On 2018/11/21 11:11, Jens Axboe wrote:
> On 11/20/18 4:58 PM, Damien Le Moal wrote:
>> On 2018/11/21 2:31, Jens Axboe wrote:
>>> I think the below should fix it, we haven't necessarily setup an
>>> ioc if we're just doing as passthrough request.
>>>
>>>
>>> diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
>>> index 13b8dc332541..f096d8989773 100644
>>> --- a/block/blk-mq-sched.c
>>> +++ b/block/blk-mq-sched.c
>>> @@ -34,9 +34,16 @@ EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
>>> void blk_mq_sched_assign_ioc(struct request *rq)
>>> {
>>> struct request_queue *q = rq->q;
>>> - struct io_context *ioc = current->io_context;
>>> + struct io_context *ioc;
>>> struct io_cq *icq;
>>>
>>> + /*
>>> + * May not have an IO context if it's a passthrough request
>>> + */
>>> + ioc = current->io_context;
>>> + if (!ioc)
>>> + return;
>>> +
>>> spin_lock_irq(&q->queue_lock);
>>> icq = ioc_lookup_icq(ioc, q);
>>> spin_unlock_irq(&q->queue_lock);
>>
>> This seems reasonable to me, but I wonder why this problem was not triggering
>> before. The previous code getting the ioc with the rq_ioc(bio) call was
>> essentially the same and there was no "if (!ioc) return;" in
>> blk_mq_sched_assign_ioc() before the patch.
>> Any idea why this is popping up now ?
>>
>> Ming,
>>
>> Is this a new test your are running ? If this same problem triggers on stable
>> kernels, Jens patch needs to go to stable too.
>
> No, it's definitely introduced in your patches:
>
> - if (e->type->icq_cache && rq_ioc(bio))
> - blk_mq_sched_assign_ioc(rq, bio);
> + if (e->type->icq_cache)
> + blk_mq_sched_assign_ioc(rq);
>
> Please run blktests on a series. Always. There's no excuse not to.
By the way, should I send an updated patch 2 to include your fix ?
Or will you add an incremental fix ?
--
Damien Le Moal
Western Digital Research
