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 hverkuil@xs4all.nl 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 david@redhat.com
Also code I looked at while looking at follow_pfn stuff
Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch
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));-- 2.38.1