cgroup2: use new fstype for unified hierarchy

Since Linux v4.4-rc1, __DEVEL__sane_behavior does not exist anymore and
is replaced by a new fstype "cgroup2".

With this patch, systemd no longer supports the old (unstable) way of
doing unified hierarchy with __DEVEL__sane_behavior and systemd now
requires Linux v4.4 for unified hierarchy.

Non-unified hierarchy is still the default and is unchanged by this
patch.

https://github.com/torvalds/linux/commit/67e9c74b8a873408c27ac9a8e4c1d1c8d72c93ff

5 files changed, 8 insertions, 4 deletions

diff --git a/src/basic/cgroup-util.c b/src/basic/cgroup-util.c
index 56c1fcaab9..5124b5bf93 100644
--- a/src/basic/cgroup-util.c
+++ b/src/basic/cgroup-util.c
@@ -2129,7 +2129,7 @@ int cg_unified(void) {
         if (statfs("/sys/fs/cgroup/", &fs) < 0)
                 return -errno;
 
-        if (F_TYPE_EQUAL(fs.f_type, CGROUP_SUPER_MAGIC))
+        if (F_TYPE_EQUAL(fs.f_type, CGROUP2_SUPER_MAGIC))
                 unified_cache = true;
         else if (F_TYPE_EQUAL(fs.f_type, TMPFS_MAGIC))
                 unified_cache = false;
diff --git a/src/basic/missing.h b/src/basic/missing.h
index 034e334e66..66cd5921ad 100644
--- a/src/basic/missing.h
+++ b/src/basic/missing.h
@@ -437,6 +437,10 @@ struct btrfs_ioctl_quota_ctl_args {
 #define CGROUP_SUPER_MAGIC 0x27e0eb
 #endif
 
+#ifndef CGROUP2_SUPER_MAGIC
+#define CGROUP2_SUPER_MAGIC 0x63677270
+#endif
+
 #ifndef TMPFS_MAGIC
 #define TMPFS_MAGIC 0x01021994
 #endif
diff --git a/src/core/mount-setup.c b/src/core/mount-setup.c
index de1a361cc4..32fe51c67e 100644
--- a/src/core/mount-setup.c
+++ b/src/core/mount-setup.c
@@ -94,7 +94,7 @@ static const MountPoint mount_table[] = {
 #endif
         { "tmpfs",       "/run",                      "tmpfs",      "mode=755",                MS_NOSUID|MS_NODEV|MS_STRICTATIME,
           NULL,          MNT_FATAL|MNT_IN_CONTAINER },
-        { "cgroup",      "/sys/fs/cgroup",            "cgroup",     "__DEVEL__sane_behavior",  MS_NOSUID|MS_NOEXEC|MS_NODEV,
+        { "cgroup",      "/sys/fs/cgroup",            "cgroup2",    NULL,                      MS_NOSUID|MS_NOEXEC|MS_NODEV,
           cg_is_unified_wanted, MNT_FATAL|MNT_IN_CONTAINER },
         { "tmpfs",       "/sys/fs/cgroup",            "tmpfs",      "mode=755",                MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME,
           cg_is_legacy_wanted, MNT_FATAL|MNT_IN_CONTAINER },
diff --git a/src/nspawn/nspawn-cgroup.c b/src/nspawn/nspawn-cgroup.c
index 9f9a4759d1..53a7ee7134 100644
--- a/src/nspawn/nspawn-cgroup.c
+++ b/src/nspawn/nspawn-cgroup.c
@@ -94,7 +94,7 @@ int sync_cgroup(pid_t pid, bool unified_requested) {
         if (unified)
                 r = mount("cgroup", tree, "cgroup", MS_NOSUID|MS_NOEXEC|MS_NODEV, "none,name=systemd,xattr");
         else
-                r = mount("cgroup", tree, "cgroup", MS_NOSUID|MS_NOEXEC|MS_NODEV, "__DEVEL__sane_behavior");
+                r = mount("cgroup", tree, "cgroup2", MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL);
         if (r < 0) {
                 r = log_error_errno(errno, "Failed to mount unified hierarchy: %m");
                 goto finish;
diff --git a/src/nspawn/nspawn-mount.c b/src/nspawn/nspawn-mount.c
index 70cca15278..64cb6b3ce3 100644
--- a/src/nspawn/nspawn-mount.c
+++ b/src/nspawn/nspawn-mount.c
@@ -750,7 +750,7 @@ static int mount_unified_cgroups(const char *dest) {
                 return -EINVAL;
         }
 
-        if (mount("cgroup", p, "cgroup", MS_NOSUID|MS_NOEXEC|MS_NODEV, "__DEVEL__sane_behavior") < 0)
+        if (mount("cgroup", p, "cgroup2", MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL) < 0)
                 return log_error_errno(errno, "Failed to mount unified cgroup hierarchy to %s: %m", p);
 
         return 0;