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Subject[PATCH 2/3] tools/lib/fs: Diet cgroupfs_find_mountpoint()
Date
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
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