btrfs: drop uuid_mutex in btrfs_destroy_dev_replace_tgtdev

Delete the uuid_mutex lock here as this thread accesses the
btrfs_fs_devices::devices only (counters or called functions do a list
traversal). And the device_list_mutex lock is already taken.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/volumes.c

@@ -2152,7 +2152,6 @@ void btrfs_rm_dev_replace_free_srcdev(struct btrfs_fs_info *fs_info,
 void btrfs_destroy_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
 				      struct btrfs_device *tgtdev)
 {
-	mutex_lock(&uuid_mutex);
 	WARN_ON(!tgtdev);
 	mutex_lock(&fs_info->fs_devices->device_list_mutex);
 
@@ -2168,7 +2167,6 @@ void btrfs_destroy_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
 	list_del_rcu(&tgtdev->dev_list);
 
 	mutex_unlock(&fs_info->fs_devices->device_list_mutex);
-	mutex_unlock(&uuid_mutex);
 
 	/*
 	 * The update_dev_time() with in btrfs_scratch_superblocks()