[PATCH 3.16.y-ckt 126/133] UBI: block: Add missing cache flushes

[Luis Henriques]

3.16.7-ckt18 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Kevin Cernekee <cernekee at chromium.org>

commit 98fb1ffd8154890d7051750e61ff5548c3ee2ab2 upstream.

Block drivers are responsible for calling flush_dcache_page() on each
BIO request. This operation keeps the I$ coherent with the D$ on
architectures that don't have hardware coherency support. Without this
flush, random crashes are seen when executing user programs from an ext4
filesystem backed by a ubiblock device.

This patch is based on the change implemented in commit 2d4dc890b5c8
("block: add helpers to run flush_dcache_page() against a bio and a
request's pages").

Fixes: 9d54c8a33eec ("UBI: R/O block driver on top of UBI volumes")
Signed-off-by: Kevin Cernekee <cernekee at chromium.org>
Signed-off-by: Ezequiel Garcia <ezequiel.garcia at imgtec.com>
Signed-off-by: Richard Weinberger <richard at nod.at>
[ luis: backported to 3.16: used Kevin's backport to 3.14 ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/mtd/ubi/block.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/mtd/ubi/block.c b/drivers/mtd/ubi/block.c
index 8457df7ec5af..8b4a182d7cf9 100644
--- a/drivers/mtd/ubi/block.c
+++ b/drivers/mtd/ubi/block.c
@@ -255,6 +255,7 @@ static int do_ubiblock_request(struct ubiblock *dev, struct request *req)
 	mutex_lock(&dev->dev_mutex);
 	ret = ubiblock_read(dev, bio_data(req->bio), sec, len);
 	mutex_unlock(&dev->dev_mutex);
+	rq_flush_dcache_pages(req);
 
 	return ret;
 }