linux-kernel - [PATCH 3.19.y-ckt 92/92] md/raid0: fix restore to sector variable in raid0_make

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Message-Id: <1432654896-28478-93-git-send-email-kamal@canonical.com>
Date:	Tue, 26 May 2015 08:41:36 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	NeilBrown <neilb@...e.de>, Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 92/92] md/raid0: fix restore to sector variable in raid0_make_request

3.19.8-ckt1 -stable review patch.  If anyone has any objections, please let me know.

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

From: Eric Work <work.eric@...il.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@...e.de>
Fixes: 47d68979cc96 ("md/raid0: fix bug with chunksize not a power of 2.")
URL: https://bugzilla.kernel.org/show_bug.cgi?id=98501
Signed-off-by: Kamal Mostafa <kamal@...onical.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 d5c12e5..b974ff2 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -530,6 +530,9 @@ 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);
@@ -537,7 +540,6 @@ 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;
-- 
1.9.1

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