dm: disable interrupt when taking map_lock

This patch disables interrupt when taking map_lock to avoid
lockdep warnings in request-based dm.

request-based dm takes map_lock after taking queue_lock with
disabling interrupt:
spin_lock_irqsave(queue_lock)
q->request_fn() == dm_request_fn()
=> dm_get_table()
=> read_lock(map_lock)
while queue_lock could be (but isn't) taken in interrupt context.

Signed-off-by: Kiyoshi Ueda <[e-mail]>
Signed-off-by: Jun'ichi Nomura <[e-mail]>
Acked-by: Christof Schmitt <[e-mail]>
Acked-by: Hannes Reinecke <[e-mail]>
Signed-off-by: Alasdair G Kergon <[e-mail]>

drivers/md/dm.c

···
 struct dm_table *dm_get_table(struct mapped_device *md)
 {
 	struct dm_table *t;
+	unsigned long flags;
 
-	read_lock(&md->map_lock);
+	read_lock_irqsave(&md->map_lock, flags);
 	t = md->map;
 	if (t)
 		dm_table_get(t);
-	read_unlock(&md->map_lock);
+	read_unlock_irqrestore(&md->map_lock, flags);
 
 	return t;
 }
···
 {
 	struct request_queue *q = md->queue;
 	sector_t size;
+	unsigned long flags;
 
 	size = dm_table_get_size(t);
 
···
 
 	__bind_mempools(md, t);
 
-	write_lock(&md->map_lock);
+	write_lock_irqsave(&md->map_lock, flags);
 	md->map = t;
 	dm_table_set_restrictions(t, q, limits);
-	write_unlock(&md->map_lock);
+	write_unlock_irqrestore(&md->map_lock, flags);
 
 	return 0;
 }
···
 static void __unbind(struct mapped_device *md)
 {
 	struct dm_table *map = md->map;
+	unsigned long flags;
 
 	if (!map)
 		return;
 
 	dm_table_event_callback(map, NULL, NULL);
-	write_lock(&md->map_lock);
+	write_lock_irqsave(&md->map_lock, flags);
 	md->map = NULL;
-	write_unlock(&md->map_lock);
+	write_unlock_irqrestore(&md->map_lock, flags);
 	dm_table_destroy(map);
 }