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=-5.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 8E38AC433E0 for ; Mon, 1 Feb 2021 09:40:59 +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 29CDE64EAE for ; Mon, 1 Feb 2021 09:40:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 29CDE64EAE Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.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-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=+e1qSU8Z6tCe/ubreAX4iLXzJvD5EPcQMSTxkZNde+s=; b=mFdSba6eNjQkjJZoWWl9Izqkw Xjy5uNYl9FN2TzRMBWXJGBOWOQYfv8b3kR4EVIhez883qCIFbpDsWWFxGLtcvy87KmdEInzQbKLwA u6QNdUuzIwpc5Vm6U98+bou8sPqAjIsy5UI4wjHE/LzB8nVFIllLJ6j4igTjA/xTdAPbVtC23eHHy ulkkEb5oJJaKNgcoQUlX3DXTeKvL/suzhfis4oD/DIChGxZ/NKbEcVSWaFoijH+2ENqiJaPkD77MJ p4DEojD3/wtkDnfWumRIDe/MABTKn6DqL3EXzQeNclv2L95CfaEjhZGE9/46ysAOPWLdU/9rHiki4 QZQQfguVQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l6VhV-0000GT-W2; Mon, 01 Feb 2021 09:40:54 +0000 Received: from szxga02-in.huawei.com ([45.249.212.188]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1l6VhR-0000EU-JU for linux-nvme@lists.infradead.org; Mon, 01 Feb 2021 09:40:51 +0000 Received: from DGGEMM405-HUB.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4DTjZj05Nwz5NJk; Mon, 1 Feb 2021 17:39:25 +0800 (CST) Received: from dggema772-chm.china.huawei.com (10.1.198.214) by DGGEMM405-HUB.china.huawei.com (10.3.20.213) with Microsoft SMTP Server (TLS) id 14.3.498.0; Mon, 1 Feb 2021 17:40:41 +0800 Received: from [10.169.42.93] (10.169.42.93) by dggema772-chm.china.huawei.com (10.1.198.214) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2106.2; Mon, 1 Feb 2021 17:40:40 +0800 Subject: Re: [PATCH v2] nvme-multipath: Early exit if no path is available To: Hannes Reinecke , Sagi Grimberg , "Daniel Wagner" References: <20210127103033.15318-1-dwagner@suse.de> <20210128075837.u5u56t23fq5gu6ou@beryllium.lan> <69575290-200e-b4a1-4269-c71e4c2cc37b@huawei.com> <20210128094004.erwnszjqcxlsi2kd@beryllium.lan> <675d3cf7-1ae8-adc5-b6d0-359fe10f6b23@grimberg.me> <59cd053e-46cb-0235-141f-4ce919c93f48@huawei.com> <65392653-6b03-9195-f686-5fe4b3290bd2@suse.de> <81b22bbf-4dd3-6161-e63a-9699690a4e4f@huawei.com> <715dd943-0587-be08-2840-e0948cf0bc62@suse.de> <6ceff3cb-c9e9-7e74-92f0-dd745987c943@huawei.com> <114751ac-1f7d-ce5e-12c5-7d6303bdb999@suse.de> <47a1b796-9d91-5947-4bac-dd8f397041a3@suse.de> From: Chao Leng Message-ID: Date: Mon, 1 Feb 2021 17:40:40 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <47a1b796-9d91-5947-4bac-dd8f397041a3@suse.de> Content-Language: en-US X-Originating-IP: [10.169.42.93] X-ClientProxiedBy: dggeme715-chm.china.huawei.com (10.1.199.111) To dggema772-chm.china.huawei.com (10.1.198.214) X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210201_044051_082613_4C50FBF0 X-CRM114-Status: GOOD ( 13.64 ) 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 , Keith Busch , linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, Christoph Hellwig Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On 2021/2/1 16:57, Hannes Reinecke wrote: > On 2/1/21 9:47 AM, Chao Leng wrote: >> >> >> On 2021/2/1 15:29, Hannes Reinecke wrote:[ .. ] >>> Urgh. Please, no. That is well impossible to debug. >>> Can you please open-code it to demonstrate where the difference to the current (and my fixed) versions is? >>> I'm still not clear where the problem is once we applied both patches. >> For example assume the list has three path, and all path is not NVME_ANA_OPTIMIZED: >> head->next = ns1; >> ns1->next = ns2; >> ns2->next = head; >> old->next = ns2; >> > And this is where I have issues with. > Where does 'old' come from? > Clearly it was part of the list at one point; so what happened to it? I explained this earlier. In nvme_ns_remove, there is a hole between list_del_rcu and nvme_mpath_clear_current_path. If head->current_path is the "old", and the "old" is removing. The "old" is already removed from the list by list_del_rcu, but head->current_path is not clear to NULL by nvme_mpath_clear_current_path. Find path is race with nvme_ns_remove, use the "old" pass to nvme_round_robin_path to find path. > > Cheers, > > Hannes _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme