cgroup-util: Merge the unified_cache and unified_systemd_v232 caches

Conceptually, the addition of bool unified_systemd_v232 split
CGROUP_UNIFIED_SYSTEMD in to two separate values.  So, split it.

The "tricky" part is when to switch the old CGROUP_UNIFIED_SYSTEMD to
CGROUP_UNIFIED_SYSTEMD232 and when to switch it to
CGROUP_UNIFIED_SYSTEMD233.  All ">= CGROUP_UNIFIED_SYSTEMD" checks go to
232, since that preserves the existing behavior.

6 files changed, 14 insertions, 26 deletions

diff --git a/configure.ac b/configure.ac
index c7537aafc0..afbb4e8ae5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -645,7 +645,7 @@ AC_ARG_WITH(default-hierarchy,
 
 AS_CASE("$DEFAULT_HIERARCHY",
         [legacy], [mode=CGROUP_UNIFIED_NONE],
-        [hybrid], [mode=CGROUP_UNIFIED_SYSTEMD],
+        [hybrid], [mode=CGROUP_UNIFIED_SYSTEMD233],
         [unified], [mode=CGROUP_UNIFIED_ALL],
         AC_MSG_ERROR(Bad default hierarchy mode ${DEFAULT_HIERARCHY}))
 AC_DEFINE_UNQUOTED(DEFAULT_HIERARCHY, [$mode], [Default cgroup hierarchy])
diff --git a/meson.build b/meson.build
index 20b27c8600..1e1677ca7e 100644
--- a/meson.build
+++ b/meson.build
@@ -544,7 +544,7 @@ conf.set_quoted('DEFAULT_HIERARCHY_NAME', default_hierarchy,
 if default_hierarchy == 'legacy'
         conf.set('DEFAULT_HIERARCHY', 'CGROUP_UNIFIED_NONE')
 elif default_hierarchy == 'hybrid'
-        conf.set('DEFAULT_HIERARCHY', 'CGROUP_UNIFIED_SYSTEMD')
+        conf.set('DEFAULT_HIERARCHY', 'CGROUP_UNIFIED_SYSTEMD233')
 else
         conf.set('DEFAULT_HIERARCHY', 'CGROUP_UNIFIED_ALL')
 endif
diff --git a/src/basic/cgroup-util.c b/src/basic/cgroup-util.c
index f849df6d0e..5287d7867a 100644
--- a/src/basic/cgroup-util.c
+++ b/src/basic/cgroup-util.c
@@ -2382,17 +2382,6 @@ 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.
- *
- * 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_unified_update(void) {
 
         struct statfs fs;
@@ -2413,12 +2402,10 @@ static int cg_unified_update(void) {
         else if (F_TYPE_EQUAL(fs.f_type, TMPFS_MAGIC)) {
                 if (statfs("/sys/fs/cgroup/unified/", &fs) == 0 &&
                     F_TYPE_EQUAL(fs.f_type, CGROUP2_SUPER_MAGIC)) {
-                        unified_cache = CGROUP_UNIFIED_SYSTEMD;
-                        unified_systemd_v232 = false;
+                        unified_cache = CGROUP_UNIFIED_SYSTEMD233;
                 } else if (statfs("/sys/fs/cgroup/systemd/", &fs) == 0 &&
                            F_TYPE_EQUAL(fs.f_type, CGROUP2_SUPER_MAGIC)) {
-                        unified_cache = CGROUP_UNIFIED_SYSTEMD;
-                        unified_systemd_v232 = true;
+                        unified_cache = CGROUP_UNIFIED_SYSTEMD232;
                 } else {
                         if (statfs("/sys/fs/cgroup/systemd/", &fs) < 0)
                                 return -errno;
@@ -2465,7 +2452,7 @@ int cg_hybrid_unified(void) {
         if (r < 0)
                 return r;
 
-        return unified_cache == CGROUP_UNIFIED_SYSTEMD && !unified_systemd_v232;
+        return unified_cache == CGROUP_UNIFIED_SYSTEMD233;
 }
 
 int cg_unified_flush(void) {
@@ -2560,7 +2547,7 @@ bool cg_is_hybrid_wanted(void) {
         static thread_local int wanted = -1;
         int r;
         bool b;
-        const bool is_default = DEFAULT_HIERARCHY >= CGROUP_UNIFIED_SYSTEMD;
+        const bool is_default = DEFAULT_HIERARCHY >= CGROUP_UNIFIED_SYSTEMD232;
         /* We default to true if the default is "hybrid", obviously,
          * but also when the default is "unified", because if we get
          * called, it means that unified hierarchy was not mounted. */
diff --git a/src/basic/cgroup-util.h b/src/basic/cgroup-util.h
index c16a33723c..65821ece36 100644
--- a/src/basic/cgroup-util.h
+++ b/src/basic/cgroup-util.h
@@ -120,8 +120,9 @@ static inline bool CGROUP_BLKIO_WEIGHT_IS_OK(uint64_t x) {
 typedef enum CGroupUnified {
         CGROUP_UNIFIED_UNKNOWN = -1,
         CGROUP_UNIFIED_NONE = 0,        /* Both systemd and controllers on legacy */
-        CGROUP_UNIFIED_SYSTEMD = 1,     /* Only systemd on unified */
-        CGROUP_UNIFIED_ALL = 2,         /* Both systemd and controllers on unified */
+        CGROUP_UNIFIED_SYSTEMD232 = 1,  /* Only systemd on unified, as done by SD232 */
+        CGROUP_UNIFIED_SYSTEMD233 = 2,  /* Only systemd on unified, as done by SD233+ */
+        CGROUP_UNIFIED_ALL = 3,         /* Both systemd and controllers on unified */
 } CGroupUnified;
 
 /*
diff --git a/src/nspawn/nspawn-cgroup.c b/src/nspawn/nspawn-cgroup.c
index ad5f8eeb5b..600f7b9393 100644
--- a/src/nspawn/nspawn-cgroup.c
+++ b/src/nspawn/nspawn-cgroup.c
@@ -88,7 +88,7 @@ int sync_cgroup(pid_t pid, CGroupUnified inner_cgver, uid_t uid_shift) {
         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) == (inner_cgver >= CGROUP_UNIFIED_SYSTEMD))
+        if ((unified_controller > 0) == (inner_cgver >= CGROUP_UNIFIED_SYSTEMD232))
                 return 0;
 
         /* When the host uses the legacy cgroup setup, but the
@@ -373,7 +373,7 @@ static int mount_legacy_cgns_supported(
         }
 
 skip_controllers:
-        if (inner_cgver >= CGROUP_UNIFIED_SYSTEMD) {
+        if (inner_cgver >= CGROUP_UNIFIED_SYSTEMD232) {
                 r = mount_legacy_cgroup_hierarchy("", SYSTEMD_CGROUP_CONTROLLER_HYBRID, "unified", false);
                 if (r < 0)
                         return r;
@@ -486,7 +486,7 @@ static int mount_legacy_cgns_unsupported(
         }
 
 skip_controllers:
-        if (inner_cgver >= CGROUP_UNIFIED_SYSTEMD) {
+        if (inner_cgver >= CGROUP_UNIFIED_SYSTEMD232) {
                 r = mount_legacy_cgroup_hierarchy(dest, SYSTEMD_CGROUP_CONTROLLER_HYBRID, "unified", false);
                 if (r < 0)
                         return r;
@@ -579,7 +579,7 @@ int mount_systemd_cgroup_writable(
                 return mount_systemd_cgroup_writable_one(strjoina(dest, "/sys/fs/cgroup", own_cgroup_path),
                                                          prefix_roota(dest, "/sys/fs/cgroup"));
 
-        if (inner_cgver >= CGROUP_UNIFIED_SYSTEMD) {
+        if (inner_cgver >= CGROUP_UNIFIED_SYSTEMD232) {
                 r = mount_systemd_cgroup_writable_one(strjoina(dest, "/sys/fs/cgroup/unified", own_cgroup_path),
                                                       prefix_roota(dest, "/sys/fs/cgroup/unified"));
                 if (r < 0)
diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index 588bf2b2bf..3018110029 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -352,7 +352,7 @@ static int detect_unified_cgroup_hierarchy(const char *directory) {
                 if (r < 0)
                         return log_error_errno(r, "Failed to determine systemd version in container: %m");
                 if (r > 0)
-                        arg_unified_cgroup_hierarchy = CGROUP_UNIFIED_SYSTEMD;
+                        arg_unified_cgroup_hierarchy = CGROUP_UNIFIED_SYSTEMD233;
                 else
                         arg_unified_cgroup_hierarchy = CGROUP_UNIFIED_NONE;
         } else