nspawn: Clarify sync_cgroup(); tmp dirname, error message

sync_cgroup() can sync name=systemd->unified or unified->name=systemd,
depending on the setup.  However, the names of things, comments, and error
messages all assume (send the fals impression) that it only goes
name=systemd->unfied.

1 files changed, 15 insertions, 12 deletions

diff --git a/src/nspawn/nspawn-cgroup.c b/src/nspawn/nspawn-cgroup.c
index e939232b9e..df0044990a 100644
--- a/src/nspawn/nspawn-cgroup.c
+++ b/src/nspawn/nspawn-cgroup.c
@@ -80,7 +80,7 @@ static int chown_cgroup(pid_t pid, uid_t uid_shift) {
 
 static int sync_cgroup(pid_t pid, CGroupUnified outer_cgver, CGroupUnified inner_cgver, uid_t uid_shift) {
         _cleanup_free_ char *cgroup = NULL;
-        char tree[] = "/tmp/unifiedXXXXXX", pid_string[DECIMAL_STR_MAX(pid) + 1];
+        char mountpoint[] = "/tmp/containerXXXXXX", pid_string[DECIMAL_STR_MAX(pid) + 1];
         bool undo_mount = false;
         const char *fn;
         int r;
@@ -101,15 +101,15 @@ static int sync_cgroup(pid_t pid, CGroupUnified outer_cgver, CGroupUnified inner
         if (r < 0)
                 return log_error_errno(r, "Failed to get control group of " PID_FMT ": %m", pid);
 
-        /* In order to access the unified hierarchy we need to mount it */
-        if (!mkdtemp(tree))
-                return log_error_errno(errno, "Failed to generate temporary mount point for unified hierarchy: %m");
+        /* In order to access the container's hierarchy we need to mount it */
+        if (!mkdtemp(mountpoint))
+                return log_error_errno(errno, "Failed to generate temporary mount point for container hierarchy: %m");
 
         if (outer_cgver >= CGROUP_UNIFIED_SYSTEMD) {
-                r = mount_verbose(LOG_ERR, "cgroup", tree, "cgroup",
+                r = mount_verbose(LOG_ERR, "cgroup", mountpoint, "cgroup",
                                   MS_NOSUID|MS_NOEXEC|MS_NODEV, "none,name=systemd,xattr");
         else
-                r = mount_verbose(LOG_ERR, "cgroup", tree, "cgroup2",
+                r = mount_verbose(LOG_ERR, "cgroup", mountpoint, "cgroup2",
                                   MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL);
         if (r < 0)
                 goto finish;
@@ -119,10 +119,10 @@ static int sync_cgroup(pid_t pid, CGroupUnified outer_cgver, CGroupUnified inner
         /* If nspawn dies abruptly the cgroup hierarchy created below
          * its unit isn't cleaned up. So, let's remove it
          * https://github.com/systemd/systemd/pull/4223#issuecomment-252519810 */
-        fn = strjoina(tree, cgroup);
+        fn = strjoina(mountpoint, cgroup);
         (void) rm_rf(fn, REMOVE_ROOT|REMOVE_ONLY_DIRECTORIES);
 
-        fn = strjoina(tree, cgroup, "/cgroup.procs");
+        fn = strjoina(mountpoint, cgroup, "/cgroup.procs");
         (void) mkdir_parents(fn, 0755);
 
         sprintf(pid_string, PID_FMT, pid);
@@ -132,15 +132,15 @@ static int sync_cgroup(pid_t pid, CGroupUnified outer_cgver, CGroupUnified inner
                 goto finish;
         }
 
-        fn = strjoina(tree, cgroup);
+        fn = strjoina(mountpoint, cgroup);
         r = chown_cgroup_path(fn, uid_shift);
         if (r < 0)
                 log_error_errno(r, "Failed to chown() cgroup %s: %m", fn);
 finish:
         if (undo_mount)
-                (void) umount_verbose(tree);
+                (void) umount_verbose(mountpoint);
 
-        (void) rmdir(tree);
+        (void) rmdir(mountpoint);
         return r;
 }
 
@@ -230,7 +230,7 @@ static int get_v1_hierarchies(Set *subsystems) {
 
                 *e = 0;
 
-                if (STR_IN_SET(l, "", "name=systemd"))
+                if (streq(l, ""))
                         continue;
 
                 p = strdup(l);
@@ -342,6 +342,9 @@ static int mount_legacy_cgns_supported(
                 if (!hierarchy)
                         break;
 
+                if (streq(hierarchy, "name=systemd"))
+                        continue;
+
                 r = mount_legacy_cgroup_hierarchy("", hierarchy, hierarchy, inner_cgver, !userns);
                 if (r < 0)
                         return r;