4.14-stable review patch. If anyone has any objections, please let me know.
------------------ From: Dan Williams <[email protected]> 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.st...@dwillia2-desk3.amr.corp.intel.com Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings") Signed-off-by: Dan Williams <[email protected]> Reported-by: Jan Kara <[email protected]> Reviewed-by: Jan Kara <[email protected]> Cc: Mauro Carvalho Chehab <[email protected]> Cc: Christoph Hellwig <[email protected]> Cc: Doug Ledford <[email protected]> Cc: Hal Rosenstock <[email protected]> Cc: Inki Dae <[email protected]> Cc: Jason Gunthorpe <[email protected]> Cc: Jeff Moyer <[email protected]> Cc: Joonyoung Shim <[email protected]> Cc: Kyungmin Park <[email protected]> Cc: Mel Gorman <[email protected]> Cc: Ross Zwisler <[email protected]> Cc: Sean Hefty <[email protected]> Cc: Seung-Woo Kim <[email protected]> Cc: Vlastimil Babka <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- 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;
