From: "zhangyi (F)" yi.zhang@huawei.com
mainline inclusion from mainline-v5.9-rc2 commit bc71726c725767205757821df364acff87f92ac5 category: bugfix bugzilla: 34540 CVE: NA ---------------------------
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
Conflict: fs/ext4/super.c fs/ext4/ext4_jbd2.c
Signed-off-by: zhangyi (F) yi.zhang@huawei.com Reviewed-by: Yang Erkun yangerkun@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- fs/ext4/ext4.h | 4 ++++ fs/ext4/ext4_jbd2.c | 24 ++++++++++++++++++++++++ fs/ext4/super.c | 17 +++++++++++++++++ 3 files changed, 45 insertions(+)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 4491b9911807c..03cf8faf51b9f 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -1535,6 +1535,10 @@ struct ext4_sb_info { */ struct percpu_rw_semaphore s_writepages_rwsem; struct dax_device *s_daxdev; + + /* 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) diff --git a/fs/ext4/ext4_jbd2.c b/fs/ext4/ext4_jbd2.c index d3b8cdea5df75..2048e30db852a 100644 --- a/fs/ext4/ext4_jbd2.c +++ b/fs/ext4/ext4_jbd2.c @@ -173,6 +173,27 @@ 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(sb, "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) { @@ -180,6 +201,9 @@ 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) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index b6b6a25cce081..170542479954e 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -4591,6 +4591,15 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) } #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; @@ -5438,6 +5447,14 @@ 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