Commit bc71726c authored by zhangyi (F)'s avatar zhangyi (F) Committed by Theodore Ts'o
Browse files

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: default avatarzhangyi (F) <yi.zhang@huawei.com>
Suggested-by: default avatarJan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20200620025427.1756360-2-yi.zhang@huawei.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent c1d2c7d4

fs/ext4/ext4.h

+3 −0
Original line number Diff line number Diff line
@@ -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)

fs/ext4/ext4_jbd2.c

+25 −0
Original line number Diff line number Diff line
@@ -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)

fs/ext4/super.c

+17 −0
Original line number Diff line number Diff line
@@ -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

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