tools lib api fs: Move cgroupsfs_find_mountpoint()

Move it from tools/perf/util/cgroup.c as it can be used by other places.
Note that cgroup filesystem is different from others since it's usually
mounted separately (in v1) for each subsystem.

I just copied the code with a little modification to pass a name of
subsystem.

Suggested-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lore.kernel.org/lkml/20200127100031.1368732-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 2 insertions, 61 deletions

diff --git a/tools/perf/util/cgroup.c b/tools/perf/util/cgroup.c
index 4881d4af3381..5bc9d3b01bd9 100644
--- a/tools/perf/util/cgroup.c
+++ b/tools/perf/util/cgroup.c
@@ -3,75 +3,16 @@
 #include "evsel.h"
 #include "cgroup.h"
 #include "evlist.h"
-#include <linux/stringify.h>
 #include <linux/zalloc.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <stdlib.h>
 #include <string.h>
+#include <api/fs/fs.h>
 
 int nr_cgroups;
 
-static int
-cgroupfs_find_mountpoint(char *buf, size_t maxlen)
-{
-	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 *token, *saved_ptr = NULL;
-
-	fp = fopen("/proc/mounts", "r");
-	if (!fp)
-		return -1;
-
-	/*
-	 * 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
-	 */
-	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")) {
-
-			token = strtok_r(tokens, ",", &saved_ptr);
-
-			while (token != NULL) {
-				if (!strcmp(token, "perf_event")) {
-					strcpy(path_v1, mountpoint);
-					break;
-				}
-				token = strtok_r(NULL, ",", &saved_ptr);
-			}
-		}
-
-		if (!path_v2[0] && !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);
-		return 0;
-	}
-	return -1;
-}
-
 static int open_cgroup(const char *name)
 {
 	char path[PATH_MAX + 1];
@@ -79,7 +20,7 @@ static int open_cgroup(const char *name)
 	int fd;
 
 
-	if (cgroupfs_find_mountpoint(mnt, PATH_MAX + 1))
+	if (cgroupfs_find_mountpoint(mnt, PATH_MAX + 1, "perf_event"))
 		return -1;
 
 	scnprintf(path, PATH_MAX, "%s/%s", mnt, name);