+ char buf[sizeof zero_buf];
+ int fd;
+ size_t i, offset;
+
+ fd = open (device, O_RDWR);
+ if (fd == -1) {
+ reply_with_perror ("%s", device);
+ return -1;
+ }
+
+ for (i = 0; i < 32; ++i) {
+ offset = i * sizeof zero_buf;
+
+ /* Check if the block is already zero before overwriting it. */
+ if (pread (fd, buf, sizeof buf, offset) != sizeof buf) {
+ reply_with_perror ("pread: %s", device);
+ close (fd);
+ return -1;
+ }
+
+ if (!is_zero (buf, sizeof buf)) {
+ if (pwrite (fd, zero_buf, sizeof zero_buf, offset) != sizeof zero_buf) {
+ reply_with_perror ("pwrite: %s", device);
+ close (fd);
+ return -1;
+ }
+ }
+
+ notify_progress ((uint64_t) i, 32);
+ }
+
+ if (close (fd) == -1) {
+ reply_with_perror ("close: %s", device);
+ return -1;
+ }
+
+ return 0;
+}
+
+int
+do_zero_device (const char *device)
+{
+ int64_t ssize = do_blockdev_getsize64 (device);
+ if (ssize == -1)
+ return -1;
+ uint64_t size = (uint64_t) ssize;