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From: Keith Busch <kbusch@kernel.org>
To: Ming Lei <tom.leiming@gmail.com>
Cc: Jianchao Wang <jianchao.w.wang@oracle.com>,
	"axboe@kernel.dk" <axboe@kernel.dk>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	"jsmart2021@gmail.com" <jsmart2021@gmail.com>,
	"bvanassche@acm.org" <bvanassche@acm.org>,
	"josef@toxicpanda.com" <josef@toxicpanda.com>,
	"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"Busch, Keith" <keith.busch@intel.com>,
	"hare@suse.de" <hare@suse.de>,
	"jthumshirn@suse.de" <jthumshirn@suse.de>,
	"hch@lst.de" <hch@lst.de>, "sagi@grimberg.me" <sagi@grimberg.me>
Subject: Re: [PATCH 2/8] blk-mq: change the method of iterating busy tags of a request_queue
Date: Mon, 18 Mar 2019 09:53:26 -0600	[thread overview]
Message-ID: <20190318155326.GB23533@localhost.localdomain> (raw)
In-Reply-To: <CACVXFVM=r-jS_GnkAuARiiXLr3bQeWV5Gix3+F03B5oYbmdULw@mail.gmail.com>

On Sat, Mar 16, 2019 at 11:50:27PM -0700, Ming Lei wrote:
> On Sat, Mar 16, 2019 at 12:15 AM Keith Busch <kbusch@kernel.org> wrote:
> > On Fri, Mar 15, 2019 at 01:57:38AM -0700, Jianchao Wang wrote:
> > > +     if (rq && rq->q == hctx->queue &&
> > > +         rq->mq_hctx == hctx &&
> > > +         (!iter_data->inflight ||
> > > +          blk_mq_rq_state(rq) == MQ_RQ_IN_FLIGHT))
> > > +             return iter_data->fn(rq, iter_data->data, reserved);
> >
> > There is still a window where the check may succeed, but the request is
> > being assigned to a completely different request_queue. The callback
> > then operates on a request it doesn't own.
> 
> The situation above is only related with 'none' io scheduler.
> 
> However, this patch doesn't change behavior for none given .rq[tag] is same with
> .static_rq[tag], so I guess your concern may not be related with this patch.

Right, it's not new, but queue iteration wasn't exported for drivers
before this.

WARNING: multiple messages have this Message-ID (diff)
From: kbusch@kernel.org (Keith Busch)
Subject: [PATCH 2/8] blk-mq: change the method of iterating busy tags of a request_queue
Date: Mon, 18 Mar 2019 09:53:26 -0600	[thread overview]
Message-ID: <20190318155326.GB23533@localhost.localdomain> (raw)
In-Reply-To: <CACVXFVM=r-jS_GnkAuARiiXLr3bQeWV5Gix3+F03B5oYbmdULw@mail.gmail.com>

On Sat, Mar 16, 2019@11:50:27PM -0700, Ming Lei wrote:
> On Sat, Mar 16, 2019@12:15 AM Keith Busch <kbusch@kernel.org> wrote:
> > On Fri, Mar 15, 2019@01:57:38AM -0700, Jianchao Wang wrote:
> > > +     if (rq && rq->q == hctx->queue &&
> > > +         rq->mq_hctx == hctx &&
> > > +         (!iter_data->inflight ||
> > > +          blk_mq_rq_state(rq) == MQ_RQ_IN_FLIGHT))
> > > +             return iter_data->fn(rq, iter_data->data, reserved);
> >
> > There is still a window where the check may succeed, but the request is
> > being assigned to a completely different request_queue. The callback
> > then operates on a request it doesn't own.
> 
> The situation above is only related with 'none' io scheduler.
> 
> However, this patch doesn't change behavior for none given .rq[tag] is same with
> .static_rq[tag], so I guess your concern may not be related with this patch.

Right, it's not new, but queue iteration wasn't exported for drivers
before this.

  reply	other threads:[~2019-03-18 15:52 UTC|newest]

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-15  8:57 [PATCH 0/8]: blk-mq: use static_rqs to iterate busy tags Jianchao Wang
2019-03-15  8:57 ` Jianchao Wang
2019-03-15  8:57 ` [PATCH 1/8] blk-mq: get rid of the synchronize_rcu in __blk_mq_update_nr_hw_queues Jianchao Wang
2019-03-15  8:57   ` Jianchao Wang
2019-03-17  6:14   ` Ming Lei
2019-03-17  6:14     ` Ming Lei
2019-03-15  8:57 ` [PATCH 2/8] blk-mq: change the method of iterating busy tags of a request_queue Jianchao Wang
2019-03-15  8:57   ` Jianchao Wang
2019-03-15 16:16   ` Keith Busch
2019-03-15 16:16     ` Keith Busch
2019-03-17  6:50     ` Ming Lei
2019-03-17  6:50       ` Ming Lei
2019-03-18 15:53       ` Keith Busch [this message]
2019-03-18 15:53         ` Keith Busch
2019-03-18  1:49     ` jianchao.wang
2019-03-18  1:49       ` jianchao.wang
2019-03-20 18:52   ` Sagi Grimberg
2019-03-20 18:52     ` Sagi Grimberg
2019-03-21  1:33     ` jianchao.wang
2019-03-21  1:33       ` jianchao.wang
2019-03-15  8:57 ` [PATCH 3/8] blk-mq: use blk_mq_queue_tag_busy_iter in debugfs Jianchao Wang
2019-03-15  8:57   ` Jianchao Wang
2019-03-15  8:57 ` [PATCH 4/8] mtip32xx: use blk_mq_queue_tag_busy_iter Jianchao Wang
2019-03-15  8:57   ` Jianchao Wang
2019-03-15  8:57 ` [PATCH 5/8] nbd: " Jianchao Wang
2019-03-15  8:57   ` Jianchao Wang
2019-03-18 17:16   ` Bart Van Assche
2019-03-18 17:16     ` Bart Van Assche
2019-03-19  2:04     ` jianchao.wang
2019-03-19  2:04       ` jianchao.wang
2019-03-15  8:57 ` [PATCH 6/8] skd: " Jianchao Wang
2019-03-15  8:57   ` Jianchao Wang
2019-03-18 17:20   ` Bart Van Assche
2019-03-18 17:20     ` Bart Van Assche
2019-03-19  1:54     ` jianchao.wang
2019-03-19  1:54       ` jianchao.wang
2019-03-15  8:57 ` [PATCH 7/8] nvme: " Jianchao Wang
2019-03-15  8:57   ` Jianchao Wang
2019-03-15 16:33   ` James Smart
2019-03-15 16:33     ` James Smart
2019-03-15 16:39     ` James Smart
2019-03-15 16:39       ` James Smart
2019-03-15 16:49       ` Hannes Reinecke
2019-03-15 16:49         ` Hannes Reinecke
2019-03-18  7:00     ` jianchao.wang
2019-03-18  7:00       ` jianchao.wang
2019-03-15  8:57 ` [PATCH 8/8] blk-mq: remove blk_mq_tagset_busy_iter Jianchao Wang
2019-03-15  8:57   ` Jianchao Wang
2019-03-15  9:20 ` [PATCH 0/8]: blk-mq: use static_rqs to iterate busy tags Christoph Hellwig
2019-03-15  9:20   ` Christoph Hellwig
2019-03-15  9:44   ` jianchao.wang
2019-03-15  9:44     ` jianchao.wang
2019-03-15 16:19     ` Bart Van Assche
2019-03-15 16:19       ` Bart Van Assche
2019-03-18  2:47       ` jianchao.wang
2019-03-18  2:47         ` jianchao.wang
2019-03-15 13:30   ` Josef Bacik
2019-03-15 13:30     ` Josef Bacik
2019-03-18 17:28 ` Bart Van Assche
2019-03-18 17:28   ` Bart Van Assche
2019-03-19  1:25   ` jianchao.wang
2019-03-19  1:25     ` jianchao.wang
2019-03-19 15:10     ` Bart Van Assche
2019-03-19 15:10       ` Bart Van Assche
2019-03-19 15:25       ` Keith Busch
2019-03-19 15:25         ` Keith Busch
2019-03-20 18:38         ` Sagi Grimberg
2019-03-20 18:38           ` Sagi Grimberg

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