api.c: cgget: cgset: Add cgroup v2 support

This commit adds cgroup v2 support to cgroup_init(). With these
changes, cgget and cgset now work on a cgroup v1 mount, a cgroup
v2 mount, or a cgroup v2 unified mount hierarchy.

Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>

diff --git a/src/api.c b/src/api.c
index 2ced9298a2752d7ff787e70a502a18330b0693de..1219cd0356b942308f7aa291b1b9c67315cac1bb 100644 (file)
--- a/src/api.c
+++ b/src/api.c
@@ -63,6 +63,12 @@ static __thread char errtext[MAXLEN];
 /* Task command name length */
 #define TASK_COMM_LEN 16
 
+/* cgroup v2 controllers file */
+#define CGV2_CONTROLLERS_FILE "cgroup.controllers"
+
+/* maximum line length when reading the cgroup.controllers file */
+#define LL_MAX                 100
+
 /* Check if cgroup_init has been called or not. */
 static int cgroup_initialized;
 
@@ -1148,6 +1154,91 @@ out:
        return ret;
 }
 
+/**
+ * Process a cgroup v2 mount and add it to cg_mount_table if it's not a
+ * duplicate.
+ *
+ *     @param ent File system description of cgroup mount being processed
+ *     @param mnt_tbl_idx cg_mount_table index
+ */
+static int cgroup_process_v2_mnt(struct mntent *ent, int *mnt_tbl_idx)
+{
+       char cgroup_controllers_path[FILENAME_MAX];
+       char *ret_c = NULL, line[LL_MAX], *stok_buff = NULL, *controller;
+       int ret = 0, i, duplicate;
+       FILE *fp = NULL;
+
+       /* determine what v2 controllers are available on this mount */
+       snprintf(cgroup_controllers_path, FILENAME_MAX, "%s/%s", ent->mnt_dir,
+                CGV2_CONTROLLERS_FILE);
+
+       fp = fopen(cgroup_controllers_path, "re");
+       if (!fp) {
+               ret = ECGOTHER;
+               goto out;
+       }
+
+       ret_c = fgets(line, LL_MAX, fp);
+       if (ret_c == NULL) {
+               ret = ECGEOF;
+               goto out;
+       }
+
+       /* remove the trailing newline */
+       ret_c[strlen(ret_c) - 1] = '\0';
+
+       /*
+        * cgroup.controllers returns a list of available controllers in
+        * the following format:
+        *      cpuset cpu io memory pids rdma
+        */
+       controller = strtok_r(ret_c, " ", &stok_buff);
+       do {
+               /* do not have duplicates in mount table */
+               duplicate = 0;
+
+               for  (i = 0; i < *mnt_tbl_idx; i++) {
+                       if (strncmp(cg_mount_table[i].name, controller,
+                                       FILENAME_MAX) == 0) {
+                               duplicate = 1;
+                               break;
+                       }
+               }
+
+               if (duplicate) {
+                       cgroup_dbg("controller %s is already mounted on %s\n",
+                               controller, cg_mount_table[i].mount.path);
+
+                       ret = cg_add_duplicate_mount(&cg_mount_table[i],
+                                       ent->mnt_dir);
+                       if (ret)
+                               break;
+
+                       continue;
+               }
+
+               /* this controller is not in the mount table.  add it */
+               strncpy(cg_mount_table[*mnt_tbl_idx].name,
+                       controller, FILENAME_MAX);
+               cg_mount_table[*mnt_tbl_idx].name[FILENAME_MAX-1] = '\0';
+               strncpy(cg_mount_table[*mnt_tbl_idx].mount.path,
+                       ent->mnt_dir, FILENAME_MAX);
+               cg_mount_table[*mnt_tbl_idx].mount.path[FILENAME_MAX-1] =
+                       '\0';
+               cg_mount_table[*mnt_tbl_idx].version = CGROUP_V2;
+               cg_mount_table[*mnt_tbl_idx].mount.next = NULL;
+               cgroup_dbg("Found cgroup option %s, count %d\n",
+                       controller, *mnt_tbl_idx);
+               (*mnt_tbl_idx)++;
+       } while ((controller = strtok_r(NULL, " ", &stok_buff)));
+
+out:
+       if (fp)
+               fclose(fp);
+
+       return ret;
+}
+
 /**
  * cgroup_init(), initializes the MOUNT_POINT.
  *
@@ -1256,6 +1347,18 @@ int cgroup_init(void)
                        if (ret)
                                goto unlock_exit;
                }
+               else if (strcmp(ent->mnt_type, "cgroup2") == 0) {
+                       ret = cgroup_process_v2_mnt(ent, &found_mnt);
+                       if (ret == ECGEOF) {
+                               /* The controllers file was empty.  Ignore and
+                                * move on.
+                                */
+                               ret = 0;
+                               continue;
+                       } else if (ret) {
+                               goto unlock_exit;
+                       }
+               }
        }
 
        free(temp_ent);