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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,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 04BF5C3A5A8 for ; Wed, 4 Sep 2019 15:56:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CE6F122CED for ; Wed, 4 Sep 2019 15:56:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567612580; bh=RMh5SN41NZE5u/rDTqAA4+0804mMUI9Vm26Q35MpjWA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=UhibJWT9zPkOyE9k5iFqAQjzHJ5zvxWbPAe+MwAqK+XUgLblc0BIWd4NqR9b1n3gB kcl/lEiRGn54/TAhMV1BliR2vJXRocH5WbRKwetvfXlEKQTFz8d6dPZvy+pYE8OrIN Kc9ozoYLSBahzg5y+xWVgDI+G4kdeecsBbtd0zrQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731506AbfIDP4T (ORCPT ); Wed, 4 Sep 2019 11:56:19 -0400 Received: from mga01.intel.com ([192.55.52.88]:10024 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727967AbfIDP4R (ORCPT ); Wed, 4 Sep 2019 11:56:17 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 04 Sep 2019 08:56:16 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,467,1559545200"; d="scan'208";a="199059841" Received: from unknown (HELO localhost.localdomain) ([10.232.112.69]) by fmsmga001.fm.intel.com with ESMTP; 04 Sep 2019 08:56:16 -0700 Date: Wed, 4 Sep 2019 09:54:45 -0600 From: Keith Busch To: Christoph Hellwig Cc: Jens Axboe , Hannes Reinecke , Sagi Grimberg , "Martin K . Petersen" , linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, Keith Busch , Logan Gunthorpe Subject: Re: [PATCH] nvme-core: Fix subsystem instance mismatches Message-ID: <20190904155445.GD21302@localhost.localdomain> References: <20190831000139.7662-1-logang@deltatee.com> <20190831152910.GA29439@localhost.localdomain> <33af4d94-9f6d-9baa-01fa-0f75ccee263e@deltatee.com> <20190903164620.GA20847@localhost.localdomain> <20190904060558.GA10849@lst.de> <20190904144426.GB21302@localhost.localdomain> <20190904154215.GA20422@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190904154215.GA20422@lst.de> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 04, 2019 at 05:42:15PM +0200, Christoph Hellwig wrote: > On Wed, Sep 04, 2019 at 08:44:27AM -0600, Keith Busch wrote: > > Let me step through an example: > > > > Ctrl A gets instance 0. > > > > Its subsystem gets the same instance, and takes ref count on it: > > all namespaces in this subsystem will use '0'. > > > > Ctrl B gets instance 1, and it's in the same subsystem as Ctrl A so > > no new subsytem is allocated. > > > > Ctrl A is disconnected, dropping its ref on instance 0, but the > > subsystem still has its refcount, making it unavailable. > > > > Ctrl A is reconnected, and allocates instance 2 because 0 is still in > > use. > > > > Now all the namespaces in this subsystem are prefixed with nvme0, but no > > controller exists with the same prefix. We still have inevitable naming > > mismatch, right? > > I think th major confusion was that we can use the same handle for > and unrelated subsystem vs controller, and that would avoid it. > > I don't see how we can avoid the controller is entirely different > from namespace problem ever. Can we just ensure there is never a matching controller then? This patch will accomplish that and simpler than wrapping the instance in a refcount'ed object: http://lists.infradead.org/pipermail/linux-nvme/2019-May/024142.html