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

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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: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Uladzislau Rezki (Sony) 2021-04-15 19:19:57 +02:00 committed by Paul E. McKenney
parent d0bfa8b3c4
commit ac7625ebd5
1 changed files with 4 additions and 10 deletions
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14
kernel/rcu/tree.c
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@ -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);
}