cgroup: combine css handling loops in cgroup_create()

Now that css operations in cgroup_create() are back-to-back, there
isn't much point in allocating css's in one loop and onlining them in
another.  Merge the two loops so that a css is allocated and onlined
on each iteration.

css_ar[] is no longer necessary and replaced with a single pointer.
This also simplifies the error handling path.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>

1 files changed, 7 insertions, 18 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 30a2670df3cf..39e2295466ec 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4084,7 +4084,7 @@ static void offline_css(struct cgroup_subsys_state *css)
 static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
                              umode_t mode)
 {
-        struct cgroup_subsys_state *css_ar[CGROUP_SUBSYS_COUNT] = { };
+        struct cgroup_subsys_state *css = NULL;
         struct cgroup *cgrp;
         struct cgroup_name *name;
         struct cgroupfs_root *root = parent->root;
@@ -4173,26 +4173,20 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
         if (err)
                 goto err_destroy;
 
+        /* let's create and online css's */
         for_each_root_subsys(root, ss) {
-                struct cgroup_subsys_state *css;
-
                 css = ss->css_alloc(cgroup_css(parent, ss));
                 if (IS_ERR(css)) {
                         err = PTR_ERR(css);
+                        css = NULL;
                         goto err_destroy;
                 }
-                css_ar[ss->subsys_id] = css;
 
                 err = percpu_ref_init(&css->refcnt, css_release);
                 if (err)
                         goto err_destroy;
 
                 init_css(css, ss, cgrp);
-        }
-
-        /* creation succeeded, notify subsystems */
-        for_each_root_subsys(root, ss) {
-                struct cgroup_subsys_state *css = css_ar[ss->subsys_id];
 
                 err = cgroup_populate_dir(cgrp, 1 << ss->subsys_id);
                 if (err)
@@ -4202,12 +4196,11 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
                 if (err)
                         goto err_destroy;
 
-                /* each css holds a ref to the cgroup's dentry and parent css */
                 dget(dentry);
                 css_get(css->parent);
 
                 /* mark it consumed for error path */
-                css_ar[ss->subsys_id] = NULL;
+                css = NULL;
 
                 if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
                     parent->parent) {
@@ -4237,13 +4230,9 @@ err_free_cgrp:
         return err;
 
 err_destroy:
-        for_each_root_subsys(root, ss) {
-                struct cgroup_subsys_state *css = css_ar[ss->subsys_id];
-
-                if (css) {
-                        percpu_ref_cancel_init(&css->refcnt);
-                        ss->css_free(css);
-                }
+        if (css) {
+                percpu_ref_cancel_init(&css->refcnt);
+                css->ss->css_free(css);
         }
         cgroup_destroy_locked(cgrp);
         mutex_unlock(&cgroup_mutex);