static int ext4_valid_extent(struct inode *inode, struct ext4_extent *ext)
{
	ext4_fsblk_t block = ext4_ext_pblock(ext);
	int len = ext4_ext_get_actual_len(ext);
	ext4_lblk_t lblock = le32_to_cpu(ext->ee_block);

	/*
	 * We allow neither:
	 *  - zero length
	 *  - overflow/wrap-around
	 */
	if (lblock + len <= lblock)
		return 0;
	return ext4_inode_block_valid(inode, block, len);
}
static int ext4_valid_extent(struct inode *inode, struct ext4_extent *ext)
{
	ext4_fsblk_t block = ext4_ext_pblock(ext);
	int len = ext4_ext_get_actual_len(ext);
	ext4_lblk_t lblock = le32_to_cpu(ext->ee_block);

	 
	if (lblock + len <= lblock)
		return 0;
	return ext4_inode_block_valid(inode, block, len);
}