mm/frame-vector: remove FOLL_FORCE usage

FOLL_FORCE is really only for ptrace access. According to commit
70794724 ("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 70794724 ("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.

Link: https://lkml.kernel.org/r/20221116102659.70287-17-david@redhat.comSigned-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Acked-by: Tomasz Figa <tfiga@chromium.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

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;