linux-kernel - Re: [PATCH 2/3] tools/lib/fs: Diet cgroupfs_find

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Message-ID: <CAM9d7cicPSLeMa25=GOsrzMBzk-Oz6XfA1NP=nOsH3fkvgkrmg@mail.gmail.com>
Date:   Tue, 29 Dec 2020 14:27:36 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Stephane Eranian <eranian@...gle.com>,
        Ian Rogers <irogers@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 2/3] tools/lib/fs: Diet cgroupfs_find_mountpoint()

Hi Jiri,

On Mon, Dec 28, 2020 at 5:31 PM Jiri Olsa <jolsa@...hat.com> wrote:
>
> On Wed, Dec 16, 2020 at 06:05:55PM +0900, Namhyung Kim wrote:
>
> SNIP
>
> > +             *p++ = '\0';
> >
> > -                     while (token != NULL) {
> > -                             if (subsys && !strcmp(token, subsys)) {
> > -                                     /* found */
> > -                                     fclose(fp);
> > +             /* check filesystem type */
> > +             if (strncmp(p, "cgroup", 6))
> > +                     continue;
> >
> > -                                     if (strlen(mountpoint) < maxlen) {
> > -                                             strcpy(buf, mountpoint);
> > -                                             return 0;
> > -                                     }
> > -                                     return -1;
> > -                             }
> > -                             token = strtok_r(NULL, ",", &saved_ptr);
> > -                     }
> > +             if (p[6] == '2') {
> > +                     /* save cgroup v2 path */
> > +                     strcpy(mountpoint, path);
> > +                     continue;
> >               }
> >
> > -             if (!strcmp(type, "cgroup2"))
> > -                     strcpy(path_v2, mountpoint);
> > +             /* now we have cgroup v1, check the options for subsystem */
> > +             p += 7;
> > +
> > +             p = strstr(p, subsys);
>
> not sure this is a real problem, but this would mixe up for
> cpu/cpuacct/cpuset no? we are using the function for perf_event
> subsys only, but it's globaly availble

Yeah, that's why I added the sanity check below. :)

>
> > +             if (p == NULL)
> > +                     continue;
> > +
> > +             /* sanity check: it should be separated by a space or a comma */
> > +             if (!strchr(" ,", p[-1]) || !strchr(" ,", p[strlen(subsys)]))
> > +                     continue;

Here.

Thanks,
Namhyung


> > +
> > +             strcpy(mountpoint, path);
> > +             break;
> >       }
> > +     free(line);
> >       fclose(fp);
> >
> > -     if (path_v2[0] && strlen(path_v2) < maxlen) {
> > -             strcpy(buf, path_v2);
> > +     if (mountpoint[0] && strlen(mountpoint) < maxlen) {
> > +             strcpy(buf, mountpoint);
> >               return 0;
> >       }
> >       return -1;
> > --
> > 2.29.2.684.gfbc64c5ab5-goog
> >
>