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Commit 69d0206c authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: bring some sanity to naming around cg_cgroup_link 



cgroups and css_sets are mapped M:N and this M:N mapping is
represented by struct cg_cgroup_link which forms linked lists on both
sides.  The naming around this mapping is already confusing and struct
cg_cgroup_link exacerbates the situation quite a bit.

>From cgroup side, it starts off ->css_sets and runs through
->cgrp_link_list.  From css_set side, it starts off ->cg_links and
runs through ->cg_link_list.  This is rather reversed as
cgrp_link_list is used to iterate css_sets and cg_link_list cgroups.
Also, this is the only place which is still using the confusing "cg"
for css_sets.  This patch cleans it up a bit.

* s/cgroup->css_sets/cgroup->cset_links/
  s/css_set->cg_links/css_set->cgrp_links/
  s/cgroup_iter->cg_link/cgroup_iter->cset_link/

* s/cg_cgroup_link/cgrp_cset_link/

* s/cgrp_cset_link->cg/cgrp_cset_link->cset/
  s/cgrp_cset_link->cgrp_link_list/cgrp_cset_link->cset_link/
  s/cgrp_cset_link->cg_link_list/cgrp_cset_link->cgrp_link/

* s/init_css_set_link/init_cgrp_cset_link/
  s/free_cg_links/free_cgrp_cset_links/
  s/allocate_cg_links/allocate_cgrp_cset_links/

* s/cgl[12]/link[12]/ in compare_css_sets()

* s/saved_link/tmp_link/ s/tmp/tmp_links/ and a couple similar
  adustments.

* Comment and whiteline adjustments.

After the changes, we have

	list_for_each_entry(link, &cont->cset_links, cset_link) {
		struct css_set *cset = link->cset;

instead of

	list_for_each_entry(link, &cont->css_sets, cgrp_link_list) {
		struct css_set *cset = link->cg;

This patch is purely cosmetic.

v2: Fix broken sentences in the patch description.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent 5abb8855

include/linux/cgroup.h

+7 −8
Original line number Diff line number Diff line
@@ -215,10 +215,10 @@ struct cgroup { 
	struct cgroupfs_root *root;



	/*

	 * List of cg_cgroup_links pointing at css_sets with

	 * tasks in this cgroup. Protected by css_set_lock

	 * List of cgrp_cset_links pointing at css_sets with tasks in this

	 * cgroup.  Protected by css_set_lock.

	 */

	struct list_head css_sets;

	struct list_head cset_links;



	struct list_head allcg_node;	/* cgroupfs_root->allcg_list */

	struct list_head cft_q_node;	/* used during cftype add/rm */
@@ -365,11 +365,10 @@ struct css_set { 
	struct list_head tasks;



	/*

	 * List of cg_cgroup_link objects on link chains from

	 * cgroups referenced from this css_set. Protected by

	 * css_set_lock

	 * List of cgrp_cset_links pointing at cgroups referenced from this

	 * css_set.  Protected by css_set_lock.

	 */

	struct list_head cg_links;

	struct list_head cgrp_links;



	/*

	 * Set of subsystem states, one for each subsystem. This array
@@ -792,7 +791,7 @@ struct cgroup *cgroup_next_descendant_post(struct cgroup *pos, 


/* A cgroup_iter should be treated as an opaque object */

struct cgroup_iter {

	struct list_head *cg_link;

	struct list_head *cset_link;

	struct list_head *task;

};

kernel/cgroup.c

+113 −113
Original line number Diff line number Diff line
@@ -315,20 +315,24 @@ static void cgroup_release_agent(struct work_struct *work); 
static DECLARE_WORK(release_agent_work, cgroup_release_agent);

static void check_for_release(struct cgroup *cgrp);



/* Link structure for associating css_set objects with cgroups */

struct cg_cgroup_link {

/*

	 * List running through cg_cgroup_links associated with a

	 * cgroup, anchored on cgroup->css_sets

 * A cgroup can be associated with multiple css_sets as different tasks may

 * belong to different cgroups on different hierarchies.  In the other

 * direction, a css_set is naturally associated with multiple cgroups.

 * This M:N relationship is represented by the following link structure

 * which exists for each association and allows traversing the associations

 * from both sides.

 */

	struct list_head cgrp_link_list;

struct cgrp_cset_link {

	/* the cgroup and css_set this link associates */

	struct cgroup		*cgrp;

	/*

	 * List running through cg_cgroup_links pointing at a

	 * single css_set object, anchored on css_set->cg_links

	 */

	struct list_head cg_link_list;

	struct css_set *cg;

	struct css_set		*cset;



	/* list of cgrp_cset_links anchored at cgrp->cset_links */

	struct list_head	cset_link;



	/* list of cgrp_cset_links anchored at css_set->cgrp_links */

	struct list_head	cgrp_link;

};



/* The default css_set - used by init and its children prior to any
@@ -339,7 +343,7 @@ struct cg_cgroup_link { 
 */



static struct css_set init_css_set;

static struct cg_cgroup_link init_css_set_link;

static struct cgrp_cset_link init_cgrp_cset_link;



static int cgroup_init_idr(struct cgroup_subsys *ss,

			   struct cgroup_subsys_state *css);
@@ -378,8 +382,7 @@ static int use_task_css_set_links __read_mostly; 


static void __put_css_set(struct css_set *cset, int taskexit)

{

	struct cg_cgroup_link *link;

	struct cg_cgroup_link *saved_link;

	struct cgrp_cset_link *link, *tmp_link;



	/*

	 * Ensure that the refcount doesn't hit zero while any readers
@@ -398,12 +401,11 @@ static void __put_css_set(struct css_set *cset, int taskexit) 
	hash_del(&cset->hlist);

	css_set_count--;



	list_for_each_entry_safe(link, saved_link, &cset->cg_links,

				 cg_link_list) {

	list_for_each_entry_safe(link, tmp_link, &cset->cgrp_links, cgrp_link) {

		struct cgroup *cgrp = link->cgrp;



		list_del(&link->cg_link_list);

		list_del(&link->cgrp_link_list);

		list_del(&link->cset_link);

		list_del(&link->cgrp_link);



		/*

		 * We may not be holding cgroup_mutex, and if cgrp->count is
@@ -475,26 +477,26 @@ static bool compare_css_sets(struct css_set *cset, 
	 * candidates.

	 */



	l1 = &cset->cg_links;

	l2 = &old_cset->cg_links;

	l1 = &cset->cgrp_links;

	l2 = &old_cset->cgrp_links;

	while (1) {

		struct cg_cgroup_link *cgl1, *cgl2;

		struct cgrp_cset_link *link1, *link2;

		struct cgroup *cgrp1, *cgrp2;



		l1 = l1->next;

		l2 = l2->next;

		/* See if we reached the end - both lists are equal length. */

		if (l1 == &cset->cg_links) {

			BUG_ON(l2 != &old_cset->cg_links);

		if (l1 == &cset->cgrp_links) {

			BUG_ON(l2 != &old_cset->cgrp_links);

			break;

		} else {

			BUG_ON(l2 == &old_cset->cg_links);

			BUG_ON(l2 == &old_cset->cgrp_links);

		}

		/* Locate the cgroups associated with these links. */

		cgl1 = list_entry(l1, struct cg_cgroup_link, cg_link_list);

		cgl2 = list_entry(l2, struct cg_cgroup_link, cg_link_list);

		cgrp1 = cgl1->cgrp;

		cgrp2 = cgl2->cgrp;

		link1 = list_entry(l1, struct cgrp_cset_link, cgrp_link);

		link2 = list_entry(l2, struct cgrp_cset_link, cgrp_link);

		cgrp1 = link1->cgrp;

		cgrp2 = link2->cgrp;

		/* Hierarchies should be linked in the same order. */

		BUG_ON(cgrp1->root != cgrp2->root);
@@ -569,61 +571,64 @@ static struct css_set *find_existing_css_set(struct css_set *old_cset, 
	return NULL;

}



static void free_cg_links(struct list_head *tmp)

static void free_cgrp_cset_links(struct list_head *links_to_free)

{

	struct cg_cgroup_link *link;

	struct cg_cgroup_link *saved_link;

	struct cgrp_cset_link *link, *tmp_link;



	list_for_each_entry_safe(link, saved_link, tmp, cgrp_link_list) {

		list_del(&link->cgrp_link_list);

	list_for_each_entry_safe(link, tmp_link, links_to_free, cset_link) {

		list_del(&link->cset_link);

		kfree(link);

	}

}



/*

 * allocate_cg_links() allocates "count" cg_cgroup_link structures

 * and chains them on tmp through their cgrp_link_list fields. Returns 0 on

 * success or a negative error

/**

 * allocate_cgrp_cset_links - allocate cgrp_cset_links

 * @count: the number of links to allocate

 * @tmp_links: list_head the allocated links are put on

 *

 * Allocate @count cgrp_cset_link structures and chain them on @tmp_links

 * through ->cset_link.  Returns 0 on success or -errno.

 */

static int allocate_cg_links(int count, struct list_head *tmp)

static int allocate_cgrp_cset_links(int count, struct list_head *tmp_links)

{

	struct cg_cgroup_link *link;

	struct cgrp_cset_link *link;

	int i;

	INIT_LIST_HEAD(tmp);



	INIT_LIST_HEAD(tmp_links);



	for (i = 0; i < count; i++) {

		link = kmalloc(sizeof(*link), GFP_KERNEL);

		if (!link) {

			free_cg_links(tmp);

			free_cgrp_cset_links(tmp_links);

			return -ENOMEM;

		}

		list_add(&link->cgrp_link_list, tmp);

		list_add(&link->cset_link, tmp_links);

	}

	return 0;

}



/**

 * link_css_set - a helper function to link a css_set to a cgroup

 * @tmp_cg_links: cg_cgroup_link objects allocated by allocate_cg_links()

 * @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()

 * @cset: the css_set to be linked

 * @cgrp: the destination cgroup

 */

static void link_css_set(struct list_head *tmp_cg_links,

			 struct css_set *cset, struct cgroup *cgrp)

static void link_css_set(struct list_head *tmp_links, struct css_set *cset,

			 struct cgroup *cgrp)

{

	struct cg_cgroup_link *link;

	struct cgrp_cset_link *link;



	BUG_ON(list_empty(tmp_cg_links));

	link = list_first_entry(tmp_cg_links, struct cg_cgroup_link,

				cgrp_link_list);

	link->cg = cset;

	BUG_ON(list_empty(tmp_links));

	link = list_first_entry(tmp_links, struct cgrp_cset_link, cset_link);

	link->cset = cset;

	link->cgrp = cgrp;

	atomic_inc(&cgrp->count);

	list_move(&link->cgrp_link_list, &cgrp->css_sets);

	list_move(&link->cset_link, &cgrp->cset_links);

	/*

	 * Always add links to the tail of the list so that the list

	 * is sorted by order of hierarchy creation

	 */

	list_add_tail(&link->cg_link_list, &cset->cg_links);

	list_add_tail(&link->cgrp_link, &cset->cgrp_links);

}



/*
@@ -638,10 +643,8 @@ static struct css_set *find_css_set(struct css_set *old_cset, 
{

	struct css_set *cset;

	struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];



	struct list_head tmp_cg_links;



	struct cg_cgroup_link *link;

	struct list_head tmp_links;

	struct cgrp_cset_link *link;

	unsigned long key;



	/* First see if we already have a cgroup group that matches
@@ -659,14 +662,14 @@ static struct css_set *find_css_set(struct css_set *old_cset, 
	if (!cset)

		return NULL;



	/* Allocate all the cg_cgroup_link objects that we'll need */

	if (allocate_cg_links(root_count, &tmp_cg_links) < 0) {

	/* Allocate all the cgrp_cset_link objects that we'll need */

	if (allocate_cgrp_cset_links(root_count, &tmp_links) < 0) {

		kfree(cset);

		return NULL;

	}



	atomic_set(&cset->refcount, 1);

	INIT_LIST_HEAD(&cset->cg_links);

	INIT_LIST_HEAD(&cset->cgrp_links);

	INIT_LIST_HEAD(&cset->tasks);

	INIT_HLIST_NODE(&cset->hlist);
@@ -676,14 +679,15 @@ static struct css_set *find_css_set(struct css_set *old_cset, 


	write_lock(&css_set_lock);

	/* Add reference counts and links from the new css_set. */

	list_for_each_entry(link, &old_cset->cg_links, cg_link_list) {

	list_for_each_entry(link, &old_cset->cgrp_links, cgrp_link) {

		struct cgroup *c = link->cgrp;



		if (c->root == cgrp->root)

			c = cgrp;

		link_css_set(&tmp_cg_links, cset, c);

		link_css_set(&tmp_links, cset, c);

	}



	BUG_ON(!list_empty(&tmp_cg_links));

	BUG_ON(!list_empty(&tmp_links));



	css_set_count++;
@@ -717,9 +721,11 @@ static struct cgroup *task_cgroup_from_root(struct task_struct *task, 
	if (cset == &init_css_set) {

		res = &root->top_cgroup;

	} else {

		struct cg_cgroup_link *link;

		list_for_each_entry(link, &cset->cg_links, cg_link_list) {

		struct cgrp_cset_link *link;



		list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {

			struct cgroup *c = link->cgrp;



			if (c->root == root) {

				res = c;

				break;
@@ -1405,7 +1411,7 @@ static void init_cgroup_housekeeping(struct cgroup *cgrp) 
	INIT_LIST_HEAD(&cgrp->sibling);

	INIT_LIST_HEAD(&cgrp->children);

	INIT_LIST_HEAD(&cgrp->files);

	INIT_LIST_HEAD(&cgrp->css_sets);

	INIT_LIST_HEAD(&cgrp->cset_links);

	INIT_LIST_HEAD(&cgrp->allcg_node);

	INIT_LIST_HEAD(&cgrp->release_list);

	INIT_LIST_HEAD(&cgrp->pidlists);
@@ -1604,7 +1610,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, 
	BUG_ON(!root);

	if (root == opts.new_root) {

		/* We used the new root structure, so this is a new hierarchy */

		struct list_head tmp_cg_links;

		struct list_head tmp_links;

		struct cgroup *root_cgrp = &root->top_cgroup;

		struct cgroupfs_root *existing_root;

		const struct cred *cred;
@@ -1636,7 +1642,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, 
		 * that's us. The worst that can happen is that we

		 * have some link structures left over

		 */

		ret = allocate_cg_links(css_set_count, &tmp_cg_links);

		ret = allocate_cgrp_cset_links(css_set_count, &tmp_links);

		if (ret)

			goto unlock_drop;
@@ -1646,7 +1652,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, 


		ret = rebind_subsystems(root, root->subsys_mask);

		if (ret == -EBUSY) {

			free_cg_links(&tmp_cg_links);

			free_cgrp_cset_links(&tmp_links);

			goto unlock_drop;

		}

		/*
@@ -1668,10 +1674,10 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, 
		 * the css_set objects */

		write_lock(&css_set_lock);

		hash_for_each(css_set_table, i, cset, hlist)

			link_css_set(&tmp_cg_links, cset, root_cgrp);

			link_css_set(&tmp_links, cset, root_cgrp);

		write_unlock(&css_set_lock);



		free_cg_links(&tmp_cg_links);

		free_cgrp_cset_links(&tmp_links);



		BUG_ON(!list_empty(&root_cgrp->children));

		BUG_ON(root->number_of_cgroups != 1);
@@ -1722,9 +1728,8 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, 
static void cgroup_kill_sb(struct super_block *sb) {

	struct cgroupfs_root *root = sb->s_fs_info;

	struct cgroup *cgrp = &root->top_cgroup;

	struct cgrp_cset_link *link, *tmp_link;

	int ret;

	struct cg_cgroup_link *link;

	struct cg_cgroup_link *saved_link;



	BUG_ON(!root);
@@ -1740,15 +1745,14 @@ static void cgroup_kill_sb(struct super_block *sb) { 
	BUG_ON(ret);



	/*

	 * Release all the links from css_sets to this hierarchy's

	 * Release all the links from cset_links to this hierarchy's

	 * root cgroup

	 */

	write_lock(&css_set_lock);



	list_for_each_entry_safe(link, saved_link, &cgrp->css_sets,

				 cgrp_link_list) {

		list_del(&link->cg_link_list);

		list_del(&link->cgrp_link_list);

	list_for_each_entry_safe(link, tmp_link, &cgrp->cset_links, cset_link) {

		list_del(&link->cset_link);

		list_del(&link->cgrp_link);

		kfree(link);

	}

	write_unlock(&css_set_lock);
@@ -2908,12 +2912,11 @@ int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts) 
int cgroup_task_count(const struct cgroup *cgrp)

{

	int count = 0;

	struct cg_cgroup_link *link;

	struct cgrp_cset_link *link;



	read_lock(&css_set_lock);

	list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {

		count += atomic_read(&link->cg->refcount);

	}

	list_for_each_entry(link, &cgrp->cset_links, cset_link)

		count += atomic_read(&link->cset->refcount);

	read_unlock(&css_set_lock);

	return count;

}
@@ -2922,24 +2925,23 @@ int cgroup_task_count(const struct cgroup *cgrp) 
 * Advance a list_head iterator.  The iterator should be positioned at

 * the start of a css_set

 */

static void cgroup_advance_iter(struct cgroup *cgrp,

				struct cgroup_iter *it)

static void cgroup_advance_iter(struct cgroup *cgrp, struct cgroup_iter *it)

{

	struct list_head *l = it->cg_link;

	struct cg_cgroup_link *link;

	struct list_head *l = it->cset_link;

	struct cgrp_cset_link *link;

	struct css_set *cset;



	/* Advance to the next non-empty css_set */

	do {

		l = l->next;

		if (l == &cgrp->css_sets) {

			it->cg_link = NULL;

		if (l == &cgrp->cset_links) {

			it->cset_link = NULL;

			return;

		}

		link = list_entry(l, struct cg_cgroup_link, cgrp_link_list);

		cset = link->cg;

		link = list_entry(l, struct cgrp_cset_link, cset_link);

		cset = link->cset;

	} while (list_empty(&cset->tasks));

	it->cg_link = l;

	it->cset_link = l;

	it->task = cset->tasks.next;

}
@@ -3160,7 +3162,7 @@ void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it) 
		cgroup_enable_task_cg_lists();



	read_lock(&css_set_lock);

	it->cg_link = &cgrp->css_sets;

	it->cset_link = &cgrp->cset_links;

	cgroup_advance_iter(cgrp, it);

}
@@ -3169,16 +3171,16 @@ struct task_struct *cgroup_iter_next(struct cgroup *cgrp, 
{

	struct task_struct *res;

	struct list_head *l = it->task;

	struct cg_cgroup_link *link;

	struct cgrp_cset_link *link;



	/* If the iterator cg is NULL, we have no tasks */

	if (!it->cg_link)

	if (!it->cset_link)

		return NULL;

	res = list_entry(l, struct task_struct, cg_list);

	/* Advance iterator to find next entry */

	l = l->next;

	link = list_entry(it->cg_link, struct cg_cgroup_link, cgrp_link_list);

	if (l == &link->cg->tasks) {

	link = list_entry(it->cset_link, struct cgrp_cset_link, cset_link);

	if (l == &link->cset->tasks) {

		/* We reached the end of this task list - move on to

		 * the next cg_cgroup_link */

		cgroup_advance_iter(cgrp, it);
@@ -4625,7 +4627,7 @@ EXPORT_SYMBOL_GPL(cgroup_load_subsys); 
 */

void cgroup_unload_subsys(struct cgroup_subsys *ss)

{

	struct cg_cgroup_link *link;

	struct cgrp_cset_link *link;



	BUG_ON(ss->module == NULL);
@@ -4654,8 +4656,8 @@ void cgroup_unload_subsys(struct cgroup_subsys *ss) 
	 * in loading, we need to pay our respects to the hashtable gods.

	 */

	write_lock(&css_set_lock);

	list_for_each_entry(link, &dummytop->css_sets, cgrp_link_list) {

		struct css_set *cset = link->cg;

	list_for_each_entry(link, &dummytop->cset_links, cset_link) {

		struct css_set *cset = link->cset;

		unsigned long key;



		hash_del(&cset->hlist);
@@ -4688,7 +4690,7 @@ int __init cgroup_init_early(void) 
{

	int i;

	atomic_set(&init_css_set.refcount, 1);

	INIT_LIST_HEAD(&init_css_set.cg_links);

	INIT_LIST_HEAD(&init_css_set.cgrp_links);

	INIT_LIST_HEAD(&init_css_set.tasks);

	INIT_HLIST_NODE(&init_css_set.hlist);

	css_set_count = 1;
@@ -4696,12 +4698,10 @@ int __init cgroup_init_early(void) 
	root_count = 1;

	init_task.cgroups = &init_css_set;



	init_css_set_link.cg = &init_css_set;

	init_css_set_link.cgrp = dummytop;

	list_add(&init_css_set_link.cgrp_link_list,

		 &rootnode.top_cgroup.css_sets);

	list_add(&init_css_set_link.cg_link_list,

		 &init_css_set.cg_links);

	init_cgrp_cset_link.cset = &init_css_set;

	init_cgrp_cset_link.cgrp = dummytop;

	list_add(&init_cgrp_cset_link.cset_link, &rootnode.top_cgroup.cset_links);

	list_add(&init_cgrp_cset_link.cgrp_link, &init_css_set.cgrp_links);



	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {

		struct cgroup_subsys *ss = subsys[i];
@@ -5454,13 +5454,13 @@ static int current_css_set_cg_links_read(struct cgroup *cont, 
					 struct cftype *cft,

					 struct seq_file *seq)

{

	struct cg_cgroup_link *link;

	struct cgrp_cset_link *link;

	struct css_set *cset;



	read_lock(&css_set_lock);

	rcu_read_lock();

	cset = rcu_dereference(current->cgroups);

	list_for_each_entry(link, &cset->cg_links, cg_link_list) {

	list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {

		struct cgroup *c = link->cgrp;

		const char *name;
@@ -5481,11 +5481,11 @@ static int cgroup_css_links_read(struct cgroup *cont, 
				 struct cftype *cft,

				 struct seq_file *seq)

{

	struct cg_cgroup_link *link;

	struct cgrp_cset_link *link;



	read_lock(&css_set_lock);

	list_for_each_entry(link, &cont->css_sets, cgrp_link_list) {

		struct css_set *cset = link->cg;

	list_for_each_entry(link, &cont->cset_links, cset_link) {

		struct css_set *cset = link->cset;

		struct task_struct *task;

		int count = 0;

		seq_printf(seq, "css_set %p\n", cset);