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[209.132.183.28]) by mx.google.com with ESMTPS id m23si1890349qtn.102.2019.03.06.16.36.10 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 06 Mar 2019 16:36:10 -0800 (PST) Received-SPF: pass (google.com: domain of jglisse@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of jglisse@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=jglisse@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 5F4543082E53; Thu, 7 Mar 2019 00:36:09 +0000 (UTC) Received: from redhat.com (ovpn-125-142.rdu2.redhat.com [10.10.125.142]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 65C6B5D9CA; Thu, 7 Mar 2019 00:36:08 +0000 (UTC) Date: Wed, 6 Mar 2019 19:36:06 -0500 From: Jerome Glisse To: Andrew Morton Cc: Dan Williams , Linux MM , Linux Kernel Mailing List , Ralph Campbell , John Hubbard , linux-fsdevel Subject: Re: [PATCH 09/10] mm/hmm: allow to mirror vma of a file on a DAX backed filesystem Message-ID: <20190307003605.GB5528@redhat.com> References: <20190130030317.GC10462@redhat.com> <20190130183616.GB5061@redhat.com> <20190131041641.GK5061@redhat.com> <20190305141635.8134e310ba7187bc39532cd3@linux-foundation.org> <20190306154903.GA3230@redhat.com> <20190306141820.d60e47d6e173d6ec171f52cf@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190306141820.d60e47d6e173d6ec171f52cf@linux-foundation.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.46]); Thu, 07 Mar 2019 00:36:09 +0000 (UTC) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Mar 06, 2019 at 02:18:20PM -0800, Andrew Morton wrote: > On Wed, 6 Mar 2019 10:49:04 -0500 Jerome Glisse wrote: > > > On Tue, Mar 05, 2019 at 02:16:35PM -0800, Andrew Morton wrote: > > > On Wed, 30 Jan 2019 21:44:46 -0800 Dan Williams wrote: > > > > > > > > > > > > > > Another way to help allay these worries is commit to no new exports > > > > > > without in-tree users. In general, that should go without saying for > > > > > > any core changes for new or future hardware. > > > > > > > > > > I always intend to have an upstream user the issue is that the device > > > > > driver tree and the mm tree move a different pace and there is always > > > > > a chicken and egg problem. I do not think Andrew wants to have to > > > > > merge driver patches through its tree, nor Linus want to have to merge > > > > > drivers and mm trees in specific order. So it is easier to introduce > > > > > mm change in one release and driver change in the next. This is what > > > > > i am doing with ODP. Adding things necessary in 5.1 and working with > > > > > Mellanox to have the ODP HMM patch fully tested and ready to go in > > > > > 5.2 (the patch is available today and Mellanox have begin testing it > > > > > AFAIK). So this is the guideline i will be following. Post mm bits > > > > > with driver patches, push to merge mm bits one release and have the > > > > > driver bits in the next. I do hope this sound fine to everyone. > > > > > > > > The track record to date has not been "merge HMM patch in one release > > > > and merge the driver updates the next". If that is the plan going > > > > forward that's great, and I do appreciate that this set came with > > > > driver changes, and maintain hope the existing exports don't go > > > > user-less for too much longer. > > > > > > Decision time. Jerome, how are things looking for getting these driver > > > changes merged in the next cycle? > > > > nouveau is merge already. > > Confused. Nouveau in mainline is dependent upon "mm/hmm: allow to > mirror vma of a file on a DAX backed filesystem"? That can't be the > case? Not really, HMM mirror is about mirroring address space onto the device so if mirroring does not work for file that are on a filesystem that use DAX it fails in un-expected way from user point of view. But as nouveau is just getting upstrean you can argue that no one previously depended on that working for file backed page on DAX filesystem. Now the ODP RDMA case is different, what is upstream today works on DAX so if that patch is not upstream in 5.1 then i can not merge HMM ODP in 5.2 as it would regress and the ODP people would not take the risk of regression ie ODP folks want the DAX support to be upstream first. > > > > > > > Dan, what's your overall take on this series for a 5.1-rc1 merge? > > > > > > Jerome, what would be the risks in skipping just this [09/10] patch? > > > > As nouveau is a new user it does not regress anything but for RDMA > > mlx5 (which i expect to merge new window) it would regress that > > driver. > > Also confused. How can omitting "mm/hmm: allow to mirror vma of a file > on a DAX backed filesystem" from 5.1-rc1 cause an mlx5 regression? Not in 5.1 but i can not merge HMM ODP in 5.2 if that is not in 5.1. I know this circular dependency between sub-system is painful but i do not see any simpler way. Cheers, Jérôme