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=-6.9 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,SPF_HELO_NONE,SPF_PASS autolearn=no 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 27081C433E7 for ; Wed, 14 Oct 2020 01:08:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DA4E021582 for ; Wed, 14 Oct 2020 01:08:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="MC3Qu85z" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730815AbgJNBIh (ORCPT ); Tue, 13 Oct 2020 21:08:37 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:39187 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730814AbgJNBIg (ORCPT ); Tue, 13 Oct 2020 21:08:36 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1602637714; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=E/69ONf8FQ290l0+b/tZ1c1YE/U0q1L4yCfmk70YYnc=; b=MC3Qu85z3Yd83zZQ/GfAMIDsKIkSsTzQ7KL7mArfu9TP+GxqnAqDXCeAacAP2OtNBnbsab C+DMOc19kFXks5B/nuM+O9uUfnnIEToAvmLMT0pV6ditvtLxcVGfK/U7de8npd/k6FfzPN RyS/7AciOye+drN6ISMxuC+9OeSN9P4= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-591-Ir_DaHO7OsmFzFbumOpCXw-1; Tue, 13 Oct 2020 21:08:30 -0400 X-MC-Unique: Ir_DaHO7OsmFzFbumOpCXw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A715456BE8; Wed, 14 Oct 2020 01:08:28 +0000 (UTC) Received: from T590 (ovpn-12-36.pek2.redhat.com [10.72.12.36]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 641D16EF7D; Wed, 14 Oct 2020 01:08:17 +0000 (UTC) Date: Wed, 14 Oct 2020 09:08:13 +0800 From: Ming Lei To: Sagi Grimberg Cc: Chao Leng , Jens Axboe , Yi Zhang , linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, Keith Busch , Christoph Hellwig Subject: Re: [PATCH] block: re-introduce blk_mq_complete_request_sync Message-ID: <20201014010813.GA775684@T590> References: <20201009043938.GC27356@T590> <1711488120.3435389.1602219830518.JavaMail.zimbra@redhat.com> <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org 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. One solution is to apply the introduced blk_mq_complete_request_sync() in both two code paths. Another candidate is to use nvme_sync_queues() before teardown, such as the following change: diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c index d6a3e1487354..dc3561ca0074 100644 --- a/drivers/nvme/host/tcp.c +++ b/drivers/nvme/host/tcp.c @@ -1909,6 +1909,7 @@ static void nvme_tcp_teardown_io_queues(struct nvme_ctrl *ctrl, blk_mq_quiesce_queue(ctrl->admin_q); nvme_start_freeze(ctrl); nvme_stop_queues(ctrl); + nvme_sync_queues(ctrl); nvme_tcp_stop_io_queues(ctrl); if (ctrl->tagset) { blk_mq_tagset_busy_iter(ctrl->tagset, @@ -2171,14 +2172,11 @@ static void nvme_tcp_complete_timed_out(struct request *rq) struct nvme_tcp_request *req = blk_mq_rq_to_pdu(rq); struct nvme_ctrl *ctrl = &req->queue->ctrl->ctrl; - /* fence other contexts that may complete the command */ - mutex_lock(&to_tcp_ctrl(ctrl)->teardown_lock); nvme_tcp_stop_queue(ctrl, nvme_tcp_queue_id(req->queue)); if (!blk_mq_request_completed(rq)) { nvme_req(rq)->status = NVME_SC_HOST_ABORTED_CMD; blk_mq_complete_request(rq); } - mutex_unlock(&to_tcp_ctrl(ctrl)->teardown_lock); } static enum blk_eh_timer_return 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=-6.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 18FEFC433DF for ; Wed, 14 Oct 2020 01:08:49 +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 9A5FD20EDD for ; Wed, 14 Oct 2020 01:08:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="Xwpvxosf"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="boykALr6" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9A5FD20EDD Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=9vE43YmQWnVdO4pWMLTuWOxp4n4Xd3OKpXbztnEwSsc=; b=Xwpvxosftht8U5ycMVnJprFTf MnZc/Q5zjwuOKW7C5CV7zaJrOrpV2bGtG/e+g3TQOU6UXpE0kYjI6g2EqjFx8GuEeKZKZgyp8zDOG dqGpN1huconBgu25cgw6UJ7MZH3rCpatDezm6Q4AiJHbnJ8rtMKFxTghydDrUiViUHJN2ZGOKfFYl JF923bL6QvvmJCjMY3py+2rZEqzzITR2L36QTTcz+qbWs1J9V98DdJ5KN898N04CQ/V1D96reN669 qvwE2g/FPI62OvhSwTCcuSiR3YRRPvwGRvp9j1U3fb+GBOubE6rgFmlfCZeAPNyIW22s6IMvmD7P3 ocK+p5FuQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kSVHX-0004go-Bm; Wed, 14 Oct 2020 01:08:43 +0000 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kSVHR-0004fY-Rd for linux-nvme@lists.infradead.org; Wed, 14 Oct 2020 01:08:40 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1602637715; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=E/69ONf8FQ290l0+b/tZ1c1YE/U0q1L4yCfmk70YYnc=; b=boykALr6NnkD6OAVkk7fhpux8PK2wO9zP/0aULQkTojfMzT1iTXYt2Msa39MW5KBqJKueQ jkUfbnbbvPO1sKsrSRqP1Uf5LPZ3D/yNuUO1BSIDQz3/fD1Rhb/PgY3YVdh2RjQKKx/Iro mQAmVos764ul0fIjfhIiEftZNi4QX/Q= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-591-Ir_DaHO7OsmFzFbumOpCXw-1; Tue, 13 Oct 2020 21:08:30 -0400 X-MC-Unique: Ir_DaHO7OsmFzFbumOpCXw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A715456BE8; Wed, 14 Oct 2020 01:08:28 +0000 (UTC) Received: from T590 (ovpn-12-36.pek2.redhat.com [10.72.12.36]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 641D16EF7D; Wed, 14 Oct 2020 01:08:17 +0000 (UTC) Date: Wed, 14 Oct 2020 09:08:13 +0800 From: Ming Lei To: Sagi Grimberg Subject: Re: [PATCH] block: re-introduce blk_mq_complete_request_sync Message-ID: <20201014010813.GA775684@T590> References: <20201009043938.GC27356@T590> <1711488120.3435389.1602219830518.JavaMail.zimbra@redhat.com> <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> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201013_210837_954174_8FACF0F9 X-CRM114-Status: GOOD ( 26.96 ) 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 , linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, Chao Leng , 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 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. One solution is to apply the introduced blk_mq_complete_request_sync() in both two code paths. Another candidate is to use nvme_sync_queues() before teardown, such as the following change: diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c index d6a3e1487354..dc3561ca0074 100644 --- a/drivers/nvme/host/tcp.c +++ b/drivers/nvme/host/tcp.c @@ -1909,6 +1909,7 @@ static void nvme_tcp_teardown_io_queues(struct nvme_ctrl *ctrl, blk_mq_quiesce_queue(ctrl->admin_q); nvme_start_freeze(ctrl); nvme_stop_queues(ctrl); + nvme_sync_queues(ctrl); nvme_tcp_stop_io_queues(ctrl); if (ctrl->tagset) { blk_mq_tagset_busy_iter(ctrl->tagset, @@ -2171,14 +2172,11 @@ static void nvme_tcp_complete_timed_out(struct request *rq) struct nvme_tcp_request *req = blk_mq_rq_to_pdu(rq); struct nvme_ctrl *ctrl = &req->queue->ctrl->ctrl; - /* fence other contexts that may complete the command */ - mutex_lock(&to_tcp_ctrl(ctrl)->teardown_lock); nvme_tcp_stop_queue(ctrl, nvme_tcp_queue_id(req->queue)); if (!blk_mq_request_completed(rq)) { nvme_req(rq)->status = NVME_SC_HOST_ABORTED_CMD; blk_mq_complete_request(rq); } - mutex_unlock(&to_tcp_ctrl(ctrl)->teardown_lock); } static enum blk_eh_timer_return Thanks, Ming _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme