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tools api fs: Diet cgroupfs_find_mountpoint()

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Reduce the number of buffers and hopefully make it more efficient. :)

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.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/20201216090556.813996-2-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Namhyung Kim 2020-12-16 18:05:55 +09:00 committed by Arnaldo Carvalho de Melo
parent 27ab1c1c06
commit 6fd99b7f62
1 changed files with 45 additions and 25 deletions
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70
tools/lib/api/fs/cgroup.c
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@ -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;