dm-buffered: add cond_resched

Add cond_resched to the "bio_for_each_segment" loop.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

---
 drivers/md/dm-buffered-target.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Index: linux-2.6/drivers/md/dm-buffered-target.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-buffered-target.c
+++ linux-2.6/drivers/md/dm-buffered-target.c
@@ -229,8 +229,10 @@ static void __process_bio(struct buffere
 				goto err;
 		}
 
-		bio_for_each_segment(bvec, bio, bio->bi_iter)
+		bio_for_each_segment(bvec, bio, bio->bi_iter) {
 			_io(bc, bio, &bvec);
+			cond_resched();
+		}
 
 		if (unlikely(bio->bi_status)) {
 			goto err;