Btrfs: Remove unused btrfs_block_group_free_space()

We've already recorded the value in block_group->frees_space.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>

fs/btrfs/free-space-cache.c

@@ -1685,21 +1685,6 @@ void btrfs_dump_free_space(struct btrfs_block_group_cache *block_group,
 	       "\n", count);
 }
 
-u64 btrfs_block_group_free_space(struct btrfs_block_group_cache *block_group)
-{
-	struct btrfs_free_space *info;
-	struct rb_node *n;
-	u64 ret = 0;
-
-	for (n = rb_first(&block_group->free_space_offset); n;
-	     n = rb_next(n)) {
-		info = rb_entry(n, struct btrfs_free_space, offset_index);
-		ret += info->bytes;
-	}
-
-	return ret;
-}
-
 /*
  * for a given cluster, put all of its extents back into the free
  * space cache.  If the block group passed doesn't match the block group

fs/btrfs/free-space-cache.h

@@ -55,7 +55,6 @@ u64 btrfs_find_space_for_alloc(struct btrfs_block_group_cache *block_group,
 			       u64 offset, u64 bytes, u64 empty_size);
 void btrfs_dump_free_space(struct btrfs_block_group_cache *block_group,
 			   u64 bytes);
-u64 btrfs_block_group_free_space(struct btrfs_block_group_cache *block_group);
 int btrfs_find_space_cluster(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *root,
 			     struct btrfs_block_group_cache *block_group,