Thread (57 messages) 57 messages, 11 authors, 2022-11-29
STALE1281d
Revisions (2)
  1. rfc [diff vs current]
  2. v1 current

[PATCH mm-unstable v1 16/20] mm/frame-vector: remove FOLL_FORCE usage

From: David Hildenbrand <hidden>
Date: 2022-11-16 10:40:13
Also in: dri-devel, linux-alpha, linux-arm-kernel, linux-fsdevel, linux-kselftest, linux-media, linux-mips, linux-mm, linux-perf-users, linux-rdma, linux-samsung-soc, linux-security-module, linux-um, lkml, sparclinux
Subsystem: media input infrastructure (v4l/dvb), the rest, videobuf2 framework · Maintainers: Mauro Carvalho Chehab, Linus Torvalds, Tomasz Figa, Marek Szyprowski

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 <redacted>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Tomasz Figa <tfiga@chromium.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: David Hildenbrand <redacted>
---
 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
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