cgroups: simplify and fix mounting on non-cgroup namespace aware kernels

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

diff --git a/src/lxc/cgroups/cgfsng.c b/src/lxc/cgroups/cgfsng.c
index 96072f79d22eb3232a5b50b9ffdda35c2fd5a52a..4c2eb48f3656090391ff8db0ce5ab08ab39fe978 100644 (file)
--- a/src/lxc/cgroups/cgfsng.c
+++ b/src/lxc/cgroups/cgfsng.c
@@ -1426,7 +1426,7 @@ static inline bool cg_mount_needs_subdirs(int cgroup_automount_type)
  * control/the/cg/path.
  */
 static int cg_legacy_mount_controllers(int cgroup_automount_type, struct hierarchy *h,
-                                      char *controllerpath, char *cgpath,
+                                      char *hierarchy_mnt, char *cgpath,
                                       const char *container_cgroup)
 {
        __do_free char *sourcepath = NULL;
@@ -1435,21 +1435,21 @@ static int cg_legacy_mount_controllers(int cgroup_automount_type, struct hierarc
 
        if ((cgroup_automount_type == LXC_AUTO_CGROUP_RO) ||
            (cgroup_automount_type == LXC_AUTO_CGROUP_MIXED)) {
-               ret = mount(controllerpath, controllerpath, "cgroup", MS_BIND, NULL);
+               ret = mount(hierarchy_mnt, hierarchy_mnt, "cgroup", MS_BIND, NULL);
                if (ret < 0)
                        return log_error_errno(-1, errno, "Failed to bind mount \"%s\" onto \"%s\"",
-                                              controllerpath, controllerpath);
+                                              hierarchy_mnt, hierarchy_mnt);
 
-               remount_flags = add_required_remount_flags(controllerpath,
-                                                          controllerpath,
+               remount_flags = add_required_remount_flags(hierarchy_mnt,
+                                                          hierarchy_mnt,
                                                           flags | MS_REMOUNT);
-               ret = mount(controllerpath, controllerpath, "cgroup",
+               ret = mount(hierarchy_mnt, hierarchy_mnt, "cgroup",
                            remount_flags | MS_REMOUNT | MS_BIND | MS_RDONLY,
                            NULL);
                if (ret < 0)
-                       return log_error_errno(-1, errno, "Failed to remount \"%s\" ro", controllerpath);
+                       return log_error_errno(-1, errno, "Failed to remount \"%s\" ro", hierarchy_mnt);
 
-               INFO("Remounted %s read-only", controllerpath);
+               INFO("Remounted %s read-only", hierarchy_mnt);
        }
 
        sourcepath = make_cgroup_path(h, h->container_base_path, container_cgroup, NULL);
@@ -1772,17 +1772,12 @@ __cgfsng_ops static bool cgfsng_mount(struct cgroup_ops *ops,
                                DEFAULT_CGROUP_MOUNTPOINT_RELATIVE);
 
        for (int i = 0; ops->hierarchies[i]; i++) {
-               __do_free char *controllerpath = NULL, *path2 = NULL;
+               __do_free char *hierarchy_mnt = NULL, *path2 = NULL;
                struct hierarchy *h = ops->hierarchies[i];
-               char *controller = h->mountpoint;
 
-               if (!controller)
-                       continue;
-               controller++;
-
-               ret = mkdirat(dfd_mnt_tmpfs, controller, 0000);
+               ret = mkdirat(dfd_mnt_tmpfs, h->mountpoint, 0000);
                if (ret < 0)
-                       return log_error_errno(false, errno, "Failed to create cgroup mountpoint %d(%s)", dfd_mnt_tmpfs, controller);
+                       return syserrno(false, "Failed to create cgroup mountpoint %d(%s)", dfd_mnt_tmpfs, h->mountpoint);
 
                if (in_cgroup_ns && wants_force_mount) {
                        /*
@@ -1790,7 +1785,8 @@ __cgfsng_ops static bool cgfsng_mount(struct cgroup_ops *ops,
                         * will not have CAP_SYS_ADMIN after it has started we
                         * need to mount the cgroups manually.
                         */
-                       ret = cgroupfs_mount(cgroup_automount_type, h, rootfs, dfd_mnt_tmpfs, controller);
+                       ret = cgroupfs_mount(cgroup_automount_type, h, rootfs,
+                                            dfd_mnt_tmpfs, h->mountpoint);
                        if (ret < 0)
                                return false;
 
@@ -1798,7 +1794,8 @@ __cgfsng_ops static bool cgfsng_mount(struct cgroup_ops *ops,
                }
 
                /* Here is where the ancient kernel section begins. */
-               ret = cgroupfs_bind_mount(cgroup_automount_type, h, rootfs, dfd_mnt_tmpfs, controller);
+               ret = cgroupfs_bind_mount(cgroup_automount_type, h, rootfs,
+                                         dfd_mnt_tmpfs, h->mountpoint);
                if (ret < 0)
                        return false;
 
@@ -1808,13 +1805,16 @@ __cgfsng_ops static bool cgfsng_mount(struct cgroup_ops *ops,
                if (!cgroup_root)
                        cgroup_root = must_make_path(rootfs_mnt, DEFAULT_CGROUP_MOUNTPOINT, NULL);
 
-               controllerpath = must_make_path(cgroup_root, controller, NULL);
-               path2 = must_make_path(controllerpath, h->container_base_path, ops->container_cgroup, NULL);
+               hierarchy_mnt = must_make_path(cgroup_root, h->mountpoint, NULL);
+               path2 = must_make_path(hierarchy_mnt, h->container_base_path,
+                                      ops->container_cgroup, NULL);
                ret = mkdir_p(path2, 0755);
                if (ret < 0 && (errno != EEXIST))
                        return false;
 
-               ret = cg_legacy_mount_controllers(cgroup_automount_type, h, controllerpath, path2, ops->container_cgroup);
+               ret = cg_legacy_mount_controllers(cgroup_automount_type, h,
+                                                 hierarchy_mnt, path2,
+                                                 ops->container_cgroup);
                if (ret < 0)
                        return false;
        }