Re: [PATCH] md/raid5: Fix bio retry on interrupted reshape

[Nigel Croxon <ncroxon@redhat.com>]

Looks like this was just fixed by Benjamin Marzinski's

commit 418b3e64e4459 md/raid5: Fix UAF on IO across the reshape position

So my patch is not needed anymore.

-Nigel


On 4/29/26 9:07 AM, Paul Menzel wrote:
> Dear Nigel,
>
>
> Thank you for your patch.
>
> Am 29.04.26 um 13:10 schrieb Nigel Croxon:
>> When a bio encounters LOC_INSIDE_RESHAPE during a reshape that is
>> interrupted (stopped or unable to progress), the code sets
>> bi->bi_status = BLK_STS_RESOURCE to signal the block layer for retry.
>> However, bio_endio() is never called, so the block layer never
>> receives the completion notification and the retry never happens.
>>
>> This causes I/O to hang when a filesystem is layered over RAID5 and
>> reshape gets stuck.
>>
>> Fix this by calling bio_endio(bi) before md_free_cloned_bio(bi) so
>> the block layer is properly notified of the BLK_STS_RESOURCE status
>> and can retry the request.
>>
>> Tested stripes and stripe size conversions under load comparing
>> files multiple times during each conversion (i.e. MD reshape) on
>> ext4 after dropping caches degrading the RaidLV each time and
>
> I thought RaidLV misspelled Raid V (Raid 5), so should you resend, 
> maybe write it as RAID LV.
>
>> no data corruption.
>>
>> Fixes: https://lwn.net/Articles/757123/
>
> Which paragraph/comment exactly?
>
>> Signed-off-by: Nigel Croxon <ncroxon@redhat.com>
>> ---
>>   drivers/md/raid5.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
>> index 6e79829c5acb..9a3475429ef4 100644
>> --- a/drivers/md/raid5.c
>> +++ b/drivers/md/raid5.c
>> @@ -6217,6 +6217,7 @@ static bool raid5_make_request(struct mddev 
>> *mddev, struct bio * bi)
>>
>>       mempool_free(ctx, conf->ctx_pool);
>>       if (res == STRIPE_WAIT_RESHAPE) {
>> +         bio_endio(bi);
>>           md_free_cloned_bio(bi);
>>           return false;
>>       }
>
> Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>
>
>
> Kind regards,
>
> Paul
>