cgroup: change rstat function signatures from cgroup-based to css-based

This non-functional change serves as preparation for moving to
subsystem-based rstat trees. To simplify future commits, change the
signatures of existing cgroup-based rstat functions to become css-based and
rename them to reflect that.

Though the signatures have changed, the implementations have not. Within
these functions use the css->cgroup pointer to obtain the associated cgroup
and allow code to function the same just as it did before this patch. At
applicable call sites, pass the subsystem-specific css pointer as an
argument or pass a pointer to cgroup::self if not in subsystem context.

Note that cgroup_rstat_updated_list() and cgroup_rstat_push_children()
are not altered yet since there would be a larger amount of css to
cgroup conversions which may overcomplicate the code at this
intermediate phase.

Signed-off-by: JP Kobryn <inwardvessel@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 17 insertions, 13 deletions

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index d98994b106ed..c284df1efc9f 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -1362,7 +1362,7 @@ static void cgroup_destroy_root(struct cgroup_root *root)
 
 	cgroup_unlock();
 
-	cgroup_rstat_exit(cgrp);
+	css_rstat_exit(&cgrp->self);
 	kernfs_destroy_root(root->kf_root);
 	cgroup_free_root(root);
 }
@@ -2136,7 +2136,7 @@ int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
 	if (ret)
 		goto destroy_root;
 
-	ret = cgroup_rstat_init(root_cgrp);
+	ret = css_rstat_init(&root_cgrp->self);
 	if (ret)
 		goto destroy_root;
 
@@ -2178,7 +2178,7 @@ int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
 	goto out;
 
 exit_stats:
-	cgroup_rstat_exit(root_cgrp);
+	css_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);
+			css_rstat_exit(css);
 			kfree(cgrp);
 		} else {
 			/*
@@ -5465,7 +5465,7 @@ static void css_release_work_fn(struct work_struct *work)
 
 		/* css release path */
 		if (!list_empty(&css->rstat_css_node)) {
-			cgroup_rstat_flush(cgrp);
+			css_rstat_flush(css);
 			list_del_rcu(&css->rstat_css_node);
 		}
 
@@ -5493,7 +5493,7 @@ static void css_release_work_fn(struct work_struct *work)
 		/* cgroup release path */
 		TRACE_CGROUP_PATH(release, cgrp);
 
-		cgroup_rstat_flush(cgrp);
+		css_rstat_flush(css);
 
 		spin_lock_irq(&css_set_lock);
 		for (tcgrp = cgroup_parent(cgrp); tcgrp;
@@ -5686,17 +5686,13 @@ static struct cgroup *cgroup_create(struct cgroup *parent, const char *name,
 	if (ret)
 		goto out_free_cgrp;
 
-	ret = cgroup_rstat_init(cgrp);
-	if (ret)
-		goto out_cancel_ref;
-
 	/* create the directory */
 	kn = kernfs_create_dir_ns(parent->kn, name, mode,
 				  current_fsuid(), current_fsgid(),
 				  cgrp, NULL);
 	if (IS_ERR(kn)) {
 		ret = PTR_ERR(kn);
-		goto out_stat_exit;
+		goto out_cancel_ref;
 	}
 	cgrp->kn = kn;
 
@@ -5706,6 +5702,14 @@ static struct cgroup *cgroup_create(struct cgroup *parent, const char *name,
 	cgrp->root = root;
 	cgrp->level = level;
 
+	/*
+	 * Now that init_cgroup_housekeeping() has been called and cgrp->self
+	 * is setup, it is safe to perform rstat initialization on it.
+	 */
+	ret = css_rstat_init(&cgrp->self);
+	if (ret)
+		goto out_stat_exit;
+
 	ret = psi_cgroup_alloc(cgrp);
 	if (ret)
 		goto out_kernfs_remove;
@@ -5776,10 +5780,10 @@ static struct cgroup *cgroup_create(struct cgroup *parent, const char *name,
 
 out_psi_free:
 	psi_cgroup_free(cgrp);
+out_stat_exit:
+	css_rstat_exit(&cgrp->self);
 out_kernfs_remove:
 	kernfs_remove(cgrp->kn);
-out_stat_exit:
-	cgroup_rstat_exit(cgrp);
 out_cancel_ref:
 	percpu_ref_exit(&cgrp->self.refcnt);
 out_free_cgrp: