From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E589BC4363D for ; Wed, 21 Oct 2020 02:55:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8729E22242 for ; Wed, 21 Oct 2020 02:55:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="H9VbReao" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2411458AbgJUCz5 (ORCPT ); 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Wed, 21 Oct 2020 02:55:49 +0000 (UTC) Received: from T590 (ovpn-12-44.pek2.redhat.com [10.72.12.44]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 38AB35B4A1; Wed, 21 Oct 2020 02:55:37 +0000 (UTC) Date: Wed, 21 Oct 2020 10:55:34 +0800 From: Ming Lei To: Chao Leng Cc: Jens Axboe , linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, Christoph Hellwig , Keith Busch , Sagi Grimberg , Yi Zhang Subject: Re: [PATCH V2 3/4] nvme: tcp: complete non-IO requests atomically Message-ID: <20201021025534.GD1571548@T590> References: <20201020085301.1553959-1-ming.lei@redhat.com> <20201020085301.1553959-4-ming.lei@redhat.com> <20201021012241.GC1571548@T590> <7a3cdbdb-8e57-484c-fcb3-e8e72dfe8d13@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7a3cdbdb-8e57-484c-fcb3-e8e72dfe8d13@huawei.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Wed, Oct 21, 2020 at 10:20:11AM +0800, Chao Leng wrote: > > > On 2020/10/21 9:22, Ming Lei wrote: > > On Tue, Oct 20, 2020 at 05:04:29PM +0800, Chao Leng wrote: > > > > > > > > > On 2020/10/20 16:53, Ming Lei wrote: > > > > During controller's CONNECTING state, admin/fabric/connect requests > > > > are submitted for recovery controller, and we allow to abort this request > > > > directly in time out handler for not blocking setup procedure. > > > > > > > > So timout vs. normal completion race exists on these requests since > > > > admin/fabirc/connect queues won't be shutdown before handling timeout > > > > during CONNECTING state. > > > > > > > > Add atomic completion for requests from connect/fabric/admin queue for > > > > avoiding the race. > > > > > > > > CC: Chao Leng > > > > Cc: Sagi Grimberg > > > > Reported-by: Yi Zhang > > > > Tested-by: Yi Zhang > > > > Signed-off-by: Ming Lei > > > > --- > > > > drivers/nvme/host/tcp.c | 40 +++++++++++++++++++++++++++++++++++++--- > > > > 1 file changed, 37 insertions(+), 3 deletions(-) > > > > > > > > diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c > > > > index d6a3e1487354..7e85bd4a8d1b 100644 > > > > --- a/drivers/nvme/host/tcp.c > > > > +++ b/drivers/nvme/host/tcp.c > > > > @@ -30,6 +30,8 @@ static int so_priority; > > > > module_param(so_priority, int, 0644); > > > > MODULE_PARM_DESC(so_priority, "nvme tcp socket optimize priority"); > > > > +#define REQ_STATE_COMPLETE 0 > > > > + > > > > enum nvme_tcp_send_state { > > > > NVME_TCP_SEND_CMD_PDU = 0, > > > > NVME_TCP_SEND_H2C_PDU, > > > > @@ -56,6 +58,8 @@ struct nvme_tcp_request { > > > > size_t offset; > > > > size_t data_sent; > > > > enum nvme_tcp_send_state state; > > > > + > > > > + unsigned long comp_state; > > > I do not think adding state is a good idea. > > > It is similar to rq->state. > > > In the teardown process, after quiesced queues delete the timer and > > > cancel the timeout work maybe a better option. > > > I will send the patch later. > > > The patch is already tested with roce more than one week. > > > > Actually there isn't race between timeout and teardown, and patch 1 and patch > > 2 are enough to fix the issue reported by Yi. > > > > It is just that rq->state is updated to IDLE in its. complete(), so > > either one of code paths may think that this rq isn't completed, and > > patch 2 has addressed this issue. > > > > In short, teardown lock is enough to cover the race. > The race may cause abnormals: > 1. Reported by Yi Zhang > detail: https://lore.kernel.org/linux-nvme/1934331639.3314730.1602152202454.JavaMail.zimbra@redhat.com/ > 2. BUG_ON in blk_mq_requeue_request > Because error recovery and time out may repeated completion request. > First error recovery cancel request in tear down process, the request > will be retried in completion, rq->state will be changed to IDEL. Right. > And then time out will complete the request again, and samely retry > the request, BUG_ON will happen in blk_mq_requeue_request. With patch2 in this patchset, timeout handler won't complete the request any more. > 3. abnormal link disconnection > Firt error recovery cancel all request, reconnect success, the request > will be restarted. And then time out will complete the request again, > the queue will be stoped in nvme_rdma(tcp)_complete_timed_out, > Abnormal link diconnection will happen. The condition(time out process > is delayed long time by some reason such as hardware interrupt) is need. > So the probability is low. OK, the timeout handler may just get chance to run after recovery is done, and it can be fixed by calling nvme_sync_queues() after updating to CONNECTING or before updating to LIVE together with patch 1 & 2. > teardown_lock just serialize the race. and add checkint the rq->state can avoid > the 1 and 2 scenario, but 3 scenario can not be fixed. I didn't think of scenario 3, which seems not triggered in Yi's test. thanks, Ming From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3451BC388F2 for ; Wed, 21 Oct 2020 02:56:07 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id BF4FB22242 for ; Wed, 21 Oct 2020 02:56:06 +0000 (UTC) Authentication-Results: mail.kernel.org; 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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 21, 2020 at 10:20:11AM +0800, Chao Leng wrote: > > > On 2020/10/21 9:22, Ming Lei wrote: > > On Tue, Oct 20, 2020 at 05:04:29PM +0800, Chao Leng wrote: > > > > > > > > > On 2020/10/20 16:53, Ming Lei wrote: > > > > During controller's CONNECTING state, admin/fabric/connect requests > > > > are submitted for recovery controller, and we allow to abort this request > > > > directly in time out handler for not blocking setup procedure. > > > > > > > > So timout vs. normal completion race exists on these requests since > > > > admin/fabirc/connect queues won't be shutdown before handling timeout > > > > during CONNECTING state. > > > > > > > > Add atomic completion for requests from connect/fabric/admin queue for > > > > avoiding the race. > > > > > > > > CC: Chao Leng > > > > Cc: Sagi Grimberg > > > > Reported-by: Yi Zhang > > > > Tested-by: Yi Zhang > > > > Signed-off-by: Ming Lei > > > > --- > > > > drivers/nvme/host/tcp.c | 40 +++++++++++++++++++++++++++++++++++++--- > > > > 1 file changed, 37 insertions(+), 3 deletions(-) > > > > > > > > diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c > > > > index d6a3e1487354..7e85bd4a8d1b 100644 > > > > --- a/drivers/nvme/host/tcp.c > > > > +++ b/drivers/nvme/host/tcp.c > > > > @@ -30,6 +30,8 @@ static int so_priority; > > > > module_param(so_priority, int, 0644); > > > > MODULE_PARM_DESC(so_priority, "nvme tcp socket optimize priority"); > > > > +#define REQ_STATE_COMPLETE 0 > > > > + > > > > enum nvme_tcp_send_state { > > > > NVME_TCP_SEND_CMD_PDU = 0, > > > > NVME_TCP_SEND_H2C_PDU, > > > > @@ -56,6 +58,8 @@ struct nvme_tcp_request { > > > > size_t offset; > > > > size_t data_sent; > > > > enum nvme_tcp_send_state state; > > > > + > > > > + unsigned long comp_state; > > > I do not think adding state is a good idea. > > > It is similar to rq->state. > > > In the teardown process, after quiesced queues delete the timer and > > > cancel the timeout work maybe a better option. > > > I will send the patch later. > > > The patch is already tested with roce more than one week. > > > > Actually there isn't race between timeout and teardown, and patch 1 and patch > > 2 are enough to fix the issue reported by Yi. > > > > It is just that rq->state is updated to IDLE in its. complete(), so > > either one of code paths may think that this rq isn't completed, and > > patch 2 has addressed this issue. > > > > In short, teardown lock is enough to cover the race. > The race may cause abnormals: > 1. Reported by Yi Zhang > detail: https://lore.kernel.org/linux-nvme/1934331639.3314730.1602152202454.JavaMail.zimbra@redhat.com/ > 2. BUG_ON in blk_mq_requeue_request > Because error recovery and time out may repeated completion request. > First error recovery cancel request in tear down process, the request > will be retried in completion, rq->state will be changed to IDEL. Right. > And then time out will complete the request again, and samely retry > the request, BUG_ON will happen in blk_mq_requeue_request. With patch2 in this patchset, timeout handler won't complete the request any more. > 3. abnormal link disconnection > Firt error recovery cancel all request, reconnect success, the request > will be restarted. And then time out will complete the request again, > the queue will be stoped in nvme_rdma(tcp)_complete_timed_out, > Abnormal link diconnection will happen. The condition(time out process > is delayed long time by some reason such as hardware interrupt) is need. > So the probability is low. OK, the timeout handler may just get chance to run after recovery is done, and it can be fixed by calling nvme_sync_queues() after updating to CONNECTING or before updating to LIVE together with patch 1 & 2. > teardown_lock just serialize the race. and add checkint the rq->state can avoid > the 1 and 2 scenario, but 3 scenario can not be fixed. I didn't think of scenario 3, which seems not triggered in Yi's test. thanks, Ming _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme