Re: [PATCH v2 3/3] btrfs: call mapping_set_error() on btree inode with a write error

[Nikolay Borisov <nborisov@suse.com>]

On 24.11.21 г. 21:14, Josef Bacik wrote:
> generic/484 fails sometimes with compression on because the write ends
> up small enough that it goes into the btree.  This means that we never
> call mapping_set_error() on the inode itself, because the page gets
> marked as fine when we inline it into the metadata.  When the metadata
> writeback happens we see it and abort the transaction properly and mark
> the fs as readonly, however we don't do the mapping_set_error() on
> anything.  In syncfs() we will simply return 0 if the sb is marked
> read-only, so we can't check for this in our syncfs callback.  The only
> way the error gets returned if we called mapping_set_error() on
> something.  Fix this by calling mapping_set_error() on the btree inode
> mapping.  This allows us to properly return an error on syncfs and pass
> generic/484 with compression on.
> 
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>

Reviewed-by: Nikolay Borisov <nborisov@suse.com>

> ---
>  fs/btrfs/extent_io.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 3454cac28389..1a67f4b3986b 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -4314,6 +4314,14 @@ static void set_btree_ioerr(struct page *page, struct extent_buffer *eb)
>  	 */
>  	clear_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
>  
> +	/*
> +	 * We need to set the mapping with the io error as well because a write
> +	 * error will flip the file system readonly, and then syncfs() will
> +	 * return a 0 because we are readonly if we don't modify the err seq for
> +	 * the superblock.
> +	 */
> +	mapping_set_error(page->mapping, -EIO);
> +
>  	/*
>  	 * If we error out, we should add back the dirty_metadata_bytes
>  	 * to make it consistent.
>