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

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>

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 39fb21e048e642dd2bf6d6729a9e8c0cd61310a9..a7f2b9c9f8a06fa84aa5f46d6c44c5760894502b 100644 (file)
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -570,7 +570,7 @@ 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;