linux-kernel - [RFC/PATCH 5/5] media: vb2: use FOLL_DURABLE and __get_user

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Date:	Tue, 05 Mar 2013 07:57:59 +0100
From:	Marek Szyprowski <m.szyprowski@...sung.com>
To:	linux-mm@...ck.org, linaro-mm-sig@...ts.linaro.org,
	linux-kernel@...r.kernel.org
Cc:	Marek Szyprowski <m.szyprowski@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Arnd Bergmann <arnd@...db.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>,
	Michal Nazarewicz <mina86@...a86.com>,
	Minchan Kim <minchan@...nel.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: [RFC/PATCH 5/5] media: vb2: use FOLL_DURABLE and __get_user_pages() to
 avoid CMA migration issues

V4L2 devices usually grab additional references to user pages for a very
long period of time, what causes permanent migration failures if the given
page has been allocated from CMA pageblock. By setting FOLL_DURABLE flag,
videobuf2 will instruct __get_user_pages() to migrate user pages out of
CMA pageblocks before blocking them with an additional reference.

Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@...sung.com>
---
 drivers/media/v4l2-core/videobuf2-dma-contig.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
index 10beaee..70649ab 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
@@ -443,9 +443,13 @@ static int vb2_dc_get_user_pages(unsigned long start, struct page **pages,
 		}
 	} else {
 		int n;
+		int flags = FOLL_TOUCH | FOLL_GET | FOLL_FORCE | FOLL_DURABLE;
 
-		n = get_user_pages(current, current->mm, start & PAGE_MASK,
-			n_pages, write, 1, pages, NULL);
+		if (write)
+			flags |= FOLL_WRITE;
+
+		n = __get_user_pages(current, current->mm, start & PAGE_MASK,
+			n_pages, flags, pages, NULL, NULL);
 		/* negative error means that no page was pinned */
 		n = max(n, 0);
 		if (n != n_pages) {
-- 
1.7.9.5

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