linux-kernel - [PATCH v2 2/4] mm: fail get_vaddr_frames() for filesystem-dax mappings

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Date:   Tue, 14 Nov 2017 11:56:39 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     akpm@...ux-foundation.org
Cc:     Jan Kara <jack@...e.cz>, Joonyoung Shim <jy0922.shim@...sung.com>,
        linux-nvdimm@...ts.01.org, Seung-Woo Kim <sw0312.kim@...sung.com>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Inki Dae <inki.dae@...sung.com>, linux-mm@...ck.org,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Mel Gorman <mgorman@...e.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>, linux-media@...r.kernel.org
Subject: [PATCH v2 2/4] mm: fail get_vaddr_frames() for filesystem-dax
 mappings

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@...sung.com>
Cc: Seung-Woo Kim <sw0312.kim@...sung.com>
Cc: Joonyoung Shim <jy0922.shim@...sung.com>
Cc: Kyungmin Park <kyungmin.park@...sung.com>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>
Cc: linux-media@...r.kernel.org
Cc: Jan Kara <jack@...e.cz>
Cc: Mel Gorman <mgorman@...e.de>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: <stable@...r.kernel.org>
Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings")
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
 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;