Commit 27ab1c1c authored by Namhyung Kim's avatar Namhyung Kim Committed by Arnaldo Carvalho de Melo
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tools api fs: Prefer cgroup v1 path in cgroupfs_find_mountpoint() 



The cgroupfs_find_mountpoint() looks up the /proc/mounts file to find
a directory for the given cgroup subsystem.  It keeps both cgroup v1
and v2 path since there's a possibility of the mixed hierarchly.

But we can simply use v1 path if it's found as it will override the v2
hierarchy.

Signed-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20201216090556.813996-1-namhyung@kernel.org


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 6833e0b8

tools/lib/api/fs/cgroup.c

+15 −19
Original line number Diff line number Diff line
@@ -12,7 +12,7 @@ int cgroupfs_find_mountpoint(char *buf, size_t maxlen, const char *subsys) 
{

	FILE *fp;

	char mountpoint[PATH_MAX + 1], tokens[PATH_MAX + 1], type[PATH_MAX + 1];

	char path_v1[PATH_MAX + 1], path_v2[PATH_MAX + 2], *path;

	char path_v2[PATH_MAX + 1];

	char *token, *saved_ptr = NULL;



	fp = fopen("/proc/mounts", "r");
@@ -22,45 +22,41 @@ int cgroupfs_find_mountpoint(char *buf, size_t maxlen, const char *subsys) 
	/*

	 * in order to handle split hierarchy, we need to scan /proc/mounts

	 * and inspect every cgroupfs mount point to find one that has

	 * perf_event subsystem

	 * the given subsystem.  If we found v1, just use it.  If not we can

	 * use v2 path as a fallback.

	 */

	path_v1[0] = '\0';

	path_v2[0] = '\0';



	while (fscanf(fp, "%*s %"__stringify(PATH_MAX)"s %"__stringify(PATH_MAX)"s %"

				__stringify(PATH_MAX)"s %*d %*d\n",

				mountpoint, type, tokens) == 3) {



		if (!path_v1[0] && !strcmp(type, "cgroup")) {

		if (!strcmp(type, "cgroup")) {



			token = strtok_r(tokens, ",", &saved_ptr);



			while (token != NULL) {

				if (subsys && !strcmp(token, subsys)) {

					strcpy(path_v1, mountpoint);

					break;

					/* found */

					fclose(fp);



					if (strlen(mountpoint) < maxlen) {

						strcpy(buf, mountpoint);

						return 0;

					}

					return -1;

				}

				token = strtok_r(NULL, ",", &saved_ptr);

			}

		}



		if (!path_v2[0] && !strcmp(type, "cgroup2"))

		if (!strcmp(type, "cgroup2"))

			strcpy(path_v2, mountpoint);



		if (path_v1[0] && path_v2[0])

			break;

	}

	fclose(fp);



	if (path_v1[0])

		path = path_v1;

	else if (path_v2[0])

		path = path_v2;

	else

		return -1;



	if (strlen(path) < maxlen) {

		strcpy(buf, path);

	if (path_v2[0] && strlen(path_v2) < maxlen) {

		strcpy(buf, path_v2);

		return 0;

	}

	return -1;