[RFC PATCH 3/7] sched/cache: Extract sched_cache_alloc_group() helper

[Tim Chen]

Extract sched_cache_alloc_group() into kernel/sched/cache_sched.c as a
shared helper.

Convert mm_init_sched() to use the new helper instead of open-coding the
allocation and initialization.  This prepares for a second caller in the
upcoming prctl CREATE path.

No functional change.

Co-developed-by: Chen Yu <yu.c.chen@xxxxxxxxx>
Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>
Signed-off-by: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
---
 include/linux/sched.h      |  2 ++
 kernel/sched/cache_sched.c | 46 ++++++++++++++++++++++++++++++++++++++
 kernel/sched/fair.c        | 32 ++------------------------
 3 files changed, 50 insertions(+), 30 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index e7253cb332fd..e25347aa2cc5 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2406,6 +2406,8 @@ struct sched_cache_group {
 void sched_cache_group_put(struct sched_cache_group *grp);
 struct sched_cache_group *sched_cache_group_get(struct sched_cache_group *grp);
 struct sched_cache_group *task_cache_group_get(struct task_struct *p);
+struct sched_cache_group *
+sched_cache_alloc_group(struct sched_cache_time __percpu *pcpu_sched);
 
 #else
 
diff --git a/kernel/sched/cache_sched.c b/kernel/sched/cache_sched.c
index 99d07e1e067c..860209a47931 100644
--- a/kernel/sched/cache_sched.c
+++ b/kernel/sched/cache_sched.c
@@ -37,3 +37,49 @@ void sched_cache_group_put(struct sched_cache_group *grp)
 
 	call_rcu(&grp->rcu, sched_cache_group_free_rcu);
 }
+
+static void sched_cache_group_init(struct sched_cache_group *grp,
+				   struct sched_cache_time __percpu *_pcpu_sched)
+{
+	unsigned long epoch = 0;
+	int i;
+
+	for_each_possible_cpu(i) {
+		struct sched_cache_time *pcpu_sched = per_cpu_ptr(_pcpu_sched, i);
+		struct rq *rq = cpu_rq(i);
+
+		pcpu_sched->runtime = 0;
+		/* a slightly stale cpu epoch is acceptible */
+		pcpu_sched->epoch = rq->cpu_epoch;
+		epoch = rq->cpu_epoch;
+	}
+
+	raw_spin_lock_init(&grp->lock);
+	grp->epoch = epoch;
+	grp->cpu = -1;
+	grp->next_scan = jiffies;
+	grp->nr_running_avg = 0;
+	grp->footprint = 0;
+	refcount_set(&grp->refcnt, 1);
+	/*
+	 * The update to grp->pcpu_sched should not be reordered
+	 * before initialization to grp's other fields, in case
+	 * the readers may get invalid mm_sched_epoch, etc.
+	 */
+	smp_store_release(&grp->pcpu_sched, _pcpu_sched);
+}
+
+struct sched_cache_group *
+sched_cache_alloc_group(struct sched_cache_time __percpu *_pcpu_sched)
+{
+	struct sched_cache_group *grp;
+
+	grp = kzalloc_obj(*grp);
+	if (!grp) {
+		free_percpu(_pcpu_sched);
+		return NULL;
+	}
+
+	sched_cache_group_init(grp, _pcpu_sched);
+	return grp;
+}
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 281b4c896bf4..be1f3568c3aa 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1575,40 +1575,12 @@ static void account_llc_dequeue(struct rq *rq, struct task_struct *p)
 int mm_init_sched(struct mm_struct *mm,
 		  struct sched_cache_time __percpu *_pcpu_sched)
 {
-	struct sched_cache_group *grp;
-	unsigned long epoch = 0;
-	int i;
+	struct sched_cache_group *grp = sched_cache_alloc_group(_pcpu_sched);
 
-	grp = kzalloc_obj(*grp);
-	if (!grp) {
-		free_percpu(_pcpu_sched);
+	if (!grp)
 		return -ENOMEM;
-	}
-
-	for_each_possible_cpu(i) {
-		struct sched_cache_time *pcpu_sched = per_cpu_ptr(_pcpu_sched, i);
-		struct rq *rq = cpu_rq(i);
-
-		pcpu_sched->runtime = 0;
-		/* a slightly stale cpu epoch is acceptible */
-		pcpu_sched->epoch = rq->cpu_epoch;
-		epoch = rq->cpu_epoch;
-	}
 
-	raw_spin_lock_init(&grp->lock);
-	grp->epoch = epoch;
-	grp->cpu = -1;
-	grp->next_scan = jiffies;
-	grp->nr_running_avg = 0;
-	grp->footprint = 0;
-	refcount_set(&grp->refcnt, 1);
 	mm->sched_cache_grp = grp;
-	/*
-	 * The update to grp->pcpu_sched should not be reordered
-	 * before initialization to grp's other fields, in case
-	 * the readers may get invalid mm_sched_epoch, etc.
-	 */
-	smp_store_release(&grp->pcpu_sched, _pcpu_sched);
 	return 0;
 }
 
-- 
2.32.0