_allocated_block(path);
                        map->m_len = min(map->m_len, next - map->m_lblk);
                }

                trace_ext4_get_implied_cluster_alloc_exit(sb, map, 1);
                return 1;
        }

        trace_ext4_get_implied_cluster_alloc_exit(sb, map, 0);
        return 0;
}

/*
 * Determine hole length around the given logical block, first try to
 * locate and expand the hole from the given @path, and then adjust it
 * if it's partially or completely converted to delayed extents, insert
 * it into the extent cache tree if it's indeed a hole, finally return
 * the length of the determined extent.
 */
static ext4_lblk_t ext4_ext_determine_insert_hole(struct inode *inode,
                                                  struct ext4_ext_path *path,
                                                  ext4_lblk_t lblk)
{
        ext4_lblk_t hole_start, len;
        struct extent_status es;

        hole_start = lblk;
        len = ext4_ext_find_hole(inode, path, &hole_start);
again:
        ext4_es_find_extent_range(inode, &ext4_es_is_delayed, hole_start,
                                  hole_start + len - 1, &es);
        if (!es.es_len)
                goto insert_hole;

        /*
         * There's a delalloc extent in the hole, handle it if the delalloc
         * extent is in front of, behind and straddle the queried range.
         */
        if (lblk >= es.es_lblk + es.es_len) {
                /*
                 * The delalloc extent is in front of the queried range,
                 * find again from the queried start block.
                 */
                len -= lblk - hole_start;
                hole_start = lblk;
                goto again;
        } else if (in_range(lblk, es.es_lblk, es.es_len)) {
                /*
                 * The delalloc extent containing lblk, it must have been
                 * added after ext4_map_blocks() checked the extent status
                 * tree so we are not holding i_rwsem and delalloc info is
                 * only stabilized by i_data_sem we are going to release
                 * soon. Don't modify the extent status tree and report
                 * extent as a hole, just adjust the length to the delalloc
                 * extent's after lblk.
                 */
                len = es.es_lblk + es.es_len - lblk;
                return len;
        } else {
                /*
                 * The delalloc extent is partially or completely behind
                 * the queried range, update hole length until the
                 * beginning of the delalloc extent.
                 */
                len = min(es.es_lblk - hole_start, len);
        }

insert_hole:
        /* Put just found gap into cache to speed up subsequent requests */
        ext_debug(inode, " -> %u:%u\n", hole_start, len);
        ext4_es_cache_extent(inode, hole_start, len, ~0, EXTENT_STATUS_HOLE);

        /* Update hole_len to reflect hole size after lblk */
        if (hole_start != lblk)
                len -= lblk - hole_start;

        return len;
}

/*
 * Block allocation/map/preallocation routine for extents based files
 *
 *
 * Need to be called with
 * down_read(&EXT4_I(inode)->i_data_sem) if not allocating file system block
 * (ie, flags is zero). Otherwise down_write(&EXT4_I(inode)->i_data_sem)
 *
 * return > 0, number of blocks already mapped/allocated
 *          if flags doesn't contain EXT4_GET_BLOCKS_CREATE and these are pre-allocated blocks
 *              buffer head is unmapped
 *          otherwise blocks are mapped
 *
 * return = 0, if plain look up failed (blocks have not been allocated)
 *          buffer head is unmapped
 *
 * return < 0, error case.
 */
int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
                        struct ext4_map_blocks *map, int flags)
{
        struct ext4_ext_path *path = NULL;
        struct ext4_extent newex, *ex, ex2;
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
        ext4_fsblk_t newblock = 0, pblk;
        int err = 0, depth;
        unsigned int allocated = 0, offset = 0;
        unsigned int allocated_clusters = 0;
        struct ext4_allocation_request ar;
        ext4_lblk_t cluster_offset;

        ext_debug(inode, "blocks %u/%u requested\n", map->m_lblk, map->m_len);
        trace_ext4_ext_map_blocks_enter(inode, map->m_lblk, map->m_len, flags);

        /* find extent for this block */
        path = ext4_find_extent(inode, map->m_lblk, NULL, flags);
        if (IS_ERR(path)) {
                err = PTR_ERR(path);
                goto out;
        }

        depth = ext_depth(inode);

        /*
         * consistent leaf must not be empty;
         * this situation is possible, though, _during_ tree modification;
         * this is why assert can't be put in ext4_find_extent()
         */
        if (unlikely(path[depth].p_ext == NULL && depth != 0)) {
                EXT4_ERROR_INODE(inode, "bad extent address "
                                 "lblock: %lu, depth: %d pblock %lld",
                                 (unsigned long) map->m_lblk, depth,
                                 path[depth].p_block);
                err = -EFSCORRUPTED;
                goto out;
        }

        ex = path[depth].p_ext;
        if (ex) {
                ext4_lblk_t ee_block = le32_to_cpu(ex->ee_block);
                ext4_fsblk_t ee_start = ext4_ext_pblock(ex);
                unsigned short ee_len;


                /*
                 * unwritten extents are treated as holes, except that
                 * we split out initialized portions during a write.
                 */
                ee_len = ext4_ext_get_actual_len(ex);

                trace_ext4_ext_show_extent(inode, ee_block, ee_start, ee_len);

                /* if found extent covers block, simply return it */
                if (in_range(map->m_lblk, ee_block, ee_len)) {
                        newblock = map->m_lblk - ee_block + ee_start;
                        /* number of remaining blocks in the extent */
                        allocated = ee_len - (map->m_lblk - ee_block);
                        ext_debug(inode, "%u fit into %u:%d -> %llu\n",
                                  map->m_lblk, ee_block, ee_len, newblock);

                        /*
                         * If the extent is initialized check whether the
                         * caller wants to convert it to unwritten.
                         */
                        if ((!ext4_ext_is_unwritten(ex)) &&
                            (flags & EXT4_GET_BLOCKS_CONVERT_UNWRITTEN)) {
                                path = convert_initialized_extent(handle,
                                        inode, map, path, flags, &allocated);
                                if (IS_ERR(path))
                                        err = PTR_ERR(path);
                                goto out;
                        } else if (!ext4_ext_is_unwritten(ex)) {
                                map->m_flags |= EXT4_MAP_MAPPED;
                                map->m_pblk = newblock;
                                if (allocated > map->m_len)
                                        allocated = map->m_len;
                                map->m_len = allocated;
                                ext4_ext_show_leaf(inode, path);
                                goto out;
                        }

                        path = ext4_ext_handle_unwritten_extents(
                                handle, inode, map, path, flags,
                                &allocated, newblock);
                        if (IS_ERR(path))
                                err = PTR_ERR(path);
                        goto out;
                }
        }

        /*
         * requested block isn't allocated yet;
         * we couldn't try to create block if flags doesn't contain EXT4_GET_BLOCKS_CREATE
         */
        if ((flags & EXT4_GET_BLOCKS_CREATE) == 0) {
                ext4_lblk_t len;

                len = ext4_ext_determine_insert_hole(inode, path, map->m_lblk);

                map->m_pblk = 0;
                map->m_len = min_t(unsigned int, map->m_len, len);
                goto out;
        }

        /*
         * Okay, we need to do block allocation.
         */
        newex.ee_block = cpu_to_le32(map->m_lblk);
        cluster_offset = EXT4_LBLK_COFF(sbi, map->m_lblk);

        /*
         * If we are doing bigalloc, check to see if the extent returned
         * by ext4_find_extent() implies a cluster we can use.
         */
        if (cluster_offset && ex &&
            get_implied_cluster_alloc(inode->i_sb, map, ex, path)) {
                ar.len = allocated = map->m_len;
                newblock = map->m_pblk;
                goto got_allocated_blocks;
        }

        /* find neighbour allocated blocks */
        ar.lleft = map->m_lblk;
        err = ext4_ext_search_left(inode, path, &ar.lleft, &ar.pleft);
        if (err)
                goto out;
        ar.lright = map->m_lblk;
        err = ext4_ext_search_right(inode, path, &ar.lright, &ar.pright,
                                    &ex2, flags);
        if (err < 0)
                goto out;

        /* Check if the extent after searching to the right implies a
         * cluster we can use. */
        if ((sbi->s_cluster_ratio > 1) && err &&
            get_implied_cluster_alloc(inode->i_sb, map, &ex2, path)) {
                ar.len = allocated = map->m_len;
                newblock = map->m_pblk;
                err = 0;
                goto got_allocated_blocks;
        }

        /*
         * See if request is beyond maximum number of blocks we can have in
         * a single extent. For an initialized extent this limit is
         * EXT_INIT_MAX_LEN and for an unwritten extent this limit is
         * EXT_UNWRITTEN_MAX_LEN.
         */
        if (map->m_len > EXT_INIT_MAX_LEN &&
            !(flags & EXT4_GET_BLOCKS_UNWRIT_EXT))
                map->m_len = EXT_INIT_MAX_LEN;
        else if (map->m_len > EXT_UNWRITTEN_MAX_LEN &&
                 (flags & EXT4_GET_BLOCKS_UNWRIT_EXT))
                map->m_len = EXT_UNWRITTEN_MAX_LEN;

        /* Check if we can really insert (m_lblk)::(m_lblk + m_len) extent */
        newex.ee_len = cpu_to_le16(map->m_len);
        err = ext4_ext_check_overlap(sbi, inode, &newex, path);
        if (err)
                allocated = ext4_ext_get_actual_len(&newex);
        else
                allocated = map->m_len;

        /* allocate new block */
        ar.inode = inode;
        ar.goal = ext4_ext_find_goal(inode, path, map->m_lblk);
        ar.logical = map->m_lblk;
        /*
         * We calculate the offset from the beginning of the cluster
         * for the logical block number, since when we allocate a
         * physical cluster, the physical block should start at the
         * same offset from the beginning of the cluster.  This is
         * needed so that future calls to get_implied_cluster_alloc()
         * work correctly.
         */
        offset = EXT4_LBLK_COFF(sbi, map->m_lblk);
        ar.len = EXT4_NUM_B2C(sbi, offset+allocated);
        ar.goal -= offset;
        ar.logical -= offset;
        if (S_ISREG(inode->i_mode))
                ar.flags = EXT4_MB_HINT_DATA;
        else
                /* disable in-core preallocation for non-regular files */
                ar.flags = 0;
        if (flags & EXT4_GET_BLOCKS_NO_NORMALIZE)
                ar.flags |= EXT4_MB_HINT_NOPREALLOC;
        if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
                ar.flags |= EXT4_MB_DELALLOC_RESERVED;
        if (flags & EXT4_GET_BLOCKS_METADATA_NOFAIL)
                ar.flags |= EXT4_MB_USE_RESERVED;
        newblock = ext4_mb_new_blocks(handle, &ar, &err);
        if (!newblock)
                goto out;
        allocated_clusters = ar.len;
        ar.len = EXT4_C2B(sbi, ar.len) - offset;
        ext_debug(inode, "allocate new block: goal %llu, found %llu/%u, requested %u\n",
                  ar.goal, newblock, ar.len, allocated);
        if (ar.len > allocated)
                ar.len = allocated;

got_allocated_blocks:
        /* try to insert new extent into found leaf and return */
        pblk = newblock + offset;
        ext4_ext_store_pblock(&newex, pblk);
        newex.ee_len = cpu_to_le16(ar.len);
        /* Mark unwritten */
        if (flags & EXT4_GET_BLOCKS_UNWRIT_EXT) {
                ext4_ext_mark_unwritten(&newex);
                map->m_flags |= EXT4_MAP_UNWRITTEN;
        }

        path = ext4_ext_insert_extent(handle, inode, path, &newex, flags);
        if (IS_ERR(path)) {
                err = PTR_ERR(path);
                /*
                 * Gracefully handle out of space conditions. If the filesystem
                 * is inconsistent, we'll just leak allocated blocks to avoid
                 * causing even more damage.
                 */
                if (allocated_clusters && (err == -EDQUOT || err == -ENOSPC)) {
                        int fb_flags = 0;
                        /*
                         * free data blocks we just allocated.
                         * not a good idea to call discard here directly,
                         * but otherwise we'd need to call it every free().
                         */
                        ext4_discard_preallocations(inode);
                        if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
                                fb_flags = EXT4_FREE_BLOCKS_NO_QUOT_UPDATE;
                        ext4_free_blocks(handle, inode, NULL, newblock,
                                         EXT4_C2B(sbi, allocated_clusters),
                                         fb_flags);
                }
                goto out;
        }

        /*
         * Cache the extent and update transaction to commit on fdatasync only
         * when it is _not_ an unwritten extent.
         */
        if ((flags & EXT4_GET_BLOCKS_UNWRIT_EXT) == 0)
                ext4_update_inode_fsync_trans(handle, inode, 1);
        else
                ext4_update_inode_fsync_trans(handle, inode, 0);

        map->m_flags |= (EXT4_MAP_NEW | EXT4_MAP_MAPPED);
        map->m_pblk = pblk;
        map->m_len = ar.len;
        allocated = map->m_len;
        ext4_ext_show_leaf(inode, path);
out:
        /*
         * We never use EXT4_GET_BLOCKS_QUERY_LAST_IN_LEAF with CREATE flag.
         * So we know that the depth used here is correct, since there was no
         * block allocation done if EXT4_GET_BLOCKS_QUERY_LAST_IN_LEAF is set.
         * If tomorrow we start using this QUERY flag with CREATE, then we will
         * need to re-calculate the depth as it might have changed due to block
         * allocation.
         */
        if (flags & EXT4_GET_BLOCKS_QUERY_LAST_IN_LEAF) {
                WARN_ON_ONCE(flags & EXT4_GET_BLOCKS_CREATE);
                if (!err && ex && (ex == EXT_LAST_EXTENT(path[depth].p_hdr)))
                        map->m_flags |= EXT4_MAP_QUERY_LAST_IN_LEAF;
        }

        ext4_free_ext_path(path);

        trace_ext4_ext_map_blocks_exit(inode, flags, map,
                                       err ? err : allocated);
        return err ? err : allocated;
}

int ext4_ext_truncate(handle_t *handle, struct inode *inode)
{
        struct super_block *sb = inode->i_sb;
        ext4_lblk_t last_block;
        int err = 0;

        /*
         * TODO: optimization is possible here.
         * Probably we need not scan at all,
         * because page truncation is enough.
         */

        /* we have to know where to truncate from in crash case */
        EXT4_I(inode)->i_disksize = inode->i_size;
        err = ext4_mark_inode_dirty(handle, inode);
        if (err)
                return err;

        last_block = (inode->i_size + sb->s_blocksize - 1)
                        >> EXT4_BLOCK_SIZE_BITS(sb);
        ext4_es_remove_extent(inode, last_block, EXT_MAX_BLOCKS - last_block);

retry_remove_space:
        err = ext4_ext_remove_space(inode, last_block, EXT_MAX_BLOCKS - 1);
        if (err == -ENOMEM) {
                memalloc_retry_wait(GFP_ATOMIC);
                goto retry_remove_space;
        }
        return err;
}

static int ext4_alloc_file_blocks(struct file *file, ext4_lblk_t offset,
                                  ext4_lblk_t len, loff_t new_size,
                                  int flags)
{
        struct inode *inode = file_inode(file);
        handle_t *handle;
        int ret = 0, ret2 = 0, ret3 = 0;
        int retries = 0;
        int depth = 0;
        struct ext4_map_blocks map;
        unsigned int credits;
        loff_t epos, old_size = i_size_read(inode);
        unsigned int blkbits = inode->i_blkbits;
        bool alloc_zero = false;

        BUG_ON(!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS));
        map.m_lblk = offset;
        map.m_len = len;
        /*
         * Don't normalize the request if it can fit in one extent so
         * that it doesn't get unnecessarily split into multiple
         * extents.
         */
        if (len <= EXT_UNWRITTEN_MAX_LEN)
                flags |= EXT4_GET_BLOCKS_NO_NORMALIZE;

        /*
         * Do the actual write zero during a running journal transaction
         * costs a lot. First allocate an unwritten extent and then
         * convert it to written after zeroing it out.
         */
        if (flags & EXT4_GET_BLOCKS_ZERO) {
                flags &= ~EXT4_GET_BLOCKS_ZERO;
                flags |= EXT4_GET_BLOCKS_UNWRIT_EXT;
                alloc_zero = true;
        }

        /*
         * credits to insert 1 extent into extent tree
         */
        credits = ext4_chunk_trans_blocks(inode, len);
        depth = ext_depth(inode);

retry:
        while (len) {
                /*
                 * Recalculate credits when extent tree depth changes.
                 */
                if (depth != ext_depth(inode)) {
                        credits = ext4_chunk_trans_blocks(inode, len);
                        depth = ext_depth(inode);
                }

                handle = ext4_journal_start(inode, EXT4_HT_MAP_BLOCKS,
                                            credits);
                if (IS_ERR(handle)) {
                        ret = PTR_ERR(handle);
                        break;
                }
                ret = ext4_map_blocks(handle, inode, &map, flags);
                if (ret <= 0) {
                        ext4_debug("inode #%lu: block %u: len %u: "
                                   "ext4_ext_map_blocks returned %d",
                                   inode->i_ino, map.m_lblk,
                                   map.m_len, ret);
                        ext4_mark_inode_dirty(handle, inode);
                        ext4_journal_stop(handle);
                        break;
                }
                /*
                 * allow a full retry cycle for any remaining allocations
                 */
                retries = 0;
                epos = EXT4_LBLK_TO_B(inode, map.m_lblk + ret);
                inode_set_ctime_current(inode);
                if (new_size) {
                        if (epos > new_size)
                                epos = new_size;
                        if (ext4_update_inode_size(inode, epos) & 0x1)
                                inode_set_mtime_to_ts(inode,
                                                      inode_get_ctime(inode));
                        if (epos > old_size) {
                                pagecache_isize_extended(inode, old_size, epos);
                                ext4_zero_partial_blocks(handle, inode,
                                                     old_size, epos - old_size);
                        }
                }
                ret2 = ext4_mark_inode_dirty(handle, inode);
                ext4_update_inode_fsync_trans(handle, inode, 1);
                ret3 = ext4_journal_stop(handle);
                ret2 = ret3 ? ret3 : ret2;
                if (unlikely(ret2))
                        break;

                if (alloc_zero &&
                    (map.m_flags & (EXT4_MAP_MAPPED | EXT4_MAP_UNWRITTEN))) {
                        ret2 = ext4_issue_zeroout(inode, map.m_lblk, map.m_pblk,
                                                  map.m_len);
                        if (likely(!ret2))
                                ret2 = ext4_convert_unwritten_extents(NULL,
                                        inode, (loff_t)map.m_lblk << blkbits,
                                        (loff_t)map.m_len << blkbits);
                        if (ret2)
                                break;
                }

                map.m_lblk += ret;
                map.m_len = len = len - ret;
        }
        if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
                goto retry;

        return ret > 0 ? ret2 : ret;
}

static int ext4_collapse_range(struct file *file, loff_t offset, loff_t len);

static int ext4_insert_range(struct file *file, loff_t offset, loff_t len);

static long ext4_zero_range(struct file *file, loff_t offset,
                            loff_t len, int mode)
{
        struct inode *inode = file_inode(file);
        handle_t *handle = NULL;
        loff_t new_size = 0;
        loff_t end = offset + len;
        ext4_lblk_t start_lblk, end_lblk;
        unsigned int blocksize = i_blocksize(inode);
        unsigned int blkbits = inode->i_blkbits;
        int ret, flags, credits;

        trace_ext4_zero_range(inode, offset, len, mode);
        WARN_ON_ONCE(!inode_is_locked(inode));

        /* Indirect files do not support unwritten extents */
        if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
                return -EOPNOTSUPP;

        if (!(mode & FALLOC_FL_KEEP_SIZE) &&
            (end > inode->i_size || end > EXT4_I(inode)->i_disksize)) {
                new_size = end;
                ret = inode_newsize_ok(inode, new_size);
                if (ret)
                        return ret;
        }

        flags = EXT4_GET_BLOCKS_CREATE_UNWRIT_EXT;
        /* Preallocate the range including the unaligned edges */
        if (!IS_ALIGNED(offset | end, blocksize)) {
                ext4_lblk_t alloc_lblk = offset >> blkbits;
                ext4_lblk_t len_lblk = EXT4_MAX_BLOCKS(len, offset, blkbits);

                ret = ext4_alloc_file_blocks(file, alloc_lblk, len_lblk,
                                             new_size, flags);
                if (ret)
                        return ret;
        }

        ret = ext4_update_disksize_before_punch(inode, offset, len);
        if (ret)
                return ret;

        /* Now release the pages and zero block aligned part of pages */
        ret = ext4_truncate_page_cache_block_range(inode, offset, end);
        if (ret)
                return ret;

        /* Zero range excluding the unaligned edges */
        start_lblk = EXT4_B_TO_LBLK(inode, offset);
        end_lblk = end >> blkbits;
        if (end_lblk > start_lblk) {
                ext4_lblk_t zero_blks = end_lblk - start_lblk;

                if (mode & FALLOC_FL_WRITE_ZEROES)
                        flags = EXT4_GET_BLOCKS_CREATE_ZERO | EXT4_EX_NOCACHE;
                else
                        flags |= (EXT4_GET_BLOCKS_CONVERT_UNWRITTEN |
                                  EXT4_EX_NOCACHE);
                ret = ext4_alloc_file_blocks(file, start_lblk, zero_blks,
                                             new_size, flags);
                if (ret)
                        return ret;
        }
        /* Finish zeroing out if it doesn't contain partial block */
        if (IS_ALIGNED(offset | end, blocksize))
                return ret;

        /*
         * In worst case we have to writeout two nonadjacent unwritten
         * blocks and update the inode
         */
        credits = (2 * ext4_ext_index_trans_blocks(inode, 2)) + 1;
        if (ext4_should_journal_data(inode))
                credits += 2;
        handle = ext4_journal_start(inode, EXT4_HT_MISC, credits);
        if (IS_ERR(handle)) {
                ret = PTR_ERR(handle);
                ext4_std_error(inode->i_sb, ret);
                return ret;
        }

        /* Zero out partial block at the edges of the range */
        ret = ext4_zero_partial_blocks(handle, inode, offset, len);
        if (ret)
                goto out_handle;

        if (new_size)
                ext4_update_inode_size(inode, new_size);
        ret = ext4_mark_inode_dirty(handle, inode);
        if (unlikely(ret))
                goto out_handle;

        ext4_update_inode_fsync_trans(handle, inode, 1);
        if (file->f_flags & O_SYNC)
                ext4_handle_sync(handle);

out_handle:
        ext4_journal_stop(handle);
        return ret;
}

static long ext4_do_fallocate(struct file *file, loff_t offset,
                              loff_t len, int mode)
{
        struct inode *inode = file_inode(file);
        loff_t end = offset + len;
        loff_t new_size = 0;
        ext4_lblk_t start_lblk, len_lblk;
        int ret;

        trace_ext4_fallocate_enter(inode, offset, len, mode);
        WARN_ON_ONCE(!inode_is_locked(inode));

        start_lblk = offset >> inode->i_blkbits;
        len_lblk = EXT4_MAX_BLOCKS(len, offset, inode->i_blkbits);

        /* We only support preallocation for extent-based files only. */
        if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
                ret = -EOPNOTSUPP;
                goto out;
        }

        if (!(mode & FALLOC_FL_KEEP_SIZE) &&
            (end > inode->i_size || end > EXT4_I(inode)->i_disksize)) {
                new_size = end;
                ret = inode_newsize_ok(inode, new_size);
                if (ret)
                        goto out;
        }

        ret = ext4_alloc_file_blocks(file, start_lblk, len_lblk, new_size,
                                     EXT4_GET_BLOCKS_CREATE_UNWRIT_EXT);
        if (ret)
                goto out;

        if (file->f_flags & O_SYNC && EXT4_SB(inode->i_sb)->s_journal) {
                ret = ext4_fc_commit(EXT4_SB(inode->i_sb)->s_journal,
                                        EXT4_I(inode)->i_sync_tid);
        }
out:
        trace_ext4_fallocate_exit(inode, offset, len_lblk, ret);
        return ret;
}

/*
 * preallocate space for a file. This implements ext4's fallocate file
 * operation, which gets called from sys_fallocate system call.
 * For block-mapped files, posix_fallocate should fall back to the method
 * of writing zeroes to the required new blocks (the same behavior which is
 * expected for file systems which do not support fallocate() system call).
 */
long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
{
        struct inode *inode = file_inode(file);
        struct address_space *mapping = file->f_mapping;
        int ret;

        /*
         * Encrypted inodes can't handle collapse range or insert
         * range since we would need to re-encrypt blocks with a
         * different IV or XTS tweak (which are based on the logical
         * block number).
         */
        if (IS_ENCRYPTED(inode) &&
            (mode & (FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_INSERT_RANGE)))
                return -EOPNOTSUPP;
        /*
         * Don't allow writing zeroes if the underlying device does not
         * enable the unmap write zeroes operation.
         */
        if ((mode & FALLOC_FL_WRITE_ZEROES) &&
            !bdev_write_zeroes_unmap_sectors(inode->i_sb->s_bdev))
                return -EOPNOTSUPP;

        /* Return error if mode is not supported */
        if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |
                     FALLOC_FL_ZERO_RANGE | FALLOC_FL_COLLAPSE_RANGE |
                     FALLOC_FL_INSERT_RANGE | FALLOC_FL_WRITE_ZEROES))
                return -EOPNOTSUPP;

        inode_lock(inode);
        ret = ext4_convert_inline_data(inode);
        if (ret)
                goto out_inode_lock;

        /* Wait all existing dio workers, newcomers will block on i_rwsem */
        inode_dio_wait(inode);

        ret = file_modified(file);
        if (ret)
                goto out_inode_lock;

        if ((mode & FALLOC_FL_MODE_MASK) == FALLOC_FL_ALLOCATE_RANGE) {
                ret = ext4_do_fallocate(file, offset, len, mode);
                goto out_inode_lock;
        }

        /*
         * Follow-up operations will drop page cache, hold invalidate lock
         * to prevent page faults from reinstantiating pages we have
         * released from page cache.
         */
        filemap_invalidate_lock(mapping);

        ret = ext4_break_layouts(inode);
        if (ret)
                goto out_invalidate_lock;

        switch (mode & FALLOC_FL_MODE_MASK) {
        case FALLOC_FL_PUNCH_HOLE:
                ret = ext4_punch_hole(file, offset, len);
                break;
        case FALLOC_FL_COLLAPSE_RANGE:
                ret = ext4_collapse_range(file, offset, len);
                break;
        case FALLOC_FL_INSERT_RANGE:
                ret = ext4_insert_range(file, offset, len);
                break;
        case FALLOC_FL_ZERO_RANGE:
        case FALLOC_FL_WRITE_ZEROES:
                ret = ext4_zero_range(file, offset, len, mode);
                break;
        default:
                ret = -EOPNOTSUPP;
        }

out_invalidate_lock:
        filemap_invalidate_unlock(mapping);
out_inode_lock:
        inode_unlock(inode);
        return ret;
}

/*
 * This function converts a range of blocks to written extents. The caller of
 * this function will pass the start offset and the size. all unwritten extents
 * within this range will be converted to written extents.
 *
 * This function is called from the direct IO end io call back function for
 * atomic writes, to convert the unwritten extents after IO is completed.
 *
 * Note that the requirement for atomic writes is that all conversion should
 * happen atomically in a single fs journal transaction. We mainly only allocate
 * unwritten extents either on a hole on a pre-exiting unwritten extent range in
 * ext4_map_blocks_atomic_write(). The only case where we can have multiple
 * unwritten extents in a range [offset, offset+len) is when there is a split
 * unwritten extent between two leaf nodes which was cached in extent status
 * cache during ext4_iomap_alloc() time. That will allow
 * ext4_map_blocks_atomic_write() to return the unwritten extent range w/o going
 * into the slow path. That means we might need a loop for conversion of this
 * unwritten extent split across leaf block within a single journal transaction.
 * Split extents across leaf nodes is a rare case, but let's still handle that
 * to meet the requirements of multi-fsblock atomic writes.
 *
 * Returns 0 on success.
 */
int ext4_convert_unwritten_extents_atomic(handle_t *handle, struct inode *inode,
                                          loff_t offset, ssize_t len)
{
        unsigned int max_blocks;
        int ret = 0, ret2 = 0, ret3 = 0;
        struct ext4_map_blocks map;
        unsigned int blkbits = inode->i_blkbits;
        unsigned int credits = 0;
        int flags = EXT4_GET_BLOCKS_IO_CONVERT_EXT | EXT4_EX_NOCACHE;

        map.m_lblk = offset >> blkbits;
        max_blocks = EXT4_MAX_BLOCKS(len, offset, blkbits);

        if (!handle) {
                /*
                 * TODO: An optimization can be added later by having an extent
                 * status flag e.g. EXTENT_STATUS_SPLIT_LEAF. If we query that
                 * it can tell if the extent in the cache is a split extent.
                 * But for now let's assume pextents as 2 always.
                 */
                credits = ext4_meta_trans_blocks(inode, max_blocks, 2);
        }

        if (credits) {
                handle = ext4_journal_start(inode, EXT4_HT_MAP_BLOCKS, credits);
                if (IS_ERR(handle)) {
                        ret = PTR_ERR(handle);
                        return ret;
                }
        }

        while (ret >= 0 && ret < max_blocks) {
                map.m_lblk += ret;
                map.m_len = (max_blocks -= ret);
                ret = ext4_map_blocks(handle, inode, &map, flags);
                if (ret != max_blocks)
                        ext4_msg(inode->i_sb, KERN_INFO,
                                     "inode #%lu: block %u: len %u: "
                                     "split block mapping found for atomic write, "
                                     "ret = %d",
                                     inode->i_ino, map.m_lblk,
                                     map.m_len, ret);
                if (ret <= 0)
                        break;
        }

        ret2 = ext4_mark_inode_dirty(handle, inode);

        if (credits) {
                ret3 = ext4_journal_stop(handle);
                if (unlikely(ret3))
                        ret2 = ret3;
        }

        if (ret <= 0 || ret2)
                ext4_warning(inode->i_sb,
                             "inode #%lu: block %u: len %u: "
                             "returned %d or %d",
                             inode->i_ino, map.m_lblk,
                             map.m_len, ret, ret2);

        return ret > 0 ? ret2 : ret;
}

/*
 * This function convert a range of blocks to written extents
 * The caller of this function will pass the start offset and the size.
 * all unwritten extents within this range will be converted to
 * written extents.
 *
 * This function is called from the direct IO end io call back
 * function, to convert the fallocated extents after IO is completed.
 * Returns 0 on success.
 */
int ext4_convert_unwritten_extents(handle_t *handle, struct inode *inode,
                                   loff_t offset, ssize_t len)
{
        unsigned int max_blocks;
        int ret = 0, ret2 = 0, ret3 = 0;
        struct ext4_map_blocks map;
        unsigned int blkbits = inode->i_blkbits;
        unsigned int credits = 0;

        map.m_lblk = offset >> blkbits;
        max_blocks = EXT4_MAX_BLOCKS(len, offset, blkbits);

        if (!handle) {
                /*
                 * credits to insert 1 extent into extent tree
                 */
                credits = ext4_chunk_trans_blocks(inode, max_blocks);
        }
        while (ret >= 0 && ret < max_blocks) {
                map.m_lblk += ret;
                map.m_len = (max_blocks -= ret);
                if (credits) {
                        handle = ext4_journal_start(inode, EXT4_HT_MAP_BLOCKS,
                                                    credits);
                        if (IS_ERR(handle)) {
                                ret = PTR_ERR(handle);
                                break;
                        }
                }
                /*
                 * Do not cache any unrelated extents, as it does not hold the
                 * i_rwsem or invalidate_lock, which could corrupt the extent
                 * status tree.
                 */
                ret = ext4_map_blocks(handle, inode, &map,
                                      EXT4_GET_BLOCKS_IO_CONVERT_EXT |
                                      EXT4_EX_NOCACHE);
                if (ret <= 0)
                        ext4_warning(inode->i_sb,
                                     "inode #%lu: block %u: len %u: "
                                     "ext4_ext_map_blocks returned %d",
                                     inode->i_ino, map.m_lblk,
                                     map.m_len, ret);
                ret2 = ext4_mark_inode_dirty(handle, inode);
                if (credits) {
                        ret3 = ext4_journal_stop(handle);
                        if (unlikely(ret3))
                                ret2 = ret3;
                }

                if (ret <= 0 || ret2)
                        break;
        }
        return ret > 0 ? ret2 : ret;
}

int ext4_convert_unwritten_io_end_vec(handle_t *handle, ext4_io_end_t *io_end)
{
        int ret = 0, err = 0;
        struct ext4_io_end_vec *io_end_vec;

        /*
         * This is somewhat ugly but the idea is clear: When transaction is
         * reserved, everything goes into it. Otherwise we rather start several
         * smaller transactions for conversion of each extent separately.
         */
        if (handle) {
                handle = ext4_journal_start_reserved(handle,
                                                     EXT4_HT_EXT_CONVERT);
                if (IS_ERR(handle))
                        return PTR_ERR(handle);
        }

        list_for_each_entry(io_end_vec, &io_end->list_vec, list) {
                ret = ext4_convert_unwritten_extents(handle, io_end->inode,
                                                     io_end_vec->offset,
                                                     io_end_vec->size);
                if (ret)
                        break;
        }

        if (handle)
                err = ext4_journal_stop(handle);

        return ret < 0 ? ret : err;
}

static int ext4_iomap_xattr_fiemap(struct inode *inode, struct iomap *iomap)
{
        __u64 physical = 0;
        __u64 length = 0;
        int blockbits = inode->i_sb->s_blocksize_bits;
        int error = 0;
        u16 iomap_type;

        /* in-inode? */
        if (ext4_test_inode_state(inode, EXT4_STATE_XATTR)) {
                struct ext4_iloc iloc;
                int offset;     /* offset of xattr in inode */

                error = ext4_get_inode_loc(inode, &iloc);
                if (error)
                        return error;
                physical = (__u64)iloc.bh->b_blocknr << blockbits;
                offset = EXT4_GOOD_OLD_INODE_SIZE +
                                EXT4_I(inode)->i_extra_isize;
                physical += offset;
                length = EXT4_SB(inode->i_sb)->s_inode_size - offset;
                brelse(iloc.bh);
                iomap_type = IOMAP_INLINE;
        } else if (EXT4_I(inode)->i_file_acl) { /* external block */
                physical = (__u64)EXT4_I(inode)->i_file_acl << blockbits;
                length = inode->i_sb->s_blocksize;
                iomap_type = IOMAP_MAPPED;
        } else {
                /* no in-inode or external block for xattr, so return -ENOENT */
                error = -ENOENT;
                goto out;
        }

        iomap->addr = physical;
        iomap->offset = 0;
        iomap->length = length;
        iomap->type = iomap_type;
        iomap->flags = 0;
out:
        return error;
}

static int ext4_iomap_xattr_begin(struct inode *inode, loff_t offset,
                                  loff_t length, unsigned flags,
                                  struct iomap *iomap, struct iomap *srcmap)
{
        int error;

        error = ext4_iomap_xattr_fiemap(inode, iomap);
        if (error == 0 && (offset >= iomap->length))
                error = -ENOENT;
        return error;
}

static const struct iomap_ops ext4_iomap_xattr_ops = {
        .iomap_begin            = ext4_iomap_xattr_begin,
};

static int ext4_fiemap_check_ranges(struct inode *inode, u64 start, u64 *len)
{
        u64 maxbytes = ext4_get_maxbytes(inode);

        if (*len == 0)
                return -EINVAL;
        if (start > maxbytes)
                return -EFBIG;

        /*
         * Shrink request scope to what the fs can actually handle.
         */
        if (*len > maxbytes || (maxbytes - *len) < start)
                *len = maxbytes - start;
        return 0;
}

int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
                u64 start, u64 len)
{
        int error = 0;

        inode_lock_shared(inode);
        if (fieinfo->fi_flags & FIEMAP_FLAG_CACHE) {
                error = ext4_ext_precache(inode);
                if (error)
                        goto unlock;
                fieinfo->fi_flags &= ~FIEMAP_FLAG_CACHE;
        }

        /*
         * For bitmap files the maximum size limit could be smaller than
         * s_maxbytes, so check len here manually instead of just relying on the
         * generic check.
         */
        error = ext4_fiemap_check_ranges(inode, start, &len);
        if (error)
                goto unlock;

        if (fieinfo->fi_flags & FIEMAP_FLAG_XATTR) {
                fieinfo->fi_flags &= ~FIEMAP_FLAG_XATTR;
                error = iomap_fiemap(inode, fieinfo, start, len,
                                     &ext4_iomap_xattr_ops);
        } else {
                error = iomap_fiemap(inode, fieinfo, start, len,
                                     &ext4_iomap_report_ops);
        }
unlock:
        inode_unlock_shared(inode);
        return error;
}

int ext4_get_es_cache(struct inode *inode, struct fiemap_extent_info *fieinfo,
                      __u64 start, __u64 len)
{
        ext4_lblk_t start_blk, len_blks;
        __u64 last_blk;
        int error = 0;

        if (ext4_has_inline_data(inode)) {
                int has_inline;

                down_read(&EXT4_I(inode)->xattr_sem);
                has_inline = ext4_has_inline_data(inode);
                up_read(&EXT4_I(inode)->xattr_sem);
                if (has_inline)
                        return 0;
        }

        if (fieinfo->fi_flags & FIEMAP_FLAG_CACHE) {
                inode_lock_shared(inode);
                error = ext4_ext_precache(inode);
                inode_unlock_shared(inode);
                if (error)
                        return error;
                fieinfo->fi_flags &= ~FIEMAP_FLAG_CACHE;
        }

        error = fiemap_prep(inode, fieinfo, start, &len, 0);
        if (error)
                return error;

        error = ext4_fiemap_check_ranges(inode, start, &len);
        if (error)
                return error;

        start_blk = start >> inode->i_sb->s_blocksize_bits;
        last_blk = (start + len - 1) >> inode->i_sb->s_blocksize_bits;
        if (last_blk >= EXT_MAX_BLOCKS)
                last_blk = EXT_MAX_BLOCKS-1;
        len_blks = ((ext4_lblk_t) last_blk) - start_blk + 1;

        /*
         * Walk the extent tree gathering extent information
         * and pushing extents back to the user.
         */
        return ext4_fill_es_cache_info(inode, start_blk, len_blks, fieinfo);
}

/*
 * ext4_ext_shift_path_extents:
 * Shift the extents of a path structure lying between path[depth].p_ext
 * and EXT_LAST_EXTENT(path[depth].p_hdr), by @shift blocks. @SHIFT tells
 * if it is right shift or left shift operation.
 */
static int
ext4_ext_shift_path_extents(struct ext4_ext_path *path, ext4_lblk_t shift,
                            struct inode *inode, handle_t *handle,
                            enum SHIFT_DIRECTION SHIFT)
{
        int depth, err = 0;
        struct ext4_extent *ex_start, *ex_last;
        bool update = false;
        int credits, restart_credits;
        depth = path->p_depth;

        while (depth >= 0) {
                if (depth == path->p_depth) {
                        ex_start = path[depth].p_ext;
                        if (!ex_start)
                                return -EFSCORRUPTED;

                        ex_last = EXT_LAST_EXTENT(path[depth].p_hdr);
                        /* leaf + sb + inode */
                        credits = 3;
                        if (ex_start == EXT_FIRST_EXTENT(path[depth].p_hdr)) {
                                update = true;
                                /* extent tree + sb + inode */
                                credits = depth + 2;
                        }

                        restart_credits = ext4_chunk_trans_extent(inode, 0);
                        err = ext4_datasem_ensure_credits(handle, inode, credits,
                                        restart_credits, 0);
                        if (err) {
                                if (err > 0)
                                        err = -EAGAIN;
                                goto out;
                        }

                        err = ext4_ext_get_access(handle, inode, path + depth);
                        if (err)
                                goto out;

                        while (ex_start <= ex_last) {
                                if (SHIFT == SHIFT_LEFT) {
                                        le32_add_cpu(&ex_start->ee_block,
                                                -shift);
                                        /* Try to merge to the left. */
                                        if ((ex_start >
                                            EXT_FIRST_EXTENT(path[depth].p_hdr))
                                            &&
                                            ext4_ext_try_to_merge_right(inode,
                                            path, ex_start - 1))
                                                ex_last--;
                                        else
                                                ex_start++;
                                } else {
                                        le32_add_cpu(&ex_last->ee_block, shift);
                                        ext4_ext_try_to_merge_right(inode, path,
                                                ex_last);
                                        ex_last--;
                                }
                        }
                        err = ext4_ext_dirty(handle, inode, path + depth);
                        if (err)
                                goto out;

                        if (--depth < 0 || !update)
                                break;
                }

                /* Update index too */
                err = ext4_ext_get_access(handle, inode, path + depth);
                if (err)
                        goto out;

                if (SHIFT == SHIFT_LEFT)
                        le32_add_cpu(&path[depth].p_idx->ei_block, -shift);
                else
                        le32_add_cpu(&path[depth].p_idx->ei_block, shift);
                err = ext4_ext_dirty(handle, inode, path + depth);
                if (err)
                        goto out;

                /* we are done if current index is not a starting index */
                if (path[depth].p_idx != EXT_FIRST_INDEX(path[depth].p_hdr))
                        break;

                depth--;
        }

out:
        return err;
}

/*
 * ext4_ext_shift_extents:
 * All the extents which lies in the range from @start to the last allocated
 * block for the @inode are shifted either towards left or right (depending
 * upon @SHIFT) by @shift blocks.
 * On success, 0 is returned, error otherwise.
 */
static int
ext4_ext_shift_extents(struct inode *inode, handle_t *handle,
                       ext4_lblk_t start, ext4_lblk_t shift,
                       enum SHIFT_DIRECTION SHIFT)
{
        struct ext4_ext_path *path;
        int ret = 0, depth;
        struct ext4_extent *extent;
        ext4_lblk_t stop, *iterator, ex_start, ex_end;
        ext4_lblk_t tmp = EXT_MAX_BLOCKS;

        /* Let path point to the last extent */
        path = ext4_find_extent(inode, EXT_MAX_BLOCKS - 1, NULL,
                                EXT4_EX_NOCACHE);
        if (IS_ERR(path))
                return PTR_ERR(path);

        depth = path->p_depth;
        extent = path[depth].p_ext;
        if (!extent)
                goto out;

        stop = le32_to_cpu(extent->ee_block);

       /*
        * For left shifts, make sure the hole on the left is big enough to
        * accommodate the shift.  For right shifts, make sure the last extent
        * won't be shifted beyond EXT_MAX_BLOCKS.
        */
        if (SHIFT == SHIFT_LEFT) {
                path = ext4_find_extent(inode, start - 1, path,
                                        EXT4_EX_NOCACHE);
                if (IS_ERR(path))
                        return PTR_ERR(path);
                depth = path->p_depth;
                extent =  path[depth].p_ext;
                if (extent) {
                        ex_start = le32_to_cpu(extent->ee_block);
                        ex_end = le32_to_cpu(extent->ee_block) +
                                ext4_ext_get_actual_len(extent);
                } else {
                        ex_start = 0;
                        ex_end = 0;
                }

                if ((start == ex_start && shift > ex_start) ||
                    (shift > start - ex_end)) {
                        ret = -EINVAL;
                        goto out;
                }
        } else {
                if (shift > EXT_MAX_BLOCKS -
                    (stop + ext4_ext_get_actual_len(extent))) {
                        ret = -EINVAL;
                        goto out;
                }
        }

        /*
         * In case of left shift, iterator points to start and it is increased
         * till we reach stop. In case of right shift, iterator points to stop
         * and it is decreased till we reach start.
         */
again:
        ret = 0;
        if (SHIFT == SHIFT_LEFT)
                iterator = &start;
        else
                iterator = &stop;

        if (tmp != EXT_MAX_BLOCKS)
                *iterator = tmp;

        /*
         * Its safe to start updating extents.  Start and stop are unsigned, so
         * in case of right shift if extent with 0 block is reached, iterator
         * becomes NULL to indicate the end of the loop.
         */
        while (iterator && start <= stop) {
                path = ext4_find_extent(inode, *iterator, path,
                                        EXT4_EX_NOCACHE);
                if (IS_ERR(path))
                        return PTR_ERR(path);
                depth = path->p_depth;
                extent = path[depth].p_ext;
                if (!extent) {
                        EXT4_ERROR_INODE(inode, "unexpected hole at %lu",
                                         (unsigned long) *iterator);
                        ret = -EFSCORRUPTED;
                        goto out;
                }
                if (SHIFT == SHIFT_LEFT && *iterator >
                    le32_to_cpu(extent->ee_block)) {
                        /* Hole, move to the next extent */
                        if (extent < EXT_LAST_EXTENT(path[depth].p_hdr)) {
                                path[depth].p_ext++;
                        } else {
                                *iterator = ext4_ext_next_allocated_block(path);
                                continue;
                        }
                }

                tmp = *iterator;
                if (SHIFT == SHIFT_LEFT) {
                        extent = EXT_LAST_EXTENT(path[depth].p_hdr);
                        *iterator = le32_to_cpu(extent->ee_block) +
                                        ext4_ext_get_actual_len(extent);
                } else {
                        extent = EXT_FIRST_EXTENT(path[depth].p_hdr);
                        if (le32_to_cpu(extent->ee_block) > start)
                                *iterator = le32_to_cpu(extent->ee_block) - 1;
                        else if (le32_to_cpu(extent->ee_block) == start)
                                iterator = NULL;
                        else {
                                extent = EXT_LAST_EXTENT(path[depth].p_hdr);
                                while (le32_to_cpu(extent->ee_block) >= start)
                                        extent--;

                                if (extent == EXT_LAST_EXTENT(path[depth].p_hdr))
                                        break;

                                extent++;
                                iterator = NULL;
                        }
                        path[depth].p_ext = extent;
                }
                ret = ext4_ext_shift_path_extents(path, shift, inode,
                                handle, SHIFT);
                /* iterator can be NULL which means we should break */
                if (ret == -EAGAIN)
                        goto again;
                if (ret)
                        break;
        }
out:
        ext4_free_ext_path(path);
        return ret;
}

/*
 * ext4_collapse_range:
 * This implements the fallocate's collapse range functionality for ext4
 * Returns: 0 and non-zero on error.
 */
static int ext4_collapse_range(struct file *file, loff_t offset, loff_t len)
{
        struct inode *inode = file_inode(file);
        struct super_block *sb = inode->i_sb;
        struct address_space *mapping = inode->i_mapping;
        loff_t end = offset + len;
        ext4_lblk_t start_lblk, end_lblk;
        handle_t *handle;
        unsigned int credits;
        loff_t start, new_size;
        int ret;

        trace_ext4_collapse_range(inode, offset, len);
        WARN_ON_ONCE(!inode_is_locked(inode));

        /* Currently just for extent based files */
        if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
                return -EOPNOTSUPP;
        /* Collapse range works only on fs cluster size aligned regions. */
        if (!IS_ALIGNED(offset | len, EXT4_CLUSTER_SIZE(sb)))
                return -EINVAL;
        /*
         * There is no need to overlap collapse range with EOF, in which case
         * it is effectively a truncate operation
         */
        if (end >= inode->i_size)
                return -EINVAL;

        /*
         * Write tail of the last page before removed range and data that
         * will be shifted since they will get removed from the page cache
         * below. We are also protected from pages becoming dirty by
         * i_rwsem and invalidate_lock.
         * Need to round down offset to be aligned with page size boundary
         * for page size > block size.
         */
        start = round_down(offset, PAGE_SIZE);
        ret = filemap_write_and_wait_range(mapping, start, offset);
        if (!ret)
                ret = filemap_write_and_wait_range(mapping, end, LLONG_MAX);
        if (ret)
                return ret;

        truncate_pagecache(inode, start);

        credits = ext4_chunk_trans_extent(inode, 0);
        handle = ext4_journal_start(inode, EXT4_HT_TRUNCATE, credits);
        if (IS_ERR(handle))
                return PTR_ERR(handle);

        ext4_fc_mark_ineligible(sb, EXT4_FC_REASON_FALLOC_RANGE, handle);

        start_lblk = offset >> inode->i_blkbits;
        end_lblk = (offset + len) >> inode->i_blkbits;

        ext4_check_map_extents_env(inode);

        down_write(&EXT4_I(inode)->i_data_sem);
        ext4_discard_preallocations(inode);
        ext4_es_remove_extent(inode, start_lblk, EXT_MAX_BLOCKS - start_lblk);

        ret = ext4_ext_remove_space(inode, start_lblk, end_lblk - 1);
        if (ret) {
                up_write(&EXT4_I(inode)->i_data_sem);
                goto out_handle;
        }
        ext4_discard_preallocations(inode);

        ret = ext4_ext_shift_extents(inode, handle, end_lblk,
                                     end_lblk - start_lblk, SHIFT_LEFT);
        if (ret) {
                up_write(&EXT4_I(inode)->i_data_sem);
                goto out_handle;
        }

        new_size = inode->i_size - len;
        i_size_write(inode, new_size);
        EXT4_I(inode)->i_disksize = new_size;

        up_write(&EXT4_I(inode)->i_data_sem);
        ret = ext4_mark_inode_dirty(handle, inode);
        if (ret)
                goto out_handle;

        ext4_update_inode_fsync_trans(handle, inode, 1);
        if (IS_SYNC(inode))
                ext4_handle_sync(handle);

out_handle:
        ext4_journal_stop(handle);
        return ret;
}

/*
 * ext4_insert_range:
 * This function implements the FALLOC_FL_INSERT_RANGE flag of fallocate.
 * The data blocks starting from @offset to the EOF are shifted by @len
 * towards right to create a hole in the @inode. Inode size is increased
 * by len bytes.
 * Returns 0 on success, error otherwise.
 */
static int ext4_insert_range(struct file *file, loff_t offset, loff_t len)
{
        struct inode *inode = file_inode(file);
        struct super_block *sb = inode->i_sb;
        struct address_space *mapping = inode->i_mapping;
        handle_t *handle;
        struct ext4_ext_path *path;
        struct ext4_extent *extent;
        ext4_lblk_t start_lblk, len_lblk, ee_start_lblk = 0;
        unsigned int credits, ee_len;
        int ret, depth;
        loff_t start;

        trace_ext4_insert_range(inode, offset, len);
        WARN_ON_ONCE(!inode_is_locked(inode));

        /* Currently just for extent based files */
        if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
                return -EOPNOTSUPP;
        /* Insert range works only on fs cluster size aligned regions. */
        if (!IS_ALIGNED(offset | len, EXT4_CLUSTER_SIZE(sb)))
                return -EINVAL;
        /* Offset must be less than i_size */
        if (offset >= inode->i_size)
                return -EINVAL;
        /* Check whether the maximum file size would be exceeded */
        if (len > inode->i_sb->s_maxbytes - inode->i_size)
                return -EFBIG;

        /*
         * Write out all dirty pages. Need to round down to align start offset
         * to page size boundary for page size > block size.
         */
        start = round_down(offset, PAGE_SIZE);
        ret = filemap_write_and_wait_range(mapping, start, LLONG_MAX);
        if (ret)
                return ret;

        truncate_pagecache(inode, start);

        credits = ext4_chunk_trans_extent(inode, 0);
        handle = ext4_journal_start(inode, EXT4_HT_TRUNCATE, credits);
        if (IS_ERR(handle))
                return PTR_ERR(handle);

        ext4_fc_mark_ineligible(sb, EXT4_FC_REASON_FALLOC_RANGE, handle);

        /* Expand file to avoid data loss if there is error while shifting */
        inode->i_size += len;
        EXT4_I(inode)->i_disksize += len;
        ret = ext4_mark_inode_dirty(handle, inode);
        if (ret)
                goto out_handle;

        start_lblk = offset >> inode->i_blkbits;
        len_lblk = len >> inode->i_blkbits;

        ext4_check_map_extents_env(inode);

        down_write(&EXT4_I(inode)->i_data_sem);
        ext4_discard_preallocations(inode);

        path = ext4_find_extent(inode, start_lblk, NULL, 0);
        if (IS_ERR(path)) {
                up_write(&EXT4_I(inode)->i_data_sem);
                ret = PTR_ERR(path);
                goto out_handle;
        }

        depth = ext_depth(inode);
        extent = path[depth].p_ext;
        if (extent) {
                ee_start_lblk = le32_to_cpu(extent->ee_block);
                ee_len = ext4_ext_get_actual_len(extent);

                /*
                 * If start_lblk is not the starting block of extent, split
                 * the extent @start_lblk
                 */
                if ((start_lblk > ee_start_lblk) &&
                                (start_lblk < (ee_start_lblk + ee_len))) {
                        path = ext4_split_extent_at(handle, inode, path,
                                        start_lblk, EXT4_EX_NOCACHE |
                                        EXT4_GET_BLOCKS_SPLIT_NOMERGE |
                                        EXT4_GET_BLOCKS_METADATA_NOFAIL);
                }

                if (IS_ERR(path)) {
                        up_write(&EXT4_I(inode)->i_data_sem);
                        ret = PTR_ERR(path);
                        goto out_handle;
                }
        }

        ext4_free_ext_path(path);
        ext4_es_remove_extent(inode, start_lblk, EXT_MAX_BLOCKS - start_lblk);

        /*
         * if start_lblk lies in a hole which is at start of file, use
         * ee_start_lblk to shift extents
         */
        ret = ext4_ext_shift_extents(inode, handle,
                max(ee_start_lblk, start_lblk), len_lblk, SHIFT_RIGHT);
        up_write(&EXT4_I(inode)->i_data_sem);
        if (ret)
                goto out_handle;

        ext4_update_inode_fsync_trans(handle, inode, 1);
        if (IS_SYNC(inode))
                ext4_handle_sync(handle);

out_handle:
        ext4_journal_stop(handle);
        return ret;
}

/**
 * ext4_swap_extents() - Swap extents between two inodes
 * @handle: handle for this transaction
 * @inode1:     First inode
 * @inode2:     Second inode
 * @lblk1:      Start block for first inode
 * @lblk2:      Start block for second inode
 * @count:      Number of blocks to swap
 * @unwritten: Mark second inode's extents as unwritten after swap
 * @erp:        Pointer to save error value
 *
 * This helper routine does exactly what is promise "swap extents". All other
 * stuff such as page-cache locking consistency, bh mapping consistency or
 * extent's data copying must be performed by caller.
 * Locking:
 *              i_rwsem is held for both inodes
 *              i_data_sem is locked for write for both inodes
 * Assumptions:
 *              All pages from requested range are locked for both inodes
 */
int
ext4_swap_extents(handle_t *handle, struct inode *inode1,
                  struct inode *inode2, ext4_lblk_t lblk1, ext4_lblk_t lblk2,
                  ext4_lblk_t count, int unwritten, int *erp)
{
        struct ext4_ext_path *path1 = NULL;
        struct ext4_ext_path *path2 = NULL;
        int replaced_count = 0;

        BUG_ON(!rwsem_is_locked(&EXT4_I(inode1)->i_data_sem));
        BUG_ON(!rwsem_is_locked(&EXT4_I(inode2)->i_data_sem));
        BUG_ON(!inode_is_locked(inode1));
        BUG_ON(!inode_is_locked(inode2));

        ext4_es_remove_extent(inode1, lblk1, count);
        ext4_es_remove_extent(inode2, lblk2, count);

        while (count) {
                struct ext4_extent *ex1, *ex2, tmp_ex;
                ext4_lblk_t e1_blk, e2_blk;
                int e1_len, e2_len, len;
                int split = 0;

                path1 = ext4_find_extent(inode1, lblk1, path1, EXT4_EX_NOCACHE);
                if (IS_ERR(path1)) {
                        *erp = PTR_ERR(path1);
                        goto errout;
                }
                path2 = ext4_find_extent(inode2, lblk2, path2, EXT4_EX_NOCACHE);
                if (IS_ERR(path2)) {
                        *erp = PTR_ERR(path2);
                        goto errout;
                }
                ex1 = path1[path1->p_depth].p_ext;
                ex2 = path2[path2->p_depth].p_ext;
                /* Do we have something to swap ? */
                if (unlikely(!ex2 || !ex1))
                        goto errout;

                e1_blk = le32_to_cpu(ex1->ee_block);
                e2_blk = le32_to_cpu(ex2->ee_block);
                e1_len = ext4_ext_get_actual_len(ex1);
                e2_len = ext4_ext_get_actual_len(ex2);

                /* Hole handling */
                if (!in_range(lblk1, e1_blk, e1_len) ||
                    !in_range(lblk2, e2_blk, e2_len)) {
                        ext4_lblk_t next1, next2;

                        /* if hole after extent, then go to next extent */
                        next1 = ext4_ext_next_allocated_block(path1);
                        next2 = ext4_ext_next_allocated_block(path2);
                        /* If hole before extent, then shift to that extent */
                        if (e1_blk > lblk1)
                                next1 = e1_blk;
                        if (e2_blk > lblk2)
                                next2 = e2_blk;
                        /* Do we have something to swap */
                        if (next1 == EXT_MAX_BLOCKS || next2 == EXT_MAX_BLOCKS)
                                goto errout;
                        /* Move to the rightest boundary */
                        len = next1 - lblk1;
                        if (len < next2 - lblk2)
                                len = next2 - lblk2;
                        if (len > count)
                                len = count;
                        lblk1 += len;
                        lblk2 += len;
                        count -= len;
                        continue;
                }

                /* Prepare left boundary */
                if (e1_blk < lblk1) {
                        split = 1;
                        path1 = ext4_force_split_extent_at(handle, inode1,
                                                           path1, lblk1, 0);
                        if (IS_ERR(path1)) {
                                *erp = PTR_ERR(path1);
                                goto errout;
                        }
                }
                if (e2_blk < lblk2) {
                        split = 1;
                        path2 = ext4_force_split_extent_at(handle, inode2,
                                                           path2, lblk2, 0);
                        if (IS_ERR(path2)) {
                                *erp = PTR_ERR(path2);
                                goto errout;
                        }
                }
                /* ext4_split_extent_at() may result in leaf extent split,
                 * path must to be revalidated. */
                if (split)
                        continue;

                /* Prepare right boundary */
                len = count;
                if (len > e1_blk + e1_len - lblk1)
                        len = e1_blk + e1_len - lblk1;
                if (len > e2_blk + e2_len - lblk2)
                        len = e2_blk + e2_len - lblk2;

                if (len != e1_len) {
                        split = 1;
                        path1 = ext4_force_split_extent_at(handle, inode1,
                                                        path1, lblk1 + len, 0);
                        if (IS_ERR(path1)) {
                                *erp = PTR_ERR(path1);
                                goto errout;
                        }
                }
                if (len != e2_len) {
                        split = 1;
                        path2 = ext4_force_split_extent_at(handle, inode2,
                                                        path2, lblk2 + len, 0);
                        if (IS_ERR(path2)) {
                                *erp = PTR_ERR(path2);
                                goto errout;
                        }
                }
                /* ext4_split_extent_at() may result in leaf extent split,
                 * path must to be revalidated. */
                if (split)
                        continue;

                BUG_ON(e2_len != e1_len);
                *erp = ext4_ext_get_access(handle, inode1, path1 + path1->p_depth);
                if (unlikely(*erp))
                        goto errout;
                *erp = ext4_ext_get_access(handle, inode2, path2 + path2->p_depth);
                if (unlikely(*erp))
                        goto errout;

                /* Both extents are fully inside boundaries. Swap it now */
                tmp_ex = *ex1;
                ext4_ext_store_pblock(ex1, ext4_ext_pblock(ex2));
                ext4_ext_store_pblock(ex2, ext4_ext_pblock(&tmp_ex));
                ex1->ee_len = cpu_to_le16(e2_len);
                ex2->ee_len = cpu_to_le16(e1_len);
                if (unwritten)
                        ext4_ext_mark_unwritten(ex2);
                if (ext4_ext_is_unwritten(&tmp_ex))
                        ext4_ext_mark_unwritten(ex1);

                ext4_ext_try_to_merge(handle, inode2, path2, ex2);
                ext4_ext_try_to_merge(handle, inode1, path1, ex1);
                *erp = ext4_ext_dirty(handle, inode2, path2 +
                                      path2->p_depth);
                if (unlikely(*erp))
                        goto errout;
                *erp = ext4_ext_dirty(handle, inode1, path1 +
                                      path1->p_depth);
                /*
                 * Looks scarry ah..? second inode already points to new blocks,
                 * and it was successfully dirtied. But luckily error may happen
                 * only due to journal error, so full transaction will be
                 * aborted anyway.
                 */
                if (unlikely(*erp))
                        goto errout;

                lblk1 += len;
                lblk2 += len;
                replaced_count += len;
                count -= len;
        }

errout:
        ext4_free_ext_path(path1);
        ext4_free_ext_path(path2);
        return replaced_count;
}

/*
 * ext4_clu_mapped - determine whether any block in a logical cluster has
 *                   been mapped to a physical cluster
 *
 * @inode - file containing the logical cluster
 * @lclu - logical cluster of interest
 *
 * Returns 1 if any block in the logical cluster is mapped, signifying
 * that a physical cluster has been allocated for it.  Otherwise,
 * returns 0.  Can also return negative error codes.  Derived from
 * ext4_ext_map_blocks().
 */
int ext4_clu_mapped(struct inode *inode, ext4_lblk_t lclu)
{
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
        struct ext4_ext_path *path;
        int depth, mapped = 0, err = 0;
        struct ext4_extent *extent;
        ext4_lblk_t first_lblk, first_lclu, last_lclu;

        /*
         * if data can be stored inline, the logical cluster isn't
         * mapped - no physical clusters have been allocated, and the
         * file has no extents
         */
        if (ext4_test_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA) ||
            ext4_has_inline_data(inode))
                return 0;

        /* search for the extent closest to the first block in the cluster */
        path = ext4_find_extent(inode, EXT4_C2B(sbi, lclu), NULL, 0);
        if (IS_ERR(path))
                return PTR_ERR(path);

        depth = ext_depth(inode);

        /*
         * A consistent leaf must not be empty.  This situation is possible,
         * though, _during_ tree modification, and it's why an assert can't
         * be put in ext4_find_extent().
         */
        if (unlikely(path[depth].p_ext == NULL && depth != 0)) {
                EXT4_ERROR_INODE(inode,
                    "bad extent address - lblock: %lu, depth: %d, pblock: %lld",
                                 (unsigned long) EXT4_C2B(sbi, lclu),
                                 depth, path[depth].p_block);
                err = -EFSCORRUPTED;
                goto out;
        }

        extent = path[depth].p_ext;

        /* can't be mapped if the extent tree is empty */
        if (extent == NULL)
                goto out;

        first_lblk = le32_to_cpu(extent->ee_block);
        first_lclu = EXT4_B2C(sbi, first_lblk);

        /*
         * Three possible outcomes at this point - found extent spanning
         * the target cluster, to the left of the target cluster, or to the
         * right of the target cluster.  The first two cases are handled here.
         * The last case indicates the target cluster is not mapped.
         */
        if (lclu >= first_lclu) {
                last_lclu = EXT4_B2C(sbi, first_lblk +
                                     ext4_ext_get_actual_len(extent) - 1);
                if (lclu <= last_lclu) {
                        mapped = 1;
                } else {
                        first_lblk = ext4_ext_next_allocated_block(path);
                        first_lclu = EXT4_B2C(sbi, first_lblk);
                        if (lclu == first_lclu)
                                mapped = 1;
                }
        }

out:
        ext4_free_ext_path(path);

        return err ? err : mapped;
}

/*
 * Updates physical block address and unwritten status of extent
 * starting at lblk start and of len. If such an extent doesn't exist,
 * this function splits the extent tree appropriately to create an
 * extent like this.  This function is called in the fast commit
 * replay path.  Returns 0 on success and error on failure.
 */
int ext4_ext_replay_update_ex(struct inode *inode, ext4_lblk_t start,
                              int len, int unwritten, ext4_fsblk_t pblk)
{
        struct ext4_ext_path *path;
        struct ext4_extent *ex;
        int ret;

        path = ext4_find_extent(inode, start, NULL, 0);
        if (IS_ERR(path))
                return PTR_ERR(path);
        ex = path[path->p_depth].p_ext;
        if (!ex) {
                ret = -EFSCORRUPTED;
                goto out;
        }

        if (le32_to_cpu(ex->ee_block) != start ||
                ext4_ext_get_actual_len(ex) != len) {
                /* We need to split this extent to match our extent first */
                down_write(&EXT4_I(inode)->i_data_sem);
                path = ext4_force_split_extent_at(NULL, inode, path, start, 1);
                up_write(&EXT4_I(inode)->i_data_sem);
                if (IS_ERR(path)) {
                        ret = PTR_ERR(path);
                        goto out;
                }

                path = ext4_find_extent(inode, start, path, 0);
                if (IS_ERR(path))
                        return PTR_ERR(path);

                ex = path[path->p_depth].p_ext;
                WARN_ON(le32_to_cpu(ex->ee_block) != start);

                if (ext4_ext_get_actual_len(ex) != len) {
                        down_write(&EXT4_I(inode)->i_data_sem);
                        path = ext4_force_split_extent_at(NULL, inode, path,
                                                          start + len, 1);
                        up_write(&EXT4_I(inode)->i_data_sem);
                        if (IS_ERR(path)) {
                                ret = PTR_ERR(path);
                                goto out;
                        }

                        path = ext4_find_extent(inode, start, path, 0);
                        if (IS_ERR(path))
                                return PTR_ERR(path);
                        ex = path[path->p_depth].p_ext;
                }
        }
        if (unwritten)
                ext4_ext_mark_unwritten(ex);
        else
                ext4_ext_mark_initialized(ex);
        ext4_ext_store_pblock(ex, pblk);
        down_write(&EXT4_I(inode)->i_data_sem);
        ret = ext4_ext_dirty(NULL, inode, &path[path->p_depth]);
        up_write(&EXT4_I(inode)->i_data_sem);
out:
        ext4_free_ext_path(path);
        ext4_mark_inode_dirty(NULL, inode);
        return ret;
}

/* Try to shrink the extent tree */
void ext4_ext_replay_shrink_inode(struct inode *inode, ext4_lblk_t end)
{
        struct ext4_ext_path *path = NULL;
        struct ext4_extent *ex;
        ext4_lblk_t old_cur, cur = 0;

        while (cur < end) {
                path = ext4_find_extent(inode, cur, NULL, 0);
                if (IS_ERR(path))
                        return;
                ex = path[path->p_depth].p_ext;
                if (!ex) {
                        ext4_free_ext_path(path);
                        ext4_mark_inode_dirty(NULL, inode);
                        return;
                }
                old_cur = cur;
                cur = le32_to_cpu(ex->ee_block) + ext4_ext_get_actual_len(ex);
                if (cur <= old_cur)
                        cur = old_cur + 1;
                ext4_ext_try_to_merge(NULL, inode, path, ex);
                down_write(&EXT4_I(inode)->i_data_sem);
                ext4_ext_dirty(NULL, inode, &path[path->p_depth]);
                up_write(&EXT4_I(inode)->i_data_sem);
                ext4_mark_inode_dirty(NULL, inode);
                ext4_free_ext_path(path);
        }
}

/* Check if *cur is a hole and if it is, skip it */
static int skip_hole(struct inode *inode, ext4_lblk_t *cur)
{
        int ret;
        struct ext4_map_blocks map;

        map.m_lblk = *cur;
        map.m_len = ((inode->i_size) >> inode->i_sb->s_blocksize_bits) - *cur;

        ret = ext4_map_blocks(NULL, inode, &map, 0);
        if (ret < 0)
                return ret;
        if (ret != 0)
                return 0;
        *cur = *cur + map.m_len;
        return 0;
}

/* Count number of blocks used by this inode and update i_blocks */
int ext4_ext_replay_set_iblocks(struct inode *inode)
{
        struct ext4_ext_path *path = NULL, *path2 = NULL;
        struct ext4_extent *ex;
        ext4_lblk_t cur = 0, end;
        int numblks = 0, i, ret = 0;
        ext4_fsblk_t cmp1, cmp2;
        struct ext4_map_blocks map;

        /* Determin the size of the file first */
        path = ext4_find_extent(inode, EXT_MAX_BLOCKS - 1, NULL,
                                        EXT4_EX_NOCACHE);
        if (IS_ERR(path))
                return PTR_ERR(path);
        ex = path[path->p_depth].p_ext;
        if (!ex)
                goto out;
        end = le32_to_cpu(ex->ee_block) + ext4_ext_get_actual_len(ex);

        /* Count the number of data blocks */
        cur = 0;
        while (cur < end) {
                map.m_lblk = cur;
                map.m_len = end - cur;
                ret = ext4_map_blocks(NULL, inode, &map, 0);
                if (ret < 0)
                        break;
                if (ret > 0)
                        numblks += ret;
                cur = cur + map.m_len;
        }

        /*
         * Count the number of extent tree blocks. We do it by looking up
         * two successive extents and determining the difference between
         * their paths. When path is different for 2 successive extents
         * we compare the blocks in the path at each level and increment
         * iblocks by total number of differences found.
         */
        cur = 0;
        ret = skip_hole(inode, &cur);
        if (ret < 0)
                goto out;
        path = ext4_find_extent(inode, cur, path, 0);
        if (IS_ERR(path))
                goto out;
        numblks += path->p_depth;
        while (cur < end) {
                path = ext4_find_extent(inode, cur, path, 0);
                if (IS_ERR(path))
                        break;
                ex = path[path->p_depth].p_ext;
                if (!ex)
                        goto cleanup;

                cur = max(cur + 1, le32_to_cpu(ex->ee_block) +
                                        ext4_ext_get_actual_len(ex));
                ret = skip_hole(inode, &cur);
                if (ret < 0)
                        break;

                path2 = ext4_find_extent(inode, cur, path2, 0);
                if (IS_ERR(path2))
                        break;

                for (i = 0; i <= max(path->p_depth, path2->p_depth); i++) {
                        cmp1 = cmp2 = 0;
                        if (i <= path->p_depth)
                                cmp1 = path[i].p_bh ?
                                        path[i].p_bh->b_blocknr : 0;
                        if (i <= path2->p_depth)
                                cmp2 = path2[i].p_bh ?
                                        path2[i].p_bh->b_blocknr : 0;
                        if (cmp1 != cmp2 && cmp2 != 0)
                                numblks++;
                }
        }

out:
        inode->i_blocks = numblks << (inode->i_sb->s_blocksize_bits - 9);
        ext4_mark_inode_dirty(NULL, inode);
cleanup:
        ext4_free_ext_path(path);
        ext4_free_ext_path(path2);
        return 0;
}

int ext4_ext_clear_bb(struct inode *inode)
{
        struct ext4_ext_path *path = NULL;
        struct ext4_extent *ex;
        ext4_lblk_t cur = 0, end;
        int j, ret = 0;
        struct ext4_map_blocks map;

        if (ext4_test_inode_flag(inode, EXT4_INODE_INLINE_DATA))
                return 0;

        /* Determin the size of the file first */
        path = ext4_find_extent(inode, EXT_MAX_BLOCKS - 1, NULL,
                                        EXT4_EX_NOCACHE);
        if (IS_ERR(path))
                return PTR_ERR(path);
        ex = path[path->p_depth].p_ext;
        if (!ex)
                goto out;
        end = le32_to_cpu(ex->ee_block) + ext4_ext_get_actual_len(ex);

        cur = 0;
        while (cur < end) {
                map.m_lblk = cur;
                map.m_len = end - cur;
                ret = ext4_map_blocks(NULL, inode, &map, 0);
                if (ret < 0)
                        break;
                if (ret > 0) {
                        path = ext4_find_extent(inode, map.m_lblk, path, 0);
                        if (!IS_ERR(path)) {
                                for (j = 0; j < path->p_depth; j++) {
                                        ext4_mb_mark_bb(inode->i_sb,
                                                        path[j].p_block, 1, false);
                                        ext4_fc_record_regions(inode->i_sb, inode->i_ino,
                                                        0, path[j].p_block, 1, 1);
                                }
                        } else {
                                path = NULL;
                        }
                        ext4_mb_mark_bb(inode->i_sb, map.m_pblk, map.m_len, false);
                        ext4_fc_record_regions(inode->i_sb, inode->i_ino,
                                        map.m_lblk, map.m_pblk, map.m_len, 1);
                }
                cur = cur + map.m_len;
        }

out:
        ext4_free_ext_path(path);
        return 0;
}

#if IS_ENABLED(CONFIG_EXT4_KUNIT_TESTS)
int ext4_ext_space_root_idx_test(struct inode *inode, int check)
{
        return ext4_ext_space_root_idx(inode, check);
}
EXPORT_SYMBOL_FOR_EXT4_TEST(ext4_ext_space_root_idx_test);

struct ext4_ext_path *ext4_split_convert_extents_test(handle_t *handle,
                        struct inode *inode, struct ext4_map_blocks *map,
                        struct ext4_ext_path *path, int flags,
                        unsigned int *allocated)
{
        return ext4_split_convert_extents(handle, inode, map, path,
                                          flags, allocated);
}
EXPORT_SYMBOL_FOR_EXT4_TEST(ext4_split_convert_extents_test);

EXPORT_SYMBOL_FOR_EXT4_TEST(__ext4_ext_dirty);
EXPORT_SYMBOL_FOR_EXT4_TEST(ext4_ext_zeroout);
EXPORT_SYMBOL_FOR_EXT4_TEST(ext4_es_register_shrinker);
EXPORT_SYMBOL_FOR_EXT4_TEST(ext4_es_unregister_shrinker);
EXPORT_SYMBOL_FOR_EXT4_TEST(ext4_map_create_blocks);
EXPORT_SYMBOL_FOR_EXT4_TEST(ext4_es_init_tree);
EXPORT_SYMBOL_FOR_EXT4_TEST(ext4_es_lookup_extent);
EXPORT_SYMBOL_FOR_EXT4_TEST(ext4_es_insert_extent);
EXPORT_SYMBOL_FOR_EXT4_TEST(ext4_ext_insert_extent);
EXPORT_SYMBOL_FOR_EXT4_TEST(ext4_find_extent);
EXPORT_SYMBOL_FOR_EXT4_TEST(ext4_issue_zeroout);
EXPORT_SYMBOL_FOR_EXT4_TEST(ext4_map_query_blocks);
#endif