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: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 4eb2dd1..37d9662 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -425,6 +425,8 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 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 @@
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 @@
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.