int ext4_group_add_blocks(handle_t *handle, struct super_block *sb,
			 ext4_fsblk_t block, unsigned long count)
{
	struct buffer_head *bitmap_bh = NULL;
	struct buffer_head *gd_bh;
	ext4_group_t block_group;
	ext4_grpblk_t bit;
	unsigned int i;
	struct ext4_group_desc *desc;
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	struct ext4_buddy e4b;
	int err = 0, ret, free_clusters_count;
	ext4_grpblk_t clusters_freed;
	ext4_fsblk_t first_cluster = EXT4_B2C(sbi, block);
	ext4_fsblk_t last_cluster = EXT4_B2C(sbi, block + count - 1);
	unsigned long cluster_count = last_cluster - first_cluster + 1;

	ext4_debug("Adding block(s) %llu-%llu\n", block, block + count - 1);

	if (count == 0)
		return 0;

	ext4_get_group_no_and_offset(sb, block, &block_group, &bit);
	/*
	 * Check to see if we are freeing blocks across a group
	 * boundary.
	 */
	if (bit + cluster_count > EXT4_CLUSTERS_PER_GROUP(sb)) {
		ext4_warning(sb, "too many blocks added to group %u",
			     block_group);
		err = -EINVAL;
		goto error_return;
	}

	bitmap_bh = ext4_read_block_bitmap(sb, block_group);
	if (IS_ERR(bitmap_bh)) {
		err = PTR_ERR(bitmap_bh);
		bitmap_bh = NULL;
		goto error_return;
	}

	desc = ext4_get_group_desc(sb, block_group, &gd_bh);
	if (!desc) {
		err = -EIO;
		goto error_return;
	}

	if (in_range(ext4_block_bitmap(sb, desc), block, count) ||
	    in_range(ext4_inode_bitmap(sb, desc), block, count) ||
	    in_range(block, ext4_inode_table(sb, desc), sbi->s_itb_per_group) ||
	    in_range(block + count - 1, ext4_inode_table(sb, desc),
		     sbi->s_itb_per_group)) {
		ext4_error(sb, "Adding blocks in system zones - "
			   "Block = %llu, count = %lu",
			   block, count);
		err = -EINVAL;
		goto error_return;
	}

	BUFFER_TRACE(bitmap_bh, "getting write access");
	err = ext4_journal_get_write_access(handle, bitmap_bh);
	if (err)
		goto error_return;

	/*
	 * We are about to modify some metadata.  Call the journal APIs
	 * to unshare ->b_data if a currently-committing transaction is
	 * using it
	 */
	BUFFER_TRACE(gd_bh, "get_write_access");
	err = ext4_journal_get_write_access(handle, gd_bh);
	if (err)
		goto error_return;

	for (i = 0, clusters_freed = 0; i < cluster_count; i++) {
		BUFFER_TRACE(bitmap_bh, "clear bit");
		if (!mb_test_bit(bit + i, bitmap_bh->b_data)) {
			ext4_error(sb, "bit already cleared for block %llu",
				   (ext4_fsblk_t)(block + i));
			BUFFER_TRACE(bitmap_bh, "bit already cleared");
		} else {
			clusters_freed++;
		}
	}

	err = ext4_mb_load_buddy(sb, block_group, &e4b);
	if (err)
		goto error_return;

	/*
	 * need to update group_info->bb_free and bitmap
	 * with group lock held. generate_buddy look at
	 * them with group lock_held
	 */
	ext4_lock_group(sb, block_group);
	mb_clear_bits(bitmap_bh->b_data, bit, cluster_count);
	mb_free_blocks(NULL, &e4b, bit, cluster_count);
	free_clusters_count = clusters_freed +
		ext4_free_group_clusters(sb, desc);
	ext4_free_group_clusters_set(sb, desc, free_clusters_count);
	ext4_block_bitmap_csum_set(sb, block_group, desc, bitmap_bh);
	ext4_group_desc_csum_set(sb, block_group, desc);
	ext4_unlock_group(sb, block_group);
	percpu_counter_add(&sbi->s_freeclusters_counter,
			   clusters_freed);

	if (sbi->s_log_groups_per_flex) {
		ext4_group_t flex_group = ext4_flex_group(sbi, block_group);
		atomic64_add(clusters_freed,
			     &sbi->s_flex_groups[flex_group].free_clusters);
	}

	ext4_mb_unload_buddy(&e4b);

	/* We dirtied the bitmap block */
	BUFFER_TRACE(bitmap_bh, "dirtied bitmap block");
	err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);

	/* And the group descriptor block */
	BUFFER_TRACE(gd_bh, "dirtied group descriptor block");
	ret = ext4_handle_dirty_metadata(handle, NULL, gd_bh);
	if (!err)
		err = ret;

error_return:
	brelse(bitmap_bh);
	ext4_std_error(sb, err);
	return err;
}