btrfs: change btrfs_free_reserved_bytes to return void

btrfs_free_reserved_bytes uses the variable "ret" for return value,
but it is not modified after initialzation. Further, I find that any of
the callers do not handle the return value, so it is safe to drop the
unneeded "ret" and return void. There are no callees that would need the
function to handle or pass the value either.
Signed-off-by: Nzhong jiang <zhongjiang@huawei.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/extent-tree.c

@@ -6422,11 +6422,10 @@ static int btrfs_add_reserved_bytes(struct btrfs_block_group_cache *cache,
  * reserve set to 0 in order to clear the reservation.
  */
 
-static int btrfs_free_reserved_bytes(struct btrfs_block_group_cache *cache,
-				     u64 num_bytes, int delalloc)
+static void btrfs_free_reserved_bytes(struct btrfs_block_group_cache *cache,
+				      u64 num_bytes, int delalloc)
 {
 	struct btrfs_space_info *space_info = cache->space_info;
-	int ret = 0;
 
 	spin_lock(&space_info->lock);
 	spin_lock(&cache->lock);
@@ -6439,7 +6438,6 @@ static int btrfs_free_reserved_bytes(struct btrfs_block_group_cache *cache,
 		cache->delalloc_bytes -= num_bytes;
 	spin_unlock(&cache->lock);
 	spin_unlock(&space_info->lock);
-	return ret;
 }
 void btrfs_prepare_extent_commit(struct btrfs_fs_info *fs_info)
 {