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Wed, 14 Oct 2020 05:56:58 -0400 X-MC-Unique: J3VBtSrYNCmOJPeN5WNKvw-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8362210066FC; Wed, 14 Oct 2020 09:56:56 +0000 (UTC) Received: from T590 (ovpn-12-36.pek2.redhat.com [10.72.12.36]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7CDDE60C07; Wed, 14 Oct 2020 09:56:46 +0000 (UTC) Date: Wed, 14 Oct 2020 17:56:42 +0800 From: Ming Lei To: Chao Leng Subject: Re: [PATCH] block: re-introduce blk_mq_complete_request_sync Message-ID: <20201014095642.GE775684@T590> References: <23f19725-f46b-7de7-915d-b97fd6d69cdc@redhat.com> <7a7aca6e-30f5-0754-fb7f-599699b97108@redhat.com> <6f2a5ae2-2e6a-0386-691c-baefeecb5478@huawei.com> <20201012081306.GB556731@T590> <5e05fc3b-ad81-aacc-1f8e-7ff0d1ad58fe@huawei.com> <20201014010813.GA775684@T590> <20201014033434.GC775684@T590> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201014_055701_481336_D35C3E74 X-CRM114-Status: GOOD ( 35.46 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jens Axboe , Yi Zhang , Sagi Grimberg , linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, Keith Busch , Christoph Hellwig 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 Wed, Oct 14, 2020 at 05:39:12PM +0800, Chao Leng wrote: > > > On 2020/10/14 11:34, Ming Lei wrote: > > On Wed, Oct 14, 2020 at 09:08:28AM +0800, Ming Lei wrote: > > > On Tue, Oct 13, 2020 at 03:36:08PM -0700, Sagi Grimberg wrote: > > > > > > > > > > > This may just reduce the probability. The concurrency of timeout > > > > > > > and teardown will cause the same request > > > > > > > be treated repeatly, this is not we expected. > > > > > > > > > > > > That is right, not like SCSI, NVME doesn't apply atomic request > > > > > > completion, so > > > > > > request may be completed/freed from both timeout & nvme_cancel_request(). > > > > > > > > > > > > .teardown_lock still may cover the race with Sagi's patch because > > > > > > teardown > > > > > > actually cancels requests in sync style. > > > > > In extreme scenarios, the request may be already retry success(rq state > > > > > change to inflight). > > > > > Timeout processing may wrongly stop the queue and abort the request. > > > > > teardown_lock serialize the process of timeout and teardown, but do not > > > > > avoid the race. > > > > > It might not be safe. > > > > > > > > Not sure I understand the scenario you are describing. > > > > > > > > what do you mean by "In extreme scenarios, the request may be already retry > > > > success(rq state change to inflight)"? > > > > > > > > What will retry the request? only when the host will reconnect > > > > the request will be retried. > > > > > > > > We can call nvme_sync_queues in the last part of the teardown, but > > > > I still don't understand the race here. > > > > > > Not like SCSI, NVME doesn't complete request atomically, so double > > > completion/free can be done from both timeout & nvme_cancel_request()(via teardown). > > > > > > Given request is completed remotely or asynchronously in the two code paths, > > > the teardown_lock can't protect the case. > > > > Thinking of the issue further, the race shouldn't be between timeout and > > teardown. > > > > Both nvme_cancel_request() and nvme_tcp_complete_timed_out() are called > > with .teardown_lock, and both check if the request is completed before > > calling blk_mq_complete_request() which marks the request as COMPLETE state. > > So the request shouldn't be double-freed in the two code paths. > > > > Another possible reason is that between timeout and normal completion(fail > > fast pending requests after ctrl state is updated to CONNECTING). > > > > Yi, can you try the following patch and see if the issue is fixed? > > > > diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c > > index d6a3e1487354..fab9220196bd 100644 > > --- a/drivers/nvme/host/tcp.c > > +++ b/drivers/nvme/host/tcp.c > > @@ -1886,7 +1886,6 @@ static int nvme_tcp_configure_admin_queue(struct nvme_ctrl *ctrl, bool new) > > static void nvme_tcp_teardown_admin_queue(struct nvme_ctrl *ctrl, > > bool remove) > > { > > - mutex_lock(&to_tcp_ctrl(ctrl)->teardown_lock); > > blk_mq_quiesce_queue(ctrl->admin_q); > > nvme_tcp_stop_queue(ctrl, 0); > > if (ctrl->admin_tagset) { > > @@ -1897,15 +1896,13 @@ static void nvme_tcp_teardown_admin_queue(struct nvme_ctrl *ctrl, > > if (remove) > > blk_mq_unquiesce_queue(ctrl->admin_q); > > nvme_tcp_destroy_admin_queue(ctrl, remove); > > - mutex_unlock(&to_tcp_ctrl(ctrl)->teardown_lock); > > } > > static void nvme_tcp_teardown_io_queues(struct nvme_ctrl *ctrl, > > bool remove) > > { > > - mutex_lock(&to_tcp_ctrl(ctrl)->teardown_lock); > > if (ctrl->queue_count <= 1) > > - goto out; > > + return; > > blk_mq_quiesce_queue(ctrl->admin_q); > > nvme_start_freeze(ctrl); > > nvme_stop_queues(ctrl); > > @@ -1918,8 +1915,6 @@ static void nvme_tcp_teardown_io_queues(struct nvme_ctrl *ctrl, > > if (remove) > > nvme_start_queues(ctrl); > > nvme_tcp_destroy_io_queues(ctrl, remove); > > -out: > > - mutex_unlock(&to_tcp_ctrl(ctrl)->teardown_lock); > > } > > static void nvme_tcp_reconnect_or_remove(struct nvme_ctrl *ctrl) > > @@ -2030,11 +2025,11 @@ static void nvme_tcp_error_recovery_work(struct work_struct *work) > > struct nvme_ctrl *ctrl = &tcp_ctrl->ctrl; > > nvme_stop_keep_alive(ctrl); > > + > > + mutex_lock(&tcp_ctrl->teardown_lock); > > nvme_tcp_teardown_io_queues(ctrl, false); > > - /* unquiesce to fail fast pending requests */ > > - nvme_start_queues(ctrl); > > nvme_tcp_teardown_admin_queue(ctrl, false); > > - blk_mq_unquiesce_queue(ctrl->admin_q); > Delete blk_mq_unquiesce_queue will cause a bug which may cause reconnect failed. > Delete nvme_start_queues may cause another bug. nvme_tcp_setup_ctrl() will re-start io and admin queue, and only .connect_q and .fabrics_q are required during reconnect. So can you explain in detail about the bug? Thanks, Ming _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme