103 lines
2.0 KiB
C
103 lines
2.0 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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#include <linux/stringify.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "fs.h"
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struct cgroupfs_cache_entry {
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char subsys[32];
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char mountpoint[PATH_MAX];
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};
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/* just cache last used one */
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static struct cgroupfs_cache_entry cached;
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int cgroupfs_find_mountpoint(char *buf, size_t maxlen, const char *subsys)
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{
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FILE *fp;
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char *line = NULL;
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size_t len = 0;
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char *p, *path;
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char mountpoint[PATH_MAX];
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if (!strcmp(cached.subsys, subsys)) {
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if (strlen(cached.mountpoint) < maxlen) {
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strcpy(buf, cached.mountpoint);
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return 0;
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}
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return -1;
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}
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fp = fopen("/proc/mounts", "r");
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if (!fp)
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return -1;
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/*
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* in order to handle split hierarchy, we need to scan /proc/mounts
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* and inspect every cgroupfs mount point to find one that has
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* the given subsystem. If we found v1, just use it. If not we can
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* use v2 path as a fallback.
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*/
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mountpoint[0] = '\0';
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/*
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* The /proc/mounts has the follow format:
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*
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* <devname> <mount point> <fs type> <options> ...
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*
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*/
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while (getline(&line, &len, fp) != -1) {
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/* skip devname */
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p = strchr(line, ' ');
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if (p == NULL)
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continue;
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/* save the mount point */
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path = ++p;
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p = strchr(p, ' ');
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if (p == NULL)
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continue;
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*p++ = '\0';
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/* check filesystem type */
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if (strncmp(p, "cgroup", 6))
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continue;
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if (p[6] == '2') {
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/* save cgroup v2 path */
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strcpy(mountpoint, path);
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continue;
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}
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/* now we have cgroup v1, check the options for subsystem */
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p += 7;
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p = strstr(p, subsys);
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if (p == NULL)
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continue;
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/* sanity check: it should be separated by a space or a comma */
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if (!strchr(" ,", p[-1]) || !strchr(" ,", p[strlen(subsys)]))
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continue;
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strcpy(mountpoint, path);
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break;
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}
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free(line);
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fclose(fp);
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strncpy(cached.subsys, subsys, sizeof(cached.subsys) - 1);
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strcpy(cached.mountpoint, mountpoint);
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if (mountpoint[0] && strlen(mountpoint) < maxlen) {
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strcpy(buf, mountpoint);
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return 0;
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}
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return -1;
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}
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