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From: Ming Lei <ming.lei@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, Hannes Reinecke <hare@suse.com>,
	Keith Busch <keith.busch@intel.com>,
	linux-nvme@lists.infradead.org, Sagi Grimberg <sagi@grimberg.me>,
	James Smart <james.smart@broadcom.com>,
	Dongli Zhang <dongli.zhang@oracle.com>,
	Bart Van Assche <bart.vanassche@wdc.com>,
	linux-scsi@vger.kernel.org,
	"Martin K . Petersen" <martin.petersen@oracle.com>,
	"James E . J . Bottomley" <jejb@linux.vnet.ibm.com>
Subject: Re: [PATCH V7 1/9] blk-mq: grab .q_usage_counter when queuing request from plug code path
Date: Thu, 25 Apr 2019 15:35:43 +0800	[thread overview]
Message-ID: <20190425073542.GA28630@ming.t460p> (raw)
In-Reply-To: <20190425053234.GA7166@lst.de>

On Thu, Apr 25, 2019 at 07:32:34AM +0200, Christoph Hellwig wrote:
> On Thu, Apr 25, 2019 at 08:53:34AM +0800, Ming Lei wrote:
> > It isn't in other callers of blk_mq_sched_insert_requests(), it is just
> > needed in some corner case like flush plug context.
> > 
> > For other callers of blk_mq_sched_insert_requests(), it is guaranteed
> > that request queue's ref is held.
> 
> In both Linus' tree and Jens' for-5.2 tree I only see these two
> callers of blk_mq_sched_insert_requests.  What am I missing?

OK, what I meant is that the issue is flush plug context specific.
And I didn't notice that this function is only called by
blk_mq_flush_plug_list().

Then it is fine to move the percpu_ref_get()/percpu_ref_put() into
the function, better with comment on this issue.

Thanks, 
Ming

WARNING: multiple messages have this Message-ID (diff)
From: ming.lei@redhat.com (Ming Lei)
Subject: [PATCH V7 1/9] blk-mq: grab .q_usage_counter when queuing request from plug code path
Date: Thu, 25 Apr 2019 15:35:43 +0800	[thread overview]
Message-ID: <20190425073542.GA28630@ming.t460p> (raw)
In-Reply-To: <20190425053234.GA7166@lst.de>

On Thu, Apr 25, 2019@07:32:34AM +0200, Christoph Hellwig wrote:
> On Thu, Apr 25, 2019@08:53:34AM +0800, Ming Lei wrote:
> > It isn't in other callers of blk_mq_sched_insert_requests(), it is just
> > needed in some corner case like flush plug context.
> > 
> > For other callers of blk_mq_sched_insert_requests(), it is guaranteed
> > that request queue's ref is held.
> 
> In both Linus' tree and Jens' for-5.2 tree I only see these two
> callers of blk_mq_sched_insert_requests.  What am I missing?

OK, what I meant is that the issue is flush plug context specific.
And I didn't notice that this function is only called by
blk_mq_flush_plug_list().

Then it is fine to move the percpu_ref_get()/percpu_ref_put() into
the function, better with comment on this issue.

Thanks, 
Ming

  reply	other threads:[~2019-04-25  7:35 UTC|newest]

Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-24 11:02 [PATCH V7 0/9] blk-mq: fix races related with freeing queue Ming Lei
2019-04-24 11:02 ` Ming Lei
2019-04-24 11:02 ` [PATCH V7 1/9] blk-mq: grab .q_usage_counter when queuing request from plug code path Ming Lei
2019-04-24 11:02   ` Ming Lei
2019-04-24 16:18   ` Christoph Hellwig
2019-04-24 16:18     ` Christoph Hellwig
2019-04-25  0:53     ` Ming Lei
2019-04-25  0:53       ` Ming Lei
2019-04-25  5:32       ` Christoph Hellwig
2019-04-25  5:32         ` Christoph Hellwig
2019-04-25  7:35         ` Ming Lei [this message]
2019-04-25  7:35           ` Ming Lei
2019-04-24 11:02 ` [PATCH V7 2/9] blk-mq: move cancel of requeue_work into blk_mq_release Ming Lei
2019-04-24 11:02   ` Ming Lei
2019-04-24 16:18   ` Christoph Hellwig
2019-04-24 16:18     ` Christoph Hellwig
2019-04-24 11:02 ` [PATCH V7 3/9] blk-mq: free hw queue's resource in hctx's release handler Ming Lei
2019-04-24 11:02   ` Ming Lei
2019-04-24 16:19   ` Christoph Hellwig
2019-04-24 16:19     ` Christoph Hellwig
2019-04-24 11:02 ` [PATCH V7 4/9] blk-mq: move all hctx alloction & initialization into __blk_mq_alloc_and_init_hctx Ming Lei
2019-04-24 11:02   ` Ming Lei
2019-04-24 16:22   ` Christoph Hellwig
2019-04-24 16:22     ` Christoph Hellwig
2019-04-25  0:55     ` Ming Lei
2019-04-25  0:55       ` Ming Lei
2019-04-26 15:09       ` Christoph Hellwig
2019-04-26 15:09         ` Christoph Hellwig
2019-04-25  1:02     ` Ming Lei
2019-04-25  1:02       ` Ming Lei
2019-04-24 11:02 ` [PATCH V7 5/9] blk-mq: split blk_mq_alloc_and_init_hctx into two parts Ming Lei
2019-04-24 11:02   ` Ming Lei
2019-04-24 11:02 ` [PATCH V7 6/9] blk-mq: always free hctx after request queue is freed Ming Lei
2019-04-24 11:02   ` Ming Lei
2019-04-24 11:15   ` Hannes Reinecke
2019-04-24 11:15     ` Hannes Reinecke
2019-04-24 11:02 ` [PATCH V7 7/9] blk-mq: move cancel of hctx->run_work into blk_mq_hw_sysfs_release Ming Lei
2019-04-24 11:02   ` Ming Lei
2019-04-24 11:02 ` [PATCH V7 8/9] block: don't drain in-progress dispatch in blk_cleanup_queue() Ming Lei
2019-04-24 11:02   ` Ming Lei
2019-04-24 11:02 ` [PATCH V7 9/9] nvme: hold request queue's refcount in ns's whole lifetime Ming Lei
2019-04-24 11:02   ` Ming Lei
2019-04-24 16:27   ` Christoph Hellwig
2019-04-24 16:27     ` Christoph Hellwig
2019-04-25  1:00     ` Ming Lei
2019-04-25  1:00       ` Ming Lei
2019-04-26 15:11       ` Christoph Hellwig
2019-04-26 15:11         ` Christoph Hellwig
2019-04-26 17:04         ` Bart Van Assche
2019-04-26 17:04           ` Bart Van Assche
2019-04-26 22:49           ` Ming Lei
2019-04-26 22:49             ` Ming Lei
2019-04-26 22:45         ` Ming Lei
2019-04-26 22:45           ` Ming Lei
2019-04-27  5:54           ` Christoph Hellwig
2019-04-27  5:54             ` Christoph Hellwig

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