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From: Ming Lei <ming.lei@redhat.com>
To: Bart Van Assche <bvanassche@acm.org>
Cc: Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org,
	"James E . J . Bottomley" <jejb@linux.ibm.com>,
	"Martin K . Petersen" <martin.petersen@oracle.com>,
	linux-scsi@vger.kernel.org, "Ewan D . Milne" <emilne@redhat.com>,
	Hannes Reinecke <hare@suse.com>, Christoph Hellwig <hch@lst.de>,
	Mike Snitzer <snitzer@redhat.com>,
	dm-devel@redhat.com, stable@vger.kernel.org
Subject: Re: [PATCH V2 1/2] blk-mq: add callback of .cleanup_rq
Date: Tue, 23 Jul 2019 09:00:55 +0800	[thread overview]
Message-ID: <20190723010053.GA30776@ming.t460p> (raw)
In-Reply-To: <4ffe9dd8-9e86-fd93-828e-78c1e5931c5f@acm.org>

On Mon, Jul 22, 2019 at 09:51:27AM -0700, Bart Van Assche wrote:
> On 7/19/19 8:06 PM, Ming Lei wrote:
> > diff --git a/block/blk-mq.c b/block/blk-mq.c
> > index b038ec680e84..fc38d95c557f 100644
> > --- a/block/blk-mq.c
> > +++ b/block/blk-mq.c
> > @@ -502,6 +502,9 @@ void blk_mq_free_request(struct request *rq)
> >   	struct blk_mq_ctx *ctx = rq->mq_ctx;
> >   	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
> > +	if (q->mq_ops->cleanup_rq)
> > +		q->mq_ops->cleanup_rq(rq);
> > +
> >   	if (rq->rq_flags & RQF_ELVPRIV) {
> >   		if (e && e->type->ops.finish_request)
> >   			e->type->ops.finish_request(rq);
> 
> I'm concerned about the performance impact of this change. How about not

Not see any performance impact in my test, and q->mq_ops should be in
data cache at that time.

> introducing .cleanup_rq() and adding a call to
> scsi_mq_uninit_cmd() in scsi_queue_rq() just before that function returns
> BLK_STS_RESOURCE or BLK_STS_DEV_RESOURCE?

The problem is that only dm-rq needs to free the request private data
when BLK_STS_RESOURCE or BLK_STS_DEV_RESOURCE is returned. If we do that
unconditionally, performance impact might be visible.


Thanks,
Ming

  reply	other threads:[~2019-07-23  1:01 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-20  3:06 [PATCH V2 0/2] block/scsi/dm-rq: fix leak of request private data in dm-mpath Ming Lei
2019-07-20  3:06 ` [PATCH V2 1/2] blk-mq: add callback of .cleanup_rq Ming Lei
2019-07-22 16:51   ` Bart Van Assche
2019-07-23  1:00     ` Ming Lei [this message]
2019-07-20  3:06 ` [PATCH V2 2/2] scsi: implement .cleanup_rq callback Ming Lei
2019-07-22 15:40   ` Bart Van Assche
2019-07-23  1:03     ` Ming Lei
     [not found]   ` <20190725104629.GC3640@shao2-debian>
2019-07-27  2:15     ` [scsi] ae86a1c553: BUG:kernel_NULL_pointer_dereference,address Ming Lei
2019-07-26 16:20 ` [PATCH V2 0/2] block/scsi/dm-rq: fix leak of request private data in dm-mpath Benjamin Block
2019-07-27  2:12   ` Ming Lei

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