Commit ac7625eb authored by Uladzislau Rezki (Sony)'s avatar Uladzislau Rezki (Sony) Committed by Paul E. McKenney
Browse files

kvfree_rcu: Use [READ/WRITE]_ONCE() macros to access to nr_bkv_objs 



nr_bkv_objs is a count of the objects in the kvfree_rcu page cache.
Accessing it requires holding the ->lock.  Switch to READ_ONCE() and
WRITE_ONCE() macros to provide lockless access to this counter.
This lockless access is used for the shrinker.

Signed-off-by: default avatarUladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent d0bfa8b3

kernel/rcu/tree.c

+4 −10
Original line number Diff line number Diff line
@@ -3250,7 +3250,7 @@ get_cached_bnode(struct kfree_rcu_cpu *krcp) 
	if (!krcp->nr_bkv_objs)

		return NULL;



	krcp->nr_bkv_objs--;

	WRITE_ONCE(krcp->nr_bkv_objs, krcp->nr_bkv_objs - 1);

	return (struct kvfree_rcu_bulk_data *)

		llist_del_first(&krcp->bkvcache);

}
@@ -3264,9 +3264,8 @@ put_cached_bnode(struct kfree_rcu_cpu *krcp, 
		return false;



	llist_add((struct llist_node *) bnode, &krcp->bkvcache);

	krcp->nr_bkv_objs++;

	WRITE_ONCE(krcp->nr_bkv_objs, krcp->nr_bkv_objs + 1);

	return true;



}



static int
@@ -3278,7 +3277,7 @@ drain_page_cache(struct kfree_rcu_cpu *krcp) 


	raw_spin_lock_irqsave(&krcp->lock, flags);

	page_list = llist_del_all(&krcp->bkvcache);

	krcp->nr_bkv_objs = 0;

	WRITE_ONCE(krcp->nr_bkv_objs, 0);

	raw_spin_unlock_irqrestore(&krcp->lock, flags);



	llist_for_each_safe(pos, n, page_list) {
@@ -3682,18 +3681,13 @@ kfree_rcu_shrink_count(struct shrinker *shrink, struct shrink_control *sc) 
{

	int cpu;

	unsigned long count = 0;

	unsigned long flags;



	/* Snapshot count of all CPUs */

	for_each_possible_cpu(cpu) {

		struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);



		count += READ_ONCE(krcp->count);



		raw_spin_lock_irqsave(&krcp->lock, flags);

		count += krcp->nr_bkv_objs;

		raw_spin_unlock_irqrestore(&krcp->lock, flags);



		count += READ_ONCE(krcp->nr_bkv_objs);

		atomic_set(&krcp->backoff_page_cache_fill, 1);

	}