// SPDX-License-Identifier: GPL-2.0+
/*
 * NILFS module and super block management.
 *
 * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
 *
 * Written by Ryusuke Konishi.
 */
/*
 *  linux/fs/ext2/super.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card (card@masi.ibp.fr)
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  from
 *
 *  linux/fs/minix/inode.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller (davem@caip.rutgers.edu), 1995
 */

#include <linux/module.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/blkdev.h>
#include <linux/crc32.h>
#include <linux/vfs.h>
#include <linux/writeback.h>
#include <linux/seq_file.h>
#include <linux/mount.h>
#include <linux/fs_context.h>
#include <linux/fs_parser.h>
#include "nilfs.h"
#include "export.h"
#include "mdt.h"
#include "alloc.h"
#include "btree.h"
#include "btnode.h"
#include "page.h"
#include "cpfile.h"
#include "sufile.h" /* nilfs_sufile_resize(), nilfs_sufile_set_alloc_range() */
#include "ifile.h"
#include "dat.h"
#include "segment.h"
#include "segbuf.h"

MODULE_AUTHOR("NTT Corp.");
MODULE_DESCRIPTION("A New Implementation of the Log-structured Filesystem "
                   "(NILFS)");
MODULE_LICENSE("GPL");

static struct kmem_cache *nilfs_inode_cachep;
struct kmem_cache *nilfs_transaction_cachep;
struct kmem_cache *nilfs_segbuf_cachep;
struct kmem_cache *nilfs_btree_path_cache;

static int nilfs_setup_super(struct super_block *sb, int is_mount);

void __nilfs_msg(struct super_block *sb, const char *fmt, ...)
{
        struct va_format vaf;
        va_list args;
        int level;

        va_start(args, fmt);

        level = printk_get_level(fmt);
        vaf.fmt = printk_skip_level(fmt);
        vaf.va = &args;

        if (sb)
                printk("%c%cNILFS (%s): %pV\n",
                       KERN_SOH_ASCII, level, sb->s_id, &vaf);
        else
                printk("%c%cNILFS: %pV\n",
                       KERN_SOH_ASCII, level, &vaf);

        va_end(args);
}

static void nilfs_set_error(struct super_block *sb)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        struct nilfs_super_block **sbp;

        down_write(&nilfs->ns_sem);
        if (!(nilfs->ns_mount_state & NILFS_ERROR_FS)) {
                nilfs->ns_mount_state |= NILFS_ERROR_FS;
                sbp = nilfs_prepare_super(sb, 0);
                if (likely(sbp)) {
                        sbp[0]->s_state |= cpu_to_le16(NILFS_ERROR_FS);
                        if (sbp[1])
                                sbp[1]->s_state |= cpu_to_le16(NILFS_ERROR_FS);
                        nilfs_commit_super(sb, NILFS_SB_COMMIT_ALL);
                }
        }
        up_write(&nilfs->ns_sem);
}

/**
 * __nilfs_error() - report failure condition on a filesystem
 * @sb:       super block instance
 * @function: name of calling function
 * @fmt:      format string for message to be output
 * @...:      optional arguments to @fmt
 *
 * __nilfs_error() sets an ERROR_FS flag on the superblock as well as
 * reporting an error message.  This function should be called when
 * NILFS detects incoherences or defects of meta data on disk.
 *
 * This implements the body of nilfs_error() macro.  Normally,
 * nilfs_error() should be used.  As for sustainable errors such as a
 * single-shot I/O error, nilfs_err() should be used instead.
 *
 * Callers should not add a trailing newline since this will do it.
 */
void __nilfs_error(struct super_block *sb, const char *function,
                   const char *fmt, ...)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        struct va_format vaf;
        va_list args;

        va_start(args, fmt);

        vaf.fmt = fmt;
        vaf.va = &args;

        printk(KERN_CRIT "NILFS error (device %s): %s: %pV\n",
               sb->s_id, function, &vaf);

        va_end(args);

        if (!sb_rdonly(sb)) {
                nilfs_set_error(sb);

                if (nilfs_test_opt(nilfs, ERRORS_RO)) {
                        printk(KERN_CRIT "Remounting filesystem read-only\n");
                        sb->s_flags |= SB_RDONLY;
                }
        }

        if (nilfs_test_opt(nilfs, ERRORS_PANIC))
                panic("NILFS (device %s): panic forced after error\n",
                      sb->s_id);
}

struct inode *nilfs_alloc_inode(struct super_block *sb)
{
        struct nilfs_inode_info *ii;

        ii = alloc_inode_sb(sb, nilfs_inode_cachep, GFP_NOFS);
        if (!ii)
                return NULL;
        ii->i_bh = NULL;
        ii->i_state = 0;
        ii->i_type = 0;
        ii->i_cno = 0;
        ii->i_assoc_inode = NULL;
        ii->i_bmap = &ii->i_bmap_data;
        return &ii->vfs_inode;
}

static void nilfs_free_inode(struct inode *inode)
{
        if (nilfs_is_metadata_file_inode(inode))
                nilfs_mdt_destroy(inode);

        kmem_cache_free(nilfs_inode_cachep, NILFS_I(inode));
}

static int nilfs_sync_super(struct super_block *sb, int flag)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        int err;

 retry:
        set_buffer_dirty(nilfs->ns_sbh[0]);
        if (nilfs_test_opt(nilfs, BARRIER)) {
                err = __sync_dirty_buffer(nilfs->ns_sbh[0],
                                          REQ_SYNC | REQ_PREFLUSH | REQ_FUA);
        } else {
                err = sync_dirty_buffer(nilfs->ns_sbh[0]);
        }

        if (unlikely(err)) {
                nilfs_err(sb, "unable to write superblock: err=%d", err);
                if (err == -EIO && nilfs->ns_sbh[1]) {
                        /*
                         * sbp[0] points to newer log than sbp[1],
                         * so copy sbp[0] to sbp[1] to take over sbp[0].
                         */
                        memcpy(nilfs->ns_sbp[1], nilfs->ns_sbp[0],
                               nilfs->ns_sbsize);
                        nilfs_fall_back_super_block(nilfs);
                        goto retry;
                }
        } else {
                struct nilfs_super_block *sbp = nilfs->ns_sbp[0];

                nilfs->ns_sbwcount++;

                /*
                 * The latest segment becomes trailable from the position
                 * written in superblock.
                 */
                clear_nilfs_discontinued(nilfs);

                /* update GC protection for recent segments */
                if (nilfs->ns_sbh[1]) {
                        if (flag == NILFS_SB_COMMIT_ALL) {
                                set_buffer_dirty(nilfs->ns_sbh[1]);
                                if (sync_dirty_buffer(nilfs->ns_sbh[1]) < 0)
                                        goto out;
                        }
                        if (le64_to_cpu(nilfs->ns_sbp[1]->s_last_cno) <
                            le64_to_cpu(nilfs->ns_sbp[0]->s_last_cno))
                                sbp = nilfs->ns_sbp[1];
                }

                spin_lock(&nilfs->ns_last_segment_lock);
                nilfs->ns_prot_seq = le64_to_cpu(sbp->s_last_seq);
                spin_unlock(&nilfs->ns_last_segment_lock);
        }
 out:
        return err;
}

void nilfs_set_log_cursor(struct nilfs_super_block *sbp,
                          struct the_nilfs *nilfs)
{
        sector_t nfreeblocks;

        /* nilfs->ns_sem must be locked by the caller. */
        nilfs_count_free_blocks(nilfs, &nfreeblocks);
        sbp->s_free_blocks_count = cpu_to_le64(nfreeblocks);

        spin_lock(&nilfs->ns_last_segment_lock);
        sbp->s_last_seq = cpu_to_le64(nilfs->ns_last_seq);
        sbp->s_last_pseg = cpu_to_le64(nilfs->ns_last_pseg);
        sbp->s_last_cno = cpu_to_le64(nilfs->ns_last_cno);
        spin_unlock(&nilfs->ns_last_segment_lock);
}

struct nilfs_super_block **nilfs_prepare_super(struct super_block *sb,
                                               int flip)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        struct nilfs_super_block **sbp = nilfs->ns_sbp;

        /* nilfs->ns_sem must be locked by the caller. */
        if (sbp[0]->s_magic != cpu_to_le16(NILFS_SUPER_MAGIC)) {
                if (sbp[1] &&
                    sbp[1]->s_magic == cpu_to_le16(NILFS_SUPER_MAGIC)) {
                        memcpy(sbp[0], sbp[1], nilfs->ns_sbsize);
                } else {
                        nilfs_crit(sb, "superblock broke");
                        return NULL;
                }
        } else if (sbp[1] &&
                   sbp[1]->s_magic != cpu_to_le16(NILFS_SUPER_MAGIC)) {
                memcpy(sbp[1], sbp[0], nilfs->ns_sbsize);
        }

        if (flip && sbp[1])
                nilfs_swap_super_block(nilfs);

        return sbp;
}

int nilfs_commit_super(struct super_block *sb, int flag)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        struct nilfs_super_block **sbp = nilfs->ns_sbp;
        time64_t t;

        /* nilfs->ns_sem must be locked by the caller. */
        t = ktime_get_real_seconds();
        nilfs->ns_sbwtime = t;
        sbp[0]->s_wtime = cpu_to_le64(t);
        sbp[0]->s_sum = 0;
        sbp[0]->s_sum = cpu_to_le32(crc32_le(nilfs->ns_crc_seed,
                                             (unsigned char *)sbp[0],
                                             nilfs->ns_sbsize));
        if (flag == NILFS_SB_COMMIT_ALL && sbp[1]) {
                sbp[1]->s_wtime = sbp[0]->s_wtime;
                sbp[1]->s_sum = 0;
                sbp[1]->s_sum = cpu_to_le32(crc32_le(nilfs->ns_crc_seed,
                                            (unsigned char *)sbp[1],
                                            nilfs->ns_sbsize));
        }
        clear_nilfs_sb_dirty(nilfs);
        nilfs->ns_flushed_device = 1;
        /* make sure store to ns_flushed_device cannot be reordered */
        smp_wmb();
        return nilfs_sync_super(sb, flag);
}

/**
 * nilfs_cleanup_super() - write filesystem state for cleanup
 * @sb: super block instance to be unmounted or degraded to read-only
 *
 * This function restores state flags in the on-disk super block.
 * This will set "clean" flag (i.e. NILFS_VALID_FS) unless the
 * filesystem was not clean previously.
 *
 * Return: 0 on success, %-EIO if I/O error or superblock is corrupted.
 */
int nilfs_cleanup_super(struct super_block *sb)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        struct nilfs_super_block **sbp;
        int flag = NILFS_SB_COMMIT;
        int ret = -EIO;

        sbp = nilfs_prepare_super(sb, 0);
        if (sbp) {
                sbp[0]->s_state = cpu_to_le16(nilfs->ns_mount_state);
                nilfs_set_log_cursor(sbp[0], nilfs);
                if (sbp[1] && sbp[0]->s_last_cno == sbp[1]->s_last_cno) {
                        /*
                         * make the "clean" flag also to the opposite
                         * super block if both super blocks point to
                         * the same checkpoint.
                         */
                        sbp[1]->s_state = sbp[0]->s_state;
                        flag = NILFS_SB_COMMIT_ALL;
                }
                ret = nilfs_commit_super(sb, flag);
        }
        return ret;
}

/**
 * nilfs_move_2nd_super - relocate secondary super block
 * @sb: super block instance
 * @sb2off: new offset of the secondary super block (in bytes)
 *
 * Return: 0 on success, or a negative error code on failure.
 */
static int nilfs_move_2nd_super(struct super_block *sb, loff_t sb2off)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        struct buffer_head *nsbh;
        struct nilfs_super_block *nsbp;
        sector_t blocknr, newblocknr;
        unsigned long offset;
        int sb2i;  /* array index of the secondary superblock */
        int ret = 0;

        /* nilfs->ns_sem must be locked by the caller. */
        if (nilfs->ns_sbh[1] &&
            nilfs->ns_sbh[1]->b_blocknr > nilfs->ns_first_data_block) {
                sb2i = 1;
                blocknr = nilfs->ns_sbh[1]->b_blocknr;
        } else if (nilfs->ns_sbh[0]->b_blocknr > nilfs->ns_first_data_block) {
                sb2i = 0;
                blocknr = nilfs->ns_sbh[0]->b_blocknr;
        } else {
                sb2i = -1;
                blocknr = 0;
        }
        if (sb2i >= 0 && (u64)blocknr << nilfs->ns_blocksize_bits == sb2off)
                goto out;  /* super block location is unchanged */

        /* Get new super block buffer */
        newblocknr = sb2off >> nilfs->ns_blocksize_bits;
        offset = sb2off & (nilfs->ns_blocksize - 1);
        nsbh = sb_getblk(sb, newblocknr);
        if (!nsbh) {
                nilfs_warn(sb,
                           "unable to move secondary superblock to block %llu",
                           (unsigned long long)newblocknr);
                ret = -EIO;
                goto out;
        }
        nsbp = (void *)nsbh->b_data + offset;

        lock_buffer(nsbh);
        if (sb2i >= 0) {
                /*
                 * The position of the second superblock only changes by 4KiB,
                 * which is larger than the maximum superblock data size
                 * (= 1KiB), so there is no need to use memmove() to allow
                 * overlap between source and destination.
                 */
                memcpy(nsbp, nilfs->ns_sbp[sb2i], nilfs->ns_sbsize);

                /*
                 * Zero fill after copy to avoid overwriting in case of move
                 * within the same block.
                 */
                memset(nsbh->b_data, 0, offset);
                memset((void *)nsbp + nilfs->ns_sbsize, 0,
                       nsbh->b_size - offset - nilfs->ns_sbsize);
        } else {
                memset(nsbh->b_data, 0, nsbh->b_size);
        }
        set_buffer_uptodate(nsbh);
        unlock_buffer(nsbh);

        if (sb2i >= 0) {
                brelse(nilfs->ns_sbh[sb2i]);
                nilfs->ns_sbh[sb2i] = nsbh;
                nilfs->ns_sbp[sb2i] = nsbp;
        } else if (nilfs->ns_sbh[0]->b_blocknr < nilfs->ns_first_data_block) {
                /* secondary super block will be restored to index 1 */
                nilfs->ns_sbh[1] = nsbh;
                nilfs->ns_sbp[1] = nsbp;
        } else {
                brelse(nsbh);
        }
out:
        return ret;
}

/**
 * nilfs_resize_fs - resize the filesystem
 * @sb: super block instance
 * @newsize: new size of the filesystem (in bytes)
 *
 * Return: 0 on success, or a negative error code on failure.
 */
int nilfs_resize_fs(struct super_block *sb, __u64 newsize)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        struct nilfs_super_block **sbp;
        __u64 devsize, newnsegs;
        loff_t sb2off;
        int ret;

        ret = -ERANGE;
        devsize = bdev_nr_bytes(sb->s_bdev);
        if (newsize > devsize)
                goto out;

        /*
         * Prevent underflow in second superblock position calculation.
         * The exact minimum size check is done in nilfs_sufile_resize().
         */
        if (newsize < 4096) {
                ret = -ENOSPC;
                goto out;
        }

        /*
         * Write lock is required to protect some functions depending
         * on the number of segments, the number of reserved segments,
         * and so forth.
         */
        down_write(&nilfs->ns_segctor_sem);

        sb2off = NILFS_SB2_OFFSET_BYTES(newsize);
        newnsegs = sb2off >> nilfs->ns_blocksize_bits;
        newnsegs = div64_ul(newnsegs, nilfs->ns_blocks_per_segment);

        ret = nilfs_sufile_resize(nilfs->ns_sufile, newnsegs);
        up_write(&nilfs->ns_segctor_sem);
        if (ret < 0)
                goto out;

        ret = nilfs_construct_segment(sb);
        if (ret < 0)
                goto out;

        down_write(&nilfs->ns_sem);
        nilfs_move_2nd_super(sb, sb2off);
        ret = -EIO;
        sbp = nilfs_prepare_super(sb, 0);
        if (likely(sbp)) {
                nilfs_set_log_cursor(sbp[0], nilfs);
                /*
                 * Drop NILFS_RESIZE_FS flag for compatibility with
                 * mount-time resize which may be implemented in a
                 * future release.
                 */
                sbp[0]->s_state = cpu_to_le16(le16_to_cpu(sbp[0]->s_state) &
                                              ~NILFS_RESIZE_FS);
                sbp[0]->s_dev_size = cpu_to_le64(newsize);
                sbp[0]->s_nsegments = cpu_to_le64(nilfs->ns_nsegments);
                if (sbp[1])
                        memcpy(sbp[1], sbp[0], nilfs->ns_sbsize);
                ret = nilfs_commit_super(sb, NILFS_SB_COMMIT_ALL);
        }
        up_write(&nilfs->ns_sem);

        /*
         * Reset the range of allocatable segments last.  This order
         * is important in the case of expansion because the secondary
         * superblock must be protected from log write until migration
         * completes.
         */
        if (!ret)
                nilfs_sufile_set_alloc_range(nilfs->ns_sufile, 0, newnsegs - 1);
out:
        return ret;
}

static void nilfs_put_super(struct super_block *sb)
{
        struct the_nilfs *nilfs = sb->s_fs_info;

        nilfs_detach_log_writer(sb);

        if (!sb_rdonly(sb)) {
                down_write(&nilfs->ns_sem);
                nilfs_cleanup_super(sb);
                up_write(&nilfs->ns_sem);
        }

        nilfs_sysfs_delete_device_group(nilfs);
        iput(nilfs->ns_sufile);
        iput(nilfs->ns_cpfile);
        iput(nilfs->ns_dat);

        destroy_nilfs(nilfs);
        sb->s_fs_info = NULL;
}

static int nilfs_sync_fs(struct super_block *sb, int wait)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        struct nilfs_super_block **sbp;
        int err = 0;

        /* This function is called when super block should be written back */
        if (wait)
                err = nilfs_construct_segment(sb);

        down_write(&nilfs->ns_sem);
        if (nilfs_sb_dirty(nilfs)) {
                sbp = nilfs_prepare_super(sb, nilfs_sb_will_flip(nilfs));
                if (likely(sbp)) {
                        nilfs_set_log_cursor(sbp[0], nilfs);
                        nilfs_commit_super(sb, NILFS_SB_COMMIT);
                }
        }
        up_write(&nilfs->ns_sem);

        if (!err)
                err = nilfs_flush_device(nilfs);

        return err;
}

int nilfs_attach_checkpoint(struct super_block *sb, __u64 cno, int curr_mnt,
                            struct nilfs_root **rootp)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        struct nilfs_root *root;
        int err = -ENOMEM;

        root = nilfs_find_or_create_root(
                nilfs, curr_mnt ? NILFS_CPTREE_CURRENT_CNO : cno);
        if (!root)
                return err;

        if (root->ifile)
                goto reuse; /* already attached checkpoint */

        down_read(&nilfs->ns_segctor_sem);
        err = nilfs_ifile_read(sb, root, cno, nilfs->ns_inode_size);
        up_read(&nilfs->ns_segctor_sem);
        if (unlikely(err))
                goto failed;

 reuse:
        *rootp = root;
        return 0;

 failed:
        if (err == -EINVAL)
                nilfs_err(sb, "Invalid checkpoint (checkpoint number=%llu)",
                          (unsigned long long)cno);
        nilfs_put_root(root);

        return err;
}

static int nilfs_freeze(struct super_block *sb)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        int err;

        if (sb_rdonly(sb))
                return 0;

        /* Mark super block clean */
        down_write(&nilfs->ns_sem);
        err = nilfs_cleanup_super(sb);
        up_write(&nilfs->ns_sem);
        return err;
}

static int nilfs_unfreeze(struct super_block *sb)
{
        struct the_nilfs *nilfs = sb->s_fs_info;

        if (sb_rdonly(sb))
                return 0;

        down_write(&nilfs->ns_sem);
        nilfs_setup_super(sb, false);
        up_write(&nilfs->ns_sem);
        return 0;
}

static int nilfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
        struct super_block *sb = dentry->d_sb;
        struct nilfs_root *root = NILFS_I(d_inode(dentry))->i_root;
        struct the_nilfs *nilfs = root->nilfs;
        u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
        unsigned long long blocks;
        unsigned long overhead;
        unsigned long nrsvblocks;
        sector_t nfreeblocks;
        u64 nmaxinodes, nfreeinodes;
        int err;

        /*
         * Compute all of the segment blocks
         *
         * The blocks before first segment and after last segment
         * are excluded.
         */
        blocks = nilfs->ns_blocks_per_segment * nilfs->ns_nsegments
                - nilfs->ns_first_data_block;
        nrsvblocks = nilfs->ns_nrsvsegs * nilfs->ns_blocks_per_segment;

        /*
         * Compute the overhead
         *
         * When distributing meta data blocks outside segment structure,
         * We must count them as the overhead.
         */
        overhead = 0;

        err = nilfs_count_free_blocks(nilfs, &nfreeblocks);
        if (unlikely(err))
                return err;

        err = nilfs_ifile_count_free_inodes(root->ifile,
                                            &nmaxinodes, &nfreeinodes);
        if (unlikely(err)) {
                nilfs_warn(sb, "failed to count free inodes: err=%d", err);
                if (err == -ERANGE) {
                        /*
                         * If nilfs_palloc_count_max_entries() returns
                         * -ERANGE error code then we simply treat
                         * curent inodes count as maximum possible and
                         * zero as free inodes value.
                         */
                        nmaxinodes = atomic64_read(&root->inodes_count);
                        nfreeinodes = 0;
                        err = 0;
                } else
                        return err;
        }

        buf->f_type = NILFS_SUPER_MAGIC;
        buf->f_bsize = sb->s_blocksize;
        buf->f_blocks = blocks - overhead;
        buf->f_bfree = nfreeblocks;
        buf->f_bavail = (buf->f_bfree >= nrsvblocks) ?
                (buf->f_bfree - nrsvblocks) : 0;
        buf->f_files = nmaxinodes;
        buf->f_ffree = nfreeinodes;
        buf->f_namelen = NILFS_NAME_LEN;
        buf->f_fsid = u64_to_fsid(id);

        return 0;
}

static int nilfs_show_options(struct seq_file *seq, struct dentry *dentry)
{
        struct super_block *sb = dentry->d_sb;
        struct the_nilfs *nilfs = sb->s_fs_info;
        struct nilfs_root *root = NILFS_I(d_inode(dentry))->i_root;

        if (!nilfs_test_opt(nilfs, BARRIER))
                seq_puts(seq, ",nobarrier");
        if (root->cno != NILFS_CPTREE_CURRENT_CNO)
                seq_printf(seq, ",cp=%llu", (unsigned long long)root->cno);
        if (nilfs_test_opt(nilfs, ERRORS_PANIC))
                seq_puts(seq, ",errors=panic");
        if (nilfs_test_opt(nilfs, ERRORS_CONT))
                seq_puts(seq, ",errors=continue");
        if (nilfs_test_opt(nilfs, STRICT_ORDER))
                seq_puts(seq, ",order=strict");
        if (nilfs_test_opt(nilfs, NORECOVERY))
                seq_puts(seq, ",norecovery");
        if (nilfs_test_opt(nilfs, DISCARD))
                seq_puts(seq, ",discard");

        return 0;
}

static const struct super_operations nilfs_sops = {
        .alloc_inode    = nilfs_alloc_inode,
        .free_inode     = nilfs_free_inode,
        .dirty_inode    = nilfs_dirty_inode,
        .evict_inode    = nilfs_evict_inode,
        .put_super      = nilfs_put_super,
        .sync_fs        = nilfs_sync_fs,
        .freeze_fs      = nilfs_freeze,
        .unfreeze_fs    = nilfs_unfreeze,
        .statfs         = nilfs_statfs,
        .show_options = nilfs_show_options
};

enum {
        Opt_err, Opt_barrier, Opt_snapshot, Opt_order, Opt_norecovery,
        Opt_discard,
};

static const struct constant_table nilfs_param_err[] = {
        {"continue",    NILFS_MOUNT_ERRORS_CONT},
        {"panic",       NILFS_MOUNT_ERRORS_PANIC},
        {"remount-ro",  NILFS_MOUNT_ERRORS_RO},
        {}
};

static const struct fs_parameter_spec nilfs_param_spec[] = {
        fsparam_enum    ("errors", Opt_err, nilfs_param_err),
        fsparam_flag_no ("barrier", Opt_barrier),
        fsparam_u64     ("cp", Opt_snapshot),
        fsparam_string  ("order", Opt_order),
        fsparam_flag    ("norecovery", Opt_norecovery),
        fsparam_flag_no ("discard", Opt_discard),
        {}
};

struct nilfs_fs_context {
        unsigned long ns_mount_opt;
        __u64 cno;
};

static int nilfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
{
        struct nilfs_fs_context *nilfs = fc->fs_private;
        int is_remount = fc->purpose == FS_CONTEXT_FOR_RECONFIGURE;
        struct fs_parse_result result;
        int opt;

        opt = fs_parse(fc, nilfs_param_spec, param, &result);
        if (opt < 0)
                return opt;

        switch (opt) {
        case Opt_barrier:
                if (result.negated)
                        nilfs_clear_opt(nilfs, BARRIER);
                else
                        nilfs_set_opt(nilfs, BARRIER);
                break;
        case Opt_order:
                if (strcmp(param->string, "relaxed") == 0)
                        /* Ordered data semantics */
                        nilfs_clear_opt(nilfs, STRICT_ORDER);
                else if (strcmp(param->string, "strict") == 0)
                        /* Strict in-order semantics */
                        nilfs_set_opt(nilfs, STRICT_ORDER);
                else
                        return -EINVAL;
                break;
        case Opt_err:
                nilfs->ns_mount_opt &= ~NILFS_MOUNT_ERROR_MODE;
                nilfs->ns_mount_opt |= result.uint_32;
                break;
        case Opt_snapshot:
                if (is_remount) {
                        struct super_block *sb = fc->root->d_sb;

                        nilfs_err(sb,
                                  "\"%s\" option is invalid for remount",
                                  param->key);
                        return -EINVAL;
                }
                if (result.uint_64 == 0) {
                        nilfs_err(NULL,
                                  "invalid option \"cp=0\": invalid checkpoint number 0");
                        return -EINVAL;
                }
                nilfs->cno = result.uint_64;
                break;
        case Opt_norecovery:
                nilfs_set_opt(nilfs, NORECOVERY);
                break;
        case Opt_discard:
                if (result.negated)
                        nilfs_clear_opt(nilfs, DISCARD);
                else
                        nilfs_set_opt(nilfs, DISCARD);
                break;
        default:
                return -EINVAL;
        }

        return 0;
}

static int nilfs_setup_super(struct super_block *sb, int is_mount)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        struct nilfs_super_block **sbp;
        int max_mnt_count;
        int mnt_count;

        /* nilfs->ns_sem must be locked by the caller. */
        sbp = nilfs_prepare_super(sb, 0);
        if (!sbp)
                return -EIO;

        if (!is_mount)
                goto skip_mount_setup;

        max_mnt_count = le16_to_cpu(sbp[0]->s_max_mnt_count);
        mnt_count = le16_to_cpu(sbp[0]->s_mnt_count);

        if (nilfs->ns_mount_state & NILFS_ERROR_FS) {
                nilfs_warn(sb, "mounting fs with errors");
#if 0
        } else if (max_mnt_count >= 0 && mnt_count >= max_mnt_count) {
                nilfs_warn(sb, "maximal mount count reached");
#endif
        }
        if (!max_mnt_count)
                sbp[0]->s_max_mnt_count = cpu_to_le16(NILFS_DFL_MAX_MNT_COUNT);

        sbp[0]->s_mnt_count = cpu_to_le16(mnt_count + 1);
        sbp[0]->s_mtime = cpu_to_le64(ktime_get_real_seconds());

skip_mount_setup:
        sbp[0]->s_state =
                cpu_to_le16(le16_to_cpu(sbp[0]->s_state) & ~NILFS_VALID_FS);
        /* synchronize sbp[1] with sbp[0] */
        if (sbp[1])
                memcpy(sbp[1], sbp[0], nilfs->ns_sbsize);
        return nilfs_commit_super(sb, NILFS_SB_COMMIT_ALL);
}

struct nilfs_super_block *nilfs_read_super_block(struct super_block *sb,
                                                 u64 pos, int blocksize,
                                                 struct buffer_head **pbh)
{
        unsigned long long sb_index = pos;
        unsigned long offset;

        offset = do_div(sb_index, blocksize);
        *pbh = sb_bread(sb, sb_index);
        if (!*pbh)
                return NULL;
        return (struct nilfs_super_block *)((char *)(*pbh)->b_data + offset);
}

int nilfs_store_magic(struct super_block *sb,
                      struct nilfs_super_block *sbp)
{
        struct the_nilfs *nilfs = sb->s_fs_info;

        sb->s_magic = le16_to_cpu(sbp->s_magic);

        /* FS independent flags */
#ifdef NILFS_ATIME_DISABLE
        sb->s_flags |= SB_NOATIME;
#endif

        nilfs->ns_resuid = le16_to_cpu(sbp->s_def_resuid);
        nilfs->ns_resgid = le16_to_cpu(sbp->s_def_resgid);
        nilfs->ns_interval = le32_to_cpu(sbp->s_c_interval);
        nilfs->ns_watermark = le32_to_cpu(sbp->s_c_block_max);

        return 0;
}

int nilfs_check_feature_compatibility(struct super_block *sb,
                                      struct nilfs_super_block *sbp)
{
        __u64 features;

        features = le64_to_cpu(sbp->s_feature_incompat) &
                ~NILFS_FEATURE_INCOMPAT_SUPP;
        if (features) {
                nilfs_err(sb,
                          "couldn't mount because of unsupported optional features (%llx)",
                          (unsigned long long)features);
                return -EINVAL;
        }
        features = le64_to_cpu(sbp->s_feature_compat_ro) &
                ~NILFS_FEATURE_COMPAT_RO_SUPP;
        if (!sb_rdonly(sb) && features) {
                nilfs_err(sb,
                          "couldn't mount RDWR because of unsupported optional features (%llx)",
                          (unsigned long long)features);
                return -EINVAL;
        }
        return 0;
}

static int nilfs_get_root_dentry(struct super_block *sb,
                                 struct nilfs_root *root,
                                 struct dentry **root_dentry)
{
        struct inode *inode;
        struct dentry *dentry;
        int ret = 0;

        inode = nilfs_iget(sb, root, NILFS_ROOT_INO);
        if (IS_ERR(inode)) {
                ret = PTR_ERR(inode);
                nilfs_err(sb, "error %d getting root inode", ret);
                goto out;
        }
        if (!S_ISDIR(inode->i_mode) || !inode->i_blocks || !inode->i_size) {
                iput(inode);
                nilfs_err(sb, "corrupt root inode");
                ret = -EINVAL;
                goto out;
        }

        if (root->cno == NILFS_CPTREE_CURRENT_CNO) {
                dentry = d_find_alias(inode);
                if (!dentry) {
                        dentry = d_make_root(inode);
                        if (!dentry) {
                                ret = -ENOMEM;
                                goto failed_dentry;
                        }
                } else {
                        iput(inode);
                }
        } else {
                dentry = d_obtain_root(inode);
                if (IS_ERR(dentry)) {
                        ret = PTR_ERR(dentry);
                        goto failed_dentry;
                }
        }
        *root_dentry = dentry;
 out:
        return ret;

 failed_dentry:
        nilfs_err(sb, "error %d getting root dentry", ret);
        goto out;
}

static int nilfs_attach_snapshot(struct super_block *s, __u64 cno,
                                 struct dentry **root_dentry)
{
        struct the_nilfs *nilfs = s->s_fs_info;
        struct nilfs_root *root;
        int ret;

        mutex_lock(&nilfs->ns_snapshot_mount_mutex);

        down_read(&nilfs->ns_segctor_sem);
        ret = nilfs_cpfile_is_snapshot(nilfs->ns_cpfile, cno);
        up_read(&nilfs->ns_segctor_sem);
        if (ret < 0) {
                ret = (ret == -ENOENT) ? -EINVAL : ret;
                goto out;
        } else if (!ret) {
                nilfs_err(s,
                          "The specified checkpoint is not a snapshot (checkpoint number=%llu)",
                          (unsigned long long)cno);
                ret = -EINVAL;
                goto out;
        }

        ret = nilfs_attach_checkpoint(s, cno, false, &root);
        if (ret) {
                nilfs_err(s,
                          "error %d while loading snapshot (checkpoint number=%llu)",
                          ret, (unsigned long long)cno);
                goto out;
        }
        ret = nilfs_get_root_dentry(s, root, root_dentry);
        nilfs_put_root(root);
 out:
        mutex_unlock(&nilfs->ns_snapshot_mount_mutex);
        return ret;
}

/**
 * nilfs_tree_is_busy() - try to shrink dentries of a checkpoint
 * @root_dentry: root dentry of the tree to be shrunk
 *
 * Return: true if the tree was in-use, false otherwise.
 */
static bool nilfs_tree_is_busy(struct dentry *root_dentry)
{
        shrink_dcache_parent(root_dentry);
        return d_count(root_dentry) > 1;
}

int nilfs_checkpoint_is_mounted(struct super_block *sb, __u64 cno)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        struct nilfs_root *root;
        struct inode *inode;
        struct dentry *dentry;
        int ret;

        if (cno > nilfs->ns_cno)
                return false;

        if (cno >= nilfs_last_cno(nilfs))
                return true;    /* protect recent checkpoints */

        ret = false;
        root = nilfs_lookup_root(nilfs, cno);
        if (root) {
                inode = nilfs_ilookup(sb, root, NILFS_ROOT_INO);
                if (inode) {
                        dentry = d_find_alias(inode);
                        if (dentry) {
                                ret = nilfs_tree_is_busy(dentry);
                                dput(dentry);
                        }
                        iput(inode);
                }
                nilfs_put_root(root);
        }
        return ret;
}

/**
 * nilfs_fill_super() - initialize a super block instance
 * @sb: super_block
 * @fc: filesystem context
 *
 * This function is called exclusively by nilfs->ns_mount_mutex.
 * So, the recovery process is protected from other simultaneous mounts.
 *
 * Return: 0 on success, or a negative error code on failure.
 */
static int
nilfs_fill_super(struct super_block *sb, struct fs_context *fc)
{
        struct the_nilfs *nilfs;
        struct nilfs_root *fsroot;
        struct nilfs_fs_context *ctx = fc->fs_private;
        __u64 cno;
        int err;

        nilfs = alloc_nilfs(sb);
        if (!nilfs)
                return -ENOMEM;

        sb->s_fs_info = nilfs;

        err = init_nilfs(nilfs, sb);
        if (err)
                goto failed_nilfs;

        /* Copy in parsed mount options */
        nilfs->ns_mount_opt = ctx->ns_mount_opt;

        sb->s_op = &nilfs_sops;
        sb->s_export_op = &nilfs_export_ops;
        sb->s_root = NULL;
        sb->s_time_gran = 1;
        sb->s_max_links = NILFS_LINK_MAX;

        sb->s_bdi = bdi_get(sb->s_bdev->bd_disk->bdi);

        err = load_nilfs(nilfs, sb);
        if (err)
                goto failed_nilfs;

        super_set_uuid(sb, nilfs->ns_sbp[0]->s_uuid,
                       sizeof(nilfs->ns_sbp[0]->s_uuid));
        super_set_sysfs_name_bdev(sb);

        cno = nilfs_last_cno(nilfs);
        err = nilfs_attach_checkpoint(sb, cno, true, &fsroot);
        if (err) {
                nilfs_err(sb,
                          "error %d while loading last checkpoint (checkpoint number=%llu)",
                          err, (unsigned long long)cno);
                goto failed_unload;
        }

        if (!sb_rdonly(sb)) {
                err = nilfs_attach_log_writer(sb, fsroot);
                if (err)
                        goto failed_checkpoint;
        }

        err = nilfs_get_root_dentry(sb, fsroot, &sb->s_root);
        if (err)
                goto failed_segctor;

        nilfs_put_root(fsroot);

        if (!sb_rdonly(sb)) {
                down_write(&nilfs->ns_sem);
                nilfs_setup_super(sb, true);
                up_write(&nilfs->ns_sem);
        }

        return 0;

 failed_segctor:
        nilfs_detach_log_writer(sb);

 failed_checkpoint:
        nilfs_put_root(fsroot);

 failed_unload:
        nilfs_sysfs_delete_device_group(nilfs);
        iput(nilfs->ns_sufile);
        iput(nilfs->ns_cpfile);
        iput(nilfs->ns_dat);

 failed_nilfs:
        destroy_nilfs(nilfs);
        return err;
}

static int nilfs_reconfigure(struct fs_context *fc)
{
        struct nilfs_fs_context *ctx = fc->fs_private;
        struct super_block *sb = fc->root->d_sb;
        struct the_nilfs *nilfs = sb->s_fs_info;
        int err;

        sync_filesystem(sb);

        err = -EINVAL;

        if (!nilfs_valid_fs(nilfs)) {
                nilfs_warn(sb,
                           "couldn't remount because the filesystem is in an incomplete recovery state");
                goto ignore_opts;
        }
        if ((bool)(fc->sb_flags & SB_RDONLY) == sb_rdonly(sb))
                goto out;
        if (fc->sb_flags & SB_RDONLY) {
                sb->s_flags |= SB_RDONLY;

                /*
                 * Remounting a valid RW partition RDONLY, so set
                 * the RDONLY flag and then mark the partition as valid again.
                 */
                down_write(&nilfs->ns_sem);
                nilfs_cleanup_super(sb);
                up_write(&nilfs->ns_sem);
        } else {
                __u64 features;
                struct nilfs_root *root;

                /*
                 * Mounting a RDONLY partition read-write, so reread and
                 * store the current valid flag.  (It may have been changed
                 * by fsck since we originally mounted the partition.)
                 */
                down_read(&nilfs->ns_sem);
                features = le64_to_cpu(nilfs->ns_sbp[0]->s_feature_compat_ro) &
                        ~NILFS_FEATURE_COMPAT_RO_SUPP;
                up_read(&nilfs->ns_sem);
                if (features) {
                        nilfs_warn(sb,
                                   "couldn't remount RDWR because of unsupported optional features (%llx)",
                                   (unsigned long long)features);
                        err = -EROFS;
                        goto ignore_opts;
                }

                sb->s_flags &= ~SB_RDONLY;

                root = NILFS_I(d_inode(sb->s_root))->i_root;
                err = nilfs_attach_log_writer(sb, root);
                if (err) {
                        sb->s_flags |= SB_RDONLY;
                        goto ignore_opts;
                }

                down_write(&nilfs->ns_sem);
                nilfs_setup_super(sb, true);
                up_write(&nilfs->ns_sem);
        }
 out:
        sb->s_flags = (sb->s_flags & ~SB_POSIXACL);
        /* Copy over parsed remount options */
        nilfs->ns_mount_opt = ctx->ns_mount_opt;

        return 0;

 ignore_opts:
        return err;
}

static int
nilfs_get_tree(struct fs_context *fc)
{
        struct nilfs_fs_context *ctx = fc->fs_private;
        struct super_block *s;
        dev_t dev;
        int err;

        if (ctx->cno && !(fc->sb_flags & SB_RDONLY)) {
                nilfs_err(NULL,
                          "invalid option \"cp=%llu\": read-only option is not specified",
                          ctx->cno);
                return -EINVAL;
        }

        err = lookup_bdev(fc->source, &dev);
        if (err)
                return err;

        s = sget_dev(fc, dev);
        if (IS_ERR(s))
                return PTR_ERR(s);

        if (!s->s_root) {
                err = setup_bdev_super(s, fc->sb_flags, fc);
                if (!err)
                        err = nilfs_fill_super(s, fc);
                if (err)
                        goto failed_super;

                s->s_flags |= SB_ACTIVE;
        } else if (!ctx->cno) {
                if (nilfs_tree_is_busy(s->s_root)) {
                        if ((fc->sb_flags ^ s->s_flags) & SB_RDONLY) {
                                nilfs_err(s,
                                          "the device already has a %s mount.",
                                          sb_rdonly(s) ? "read-only" : "read/write");
                                err = -EBUSY;
                                goto failed_super;
                        }
                } else {
                        /*
                         * Try reconfigure to setup mount states if the current
                         * tree is not mounted and only snapshots use this sb.
                         *
                         * Since nilfs_reconfigure() requires fc->root to be
                         * set, set it first and release it on failure.
                         */
                        fc->root = dget(s->s_root);
                        err = nilfs_reconfigure(fc);
                        if (err) {
                                dput(fc->root);
                                fc->root = NULL;  /* prevent double release */
                                goto failed_super;
                        }
                        return 0;
                }
        }

        if (ctx->cno) {
                struct dentry *root_dentry;

                err = nilfs_attach_snapshot(s, ctx->cno, &root_dentry);
                if (err)
                        goto failed_super;
                fc->root = root_dentry;
                return 0;
        }

        fc->root = dget(s->s_root);
        return 0;

 failed_super:
        deactivate_locked_super(s);
        return err;
}

static void nilfs_free_fc(struct fs_context *fc)
{
        kfree(fc->fs_private);
}

static const struct fs_context_operations nilfs_context_ops = {
        .parse_param    = nilfs_parse_param,
        .get_tree       = nilfs_get_tree,
        .reconfigure    = nilfs_reconfigure,
        .free           = nilfs_free_fc,
};

static int nilfs_init_fs_context(struct fs_context *fc)
{
        struct nilfs_fs_context *ctx;

        ctx = kzalloc_obj(*ctx);
        if (!ctx)
                return -ENOMEM;

        ctx->ns_mount_opt = NILFS_MOUNT_ERRORS_RO | NILFS_MOUNT_BARRIER;
        fc->fs_private = ctx;
        fc->ops = &nilfs_context_ops;

        return 0;
}

struct file_system_type nilfs_fs_type = {
        .owner    = THIS_MODULE,
        .name     = "nilfs2",
        .kill_sb  = kill_block_super,
        .fs_flags = FS_REQUIRES_DEV,
        .init_fs_context = nilfs_init_fs_context,
        .parameters = nilfs_param_spec,
};
MODULE_ALIAS_FS("nilfs2");

static void nilfs_inode_init_once(void *obj)
{
        struct nilfs_inode_info *ii = obj;

        INIT_LIST_HEAD(&ii->i_dirty);
#ifdef CONFIG_NILFS_XATTR
        init_rwsem(&ii->xattr_sem);
#endif
        inode_init_once(&ii->vfs_inode);
}

static void nilfs_segbuf_init_once(void *obj)
{
        memset(obj, 0, sizeof(struct nilfs_segment_buffer));
}

static void nilfs_destroy_cachep(void)
{
        /*
         * Make sure all delayed rcu free inodes are flushed before we
         * destroy cache.
         */
        rcu_barrier();

        kmem_cache_destroy(nilfs_inode_cachep);
        kmem_cache_destroy(nilfs_transaction_cachep);
        kmem_cache_destroy(nilfs_segbuf_cachep);
        kmem_cache_destroy(nilfs_btree_path_cache);
}

static int __init nilfs_init_cachep(void)
{
        nilfs_inode_cachep = kmem_cache_create("nilfs2_inode_cache",
                        sizeof(struct nilfs_inode_info), 0,
                        SLAB_RECLAIM_ACCOUNT|SLAB_ACCOUNT,
                        nilfs_inode_init_once);
        if (!nilfs_inode_cachep)
                goto fail;

        nilfs_transaction_cachep = kmem_cache_create("nilfs2_transaction_cache",
                        sizeof(struct nilfs_transaction_info), 0,
                        SLAB_RECLAIM_ACCOUNT, NULL);
        if (!nilfs_transaction_cachep)
                goto fail;

        nilfs_segbuf_cachep = kmem_cache_create("nilfs2_segbuf_cache",
                        sizeof(struct nilfs_segment_buffer), 0,
                        SLAB_RECLAIM_ACCOUNT, nilfs_segbuf_init_once);
        if (!nilfs_segbuf_cachep)
                goto fail;

        nilfs_btree_path_cache = kmem_cache_create("nilfs2_btree_path_cache",
                        sizeof(struct nilfs_btree_path) * NILFS_BTREE_LEVEL_MAX,
                        0, 0, NULL);
        if (!nilfs_btree_path_cache)
                goto fail;

        return 0;

fail:
        nilfs_destroy_cachep();
        return -ENOMEM;
}

static int __init init_nilfs_fs(void)
{
        int err;

        err = nilfs_init_cachep();
        if (err)
                goto fail;

        err = nilfs_sysfs_init();
        if (err)
                goto free_cachep;

        err = register_filesystem(&nilfs_fs_type);
        if (err)
                goto deinit_sysfs_entry;

        printk(KERN_INFO "NILFS version 2 loaded\n");
        return 0;

deinit_sysfs_entry:
        nilfs_sysfs_exit();
free_cachep:
        nilfs_destroy_cachep();
fail:
        return err;
}

static void __exit exit_nilfs_fs(void)
{
        nilfs_destroy_cachep();
        nilfs_sysfs_exit();
        unregister_filesystem(&nilfs_fs_type);
}

module_init(init_nilfs_fs)
module_exit(exit_nilfs_fs)