Re: [PATCH mm-unstable v1 16/20] mm/frame-vector: remove FOLL_FORCE usage
From: Daniel Vetter <hidden>
Date: 2022-11-16 11:04:39
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
On Wed, Nov 16, 2022 at 11:26:55AM +0100, 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 <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>Also code I looked at while looking at follow_pfn stuff Reviewed-by: Daniel Vetter <redacted>
quoted hunk ↗ jump to hunk
--- 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
-- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch