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 BB3DAC433E7 for ; Wed, 14 Oct 2020 02:03:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 70023221FF for ; Wed, 14 Oct 2020 02:03:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="cA1pPt3e" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727159AbgJNCD3 (ORCPT ); Tue, 13 Oct 2020 22:03:29 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:20324 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725874AbgJNCD3 (ORCPT ); Tue, 13 Oct 2020 22:03:29 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1602641007; 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=ZnBS0lxFc4aRI5IPnBKqaaP5VKiZUfUv2cEuSMjVCR4=; b=cA1pPt3ehDDr8M/MPSbV4bKxgn5G3lBZq1o3P+GQ8YhHFhwZJMUUuCxFQ9XMURi5KwW3Et I3d1kuDYxufdmgw/xhVsMb/dLkib5oVbsWOeS+V/6yUH2J7XET8H9KBb5cZtfxcjZH1HMs +T/MAcc2XGsGZiOqRQcMI+sb/Y1+JxI= 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-228-SlNewCraPw2HPxMnv_OmPQ-1; Tue, 13 Oct 2020 22:03:22 -0400 X-MC-Unique: SlNewCraPw2HPxMnv_OmPQ-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2785E879535; Wed, 14 Oct 2020 02:03:21 +0000 (UTC) Received: from T590 (ovpn-12-36.pek2.redhat.com [10.72.12.36]) by smtp.corp.redhat.com (Postfix) with ESMTPS id EE29B5DA8C; Wed, 14 Oct 2020 02:03:06 +0000 (UTC) Date: Wed, 14 Oct 2020 10:02:57 +0800 From: Ming Lei To: Chao Leng Cc: Sagi Grimberg , 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: <20201014020257.GB775684@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Wed, Oct 14, 2020 at 09:37:07AM +0800, Chao Leng wrote: > rdma also need do this patch. > We do test this patch with nvme over roce a few days, now work well. > > On 2020/10/14 9:08, 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. > > > > 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_sync_queues now sync io queues and admin queues, so we may need like this: > nvme_sync_io_queues(struct nvme_ctrl *ctrl) > { > down_read(&ctrl->namespaces_rwsem); > list_for_each_entry(ns, &ctrl->namespaces, list) > blk_sync_queue(ns->queue); > up_read(&ctrl->namespaces_rwsem); > } Looks not necessary to do that, because admin queue is quiesced in nvme_tcp_teardown_io_queues(), so it is safe to sync admin queue here too. Thanks, Ming