Function punch_hole

src/copy-file-data.c:44–58

Attempt to punch a hole to avoid any permanent speculative preallocation on file systems such as XFS. Return values as per fallocate(2) except ENOSYS etc. are ignored. */

   speculative preallocation on file systems such as XFS.
   Return values as per fallocate(2) except ENOSYS etc. are ignored.  */
static int
punch_hole (int fd, off_t offset, off_t length)
{
  int ret = 0;
/* +0 is to work around older <linux/fs.h> defining HAVE_FALLOCATE to empty.  */
#if HAVE_FALLOCATE + 0
# if defined FALLOC_FL_PUNCH_HOLE && defined FALLOC_FL_KEEP_SIZE
  ret = fallocate (fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
                   offset, length);
  if (ret < 0 && (is_ENOTSUP (errno) || errno == ENOSYS))
    ret = 0;
# endif
#endif
  return ret;
}

/* Create a hole at the end of the file with descriptor FD and name NAME.
   The hole is of size SIZE.  Assume FD is already at file end,