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>

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 30a2670df3cfead079b1b7fbf45413e8bbb1a72e..39e2295466eca443f3a9bea020bb072baeb0cdae 100644 (file)
--- 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);