On Thu, Jun 18, 2020 at 11:29:16AM +0200, Lukas Czerner wrote:
> With this commit blkdiscard will check for existing signatures on the
> device and refuse to continue if any are found unless the operation is
> forced with the -f option.
Good idea.
> +/*
> + * Check existing signature on the open fd
> + * Returns 0 if no signature was found
> + * 1 if a signature was found
this is not true, 0 means detected, 1 not found
> + * <0 on error
> + */
> +static int device_empty(int fd, char *path)
This is difficult for to read, at first glance it seems according
to function name that 1 means "yes, it's empty".
Maybe rename it to probe_device().
> +{
> + const char *type;
> + blkid_probe pr = NULL;
> + int ret = -1;
> +
> + pr = blkid_new_probe();
> + if (!pr || blkid_probe_set_device(pr, fd, 0, 0))
> + return ret;
> +
> + blkid_probe_enable_superblocks(pr, TRUE);
> + blkid_probe_enable_partitions(pr, TRUE);
> +
> + ret = blkid_do_fullprobe(pr);
> + if (ret)
> + return ret;
yes, blkid_do_fullprobe() returns: 0 on success, 1 if nothing is detected or -1 on case of error.
> +
> + if (!blkid_probe_lookup_value(pr, "TYPE", &type, NULL)) {
> + warnx("%s contains existing file system (%s).",path ,type);
> + } else if (!blkid_probe_lookup_value(pr, "PTTYPE", &type, NULL)) {
> + warnx("%s contains existing partition (%s).",path ,type);
> + } else {
> + warnx("%s contains existing signature.", path);
> + }
> +
> + blkid_free_probe(pr);
> + return ret;
This is always 0.
> +}
>
> int main(int argc, char **argv)
> {
> char *path;
> - int c, fd, verbose = 0, secsize, force = 0;
> + int c, fd, ret, verbose = 0, secsize, force = 0;
> uint64_t end, blksize, step, range[2], stats[2];
> struct stat sb;
> struct timeval now, last;
> @@ -184,7 +219,7 @@ int main(int argc, char **argv)
> errtryhelp(EXIT_FAILURE);
> }
>
> - fd = open(path, O_WRONLY | (force ? 0 : O_EXCL));
> + fd = open(path, O_RDWR | (force ? 0 : O_EXCL));
> if (fd < 0)
> err(EXIT_FAILURE, _("cannot open %s"), path);
>
> @@ -217,6 +252,21 @@ int main(int argc, char **argv)
> errx(EXIT_FAILURE, _("%s: length %" PRIu64 " is not aligned "
> "to sector size %i"), path, range[1], secsize);
>
> + /* Check for existing signatures on the device */
> + if ((ret = device_empty(fd, path)) == 0) {
What about:
switch (probe_device(fd, path)) {
case 0: /* signature detected */
> + /*
> + * Only require force in interactive mode to avoid
> + * breaking existing scripts
> + */
> + if (!force && isatty(STDIN_FILENO)) {
> + errx(EXIT_FAILURE,
> + _("This is destructive operation, data will " \
> + "be lost! Use the -f option to override."));
> + }
> + warnx(_("Operation forced, data will be lost!"));
break;
case 1: /* no signature */
break;
default: /* error */
> + err(EXIT_FAILURE, _("failed to probe the device"));
break;
}
I think it's more readable ;-)
Karel
--
Karel Zak <kzak@xxxxxxxxxx>
http://karelzak.blogspot.com
