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cgroup: implement cgroup->e_csets[]

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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: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
This commit is contained in:
Tejun Heo 2014-04-23 11:13:15 -04:00
parent aec3dfcb2e
commit 2d8f243a5e
2 changed files with 46 additions and 2 deletions
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18
include/linux/cgroup.h
View file

@ -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;
};

30
kernel/cgroup.c
View file

@ -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 @@ out_unlock:
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.