[PATCH] block cleanups: Fix iosched module refcount leak

If the requested I/O scheduler is already in place, elevator_switch simply
leaves the queue alone, and returns.  However, it forgets to call
elevator_put, so

'echo [current_sched] > /sys/block/[dev]/queue/scheduler'

will leak a reference, causing the current_sched module to be permanently
pinned in memory.

Signed-off-by: Nate Diller <nate@namesys.com>
Acked-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/block/elevator.c

@@ -753,8 +753,10 @@ ssize_t elv_iosched_store(request_queue_t *q, const char *name, size_t count)
 		return -EINVAL;
 	}
 
-	if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name))
+	if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) {
+		elevator_put(e);
 		return count;
+	}
 
 	elevator_switch(q, e);
 	return count;