Re: [PATCH v2 3/4] btrfs: fix error handling of fallbacked uncompress write

[Filipe Manana <fdmanana@kernel.org>]

On Tue, Jun 21, 2022 at 03:41:01PM +0900, Naohiro Aota wrote:
> When cow_file_range() fails in the middle of the allocation loop, it
> unlocks the pages but leaves the ordered extents intact. Thus, we need to
> call btrfs_cleanup_ordered_extents() to finish the created ordered extents.
> 
> Also, we need to call end_extent_writepage() if locked_page is available
> because btrfs_cleanup_ordered_extents() never process the region on the
> locked_page.
> 
> Furthermore, we need to set the mapping as error if locked_page is
> unavailable before unlocking the pages, so that the errno is properly
> propagated to the userland.
> 
> CC: stable@vger.kernel.org # 5.18+
> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
> ---
> I choose 5.18+ as the target as they are after refactoring and we can apply
> the series cleanly. Technically, older versions potentially have the same
> issue, but it might not happen actually. So, let's choose easy targets to
> apply.
> ---
>  fs/btrfs/inode.c | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 326150552e57..38d8e6d78e77 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -933,8 +933,18 @@ static int submit_uncompressed_range(struct btrfs_inode *inode,
>  		goto out;
>  	}
>  	if (ret < 0) {
> -		if (locked_page)
> +		btrfs_cleanup_ordered_extents(inode, locked_page, start, end - start + 1);
> +		if (locked_page) {
> +			u64 page_start = page_offset(locked_page);
> +			u64 page_end = page_start + PAGE_SIZE - 1;
> +
> +			btrfs_page_set_error(inode->root->fs_info, locked_page,
> +					     page_start, PAGE_SIZE);
> +			set_page_writeback(locked_page);
> +			end_page_writeback(locked_page);
> +			end_extent_writepage(locked_page, ret, page_start, page_end);
>  			unlock_page(locked_page);
> +		}
>  		goto out;
>  	}
>  
> @@ -1383,9 +1393,12 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
>  	 * However, in case of unlock == 0, we still need to unlock the pages
>  	 * (except @locked_page) to ensure all the pages are unlocked.
>  	 */
> -	if (!unlock && orig_start < start)
> +	if (!unlock && orig_start < start) {
> +		if (!locked_page)
> +			mapping_set_error(inode->vfs_inode.i_mapping, ret);

Instead of this we can pass PAGE_SET_ERROR in page_ops, which will result in
setting the error in the inode's mapping.

In fact we currently only mark the locked page with error (at writepage_delalloc()).
However all pages before and after it are still locked and we don't set the error on
them, I think we should - I don't see why not.

Did I miss something (again)?

Sorry I only noticed this now.

Thanks.

>  		extent_clear_unlock_delalloc(inode, orig_start, start - 1,
>  					     locked_page, 0, page_ops);
> +	}
>  
>  	/*
>  	 * For the range (2). If we reserved an extent for our delalloc range
> -- 
> 2.35.1
>