[PATCH 3.19 044/177] md/raid0: fix bug with chunksize not a power of 2.

[Greg Kroah-Hartman]

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

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

From: NeilBrown <neilb@xxxxxxx>

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@xxxxxxxxx>
Reported-by: Dave Chinner <david@xxxxxxxxxxxxx>
Fixes: 20d0189b1012a37d2533a87fb451f7852f2418d1
Signed-off-by: NeilBrown <neilb@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/md/raid0.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -319,7 +319,7 @@ static struct strip_zone *find_zone(stru
 
 /*
  * 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)
@@ -537,6 +537,7 @@ static void raid0_make_request(struct md
 			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;


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