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Subject[PATCH 4/7] cgroup: combine css handling loops in cgroup_create()
Date
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>
---
kernel/cgroup.c | 25 +++++++------------------
1 file changed, 7 insertions(+), 18 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 30a2670..39e2295 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);
--
1.8.4.2


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