cgroups: simplify current cgroup retrieval on pure unified cgroup layouts

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/src/lxc/cgroups/cgfsng.c b/src/lxc/cgroups/cgfsng.c
index e451658a3cb40c085252519292deec0d2edebf3c..611536695782dfeecc80fa969219724f69a862f6 100644 (file)
--- a/src/lxc/cgroups/cgfsng.c
+++ b/src/lxc/cgroups/cgfsng.c
@@ -3419,41 +3419,39 @@ static int cg_hybrid_init(struct cgroup_ops *ops, bool relative, bool unprivileg
 }
 
 /* Get current cgroup from /proc/self/cgroup for the cgroupfs v2 hierarchy. */
-static char *cg_unified_get_current_cgroup(bool relative)
+static char *current_cgroup_unified(bool relative)
 {
-       __do_free char *basecginfo = NULL, *copy = NULL;
-       char *base_cgroup;
+       __do_free char *cgroup_info = NULL;
+       char *it;
 
        if (!relative && (geteuid() == 0))
-               basecginfo = read_file_at(-EBADF, "/proc/1/cgroup", PROTECT_OPEN, 0);
+               cgroup_info = read_file_at(-EBADF, "/proc/1/cgroup", PROTECT_OPEN, 0);
        else
-               basecginfo = read_file_at(-EBADF, "/proc/self/cgroup", PROTECT_OPEN, 0);
-       if (!basecginfo)
+               cgroup_info = read_file_at(-EBADF, "/proc/self/cgroup", PROTECT_OPEN, 0);
+       if (!cgroup_info)
                return NULL;
 
-       base_cgroup = strstr(basecginfo, "0::/");
-       if (!base_cgroup)
-               return NULL;
+       lxc_iterate_parts(it, cgroup_info, "\n") {
+               if (*it != '0')
+                       continue;
 
-       base_cgroup = base_cgroup + 3;
-       copy = copy_to_eol(base_cgroup);
-       if (!copy)
-               return NULL;
-       trim(copy);
+               it += STRLITERALLEN("0::");
 
-       if (!relative) {
-               base_cgroup = prune_init_scope(copy);
-               if (!base_cgroup)
-                       return NULL;
-       } else {
-               base_cgroup = copy;
-       }
+               if (!abspath(it))
+                       return log_error(NULL, "Corrupt cgroup info for %s process", relative ? "current" : "init");
 
-       if (abspath(base_cgroup))
-               base_cgroup = deabs(base_cgroup);
+               /* remove init.scope */
+               if (!relative)
+                       it = prune_init_scope(it);
+
+               /* create a relative path */
+               it = deabs(it);
+
+               return strdup(it);
+       }
 
-       /* We're allowing base_cgroup to be "". */
-       return strdup(base_cgroup);
+       return log_error(NULL, "Failed to retrieve current cgroup for %s process",
+                        relative ? "current" : "init");
 }
 
 static int cg_unified_init(struct cgroup_ops *ops, bool relative,
@@ -3462,7 +3460,7 @@ static int cg_unified_init(struct cgroup_ops *ops, bool relative,
        __do_free char *base_cgroup = NULL;
        int ret;
 
-       base_cgroup = cg_unified_get_current_cgroup(relative);
+       base_cgroup = current_cgroup_unified(relative);
        if (!base_cgroup)
                return ret_errno(EINVAL);