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[PATCH 3.18 04/68] md:raid1: fix a dead loop when read from a WriteMostly disk

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

------------------

From: Wei Fang <fangwei1@huawei.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@huawei.com>
Signed-off-by: Shaohua Li <shli@fb.com>
Cc: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -563,7 +563,7 @@ 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 */
 						continue;
 					best_good_sectors = first_bad - this_sector;

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[PATCH 3.18 04/68] md:raid1: fix a dead loop when read from a WriteMostly disk Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-05 20:40 +0200

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