linux-kernel - [PATCH 3.10 019/268] md:raid1: fix a dead loop when read from a WriteMostly disk

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Message-Id: <1497897167-14556-20-git-send-email-w@1wt.eu>
Date:   Mon, 19 Jun 2017 20:28:38 +0200
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     Wei Fang <fangwei1@...wei.com>, Shaohua Li <shli@...com>,
        Julia Lawall <julia.lawall@...6.fr>,
        Jiri Slaby <jslaby@...e.cz>, Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 019/268] md:raid1: fix a dead loop when read from a WriteMostly disk

From: Wei Fang <fangwei1@...wei.com>

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@...wei.com>
Signed-off-by: Shaohua Li <shli@...com>
Cc: Julia Lawall <julia.lawall@...6.fr>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
Signed-off-by: Willy Tarreau <w@....eu>
---
 drivers/md/raid1.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 63d42ae..a8315aa 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;
-- 
2.8.0.rc2.1.gbe9624a