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16 Sep 2019 19:38:45 +0000 Received: from EX13MTAUWB001.ant.amazon.com (pdx4-ws-svc-p6-lb7-vlan2.pdx.amazon.com [10.170.41.162]) by email-inbound-relay-2a-69849ee2.us-west-2.amazon.com (Postfix) with ESMTPS id 81183A07CB; Mon, 16 Sep 2019 19:38:45 +0000 (UTC) Received: from EX13D01UWB004.ant.amazon.com (10.43.161.157) by EX13MTAUWB001.ant.amazon.com (10.43.161.207) with Microsoft SMTP Server (TLS) id 15.0.1367.3; Mon, 16 Sep 2019 19:38:44 +0000 Received: from EX13D01UWB002.ant.amazon.com (10.43.161.136) by EX13d01UWB004.ant.amazon.com (10.43.161.157) with Microsoft SMTP Server (TLS) id 15.0.1367.3; Mon, 16 Sep 2019 19:38:44 +0000 Received: from EX13D01UWB002.ant.amazon.com ([10.43.161.136]) by EX13d01UWB002.ant.amazon.com ([10.43.161.136]) with mapi id 15.00.1367.000; Mon, 16 Sep 2019 19:38:44 +0000 From: "Singh, Balbir" To: "bvanassche@acm.org" , "linux-nvme@lists.infradead.org" , "sblbir@amzn.com" Subject: Re: [PATCH v2 1/2] nvme/host/pci: Fix a race in controller removal Thread-Topic: [PATCH v2 1/2] nvme/host/pci: Fix a race in controller removal Thread-Index: AQHVaowXMhT5fp4jR0Gn8rYSgg/tw6cudR4AgABCegA= Date: Mon, 16 Sep 2019 19:38:44 +0000 Message-ID: <25d9badc90a1eb951cb5103774e8360edaa8ec15.camel@amazon.com> References: <20190913233631.15352-1-sblbir@amzn.com> <7017c4c1-75a9-1e37-eb54-6126dfbb251b@acm.org> In-Reply-To: <7017c4c1-75a9-1e37-eb54-6126dfbb251b@acm.org> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-messagesentrepresentingtype: 1 x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.43.161.34] Content-ID: MIME-Version: 1.0 Precedence: Bulk X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190916_123916_998731_4DA0768A X-CRM114-Status: GOOD ( 18.00 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.29 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "kbusch@kernel.org" , "axboe@fb.com" , "hch@lst.de" , "sagi@grimberg.me" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Mon, 2019-09-16 at 08:40 -0700, Bart Van Assche wrote: > On 9/13/19 4:36 PM, Balbir Singh wrote: > > diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c > > index b45f82d58be8..f6ddb58a7013 100644 > > --- a/drivers/nvme/host/core.c > > +++ b/drivers/nvme/host/core.c > > @@ -103,10 +103,16 @@ static void nvme_set_queue_dying(struct > > nvme_ns *ns) > > */ > > if (!ns->disk || test_and_set_bit(NVME_NS_DEAD, &ns->flags)) > > return; > > - revalidate_disk(ns->disk); > > blk_set_queue_dying(ns->queue); > > /* Forcibly unquiesce queues to avoid blocking dispatch */ > > blk_mq_unquiesce_queue(ns->queue); > > + /* > > + * revalidate_disk, after all pending IO is cleaned up > > + * by blk_set_queue_dying, largely any races with blk parittion > > + * reads that might come in after freezing the queues, > > otherwise > > + * we'll end up waiting up on bd_mutex, creating a deadlock. > > + */ > > + revalidate_disk(ns->disk); > > } > > The comment above revalidate_disk() looks wrong to me. I don't think > that blk_set_queue_dying() guarantees that ongoing commands have > finished by the time that function returns. All > blk_set_queue_dying() > does is to set the DYING flag, to kill q->q_usage_counter and to wake > up > threads that are waiting inside a request allocation function. It > does > not wait for pending commands to finish. I was referring to the combined effect of blk_set_queue_dying() and blk_mq_unquiesce_queue() which should invoke blk_mq_run_hw_queues(). I can see how that might be misleading. I can reword it to say /* * revalidate_disk, after all pending IO is cleaned up * largely any races with block partition * reads that might come in after freezing the queues, otherwise * we'll end up waiting up on bd_mutex, creating a deadlock */ Would that work? Balbir Singh. > > Bart. > _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme