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[212.51.149.33]) by smtp.gmail.com with ESMTPSA id g13-20020a50ec0d000000b0045b3853c4b7sm7352935edr.51.2022.11.16.02.48.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 16 Nov 2022 02:48:58 -0800 (PST) Date: Wed, 16 Nov 2022 11:48:56 +0100 From: Daniel Vetter To: David Hildenbrand Subject: Re: [PATCH mm-unstable v1 13/20] media: videobuf-dma-sg: remove FOLL_FORCE usage Message-ID: Mail-Followup-To: David Hildenbrand , linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org, Greg Kroah-Hartman , dri-devel@lists.freedesktop.org, linux-mm@kvack.org, Nadav Amit , linux-kselftest@vger.kernel.org, sparclinux@vger.kernel.org, Shuah Khan , Andrea Arcangeli , linux-samsung-soc@vger.kernel.org, linux-rdma@vger.kernel.org, x86@kernel.org, Hugh Dickins , Matthew Wilcox , Christoph Hellwig , Jason Gunthorpe , Vlastimil Babka , linux-media@vger.kernel.org, Arnd Bergmann , John Hubbard , linux-um@lists.infradead.org, etnaviv@lists.freedesktop.org, Alex Williamson , Peter Xu , Muchun Song , Mauro Carvalho Chehab , linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, Oded Gabbay , linux-mips@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-security-module@vger.kernel.org, linux-alpha@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton , Linus Torvalds , Mike Kravetz References: <20221116102659.70287-1-david@redhat.com> <20221116102659.70287-14-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221116102659.70287-14-david@redhat.com> X-Operating-System: Linux phenom 5.19.0-2-amd64 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-ia64@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-mips@vger.kernel.org, linux-mm@kvack.org, Nadav Amit , linux-kselftest@vger.kernel.org, sparclinux@vger.kernel.org, Shuah Khan , Andrea Arcangeli , linux-samsung-soc@vger.kernel.org, linux-rdma@vger.kernel.org, x86@kernel.org, Hugh Dickins , Matthew Wilcox , Christoph Hellwig , Jason Gunthorpe , linux-arm-kernel@lists.infradead.org, linux-media@vger.kernel.org, Arnd Bergmann , John Hubbard , linux-um@lists.infradead.org, etnaviv@lists.freedesktop.org, Alex Williamson , Peter Xu , Muchun Song , Mauro Carvalho Chehab , Vlastimil Babka , Greg Kroah-Hartman , Oded Gabbay , Linus Torvalds , linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-security-module@vger.kernel.org, linux-alpha@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton , linuxppc-dev@lists.ozlabs.org, Mike Kravetz Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, Nov 16, 2022 at 11:26:52AM +0100, David Hildenbrand wrote: > GUP now supports reliable R/O long-term pinning in COW mappings, such > that we break COW early. MAP_SHARED VMAs only use the shared zeropage so > far in one corner case (DAXFS file with holes), which can be ignored > because GUP does not support long-term pinning in fsdax (see > check_vma_flags()). > > Consequently, FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM is no longer required > for reliable R/O long-term pinning: FOLL_LONGTERM is sufficient. So stop > using FOLL_FORCE, which is really only for ptrace access. > > Cc: Mauro Carvalho Chehab > Signed-off-by: David Hildenbrand I looked at this a while ago when going through some of the follow_pfn stuff, so Reviewed-by: Daniel Vetter > --- > drivers/media/v4l2-core/videobuf-dma-sg.c | 14 +++++--------- > 1 file changed, 5 insertions(+), 9 deletions(-) > > diff --git a/drivers/media/v4l2-core/videobuf-dma-sg.c b/drivers/media/v4l2-core/videobuf-dma-sg.c > index f75e5eedeee0..234e9f647c96 100644 > --- a/drivers/media/v4l2-core/videobuf-dma-sg.c > +++ b/drivers/media/v4l2-core/videobuf-dma-sg.c > @@ -151,17 +151,16 @@ static void videobuf_dma_init(struct videobuf_dmabuf *dma) > static int videobuf_dma_init_user_locked(struct videobuf_dmabuf *dma, > int direction, unsigned long data, unsigned long size) > { > + unsigned int gup_flags = FOLL_LONGTERM; > unsigned long first, last; > - int err, rw = 0; > - unsigned int flags = FOLL_FORCE; > + int err; > > dma->direction = direction; > switch (dma->direction) { > case DMA_FROM_DEVICE: > - rw = READ; > + gup_flags |= FOLL_WRITE; > break; > case DMA_TO_DEVICE: > - rw = WRITE; > break; > default: > BUG(); > @@ -177,14 +176,11 @@ static int videobuf_dma_init_user_locked(struct videobuf_dmabuf *dma, > if (NULL == dma->pages) > return -ENOMEM; > > - if (rw == READ) > - flags |= FOLL_WRITE; > - > dprintk(1, "init user [0x%lx+0x%lx => %lu pages]\n", > data, size, dma->nr_pages); > > - err = pin_user_pages(data & PAGE_MASK, dma->nr_pages, > - flags | FOLL_LONGTERM, dma->pages, NULL); > + err = pin_user_pages(data & PAGE_MASK, dma->nr_pages, gup_flags, > + dma->pages, NULL); > > if (err != dma->nr_pages) { > dma->nr_pages = (err >= 0) ? err : 0; > -- > 2.38.1 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch