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[209.85.208.45]) by smtp.gmail.com with ESMTPSA id t25-20020a1709064f1900b007be886f0db5sm2109533eju.209.2022.11.28.00.58.04 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 28 Nov 2022 00:58:04 -0800 (PST) Received: by mail-ed1-f45.google.com with SMTP id l11so14483448edb.4 for ; Mon, 28 Nov 2022 00:58:04 -0800 (PST) X-Received: by 2002:aa7:db98:0:b0:46a:d57:d9d0 with SMTP id u24-20020aa7db98000000b0046a0d57d9d0mr25216647edt.113.1669625884043; Mon, 28 Nov 2022 00:58:04 -0800 (PST) MIME-Version: 1.0 References: <20221116102659.70287-1-david@redhat.com> <20221116102659.70287-17-david@redhat.com> <81fb0fa3-2e06-b765-56ac-a7d981194e59@redhat.com> <08b65ac6-6786-1080-18f8-d2be109c85fc@xs4all.nl> <9d0bf98a-3d6a-1082-e992-1338e1525935@redhat.com> In-Reply-To: <9d0bf98a-3d6a-1082-e992-1338e1525935@redhat.com> From: Tomasz Figa Date: Mon, 28 Nov 2022 17:57:51 +0900 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH mm-unstable v1 16/20] mm/frame-vector: remove FOLL_FORCE usage To: David Hildenbrand Cc: Hans Verkuil , linux-kernel@vger.kernel.org, Andrew Morton , x86@kernel.org, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, etnaviv@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-samsung-soc@vger.kernel.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-perf-users@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kselftest@vger.kernel.org, Linus Torvalds , Jason Gunthorpe , John Hubbard , Peter Xu , Greg Kroah-Hartman , Andrea Arcangeli , Hugh Dickins , Nadav Amit , Vlastimil Babka , Matthew Wilcox , Mike Kravetz , Muchun Song , Shuah Khan , Lucas Stach , David Airlie , Oded Gabbay , Arnd Bergmann , Christoph Hellwig , Alex Williamson , Marek Szyprowski , Mauro Carvalho Chehab Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org On Mon, Nov 28, 2022 at 5:19 PM David Hildenbrand wrote: > > On 28.11.22 09:17, Hans Verkuil wrote: > > Hi David, > > > > On 27/11/2022 11:35, David Hildenbrand wrote: > >> On 16.11.22 11:26, David Hildenbrand wrote: > >>> FOLL_FORCE is really only for ptrace access. According to commit > >>> 707947247e95 ("media: videobuf2-vmalloc: get_userptr: buffers are always > >>> writable"), get_vaddr_frames() currently pins all pages writable as a > >>> workaround for issues with read-only buffers. > >>> > >>> FOLL_FORCE, however, seems to be a legacy leftover as it predates > >>> commit 707947247e95 ("media: videobuf2-vmalloc: get_userptr: buffers are > >>> always writable"). Let's just remove it. > >>> > >>> Once the read-only buffer issue has been resolved, FOLL_WRITE could > >>> again be set depending on the DMA direction. > >>> > >>> Cc: Hans Verkuil > >>> Cc: Marek Szyprowski > >>> Cc: Tomasz Figa > >>> Cc: Marek Szyprowski > >>> Cc: Mauro Carvalho Chehab > >>> Signed-off-by: David Hildenbrand > >>> --- > >>> drivers/media/common/videobuf2/frame_vector.c | 2 +- > >>> 1 file changed, 1 insertion(+), 1 deletion(-) > >>> > >>> diff --git a/drivers/media/common/videobuf2/frame_vector.c b/drivers/media/common/videobuf2/frame_vector.c > >>> index 542dde9d2609..062e98148c53 100644 > >>> --- a/drivers/media/common/videobuf2/frame_vector.c > >>> +++ b/drivers/media/common/videobuf2/frame_vector.c > >>> @@ -50,7 +50,7 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames, > >>> start = untagged_addr(start); > >>> ret = pin_user_pages_fast(start, nr_frames, > >>> - FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM, > >>> + FOLL_WRITE | FOLL_LONGTERM, > >>> (struct page **)(vec->ptrs)); > >>> if (ret > 0) { > >>> vec->got_ref = true; > >> > >> > >> Hi Andrew, > >> > >> see the discussion at [1] regarding a conflict and how to proceed with > >> upstreaming. The conflict would be easy to resolve, however, also > >> the patch description doesn't make sense anymore with [1]. > > > > Might it be easier and less confusing if you post a v2 of this series > > with my patch first? That way it is clear that 1) my patch has to come > > first, and 2) that it is part of a single series and should be merged > > by the mm subsystem. > > > > Less chances of things going wrong that way. > > > > Just mention in the v2 cover letter that the first patch was added to > > make it easy to backport that fix without being hampered by merge > > conflicts if it was added after your frame_vector.c patch. > > Yes, that's the way I would naturally do, it, however, Andrew prefers > delta updates for minor changes. > > @Andrew, whatever you prefer! > > Thanks! > However you folks proceed with taking this patch, feel free to add my Acked-by. Thanks! Best regards, Tomasz > -- > Thanks, > > David / dhildenb >