drbd: restart loop in drbd_make_request() [prepare for Linux-3.2]

With Linux-3.2 generic_make_request() will no longer loop over
the request function until it finally returns 0. Move this
loop into our drbd_make_request() function.
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

drivers/block/drbd/drbd_req.c

@@ -929,8 +929,8 @@ int __drbd_make_request(struct drbd_conf *mdev, struct bio *bio, unsigned long s
 	}
 
 	if (drbd_suspended(mdev)) {
-		/* If we got suspended, use the retry mechanism of
-		   generic_make_request() to restart processing of this
+		/* If we got suspended, use the retry mechanism in
+		   drbd_make_request() to restart processing of this
 		   bio. In the next call to drbd_make_request
 		   we sleep in inc_ap_bio() */
 		ret = 1;
@@ -1110,8 +1110,11 @@ int drbd_make_request(struct request_queue *q, struct bio *bio)
 	D_ASSERT(bio->bi_size > 0);
 	D_ASSERT(IS_ALIGNED(bio->bi_size, 512));
 
-	inc_ap_bio(mdev);
-	return __drbd_make_request(mdev, bio, start_time);
+	do {
+		inc_ap_bio(mdev);
+	} while (__drbd_make_request(mdev, bio, start_time));
+
+	return 0;
 }
 
 /* This is called by bio_add_page().