btrfs: block-group: refactor how we delete one block group item

When deleting a block group item, it's pretty straight forward, just
delete the item pointed by the key.  However it will not be that
straight-forward for incoming skinny block group item.

So refactor the block group item deletion into a new function,
remove_block_group_item(), also to make the already lengthy
btrfs_remove_block_group() a little shorter.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/block-group.c

@@ -865,11 +865,34 @@ static void clear_incompat_bg_bits(struct btrfs_fs_info *fs_info, u64 flags)
 	}
 }
 
+static int remove_block_group_item(struct btrfs_trans_handle *trans,
+				   struct btrfs_path *path,
+				   struct btrfs_block_group *block_group)
+{
+	struct btrfs_fs_info *fs_info = trans->fs_info;
+	struct btrfs_root *root;
+	struct btrfs_key key;
+	int ret;
+
+	root = fs_info->extent_root;
+	key.objectid = block_group->start;
+	key.type = BTRFS_BLOCK_GROUP_ITEM_KEY;
+	key.offset = block_group->length;
+
+	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
+	if (ret > 0)
+		ret = -ENOENT;
+	if (ret < 0)
+		return ret;
+
+	ret = btrfs_del_item(trans, root, path);
+	return ret;
+}
+
 int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
 			     u64 group_start, struct extent_map *em)
 {
 	struct btrfs_fs_info *fs_info = trans->fs_info;
-	struct btrfs_root *root = fs_info->extent_root;
 	struct btrfs_path *path;
 	struct btrfs_block_group *block_group;
 	struct btrfs_free_cluster *cluster;
@@ -1067,10 +1090,6 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
 
 	spin_unlock(&block_group->space_info->lock);
 
-	key.objectid = block_group->start;
-	key.type = BTRFS_BLOCK_GROUP_ITEM_KEY;
-	key.offset = block_group->length;
-
 	mutex_lock(&fs_info->chunk_mutex);
 	spin_lock(&block_group->lock);
 	block_group->removed = 1;
@@ -1112,16 +1131,10 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
 	/* Once for the block groups rbtree */
 	btrfs_put_block_group(block_group);
 
-	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
-	if (ret > 0)
-		ret = -EIO;
+	ret = remove_block_group_item(trans, path, block_group);
 	if (ret < 0)
 		goto out;
 
-	ret = btrfs_del_item(trans, root, path);
-	if (ret)
-		goto out;
-
 	if (remove_em) {
 		struct extent_map_tree *em_tree;