[RFC,4/9] cgroup: Export task_cgroup_from_root() and cgroup_mutex for drivers

Commit Message

Matt Roper Jan. 20, 2018, 1:51 a.m. UTC

Drivers that handle processes on a per-cgroup basis need to be able to lookup
the cgroup that a process belongs to.

Cc: Tejun Heo <[e-mail]>
Cc: [e-mail]
Signed-off-by: Matt Roper <[e-mail]>
---
 include/linux/cgroup.h          | 5 ++++-
 kernel/cgroup/cgroup-internal.h | 3 ---
 kernel/cgroup/cgroup.c          | 8 +++++---
 3 files changed, 9 insertions(+), 7 deletions(-)

Patch

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 1c1758ac1a97..1b93fb018bfc 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -103,6 +103,8 @@  struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
 
 struct cgroup *cgroup_get_from_path(const char *path);
 struct cgroup *cgroup_get_from_fd(int fd);
+struct cgroup *task_cgroup_from_root(struct task_struct *task,
+				     struct cgroup_root *root);
 
 int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
 int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
@@ -432,7 +434,6 @@  static inline void cgroup_put(struct cgroup *cgrp)
  * as locks used during the cgroup_subsys::attach() methods.
  */
 #ifdef CONFIG_PROVE_RCU
-extern struct mutex cgroup_mutex;
 extern spinlock_t css_set_lock;
 #define task_css_set_check(task, __c)					\
 	rcu_dereference_check((task)->cgroups,				\
@@ -444,6 +445,8 @@  extern spinlock_t css_set_lock;
 	rcu_dereference((task)->cgroups)
 #endif
 
+extern struct mutex cgroup_mutex;
+
 /**
  * task_css_check - obtain css for (task, subsys) w/ extra access conds
  * @task: the target task
diff --git a/kernel/cgroup/cgroup-internal.h b/kernel/cgroup/cgroup-internal.h
index 7338083ee3bc..5471f8fe8c2d 100644
--- a/kernel/cgroup/cgroup-internal.h
+++ b/kernel/cgroup/cgroup-internal.h
@@ -99,7 +99,6 @@  struct cgroup_sb_opts {
 	bool none;
 };
 
-extern struct mutex cgroup_mutex;
 extern spinlock_t css_set_lock;
 extern struct cgroup_subsys *cgroup_subsys[];
 extern struct list_head cgroup_roots;
@@ -160,8 +159,6 @@  bool cgroup_is_thread_root(struct cgroup *cgrp);
 bool cgroup_is_threaded(struct cgroup *cgrp);
 
 struct cgroup_root *cgroup_root_from_kf(struct kernfs_root *kf_root);
-struct cgroup *task_cgroup_from_root(struct task_struct *task,
-				     struct cgroup_root *root);
 struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn, bool drain_offline);
 void cgroup_kn_unlock(struct kernfs_node *kn);
 int cgroup_path_ns_locked(struct cgroup *cgrp, char *buf, size_t buflen,
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 6069191653f8..0a0093a36a7f 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -69,8 +69,9 @@ 
  * css_set_lock protects task->cgroups pointer, the list of css_set
  * objects, and the chain of tasks off each css_set.
  *
- * These locks are exported if CONFIG_PROVE_RCU so that accessors in
- * cgroup.h can use them for lockdep annotations.
+ * cgroup_mutex is always exported so that it may be taken by non-controller
+ * drivers.  css_set_lock is exported if CONFIG_PROVE_RCU so that accessors in
+ * cgroup.h can use it for lockdep annotations.
  */
 DEFINE_MUTEX(cgroup_mutex);
 DEFINE_SPINLOCK(css_set_lock);
@@ -84,8 +85,8 @@  DEFINE_SPINLOCK(css_set_lock);
 BLOCKING_NOTIFIER_HEAD(cgroup_destroy_notifier_list);
 EXPORT_SYMBOL_GPL(cgroup_destroy_notifier_list);
 
-#ifdef CONFIG_PROVE_RCU
 EXPORT_SYMBOL_GPL(cgroup_mutex);
+#ifdef CONFIG_PROVE_RCU
 EXPORT_SYMBOL_GPL(css_set_lock);
 #endif
 
@@ -1367,6 +1368,7 @@  struct cgroup *task_cgroup_from_root(struct task_struct *task,
 	 */
 	return cset_cgroup_from_root(task_css_set(task), root);
 }
+EXPORT_SYMBOL(task_cgroup_from_root);
 
 /*
  * A task must hold cgroup_mutex to modify cgroups.