Currently, css (cgroup_subsys_state) lifetime is tied to that of the
associated cgroup. With the planned unified hierarchy, css's will be
dynamically created and destroyed within the lifetime of a cgroup. To
enable such usages, css's will be individually RCU protected instead
of being tied to the cgroup.
In preparation, this patch moves cgroup->subsys[] assignment from
init_css() to online_css(). As this means that a newly initialized
css should be remembered separately and that cgroup_css() returns NULL
between init and online, cgroup_create() is updated so that it stores
newly created css's in a local array css_ar[] and
cgroup_init/load_subsys() are updated to use local variable @css
instead of using cgroup_css(). This change also slightly simplifies
error path of cgroup_create().
While this patch changes when cgroup->subsys[] is initialized, this
change isn't visible to subsystems or userland.
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
---
kernel/cgroup.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 2a93bae..06ba664 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4321,7 +4321,6 @@ static void init_css(struct cgroup_subsys_state *css, struct cgroup_subsys *ss,
css->flags |= CSS_ROOT;
BUG_ON(cgroup_css(cgrp, ss->subsys_id));
- rcu_assign_pointer(cgrp->subsys[ss->subsys_id], css);
}
/* invoke ->css_online() on a new CSS and mark it online if successful */
@@ -4334,8 +4333,10 @@ static int online_css(struct cgroup_subsys_state *css)
if (ss->css_online)
ret = ss->css_online(css);
- if (!ret)
+ if (!ret) {
css->flags |= CSS_ONLINE;
+ rcu_assign_pointer(css->cgroup->subsys[ss->subsys_id], css);
+ }
return ret;
}
@@ -4366,6 +4367,7 @@ 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 *cgrp;
struct cgroup_name *name;
struct cgroupfs_root *root = parent->root;
@@ -4433,12 +4435,11 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
err = PTR_ERR(css);
goto err_free_all;
}
+ css_ar[ss->subsys_id] = css;
err = percpu_ref_init(&css->refcnt, css_release);
- if (err) {
- ss->css_free(css);
+ if (err)
goto err_free_all;
- }
init_css(css, ss, cgrp);
@@ -4469,7 +4470,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
dget(parent->dentry);
for_each_root_subsys(root, ss) {
- struct cgroup_subsys_state *css = cgroup_css(cgrp, ss->subsys_id);
+ struct cgroup_subsys_state *css = css_ar[ss->subsys_id];
/* each css holds a ref to the cgroup and the parent css */
dget(dentry);
@@ -4507,7 +4508,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
err_free_all:
for_each_root_subsys(root, ss) {
- struct cgroup_subsys_state *css = cgroup_css(cgrp, ss->subsys_id);
+ struct cgroup_subsys_state *css = css_ar[ss->subsys_id];
if (css) {
percpu_ref_cancel_init(&css->refcnt);
@@ -4789,7 +4790,7 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
* need to invoke fork callbacks here. */
BUG_ON(!list_empty(&init_task.tasks));
- BUG_ON(online_css(cgroup_css(cgroup_dummy_top, ss->subsys_id)));
+ BUG_ON(online_css(css));
mutex_unlock(&cgroup_mutex);
@@ -4893,7 +4894,7 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
}
write_unlock(&css_set_lock);
- ret = online_css(cgroup_css(cgroup_dummy_top, ss->subsys_id));
+ ret = online_css(css);
if (ret)
goto err_unload;
--
1.8.3.1
_______________________________________________
Containers mailing list
Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx
https://lists.linuxfoundation.org/mailman/listinfo/containers
