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 B0379C636CC for ; Wed, 15 Feb 2023 06:18:23 +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=y1tBEtqcOinftLT+Md7QoRoWwzj7KcsgBG07PqJnwsc=; b=Dxq+77ymsAG+rzQrWKWQCsmSLr sqyeSItJa7T5frVwDZPkgKmeUmyDMk1V6ZQu3rymAN0fqCG3Lqr2Jq2exixnaQcvKj3bbpT6m4A4k ElyLEmgV3gap3Fu2VJ5/h8bfu74n4NXpa35O7yF8OniaDesgyCTVbDCHHDTXGYDtUL03u2Gds7BPi 6w1jXMyCq2pIBZPhKA+ptmKVINneOmCCApLQmc7AIgJFhkg/3vCCrEJB2iw77nuzc3mEZkUusyzMh w36FBr48z0T7mTvgTbtxZtHkCD67Ws4KW8g/0glaYkKmh5fBaWSFB5lAwR2HKgPJ22wTOx15Izej8 ip7gZ7ng==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1pSB7T-004rDM-Cb; Wed, 15 Feb 2023 06:18:19 +0000 Received: from hch by bombadil.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pSB7Q-004rCz-Np; Wed, 15 Feb 2023 06:18:16 +0000 Date: Tue, 14 Feb 2023 22:18:16 -0800 From: Christoph Hellwig To: Keith Busch Cc: Sagi Grimberg , Christoph Hellwig , Ming Lei , John Meneghini , "linux-nvme@lists.infradead.org" Subject: Re: nvme/pcie hot plug results in /dev name change Message-ID: References: <472fe309-f0f9-65bf-1ad1-8a92a349e973@redhat.com> <2205fb9d-f887-dedc-04c1-06190dc51413@grimberg.me> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Mon, Feb 13, 2023 at 09:32:35AM -0700, Keith Busch wrote: > > Isn't this equivalent to dm-mpath queue_if_no_path or no_path_timeout ? > > Similiar, but generic to non-multipath devices. Exactly! > > We can keep the mpath device around, but if not, what is the desired > > behavior from the upper layers? > > I don't think we're looking for any behavioral changes in the upper layers. There's really two different things, which would both a problem: - make the device not go away if we expect it to come back by using the multipath code - tell the upper layer that a devie went away when it actually did Right now if user has a block device open, it will keep a reference to it forever. If we send a notification to the upper layer not only can it release that refrence, but it also knows the device went away. This really helps to e.g. rebalance data in a RAID or RAID-like setup.