block: add missing blk_queue_dead() checks

commit 8ba61435 upstream.

blk_insert_cloned_request(), blk_execute_rq_nowait() and
blk_flush_plug_list() either didn't check whether the queue was dead
or did it without holding queue_lock.  Update them so that dead state
is checked while holding queue_lock.

AFAICS, this plugs all holes (requeue doesn't matter as the request is
transitioning atomically from in_flight to queued).
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
[bwh: Backported to 2.6.32:
 - Drop inapplicable changes to queue_unplugged() and
   blk_flush_plug_list()
 - We don't have blk_queue_dead() so open-code it
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Willy Tarreau <w@1wt.eu>

block/blk-core.c

@@ -1651,6 +1651,10 @@ int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
 #endif
 
 	spin_lock_irqsave(q->queue_lock, flags);
+	if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) {
+		spin_unlock_irqrestore(q->queue_lock, flags);
+		return -ENODEV;
+	}
 
 	/*
 	 * Submitting request must be dequeued before calling this function

block/blk-exec.c

@@ -50,7 +50,11 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk,
 {
 	int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
 
+	WARN_ON(irqs_disabled());
+	spin_lock_irq(q->queue_lock);
+
 	if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) {
+		spin_unlock_irq(q->queue_lock);
 		rq->errors = -ENXIO;
 		if (rq->end_io)
 			rq->end_io(rq, rq->errors);
@@ -59,8 +63,6 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk,
 
 	rq->rq_disk = bd_disk;
 	rq->end_io = done;
-	WARN_ON(irqs_disabled());
-	spin_lock_irq(q->queue_lock);
 	__elv_add_request(q, rq, where, 1);
 	__generic_unplug_device(q);
 	/* the queue is stopped so it won't be plugged+unplugged */