static int ext4_split_extent_at(handle_t *handle,
			     struct inode *inode,
			     struct ext4_ext_path **ppath,
			     ext4_lblk_t split,
			     int split_flag,
			     int flags)
{
	struct ext4_ext_path *path = *ppath;
	ext4_fsblk_t newblock;
	ext4_lblk_t ee_block;
	struct ext4_extent *ex, newex, orig_ex, zero_ex;
	struct ext4_extent *ex2 = NULL;
	unsigned int ee_len, depth;
	int err = 0;

	BUG_ON((split_flag & (EXT4_EXT_DATA_VALID1 | EXT4_EXT_DATA_VALID2)) ==
	       (EXT4_EXT_DATA_VALID1 | EXT4_EXT_DATA_VALID2));

	ext_debug("ext4_split_extents_at: inode %lu, logical"
		"block %llu\n", inode->i_ino, (unsigned long long)split);

	ext4_ext_show_leaf(inode, path);

	depth = ext_depth(inode);
	ex = path[depth].p_ext;
	ee_block = le32_to_cpu(ex->ee_block);
	ee_len = ext4_ext_get_actual_len(ex);
	newblock = split - ee_block + ext4_ext_pblock(ex);

	BUG_ON(split < ee_block || split >= (ee_block + ee_len));
	BUG_ON(!ext4_ext_is_unwritten(ex) &&
	       split_flag & (EXT4_EXT_MAY_ZEROOUT |
			     EXT4_EXT_MARK_UNWRIT1 |
			     EXT4_EXT_MARK_UNWRIT2));

	err = ext4_ext_get_access(handle, inode, path + depth);
	if (err)
		goto out;

	if (split == ee_block) {
		/*
		 * case b: block @split is the block that the extent begins with
		 * then we just change the state of the extent, and splitting
		 * is not needed.
		 */
		if (split_flag & EXT4_EXT_MARK_UNWRIT2)
			ext4_ext_mark_unwritten(ex);
		else
			ext4_ext_mark_initialized(ex);

		if (!(flags & EXT4_GET_BLOCKS_PRE_IO))
			ext4_ext_try_to_merge(handle, inode, path, ex);

		err = ext4_ext_dirty(handle, inode, path + path->p_depth);
		goto out;
	}

	/* case a */
	memcpy(&orig_ex, ex, sizeof(orig_ex));
	ex->ee_len = cpu_to_le16(split - ee_block);
	if (split_flag & EXT4_EXT_MARK_UNWRIT1)
		ext4_ext_mark_unwritten(ex);

	/*
	 * path may lead to new leaf, not to original leaf any more
	 * after ext4_ext_insert_extent() returns,
	 */
	err = ext4_ext_dirty(handle, inode, path + depth);
	if (err)
		goto fix_extent_len;

	ex2 = &newex;
	ex2->ee_block = cpu_to_le32(split);
	ex2->ee_len   = cpu_to_le16(ee_len - (split - ee_block));
	ext4_ext_store_pblock(ex2, newblock);
	if (split_flag & EXT4_EXT_MARK_UNWRIT2)
		ext4_ext_mark_unwritten(ex2);

	err = ext4_ext_insert_extent(handle, inode, ppath, &newex, flags);
	if (err == -ENOSPC && (EXT4_EXT_MAY_ZEROOUT & split_flag)) {
		if (split_flag & (EXT4_EXT_DATA_VALID1|EXT4_EXT_DATA_VALID2)) {
			if (split_flag & EXT4_EXT_DATA_VALID1) {
				err = ext4_ext_zeroout(inode, ex2);
				zero_ex.ee_block = ex2->ee_block;
				zero_ex.ee_len = cpu_to_le16(
						ext4_ext_get_actual_len(ex2));
				ext4_ext_store_pblock(&zero_ex,
						      ext4_ext_pblock(ex2));
			} else {
				err = ext4_ext_zeroout(inode, ex);
				zero_ex.ee_block = ex->ee_block;
				zero_ex.ee_len = cpu_to_le16(
						ext4_ext_get_actual_len(ex));
				ext4_ext_store_pblock(&zero_ex,
						      ext4_ext_pblock(ex));
			}
		} else {
			err = ext4_ext_zeroout(inode, &orig_ex);
			zero_ex.ee_block = orig_ex.ee_block;
			zero_ex.ee_len = cpu_to_le16(
						ext4_ext_get_actual_len(&orig_ex));
			ext4_ext_store_pblock(&zero_ex,
					      ext4_ext_pblock(&orig_ex));
		}

		if (err)
			goto fix_extent_len;
		/* update the extent length and mark as initialized */
		ex->ee_len = cpu_to_le16(ee_len);
		ext4_ext_try_to_merge(handle, inode, path, ex);
		err = ext4_ext_dirty(handle, inode, path + path->p_depth);
		if (err)
			goto fix_extent_len;

		/* update extent status tree */
		err = ext4_zeroout_es(inode, &zero_ex);

		goto out;
	} else if (err)
		goto fix_extent_len;

out:
	ext4_ext_show_leaf(inode, path);
	return err;

fix_extent_len:
	ex->ee_len = orig_ex.ee_len;
	ext4_ext_dirty(handle, inode, path + path->p_depth);
	return err;
}