// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2012-2013 Samsung Electronics Co., Ltd.
 */

#include <linux/init.h>
#include <linux/buffer_head.h>
#include <linux/mpage.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/time.h>
#include <linux/writeback.h>
#include <linux/uio.h>
#include <linux/random.h>
#include <linux/iversion.h>

#include "exfat_raw.h"
#include "exfat_fs.h"

int __exfat_write_inode(struct inode *inode, int sync)
{
        unsigned long long on_disk_size;
        struct exfat_dentry *ep, *ep2;
        struct exfat_entry_set_cache es;
        struct super_block *sb = inode->i_sb;
        struct exfat_sb_info *sbi = EXFAT_SB(sb);
        struct exfat_inode_info *ei = EXFAT_I(inode);
        bool is_dir = (ei->type == TYPE_DIR);
        struct timespec64 ts;

        if (inode->i_ino == EXFAT_ROOT_INO)
                return 0;

        /*
         * If the inode is already unlinked, there is no need for updating it.
         */
        if (ei->dir.dir == DIR_DELETED)
                return 0;

        if (is_dir && ei->dir.dir == sbi->root_dir && ei->entry == -1)
                return 0;

        exfat_set_volume_dirty(sb);

        /* get the directory entry of given file or directory */
        if (exfat_get_dentry_set_by_ei(&es, sb, ei))
                return -EIO;
        ep = exfat_get_dentry_cached(&es, ES_IDX_FILE);
        ep2 = exfat_get_dentry_cached(&es, ES_IDX_STREAM);

        ep->dentry.file.attr = cpu_to_le16(exfat_make_attr(inode));

        /* set FILE_INFO structure using the acquired struct exfat_dentry */
        exfat_set_entry_time(sbi, &ei->i_crtime,
                        &ep->dentry.file.create_tz,
                        &ep->dentry.file.create_time,
                        &ep->dentry.file.create_date,
                        &ep->dentry.file.create_time_cs);
        ts = inode_get_mtime(inode);
        exfat_set_entry_time(sbi, &ts,
                             &ep->dentry.file.modify_tz,
                             &ep->dentry.file.modify_time,
                             &ep->dentry.file.modify_date,
                             &ep->dentry.file.modify_time_cs);
        ts = inode_get_atime(inode);
        exfat_set_entry_time(sbi, &ts,
                             &ep->dentry.file.access_tz,
                             &ep->dentry.file.access_time,
                             &ep->dentry.file.access_date,
                             NULL);

        /* File size should be zero if there is no cluster allocated */
        on_disk_size = i_size_read(inode);

        if (ei->start_clu == EXFAT_EOF_CLUSTER)
                on_disk_size = 0;

        ep2->dentry.stream.size = cpu_to_le64(on_disk_size);
        /*
         * mmap write does not use exfat_write_end(), valid_size may be
         * extended to the sector-aligned length in exfat_get_block().
         * So we need to fixup valid_size to the writren length.
         */
        if (on_disk_size < ei->valid_size)
                ep2->dentry.stream.valid_size = ep2->dentry.stream.size;
        else
                ep2->dentry.stream.valid_size = cpu_to_le64(ei->valid_size);

        if (on_disk_size) {
                ep2->dentry.stream.flags = ei->flags;
                ep2->dentry.stream.start_clu = cpu_to_le32(ei->start_clu);
        } else {
                ep2->dentry.stream.flags = ALLOC_FAT_CHAIN;
                ep2->dentry.stream.start_clu = EXFAT_FREE_CLUSTER;
        }

        exfat_update_dir_chksum(&es);
        return exfat_put_dentry_set(&es, sync);
}

int exfat_write_inode(struct inode *inode, struct writeback_control *wbc)
{
        int ret;

        if (unlikely(exfat_forced_shutdown(inode->i_sb)))
                return -EIO;

        mutex_lock(&EXFAT_SB(inode->i_sb)->s_lock);
        ret = __exfat_write_inode(inode, wbc->sync_mode == WB_SYNC_ALL);
        mutex_unlock(&EXFAT_SB(inode->i_sb)->s_lock);

        return ret;
}

void exfat_sync_inode(struct inode *inode)
{
        lockdep_assert_held(&EXFAT_SB(inode->i_sb)->s_lock);
        __exfat_write_inode(inode, 1);
}

/*
 * Input: inode, (logical) clu_offset, target allocation area
 * Output: errcode, cluster number
 * *clu = (~0), if it's unable to allocate a new cluster
 */
static int exfat_map_cluster(struct inode *inode, unsigned int clu_offset,
                unsigned int *clu, unsigned int *count, int create)
{
        int ret;
        unsigned int last_clu;
        struct exfat_chain new_clu;
        struct super_block *sb = inode->i_sb;
        struct exfat_sb_info *sbi = EXFAT_SB(sb);
        struct exfat_inode_info *ei = EXFAT_I(inode);
        unsigned int local_clu_offset = clu_offset;
        unsigned int num_to_be_allocated = 0, num_clusters;

        num_clusters = EXFAT_B_TO_CLU(exfat_ondisk_size(inode), sbi);

        if (clu_offset >= num_clusters)
                num_to_be_allocated = clu_offset - num_clusters + 1;

        if (!create && (num_to_be_allocated > 0)) {
                *clu = EXFAT_EOF_CLUSTER;
                return 0;
        }

        *clu = last_clu = ei->start_clu;

        if (*clu == EXFAT_EOF_CLUSTER) {
                *count = 0;
        } else if (ei->flags == ALLOC_NO_FAT_CHAIN) {
                last_clu += num_clusters - 1;
                if (clu_offset < num_clusters) {
                        *clu += clu_offset;
                        *count = min(num_clusters - clu_offset, *count);
                } else {
                        *clu = EXFAT_EOF_CLUSTER;
                        *count = 0;
                }
        } else {
                int err = exfat_get_cluster(inode, clu_offset,
                                clu, count, &last_clu);
                if (err)
                        return -EIO;
        }

        if (*clu == EXFAT_EOF_CLUSTER) {
                exfat_set_volume_dirty(sb);

                new_clu.dir = (last_clu == EXFAT_EOF_CLUSTER) ?
                                EXFAT_EOF_CLUSTER : last_clu + 1;
                new_clu.size = 0;
                new_clu.flags = ei->flags;

                /* allocate a cluster */
                if (num_to_be_allocated < 1) {
                        /* Broken FAT (i_sze > allocated FAT) */
                        exfat_fs_error(sb, "broken FAT chain.");
                        return -EIO;
                }

                ret = exfat_alloc_cluster(inode, num_to_be_allocated, &new_clu,
                                inode_needs_sync(inode));
                if (ret)
                        return ret;

                if (new_clu.dir == EXFAT_EOF_CLUSTER ||
                    new_clu.dir == EXFAT_FREE_CLUSTER) {
                        exfat_fs_error(sb,
                                "bogus cluster new allocated (last_clu : %u, new_clu : %u)",
                                last_clu, new_clu.dir);
                        return -EIO;
                }

                /* append to the FAT chain */
                if (last_clu == EXFAT_EOF_CLUSTER) {
                        if (new_clu.flags == ALLOC_FAT_CHAIN)
                                ei->flags = ALLOC_FAT_CHAIN;
                        ei->start_clu = new_clu.dir;
                } else {
                        if (new_clu.flags != ei->flags) {
                                /* no-fat-chain bit is disabled,
                                 * so fat-chain should be synced with
                                 * alloc-bitmap
                                 */
                                exfat_chain_cont_cluster(sb, ei->start_clu,
                                        num_clusters);
                                ei->flags = ALLOC_FAT_CHAIN;
                        }
                        if (new_clu.flags == ALLOC_FAT_CHAIN)
                                if (exfat_ent_set(sb, last_clu, new_clu.dir))
                                        return -EIO;
                }

                num_clusters += num_to_be_allocated;
                *clu = new_clu.dir;

                inode->i_blocks += EXFAT_CLU_TO_B(num_to_be_allocated, sbi) >> 9;

                /*
                 * Move *clu pointer along FAT chains (hole care) because the
                 * caller of this function expect *clu to be the last cluster.
                 * This only works when num_to_be_allocated >= 2,
                 * *clu = (the first cluster of the allocated chain) =>
                 * (the last cluster of ...)
                 */
                if (ei->flags == ALLOC_NO_FAT_CHAIN) {
                        *clu += num_to_be_allocated - 1;
                } else {
                        while (num_to_be_allocated > 1) {
                                if (exfat_get_next_cluster(sb, clu))
                                        return -EIO;
                                num_to_be_allocated--;
                        }
                }
                *count = 1;
        }

        /* hint information */
        ei->hint_bmap.off = local_clu_offset;
        ei->hint_bmap.clu = *clu;

        return 0;
}

static int exfat_get_block(struct inode *inode, sector_t iblock,
                struct buffer_head *bh_result, int create)
{
        struct exfat_inode_info *ei = EXFAT_I(inode);
        struct super_block *sb = inode->i_sb;
        struct exfat_sb_info *sbi = EXFAT_SB(sb);
        unsigned long max_blocks = bh_result->b_size >> inode->i_blkbits;
        int err = 0;
        unsigned long mapped_blocks = 0;
        unsigned int cluster, sec_offset, count;
        sector_t last_block;
        sector_t phys = 0;
        sector_t valid_blks;
        loff_t i_size;

        mutex_lock(&sbi->s_lock);
        i_size = i_size_read(inode);
        last_block = EXFAT_B_TO_BLK_ROUND_UP(i_size, sb);
        if (iblock >= last_block && !create)
                goto done;

        /* Is this block already allocated? */
        count = EXFAT_B_TO_CLU_ROUND_UP(bh_result->b_size, sbi);
        err = exfat_map_cluster(inode, iblock >> sbi->sect_per_clus_bits,
                        &cluster, &count, create);
        if (err) {
                if (err != -ENOSPC)
                        exfat_fs_error_ratelimit(sb,
                                "failed to bmap (inode : %p iblock : %llu, err : %d)",
                                inode, (unsigned long long)iblock, err);
                goto unlock_ret;
        }

        if (cluster == EXFAT_EOF_CLUSTER)
                goto done;

        /* sector offset in cluster */
        sec_offset = iblock & (sbi->sect_per_clus - 1);

        phys = exfat_cluster_to_sector(sbi, cluster) + sec_offset;
        mapped_blocks = ((unsigned long)count << sbi->sect_per_clus_bits) - sec_offset;
        max_blocks = min(mapped_blocks, max_blocks);

        map_bh(bh_result, sb, phys);
        if (buffer_delay(bh_result))
                clear_buffer_delay(bh_result);

        /*
         * In most cases, we just need to set bh_result to mapped, unmapped
         * or new status as follows:
         *  1. i_size == valid_size
         *  2. write case (create == 1)
         *  3. direct_read (!bh_result->b_folio)
         *     -> the unwritten part will be zeroed in exfat_direct_IO()
         *
         * Otherwise, in the case of buffered read, it is necessary to take
         * care the last nested block if valid_size is not equal to i_size.
         */
        if (i_size == ei->valid_size || create || !bh_result->b_folio)
                valid_blks = EXFAT_B_TO_BLK_ROUND_UP(ei->valid_size, sb);
        else
                valid_blks = EXFAT_B_TO_BLK(ei->valid_size, sb);

        /* The range has been fully written, map it */
        if (iblock + max_blocks < valid_blks)
                goto done;

        /* The range has been partially written, map the written part */
        if (iblock < valid_blks) {
                max_blocks = valid_blks - iblock;
                goto done;
        }

        /* The area has not been written, map and mark as new for create case */
        if (create) {
                set_buffer_new(bh_result);
                ei->valid_size = EXFAT_BLK_TO_B(iblock + max_blocks, sb);
                mark_inode_dirty(inode);
                goto done;
        }

        /*
         * The area has just one block partially written.
         * In that case, we should read and fill the unwritten part of
         * a block with zero.
         */
        if (bh_result->b_folio && iblock == valid_blks &&
            (ei->valid_size & (sb->s_blocksize - 1))) {
                loff_t size, pos;
                void *addr;

                max_blocks = 1;

                /*
                 * No buffer_head is allocated.
                 * (1) bmap: It's enough to set blocknr without I/O.
                 * (2) read: The unwritten part should be filled with zero.
                 *           If a folio does not have any buffers,
                 *           let's returns -EAGAIN to fallback to
                 *           block_read_full_folio() for per-bh IO.
                 */
                if (!folio_buffers(bh_result->b_folio)) {
                        err = -EAGAIN;
                        goto done;
                }

                pos = EXFAT_BLK_TO_B(iblock, sb);
                size = ei->valid_size - pos;
                addr = folio_address(bh_result->b_folio) +
                        offset_in_folio(bh_result->b_folio, pos);

                /* Check if bh->b_data points to proper addr in folio */
                if (bh_result->b_data != addr) {
                        exfat_fs_error_ratelimit(sb,
                                        "b_data(%p) != folio_addr(%p)",
                                        bh_result->b_data, addr);
                        err = -EINVAL;
                        goto done;
                }

                /* Read a block */
                err = bh_read(bh_result, 0);
                if (err < 0)
                        goto done;

                /* Zero unwritten part of a block */
                memset(bh_result->b_data + size, 0, bh_result->b_size - size);
                err = 0;
                goto done;
        }

        /*
         * The area has not been written, clear mapped for read/bmap cases.
         * If so, it will be filled with zero without reading from disk.
         */
        clear_buffer_mapped(bh_result);
done:
        bh_result->b_size = EXFAT_BLK_TO_B(max_blocks, sb);
        if (err < 0)
                clear_buffer_mapped(bh_result);
unlock_ret:
        mutex_unlock(&sbi->s_lock);
        return err;
}

static int exfat_read_folio(struct file *file, struct folio *folio)
{
        return mpage_read_folio(folio, exfat_get_block);
}

static void exfat_readahead(struct readahead_control *rac)
{
        struct address_space *mapping = rac->mapping;
        struct inode *inode = mapping->host;
        struct exfat_inode_info *ei = EXFAT_I(inode);
        loff_t pos = readahead_pos(rac);

        /* Range cross valid_size, read it page by page. */
        if (ei->valid_size < i_size_read(inode) &&
            pos <= ei->valid_size &&
            ei->valid_size < pos + readahead_length(rac))
                return;

        mpage_readahead(rac, exfat_get_block);
}

static int exfat_writepages(struct address_space *mapping,
                struct writeback_control *wbc)
{
        if (unlikely(exfat_forced_shutdown(mapping->host->i_sb)))
                return -EIO;

        return mpage_writepages(mapping, wbc, exfat_get_block);
}

static void exfat_write_failed(struct address_space *mapping, loff_t to)
{
        struct inode *inode = mapping->host;

        if (to > i_size_read(inode)) {
                truncate_pagecache(inode, i_size_read(inode));
                inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
                exfat_truncate(inode);
        }
}

static int exfat_write_begin(const struct kiocb *iocb,
                             struct address_space *mapping,
                             loff_t pos, unsigned int len,
                             struct folio **foliop, void **fsdata)
{
        int ret;

        if (unlikely(exfat_forced_shutdown(mapping->host->i_sb)))
                return -EIO;

        ret = block_write_begin(mapping, pos, len, foliop, exfat_get_block);

        if (ret < 0)
                exfat_write_failed(mapping, pos+len);

        return ret;
}

static int exfat_write_end(const struct kiocb *iocb,
                           struct address_space *mapping,
                           loff_t pos, unsigned int len, unsigned int copied,
                           struct folio *folio, void *fsdata)
{
        struct inode *inode = mapping->host;
        struct exfat_inode_info *ei = EXFAT_I(inode);
        int err;

        err = generic_write_end(iocb, mapping, pos, len, copied, folio, fsdata);
        if (err < len)
                exfat_write_failed(mapping, pos+len);

        if (!(err < 0) && pos + err > ei->valid_size) {
                ei->valid_size = pos + err;
                mark_inode_dirty(inode);
        }

        if (!(err < 0) && !(ei->attr & EXFAT_ATTR_ARCHIVE)) {
                inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
                ei->attr |= EXFAT_ATTR_ARCHIVE;
                mark_inode_dirty(inode);
        }

        return err;
}

static ssize_t exfat_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
{
        struct address_space *mapping = iocb->ki_filp->f_mapping;
        struct inode *inode = mapping->host;
        struct exfat_inode_info *ei = EXFAT_I(inode);
        loff_t pos = iocb->ki_pos;
        loff_t size = pos + iov_iter_count(iter);
        int rw = iov_iter_rw(iter);
        ssize_t ret;

        /*
         * Need to use the DIO_LOCKING for avoiding the race
         * condition of exfat_get_block() and ->truncate().
         */
        ret = blockdev_direct_IO(iocb, inode, iter, exfat_get_block);
        if (ret < 0) {
                if (rw == WRITE && ret != -EIOCBQUEUED)
                        exfat_write_failed(mapping, size);

                return ret;
        }

        size = pos + ret;

        if (rw == WRITE) {
                /*
                 * If the block had been partially written before this write,
                 * ->valid_size will not be updated in exfat_get_block(),
                 * update it here.
                 */
                if (ei->valid_size < size) {
                        ei->valid_size = size;
                        mark_inode_dirty(inode);
                }
        } else if (pos < ei->valid_size && ei->valid_size < size) {
                /* zero the unwritten part in the partially written block */
                iov_iter_revert(iter, size - ei->valid_size);
                iov_iter_zero(size - ei->valid_size, iter);
        }

        return ret;
}

static sector_t exfat_aop_bmap(struct address_space *mapping, sector_t block)
{
        sector_t blocknr;

        /* exfat_get_cluster() assumes the requested blocknr isn't truncated. */
        down_read(&EXFAT_I(mapping->host)->truncate_lock);
        blocknr = generic_block_bmap(mapping, block, exfat_get_block);
        up_read(&EXFAT_I(mapping->host)->truncate_lock);
        return blocknr;
}

/*
 * exfat_block_truncate_page() zeroes out a mapping from file offset `from'
 * up to the end of the block which corresponds to `from'.
 * This is required during truncate to physically zeroout the tail end
 * of that block so it doesn't yield old data if the file is later grown.
 * Also, avoid causing failure from fsx for cases of "data past EOF"
 */
int exfat_block_truncate_page(struct inode *inode, loff_t from)
{
        return block_truncate_page(inode->i_mapping, from, exfat_get_block);
}

static const struct address_space_operations exfat_aops = {
        .dirty_folio    = block_dirty_folio,
        .invalidate_folio = block_invalidate_folio,
        .read_folio     = exfat_read_folio,
        .readahead      = exfat_readahead,
        .writepages     = exfat_writepages,
        .write_begin    = exfat_write_begin,
        .write_end      = exfat_write_end,
        .direct_IO      = exfat_direct_IO,
        .bmap           = exfat_aop_bmap,
        .migrate_folio  = buffer_migrate_folio,
};

static inline unsigned long exfat_hash(loff_t i_pos)
{
        return hash_32(i_pos, EXFAT_HASH_BITS);
}

void exfat_hash_inode(struct inode *inode, loff_t i_pos)
{
        struct exfat_sb_info *sbi = EXFAT_SB(inode->i_sb);
        struct hlist_head *head = sbi->inode_hashtable + exfat_hash(i_pos);

        spin_lock(&sbi->inode_hash_lock);
        EXFAT_I(inode)->i_pos = i_pos;
        hlist_add_head(&EXFAT_I(inode)->i_hash_fat, head);
        spin_unlock(&sbi->inode_hash_lock);
}

void exfat_unhash_inode(struct inode *inode)
{
        struct exfat_sb_info *sbi = EXFAT_SB(inode->i_sb);

        spin_lock(&sbi->inode_hash_lock);
        hlist_del_init(&EXFAT_I(inode)->i_hash_fat);
        EXFAT_I(inode)->i_pos = 0;
        spin_unlock(&sbi->inode_hash_lock);
}

struct inode *exfat_iget(struct super_block *sb, loff_t i_pos)
{
        struct exfat_sb_info *sbi = EXFAT_SB(sb);
        struct exfat_inode_info *info;
        struct hlist_head *head = sbi->inode_hashtable + exfat_hash(i_pos);
        struct inode *inode = NULL;

        spin_lock(&sbi->inode_hash_lock);
        hlist_for_each_entry(info, head, i_hash_fat) {
                WARN_ON(info->vfs_inode.i_sb != sb);

                if (i_pos != info->i_pos)
                        continue;
                inode = igrab(&info->vfs_inode);
                if (inode)
                        break;
        }
        spin_unlock(&sbi->inode_hash_lock);
        return inode;
}

/* doesn't deal with root inode */
static int exfat_fill_inode(struct inode *inode, struct exfat_dir_entry *info)
{
        struct exfat_sb_info *sbi = EXFAT_SB(inode->i_sb);
        struct exfat_inode_info *ei = EXFAT_I(inode);
        loff_t size = info->size;

        ei->dir = info->dir;
        ei->entry = info->entry;
        ei->attr = info->attr;
        ei->start_clu = info->start_clu;
        ei->flags = info->flags;
        ei->type = info->type;
        ei->valid_size = info->valid_size;

        ei->version = 0;
        ei->hint_stat.eidx = 0;
        ei->hint_stat.clu = info->start_clu;
        ei->hint_femp.eidx = EXFAT_HINT_NONE;
        ei->hint_bmap.off = EXFAT_EOF_CLUSTER;
        ei->i_pos = 0;

        inode->i_uid = sbi->options.fs_uid;
        inode->i_gid = sbi->options.fs_gid;
        inode_inc_iversion(inode);
        inode->i_generation = get_random_u32();

        if (info->attr & EXFAT_ATTR_SUBDIR) { /* directory */
                inode->i_generation &= ~1;
                inode->i_mode = exfat_make_mode(sbi, info->attr, 0777);
                inode->i_op = &exfat_dir_inode_operations;
                inode->i_fop = &exfat_dir_operations;
                set_nlink(inode, info->num_subdirs);
        } else { /* regular file */
                inode->i_generation |= 1;
                inode->i_mode = exfat_make_mode(sbi, info->attr, 0777);
                inode->i_op = &exfat_file_inode_operations;
                inode->i_fop = &exfat_file_operations;
                inode->i_mapping->a_ops = &exfat_aops;
                inode->i_mapping->nrpages = 0;
        }

        i_size_write(inode, size);

        exfat_save_attr(inode, info->attr);

        inode->i_blocks = round_up(i_size_read(inode), sbi->cluster_size) >> 9;
        inode_set_mtime_to_ts(inode, info->mtime);
        inode_set_ctime_to_ts(inode, info->mtime);
        ei->i_crtime = info->crtime;
        inode_set_atime_to_ts(inode, info->atime);

        return 0;
}

struct inode *exfat_build_inode(struct super_block *sb,
                struct exfat_dir_entry *info, loff_t i_pos)
{
        struct inode *inode;
        int err;

        inode = exfat_iget(sb, i_pos);
        if (inode)
                goto out;
        inode = new_inode(sb);
        if (!inode) {
                inode = ERR_PTR(-ENOMEM);
                goto out;
        }
        inode->i_ino = iunique(sb, EXFAT_ROOT_INO);
        inode_set_iversion(inode, 1);
        err = exfat_fill_inode(inode, info);
        if (err) {
                iput(inode);
                inode = ERR_PTR(err);
                goto out;
        }
        exfat_hash_inode(inode, i_pos);
        insert_inode_hash(inode);
out:
        return inode;
}

void exfat_evict_inode(struct inode *inode)
{
        truncate_inode_pages(&inode->i_data, 0);

        if (!inode->i_nlink) {
                i_size_write(inode, 0);
                mutex_lock(&EXFAT_SB(inode->i_sb)->s_lock);
                __exfat_truncate(inode);
                mutex_unlock(&EXFAT_SB(inode->i_sb)->s_lock);
        }

        invalidate_inode_buffers(inode);
        clear_inode(inode);
        exfat_cache_inval_inode(inode);
        exfat_unhash_inode(inode);
}