[PATCH 07/14] cgroup: reorganize css init / exit paths
From: Tejun Heo
Date: Thu Aug 08 2013 - 16:17:14 EST
css (cgroup_subsys_state) lifetime management is about to be
restructured. In prepartion, make the following mostly trivial
changes.
* init_cgroup_css() is renamed to init_css() so that it's consistent
with other css handling functions.
* alloc_css_id(), online_css() and offline_css() updated to take @css
instead of cgroups and subsys IDs.
* Merge two separate loops - one around percpu_ref_get() and the other
around online_css() - into one. This changes the order of
operations a bit without any consequences.
The first two changes don't make any functional differences and while
the last one does change behavior, it is of no consequence.
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
---
kernel/cgroup.c | 60 +++++++++++++++++++++++++--------------------------------
1 file changed, 26 insertions(+), 34 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index c271016..2a93bae 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -838,8 +838,7 @@ static struct backing_dev_info cgroup_backing_dev_info = {
.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
};
-static int alloc_css_id(struct cgroup_subsys *ss,
- struct cgroup *parent, struct cgroup *child);
+static int alloc_css_id(struct cgroup_subsys_state *child_css);
static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb)
{
@@ -4308,9 +4307,8 @@ static void css_release(struct percpu_ref *ref)
schedule_work(&css->destroy_work);
}
-static void init_cgroup_css(struct cgroup_subsys_state *css,
- struct cgroup_subsys *ss,
- struct cgroup *cgrp)
+static void init_css(struct cgroup_subsys_state *css, struct cgroup_subsys *ss,
+ struct cgroup *cgrp)
{
css->cgroup = cgrp;
css->ss = ss;
@@ -4327,9 +4325,9 @@ static void init_cgroup_css(struct cgroup_subsys_state *css,
}
/* invoke ->css_online() on a new CSS and mark it online if successful */
-static int online_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
+static int online_css(struct cgroup_subsys_state *css)
{
- struct cgroup_subsys_state *css = cgroup_css(cgrp, ss->subsys_id);
+ struct cgroup_subsys *ss = css->ss;
int ret = 0;
lockdep_assert_held(&cgroup_mutex);
@@ -4342,9 +4340,9 @@ static int online_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
}
/* if the CSS is online, invoke ->css_offline() on it and mark it offline */
-static void offline_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
+static void offline_css(struct cgroup_subsys_state *css)
{
- struct cgroup_subsys_state *css = cgroup_css(cgrp, ss->subsys_id);
+ struct cgroup_subsys *ss = css->ss;
lockdep_assert_held(&cgroup_mutex);
@@ -4442,10 +4440,10 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
goto err_free_all;
}
- init_cgroup_css(css, ss, cgrp);
+ init_css(css, ss, cgrp);
if (ss->use_id) {
- err = alloc_css_id(ss, parent, cgrp);
+ err = alloc_css_id(css);
if (err)
goto err_free_all;
}
@@ -4467,20 +4465,18 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);
root->number_of_cgroups++;
- /* each css holds a ref to the cgroup's dentry and the parent css */
+ /* hold a ref to the parent's dentry */
+ dget(parent->dentry);
+
for_each_root_subsys(root, ss) {
struct cgroup_subsys_state *css = cgroup_css(cgrp, ss->subsys_id);
+ /* each css holds a ref to the cgroup and the parent css */
dget(dentry);
percpu_ref_get(&css->parent->refcnt);
- }
- /* hold a ref to the parent's dentry */
- dget(parent->dentry);
-
- /* creation succeeded, notify subsystems */
- for_each_root_subsys(root, ss) {
- err = online_css(ss, cgrp);
+ /* creation succeeded, notify subsystems */
+ err = online_css(css);
if (err)
goto err_destroy;
@@ -4700,7 +4696,7 @@ static void cgroup_offline_fn(struct work_struct *work)
* initate destruction.
*/
for_each_root_subsys(cgrp->root, ss)
- offline_css(ss, cgrp);
+ offline_css(cgroup_css(cgrp, ss->subsys_id));
/*
* Put the css refs from cgroup_destroy_locked(). Each css holds
@@ -4778,7 +4774,7 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
css = ss->css_alloc(cgroup_css(cgroup_dummy_top, ss->subsys_id));
/* We don't handle early failures gracefully */
BUG_ON(IS_ERR(css));
- init_cgroup_css(css, ss, cgroup_dummy_top);
+ init_css(css, ss, cgroup_dummy_top);
/* Update the init_css_set to contain a subsys
* pointer to this state - since the subsystem is
@@ -4793,7 +4789,7 @@ 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(ss, cgroup_dummy_top));
+ BUG_ON(online_css(cgroup_css(cgroup_dummy_top, ss->subsys_id)));
mutex_unlock(&cgroup_mutex);
@@ -4866,8 +4862,8 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
ss->root = &cgroup_dummy_root;
/* our new subsystem will be attached to the dummy hierarchy. */
- init_cgroup_css(css, ss, cgroup_dummy_top);
- /* init_idr must be after init_cgroup_css because it sets css->id. */
+ init_css(css, ss, cgroup_dummy_top);
+ /* init_idr must be after init_css() because it sets css->id. */
if (ss->use_id) {
ret = cgroup_init_idr(ss, css);
if (ret)
@@ -4897,7 +4893,7 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
}
write_unlock(&css_set_lock);
- ret = online_css(ss, cgroup_dummy_top);
+ ret = online_css(cgroup_css(cgroup_dummy_top, ss->subsys_id));
if (ret)
goto err_unload;
@@ -4936,7 +4932,7 @@ void cgroup_unload_subsys(struct cgroup_subsys *ss)
mutex_lock(&cgroup_mutex);
- offline_css(ss, cgroup_dummy_top);
+ offline_css(cgroup_css(cgroup_dummy_top, ss->subsys_id));
if (ss->use_id)
idr_destroy(&ss->idr);
@@ -5588,20 +5584,16 @@ static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
return 0;
}
-static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
- struct cgroup *child)
+static int alloc_css_id(struct cgroup_subsys_state *child_css)
{
- int subsys_id, i, depth = 0;
- struct cgroup_subsys_state *parent_css, *child_css;
+ struct cgroup_subsys_state *parent_css = css_parent(child_css);
struct css_id *child_id, *parent_id;
+ int i, depth;
- subsys_id = ss->subsys_id;
- parent_css = cgroup_css(parent, subsys_id);
- child_css = cgroup_css(child, subsys_id);
parent_id = rcu_dereference_protected(parent_css->id, true);
depth = parent_id->depth + 1;
- child_id = get_new_cssid(ss, depth);
+ child_id = get_new_cssid(child_css->ss, depth);
if (IS_ERR(child_id))
return PTR_ERR(child_id);
--
1.8.3.1
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