Re: [PATCH] btrfs: return an error for unrepaired RAID56 scrub sectors

[Filipe Manana]

On Sun, Oct 25, 2026 at 6:05 PM Cheng Yongkang <teel4res@xxxxxxxxx> wrote:
>
> scrub_raid56_parity_stripe() returns the leftover value of
> scrub_find_fill_first_stripe() (0 or 1) when it detects unrepaired
> sectors in a data stripe.  Scrub callers only treat negative values as
> errors, so the unrepaired state is masked as success and P/Q
> regeneration is skipped; a device replace can then copy corrupted data.
>
> Return -EIO so the unrepaired sectors are reported and the corrupt
> stripe is not treated as healthy.
>
> The masked-success behavior was reproduced 3/3 times: baseline scrub
> returned 0 with "finished ... status: 0", left P/Q unregenerated, and a
> device replace copied corruption.  With this change scrub returns -EIO
> and the replace is canceled; healthy RAID1/RAID5 scrub still succeeds.

This information in the last paragraph is rather useless.
Rather than state the obvious, just check why we were not returning an
error when we should have. If you checked the git history, you would
see this is a regression.
Also, add a Fixes tag identifying the commit, as this is a bug and
should be backported to stable kernels.

You should also check the for-next branches (in kernel.org and on
https://github.com/btrfs/linux/commits/for-next/) before sending
patches, as this issue was already fixed:

https://github.com/btrfs/linux/commits/for-next/

>
> Assisted-by: LLM
> Signed-off-by: Cheng Yongkang <teel4res@xxxxxxxxx>
> ---
>  fs/btrfs/scrub.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
> index 479c0e0..ba2e27c 100644
> --- a/fs/btrfs/scrub.c
> +++ b/fs/btrfs/scrub.c
> @@ -2250,7 +2250,7 @@ static int scrub_raid56_parity_stripe(struct scrub_ctx *sctx,
>  "scrub: unrepaired sectors detected, full stripe %llu data stripe %u errors %*pbl",
>                                   full_stripe_start, i, stripe->nr_sectors,
>                                   &error);
> -                       return ret;
> +                       return -EIO;
>                 }
>                 bitmap_or(&extent_bitmap, &extent_bitmap, &has_extent,
>                           stripe->nr_sectors);
> --
> 2.34.1
>
>