Re: [PATCH] md/raid5: complete discard bios while reshape is active

[yu kuai]

Hi,

在 2026/7/12 0:13, Genjian 写道:
> From: Genjian Zhang <zhanggenjian@xxxxxxxxxx>
>
> make_discard_request() returns without completing the bio when reshape
> is in progress. Discard callers block in submit_bio_wait()
> waiting for a completion that never arrives.  The caller hangs in
> uninterruptible sleep, and this does not resolve when reshape finishes.
>
> Complete the bio with BLK_STS_AGAIN so userspace can retry after reshape,
> consistent with the existing policy of not processing discard during
> reshape.
>
> Tested on a loop-backed RAID5 array during mdadm --grow: without this
> patch, blkdiscard hangs in bio_await() and remains in uninterruptible
> sleep after md reports "reshape done"; with this patch it returns
> -EAGAIN instead.
>
> Signed-off-by: Genjian Zhang <zhanggenjian@xxxxxxxxxx>
> ---
>   drivers/md/raid5.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index ffb5fcde54a9..4c3b42b2af85 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -5722,9 +5722,11 @@ static void make_discard_request(struct mddev *mddev, struct bio *bi)
>   	if (WARN_ON_ONCE(bi->bi_opf & REQ_NOWAIT))
>   		return;

As nowait will be removed soon, I'm fine leaving it here.

Reviewed-by: Yu Kuai <yukuai@xxxxxxx>

>   
> -	if (mddev->reshape_position != MaxSector)
> +	if (mddev->reshape_position != MaxSector) {
>   		/* Skip discard while reshape is happening */
> +		bio_endio_status(bi, BLK_STS_AGAIN);
>   		return;
> +	}
>   
>   	if (!raid5_discard_limits(mddev, bi))
>   		return;

-- 
Thanks,
Kuai