| 1 | |
| 2 | #include <linux/stringify.h>
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| 3 | #include <sys/types.h>
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| 4 | #include <sys/stat.h>
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| 5 | #include <fcntl.h>
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| 6 | #include <stdio.h>
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| 7 | #include <stdlib.h>
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| 8 | #include <string.h>
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| 9 | #include "fs.h"
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| 10 |
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| 11 | struct cgroupfs_cache_entry {
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| 12 | char subsys[32];
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| 13 | char mountpoint[PATH_MAX];
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| 14 | };
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| 15 |
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| 16 |
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| 17 | static struct cgroupfs_cache_entry *cached;
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| 18 |
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| 19 | int cgroupfs_find_mountpoint(char *buf, size_t maxlen, const char *subsys)
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| 20 | {
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| 21 | FILE *fp;
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| 22 | char *line = NULL;
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| 23 | size_t len = 0;
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| 24 | char *p, *path;
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| 25 | char mountpoint[PATH_MAX];
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| 26 |
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| 27 | if (cached && !strcmp(cached->subsys, subsys)) {
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| 28 | if (strlen(cached->mountpoint) < maxlen) {
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| 29 | strcpy(buf, cached->mountpoint);
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| 30 | return 0;
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| 31 | }
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| 32 | return -1;
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| 33 | }
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| 34 |
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| 35 | fp = fopen("/proc/mounts", "r");
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| 36 | if (!fp)
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| 37 | return -1;
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| 38 |
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| 39 | |
| 40 | * in order to handle split hierarchy, we need to scan /proc/mounts
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| 41 | * and inspect every cgroupfs mount point to find one that has
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| 42 | * the given subsystem. If we found v1, just use it. If not we can
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| 43 | * use v2 path as a fallback.
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| 44 |
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| 45 | mountpoint[0] = '\0';
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| 46 |
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| 47 | |
| 48 | * The /proc/mounts has the follow format:
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| 49 | *
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| 50 | * <devname> <mount point> <fs type> <options> ...
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| 51 | *
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| 52 |
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| 53 | while (getline(&line, &len, fp) != -1) {
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| 54 |
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| 55 | p = strchr(line, ' ');
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| 56 | if (p == NULL)
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| 57 | continue;
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| 58 |
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| 59 |
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| 60 | path = ++p;
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| 61 | p = strchr(p, ' ');
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| 62 | if (p == NULL)
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| 63 | continue;
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| 64 |
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| 65 | *p++ = '\0';
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| 66 |
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| 67 |
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| 68 | if (strncmp(p, "cgroup", 6))
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| 69 | continue;
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| 70 |
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| 71 | if (p[6] == '2') {
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| 72 |
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| 73 | strcpy(mountpoint, path);
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| 74 | continue;
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| 75 | }
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| 76 |
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| 77 |
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| 78 | p += 7;
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| 79 |
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| 80 | p = strstr(p, subsys);
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| 81 | if (p == NULL)
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| 82 | continue;
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| 83 |
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| 84 |
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| 85 | if (!strchr(" ,", p[-1]) || !strchr(" ,", p[strlen(subsys)]))
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| 86 | continue;
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| 87 |
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| 88 | strcpy(mountpoint, path);
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| 89 | break;
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| 90 | }
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| 91 | free(line);
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| 92 | fclose(fp);
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| 93 |
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| 94 | if (!cached)
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| 95 | cached = calloc(1, sizeof(*cached));
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| 96 |
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| 97 | if (cached) {
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| 98 | strncpy(cached->subsys, subsys, sizeof(cached->subsys) - 1);
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| 99 | strcpy(cached->mountpoint, mountpoint);
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| 100 | }
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| 101 |
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| 102 | if (mountpoint[0] && strlen(mountpoint) < maxlen) {
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| 103 | strcpy(buf, mountpoint);
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| 104 | return 0;
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| 105 | }
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| 106 | return -1;
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| 107 | }
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