linux-kernel - [PATCH mm-unstable v1 16/20] mm/frame-vector: remove FOLL

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Message-Id: <20221116102659.70287-17-david@redhat.com>
Date:   Wed, 16 Nov 2022 11:26:55 +0100
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     x86@...nel.org, linux-alpha@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-ia64@...r.kernel.org,
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        etnaviv@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-samsung-soc@...r.kernel.org, linux-rdma@...r.kernel.org,
        linux-media@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-perf-users@...r.kernel.org,
        linux-security-module@...r.kernel.org,
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        Linus Torvalds <torvalds@...ux-foundation.org>,
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        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Hugh Dickins <hughd@...gle.com>, Nadav Amit <namit@...are.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Matthew Wilcox <willy@...radead.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Muchun Song <songmuchun@...edance.com>,
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        Oded Gabbay <ogabbay@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Christoph Hellwig <hch@...radead.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Hans Verkuil <hverkuil@...all.nl>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Tomasz Figa <tfiga@...omium.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Subject: [PATCH mm-unstable v1 16/20] mm/frame-vector: remove FOLL_FORCE usage

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 <hverkuil@...all.nl>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>
Cc: Tomasz Figa <tfiga@...omium.org>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>
Signed-off-by: David Hildenbrand <david@...hat.com>
---
 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;
-- 
2.38.1