From: Kristen Carlson Accardi <kristen@linux.intel.com>

The SGX EPC cgroup will reclaim EPC pages when usage in a cgroup reaches
its or ancestor's limit. This requires a walk from the current cgroup up
to the root similar to misc_cg_try_charge(). Expose misc_cg_parent() to
enable this walk.

The SGX driver also needs start a global level reclamation from the
root. Expose misc_cg_root() for the SGX driver to access.

Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
Co-developed-by: Haitao Huang <haitao.huang@linux.intel.com>
Signed-off-by: Haitao Huang <haitao.huang@linux.intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Reviewed-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Tested-by: Jarkko Sakkinen <jarkko@kernel.org>
---
V17:
- Remove EXPORT_SYMBOL_GPL as these are currently used by the builtin
  SGX driver only. (Kai)

V6:
- Make commit messages more concise and split the original patch into two(Kai)
---
 include/linux/misc_cgroup.h | 24 ++++++++++++++++++++++++
 kernel/cgroup/misc.c        | 20 +++++++-------------
 2 files changed, 31 insertions(+), 13 deletions(-)

diff --git a/include/linux/misc_cgroup.h b/include/linux/misc_cgroup.h
index e5159770a68e..75c711333ad4 100644
--- a/include/linux/misc_cgroup.h
+++ b/include/linux/misc_cgroup.h
@@ -70,6 +70,7 @@ struct misc_cg {
 	struct misc_res res[MISC_CG_RES_TYPES];
 };
 
+struct misc_cg *misc_cg_root(void);
 u64 misc_cg_res_total_usage(enum misc_res_type type);
 int misc_cg_set_capacity(enum misc_res_type type, u64 capacity);
 int misc_cg_set_ops(enum misc_res_type type, const struct misc_res_ops *ops);
@@ -90,6 +91,20 @@ static inline struct misc_cg *css_misc(struct cgroup_subsys_state *css)
 	return css ? container_of(css, struct misc_cg, css) : NULL;
 }
 
+/**
+ * misc_cg_parent() - Get the parent of the passed misc cgroup.
+ * @cgroup: cgroup whose parent needs to be fetched.
+ *
+ * Context: Any context.
+ * Return:
+ * * struct misc_cg* - Parent of the @cgroup.
+ * * %NULL - If @cgroup is null or the passed cgroup does not have a parent.
+ */
+static inline struct misc_cg *misc_cg_parent(struct misc_cg *cgroup)
+{
+	return cgroup ? css_misc(cgroup->css.parent) : NULL;
+}
+
 /*
  * get_current_misc_cg() - Find and get the misc cgroup of the current task.
  *
@@ -114,6 +129,15 @@ static inline void put_misc_cg(struct misc_cg *cg)
 }
 
 #else /* !CONFIG_CGROUP_MISC */
+static inline struct misc_cg *misc_cg_root(void)
+{
+	return NULL;
+}
+
+static inline struct misc_cg *misc_cg_parent(struct misc_cg *cg)
+{
+	return NULL;
+}
 
 static inline u64 misc_cg_res_total_usage(enum misc_res_type type)
 {
diff --git a/kernel/cgroup/misc.c b/kernel/cgroup/misc.c
index b06343ab9651..757b534bec5f 100644
--- a/kernel/cgroup/misc.c
+++ b/kernel/cgroup/misc.c
@@ -43,17 +43,11 @@ static u64 misc_res_capacity[MISC_CG_RES_TYPES];
 static const struct misc_res_ops *misc_res_ops[MISC_CG_RES_TYPES];
 
 /**
- * parent_misc() - Get the parent of the passed misc cgroup.
- * @cgroup: cgroup whose parent needs to be fetched.
- *
- * Context: Any context.
- * Return:
- * * struct misc_cg* - Parent of the @cgroup.
- * * %NULL - If @cgroup is null or the passed cgroup does not have a parent.
+ * misc_cg_root() - Return the root misc cgroup.
  */
-static struct misc_cg *parent_misc(struct misc_cg *cgroup)
+struct misc_cg *misc_cg_root(void)
 {
-	return cgroup ? css_misc(cgroup->css.parent) : NULL;
+	return &root_cg;
 }
 
 /**
@@ -176,7 +170,7 @@ static void misc_cg_event(enum misc_res_type type, struct misc_cg *cg)
 	atomic64_inc(&cg->res[type].events_local);
 	cgroup_file_notify(&cg->events_local_file);
 
-	for (; parent_misc(cg); cg = parent_misc(cg)) {
+	for (; misc_cg_parent(cg); cg = misc_cg_parent(cg)) {
 		atomic64_inc(&cg->res[type].events);
 		cgroup_file_notify(&cg->events_file);
 	}
@@ -211,7 +205,7 @@ int misc_cg_try_charge(enum misc_res_type type, struct misc_cg *cg, u64 amount)
 	if (!amount)
 		return 0;
 
-	for (i = cg; i; i = parent_misc(i)) {
+	for (i = cg; i; i = misc_cg_parent(i)) {
 		res = &i->res[type];
 
 		new_usage = atomic64_add_return(amount, &res->usage);
@@ -227,7 +221,7 @@ int misc_cg_try_charge(enum misc_res_type type, struct misc_cg *cg, u64 amount)
 err_charge:
 	misc_cg_event(type, i);
 
-	for (j = cg; j != i; j = parent_misc(j))
+	for (j = cg; j != i; j = misc_cg_parent(j))
 		misc_cg_cancel_charge(type, j, amount);
 	misc_cg_cancel_charge(type, i, amount);
 	return ret;
@@ -249,7 +243,7 @@ void misc_cg_uncharge(enum misc_res_type type, struct misc_cg *cg, u64 amount)
 	if (!(amount && valid_type(type) && cg))
 		return;
 
-	for (i = cg; i; i = parent_misc(i))
+	for (i = cg; i; i = misc_cg_parent(i))
 		misc_cg_cancel_charge(type, i, amount);
 }
 EXPORT_SYMBOL_GPL(misc_cg_uncharge);
-- 
2.43.0