Remove blkdev warning triggered by using md

As setting and clearing queue flags now requires that we hold a spinlock
on the queue, and as blk_queue_stack_limits is called without that lock,
get the lock inside blk_queue_stack_limits.

For blk_queue_stack_limits to be able to find the right lock, each md
personality needs to set q->queue_lock to point to the appropriate lock.
Those personalities which didn't previously use a spin_lock, us
q->__queue_lock. So always initialise that lock when allocated.

With this in place, setting/clearing of the QUEUE_FLAG_PLUGGED bit will no
longer cause warnings as it will be clear that the proper lock is held.

Thanks to Dan Williams for review and fixing the silly bugs.

Signed-off-by: NeilBrown <[e-mail]>
Cc: Dan Williams <[e-mail]>
Cc: Jens Axboe <[e-mail]>
Cc: Alistair John Strachan <[e-mail]>
Cc: Nick Piggin <[e-mail]>
Cc: "Rafael J. Wysocki" <[e-mail]>
Cc: Jacek Luczak <[e-mail]>
Cc: Prakash Punnoor <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

block/blk-core.c

···
 	kobject_init(&q->kobj, &blk_queue_ktype);
 
 	mutex_init(&q->sysfs_lock);
+	spin_lock_init(&q->__queue_lock);
 
 	return q;
 }
···
 	 * if caller didn't supply a lock, they get per-queue locking with
 	 * our embedded lock
 	 */
-	if (!lock) {
-		spin_lock_init(&q->__queue_lock);
+	if (!lock)
 		lock = &q->__queue_lock;
-	}
 
 	q->request_fn		= rfn;
 	q->prep_rq_fn		= NULL;

block/blk-settings.c

···
 	t->max_hw_segments = min(t->max_hw_segments, b->max_hw_segments);
 	t->max_segment_size = min(t->max_segment_size, b->max_segment_size);
 	t->hardsect_size = max(t->hardsect_size, b->hardsect_size);
-	if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags))
+	if (!t->queue_lock)
+		WARN_ON_ONCE(1);
+	else if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags)) {
+		unsigned long flags;
+		spin_lock_irqsave(t->queue_lock, flags);
 		queue_flag_clear(QUEUE_FLAG_CLUSTER, t);
+		spin_unlock_irqrestore(t->queue_lock, flags);
+	}
 }
 EXPORT_SYMBOL(blk_queue_stack_limits);
 

drivers/md/linear.c

···
 {
 	linear_conf_t *conf;
 
+	mddev->queue->queue_lock = &mddev->queue->__queue_lock;
 	conf = linear_conf(mddev, mddev->raid_disks);
 
 	if (!conf)

drivers/md/multipath.c

···
 	 * bookkeeping area. [whatever we allocate in multipath_run(),
 	 * should be freed in multipath_stop()]
 	 */
+	mddev->queue->queue_lock = &mddev->queue->__queue_lock;
 
 	conf = kzalloc(sizeof(multipath_conf_t), GFP_KERNEL);
 	mddev->private = conf;

drivers/md/raid0.c

···
 	       (mddev->chunk_size>>1)-1);
 	blk_queue_max_sectors(mddev->queue, mddev->chunk_size >> 9);
 	blk_queue_segment_boundary(mddev->queue, (mddev->chunk_size>>1) - 1);
+	mddev->queue->queue_lock = &mddev->queue->__queue_lock;
 
 	conf = kmalloc(sizeof (raid0_conf_t), GFP_KERNEL);
 	if (!conf)

drivers/md/raid1.c

···
 	if (!conf->r1bio_pool)
 		goto out_no_mem;
 
+	spin_lock_init(&conf->device_lock);
+	mddev->queue->queue_lock = &conf->device_lock;
+
 	rdev_for_each(rdev, tmp, mddev) {
 		disk_idx = rdev->raid_disk;
 		if (disk_idx >= mddev->raid_disks
···
 	}
 	conf->raid_disks = mddev->raid_disks;
 	conf->mddev = mddev;
-	spin_lock_init(&conf->device_lock);
 	INIT_LIST_HEAD(&conf->retry_list);
 
 	spin_lock_init(&conf->resync_lock);

drivers/md/raid10.c

···
 		goto out_free_conf;
 	}
 
+	spin_lock_init(&conf->device_lock);
+	mddev->queue->queue_lock = &conf->device_lock;
+
 	rdev_for_each(rdev, tmp, mddev) {
 		disk_idx = rdev->raid_disk;
 		if (disk_idx >= mddev->raid_disks
···
 
 		disk->head_position = 0;
 	}
-	spin_lock_init(&conf->device_lock);
 	INIT_LIST_HEAD(&conf->retry_list);
 
 	spin_lock_init(&conf->resync_lock);

drivers/md/raid5.c

···
 			goto abort;
 	}
 	spin_lock_init(&conf->device_lock);
+	mddev->queue->queue_lock = &conf->device_lock;
 	init_waitqueue_head(&conf->wait_for_stripe);
 	init_waitqueue_head(&conf->wait_for_overlap);
 	INIT_LIST_HEAD(&conf->handle_list);