cgroup: remove cgroup->parent
cgroup->parent is redundant as cgroup->self.parent can also be used to
determine the parent cgroup and we're moving towards using
cgroup_subsys_states as the fundamental structural blocks. This patch
introduces cgroup_parent() which follows cgroup->self.parent and
removes cgroup->parent.
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 929bbbc5..8c67a73 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -218,6 +218,15 @@
spin_unlock_bh(&cgroup_idr_lock);
}
+static struct cgroup *cgroup_parent(struct cgroup *cgrp)
+{
+ struct cgroup_subsys_state *parent_css = cgrp->self.parent;
+
+ if (parent_css)
+ return container_of(parent_css, struct cgroup, self);
+ return NULL;
+}
+
/**
* cgroup_css - obtain a cgroup's css for the specified subsystem
* @cgrp: the cgroup of interest
@@ -260,9 +269,9 @@
if (!(cgrp->root->subsys_mask & (1 << ss->id)))
return NULL;
- while (cgrp->parent &&
- !(cgrp->parent->child_subsys_mask & (1 << ss->id)))
- cgrp = cgrp->parent;
+ while (cgroup_parent(cgrp) &&
+ !(cgroup_parent(cgrp)->child_subsys_mask & (1 << ss->id)))
+ cgrp = cgroup_parent(cgrp);
return cgroup_css(cgrp, ss);
}
@@ -307,7 +316,7 @@
while (cgrp) {
if (cgrp == ancestor)
return true;
- cgrp = cgrp->parent;
+ cgrp = cgroup_parent(cgrp);
}
return false;
}
@@ -454,7 +463,7 @@
if (cgrp->populated_kn)
kernfs_notify(cgrp->populated_kn);
- cgrp = cgrp->parent;
+ cgrp = cgroup_parent(cgrp);
} while (cgrp);
}
@@ -2018,7 +2027,7 @@
* Except for the root, child_subsys_mask must be zero for a cgroup
* with tasks so that child cgroups don't compete against tasks.
*/
- if (dst_cgrp && cgroup_on_dfl(dst_cgrp) && dst_cgrp->parent &&
+ if (dst_cgrp && cgroup_on_dfl(dst_cgrp) && cgroup_parent(dst_cgrp) &&
dst_cgrp->child_subsys_mask)
return -EBUSY;
@@ -2427,7 +2436,7 @@
{
struct cgroup *cgrp = seq_css(seq)->cgroup;
- cgroup_print_ss_mask(seq, cgrp->parent->child_subsys_mask);
+ cgroup_print_ss_mask(seq, cgroup_parent(cgrp)->child_subsys_mask);
return 0;
}
@@ -2610,8 +2619,8 @@
/* unavailable or not enabled on the parent? */
if (!(cgrp_dfl_root.subsys_mask & (1 << ssid)) ||
- (cgrp->parent &&
- !(cgrp->parent->child_subsys_mask & (1 << ssid)))) {
+ (cgroup_parent(cgrp) &&
+ !(cgroup_parent(cgrp)->child_subsys_mask & (1 << ssid)))) {
ret = -ENOENT;
goto out_unlock;
}
@@ -2640,7 +2649,7 @@
* Except for the root, child_subsys_mask must be zero for a cgroup
* with tasks so that child cgroups don't compete against tasks.
*/
- if (enable && cgrp->parent && !list_empty(&cgrp->cset_links)) {
+ if (enable && cgroup_parent(cgrp) && !list_empty(&cgrp->cset_links)) {
ret = -EBUSY;
goto out_unlock;
}
@@ -2898,9 +2907,9 @@
continue;
if ((cft->flags & CFTYPE_INSANE) && cgroup_sane_behavior(cgrp))
continue;
- if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
+ if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgroup_parent(cgrp))
continue;
- if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent)
+ if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgroup_parent(cgrp))
continue;
if (is_add) {
@@ -4092,14 +4101,14 @@
atomic_dec(&cgrp->root->nr_cgrps);
cgroup_pidlist_destroy_all(cgrp);
- if (cgrp->parent) {
+ if (cgroup_parent(cgrp)) {
/*
* We get a ref to the parent, and put the ref when
* this cgroup is being freed, so it's guaranteed
* that the parent won't be destroyed before its
* children.
*/
- cgroup_put(cgrp->parent);
+ cgroup_put(cgroup_parent(cgrp));
kernfs_put(cgrp->kn);
kfree(cgrp);
} else {
@@ -4163,8 +4172,8 @@
css->ss = ss;
css->flags = 0;
- if (cgrp->parent) {
- css->parent = cgroup_css(cgrp->parent, ss);
+ if (cgroup_parent(cgrp)) {
+ css->parent = cgroup_css(cgroup_parent(cgrp), ss);
css_get(css->parent);
}
@@ -4218,7 +4227,7 @@
*/
static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss)
{
- struct cgroup *parent = cgrp->parent;
+ struct cgroup *parent = cgroup_parent(cgrp);
struct cgroup_subsys_state *css;
int err;
@@ -4251,7 +4260,7 @@
goto err_clear_dir;
if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
- parent->parent) {
+ cgroup_parent(parent)) {
pr_warn("%s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n",
current->comm, current->pid, ss->name);
if (!strcmp(ss->name, "memory"))
@@ -4309,7 +4318,6 @@
init_cgroup_housekeeping(cgrp);
- cgrp->parent = parent;
cgrp->self.parent = &parent->self;
cgrp->root = root;
@@ -4336,7 +4344,7 @@
cgrp->serial_nr = cgroup_serial_nr_next++;
/* allocation complete, commit to creation */
- list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);
+ list_add_tail_rcu(&cgrp->sibling, &cgroup_parent(cgrp)->children);
atomic_inc(&root->nr_cgrps);
cgroup_get(parent);
@@ -4531,8 +4539,8 @@
*/
kernfs_remove(cgrp->kn);
- set_bit(CGRP_RELEASABLE, &cgrp->parent->flags);
- check_for_release(cgrp->parent);
+ set_bit(CGRP_RELEASABLE, &cgroup_parent(cgrp)->flags);
+ check_for_release(cgroup_parent(cgrp));
/* put the base reference */
percpu_ref_kill(&cgrp->self.refcnt);
