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

[genjian zhang]

At 2026-07-19 20:54:42, "yu kuai" <yukuai@xxxxxxx> wrote:
>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

Thanks for the review.
I'll leave the REQ_NOWAIT path unchanged and won't send a v2 for it.

Thanks,
Genjian