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Commit d51f39b0 authored by Tejun Heo's avatar Tejun Heo
Browse files

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: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent 5877019d

include/linux/cgroup.h

+0 −1
Original line number Diff line number Diff line
@@ -178,7 +178,6 @@ struct cgroup { 
	struct list_head sibling;	/* my parent's children */

	struct list_head children;	/* my children */



	struct cgroup *parent;		/* my parent */

	struct kernfs_node *kn;		/* cgroup kernfs entry */

	struct kernfs_node *populated_kn; /* kn for "cgroup.subtree_populated" */

kernel/cgroup.c

+30 −22
Original line number Diff line number Diff line
@@ -218,6 +218,15 @@ static void cgroup_idr_remove(struct idr *idr, int id) 
	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 @@ static struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp, 
	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 @@ bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor) 
	while (cgrp) {

		if (cgrp == ancestor)

			return true;

		cgrp = cgrp->parent;

		cgrp = cgroup_parent(cgrp);

	}

	return false;

}
@@ -454,7 +463,7 @@ static void cgroup_update_populated(struct cgroup *cgrp, bool populated) 


		if (cgrp->populated_kn)

			kernfs_notify(cgrp->populated_kn);

		cgrp = cgrp->parent;

		cgrp = cgroup_parent(cgrp);

	} while (cgrp);

}
@@ -2018,7 +2027,7 @@ static int cgroup_migrate_prepare_dst(struct cgroup *dst_cgrp, 
	 * 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 @@ static int cgroup_controllers_show(struct seq_file *seq, void *v) 
{

	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 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of, 


			/* 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 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of, 
	 * 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 @@ static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[], 
			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 @@ static void css_free_work_fn(struct work_struct *work) 
		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 @@ static void init_and_link_css(struct cgroup_subsys_state *css, 
	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 void offline_css(struct cgroup_subsys_state *css) 
 */

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 @@ static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss) 
		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 @@ static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, 


	init_cgroup_housekeeping(cgrp);



	cgrp->parent = parent;

	cgrp->self.parent = &parent->self;

	cgrp->root = root;
@@ -4336,7 +4344,7 @@ static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, 
	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 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) 
	 */

	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);