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[174.83.0.20]) by smtp.gmail.com with ESMTPSA id b6sm14324474qtq.29.2018.11.16.11.34.27 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 16 Nov 2018 11:34:28 -0800 (PST) Message-ID: <1542396866.13202.0.camel@redhat.com> Subject: Re: nvme: allow ANA support to be independent of native multipathing From: Laurence Oberman To: Mike Snitzer , Christoph Hellwig Cc: Hannes Reinecke , linux-nvme@lists.infradead.org, Keith Busch , Sagi Grimberg , axboe@kernel.dk, Martin Wilck , lijie , xose.vazquez@gmail.com, chengjike.cheng@huawei.com, shenhong09@huawei.com, dm-devel@redhat.com, wangzhoumengjian@huawei.com, christophe.varoqui@opensvc.com, bmarzins@redhat.com, sschremm@netapp.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Date: Fri, 16 Nov 2018 14:34:26 -0500 In-Reply-To: <20181116192802.GA30057@redhat.com> References: <20181114053837.GA15086@redhat.com> <30cf7af7-8826-55bd-e39a-4f81ed032f6d@suse.de> <20181114174746.GA18526@redhat.com> <87c931e5-4ac9-1795-8d40-cc5541d3ebcf@suse.de> <20181115174605.GA19782@redhat.com> <20181116091458.GA17267@lst.de> <37098edd-4dea-b58f-bca6-3be9af8ec4ee@suse.de> <20181116094947.GA19296@lst.de> <20181116101752.GA21531@lst.de> <20181116192802.GA30057@redhat.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6 (3.22.6-10.el7) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Fri, 2018-11-16 at 14:28 -0500, Mike Snitzer wrote: > On Fri, Nov 16 2018 at  5:17am -0500, > Christoph Hellwig wrote: > > > On Fri, Nov 16, 2018 at 11:06:32AM +0100, Hannes Reinecke wrote: > > > Ok, so would you be happy with making ANA support configurable? > > > > I've looked a bit over the whole situation, and what I think we > > need > > to do is: > > > >  a) warn if we see a ANA capable device without multipath support > >     so people know it is not going to work properly. > > I disagree with your cynicism but v2 of this patch now emits a > warning > accordingly. > > >  b) deprecate the multipath module option.  It was only intended as > >     a migration for any pre-existing PCIe multipath user if there > >     were any, not to support any new functionality.  So for 4.20 > >     put in a patch that prints a clear warning when it is used, > >     including a link to the nvme list, and then for 4.25 or so > >     remove it entirely unless something unexpected come up. > > You rejected the idea of allowing fine-grained control over whether > native NVMe multipathing is enabled or not on a per-namespace basis. > All we have is the coarse-grained nvme_core.multipath=N knob.  Now > you're forecasting removing even that.  Please don't do that. > > > This whole drama of optional multipath use has wasted way too much > > of everyones time already. > > It has wasted _way_ too much time. > > But the drama is born out of you rejecting that we need to preserve > multipath-tools and dm-multipath's ability to work across any > transport.  You don't need to do that work: Hannes, myself and others > have always been willing and able -- if you'd let us. > > IIRC it was at 2016's LSF in Boston where Ewan Milne and I had a > face-to-face conversation with you in the hallway track where you > agreed > that ANA support would be activated if the capability was advertised > by > the target.  The model we discussed is that it would be comparable to > how ALUA gets enabled during SCSI LUN discovery. > > I hope you can see your way forward to be more accommodating now. > Especially given the proposed changes are backed by NVMe standards. > > Please, PLEASE take v2 of this patch.. please? ;) > > Thanks, > Mike I am begging you take it too please Thanks Laurence