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Commit 2d8f243a authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: implement cgroup->e_csets[] 



On the default unified hierarchy, a cgroup may be associated with
csses of its ancestors, which means that a css of a given cgroup may
be associated with css_sets of descendant cgroups.  This means that we
can't walk all tasks associated with a css by iterating the css_sets
associated with the cgroup as there are css_sets which are pointing to
the css but linked on the descendants.

This patch adds per-subsystem list heads cgroup->e_csets[].  Any
css_set which is pointing to a css is linked to
css->cgroup->e_csets[$SUBSYS_ID] through
css_set->e_cset_node[$SUBSYS_ID].  The lists are protected by
css_set_rwsem and will allow us to walk all css_sets associated with a
given css so that we can find out all associated tasks.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent aec3dfcb

include/linux/cgroup.h

+18 −0
Original line number Diff line number Diff line
@@ -187,6 +187,15 @@ struct cgroup { 
	 */

	struct list_head cset_links;



	/*

	 * On the default hierarchy, a css_set for a cgroup with some

	 * susbsys disabled will point to css's which are associated with

	 * the closest ancestor which has the subsys enabled.  The

	 * following lists all css_sets which point to this cgroup's css

	 * for the given subsystem.

	 */

	struct list_head e_csets[CGROUP_SUBSYS_COUNT];



	/*

	 * Linked list running through all cgroups that can

	 * potentially be reaped by the release agent. Protected by
@@ -369,6 +378,15 @@ struct css_set { 
	struct cgroup *mg_src_cgrp;

	struct css_set *mg_dst_cset;



	/*

	 * On the default hierarhcy, ->subsys[ssid] may point to a css

	 * attached to an ancestor instead of the cgroup this css_set is

	 * associated with.  The following node is anchored at

	 * ->subsys[ssid]->cgroup->e_csets[ssid] and provides a way to

	 * iterate through all css's attached to a given cgroup.

	 */

	struct list_head e_cset_node[CGROUP_SUBSYS_COUNT];



	/* For RCU-protected deletion */

	struct rcu_head rcu_head;

};

kernel/cgroup.c

+28 −2
Original line number Diff line number Diff line
@@ -425,6 +425,8 @@ static unsigned long css_set_hash(struct cgroup_subsys_state *css[]) 
static void put_css_set_locked(struct css_set *cset, bool taskexit)

{

	struct cgrp_cset_link *link, *tmp_link;

	struct cgroup_subsys *ss;

	int ssid;



	lockdep_assert_held(&css_set_rwsem);
@@ -432,6 +434,8 @@ static void put_css_set_locked(struct css_set *cset, bool taskexit) 
		return;



	/* This css_set is dead. unlink it and release cgroup refcounts */

	for_each_subsys(ss, ssid)

		list_del(&cset->e_cset_node[ssid]);

	hash_del(&cset->hlist);

	css_set_count--;
@@ -673,7 +677,9 @@ static struct css_set *find_css_set(struct css_set *old_cset, 
	struct css_set *cset;

	struct list_head tmp_links;

	struct cgrp_cset_link *link;

	struct cgroup_subsys *ss;

	unsigned long key;

	int ssid;



	lockdep_assert_held(&cgroup_mutex);
@@ -724,10 +730,14 @@ static struct css_set *find_css_set(struct css_set *old_cset, 


	css_set_count++;



	/* Add this cgroup group to the hash table */

	/* Add @cset to the hash table */

	key = css_set_hash(cset->subsys);

	hash_add(css_set_table, &cset->hlist, key);



	for_each_subsys(ss, ssid)

		list_add_tail(&cset->e_cset_node[ssid],

			      &cset->subsys[ssid]->cgroup->e_csets[ssid]);



	up_write(&css_set_rwsem);



	return cset;
@@ -1028,7 +1038,7 @@ static int rebind_subsystems(struct cgroup_root *dst_root, 
			     unsigned long ss_mask)

{

	struct cgroup_subsys *ss;

	int ssid, ret;

	int ssid, i, ret;



	lockdep_assert_held(&cgroup_tree_mutex);

	lockdep_assert_held(&cgroup_mutex);
@@ -1081,6 +1091,7 @@ static int rebind_subsystems(struct cgroup_root *dst_root, 
	for_each_subsys(ss, ssid) {

		struct cgroup_root *src_root;

		struct cgroup_subsys_state *css;

		struct css_set *cset;



		if (!(ss_mask & (1 << ssid)))

			continue;
@@ -1095,6 +1106,12 @@ static int rebind_subsystems(struct cgroup_root *dst_root, 
		ss->root = dst_root;

		css->cgroup = &dst_root->cgrp;



		down_write(&css_set_rwsem);

		hash_for_each(css_set_table, i, cset, hlist)

			list_move_tail(&cset->e_cset_node[ss->id],

				       &dst_root->cgrp.e_csets[ss->id]);

		up_write(&css_set_rwsem);



		src_root->subsys_mask &= ~(1 << ssid);

		src_root->cgrp.child_subsys_mask &= ~(1 << ssid);
@@ -1417,6 +1434,9 @@ static void cgroup_enable_task_cg_lists(void) 


static void init_cgroup_housekeeping(struct cgroup *cgrp)

{

	struct cgroup_subsys *ss;

	int ssid;



	atomic_set(&cgrp->refcnt, 1);

	INIT_LIST_HEAD(&cgrp->sibling);

	INIT_LIST_HEAD(&cgrp->children);
@@ -1425,6 +1445,9 @@ static void init_cgroup_housekeeping(struct cgroup *cgrp) 
	INIT_LIST_HEAD(&cgrp->pidlists);

	mutex_init(&cgrp->pidlist_mutex);

	cgrp->dummy_css.cgroup = cgrp;



	for_each_subsys(ss, ssid)

		INIT_LIST_HEAD(&cgrp->e_csets[ssid]);

}



static void init_cgroup_root(struct cgroup_root *root,
@@ -4249,6 +4272,9 @@ int __init cgroup_init(void) 
		if (!ss->early_init)

			cgroup_init_subsys(ss);



		list_add_tail(&init_css_set.e_cset_node[ssid],

			      &cgrp_dfl_root.cgrp.e_csets[ssid]);



		/*

		 * cftype registration needs kmalloc and can't be done

		 * during early_init.  Register base cftypes separately.