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ext4: abort the filesystem if failed to async write metadata buffer 

There is a risk of filesystem inconsistency if we failed to async write
back metadata buffer in the background. Because of current buffer's end
io procedure is handled by end_buffer_async_write() in the block layer,
and it only clear the buffer's uptodate flag and mark the write_io_error
flag, so ext4 cannot detect such failure immediately. In most cases of
getting metadata buffer (e.g. ext4_read_inode_bitmap()), although the
buffer's data is actually uptodate, it may still read data from disk
because the buffer's uptodate flag has been cleared. Finally, it may
lead to on-disk filesystem inconsistency if reading old data from the
disk successfully and write them out again.

This patch detect bdev mapping->wb_err when getting journal's write
access and mark the filesystem error if bdev's mapping->wb_err was
increased, this could prevent further writing and potential
inconsistency.

Signed-off-by: zhangyi (F) <yi.zhang@huawei.com>
Suggested-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20200620025427.1756360-2-yi.zhang@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
zhangyi (F) 2020-06-20 10:54:23 +08:00 committed by Theodore Ts'o
parent c1d2c7d47e
commit bc71726c72
3 changed files with 45 additions and 0 deletions
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3
fs/ext4/ext4.h
View File

@ -1603,6 +1603,9 @@ struct ext4_sb_info {
#ifdef CONFIG_EXT4_DEBUG
unsigned long s_simulate_fail;
#endif
/* Record the errseq of the backing block device */
errseq_t s_bdev_wb_err;
spinlock_t s_bdev_wb_lock;
};
static inline struct ext4_sb_info *EXT4_SB(struct super_block *sb)

25
fs/ext4/ext4_jbd2.c
View File

@ -195,6 +195,28 @@ static void ext4_journal_abort_handle(const char *caller, unsigned int line,
jbd2_journal_abort_handle(handle);
}
static void ext4_check_bdev_write_error(struct super_block *sb)
{
struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
struct ext4_sb_info *sbi = EXT4_SB(sb);
int err;
/*
* If the block device has write error flag, it may have failed to
* async write out metadata buffers in the background. In this case,
* we could read old data from disk and write it out again, which
* may lead to on-disk filesystem inconsistency.
*/
if (errseq_check(&mapping->wb_err, READ_ONCE(sbi->s_bdev_wb_err))) {
spin_lock(&sbi->s_bdev_wb_lock);
err = errseq_check_and_advance(&mapping->wb_err, &sbi->s_bdev_wb_err);
spin_unlock(&sbi->s_bdev_wb_lock);
if (err)
ext4_error_err(sb, -err,
"Error while async write back metadata");
}
}
int __ext4_journal_get_write_access(const char *where, unsigned int line,
handle_t *handle, struct buffer_head *bh)
{
@ -202,6 +224,9 @@ int __ext4_journal_get_write_access(const char *where, unsigned int line,
might_sleep();
if (bh->b_bdev->bd_super)
ext4_check_bdev_write_error(bh->b_bdev->bd_super);
if (ext4_handle_valid(handle)) {
err = jbd2_journal_get_write_access(handle, bh);
if (err)

17
fs/ext4/super.c
View File

@ -4765,6 +4765,15 @@ no_journal:
}
#endif /* CONFIG_QUOTA */
/*
* Save the original bdev mapping's wb_err value which could be
* used to detect the metadata async write error.
*/
spin_lock_init(&sbi->s_bdev_wb_lock);
if (!sb_rdonly(sb))
errseq_check_and_advance(&sb->s_bdev->bd_inode->i_mapping->wb_err,
&sbi->s_bdev_wb_err);
sb->s_bdev->bd_super = sb;
EXT4_SB(sb)->s_mount_state |= EXT4_ORPHAN_FS;
ext4_orphan_cleanup(sb, es);
EXT4_SB(sb)->s_mount_state &= ~EXT4_ORPHAN_FS;
@ -5654,6 +5663,14 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
goto restore_opts;
}
/*
* Update the original bdev mapping's wb_err value
* which could be used to detect the metadata async
* write error.
*/
errseq_check_and_advance(&sb->s_bdev->bd_inode->i_mapping->wb_err,
&sbi->s_bdev_wb_err);
/*
* Mounting a RDONLY partition read-write, so reread
* and store the current valid flag. (It may have