Commit eee87853 authored by Waiman Long's avatar Waiman Long Committed by Tejun Heo
Browse files

cgroup/cpuset: Add cpuset_can_fork() and cpuset_cancel_fork() methods 



In the case of CLONE_INTO_CGROUP, not all cpusets are ready to accept
new tasks. It is too late to check that in cpuset_fork(). So we need
to add the cpuset_can_fork() and cpuset_cancel_fork() methods to
pre-check it before we can allow attachment to a different cpuset.

We also need to set the attach_in_progress flag to alert other code
that a new task is going to be added to the cpuset.

Fixes: ef2c41cf ("clone3: allow spawning processes into cgroups")
Suggested-by: default avatarMichal Koutný <mkoutny@suse.com>
Signed-off-by: default avatarWaiman Long <longman@redhat.com>
Cc: stable@vger.kernel.org # v5.7+
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 42a11bf5

kernel/cgroup/cpuset.c

+86 −11
Original line number Diff line number Diff line
@@ -2453,6 +2453,20 @@ static int fmeter_getrate(struct fmeter *fmp) 


static struct cpuset *cpuset_attach_old_cs;



/*

 * Check to see if a cpuset can accept a new task

 * For v1, cpus_allowed and mems_allowed can't be empty.

 * For v2, effective_cpus can't be empty.

 * Note that in v1, effective_cpus = cpus_allowed.

 */

static int cpuset_can_attach_check(struct cpuset *cs)

{

	if (cpumask_empty(cs->effective_cpus) ||

	   (!is_in_v2_mode() && nodes_empty(cs->mems_allowed)))

		return -ENOSPC;

	return 0;

}



/* Called by cgroups to determine if a cpuset is usable; cpuset_rwsem held */

static int cpuset_can_attach(struct cgroup_taskset *tset)

{
@@ -2467,16 +2481,9 @@ static int cpuset_can_attach(struct cgroup_taskset *tset) 


	percpu_down_write(&cpuset_rwsem);



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

	ret = -ENOSPC;

	if (!is_in_v2_mode() &&

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

		goto out_unlock;



	/*

	 * Task cannot be moved to a cpuset with empty effective cpus.

	 */

	if (cpumask_empty(cs->effective_cpus))

	/* Check to see if task is allowed in the cpuset */

	ret = cpuset_can_attach_check(cs);

	if (ret)

		goto out_unlock;



	cgroup_taskset_for_each(task, css, tset) {
@@ -2493,7 +2500,6 @@ static int cpuset_can_attach(struct cgroup_taskset *tset) 
	 * changes which zero cpus/mems_allowed.

	 */

	cs->attach_in_progress++;

	ret = 0;

out_unlock:

	percpu_up_write(&cpuset_rwsem);

	return ret;
@@ -3264,6 +3270,68 @@ static void cpuset_bind(struct cgroup_subsys_state *root_css) 
	percpu_up_write(&cpuset_rwsem);

}



/*

 * In case the child is cloned into a cpuset different from its parent,

 * additional checks are done to see if the move is allowed.

 */

static int cpuset_can_fork(struct task_struct *task, struct css_set *cset)

{

	struct cpuset *cs = css_cs(cset->subsys[cpuset_cgrp_id]);

	bool same_cs;

	int ret;



	rcu_read_lock();

	same_cs = (cs == task_cs(current));

	rcu_read_unlock();



	if (same_cs)

		return 0;



	lockdep_assert_held(&cgroup_mutex);

	percpu_down_write(&cpuset_rwsem);



	/* Check to see if task is allowed in the cpuset */

	ret = cpuset_can_attach_check(cs);

	if (ret)

		goto out_unlock;



	ret = task_can_attach(task, cs->effective_cpus);

	if (ret)

		goto out_unlock;



	ret = security_task_setscheduler(task);

	if (ret)

		goto out_unlock;



	/*

	 * Mark attach is in progress.  This makes validate_change() fail

	 * changes which zero cpus/mems_allowed.

	 */

	cs->attach_in_progress++;

out_unlock:

	percpu_up_write(&cpuset_rwsem);

	return ret;

}



static void cpuset_cancel_fork(struct task_struct *task, struct css_set *cset)

{

	struct cpuset *cs = css_cs(cset->subsys[cpuset_cgrp_id]);

	bool same_cs;



	rcu_read_lock();

	same_cs = (cs == task_cs(current));

	rcu_read_unlock();



	if (same_cs)

		return;



	percpu_down_write(&cpuset_rwsem);

	cs->attach_in_progress--;

	if (!cs->attach_in_progress)

		wake_up(&cpuset_attach_wq);

	percpu_up_write(&cpuset_rwsem);

}



/*

 * Make sure the new task conform to the current state of its parent,

 * which could have been changed by cpuset just after it inherits the
@@ -3292,6 +3360,11 @@ static void cpuset_fork(struct task_struct *task) 
	percpu_down_write(&cpuset_rwsem);

	guarantee_online_mems(cs, &cpuset_attach_nodemask_to);

	cpuset_attach_task(cs, task);



	cs->attach_in_progress--;

	if (!cs->attach_in_progress)

		wake_up(&cpuset_attach_wq);



	percpu_up_write(&cpuset_rwsem);

}
@@ -3305,6 +3378,8 @@ struct cgroup_subsys cpuset_cgrp_subsys = { 
	.attach		= cpuset_attach,

	.post_attach	= cpuset_post_attach,

	.bind		= cpuset_bind,

	.can_fork	= cpuset_can_fork,

	.cancel_fork	= cpuset_cancel_fork,

	.fork		= cpuset_fork,

	.legacy_cftypes	= legacy_files,

	.dfl_cftypes	= dfl_files,