Re: [PATCH] btrfs: raid56: fix an incorrect csum skip during scrub

On Sun, 12 Jul 2026 at 05:43, Qu Wenruo <[email protected]> wrote:
> Commit 7425a2894019 ("btrfs: introduce btrfs_bio_for_each_block_all()
> helper") uses the new helper to replace the nested loop inside
> verify_bio_data_sectors(), which simplifies the code.
>
> However that also changed the behavior of "continue" when a block has no
> data checksum.
>
> Previously the "continue" will skip the old for() loop, which will also
> increase @total_sector_nr.
>
> Now the "continue" will skip the new btrfs_bio_for_each_block_all()
> loop, which doesn't update @total_sector_nr.
>
> This means if we hit a block that has no data checksum, we will skip all
> the remaining blocks no matter if they have data checksum.
> As @total_sector_nr will never be updated, and that test_bit() will
> always return false.
>
> Fix it by increasing @total_sector_nr before calling "continue".
>
> Fixes: 7425a2894019 ("btrfs: introduce btrfs_bio_for_each_block_all() helper")
> Signed-off-by: Qu Wenruo <[email protected]>

Thanks

Reviewed-by: Daniel Vacek <[email protected]>

> ---
>  fs/btrfs/raid56.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
> index baaa18b3c958..885602ab6448 100644
> --- a/fs/btrfs/raid56.c
> +++ b/fs/btrfs/raid56.c
> @@ -1679,8 +1679,10 @@ static void verify_bio_data_sectors(struct btrfs_raid_bio *rbio,
>                         continue;
>
>                 /* No csum for this sector, skip to the next sector. */
> -               if (!test_bit(total_sector_nr, rbio->csum_bitmap))
> +               if (!test_bit(total_sector_nr, rbio->csum_bitmap)) {
> +                       total_sector_nr++;
>                         continue;
> +               }
>
>                 expected_csum = rbio->csum_buf + total_sector_nr * fs_info->csum_size;
>                 btrfs_calculate_block_csum_pages(fs_info, paddrs, csum_buf);
> --
> 2.54.0
>
>