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[209.85.128.50]) by smtp.gmail.com with ESMTPSA id w4sm1431715edr.72.2020.10.07.05.55.35 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 07 Oct 2020 05:55:35 -0700 (PDT) Received: by mail-wm1-f50.google.com with SMTP id l11so2198192wmh.2 for ; Wed, 07 Oct 2020 05:55:35 -0700 (PDT) X-Received: by 2002:a1c:4904:: with SMTP id w4mr2925784wma.99.1602074886765; Wed, 07 Oct 2020 05:48:06 -0700 (PDT) MIME-Version: 1.0 References: <20201002175303.390363-1-daniel.vetter@ffwll.ch> <20201002175303.390363-2-daniel.vetter@ffwll.ch> <20201002180603.GL9916@ziepe.ca> <20201002233118.GM9916@ziepe.ca> <725819e9-4f07-3f04-08f8-b6180406b339@samsung.com> <20201007124409.GN5177@ziepe.ca> In-Reply-To: <20201007124409.GN5177@ziepe.ca> From: Tomasz Figa Date: Wed, 7 Oct 2020 14:47:55 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 2/2] mm/frame-vec: use FOLL_LONGTERM To: Jason Gunthorpe Cc: Marek Szyprowski , Daniel Vetter , DRI Development , LKML , Daniel Vetter , Andrew Morton , John Hubbard , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Jan Kara , Dan Williams , Linux MM , Linux ARM , Pawel Osciak , Kyungmin Park , Inki Dae , Joonyoung Shim , Seung-Woo Kim , linux-samsung-soc , "open list:DMA BUFFER SHARING FRAMEWORK" , Oded Gabbay Content-Type: text/plain; charset="UTF-8" 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, Oct 7, 2020 at 2:44 PM Jason Gunthorpe wrote: > > On Wed, Oct 07, 2020 at 02:33:56PM +0200, Marek Szyprowski wrote: > > Well, it was in vb2_get_vma() function, but now I see that it has been > > lost in fb639eb39154 and 6690c8c78c74 some time ago... > > There is no guarentee that holding a get on the file says anthing > about the VMA. This needed to check that the file was some special > kind of file that promised the VMA layout and file lifetime are > connected. > > Also, cloning a VMA outside the mm world is just really bad. That > would screw up many assumptions the drivers make. > > If it is all obsolete I say we hide it behind a default n config > symbol and taint the kernel if anything uses it. > > Add a big comment above the follow_pfn to warn others away from this > code. Sadly it's just verbally declared as deprecated and not formally noted anyway. There are a lot of userspace applications relying on user pointer support.