[PATCH 3.16.y-ckt 112/180] md/raid0: fix bug with chunksize not a power of 2.

[Luis Henriques]

3.16.7-ckt11 -stable review patch.  If anyone has any objections, please let me know.

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

From: NeilBrown <neilb at suse.de>

commit 47d68979cc968535cb87f3e5f2e6a3533ea48fbd upstream.

Since commit 20d0189b1012a37d2533a87fb451f7852f2418d1
in v3.14-rc1 RAID0 has performed incorrect calculations
when the chunksize is not a power of 2.

This happens because "sector_div()" modifies its first argument, but
this wasn't taken into account in the patch.

So restore that first arg before re-using the variable.

Reported-by: Joe Landman <joe.landman at gmail.com>
Reported-by: Dave Chinner <david at fromorbit.com>
Fixes: 20d0189b1012a37d2533a87fb451f7852f2418d1
Signed-off-by: NeilBrown <neilb at suse.de>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/md/raid0.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index 407a99e46f69..683e685ed697 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -320,7 +320,7 @@ static struct strip_zone *find_zone(struct r0conf *conf,
 
 /*
  * remaps the bio to the target device. we separate two flows.
- * power 2 flow and a general flow for the sake of perfromance
+ * power 2 flow and a general flow for the sake of performance
 */
 static struct md_rdev *map_sector(struct mddev *mddev, struct strip_zone *zone,
 				sector_t sector, sector_t *sector_offset)
@@ -538,6 +538,7 @@ static void raid0_make_request(struct mddev *mddev, struct bio *bio)
 			split = bio;
 		}
 
+		sector = bio->bi_iter.bi_sector;
 		zone = find_zone(mddev->private, &sector);
 		tmp_dev = map_sector(mddev, zone, sector, &sector);
 		split->bi_bdev = tmp_dev->bdev;