From: Wei Fang <fangwei1@huawei.com>
Date: Mon, 21 Mar 2016 11:18:32 +0000 (+0800)
Subject: md:raid1: fix a dead loop when read from a WriteMostly disk
X-Git-Tag: v3.12.74~10
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=204c56d845fcec43176160f831b86444d745cf67;p=thirdparty%2Fkernel%2Fstable.git

md:raid1: fix a dead loop when read from a WriteMostly disk

commit 816b0acf3deb6d6be5d0519b286fdd4bafade905 upstream.

If first_bad == this_sector when we get the WriteMostly disk
in read_balance(), valid disk will be returned with zero
max_sectors. It'll lead to a dead loop in make_request(), and
OOM will happen because of endless allocation of struct bio.

Since we can't get data from this disk in this case, so
continue for another disk.

Signed-off-by: Wei Fang <fangwei1@huawei.com>
Signed-off-by: Shaohua Li <shli@fb.com>
Cc: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 479828ad20213..e5f8fd19e47d4 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -560,7 +560,7 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
 			if (best_dist_disk < 0) {
 				if (is_badblock(rdev, this_sector, sectors,
 						&first_bad, &bad_sectors)) {
-					if (first_bad < this_sector)
+					if (first_bad <= this_sector)
 						/* Cannot use this */
 						continue;
 					best_good_sectors = first_bad - this_sector;