Commit d5c419b6 authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: move cgroup->sibling and ->children into cgroup_subsys_state 



We're moving towards using cgroup_subsys_states as the fundamental
structural blocks.  Let's move cgroup->sibling and ->children into
cgroup_subsys_state.  This is pure move without functional change and
only cgroup->self's fields are actually used.  Other csses will make
use of the fields later.

While at it, update init_and_link_css() so that it zeroes the whole
css before initializing it and remove explicit zeroing of ->flags.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent d51f39b0

include/linux/cgroup.h

+4 −7
Original line number Diff line number Diff line
@@ -68,6 +68,10 @@ struct cgroup_subsys_state { 
	/* PI: the parent css */

	struct cgroup_subsys_state *parent;



	/* siblings list anchored at the parent's ->children */

	struct list_head sibling;

	struct list_head children;



	/*

	 * PI: Subsys-unique ID.  0 is unused and root is always 1.  The

	 * matching css can be looked up using css_from_id().
@@ -171,13 +175,6 @@ struct cgroup { 
	 */

	int populated_cnt;



	/*

	 * We link our 'sibling' struct into our parent's 'children'.

	 * Our children link their 'sibling' into our 'children'.

	 */

	struct list_head sibling;	/* my parent's children */

	struct list_head children;	/* my children */



	struct kernfs_node *kn;		/* cgroup kernfs entry */

	struct kernfs_node *populated_kn; /* kn for "cgroup.subtree_populated" */

kernel/cgroup.c

+20 −18
Original line number Diff line number Diff line
@@ -378,7 +378,7 @@ static int notify_on_release(const struct cgroup *cgrp) 


/* iterate over child cgrps, lock should be held throughout iteration */

#define cgroup_for_each_live_child(child, cgrp)				\

	list_for_each_entry((child), &(cgrp)->children, sibling)	\

	list_for_each_entry((child), &(cgrp)->self.children, self.sibling) \

		if (({ lockdep_assert_held(&cgroup_mutex);		\

		       cgroup_is_dead(child); }))			\

			;						\
@@ -870,7 +870,7 @@ static void cgroup_destroy_root(struct cgroup_root *root) 
	mutex_lock(&cgroup_mutex);



	BUG_ON(atomic_read(&root->nr_cgrps));

	BUG_ON(!list_empty(&cgrp->children));

	BUG_ON(!list_empty(&cgrp->self.children));



	/* Rebind all subsystems back to the default hierarchy */

	rebind_subsystems(&cgrp_dfl_root, root->subsys_mask);
@@ -1432,7 +1432,7 @@ static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data) 
	}



	/* remounting is not allowed for populated hierarchies */

	if (!list_empty(&root->cgrp.children)) {

	if (!list_empty(&root->cgrp.self.children)) {

		ret = -EBUSY;

		goto out_unlock;

	}
@@ -1512,8 +1512,8 @@ static void init_cgroup_housekeeping(struct cgroup *cgrp) 
	struct cgroup_subsys *ss;

	int ssid;



	INIT_LIST_HEAD(&cgrp->sibling);

	INIT_LIST_HEAD(&cgrp->children);

	INIT_LIST_HEAD(&cgrp->self.sibling);

	INIT_LIST_HEAD(&cgrp->self.children);

	INIT_LIST_HEAD(&cgrp->cset_links);

	INIT_LIST_HEAD(&cgrp->release_list);

	INIT_LIST_HEAD(&cgrp->pidlists);
@@ -1612,7 +1612,7 @@ static int cgroup_setup_root(struct cgroup_root *root, unsigned int ss_mask) 
		link_css_set(&tmp_links, cset, root_cgrp);

	up_write(&css_set_rwsem);



	BUG_ON(!list_empty(&root_cgrp->children));

	BUG_ON(!list_empty(&root_cgrp->self.children));

	BUG_ON(atomic_read(&root->nr_cgrps) != 1);



	kernfs_activate(root_cgrp->kn);
@@ -3128,11 +3128,11 @@ css_next_child(struct cgroup_subsys_state *pos_css, 
	 * cgroup is removed or iteration and removal race.

	 */

	if (!pos) {

		next = list_entry_rcu(cgrp->children.next, struct cgroup, sibling);

		next = list_entry_rcu(cgrp->self.children.next, struct cgroup, self.sibling);

	} else if (likely(!cgroup_is_dead(pos))) {

		next = list_entry_rcu(pos->sibling.next, struct cgroup, sibling);

		next = list_entry_rcu(pos->self.sibling.next, struct cgroup, self.sibling);

	} else {

		list_for_each_entry_rcu(next, &cgrp->children, sibling)

		list_for_each_entry_rcu(next, &cgrp->self.children, self.sibling)

			if (next->serial_nr > pos->serial_nr)

				break;

	}
@@ -3142,12 +3142,12 @@ css_next_child(struct cgroup_subsys_state *pos_css, 
	 * the next sibling; however, it might have @ss disabled.  If so,

	 * fast-forward to the next enabled one.

	 */

	while (&next->sibling != &cgrp->children) {

	while (&next->self.sibling != &cgrp->self.children) {

		struct cgroup_subsys_state *next_css = cgroup_css(next, parent_css->ss);



		if (next_css)

			return next_css;

		next = list_entry_rcu(next->sibling.next, struct cgroup, sibling);

		next = list_entry_rcu(next->self.sibling.next, struct cgroup, self.sibling);

	}

	return NULL;

}
@@ -3283,7 +3283,7 @@ static bool cgroup_has_live_children(struct cgroup *cgrp) 
	struct cgroup *child;



	rcu_read_lock();

	list_for_each_entry_rcu(child, &cgrp->children, sibling) {

	list_for_each_entry_rcu(child, &cgrp->self.children, self.sibling) {

		if (!cgroup_is_dead(child)) {

			rcu_read_unlock();

			return true;
@@ -4144,7 +4144,7 @@ static void css_release_work_fn(struct work_struct *work) 
	} else {

		/* cgroup release path */

		mutex_lock(&cgroup_mutex);

		list_del_rcu(&cgrp->sibling);

		list_del_rcu(&cgrp->self.sibling);

		mutex_unlock(&cgroup_mutex);



		cgroup_idr_remove(&cgrp->root->cgroup_idr, cgrp->id);
@@ -4168,9 +4168,11 @@ static void init_and_link_css(struct cgroup_subsys_state *css, 
{

	cgroup_get(cgrp);



	memset(css, 0, sizeof(*css));

	css->cgroup = cgrp;

	css->ss = ss;

	css->flags = 0;

	INIT_LIST_HEAD(&css->sibling);

	INIT_LIST_HEAD(&css->children);



	if (cgroup_parent(cgrp)) {

		css->parent = cgroup_css(cgroup_parent(cgrp), ss);
@@ -4344,7 +4346,7 @@ static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, 
	cgrp->serial_nr = cgroup_serial_nr_next++;



	/* allocation complete, commit to creation */

	list_add_tail_rcu(&cgrp->sibling, &cgroup_parent(cgrp)->children);

	list_add_tail_rcu(&cgrp->self.sibling, &cgroup_parent(cgrp)->self.children);

	atomic_inc(&root->nr_cgrps);

	cgroup_get(parent);
@@ -4507,9 +4509,9 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) 
		return -EBUSY;



	/*

	 * Make sure there's no live children.  We can't test ->children

	 * emptiness as dead children linger on it while being destroyed;

	 * otherwise, "rmdir parent/child parent" may fail with -EBUSY.

	 * Make sure there's no live children.  We can't test emptiness of

	 * ->self.children as dead children linger on it while being

	 * drained; otherwise, "rmdir parent/child parent" may fail.

	 */

	if (cgroup_has_live_children(cgrp))

		return -EBUSY;

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