Re: blk-mq crash under KVM in multiqueue block code (with virtio-blk and ext4)

Jens Axboe
2014-09-17T20:16:25Z

On 09/17/2014 01:09 PM, David Hildenbrand wrote:
>>> 0. That should already be sufficient to hinder blk_mq_tag_to_rq and the calling
>>> method to do the wrong thing.
>>
>> Yes, clearing rq->cmd_flags should be enough.
>>
>> And looks better to move rq initialization to __blk_mq_free_request()
>> too, otherwise timeout still may see old cmd_flags and rq->q before
>> rq's new initialization.
>
> Yes, __blk_mq_free_request() should also reset at least rq->cmd_flags, and I
> think we can remove the initialization from __blk_mq_alloc_request().

And then we come full circle, that's how the code originally started out
(and it is the saner way to do things). So yes, I'd greatly applaud that.

--
Jens Axboe