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

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Message-ID: <20201228083120.GA450923@krava>
Date:   Mon, 28 Dec 2020 09:31:20 +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 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

jirka

> +		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;
> +
> +		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
>