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>
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@ -187,6 +187,15 @@ struct cgroup {
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*/
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struct list_head cset_links;
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/*
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* On the default hierarchy, a css_set for a cgroup with some
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* susbsys disabled will point to css's which are associated with
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* the closest ancestor which has the subsys enabled. The
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* following lists all css_sets which point to this cgroup's css
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* for the given subsystem.
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*/
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struct list_head e_csets[CGROUP_SUBSYS_COUNT];
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/*
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* Linked list running through all cgroups that can
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* potentially be reaped by the release agent. Protected by
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@ -369,6 +378,15 @@ struct css_set {
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struct cgroup *mg_src_cgrp;
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struct css_set *mg_dst_cset;
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/*
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* On the default hierarhcy, ->subsys[ssid] may point to a css
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* attached to an ancestor instead of the cgroup this css_set is
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* associated with. The following node is anchored at
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* ->subsys[ssid]->cgroup->e_csets[ssid] and provides a way to
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* iterate through all css's attached to a given cgroup.
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*/
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struct list_head e_cset_node[CGROUP_SUBSYS_COUNT];
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/* For RCU-protected deletion */
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struct rcu_head rcu_head;
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};
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@ -425,6 +425,8 @@ static unsigned long css_set_hash(struct cgroup_subsys_state *css[])
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static void put_css_set_locked(struct css_set *cset, bool taskexit)
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{
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struct cgrp_cset_link *link, *tmp_link;
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struct cgroup_subsys *ss;
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int ssid;
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lockdep_assert_held(&css_set_rwsem);
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@ -432,6 +434,8 @@ static void put_css_set_locked(struct css_set *cset, bool taskexit)
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return;
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/* This css_set is dead. unlink it and release cgroup refcounts */
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for_each_subsys(ss, ssid)
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list_del(&cset->e_cset_node[ssid]);
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hash_del(&cset->hlist);
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css_set_count--;
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@ -673,7 +677,9 @@ static struct css_set *find_css_set(struct css_set *old_cset,
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struct css_set *cset;
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struct list_head tmp_links;
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struct cgrp_cset_link *link;
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struct cgroup_subsys *ss;
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unsigned long key;
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int ssid;
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lockdep_assert_held(&cgroup_mutex);
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@ -724,10 +730,14 @@ static struct css_set *find_css_set(struct css_set *old_cset,
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css_set_count++;
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/* Add this cgroup group to the hash table */
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/* Add @cset to the hash table */
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key = css_set_hash(cset->subsys);
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hash_add(css_set_table, &cset->hlist, key);
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for_each_subsys(ss, ssid)
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list_add_tail(&cset->e_cset_node[ssid],
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&cset->subsys[ssid]->cgroup->e_csets[ssid]);
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up_write(&css_set_rwsem);
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return cset;
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@ -1028,7 +1038,7 @@ static int rebind_subsystems(struct cgroup_root *dst_root,
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unsigned long ss_mask)
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{
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struct cgroup_subsys *ss;
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int ssid, ret;
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int ssid, i, ret;
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lockdep_assert_held(&cgroup_tree_mutex);
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lockdep_assert_held(&cgroup_mutex);
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@ -1081,6 +1091,7 @@ static int rebind_subsystems(struct cgroup_root *dst_root,
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for_each_subsys(ss, ssid) {
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struct cgroup_root *src_root;
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struct cgroup_subsys_state *css;
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struct css_set *cset;
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if (!(ss_mask & (1 << ssid)))
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continue;
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@ -1095,6 +1106,12 @@ static int rebind_subsystems(struct cgroup_root *dst_root,
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ss->root = dst_root;
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css->cgroup = &dst_root->cgrp;
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down_write(&css_set_rwsem);
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hash_for_each(css_set_table, i, cset, hlist)
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list_move_tail(&cset->e_cset_node[ss->id],
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&dst_root->cgrp.e_csets[ss->id]);
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up_write(&css_set_rwsem);
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src_root->subsys_mask &= ~(1 << ssid);
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src_root->cgrp.child_subsys_mask &= ~(1 << ssid);
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@ -1417,6 +1434,9 @@ out_unlock:
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static void init_cgroup_housekeeping(struct cgroup *cgrp)
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{
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struct cgroup_subsys *ss;
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int ssid;
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atomic_set(&cgrp->refcnt, 1);
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INIT_LIST_HEAD(&cgrp->sibling);
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INIT_LIST_HEAD(&cgrp->children);
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@ -1425,6 +1445,9 @@ static void init_cgroup_housekeeping(struct cgroup *cgrp)
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INIT_LIST_HEAD(&cgrp->pidlists);
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mutex_init(&cgrp->pidlist_mutex);
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cgrp->dummy_css.cgroup = cgrp;
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for_each_subsys(ss, ssid)
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INIT_LIST_HEAD(&cgrp->e_csets[ssid]);
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}
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static void init_cgroup_root(struct cgroup_root *root,
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@ -4249,6 +4272,9 @@ int __init cgroup_init(void)
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if (!ss->early_init)
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cgroup_init_subsys(ss);
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list_add_tail(&init_css_set.e_cset_node[ssid],
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&cgrp_dfl_root.cgrp.e_csets[ssid]);
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/*
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* cftype registration needs kmalloc and can't be done
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* during early_init. Register base cftypes separately.
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