[PATCH v2] ext4: Fix bdev write error check failed when mount fs with ro

[PATCH v2] ext4: Fix bdev write error check failed when mount fs with ro

[Zhang Xiaoxu]

If some errors has occurred on the device, and the orphan list not empty,
then mount the device with 'ro', the bdev write error check will failed:
  ext4_check_bdev_write_error:193: comm mount: Error while async write back metadata

Since the sbi->s_bdev_wb_err wouldn't be initialized when mount file system
with 'ro', when clean up the orphan list and access the iloc buffer, bdev
write error check will failed.

So we should always initialize the sbi->s_bdev_wb_err even if mount the
file system with 'ro'.

Fixes: bc71726c7257 ("ext4: abort the filesystem if failed to async write metadata buffer")
Signed-off-by: Zhang Xiaoxu <zhangxiaoxu5@huawei.com>
---
 fs/ext4/super.c | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index ea425b49b345..0303e6e17190 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4814,9 +4814,8 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	 * 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);
+	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);
@@ -5707,14 +5706,6 @@ 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
-- 
2.25.4

Re: [PATCH v2] ext4: Fix bdev write error check failed when mount fs with ro

[Jan Kara]

On Thu 24-09-20 21:01:42, Zhang Xiaoxu wrote:
> If some errors has occurred on the device, and the orphan list not empty,
> then mount the device with 'ro', the bdev write error check will failed:
>   ext4_check_bdev_write_error:193: comm mount: Error while async write back metadata
> 
> Since the sbi->s_bdev_wb_err wouldn't be initialized when mount file system
> with 'ro', when clean up the orphan list and access the iloc buffer, bdev
> write error check will failed.
>
> So we should always initialize the sbi->s_bdev_wb_err even if mount the
> file system with 'ro'.

Let me rephrase the changelog a little bit for better readability:

Consider a situation when a filesystem was uncleanly shutdown and the orphan
list is not empty and a read-only mount is attempted. The orphan list
cleanup during mount will fail with:

ext4_check_bdev_write_error:193: comm mount: Error while async write back metadata

This happens because sbi->s_bdev_wb_err is not initialized when mounting
the filesystem in read only mode and so ext4_check_bdev_write_error()
falsely triggers.

Initialize sbi->s_bdev_wb_err unconditionally to avoid this problem.

> 
> Fixes: bc71726c7257 ("ext4: abort the filesystem if failed to async write metadata buffer")
> Signed-off-by: Zhang Xiaoxu <zhangxiaoxu5@huawei.com>

Otherwise the patch looks good so feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza


> ---
>  fs/ext4/super.c | 13 ++-----------
>  1 file changed, 2 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index ea425b49b345..0303e6e17190 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -4814,9 +4814,8 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>  	 * 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);
> +	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);
> @@ -5707,14 +5706,6 @@ 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
> -- 
> 2.25.4
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR