Re: [PATCH 1/3] md/raid10: restore still_degraded detection in recovery

[yu kuai]

在 2026/7/19 22:42, Mykola Marzhan 写道:

> raid10_sync_request()'s recovery arm passes still_degraded -- "will
> the array still be degraded after this recovery completes?" -- to
> md_bitmap_start_sync(), whose !degraded branch consumes the chunk's
> NEEDED marker, the write-intent record.  That is only safe when the
> recovery restores full redundancy; otherwise the record still
> describes writes an absent member missed.
>
> Commit fe6a19d40ceb ("md/md-bitmap: merge md_bitmap_start_sync()
> into bitmap_operations") turned the detection loop's only assignment
> from "still_degraded = 1" into "still_degraded = false" in its
> int-to-bool styling pass, so the flag has been constant false ever
> since.  raid1 and raid5 were converted to "= true"; only raid10 was
> inverted.
>
> The result is silent data loss on a classic-bitmap raid10 that stays
> degraded across a recovery.  With mirror pairs {A,B} and {C,D}: lose
> D, keep writing, lose B, add a spare.  The rebuild into B's slot
> strips NEEDED from every chunk -- including chunks whose only
> unsatisfied intent belonged to D -- so a later --re-add of D sees an
> empty intent record, completes instantly, and serves stale data.
>
> Restore the pre-conversion assignment.  Only the classic-bitmap
> recovery arm is affected: llbitmap ignores the degraded parameter,
> and the resync arm passes mddev->degraded directly.
>
> Fixes: fe6a19d40ceb ("md/md-bitmap: merge md_bitmap_start_sync() into bitmap_operations")
> Cc:stable@xxxxxxxxxxxxxxx # v6.12+
> Assisted-by: Claude-Code:claude-opus-4-8
> Signed-off-by: Mykola Marzhan<mykola@xxxxxxxxxxx>
> ---
>   drivers/md/raid10.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
Reviewed-by: Yu Kuai <yukuai@xxxxxxx>

-- 
Thanks,
Kuai