From: Bart Van Assche <bvanassche@acm.org>
To: Ming Lei <ming.lei@redhat.com>, Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org,
Dongli Zhang <dongli.zhang@oracle.com>,
James Smart <james.smart@broadcom.com>,
Bart Van Assche <bart.vanassche@wdc.com>,
linux-scsi@vger.kernel.org,
"Martin K . Petersen" <martin.petersen@oracle.com>,
Christoph Hellwig <hch@lst.de>,
"James E . J . Bottomley" <jejb@linux.vnet.ibm.com>,
jianchao wang <jianchao.w.wang@oracle.com>
Subject: Re: [PATCH V3 1/6] blk-mq: grab .q_usage_counter when queuing request from plug code path
Date: Wed, 03 Apr 2019 08:21:11 -0700 [thread overview]
Message-ID: <1554304871.118779.185.camel@acm.org> (raw)
In-Reply-To: <20190403102609.18707-2-ming.lei@redhat.com>
On Wed, 2019-04-03 at 18:26 +0800, Ming Lei wrote:
> However, if request is staggered into plug list, and finally queued
> from plug code path, the refcount in submission side is actually missed.
> And we may start to run queue after queue is removed, then kernel oops
> is triggered.
I don't think that this patch is necessary. blk_mq_get_request() increases
q_usage_counter. In other words, as long as at least one request has been
allocated that has not finished it is guaranteed that q_usage_counter > 0.
So there is no need for additional protection in blk_mq_flush_plug_list().
Bart.
next prev parent reply other threads:[~2019-04-03 15:21 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-03 10:26 [PATCH V3 0/6] blk-mq: fix races related with freeing queue Ming Lei
2019-04-03 10:26 ` [PATCH V3 1/6] blk-mq: grab .q_usage_counter when queuing request from plug code path Ming Lei
2019-04-03 15:21 ` Bart Van Assche [this message]
2019-04-03 16:27 ` Ming Lei
2019-04-03 21:22 ` Bart Van Assche
2019-04-04 6:57 ` Ming Lei
2019-04-03 10:26 ` [PATCH V3 2/6] blk-mq: move cancel of requeue_work into blk_mq_release Ming Lei
2019-04-03 16:19 ` Bart Van Assche
2019-04-03 10:26 ` [PATCH V3 3/6] blk-mq: free hw queue's resource in hctx's release handler Ming Lei
2019-04-03 16:26 ` Bart Van Assche
2019-04-04 6:40 ` Ming Lei
2019-04-04 7:42 ` Ming Lei
2019-04-03 10:26 ` [PATCH V3 4/6] blk-mq: move cancel of hctx->run_work into blk_mq_hw_sysfs_release Ming Lei
2019-04-03 16:21 ` Bart Van Assche
2019-04-03 10:26 ` [PATCH V3 5/6] block: don't drain in-progress dispatch in blk_cleanup_queue() Ming Lei
2019-04-03 15:25 ` Bart Van Assche
2019-04-03 10:26 ` [PATCH V3 6/6] SCSI: don't hold device refcount in IO path Ming Lei
2019-04-03 16:24 ` Bart Van Assche
2019-04-04 6:47 ` Ming Lei
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