mm, slub: detach whole partial list at once in unfreeze_partials()

Instead of iterating through the live percpu partial list, detach it from the
kmem_cache_cpu at once. This is simpler and will allow further optimization.
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

mm/slub.c

@@ -2358,16 +2358,20 @@ static void unfreeze_partials(struct kmem_cache *s,
 {
 #ifdef CONFIG_SLUB_CPU_PARTIAL
 	struct kmem_cache_node *n = NULL, *n2 = NULL;
-	struct page *page, *discard_page = NULL;
+	struct page *page, *partial_page, *discard_page = NULL;
 	unsigned long flags;
 
 	local_irq_save(flags);
 
-	while ((page = slub_percpu_partial(c))) {
+	partial_page = slub_percpu_partial(c);
+	c->partial = NULL;
+
+	while (partial_page) {
 		struct page new;
 		struct page old;
 
-		slub_set_percpu_partial(c, page);
+		page = partial_page;
+		partial_page = page->next;
 
 		n2 = get_node(s, page_to_nid(page));
 		if (n != n2) {