[PATCH] Fix get_request nastiness

get_request is now expected to be holding on to queue_lock, with interrupts
disabled, when it returns NULL; but one path forgot that, causing all kinds
of nastiness under swap load - badness backtraces, strange failures, BUGs.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/block/ll_rw_blk.c

@@ -1917,10 +1917,9 @@ static struct request *get_request(request_queue_t *q, int rw, struct bio *bio,
 	 * limit of requests, otherwise we could have thousands of requests
 	 * allocated with any setting of ->nr_requests
 	 */
-	if (rl->count[rw] >= (3 * q->nr_requests / 2)) {
-		spin_unlock_irq(q->queue_lock);
+	if (rl->count[rw] >= (3 * q->nr_requests / 2))
 		goto out;
-	}
+
 	rl->count[rw]++;
 	rl->starved[rw] = 0;
 	if (rl->count[rw] >= queue_congestion_on_threshold(q))