On 16/11/2022 11:26, David Hildenbrand wrote:
GUP now supports reliable R/O long-term pinning in COW mappings, such that we break COW early. MAP_SHARED VMAs only use the shared zeropage so far in one corner case (DAXFS file with holes), which can be ignored because GUP does not support long-term pinning in fsdax (see check_vma_flags()).
Consequently, FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM is no longer required for reliable R/O long-term pinning: FOLL_LONGTERM is sufficient. So stop using FOLL_FORCE, which is really only for ptrace access.
Cc: Mauro Carvalho Chehab mchehab@kernel.org Signed-off-by: David Hildenbrand david@redhat.com
Acked-by: Hans Verkuil hverkuil-cisco@xs4all.nl
Looks good!
Hans
drivers/media/v4l2-core/videobuf-dma-sg.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-)
diff --git a/drivers/media/v4l2-core/videobuf-dma-sg.c b/drivers/media/v4l2-core/videobuf-dma-sg.c index f75e5eedeee0..234e9f647c96 100644 --- a/drivers/media/v4l2-core/videobuf-dma-sg.c +++ b/drivers/media/v4l2-core/videobuf-dma-sg.c @@ -151,17 +151,16 @@ static void videobuf_dma_init(struct videobuf_dmabuf *dma) static int videobuf_dma_init_user_locked(struct videobuf_dmabuf *dma, int direction, unsigned long data, unsigned long size) {
- unsigned int gup_flags = FOLL_LONGTERM; unsigned long first, last;
- int err, rw = 0;
- unsigned int flags = FOLL_FORCE;
- int err;
dma->direction = direction; switch (dma->direction) { case DMA_FROM_DEVICE:
rw = READ;
gup_flags |= FOLL_WRITE;
rw = WRITE;@@ -177,14 +176,11 @@ static int videobuf_dma_init_user_locked(struct videobuf_dmabuf *dma, if (NULL == dma->pages) return -ENOMEM;
- if (rw == READ)
flags |= FOLL_WRITE;- dprintk(1, "init user [0x%lx+0x%lx => %lu pages]\n", data, size, dma->nr_pages);
- err = pin_user_pages(data & PAGE_MASK, dma->nr_pages,
flags | FOLL_LONGTERM, dma->pages, NULL);
- err = pin_user_pages(data & PAGE_MASK, dma->nr_pages, gup_flags,
dma->pages, NULL);if (err != dma->nr_pages) { dma->nr_pages = (err >= 0) ? err : 0;