This is a note to let you know that I've just added the patch titled

v4l2: disable filesystem-dax mapping support

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: v4l2-disable-filesystem-dax-mapping-support.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From b70131de648c2b997d22f4653934438013f407a1 Mon Sep 17 00:00:00 2001

From: Dan Williams dan.j.williams@intel.com Date: Wed, 29 Nov 2017 16:10:43 -0800 Subject: v4l2: disable filesystem-dax mapping support

From: Dan Williams dan.j.williams@intel.com

commit b70131de648c2b997d22f4653934438013f407a1 upstream.

V4L2 memory registrations are incompatible with filesystem-dax that needs the ability to revoke dma access to a mapping at will, or otherwise allow the kernel to wait for completion of DMA. The filesystem-dax implementation breaks the traditional solution of truncate of active file backed mappings since there is no page-cache page we can orphan to sustain ongoing DMA.

If v4l2 wants to support long lived DMA mappings it needs to arrange to hold a file lease or use some other mechanism so that the kernel can coordinate revoking DMA access when the filesystem needs to truncate mappings.

Link: http://lkml.kernel.org/r/151068940499.7446.12846708245365671207.stgit@dwilli... Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings") Signed-off-by: Dan Williams dan.j.williams@intel.com Reported-by: Jan Kara jack@suse.cz Reviewed-by: Jan Kara jack@suse.cz Cc: Mauro Carvalho Chehab mchehab@kernel.org Cc: Christoph Hellwig hch@lst.de Cc: Doug Ledford dledford@redhat.com Cc: Hal Rosenstock hal.rosenstock@gmail.com Cc: Inki Dae inki.dae@samsung.com Cc: Jason Gunthorpe jgg@mellanox.com Cc: Jeff Moyer jmoyer@redhat.com Cc: Joonyoung Shim jy0922.shim@samsung.com Cc: Kyungmin Park kyungmin.park@samsung.com Cc: Mel Gorman mgorman@suse.de Cc: Ross Zwisler ross.zwisler@linux.intel.com Cc: Sean Hefty sean.hefty@intel.com Cc: Seung-Woo Kim sw0312.kim@samsung.com Cc: Vlastimil Babka vbabka@suse.cz Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- drivers/media/v4l2-core/videobuf-dma-sg.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/media/v4l2-core/videobuf-dma-sg.c +++ b/drivers/media/v4l2-core/videobuf-dma-sg.c @@ -185,12 +185,13 @@ static int videobuf_dma_init_user_locked dprintk(1, "init user [0x%lx+0x%lx => %d pages]\n", data, size, dma->nr_pages);

- err = get_user_pages(data & PAGE_MASK, dma->nr_pages, + err = get_user_pages_longterm(data & PAGE_MASK, dma->nr_pages, flags, dma->pages, NULL);

if (err != dma->nr_pages) { dma->nr_pages = (err >= 0) ? err : 0; - dprintk(1, "get_user_pages: err=%d [%d]\n", err, dma->nr_pages); + dprintk(1, "get_user_pages_longterm: err=%d [%d]\n", err, + dma->nr_pages); return err < 0 ? err : -EINVAL; } return 0;

Patches currently in stable-queue which might be from dan.j.williams@intel.com are

queue-4.14/mm-hugetlbfs-introduce-split-to-vm_operations_struct.patch queue-4.14/ib-core-disable-memory-registration-of-filesystem-dax-vmas.patch queue-4.14/mm-introduce-get_user_pages_longterm.patch queue-4.14/mm-fail-get_vaddr_frames-for-filesystem-dax-mappings.patch queue-4.14/device-dax-implement-split-to-catch-invalid-munmap-attempts.patch queue-4.14/v4l2-disable-filesystem-dax-mapping-support.patch queue-4.14/mm-fix-device-dax-pud-write-faults-triggered-by-get_user_pages.patch queue-4.14/mm-madvise.c-fix-madvise-infinite-loop-under-special-circumstances.patch