watchdogd stat location

[Warner Losh]

On Fri, Sep 27, 2019 at 2:30 PM mike tancsa <mike at sentex.net> wrote:

> On 9/27/2019 3:53 PM, Warner Losh wrote:
> > >
> >
> >     I am all for that too. Just something other than /etc or /var
> >     which are
> >     often mounted on ramdisk.
> >
> >
> > I think that / is too special to cause disk IO to ever happen. Other
> > dirs will sometimes not be in the cache.... The notion here, perhaps
> > bogus, is that we want to check the root FS is sane. The stat(2) is a
> > cheap way to do this that will eventually fail if / goes wonky enough.
> > It's weak.
> >
> >
> Would something like this buy any extra sanity ? or not worth it. I
> guess fancier checks belong in a passed program
>
>
> # diff -u watchdogd.c.orig watchdogd.c
> --- watchdogd.c.orig    2019-09-27 16:27:14.456973000 -0400
> +++ watchdogd.c 2019-09-27 16:27:18.904885000 -0400
> @@ -364,9 +364,23 @@
>
>                 if (test_cmd != NULL)
>                         failed = system(test_cmd);
> -               else
> -                       failed = stat("/etc", &sb);
> -
> +               else {
> +
> +                       srand(time(NULL));
> +                       switch(rand() % 4) {
> +                               case 0:
> +                                       failed = stat("/", &sb);
> +                                       break;
> +                               case 1:
> +                                       failed = stat("/bin", &sb);
> +                                       break;
> +                               case 2:
> +                                       failed = stat("/sbin", &sb);
> +                                       break;
> +                               default:
> +                                       failed = stat("/usr", &sb);
> +                       }
> +               }
>                 error = watchdog_getuptime(&ts_end);
>                 if (error) {
>                         end_program = 1;
>

I don't think the rand helps at all. I think you'd really rather do things
sequentially. And this introduces more assumptions about the underlying
filesystem(s).

Warner