On Thu, Jun 18, 2020 at 12:06:26PM +0200, Karel Zak wrote:
> 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 ;-)
Sure, I can do that. The bad comment definitelly makes it more confusing
that it needed to be :)
if (!device_empty()) was the intention but then I still have to deal
with the error. I'll do the switch change.
-Lukas
>
> Karel
>
> --
> Karel Zak <kzak@xxxxxxxxxx>
> http://karelzak.blogspot.com
