From: Namhyung Kim <namhyung@kernel.org>
To: Arnaldo Carvalho de Melo <acme@kernel.org>, Jiri Olsa <jolsa@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
LKML <linux-kernel@vger.kernel.org>,
Stephane Eranian <eranian@google.com>,
Ian Rogers <irogers@google.com>, Andi Kleen <ak@linux.intel.com>
Subject: [PATCH 2/3] tools/lib/fs: Diet cgroupfs_find_mountpoint()
Date: Wed, 16 Dec 2020 18:05:55 +0900 [thread overview]
Message-ID: <20201216090556.813996-2-namhyung@kernel.org> (raw)
In-Reply-To: <20201216090556.813996-1-namhyung@kernel.org>
Reduce the number of buffers and hopefully make it more efficient. :)
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
tools/lib/api/fs/cgroup.c | 70 +++++++++++++++++++++++++--------------
1 file changed, 45 insertions(+), 25 deletions(-)
diff --git a/tools/lib/api/fs/cgroup.c b/tools/lib/api/fs/cgroup.c
index 813236d8ca48..262a4229e293 100644
--- a/tools/lib/api/fs/cgroup.c
+++ b/tools/lib/api/fs/cgroup.c
@@ -11,9 +11,10 @@
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_v2[PATH_MAX + 1];
- char *token, *saved_ptr = NULL;
+ char *line = NULL;
+ size_t len = 0;
+ char *p, *path;
+ char mountpoint[PATH_MAX];
fp = fopen("/proc/mounts", "r");
if (!fp)
@@ -25,38 +26,57 @@ int cgroupfs_find_mountpoint(char *buf, size_t maxlen, const char *subsys)
* the given subsystem. If we found v1, just use it. If not we can
* use v2 path as a fallback.
*/
- path_v2[0] = '\0';
+ mountpoint[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) {
+ /*
+ * The /proc/mounts has the follow format:
+ *
+ * <devname> <mount point> <fs type> <options> ...
+ *
+ */
+ while (getline(&line, &len, fp) != -1) {
+ /* skip devname */
+ p = strchr(line, ' ');
+ if (p == NULL)
+ continue;
- if (!strcmp(type, "cgroup")) {
+ /* save the mount point */
+ path = ++p;
+ p = strchr(p, ' ');
+ if (p == NULL)
+ continue;
- token = strtok_r(tokens, ",", &saved_ptr);
+ *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);
+ 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
next prev parent reply other threads:[~2020-12-16 9:07 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-16 9:05 [PATCH 1/3] tools/lib/fs: Prefer cgroup v1 path Namhyung Kim
2020-12-16 9:05 ` Namhyung Kim [this message]
2020-12-28 8:31 ` [PATCH 2/3] tools/lib/fs: Diet cgroupfs_find_mountpoint() Jiri Olsa
2020-12-29 5:27 ` Namhyung Kim
2020-12-29 9:39 ` Jiri Olsa
2020-12-16 9:05 ` [PATCH 3/3] tools/lib/fs: Cache cgroupfs mount point Namhyung Kim
2020-12-29 11:51 ` Arnaldo Carvalho de Melo
2021-01-06 1:33 ` Namhyung Kim
2021-01-08 5:51 ` Namhyung Kim
2021-01-21 4:33 ` Namhyung Kim
2021-02-17 12:58 ` Arnaldo Carvalho de Melo
2021-02-19 10:05 ` Namhyung Kim
2021-02-19 11:37 ` Arnaldo Carvalho de Melo
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