Until there is a solution to the dma-to-dax vs truncate problem it is not safe to allow V4L2, Exynos, and other frame vector users to create long standing / irrevocable memory registrations against filesytem-dax vmas.
Cc: Inki Dae <[email protected]> Cc: Seung-Woo Kim <[email protected]> Cc: Joonyoung Shim <[email protected]> Cc: Kyungmin Park <[email protected]> Cc: Mauro Carvalho Chehab <[email protected]> Cc: [email protected] Cc: Mel Gorman <[email protected]> Cc: Vlastimil Babka <[email protected]> Cc: Andrew Morton <[email protected]> Cc: <[email protected]> Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings") Reviewed-by: Jan Kara <[email protected]> Signed-off-by: Dan Williams <[email protected]> --- mm/frame_vector.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/mm/frame_vector.c b/mm/frame_vector.c index 2f98df0d460e..297c7238f7d4 100644 --- a/mm/frame_vector.c +++ b/mm/frame_vector.c @@ -53,6 +53,18 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames, ret = -EFAULT; goto out; } + + /* + * While get_vaddr_frames() could be used for transient (kernel + * controlled lifetime) pinning of memory pages all current + * users establish long term (userspace controlled lifetime) + * page pinning. Treat get_vaddr_frames() like + * get_user_pages_longterm() and disallow it for filesystem-dax + * mappings. + */ + if (vma_is_fsdax(vma)) + return -EOPNOTSUPP; + if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) { vec->got_ref = true; vec->is_pfns = false;
