[RFC PATCH 3/9 v2] cgroup: change cgroup to css in rstat init and exit api

[JP Kobryn <inwardvessel@gmail.com>]

Change rstat init and exit API calls to accept a cgroup_subsys_state instead of
a cgroup.

Signed-off-by: JP Kobryn <inwardvessel@gmail.com>
---
 kernel/cgroup/cgroup-internal.h |  4 ++--
 kernel/cgroup/cgroup.c          | 16 ++++++++++------
 kernel/cgroup/rstat.c           |  6 ++++--
 3 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/kernel/cgroup/cgroup-internal.h b/kernel/cgroup/cgroup-internal.h
index c964dd7ff967..87d062baff90 100644
--- a/kernel/cgroup/cgroup-internal.h
+++ b/kernel/cgroup/cgroup-internal.h
@@ -269,8 +269,8 @@ int cgroup_task_count(const struct cgroup *cgrp);
 /*
  * rstat.c
  */
-int cgroup_rstat_init(struct cgroup *cgrp);
-void cgroup_rstat_exit(struct cgroup *cgrp);
+int cgroup_rstat_init(struct cgroup_subsys_state *css);
+void cgroup_rstat_exit(struct cgroup_subsys_state *css);
 void cgroup_rstat_boot(void);
 void cgroup_base_stat_cputime_show(struct seq_file *seq);
 
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index fdddd5ec5f3c..848e09f433c0 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -1358,7 +1358,7 @@ static void cgroup_destroy_root(struct cgroup_root *root)
 
 	cgroup_unlock();
 
-	cgroup_rstat_exit(cgrp);
+	cgroup_rstat_exit(&cgrp->self);
 	kernfs_destroy_root(root->kf_root);
 	cgroup_free_root(root);
 }
@@ -2132,7 +2132,7 @@ int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
 	if (ret)
 		goto destroy_root;
 
-	ret = cgroup_rstat_init(root_cgrp);
+	ret = cgroup_rstat_init(&root_cgrp->self);
 	if (ret)
 		goto destroy_root;
 
@@ -2174,7 +2174,7 @@ int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
 	goto out;
 
 exit_stats:
-	cgroup_rstat_exit(root_cgrp);
+	cgroup_rstat_exit(&root_cgrp->self);
 destroy_root:
 	kernfs_destroy_root(root->kf_root);
 	root->kf_root = NULL;
@@ -5435,7 +5435,7 @@ static void css_free_rwork_fn(struct work_struct *work)
 			cgroup_put(cgroup_parent(cgrp));
 			kernfs_put(cgrp->kn);
 			psi_cgroup_free(cgrp);
-			cgroup_rstat_exit(cgrp);
+			cgroup_rstat_exit(css);
 			kfree(cgrp);
 		} else {
 			/*
@@ -5686,7 +5686,11 @@ static struct cgroup *cgroup_create(struct cgroup *parent, const char *name,
 	if (ret)
 		goto out_free_cgrp;
 
-	ret = cgroup_rstat_init(cgrp);
+	/* init self cgroup early so css->cgroup is valid within cgroup_rstat_init()
+	 * note that this will go away in a subsequent patch in this series
+	 */
+	cgrp->self.cgroup = cgrp;
+	ret = cgroup_rstat_init(&cgrp->self);
 	if (ret)
 		goto out_cancel_ref;
 
@@ -5779,7 +5783,7 @@ static struct cgroup *cgroup_create(struct cgroup *parent, const char *name,
 out_kernfs_remove:
 	kernfs_remove(cgrp->kn);
 out_stat_exit:
-	cgroup_rstat_exit(cgrp);
+	cgroup_rstat_exit(&cgrp->self);
 out_cancel_ref:
 	percpu_ref_exit(&cgrp->self.refcnt);
 out_free_cgrp:
diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
index 1b7ef8690a09..01a5c185b02a 100644
--- a/kernel/cgroup/rstat.c
+++ b/kernel/cgroup/rstat.c
@@ -390,8 +390,9 @@ void cgroup_rstat_flush_release(struct cgroup_subsys_state *css)
 	__cgroup_rstat_unlock(css, -1);
 }
 
-int cgroup_rstat_init(struct cgroup *cgrp)
+int cgroup_rstat_init(struct cgroup_subsys_state *css)
 {
+	struct cgroup *cgrp = css->cgroup;
 	int cpu;
 
 	/* the root cgrp has rstat_cpu preallocated */
@@ -412,8 +413,9 @@ int cgroup_rstat_init(struct cgroup *cgrp)
 	return 0;
 }
 
-void cgroup_rstat_exit(struct cgroup *cgrp)
+void cgroup_rstat_exit(struct cgroup_subsys_state *css)
 {
+	struct cgroup *cgrp = css->cgroup;
 	int cpu;
 
 	cgroup_rstat_flush(&cgrp->self);
-- 
2.47.1