[3.19.y-ckt stable] Patch "md/raid0: fix restore to sector variable in raid0_make_request" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    md/raid0: fix restore to sector variable in raid0_make_request

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.8-ckt1.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From f09ab4d2936f7c74bb5b89b24a00f182e48e6811 Mon Sep 17 00:00:00 2001
From: Eric Work <work.eric at gmail.com>
Date: Mon, 18 May 2015 23:26:23 -0700
Subject: md/raid0: fix restore to sector variable in raid0_make_request

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
Signed-off-by: Kamal Mostafa <kamal 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 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