Btrfs: cleanup for unused ref cache stuff

As ref cache has been removed from btrfs, there is no user on
its lock and its check.

Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com>
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>

fs/btrfs/ctree.h

@@ -1376,9 +1376,6 @@ struct btrfs_fs_info {
 	struct rb_root defrag_inodes;
 	atomic_t defrag_running;
 
-	spinlock_t ref_cache_lock;
-	u64 total_ref_cache_size;
-
 	/*
 	 * these three are in extended format (availability of single
 	 * chunks is denoted by BTRFS_AVAIL_ALLOC_BIT_SINGLE bit, other

fs/btrfs/disk-io.c

@@ -2000,7 +2000,6 @@ int open_ctree(struct super_block *sb,
 	INIT_LIST_HEAD(&fs_info->caching_block_groups);
 	spin_lock_init(&fs_info->delalloc_lock);
 	spin_lock_init(&fs_info->trans_lock);
-	spin_lock_init(&fs_info->ref_cache_lock);
 	spin_lock_init(&fs_info->fs_roots_radix_lock);
 	spin_lock_init(&fs_info->delayed_iput_lock);
 	spin_lock_init(&fs_info->defrag_inodes_lock);
@@ -3214,10 +3213,6 @@ int close_ctree(struct btrfs_root *root)
 		printk(KERN_INFO "btrfs: at unmount delalloc count %llu\n",
 		       (unsigned long long)fs_info->delalloc_bytes);
 	}
-	if (fs_info->total_ref_cache_size) {
-		printk(KERN_INFO "btrfs: at umount reference cache size %llu\n",
-		       (unsigned long long)fs_info->total_ref_cache_size);
-	}
 
 	free_extent_buffer(fs_info->extent_root->node);
 	free_extent_buffer(fs_info->extent_root->commit_root);