--- v9
+++ v7
@@ -1,38 +1,35 @@
-Commit 817be129e6f2 ("mm: validate get_user_pages_fast flags") allowed
-only FOLL_WRITE and FOLL_LONGTERM to be passed to get_user_pages_fast().
-This, combined with the fact that get_user_pages_fast() falls back to
-"slow gup", which *does* accept FOLL_FORCE, leads to an odd situation:
-if you need FOLL_FORCE, you cannot call get_user_pages_fast().
+After DMA is complete, and the device and CPU caches are synchronized,
+it's still required to mark the CPU pages as dirty, if the data was
+coming from the device. However, this driver was just issuing a
+bare put_page() call, without any set_page_dirty*() call.
-There does not appear to be any reason for filtering out FOLL_FORCE.
-There is nothing in the _fast() implementation that requires that we
-avoid writing to the pages. So it appears to have been an oversight.
+Fix the problem, by calling set_page_dirty_lock() if the CPU pages
+were potentially receiving data from the device.
-Fix by allowing FOLL_FORCE to be set for get_user_pages_fast().
-
-Fixes: 817be129e6f2 ("mm: validate get_user_pages_fast flags")
-Cc: Christoph Hellwig <hch@lst.de>
-Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
-Reviewed-by: Jan Kara <jack@suse.cz>
+Acked-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
+Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
- mm/gup.c | 3 ++-
- 1 file changed, 2 insertions(+), 1 deletion(-)
+ drivers/media/v4l2-core/videobuf-dma-sg.c | 5 ++++-
+ 1 file changed, 4 insertions(+), 1 deletion(-)
-diff --git a/mm/gup.c b/mm/gup.c
-index c0c56888e7cc..958ab0757389 100644
---- a/mm/gup.c
-+++ b/mm/gup.c
-@@ -2414,7 +2414,8 @@ int get_user_pages_fast(unsigned long start, int nr_pages,
- unsigned long addr, len, end;
- int nr = 0, ret = 0;
+diff --git a/drivers/media/v4l2-core/videobuf-dma-sg.c b/drivers/media/v4l2-core/videobuf-dma-sg.c
+index 66a6c6c236a7..28262190c3ab 100644
+--- a/drivers/media/v4l2-core/videobuf-dma-sg.c
++++ b/drivers/media/v4l2-core/videobuf-dma-sg.c
+@@ -349,8 +349,11 @@ int videobuf_dma_free(struct videobuf_dmabuf *dma)
+ BUG_ON(dma->sglen);
-- if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM)))
-+ if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM |
-+ FOLL_FORCE)))
- return -EINVAL;
-
- start = untagged_addr(start) & PAGE_MASK;
+ if (dma->pages) {
+- for (i = 0; i < dma->nr_pages; i++)
++ for (i = 0; i < dma->nr_pages; i++) {
++ if (dma->direction == DMA_FROM_DEVICE)
++ set_page_dirty_lock(dma->pages[i]);
+ put_page(dma->pages[i]);
++ }
+ kfree(dma->pages);
+ dma->pages = NULL;
+ }
--
2.24.0