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tools api fs: Prefer cgroup v1 path in cgroupfs_find_mountpoint()

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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: Namhyung 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: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Namhyung Kim 2020-12-16 18:05:54 +09:00 committed by Arnaldo Carvalho de Melo
parent 6833e0b81a
commit 27ab1c1c06
1 changed files with 15 additions and 19 deletions
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34
tools/lib/api/fs/cgroup.c
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@ -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;