[PATCH v6 02/12] cgroup/misc: Export APIs for SGX driver

[Haitao Huang <haitao.huang@xxxxxxxxxxxxxxx>]

From: Kristen Carlson Accardi <kristen@xxxxxxxxxxxxxxx>

Export misc_cg_root() so the SGX EPC cgroup can access and do extra
setup during initialization, e.g., set callbacks and private data
previously defined.

The SGX EPC cgroup will reclaim EPC pages when a 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(). Export
misc_cg_parent() to enable this walk.

Signed-off-by: Kristen Carlson Accardi <kristen@xxxxxxxxxxxxxxx>
Co-developed-by: Haitao Huang <haitao.huang@xxxxxxxxxxxxxxx>
Signed-off-by: Haitao Huang <haitao.huang@xxxxxxxxxxxxxxx>
---
V6:
- Make commit messages more concise and split the original patch into two(Kai)
---
 include/linux/misc_cgroup.h | 24 ++++++++++++++++++++++++
 kernel/cgroup/misc.c        | 21 ++++++++-------------
 2 files changed, 32 insertions(+), 13 deletions(-)

diff --git a/include/linux/misc_cgroup.h b/include/linux/misc_cgroup.h
index 5dc509c27c3d..2a3b1f8dc669 100644
--- a/include/linux/misc_cgroup.h
+++ b/include/linux/misc_cgroup.h
@@ -68,6 +68,7 @@ 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_try_charge(enum misc_res_type type, struct misc_cg *cg, u64 amount);
@@ -87,6 +88,20 @@ 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.
  *
@@ -111,6 +126,15 @@ 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 d971ede44ebf..fa464324ccf8 100644
--- a/kernel/cgroup/misc.c
+++ b/kernel/cgroup/misc.c
@@ -40,18 +40,13 @@ static struct misc_cg root_cg;
 static u64 misc_res_capacity[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;
 }
+EXPORT_SYMBOL_GPL(misc_cg_root);
 
 /**
  * valid_type() - Check if @type is valid or not.
@@ -150,7 +145,7 @@ 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);
@@ -163,12 +158,12 @@ int misc_cg_try_charge(enum misc_res_type type, struct misc_cg *cg, u64 amount)
 	return 0;
 
 err_charge:
-	for (j = i; j; j = parent_misc(j)) {
+	for (j = i; j; j = misc_cg_parent(j)) {
 		atomic64_inc(&j->res[type].events);
 		cgroup_file_notify(&j->events_file);
 	}
 
-	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;
@@ -190,7 +185,7 @@ 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);
-- 
2.25.1