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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 1F295C369A1 for ; Wed, 9 Apr 2025 10:43:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=YViNYDQw4VsdudezqF3bvfbHcUGdp4pjcccRrbiYMys=; b=husgwrZifPN3iZzdgd77BLs7uX 2CdapdDiNoStbZZ+Pf6rn+CWtu/Nzk529DYOrwa6Dhg42O2wVvNMGH1FibkNcWcUG5J34ICgfkuzB d/SgeR7EObcFEmZ8m/HCw36D5CERXPGh+9fZFr4kWmqkaVcpQQBz39R3mFqtvM4G7f/yA1/qmEePm eO1XsrIGrvZIz4A3WhTzsAWXvSweE/0b9YHtRu1p6wQX6xtPUiFrpwpTVmS2aE3TpLYYYiB7nX6vU jfwKDV+F0zGIHNpVP/H4h9DIXnFQ5Hp0tuL+8nSmxDG7euOH0q6kWzsKAQWOafgBIIf/ZtcE92Hbi cy8FCGSw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1u2Su5-00000006sOh-1Vxl; Wed, 09 Apr 2025 10:43:33 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1u2Su2-00000006sNp-41NK for linux-nvme@lists.infradead.org; Wed, 09 Apr 2025 10:43:32 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 56BBB68AA6; Wed, 9 Apr 2025 12:43:26 +0200 (CEST) Date: Wed, 9 Apr 2025 12:43:26 +0200 From: Christoph Hellwig To: Nilay Shroff Cc: Christoph Hellwig , linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, kbusch@kernel.org, hare@suse.de, sagi@grimberg.me, jmeneghi@redhat.com, axboe@kernel.dk, gjoyce@ibm.com Subject: Re: [RFC PATCH 1/2] nvme-multipath: introduce delayed removal of the multipath head node Message-ID: <20250409104326.GA5359@lst.de> References: <20250321063901.747605-1-nilay@linux.ibm.com> <20250321063901.747605-2-nilay@linux.ibm.com> <20250407144413.GA12216@lst.de> <5db5ab7b-fdf2-4b40-86fc-3ab4ccff9a41@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5db5ab7b-fdf2-4b40-86fc-3ab4ccff9a41@linux.ibm.com> User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250409_034331_151132_D61D1516 X-CRM114-Status: GOOD ( 17.47 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Tue, Apr 08, 2025 at 07:37:48PM +0530, Nilay Shroff wrote: > >> + * For non-fabric controllers we support delayed removal of head disk > >> + * node. If we reached up to here then it means that head disk is still > >> + * alive and so we assume here that even if there's no path available > >> + * maybe due to the transient link failure, we could queue up the IO > >> + * and later when path becomes ready we re-submit queued IO. > >> + */ > >> + if (!(test_bit(NVME_NSHEAD_FABRICS, &head->flags))) > >> + return true; > > > > Why is this conditional on fabrics or not? The same rationale should > > apply as much if not more for fabrics controllers. > > > For fabrics we already have options like "reconnect_delay" and > "max_reconnects". So in case of fabric link failures, we delay > the removal of the head disk node based on those options. Yes. But having entirely different behavior for creating a multipath node and removing it still seems like a rather bad idea.