page_pool: remove spinlock in page_pool_refill_alloc_cache()

As page_pool_refill_alloc_cache() is only called by
__page_pool_get_cached(), which assumes non-concurrent access
as suggested by the comment in __page_pool_get_cached(), and
ptr_ring allows concurrent access between consumer and producer,
so remove the spinlock in page_pool_refill_alloc_cache().

Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Link: https://lore.kernel.org/r/20220107090042.13605-1-linyunsheng@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/core/page_pool.c

@@ -130,9 +130,6 @@ static struct page *page_pool_refill_alloc_cache(struct page_pool *pool)
 	pref_nid = numa_mem_id(); /* will be zero like page_to_nid() */
 #endif
 
-	/* Slower-path: Get pages from locked ring queue */
-	spin_lock(&r->consumer_lock);
-
 	/* Refill alloc array, but only if NUMA match */
 	do {
 		page = __ptr_ring_consume(r);
@@ -157,7 +154,6 @@ static struct page *page_pool_refill_alloc_cache(struct page_pool *pool)
 	if (likely(pool->alloc.count > 0))
 		page = pool->alloc.cache[--pool->alloc.count];
 
-	spin_unlock(&r->consumer_lock);
 	return page;
 }