cgroups: stash fds for the controller mountpoint and base cgroup path

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

diff --git a/src/lxc/cgroups/cgfsng.c b/src/lxc/cgroups/cgfsng.c
index b237b75a94d71b0bc4b9b99219354c3c5f15caae..87343568885cf7020b94940be6c424ecde3be90d 100644 (file)
--- a/src/lxc/cgroups/cgfsng.c
+++ b/src/lxc/cgroups/cgfsng.c
@@ -696,6 +696,7 @@ static struct hierarchy *add_hierarchy(struct cgroup_ops *ops,
                                       char **clist, char *mountpoint,
                                       char *container_base_path, int type)
 {
+       __do_close int dfd_base = -EBADF, dfd_mnt = -EBADF;
        __do_free struct hierarchy *new = NULL;
        int newentry;
 
@@ -714,6 +715,16 @@ static struct hierarchy *add_hierarchy(struct cgroup_ops *ops,
        new->cgfd_limit                 = -EBADF;
        new->cgfd_mon                   = -EBADF;
 
+       dfd_mnt = open_at(-EBADF, mountpoint, PROTECT_OPATH_DIRECTORY,
+                         PROTECT_LOOKUP_ABSOLUTE_XDEV, 0);
+       if (dfd_mnt < 0)
+               return syserrno(NULL, "Failed to open %s", mountpoint);
+
+       dfd_base = open_at(dfd_mnt, container_base_path, PROTECT_OPATH_DIRECTORY,
+                          PROTECT_LOOKUP_BENEATH_XDEV, 0);
+       if (dfd_base < 0)
+               return syserrno(NULL, "Failed to open %d(%s)", dfd_base, container_base_path);
+
        TRACE("Adding cgroup hierarchy with mountpoint %s and base cgroup %s %s",
              mountpoint, container_base_path,
              clist ? "with controllers " : "without any controllers");
@@ -721,6 +732,8 @@ static struct hierarchy *add_hierarchy(struct cgroup_ops *ops,
                TRACE("%s", *it);
 
        newentry = append_null_to_list((void ***)&ops->hierarchies);
+       new->dfd_mnt = move_fd(dfd_mnt);
+       new->dfd_base = move_fd(dfd_base);
        (ops->hierarchies)[newentry] = new;
        return move_ptr(new);
 }

diff --git a/src/lxc/cgroups/cgroup.c b/src/lxc/cgroups/cgroup.c
index 9ba7a18608a6ea92ec30d6e2c5cb51eab16686bd..b83879b62b93362451627b970a2a050639361af8 100644 (file)
--- a/src/lxc/cgroups/cgroup.c
+++ b/src/lxc/cgroups/cgroup.c
@@ -92,6 +92,10 @@ void cgroup_exit(struct cgroup_ops *ops)
                        close((*it)->cgfd_con);
                if ((*it)->cgfd_mon >= 0)
                        close((*it)->cgfd_mon);
+               if ((*it)->dfd_mnt >= 0)
+                       close((*it)->dfd_mnt);
+               if ((*it)->dfd_base >= 0)
+                       close((*it)->dfd_base);
                free(*it);
        }
        free(ops->hierarchies);

diff --git a/src/lxc/cgroups/cgroup.h b/src/lxc/cgroups/cgroup.h
index f8060c06df126d00225544e06ac45d4c2de63040..2ec5f0a7ca1bcb417015891aec33d76398913ebf 100644 (file)
--- a/src/lxc/cgroups/cgroup.h
+++ b/src/lxc/cgroups/cgroup.h
@@ -103,6 +103,12 @@ struct hierarchy {
 
        /* File descriptor for the monitor's cgroup @monitor_full_path. */
        int cgfd_mon;
+
+       /* File descriptor for the controller's mountpoint @mountpoint. */
+       int dfd_mnt;
+
+       /* File descriptor for the controller's base cgroup path @container_base_path. */
+       int dfd_base;
 };
 
 struct cgroup_ops {