Re: [PATCH V4 0/2] block/scsi/dm-rq: fix leak of request private data in dm-mpath

From: Ming Lei <ming.lei@redhat.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org, "Ewan D . Milne" <emilne@redhat.com>,
	Bart Van Assche <bvanassche@acm.org>,
	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 V4 0/2] block/scsi/dm-rq: fix leak of request private data in dm-mpath
Date: Mon, 5 Aug 2019 08:55:33 +0800	[thread overview]
Message-ID: <20190805005532.GA3449@ming.t460p> (raw)
In-Reply-To: <20190730004359.GA28708@ming.t460p>

On Tue, Jul 30, 2019 at 08:43:59AM +0800, Ming Lei wrote:
> On Thu, Jul 25, 2019 at 10:04:58AM +0800, Ming Lei wrote:
> > Hi,
> > 
> > When one request is dispatched to LLD via dm-rq, if the result is
> > BLK_STS_*RESOURCE, dm-rq will free the request. However, LLD may allocate
> > private data for this request, so this way will cause memory leak.
> > 
> > Add .cleanup_rq() callback and implement it in SCSI for fixing the issue,
> > since SCSI is the only driver which allocates private requst data in
> > .queue_rq() path.
> > 
> > Another use case of this callback is to free the request and re-submit
> > bios during cpu hotplug when the hctx is dead, see the following link:
> > 
> > https://lore.kernel.org/linux-block/f122e8f2-5ede-2d83-9ca0-bc713ce66d01@huawei.com/T/#t
> > 
> > V4:
> > 	- add more commit log on the new .cleanup_rq callback, as suggested
> > 	  by Mike
> > 
> > V3:
> > 	- run .cleanup_rq() from dm-rq because this issue is dm-rq specific,
> > 	and even in future it should be still very unusual to free request
> > 	in this way. If we call .cleanup_rq() in generic rq free code(fast
> > 	path), cost will be introduced unnecessarily, also we have to
> > 	consider related race.
> > 
> > V2:
> > 	- run .cleanup_rq() in blk_mq_free_request(), as suggested by Mike 
> > 
> > 
> > 
> > Ming Lei (2):
> >   blk-mq: add callback of .cleanup_rq
> >   scsi: implement .cleanup_rq callback
> > 
> >  drivers/md/dm-rq.c      |  1 +
> >  drivers/scsi/scsi_lib.c | 13 +++++++++++++
> >  include/linux/blk-mq.h  | 13 +++++++++++++
> >  3 files changed, 27 insertions(+)
> > 
> > Cc: Ewan D. Milne <emilne@redhat.com>
> > Cc: Bart Van Assche <bvanassche@acm.org>
> > Cc: Hannes Reinecke <hare@suse.com>
> > Cc: Christoph Hellwig <hch@lst.de>
> > Cc: Mike Snitzer <snitzer@redhat.com>
> > Cc: dm-devel@redhat.com
> > Cc: <stable@vger.kernel.org>
> > Fixes: 396eaf21ee17 ("blk-mq: improve DM's blk-mq IO merging via blk_insert_cloned_request feedback")
> 
> Hello Jens & guys,
> 
> Ping on this fix.

Hi Jens,

Could you make the patcheset merged for 5.4? And it has been verified
that big memory leak issue can be fixed by this patchset.

thanks,
Ming