Merge pull request #5444 from poettering/cgroups-revert-no-error

Revert "core: simplify cg_[all_]unified()" and more.

12 files changed, 207 insertions, 91 deletions

diff --git a/src/basic/cgroup-util.c b/src/basic/cgroup-util.c
index f76b7f47e5..bda5c555ad 100644
--- a/src/basic/cgroup-util.c
+++ b/src/basic/cgroup-util.c
@@ -208,7 +208,13 @@ int cg_rmdir(const char *controller, const char *path) {
         if (r < 0 && errno != ENOENT)
                 return -errno;
 
-        if (streq(controller, SYSTEMD_CGROUP_CONTROLLER) && cg_hybrid_unified()) {
+        r = cg_hybrid_unified();
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return 0;
+
+        if (streq(controller, SYSTEMD_CGROUP_CONTROLLER)) {
                 r = cg_rmdir(SYSTEMD_CGROUP_CONTROLLER_LEGACY, path);
                 if (r < 0)
                         log_warning_errno(r, "Failed to remove compat systemd cgroup %s: %m", path);
@@ -549,7 +555,7 @@ static const char *controller_to_dirname(const char *controller) {
          * hierarchies, if it is specified. */
 
         if (streq(controller, SYSTEMD_CGROUP_CONTROLLER)) {
-                if (cg_hybrid_unified())
+                if (cg_hybrid_unified() > 0)
                         controller = SYSTEMD_CGROUP_CONTROLLER_HYBRID;
                 else
                         controller = SYSTEMD_CGROUP_CONTROLLER_LEGACY;
@@ -636,7 +642,10 @@ int cg_get_path(const char *controller, const char *path, const char *suffix, ch
         if (!cg_controller_is_valid(controller))
                 return -EINVAL;
 
-        if (cg_all_unified())
+        r = cg_all_unified();
+        if (r < 0)
+                return r;
+        if (r > 0)
                 r = join_path_unified(path, suffix, fs);
         else
                 r = join_path_legacy(controller, path, suffix, fs);
@@ -648,6 +657,7 @@ int cg_get_path(const char *controller, const char *path, const char *suffix, ch
 }
 
 static int controller_is_accessible(const char *controller) {
+        int r;
 
         assert(controller);
 
@@ -659,7 +669,10 @@ static int controller_is_accessible(const char *controller) {
         if (!cg_controller_is_valid(controller))
                 return -EINVAL;
 
-        if (cg_all_unified()) {
+        r = cg_all_unified();
+        if (r < 0)
+                return r;
+        if (r > 0) {
                 /* We don't support named hierarchies if we are using
                  * the unified hierarchy. */
 
@@ -736,7 +749,10 @@ int cg_trim(const char *controller, const char *path, bool delete_root) {
                         return -errno;
         }
 
-        if (streq(controller, SYSTEMD_CGROUP_CONTROLLER) && cg_hybrid_unified()) {
+        q = cg_hybrid_unified();
+        if (q < 0)
+                return q;
+        if (q > 0 && streq(controller, SYSTEMD_CGROUP_CONTROLLER)) {
                 q = cg_trim(SYSTEMD_CGROUP_CONTROLLER_LEGACY, path, delete_root);
                 if (q < 0)
                         log_warning_errno(q, "Failed to trim compat systemd cgroup %s: %m", path);
@@ -765,7 +781,11 @@ int cg_create(const char *controller, const char *path) {
                 return -errno;
         }
 
-        if (streq(controller, SYSTEMD_CGROUP_CONTROLLER) && cg_hybrid_unified()) {
+        r = cg_hybrid_unified();
+        if (r < 0)
+                return r;
+
+        if (r > 0 && streq(controller, SYSTEMD_CGROUP_CONTROLLER)) {
                 r = cg_create(SYSTEMD_CGROUP_CONTROLLER_LEGACY, path);
                 if (r < 0)
                         log_warning_errno(r, "Failed to create compat systemd cgroup %s: %m", path);
@@ -812,7 +832,11 @@ int cg_attach(const char *controller, const char *path, pid_t pid) {
         if (r < 0)
                 return r;
 
-        if (streq(controller, SYSTEMD_CGROUP_CONTROLLER) && cg_hybrid_unified()) {
+        r = cg_hybrid_unified();
+        if (r < 0)
+                return r;
+
+        if (r > 0 && streq(controller, SYSTEMD_CGROUP_CONTROLLER)) {
                 r = cg_attach(SYSTEMD_CGROUP_CONTROLLER_LEGACY, path, pid);
                 if (r < 0)
                         log_warning_errno(r, "Failed to attach %d to compat systemd cgroup %s: %m", pid, path);
@@ -871,7 +895,10 @@ int cg_set_group_access(
         if (r < 0)
                 return r;
 
-        if (streq(controller, SYSTEMD_CGROUP_CONTROLLER) && cg_hybrid_unified()) {
+        r = cg_hybrid_unified();
+        if (r < 0)
+                return r;
+        if (r > 0 && streq(controller, SYSTEMD_CGROUP_CONTROLLER)) {
                 r = cg_set_group_access(SYSTEMD_CGROUP_CONTROLLER_LEGACY, path, mode, uid, gid);
                 if (r < 0)
                         log_warning_errno(r, "Failed to set group access on compat systemd cgroup %s: %m", path);
@@ -906,14 +933,20 @@ int cg_set_task_access(
         if (r < 0)
                 return r;
 
-        if (!cg_unified(controller)) {
+        r = cg_unified_controller(controller);
+        if (r < 0)
+                return r;
+        if (r == 0) {
                 /* Compatibility, Always keep values for "tasks" in sync with
                  * "cgroup.procs" */
                 if (cg_get_path(controller, path, "tasks", &procs) >= 0)
                         (void) chmod_and_chown(procs, mode, uid, gid);
         }
 
-        if (streq(controller, SYSTEMD_CGROUP_CONTROLLER) && cg_hybrid_unified()) {
+        r = cg_hybrid_unified();
+        if (r < 0)
+                return r;
+        if (r > 0 && streq(controller, SYSTEMD_CGROUP_CONTROLLER)) {
                 r = cg_set_task_access(SYSTEMD_CGROUP_CONTROLLER_LEGACY, path, mode, uid, gid);
                 if (r < 0)
                         log_warning_errno(r, "Failed to set task access on compat systemd cgroup %s: %m", path);
@@ -964,7 +997,7 @@ int cg_pid_get_path(const char *controller, pid_t pid, char **path) {
         char line[LINE_MAX];
         const char *fs, *controller_str;
         size_t cs = 0;
-        bool unified;
+        int unified;
 
         assert(path);
         assert(pid >= 0);
@@ -975,8 +1008,10 @@ int cg_pid_get_path(const char *controller, pid_t pid, char **path) {
         } else
                 controller = SYSTEMD_CGROUP_CONTROLLER;
 
-        unified = cg_unified(controller);
-        if (!unified) {
+        unified = cg_unified_controller(controller);
+        if (unified < 0)
+                return unified;
+        if (unified == 0) {
                 if (streq(controller, SYSTEMD_CGROUP_CONTROLLER))
                         controller_str = SYSTEMD_CGROUP_CONTROLLER_LEGACY;
                 else
@@ -1048,7 +1083,10 @@ int cg_install_release_agent(const char *controller, const char *agent) {
 
         assert(agent);
 
-        if (cg_unified(controller)) /* doesn't apply to unified hierarchy */
+        r = cg_unified_controller(controller);
+        if (r < 0)
+                return r;
+        if (r > 0) /* doesn't apply to unified hierarchy */
                 return -EOPNOTSUPP;
 
         r = cg_get_path(controller, NULL, "release_agent", &fs);
@@ -1096,7 +1134,10 @@ int cg_uninstall_release_agent(const char *controller) {
         _cleanup_free_ char *fs = NULL;
         int r;
 
-        if (cg_unified(controller)) /* Doesn't apply to unified hierarchy */
+        r = cg_unified_controller(controller);
+        if (r < 0)
+                return r;
+        if (r > 0) /* Doesn't apply to unified hierarchy */
                 return -EOPNOTSUPP;
 
         r = cg_get_path(controller, NULL, "notify_on_release", &fs);
@@ -1149,7 +1190,10 @@ int cg_is_empty_recursive(const char *controller, const char *path) {
         if (controller && (isempty(path) || path_equal(path, "/")))
                 return false;
 
-        if (cg_unified(controller)) {
+        r = cg_unified_controller(controller);
+        if (r < 0)
+                return r;
+        if (r > 0) {
                 _cleanup_free_ char *t = NULL;
 
                 /* On the unified hierarchy we can check empty state
@@ -2034,7 +2078,10 @@ int cg_create_everywhere(CGroupMask supported, CGroupMask mask, const char *path
                 return r;
 
         /* If we are in the unified hierarchy, we are done now */
-        if (cg_all_unified())
+        r = cg_all_unified();
+        if (r < 0)
+                return r;
+        if (r > 0)
                 return 0;
 
         /* Otherwise, do the same in the other hierarchies */
@@ -2061,7 +2108,10 @@ int cg_attach_everywhere(CGroupMask supported, const char *path, pid_t pid, cg_m
         if (r < 0)
                 return r;
 
-        if (cg_all_unified())
+        r = cg_all_unified();
+        if (r < 0)
+                return r;
+        if (r > 0)
                 return 0;
 
         for (c = 0; c < _CGROUP_CONTROLLER_MAX; c++) {
@@ -2102,7 +2152,7 @@ int cg_attach_many_everywhere(CGroupMask supported, const char *path, Set* pids,
 
 int cg_migrate_everywhere(CGroupMask supported, const char *from, const char *to, cg_migrate_callback_t to_callback, void *userdata) {
         CGroupController c;
-        int r = 0;
+        int r = 0, q;
 
         if (!path_equal(from, to))  {
                 r = cg_migrate_recursive(SYSTEMD_CGROUP_CONTROLLER, from, SYSTEMD_CGROUP_CONTROLLER, to, CGROUP_REMOVE);
@@ -2110,7 +2160,10 @@ int cg_migrate_everywhere(CGroupMask supported, const char *from, const char *to
                         return r;
         }
 
-        if (cg_all_unified())
+        q = cg_all_unified();
+        if (q < 0)
+                return q;
+        if (q > 0)
                 return r;
 
         for (c = 0; c < _CGROUP_CONTROLLER_MAX; c++) {
@@ -2134,13 +2187,16 @@ int cg_migrate_everywhere(CGroupMask supported, const char *from, const char *to
 
 int cg_trim_everywhere(CGroupMask supported, const char *path, bool delete_root) {
         CGroupController c;
-        int r;
+        int r, q;
 
         r = cg_trim(SYSTEMD_CGROUP_CONTROLLER, path, delete_root);
         if (r < 0)
                 return r;
 
-        if (cg_all_unified())
+        q = cg_all_unified();
+        if (q < 0)
+                return q;
+        if (q > 0)
                 return r;
 
         for (c = 0; c < _CGROUP_CONTROLLER_MAX; c++) {
@@ -2163,7 +2219,10 @@ int cg_mask_supported(CGroupMask *ret) {
          * includes controllers we can make sense of and that are
          * actually accessible. */
 
-        if (cg_all_unified()) {
+        r = cg_all_unified();
+        if (r < 0)
+                return r;
+        if (r > 0) {
                 _cleanup_free_ char *root = NULL, *controllers = NULL, *path = NULL;
                 const char *c;
 
@@ -2283,21 +2342,18 @@ int cg_kernel_controllers(Set *controllers) {
 
 static thread_local CGroupUnified unified_cache = CGROUP_UNIFIED_UNKNOWN;
 
-/* The hybrid mode was initially implemented in v232 and simply mounted
- * cgroup v2 on /sys/fs/cgroup/systemd.  This unfortunately broke other
- * tools (such as docker) which expected the v1 "name=systemd" hierarchy
- * on /sys/fs/cgroup/systemd.  From v233 and on, the hybrid mode mountnbs
- * v2 on /sys/fs/cgroup/unified and maintains "name=systemd" hierarchy
- * on /sys/fs/cgroup/systemd for compatibility with other tools.
+/* The hybrid mode was initially implemented in v232 and simply mounted cgroup v2 on /sys/fs/cgroup/systemd.  This
+ * unfortunately broke other tools (such as docker) which expected the v1 "name=systemd" hierarchy on
+ * /sys/fs/cgroup/systemd.  From v233 and on, the hybrid mode mountnbs v2 on /sys/fs/cgroup/unified and maintains
+ * "name=systemd" hierarchy on /sys/fs/cgroup/systemd for compatibility with other tools.
  *
- * To keep live upgrade working, we detect and support v232 layout.  When
- * v232 layout is detected, to keep cgroup v2 process management but
- * disable the compat dual layout, we return %true on
- * cg_unified(SYSTEMD_CGROUP_CONTROLLER) and %false on cg_hybrid_unified().
+ * To keep live upgrade working, we detect and support v232 layout.  When v232 layout is detected, to keep cgroup v2
+ * process management but disable the compat dual layout, we return %true on
+ * cg_unified_controller(SYSTEMD_CGROUP_CONTROLLER) and %false on cg_hybrid_unified().
  */
 static thread_local bool unified_systemd_v232;
 
-static int cg_update_unified(void) {
+static int cg_unified_update(void) {
 
         struct statfs fs;
 
@@ -2336,24 +2392,38 @@ static int cg_update_unified(void) {
         return 0;
 }
 
-bool cg_unified(const char *controller) {
+int cg_unified_controller(const char *controller) {
+        int r;
+
+        r = cg_unified_update();
+        if (r < 0)
+                return r;
 
-        assert(cg_update_unified() >= 0);
+        if (unified_cache == CGROUP_UNIFIED_NONE)
+                return false;
 
-        if (streq_ptr(controller, SYSTEMD_CGROUP_CONTROLLER))
-                return unified_cache >= CGROUP_UNIFIED_SYSTEMD;
-        else
-                return unified_cache >= CGROUP_UNIFIED_ALL;
+        if (unified_cache >= CGROUP_UNIFIED_ALL)
+                return true;
+
+        return streq_ptr(controller, SYSTEMD_CGROUP_CONTROLLER);
 }
 
-bool cg_all_unified(void) {
+int cg_all_unified(void) {
+        int r;
 
-        return cg_unified(NULL);
+        r = cg_unified_update();
+        if (r < 0)
+                return r;
+
+        return unified_cache >= CGROUP_UNIFIED_ALL;
 }
 
-bool cg_hybrid_unified(void) {
+int cg_hybrid_unified(void) {
+        int r;
 
-        assert(cg_update_unified() >= 0);
+        r = cg_unified_update();
+        if (r < 0)
+                return r;
 
         return unified_cache == CGROUP_UNIFIED_SYSTEMD && !unified_systemd_v232;
 }
@@ -2361,7 +2431,7 @@ bool cg_hybrid_unified(void) {
 int cg_unified_flush(void) {
         unified_cache = CGROUP_UNIFIED_UNKNOWN;
 
-        return cg_update_unified();
+        return cg_unified_update();
 }
 
 int cg_enable_everywhere(CGroupMask supported, CGroupMask mask, const char *p) {
@@ -2374,7 +2444,10 @@ int cg_enable_everywhere(CGroupMask supported, CGroupMask mask, const char *p) {
         if (supported == 0)
                 return 0;
 
-        if (!cg_all_unified()) /* on the legacy hiearchy there's no joining of controllers defined */
+        r = cg_all_unified();
+        if (r < 0)
+                return r;
+        if (r == 0) /* on the legacy hiearchy there's no joining of controllers defined */
                 return 0;
 
         r = cg_get_path(SYSTEMD_CGROUP_CONTROLLER, p, "cgroup.subtree_control", &fs);
@@ -2417,7 +2490,7 @@ bool cg_is_unified_wanted(void) {
         /* If the hierarchy is already mounted, then follow whatever
          * was chosen for it. */
         if (cg_unified_flush() >= 0)
-                return (wanted = cg_all_unified());
+                return (wanted = unified_cache >= CGROUP_UNIFIED_ALL);
 
         /* Otherwise, let's see what the kernel command line has to say.
          * Since checking is expensive, cache a non-error result. */
diff --git a/src/basic/cgroup-util.h b/src/basic/cgroup-util.h
index 3d14ec3d9d..a522095d95 100644
--- a/src/basic/cgroup-util.h
+++ b/src/basic/cgroup-util.h
@@ -240,9 +240,9 @@ int cg_kernel_controllers(Set *controllers);
 
 bool cg_ns_supported(void);
 
-bool cg_all_unified(void);
-bool cg_hybrid_unified(void);
-bool cg_unified(const char *controller);
+int cg_all_unified(void);
+int cg_hybrid_unified(void);
+int cg_unified_controller(const char *controller);
 int cg_unified_flush(void);
 
 bool cg_is_unified_wanted(void);
diff --git a/src/cgls/cgls.c b/src/cgls/cgls.c
index 40db82f9ae..1b746a0e13 100644
--- a/src/cgls/cgls.c
+++ b/src/cgls/cgls.c
@@ -158,7 +158,7 @@ static int parse_argv(int argc, char *argv[]) {
 
 static void show_cg_info(const char *controller, const char *path) {
 
-        if (!cg_all_unified() && controller && !streq(controller, SYSTEMD_CGROUP_CONTROLLER))
+        if (cg_all_unified() == 0 && controller && !streq(controller, SYSTEMD_CGROUP_CONTROLLER))
                 printf("Controller %s; ", controller);
 
         printf("Control group %s:\n", isempty(path) ? "/" : path);
diff --git a/src/cgtop/cgtop.c b/src/cgtop/cgtop.c
index 45c050c9c3..a1c0f48c89 100644
--- a/src/cgtop/cgtop.c
+++ b/src/cgtop/cgtop.c
@@ -133,12 +133,16 @@ static int process(
                 Group **ret) {
 
         Group *g;
-        int r;
+        int r, all_unified;
 
         assert(controller);
         assert(path);
         assert(a);
 
+        all_unified = cg_all_unified();
+        if (all_unified < 0)
+                return all_unified;
+
         g = hashmap_get(a, path);
         if (!g) {
                 g = hashmap_get(b, path);
@@ -214,7 +218,7 @@ static int process(
                 uint64_t new_usage;
                 nsec_t timestamp;
 
-                if (cg_all_unified()) {
+                if (all_unified) {
                         const char *keys[] = { "usage_usec", NULL };
                         _cleanup_free_ char *val = NULL;
 
@@ -274,10 +278,10 @@ static int process(
         } else if (streq(controller, "memory")) {
                 _cleanup_free_ char *p = NULL, *v = NULL;
 
-                if (!cg_all_unified())
-                        r = cg_get_path(controller, path, "memory.usage_in_bytes", &p);
-                else
+                if (all_unified)
                         r = cg_get_path(controller, path, "memory.current", &p);
+                else
+                        r = cg_get_path(controller, path, "memory.usage_in_bytes", &p);
                 if (r < 0)
                         return r;
 
@@ -294,14 +298,14 @@ static int process(
                 if (g->memory > 0)
                         g->memory_valid = true;
 
-        } else if ((streq(controller, "io") && cg_all_unified()) ||
-                   (streq(controller, "blkio") && !cg_all_unified())) {
+        } else if ((streq(controller, "io") && all_unified) ||
+                   (streq(controller, "blkio") && !all_unified)) {
                 _cleanup_fclose_ FILE *f = NULL;
                 _cleanup_free_ char *p = NULL;
                 uint64_t wr = 0, rd = 0;
                 nsec_t timestamp;
 
-                r = cg_get_path(controller, path, cg_all_unified() ? "io.stat" : "blkio.io_service_bytes", &p);
+                r = cg_get_path(controller, path, all_unified ? "io.stat" : "blkio.io_service_bytes", &p);
                 if (r < 0)
                         return r;
 
@@ -324,7 +328,7 @@ static int process(
                         l += strcspn(l, WHITESPACE);
                         l += strspn(l, WHITESPACE);
 
-                        if (cg_all_unified()) {
+                        if (all_unified) {
                                 while (!isempty(l)) {
                                         if (sscanf(l, "rbytes=%" SCNu64, &k))
                                                 rd += k;
diff --git a/src/core/cgroup.c b/src/core/cgroup.c
index fbb711782e..774b832a63 100644
--- a/src/core/cgroup.c
+++ b/src/core/cgroup.c
@@ -678,7 +678,7 @@ static void cgroup_context_apply(Unit *u, CGroupMask mask, ManagerState state) {
                 bool has_weight = cgroup_context_has_cpu_weight(c);
                 bool has_shares = cgroup_context_has_cpu_shares(c);
 
-                if (cg_all_unified()) {
+                if (cg_all_unified() > 0) {
                         uint64_t weight;
 
                         if (has_weight)
@@ -858,9 +858,8 @@ static void cgroup_context_apply(Unit *u, CGroupMask mask, ManagerState state) {
         }
 
         if ((mask & CGROUP_MASK_MEMORY) && !is_root) {
-                if (cg_all_unified()) {
-                        uint64_t max;
-                        uint64_t swap_max = CGROUP_LIMIT_MAX;
+                if (cg_all_unified() > 0) {
+                        uint64_t max, swap_max = CGROUP_LIMIT_MAX;
 
                         if (cgroup_context_has_unified_memory_config(c)) {
                                 max = c->memory_max;
@@ -1033,7 +1032,7 @@ CGroupMask unit_get_own_mask(Unit *u) {
                 e = unit_get_exec_context(u);
                 if (!e ||
                     exec_context_maintains_privileges(e) ||
-                    cg_all_unified())
+                    cg_all_unified() > 0)
                         return _CGROUP_MASK_ALL;
         }
 
@@ -1260,7 +1259,10 @@ int unit_watch_cgroup(Unit *u) {
                 return 0;
 
         /* Only applies to the unified hierarchy */
-        if (!cg_unified(SYSTEMD_CGROUP_CONTROLLER))
+        r = cg_unified_controller(SYSTEMD_CGROUP_CONTROLLER);
+        if (r < 0)
+                return log_error_errno(r, "Failed to determine whether the name=systemd hierarchy is unified: %m");
+        if (r == 0)
                 return 0;
 
         /* Don't watch the root slice, it's pointless. */
@@ -1670,6 +1672,8 @@ static int unit_watch_pids_in_path(Unit *u, const char *path) {
 }
 
 int unit_watch_all_pids(Unit *u) {
+        int r;
+
         assert(u);
 
         /* Adds all PIDs from our cgroup to the set of PIDs we
@@ -1680,7 +1684,10 @@ int unit_watch_all_pids(Unit *u) {
         if (!u->cgroup_path)
                 return -ENOENT;
 
-        if (cg_unified(SYSTEMD_CGROUP_CONTROLLER)) /* On unified we can use proper notifications */
+        r = cg_unified_controller(SYSTEMD_CGROUP_CONTROLLER);
+        if (r < 0)
+                return r;
+        if (r > 0) /* On unified we can use proper notifications */
                 return 0;
 
         return unit_watch_pids_in_path(u, u->cgroup_path);
@@ -1753,7 +1760,7 @@ static int on_cgroup_inotify_event(sd_event_source *s, int fd, uint32_t revents,
 int manager_setup_cgroup(Manager *m) {
         _cleanup_free_ char *path = NULL;
         CGroupController c;
-        int r;
+        int r, all_unified;
         char *e;
 
         assert(m);
@@ -1794,18 +1801,26 @@ int manager_setup_cgroup(Manager *m) {
         if (r < 0)
                 return log_error_errno(r, "Couldn't determine if we are running in the unified hierarchy: %m");
 
-        if (cg_all_unified())
+        all_unified = cg_all_unified();
+        if (r < 0)
+                return log_error_errno(r, "Couldn't determine whether we are in all unified mode: %m");
+        if (r > 0)
                 log_debug("Unified cgroup hierarchy is located at %s.", path);
-        else if (cg_unified(SYSTEMD_CGROUP_CONTROLLER))
-                log_debug("Unified cgroup hierarchy is located at %s. Controllers are on legacy hierarchies.", path);
-        else
-                log_debug("Using cgroup controller " SYSTEMD_CGROUP_CONTROLLER_LEGACY ". File system hierarchy is at %s.", path);
+        else {
+                r = cg_unified_controller(SYSTEMD_CGROUP_CONTROLLER);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to determine whether systemd's own controller is in unified mode: %m");
+                if (r > 0)
+                        log_debug("Unified cgroup hierarchy is located at %s. Controllers are on legacy hierarchies.", path);
+                else
+                        log_debug("Using cgroup controller " SYSTEMD_CGROUP_CONTROLLER_LEGACY ". File system hierarchy is at %s.", path);
+        }
 
         if (!m->test_run) {
                 const char *scope_path;
 
                 /* 3. Install agent */
-                if (cg_unified(SYSTEMD_CGROUP_CONTROLLER)) {
+                if (cg_unified_controller(SYSTEMD_CGROUP_CONTROLLER) > 0) {
 
                         /* In the unified hierarchy we can get
                          * cgroup empty notifications via inotify. */
@@ -1865,7 +1880,7 @@ int manager_setup_cgroup(Manager *m) {
                         return log_error_errno(errno, "Failed to open pin file: %m");
 
                 /* 6.  Always enable hierarchical support if it exists... */
-                if (!cg_all_unified())
+                if (!all_unified)
                         (void) cg_set_attribute("memory", "/", "memory.use_hierarchy", "1");
         }
 
@@ -1991,10 +2006,13 @@ int unit_get_memory_current(Unit *u, uint64_t *ret) {
         if ((u->cgroup_realized_mask & CGROUP_MASK_MEMORY) == 0)
                 return -ENODATA;
 
-        if (!cg_all_unified())
-                r = cg_get_attribute("memory", u->cgroup_path, "memory.usage_in_bytes", &v);
-        else
+        r = cg_all_unified();
+        if (r < 0)
+                return r;
+        if (r > 0)
                 r = cg_get_attribute("memory", u->cgroup_path, "memory.current", &v);
+        else
+                r = cg_get_attribute("memory", u->cgroup_path, "memory.usage_in_bytes", &v);
         if (r == -ENOENT)
                 return -ENODATA;
         if (r < 0)
@@ -2036,7 +2054,10 @@ static int unit_get_cpu_usage_raw(Unit *u, nsec_t *ret) {
         if (!u->cgroup_path)
                 return -ENODATA;
 
-        if (cg_all_unified()) {
+        r = cg_all_unified();
+        if (r < 0)
+                return r;
+        if (r > 0) {
                 const char *keys[] = { "usage_usec", NULL };
                 _cleanup_free_ char *val = NULL;
                 uint64_t us;
diff --git a/src/core/manager.c b/src/core/manager.c
index ea80585329..cff38e28de 100644
--- a/src/core/manager.c
+++ b/src/core/manager.c
@@ -776,7 +776,10 @@ static int manager_setup_cgroups_agent(Manager *m) {
         if (!MANAGER_IS_SYSTEM(m))
                 return 0;
 
-        if (cg_unified(SYSTEMD_CGROUP_CONTROLLER)) /* We don't need this anymore on the unified hierarchy */
+        r = cg_unified_controller(SYSTEMD_CGROUP_CONTROLLER);
+        if (r < 0)
+                return log_error_errno(r, "Failed to determine whether unified cgroups hierarchy is used: %m");
+        if (r > 0) /* We don't need this anymore on the unified hierarchy */
                 return 0;
 
         if (m->cgroups_agent_fd < 0) {
diff --git a/src/core/scope.c b/src/core/scope.c
index 5e068a76d1..a1d5c1cfd5 100644
--- a/src/core/scope.c
+++ b/src/core/scope.c
@@ -475,7 +475,7 @@ static void scope_sigchld_event(Unit *u, pid_t pid, int code, int status) {
 
         /* If the PID set is empty now, then let's finish this off
            (On unified we use proper notifications) */
-        if (!cg_unified(SYSTEMD_CGROUP_CONTROLLER) && set_isempty(u->pids))
+        if (cg_unified_controller(SYSTEMD_CGROUP_CONTROLLER) == 0 && set_isempty(u->pids))
                 scope_notify_cgroup_empty_event(u);
 }
 
diff --git a/src/core/service.c b/src/core/service.c
index 0c2eb18f38..5581ec8b06 100644
--- a/src/core/service.c
+++ b/src/core/service.c
@@ -2938,7 +2938,7 @@ static void service_sigchld_event(Unit *u, pid_t pid, int code, int status) {
 
         /* If the PID set is empty now, then let's finish this off
            (On unified we use proper notifications) */
-        if (!cg_unified(SYSTEMD_CGROUP_CONTROLLER) && set_isempty(u->pids))
+        if (cg_unified_controller(SYSTEMD_CGROUP_CONTROLLER) == 0 && set_isempty(u->pids))
                 service_notify_cgroup_empty_event(u);
 }
 
diff --git a/src/core/unit.c b/src/core/unit.c
index b784277a96..174dd42819 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -3897,7 +3897,7 @@ int unit_kill_context(
                          * there we get proper events. Hence rely on
                          * them. */
 
-                        if (cg_unified(SYSTEMD_CGROUP_CONTROLLER) ||
+                        if (cg_unified_controller(SYSTEMD_CGROUP_CONTROLLER) > 0 ||
                             (detect_container() == 0 && !unit_cgroup_delegate(u)))
                                 wait_for_exit = true;
 
diff --git a/src/nspawn/nspawn-cgroup.c b/src/nspawn/nspawn-cgroup.c
index 4678a7e349..d749756437 100644
--- a/src/nspawn/nspawn-cgroup.c
+++ b/src/nspawn/nspawn-cgroup.c
@@ -78,9 +78,12 @@ int sync_cgroup(pid_t pid, CGroupUnified unified_requested, uid_t arg_uid_shift)
         char tree[] = "/tmp/unifiedXXXXXX", pid_string[DECIMAL_STR_MAX(pid) + 1];
         bool undo_mount = false;
         const char *fn;
-        int r;
+        int r, unified_controller;
 
-        if (cg_unified(SYSTEMD_CGROUP_CONTROLLER) == (unified_requested >= CGROUP_UNIFIED_SYSTEMD))
+        unified_controller = cg_unified_controller(SYSTEMD_CGROUP_CONTROLLER);
+        if (unified_controller < 0)
+                return log_error_errno(unified_controller, "Failed to determine whether the systemd hierarchy is unified: %m");
+        if ((unified_controller > 0) == (unified_requested >= CGROUP_UNIFIED_SYSTEMD))
                 return 0;
 
         /* When the host uses the legacy cgroup setup, but the
@@ -96,7 +99,7 @@ int sync_cgroup(pid_t pid, CGroupUnified unified_requested, uid_t arg_uid_shift)
         if (!mkdtemp(tree))
                 return log_error_errno(errno, "Failed to generate temporary mount point for unified hierarchy: %m");
 
-        if (cg_unified(SYSTEMD_CGROUP_CONTROLLER))
+        if (unified_controller > 0)
                 r = mount_verbose(LOG_ERR, "cgroup", tree, "cgroup",
                                   MS_NOSUID|MS_NOEXEC|MS_NODEV, "none,name=systemd,xattr");
         else
@@ -150,7 +153,10 @@ int create_subcgroup(pid_t pid, CGroupUnified unified_requested) {
         if (unified_requested == CGROUP_UNIFIED_NONE)
                 return 0;
 
-        if (!cg_unified(SYSTEMD_CGROUP_CONTROLLER))
+        r = cg_unified_controller(SYSTEMD_CGROUP_CONTROLLER);
+        if (r < 0)
+                return log_error_errno(r, "Failed to determine whether the systemd controller is unified: %m");
+        if (r == 0)
                 return 0;
 
         r = cg_mask_supported(&supported);
diff --git a/src/nspawn/nspawn-mount.c b/src/nspawn/nspawn-mount.c
index fca9d170d6..d276994120 100644
--- a/src/nspawn/nspawn-mount.c
+++ b/src/nspawn/nspawn-mount.c
@@ -991,7 +991,10 @@ static int mount_legacy_cgns_supported(
                         return r;
         }
 
-        if (cg_all_unified())
+        r = cg_all_unified();
+        if (r < 0)
+                return r;
+        if (r > 0)
                 goto skip_controllers;
 
         controllers = set_new(&string_hash_ops);
@@ -1094,7 +1097,10 @@ static int mount_legacy_cgns_unsupported(
                         return r;
         }
 
-        if (cg_all_unified())
+        r = cg_all_unified();
+        if (r < 0)
+                return r;
+        if (r > 0)
                 goto skip_controllers;
 
         controllers = set_new(&string_hash_ops);
diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index 00b084a42f..1fc0501c2e 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -333,7 +333,10 @@ static int detect_unified_cgroup_hierarchy(const char *directory) {
         }
 
         /* Otherwise inherit the default from the host system */
-        if (cg_all_unified()) {
+        r = cg_all_unified();
+        if (r < 0)
+                return log_error_errno(r, "Failed to determine whether we are in all unified mode.");
+        if (r > 0) {
                 /* Unified cgroup hierarchy support was added in 230. Unfortunately the detection
                  * routine only detects 231, so we'll have a false negative here for 230. */
                 r = systemd_installation_has_version(directory, 230);
@@ -343,7 +346,7 @@ static int detect_unified_cgroup_hierarchy(const char *directory) {
                         arg_unified_cgroup_hierarchy = CGROUP_UNIFIED_ALL;
                 else
                         arg_unified_cgroup_hierarchy = CGROUP_UNIFIED_NONE;
-        } else if (cg_unified(SYSTEMD_CGROUP_CONTROLLER)) {
+        } else if (cg_unified_controller(SYSTEMD_CGROUP_CONTROLLER) > 0) {
                 /* Mixed cgroup hierarchy support was added in 233 */
                 r = systemd_installation_has_version(directory, 233);
                 if (r < 0)