[PATCH 4.4 08/43] md:raid1: fix a dead loop when read from a WriteMostly disk

From: Greg Kroah-Hartman
Date: Mon May 01 2017 - 18:02:42 EST

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


From: Wei Fang <fangwei1@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Shaohua Li <shli@xxxxxx>
Cc: Julia Lawall <julia.lawall@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/md/raid1.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -570,7 +570,7 @@ static int read_balance(struct r1conf *c
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 */
best_good_sectors = first_bad - this_sector;