Commit 9e10a130 authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: replace cgroup_on_dfl() tests in controllers with cgroup_subsys_on_dfl() 



cgroup_on_dfl() tests whether the cgroup's root is the default
hierarchy; however, an individual controller is only interested in
whether the controller is attached to the default hierarchy and never
tests a cgroup which doesn't belong to the hierarchy that the
controller is attached to.

This patch replaces cgroup_on_dfl() tests in controllers with faster
static_key based cgroup_subsys_on_dfl().  This leaves cgroup core as
the only user of cgroup_on_dfl() and the function is moved from the
header file to cgroup.c.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarZefan Li <lizefan@huawei.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
parent fc5ed1e9

block/blk-throttle.c

+1 −1
Original line number Diff line number Diff line
@@ -369,7 +369,7 @@ static void throtl_pd_init(struct blkg_policy_data *pd) 
	 * regardless of the position of the group in the hierarchy.

	 */

	sq->parent_sq = &td->service_queue;

	if (cgroup_on_dfl(blkg->blkcg->css.cgroup) && blkg->parent)

	if (cgroup_subsys_on_dfl(io_cgrp_subsys) && blkg->parent)

		sq->parent_sq = &blkg_to_tg(blkg->parent)->service_queue;

	tg->td = td;

}

block/cfq-iosched.c

+2 −2
Original line number Diff line number Diff line
@@ -1581,7 +1581,7 @@ static struct blkcg_policy_data *cfq_cpd_alloc(gfp_t gfp) 
static void cfq_cpd_init(struct blkcg_policy_data *cpd)

{

	struct cfq_group_data *cgd = cpd_to_cfqgd(cpd);

	unsigned int weight = cgroup_on_dfl(blkcg_root.css.cgroup) ?

	unsigned int weight = cgroup_subsys_on_dfl(io_cgrp_subsys) ?

			      CGROUP_WEIGHT_DFL : CFQ_WEIGHT_LEGACY_DFL;



	if (cpd_to_blkcg(cpd) == &blkcg_root)
@@ -1599,7 +1599,7 @@ static void cfq_cpd_free(struct blkcg_policy_data *cpd) 
static void cfq_cpd_bind(struct blkcg_policy_data *cpd)

{

	struct blkcg *blkcg = cpd_to_blkcg(cpd);

	bool on_dfl = cgroup_on_dfl(blkcg_root.css.cgroup);

	bool on_dfl = cgroup_subsys_on_dfl(io_cgrp_subsys);

	unsigned int weight = on_dfl ? CGROUP_WEIGHT_DFL : CFQ_WEIGHT_LEGACY_DFL;



	if (blkcg == &blkcg_root)

include/linux/cgroup.h

+0 −58
Original line number Diff line number Diff line
@@ -433,64 +433,6 @@ static inline struct cgroup *task_cgroup(struct task_struct *task, 
	return task_css(task, subsys_id)->cgroup;

}



/**

 * cgroup_on_dfl - test whether a cgroup is on the default hierarchy

 * @cgrp: the cgroup of interest

 *

 * The default hierarchy is the v2 interface of cgroup and this function

 * can be used to test whether a cgroup is on the default hierarchy for

 * cases where a subsystem should behave differnetly depending on the

 * interface version.

 *

 * The set of behaviors which change on the default hierarchy are still

 * being determined and the mount option is prefixed with __DEVEL__.

 *

 * List of changed behaviors:

 *

 * - Mount options "noprefix", "xattr", "clone_children", "release_agent"

 *   and "name" are disallowed.

 *

 * - When mounting an existing superblock, mount options should match.

 *

 * - Remount is disallowed.

 *

 * - rename(2) is disallowed.

 *

 * - "tasks" is removed.  Everything should be at process granularity.  Use

 *   "cgroup.procs" instead.

 *

 * - "cgroup.procs" is not sorted.  pids will be unique unless they got

 *   recycled inbetween reads.

 *

 * - "release_agent" and "notify_on_release" are removed.  Replacement

 *   notification mechanism will be implemented.

 *

 * - "cgroup.clone_children" is removed.

 *

 * - "cgroup.subtree_populated" is available.  Its value is 0 if the cgroup

 *   and its descendants contain no task; otherwise, 1.  The file also

 *   generates kernfs notification which can be monitored through poll and

 *   [di]notify when the value of the file changes.

 *

 * - cpuset: tasks will be kept in empty cpusets when hotplug happens and

 *   take masks of ancestors with non-empty cpus/mems, instead of being

 *   moved to an ancestor.

 *

 * - cpuset: a task can be moved into an empty cpuset, and again it takes

 *   masks of ancestors.

 *

 * - memcg: use_hierarchy is on by default and the cgroup file for the flag

 *   is not created.

 *

 * - blkcg: blk-throttle becomes properly hierarchical.

 *

 * - debug: disallowed on the default hierarchy.

 */

static inline bool cgroup_on_dfl(const struct cgroup *cgrp)

{

	return cgrp->root == &cgrp_dfl_root;

}



/* no synchronization, the result can only be used as a hint */

static inline bool cgroup_has_tasks(struct cgroup *cgrp)

{

kernel/cgroup.c

+58 −0
Original line number Diff line number Diff line
@@ -237,6 +237,64 @@ static bool cgroup_ssid_enabled(int ssid) 
	return static_key_enabled(cgroup_subsys_enabled_key[ssid]);

}



/**

 * cgroup_on_dfl - test whether a cgroup is on the default hierarchy

 * @cgrp: the cgroup of interest

 *

 * The default hierarchy is the v2 interface of cgroup and this function

 * can be used to test whether a cgroup is on the default hierarchy for

 * cases where a subsystem should behave differnetly depending on the

 * interface version.

 *

 * The set of behaviors which change on the default hierarchy are still

 * being determined and the mount option is prefixed with __DEVEL__.

 *

 * List of changed behaviors:

 *

 * - Mount options "noprefix", "xattr", "clone_children", "release_agent"

 *   and "name" are disallowed.

 *

 * - When mounting an existing superblock, mount options should match.

 *

 * - Remount is disallowed.

 *

 * - rename(2) is disallowed.

 *

 * - "tasks" is removed.  Everything should be at process granularity.  Use

 *   "cgroup.procs" instead.

 *

 * - "cgroup.procs" is not sorted.  pids will be unique unless they got

 *   recycled inbetween reads.

 *

 * - "release_agent" and "notify_on_release" are removed.  Replacement

 *   notification mechanism will be implemented.

 *

 * - "cgroup.clone_children" is removed.

 *

 * - "cgroup.subtree_populated" is available.  Its value is 0 if the cgroup

 *   and its descendants contain no task; otherwise, 1.  The file also

 *   generates kernfs notification which can be monitored through poll and

 *   [di]notify when the value of the file changes.

 *

 * - cpuset: tasks will be kept in empty cpusets when hotplug happens and

 *   take masks of ancestors with non-empty cpus/mems, instead of being

 *   moved to an ancestor.

 *

 * - cpuset: a task can be moved into an empty cpuset, and again it takes

 *   masks of ancestors.

 *

 * - memcg: use_hierarchy is on by default and the cgroup file for the flag

 *   is not created.

 *

 * - blkcg: blk-throttle becomes properly hierarchical.

 *

 * - debug: disallowed on the default hierarchy.

 */

static bool cgroup_on_dfl(const struct cgroup *cgrp)

{

	return cgrp->root == &cgrp_dfl_root;

}



/* IDR wrappers which synchronize using cgroup_idr_lock */

static int cgroup_idr_alloc(struct idr *idr, void *ptr, int start, int end,

			    gfp_t gfp_mask)

kernel/cpuset.c

+13 −10
Original line number Diff line number Diff line
@@ -473,7 +473,8 @@ static int validate_change(struct cpuset *cur, struct cpuset *trial) 


	/* On legacy hiearchy, we must be a subset of our parent cpuset. */

	ret = -EACCES;

	if (!cgroup_on_dfl(cur->css.cgroup) && !is_cpuset_subset(trial, par))

	if (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&

	    !is_cpuset_subset(trial, par))

		goto out;



	/*
@@ -879,7 +880,8 @@ static void update_cpumasks_hier(struct cpuset *cs, struct cpumask *new_cpus) 
		 * If it becomes empty, inherit the effective mask of the

		 * parent, which is guaranteed to have some CPUs.

		 */

		if (cgroup_on_dfl(cp->css.cgroup) && cpumask_empty(new_cpus))

		if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&

		    cpumask_empty(new_cpus))

			cpumask_copy(new_cpus, parent->effective_cpus);



		/* Skip the whole subtree if the cpumask remains the same. */
@@ -896,7 +898,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct cpumask *new_cpus) 
		cpumask_copy(cp->effective_cpus, new_cpus);

		spin_unlock_irq(&callback_lock);



		WARN_ON(!cgroup_on_dfl(cp->css.cgroup) &&

		WARN_ON(!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&

			!cpumask_equal(cp->cpus_allowed, cp->effective_cpus));



		update_tasks_cpumask(cp);
@@ -1135,7 +1137,8 @@ static void update_nodemasks_hier(struct cpuset *cs, nodemask_t *new_mems) 
		 * If it becomes empty, inherit the effective mask of the

		 * parent, which is guaranteed to have some MEMs.

		 */

		if (cgroup_on_dfl(cp->css.cgroup) && nodes_empty(*new_mems))

		if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&

		    nodes_empty(*new_mems))

			*new_mems = parent->effective_mems;



		/* Skip the whole subtree if the nodemask remains the same. */
@@ -1152,7 +1155,7 @@ static void update_nodemasks_hier(struct cpuset *cs, nodemask_t *new_mems) 
		cp->effective_mems = *new_mems;

		spin_unlock_irq(&callback_lock);



		WARN_ON(!cgroup_on_dfl(cp->css.cgroup) &&

		WARN_ON(!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&

			!nodes_equal(cp->mems_allowed, cp->effective_mems));



		update_tasks_nodemask(cp);
@@ -1440,7 +1443,7 @@ static int cpuset_can_attach(struct cgroup_subsys_state *css, 


	/* allow moving tasks into an empty cpuset if on default hierarchy */

	ret = -ENOSPC;

	if (!cgroup_on_dfl(css->cgroup) &&

	if (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&

	    (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed)))

		goto out_unlock;
@@ -1952,7 +1955,7 @@ static int cpuset_css_online(struct cgroup_subsys_state *css) 
	cpuset_inc();



	spin_lock_irq(&callback_lock);

	if (cgroup_on_dfl(cs->css.cgroup)) {

	if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys)) {

		cpumask_copy(cs->effective_cpus, parent->effective_cpus);

		cs->effective_mems = parent->effective_mems;

	}
@@ -2029,7 +2032,7 @@ static void cpuset_bind(struct cgroup_subsys_state *root_css) 
	mutex_lock(&cpuset_mutex);

	spin_lock_irq(&callback_lock);



	if (cgroup_on_dfl(root_css->cgroup)) {

	if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys)) {

		cpumask_copy(top_cpuset.cpus_allowed, cpu_possible_mask);

		top_cpuset.mems_allowed = node_possible_map;

	} else {
@@ -2210,7 +2213,7 @@ retry: 
	cpus_updated = !cpumask_equal(&new_cpus, cs->effective_cpus);

	mems_updated = !nodes_equal(new_mems, cs->effective_mems);



	if (cgroup_on_dfl(cs->css.cgroup))

	if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys))

		hotplug_update_tasks(cs, &new_cpus, &new_mems,

				     cpus_updated, mems_updated);

	else
@@ -2241,7 +2244,7 @@ static void cpuset_hotplug_workfn(struct work_struct *work) 
	static cpumask_t new_cpus;

	static nodemask_t new_mems;

	bool cpus_updated, mems_updated;

	bool on_dfl = cgroup_on_dfl(top_cpuset.css.cgroup);

	bool on_dfl = cgroup_subsys_on_dfl(cpuset_cgrp_subsys);



	mutex_lock(&cpuset_mutex);

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