Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752833AbdLDQ3E (ORCPT ); Mon, 4 Dec 2017 11:29:04 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:33596 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752777AbdLDQDT (ORCPT ); Mon, 4 Dec 2017 11:03:19 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dan Williams , Jan Kara , Mauro Carvalho Chehab , Christoph Hellwig , Doug Ledford , Hal Rosenstock , Inki Dae , Jason Gunthorpe , Jeff Moyer , Joonyoung Shim , Kyungmin Park , Mel Gorman , Ross Zwisler , Sean Hefty , Seung-Woo Kim , Vlastimil Babka , Andrew Morton , Linus Torvalds Subject: [PATCH 4.14 11/95] v4l2: disable filesystem-dax mapping support Date: Mon, 4 Dec 2017 16:59:35 +0100 Message-Id: <20171204160046.649333945@linuxfoundation.org> X-Mailer: git-send-email 2.15.1 In-Reply-To: <20171204160046.206920966@linuxfoundation.org> References: <20171204160046.206920966@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2640 Lines: 66 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Dan Williams 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@dwillia2-desk3.amr.corp.intel.com Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings") Signed-off-by: Dan Williams Reported-by: Jan Kara Reviewed-by: Jan Kara Cc: Mauro Carvalho Chehab Cc: Christoph Hellwig Cc: Doug Ledford Cc: Hal Rosenstock Cc: Inki Dae Cc: Jason Gunthorpe Cc: Jeff Moyer Cc: Joonyoung Shim Cc: Kyungmin Park Cc: Mel Gorman Cc: Ross Zwisler Cc: Sean Hefty Cc: Seung-Woo Kim Cc: Vlastimil Babka Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- 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;