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

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Date:   Tue, 29 Dec 2020 10:39:40 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Namhyung Kim <namhyung@...nel.org>
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()

On Tue, Dec 29, 2020 at 02:27:36PM +0900, Namhyung Kim wrote:
> 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.

aah right, sry ;-) looks ok

jirka