From mboxrd@z Thu Jan  1 00:00:00 1970
From: axboe@kernel.dk (Jens Axboe)
Date: Mon, 27 Feb 2017 08:33:33 -0700
Subject: nvmf regression with mq-deadline
In-Reply-To: <0f06d732-fe32-bca0-8a4d-299a6cce7a6e@grimberg.me>
References: <8384a5c8-c8e6-4e46-65d6-208b802f6957@grimberg.me>
 <34fb43d6-37e7-feb3-73c6-63140993ba7c@grimberg.me>
 <0f06d732-fe32-bca0-8a4d-299a6cce7a6e@grimberg.me>
Message-ID: <20170227153333.GA25478@kernel.dk>

On Mon, Feb 27 2017, Sagi Grimberg wrote:
> 
> >Now I'm getting a NULL deref with nvme-rdma [1].
> >
> >For some reason blk_mq_tag_to_rq() is returning NULL on
> >tag 0x0 which is io queue connect.
> >
> >I'll try to see where this is coming from.
> >This does not happen with loop though...
> 
> That's because the loop driver does not rely on the
> cqe.command_id to resolve the submitted request (I'll
> fix that).
> 
> Looks like blk_mq_alloc_request_hctx was overlooked when
> the back assignment of the request to the rq_map...
> 
> This patch solves the issue for fabrics:
> --
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index d84c66fb37b7..9611cd9920e9 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -312,6 +312,7 @@ struct request *blk_mq_alloc_request_hctx(struct
> request_queue *q, int rw,
>                 ret = -EWOULDBLOCK;
>                 goto out_queue_exit;
>         }
> +       alloc_data.hctx->tags->rqs[rq->tag] = rq;
> 
>         return rq;
> --
> 
> If its agreed with everyone I'll send a proper patch
> for this and the blk_mq_sched_setup fix?

Thanks Sagi, yes please send a proper patch for those two conditions!

-- 
Jens Axboe