Function do_punch_hole

syscall.c:1561–1596

Punch a hole at pos for len bytes. The current file position must be at pos and will be * changed to be at pos + len. */

/* Punch a hole at pos for len bytes. The current file position must be at pos and will be
 * changed to be at pos + len. */
int do_punch_hole(int fd, OFF_T pos, OFF_T len)
{
#ifdef HAVE_FALLOCATE
# ifdef HAVE_FALLOC_FL_PUNCH_HOLE
	if (fallocate(fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, pos, len) == 0) {
		if (do_lseek(fd, len, SEEK_CUR) != pos + len)
			return -1;
		return 0;
	}
# endif
# ifdef HAVE_FALLOC_FL_ZERO_RANGE
	if (fallocate(fd, FALLOC_FL_ZERO_RANGE, pos, len) == 0) {
		if (do_lseek(fd, len, SEEK_CUR) != pos + len)
			return -1;
		return 0;
	}
# endif
#else
	(void)pos;
#endif
	{
		char zeros[4096];
		memset(zeros, 0, sizeof zeros);
		while (len > 0) {
			int chunk = len > (int)sizeof zeros ? (int)sizeof zeros : len;
			int wrote = write(fd, zeros, chunk);
			if (wrote <= 0) {
				if (wrote < 0 && errno == EINTR)
					continue;
				return -1;
			}
			len -= wrote;
		}
	}
	return 0;
}

int do_open_nofollow(const char *pathname, int flags)
{