On Tue 14-11-17 11:56:39, Dan Williams wrote:
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 inki.dae@samsung.com Cc: Seung-Woo Kim sw0312.kim@samsung.com Cc: Joonyoung Shim jy0922.shim@samsung.com Cc: Kyungmin Park kyungmin.park@samsung.com Cc: Mauro Carvalho Chehab mchehab@kernel.org Cc: linux-media@vger.kernel.org Cc: Jan Kara jack@suse.cz Cc: Mel Gorman mgorman@suse.de Cc: Vlastimil Babka vbabka@suse.cz Cc: Andrew Morton akpm@linux-foundation.org Cc: stable@vger.kernel.org Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings") Signed-off-by: Dan Williams dan.j.williams@intel.com
Makes sense. I'd just note that in principle get_vaddr_frames() is no more long-term than get_user_pages(). It is just so that all the users of get_vaddr_frames() currently want a long-term reference. Maybe could you add here also a comment that the vma_is_fsdax() check is there because all users of this function want a long term page reference? With that you can add:
Reviewed-by: Jan Kara jack@suse.cz
Honza
mm/frame_vector.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/mm/frame_vector.c b/mm/frame_vector.c index 72ebec18629c..d2fdbeaadc8b 100644 --- a/mm/frame_vector.c +++ b/mm/frame_vector.c @@ -52,6 +52,10 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames, ret = -EFAULT; goto out; }
- if (vma_is_fsdax(vma))
return -EOPNOTSUPP;- if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) { vec->got_ref = true; vec->is_pfns = false;