1 files changed, 30 insertions, 7 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index f3cc5d99fe8d..345e94c10c65 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -125,6 +125,10 @@ struct mapped_device {
         unsigned long flags;
 
         struct request_queue *queue;
+        unsigned type;
+        /* Protect type against concurrent access. */
+        struct mutex type_lock;
+
         struct gendisk *disk;
         char name[16];
 
@@ -1877,8 +1881,10 @@ static struct mapped_device *alloc_dev(int minor)
         if (r < 0)
                 goto bad_minor;
 
+        md->type = DM_TYPE_NONE;
         init_rwsem(&md->io_lock);
         mutex_init(&md->suspend_lock);
+        mutex_init(&md->type_lock);
         spin_lock_init(&md->deferred_lock);
         spin_lock_init(&md->barrier_error_lock);
         rwlock_init(&md->map_lock);
@@ -2130,6 +2136,30 @@ int dm_create(int minor, struct mapped_device **result)
         return 0;
 }
 
+/*
+ * Functions to manage md->type.
+ * All are required to hold md->type_lock.
+ */
+void dm_lock_md_type(struct mapped_device *md)
+{
+        mutex_lock(&md->type_lock);
+}
+
+void dm_unlock_md_type(struct mapped_device *md)
+{
+        mutex_unlock(&md->type_lock);
+}
+
+void dm_set_md_type(struct mapped_device *md, unsigned type)
+{
+        md->type = type;
+}
+
+unsigned dm_get_md_type(struct mapped_device *md)
+{
+        return md->type;
+}
+
 static struct mapped_device *dm_find_md(dev_t dev)
 {
         struct mapped_device *md;
@@ -2440,13 +2470,6 @@ struct dm_table *dm_swap_table(struct mapped_device *md, struct dm_table *table)
                 goto out;
         }
 
-        /* cannot change the device type, once a table is bound */
-        if (md->map &&
-            (dm_table_get_type(md->map) != dm_table_get_type(table))) {
-                DMWARN("can't change the device type after a table is bound");
-                goto out;
-        }
-
         map = __bind(md, table, &limits);
 
 out: