[PATCH 3.16.y-ckt 130/130] md/raid0: fix restore to sector variable in raid0_make_request

[Luis Henriques]

3.16.7-ckt12 -stable review patch.  If anyone has any objections, please let me know.

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

From: Eric Work <work.eric at gmail.com>

commit a81157768a00e8cf8a7b43b5ea5cac931262374f upstream.

The variable "sector" in "raid0_make_request()" was improperly updated
by a call to "sector_div()" which modifies its first argument in place.
Commit 47d68979cc968535cb87f3e5f2e6a3533ea48fbd restored this variable
after the call for later re-use.  Unfortunetly the restore was done after
the referenced variable "bio" was advanced.  This lead to the original
value and the restored value being different.  Here we move this line to
the proper place.

One observed side effect of this bug was discarding a file though
unlinking would cause an unrelated file's contents to be discarded.

Signed-off-by: NeilBrown <neilb at suse.de>
Fixes: 47d68979cc96 ("md/raid0: fix bug with chunksize not a power of 2.")
URL: https://bugzilla.kernel.org/show_bug.cgi?id=98501
Cc: Philip Müller <philm at manjaro.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/md/raid0.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index 683e685ed697..9afd00b45f83 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -531,6 +531,9 @@ static void raid0_make_request(struct mddev *mddev, struct bio *bio)
 			 ? (sector & (chunk_sects-1))
 			 : sector_div(sector, chunk_sects));
 
+		/* Restore due to sector_div */
+		sector = bio->bi_iter.bi_sector;
+
 		if (sectors < bio_sectors(bio)) {
 			split = bio_split(bio, sectors, GFP_NOIO, fs_bio_set);
 			bio_chain(split, bio);
@@ -538,7 +541,6 @@ 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;