long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
{
  struct inode *inode = file_inode(file);
  loff_t new_size = 0;
  unsigned int max_blocks;
  int ret = 0;
  int flags;
  ext4_lblk_t lblk;
  unsigned int blkbits = inode->i_blkbits;

  /*
   * Encrypted inodes can't handle collapse range or insert
   * range since we would need to re-encrypt blocks with a
   * different IV or XTS tweak (which are based on the logical
   * block number).
   *
   * XXX It's not clear why zero range isn't working, but we'll
   * leave it disabled for encrypted inodes for now.  This is a
   * bug we should fix....
   */
  if (ext4_encrypted_inode(inode) &&
      (mode & (FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_INSERT_RANGE |
         FALLOC_FL_ZERO_RANGE)))
    return -EOPNOTSUPP;

  /* Return error if mode is not supported */
  if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |
         FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE |
         FALLOC_FL_INSERT_RANGE))
    return -EOPNOTSUPP;