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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id d34si824268pla.80.2019.02.04.11.09.36 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 04 Feb 2019 11:09:37 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) client-ip=2607:7c80:54:e::133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=FGUGQXDg; spf=pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=willy@infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=MtMB9MTpgmr1BCRNMWDvA5NXWtOVSM9dan7iTMIlXJQ=; b=FGUGQXDgOr8ZcEZwwE4Ok29No isAsaok6MHTNDkHfzs+oKLY+BVx4RxoDnK2NdDOUUlXrq0Dp0wpCbo+mFCPoGsI7Ht3QfesusXvSd Gb1R2G80avdRDh4s8V71Ge1MGJ7Y+G5JYyvNP7/4UKiEoTAS243rvxCxl24o4639/aisINDjmQH/8 3IPLiJ+8dM5eUIHJ21yBvcUI8lmF6Sc13jjKROMJz8vBZ3ZVMjlUG4RnP1ft7CP8X9niJG2iCE6aj C3E+Gr341sVnU6Awoyea9ahuSMzyPFV0p8gMMJSFTN3ZuVwWlwW3QX3kpfqkH3T3NenVu9AsyFgJq SAPhH+2XA==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1gqjcc-0008F9-Bv; Mon, 04 Feb 2019 19:09:34 +0000 Date: Mon, 4 Feb 2019 11:09:34 -0800 From: Matthew Wilcox To: Christopher Lameter Cc: Jason Gunthorpe , john.hubbard@gmail.com, Andrew Morton , linux-mm@kvack.org, Al Viro , Christian Benvenuti , Christoph Hellwig , Dan Williams , Dave Chinner , Dennis Dalessandro , Doug Ledford , Jan Kara , Jerome Glisse , Michal Hocko , Mike Rapoport , Mike Marciniszyn , Ralph Campbell , Tom Talpey , LKML , linux-fsdevel@vger.kernel.org, John Hubbard Subject: Re: [PATCH 0/6] RFC v2: mm: gup/dma tracking Message-ID: <20190204190934.GE21860@bombadil.infradead.org> References: <20190204052135.25784-1-jhubbard@nvidia.com> <01000168b980e880-a7d8e0db-84fb-4398-8269-149c66b701b4-000000@email.amazonses.com> <20190204175110.GA10237@ziepe.ca> <01000168b9be8b5a-3b4f8036-50c8-4180-b39f-9ef28cb60cce-000000@email.amazonses.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <01000168b9be8b5a-3b4f8036-50c8-4180-b39f-9ef28cb60cce-000000@email.amazonses.com> User-Agent: Mutt/1.9.2 (2017-12-15) 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 Mon, Feb 04, 2019 at 06:21:39PM +0000, Christopher Lameter wrote: > On Mon, 4 Feb 2019, Jason Gunthorpe wrote: > > > On Mon, Feb 04, 2019 at 05:14:19PM +0000, Christopher Lameter wrote: > > > Frankly I still think this does not solve anything. > > > > > > Concurrent write access from two sources to a single page is simply wrong. > > > You cannot make this right by allowing long term RDMA pins in a filesystem > > > and thus the filesystem can never update part of its files on disk. > > > > Fundamentally this patch series is fixing O_DIRECT to not crash the > > kernel in extreme cases.. RDMA has the same problem, but it is much > > easier to hit. > > O_DIRECT is the same issue. O_DIRECT addresses always have been in > anonymous memory or special file systems. That's never been a constraint that's existed.