From 27ab1c1c06529056df498b9647c03167e682b4d9 Mon Sep 17 00:00:00 2001 From: Namhyung Kim Date: Wed, 16 Dec 2020 18:05:54 +0900 Subject: 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: Namhyung Kim Cc: Alexander Shishkin Cc: Andi Kleen Cc: Ian Rogers Cc: Jiri Olsa Cc: Mark Rutland Cc: Peter Zijlstra Cc: Stephane Eranian Link: http://lore.kernel.org/lkml/20201216090556.813996-1-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- tools/lib/api/fs/cgroup.c | 34 +++++++++++++++------------------- 1 file changed, 15 insertions(+), 19 deletions(-) (limited to 'tools/lib') diff --git a/tools/lib/api/fs/cgroup.c b/tools/lib/api/fs/cgroup.c index 889a6eb4aaca..813236d8ca48 100644 --- a/tools/lib/api/fs/cgroup.c +++ b/tools/lib/api/fs/cgroup.c @@ -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; -- cgit v1.2.3