Date:   Fri,  2 Sep 2022 14:33:03 +0800
From:   hezhongkun <hezhongkun.hzk@...edance.com>
To:     tj@...nel.org, lizefan.x@...edance.com, hannes@...xchg.org
Cc:     cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        Zhongkun He <hezhongkun.hzk@...edance.com>
Subject: [PATCH] cgroup/cpuset: Add a new isolated mems.policy type.

From: Zhongkun He <hezhongkun.hzk@...edance.com>

Mempolicy is difficult to use because it is set in-process
via a system call. We want to make it easier to use mempolicy
in cpuset, and  we can control low-priority cgroups to
allocate memory in specified nodes. So this patch want to
adds the mempolicy interface in cpuset.

The mempolicy priority of cpuset is lower than the task.
The order of getting the policy is:
	1) vma mempolicy
	2) task->mempolicy
	3) cpuset->mempolicy
	4) default policy.

cpuset's policy is owned by itself, but descendants will
get the default mempolicy from parent.

How to use the mempolicy interface:
	echo prefer:2 > /sys/fs/cgroup/zz/cpuset.mems.policy
	echo bind:1-3 > /sys/fs/cgroup/zz/cpuset.mems.policy
        echo interleave:0,1,2,3 >/sys/fs/cgroup/zz/cpuset.mems.policy
Show the policy:
	cat /sys/fs/cgroup/zz/cpuset.mems.policy
		prefer:2
	cat /sys/fs/cgroup/zz/cpuset.mems.policy
		bind:1-3
	cat /sys/fs/cgroup/zz/cpuset.mems.policy
		interleave:0-3
Clear the policy:
	echo default > /sys/fs/cgroup/zz/cpuset.mems.policy

Signed-off-by: Zhongkun He <hezhongkun.hzk@...edance.com>
---
 include/linux/mempolicy.h |   4 +
 include/linux/sched.h     |   2 +
 kernel/cgroup/cpuset.c    | 154 +++++++++++++++++++++++++++++++++++++-
 kernel/fork.c             |   1 +
 mm/mempolicy.c            |  28 +++++--
 5 files changed, 180 insertions(+), 9 deletions(-)

diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
index 668389b4b53d..5e54dd8576e4 100644
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -142,6 +142,7 @@ extern void numa_default_policy(void);
 extern void numa_policy_init(void);
 extern void mpol_rebind_task(struct task_struct *tsk, const nodemask_t *new);
 extern void mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new);
+extern void mpol_rebind_policy(struct mempolicy *pol, const nodemask_t *newmask);
 
 extern int huge_node(struct vm_area_struct *vma,
 				unsigned long addr, gfp_t gfp_flags,
@@ -252,6 +253,9 @@ static inline void mpol_rebind_task(struct task_struct *tsk,
 static inline void mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new)
 {
 }
+static inline void mpol_rebind_policy(struct mempolicy *pol, const nodemask_t *newmask)
+{
+}
 
 static inline int huge_node(struct vm_area_struct *vma,
 				unsigned long addr, gfp_t gfp_flags,
diff --git a/include/linux/sched.h b/include/linux/sched.h
index e7b2f8a5c711..c79fc82ac9fe 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1200,6 +1200,8 @@ struct task_struct {
 	u64				acct_timexpd;
 #endif
 #ifdef CONFIG_CPUSETS
+	/* cpuset memory policy */
+	struct mempolicy		*cs_mpol;
 	/* Protected by ->alloc_lock: */
 	nodemask_t			mems_allowed;
 	/* Sequence number to catch updates: */
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 1f3a55297f39..d624393a0d7e 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -118,6 +118,9 @@ struct cpuset {
 	cpumask_var_t effective_cpus;
 	nodemask_t effective_mems;
 
+	/*cpuset mem policy */
+	struct mempolicy *mempolicy;
+
 	/*
 	 * CPUs allocated to child sub-partitions (default hierarchy only)
 	 * - CPUs granted by the parent = effective_cpus U subparts_cpus
@@ -378,6 +381,8 @@ static void cpuset_hotplug_workfn(struct work_struct *work);
 static DECLARE_WORK(cpuset_hotplug_work, cpuset_hotplug_workfn);
 
 static DECLARE_WAIT_QUEUE_HEAD(cpuset_attach_wq);
+static void cpuset_change_task_cs_mpol(struct task_struct *tsk,
+		struct mempolicy *mpol);
 
 static inline void check_insane_mems_config(nodemask_t *nodes)
 {
@@ -570,7 +575,10 @@ static struct cpuset *alloc_trial_cpuset(struct cpuset *cs)
 	if (!trial)
 		return NULL;
 
+	mpol_get(trial->mempolicy);
+
 	if (alloc_cpumasks(trial, NULL)) {
+		mpol_put(trial->mempolicy);
 		kfree(trial);
 		return NULL;
 	}
@@ -587,6 +595,10 @@ static struct cpuset *alloc_trial_cpuset(struct cpuset *cs)
 static inline void free_cpuset(struct cpuset *cs)
 {
 	free_cpumasks(cs, NULL);
+
+	if (cs->mempolicy)
+		mpol_put(cs->mempolicy);
+
 	kfree(cs);
 }
 
@@ -1823,6 +1835,7 @@ static void update_nodemasks_hier(struct cpuset *cs, nodemask_t *new_mems)
 {
 	struct cpuset *cp;
 	struct cgroup_subsys_state *pos_css;
+	nodemask_t cs_allowed;
 
 	rcu_read_lock();
 	cpuset_for_each_descendant_pre(cp, pos_css, cs) {
@@ -1848,6 +1861,11 @@ static void update_nodemasks_hier(struct cpuset *cs, nodemask_t *new_mems)
 		rcu_read_unlock();
 
 		spin_lock_irq(&callback_lock);
+
+		if (cp->mempolicy)
+			nodes_and(cs_allowed, *new_mems,
+					cp->mempolicy->w.user_nodemask);
+		mpol_rebind_policy(cp->mempolicy, &cs_allowed);
 		cp->effective_mems = *new_mems;
 		spin_unlock_irq(&callback_lock);
 
@@ -2304,7 +2322,8 @@ static void cpuset_attach(struct cgroup_taskset *tset)
 		 * fail.  TODO: have a better way to handle failure here
 		 */
 		WARN_ON_ONCE(set_cpus_allowed_ptr(task, cpus_attach));
-
+		/*update the cpuset mempolicy to task*/
+		cpuset_change_task_cs_mpol(task, cs->mempolicy);
 		cpuset_change_task_nodemask(task, &cpuset_attach_nodemask_to);
 		cpuset_update_task_spread_flag(cs, task);
 	}
@@ -2441,6 +2460,112 @@ static int cpuset_write_s64(struct cgroup_subsys_state *css, struct cftype *cft,
 	return retval;
 }
 
+/*update cpuset policy for task*/
+static void cpuset_change_task_cs_mpol(struct task_struct *tsk,
+		struct mempolicy *mpol)
+{
+	struct mempolicy *old = NULL;
+
+	task_lock(tsk);
+	local_irq_disable();
+	write_seqcount_begin(&tsk->mems_allowed_seq);
+
+	old = tsk->cs_mpol;
+	tsk->cs_mpol = mpol;
+	mpol_get(mpol);
+	tsk->il_prev = 0;
+
+	write_seqcount_end(&tsk->mems_allowed_seq);
+	local_irq_enable();
+	task_unlock(tsk);
+	mpol_put(old);
+}
+
+static void update_tasks_cs_mpol(struct cpuset *cs)
+{
+	struct css_task_iter it;
+	struct task_struct *task;
+
+	css_task_iter_start(&cs->css, 0, &it);
+
+	while ((task = css_task_iter_next(&it)))
+		cpuset_change_task_cs_mpol(task, cs->mempolicy);
+	css_task_iter_end(&it);
+}
+
+/* change cpuset mempolicy */
+static ssize_t cpuset_mpol_write(struct kernfs_open_file *of,
+		char *buf, size_t nbytes, loff_t off)
+{
+	struct mempolicy *mpol, *old = NULL;
+	struct cpuset *cs = css_cs(of_css(of));
+	nodemask_t cs_allowed;
+	int err = -ENODEV;
+
+	css_get(&cs->css);
+	kernfs_break_active_protection(of->kn);
+	percpu_down_write(&cpuset_rwsem);
+
+	if (!is_cpuset_online(cs))
+		goto out_unlock;
+
+	buf = strstrip(buf);
+	err = mpol_parse_str(buf, &mpol);
+
+	if (err) {
+		err = -EINVAL;
+		goto out_unlock;
+	}
+
+	spin_lock_irq(&callback_lock);
+	old = cs->mempolicy;
+
+	if (mpol) {
+		nodes_and(cs_allowed, cs->effective_mems, mpol->w.user_nodemask);
+		mpol_rebind_policy(mpol, &cs_allowed);
+		cs->mempolicy = mpol;
+	}
+	spin_unlock_irq(&callback_lock);
+
+	update_tasks_cs_mpol(cs);
+
+out_unlock:
+	percpu_up_write(&cpuset_rwsem);
+	kernfs_unbreak_active_protection(of->kn);
+	css_put(&cs->css);
+
+	if (old) {
+	/*Wait for outstanding programs to complete.*/
+		synchronize_rcu();
+		mpol_put(old);
+	}
+	return err ?: nbytes;
+}
+
+/*show cpuset mempolicy*/
+static int cpuset_mpol_show(struct seq_file *seq, void *v)
+{
+	char buffer[64];
+	int ret = 0;
+	struct mempolicy *mpol;
+	struct cpuset *cs = css_cs(seq_css(seq));
+
+	memset(buffer, 0, sizeof(buffer));
+	spin_lock_irq(&callback_lock);
+	mpol = cs->mempolicy;
+
+	if (!mpol || mpol->mode == MPOL_DEFAULT)
+		goto out_unlock;
+
+	mpol_to_str(buffer, sizeof(buffer), mpol);
+	seq_printf(seq, buffer);
+	seq_putc(seq, '\n');
+
+out_unlock:
+	spin_unlock_irq(&callback_lock);
+	return ret;
+}
+
 /*
  * Common handling for a write to a "cpus" or "mems" file.
  */
@@ -2679,6 +2804,13 @@ static struct cftype legacy_files[] = {
 		.private = FILE_EFFECTIVE_MEMLIST,
 	},
 
+	{
+		.name = "mems_policy",
+		.flags = CFTYPE_NOT_ON_ROOT,
+		.seq_show = cpuset_mpol_show,
+		.write = cpuset_mpol_write,
+	},
+
 	{
 		.name = "cpu_exclusive",
 		.read_u64 = cpuset_read_u64,
@@ -2787,6 +2919,13 @@ static struct cftype dfl_files[] = {
 		.private = FILE_EFFECTIVE_MEMLIST,
 	},
 
+	{
+		.name = "mems.policy",
+		.flags = CFTYPE_NOT_ON_ROOT,
+		.seq_show = cpuset_mpol_show,
+		.write = cpuset_mpol_write,
+	},
+
 	{
 		.name = "cpus.partition",
 		.seq_show = sched_partition_show,
@@ -2815,7 +2954,8 @@ static struct cftype dfl_files[] = {
 static struct cgroup_subsys_state *
 cpuset_css_alloc(struct cgroup_subsys_state *parent_css)
 {
-	struct cpuset *cs;
+	struct cpuset *cs, *pcs = css_cs(parent_css);
+	struct mempolicy *new;
 
 	if (!parent_css)
 		return &top_cpuset.css;
@@ -2835,6 +2975,16 @@ cpuset_css_alloc(struct cgroup_subsys_state *parent_css)
 	fmeter_init(&cs->fmeter);
 	cs->relax_domain_level = -1;
 
+	/*Inherit mempolicy from parent.*/
+	spin_lock_irq(&callback_lock);
+	new = mpol_dup(pcs->mempolicy);
+
+	if (IS_ERR(new))
+		new = NULL;
+
+	cs->mempolicy = new;
+	spin_unlock_irq(&callback_lock);
+
 	/* Set CS_MEMORY_MIGRATE for default hierarchy */
 	if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys))
 		__set_bit(CS_MEMORY_MIGRATE, &cs->flags);
diff --git a/kernel/fork.c b/kernel/fork.c
index 90c85b17bf69..3f695449e2a5 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2190,6 +2190,7 @@ static __latent_entropy struct task_struct *copy_process(
 		p->mempolicy = NULL;
 		goto bad_fork_cleanup_delayacct;
 	}
+	mpol_get(p->cs_mpol); /*ref cpuset mempolicy*/
 #endif
 #ifdef CONFIG_CPUSETS
 	p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index b73d3248d976..4cf54cf60244 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -158,9 +158,15 @@ int numa_map_to_online_node(int node)
 }
 EXPORT_SYMBOL_GPL(numa_map_to_online_node);
 
+static inline struct mempolicy *task_or_cs_mpol(struct task_struct *p)
+{
+	return p->mempolicy ?
+		p->mempolicy : p->cs_mpol;
+}
+
 struct mempolicy *get_task_policy(struct task_struct *p)
 {
-	struct mempolicy *pol = p->mempolicy;
+	struct mempolicy *pol = task_or_cs_mpol(p);
 	int node;
 
 	if (pol)
@@ -349,7 +355,7 @@ static void mpol_rebind_preferred(struct mempolicy *pol,
  * policies are protected by task->mems_allowed_seq to prevent a premature
  * OOM/allocation failure due to parallel nodemask modification.
  */
-static void mpol_rebind_policy(struct mempolicy *pol, const nodemask_t *newmask)
+void mpol_rebind_policy(struct mempolicy *pol, const nodemask_t *newmask)
 {
 	if (!pol || pol->mode == MPOL_LOCAL)
 		return;
@@ -1878,9 +1884,11 @@ static unsigned interleave_nodes(struct mempolicy *policy)
 	struct task_struct *me = current;
 
 	next = next_node_in(me->il_prev, policy->nodes);
-	if (next < MAX_NUMNODES)
+	if (next < MAX_NUMNODES) {
 		me->il_prev = next;
-	return next;
+		return next;
+	} else
+		return numa_node_id();
 }
 
 /*
@@ -1895,7 +1903,7 @@ unsigned int mempolicy_slab_node(void)
 	if (!in_task())
 		return node;
 
-	policy = current->mempolicy;
+	policy = task_or_cs_mpol(current);
 	if (!policy)
 		return node;
 
@@ -2043,7 +2051,7 @@ bool init_nodemask_of_mempolicy(nodemask_t *mask)
 		return false;
 
 	task_lock(current);
-	mempolicy = current->mempolicy;
+	mempolicy = task_or_cs_mpol(current);
 	switch (mempolicy->mode) {
 	case MPOL_PREFERRED:
 	case MPOL_PREFERRED_MANY:
@@ -2633,13 +2641,16 @@ int mpol_misplaced(struct page *page, struct vm_area_struct *vma, unsigned long
  */
 void mpol_put_task_policy(struct task_struct *task)
 {
-	struct mempolicy *pol;
+	struct mempolicy *pol, *cs_pol;
 
 	task_lock(task);
 	pol = task->mempolicy;
+	cs_pol = task->cs_mpol;
+	task->cs_mpol = NULL;
 	task->mempolicy = NULL;
 	task_unlock(task);
 	mpol_put(pol);
+	mpol_put(cs_pol);
 }
 
 static void sp_delete(struct shared_policy *sp, struct sp_node *n)
@@ -3054,6 +3065,9 @@ int mpol_parse_str(char *str, struct mempolicy **mpol)
 			mode_flags |= MPOL_F_RELATIVE_NODES;
 		else
 			goto out;
+	} else {
+		/*use static mode_flags in default*/
+		mode_flags |= MPOL_F_STATIC_NODES;
 	}
 
 	new = mpol_new(mode, mode_flags, &nodes);
-- 
2.25.1

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