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 9A338C433DF for ; Wed, 14 Oct 2020 09:57:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3CB93207C3 for ; Wed, 14 Oct 2020 09:57:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="PLl+78A8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728629AbgJNJ5Q (ORCPT ); Wed, 14 Oct 2020 05:57:16 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:31105 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728579AbgJNJ5F (ORCPT ); Wed, 14 Oct 2020 05:57:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1602669422; 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=O+Nfo7CPvqON4B3Kn47TT+yFPZmeO35wHPJpTlz7u8g=; b=PLl+78A8Pd6S0t7MCPnY6sr/w2a/ojnkxvUERzJr6uu+3KbrizGt+T6pLd9eV6jDj80r96 uJi0ViJHlAB/krVwA3/YtH2392Nj2m4DHftgsZ1NGNeUXcLE1r2eHvSZfBPxNZlY2UFDFa g1bwlOd14XRgxzXY8e9QEf/DcfEiSPc= 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-427-J3VBtSrYNCmOJPeN5WNKvw-1; 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 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: <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-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.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