commit a81157768a00e8cf8a7b43b5ea5cac931262374f
author Eric Work <work.eric@gmail.com> Mon May 18 23:26:23 2015 -0700
committer NeilBrown <neilb@suse.de> Thu May 21 09:14:25 2015 +1000
tree 824d88d9b79c668fb18594d4fe7bcbc414ee43bc
parent 487696957e3bd64ccffe62c0ac4ff7bf662785ab

md/raid0: fix restore to sector variable in raid0_make_request

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@suse.de>
Fixes: 47d68979cc96 ("md/raid0: fix bug with chunksize not a power of 2.")
Cc: stable@vger.kernel.org (any that received above backport)
URL: https://bugzilla.kernel.org/show_bug.cgi?id=98501

drivers/md/raid0.c

diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index 6a68ef5..efb654e 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -524,6 +524,9 @@
 			 ? (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);
@@ -531,7 +534,6 @@
 			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;