mm, slub: move irq control into unfreeze_partials()

unfreeze_partials() can be optimized so that it doesn't need irqs disabled for
the whole time. As the first step, move irq control into the function and
remove it from the put_cpu_partial() caller.
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

mm/slub.c

@@ -2350,9 +2350,8 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page,
 /*
  * Unfreeze all the cpu partial slabs.
  *
- * This function must be called with interrupts disabled
- * for the cpu using c (or some other guarantee must be there
- * to guarantee no concurrent accesses).
+ * This function must be called with preemption or migration
+ * disabled with c local to the cpu.
  */
 static void unfreeze_partials(struct kmem_cache *s,
 		struct kmem_cache_cpu *c)
@@ -2360,6 +2359,9 @@ 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;
+	unsigned long flags;
+
+	local_irq_save(flags);
 
 	while ((page = slub_percpu_partial(c))) {
 		struct page new;
@@ -2412,6 +2414,8 @@ static void unfreeze_partials(struct kmem_cache *s,
 		discard_slab(s, page);
 		stat(s, FREE_SLAB);
 	}
+
+	local_irq_restore(flags);
 #endif	/* CONFIG_SLUB_CPU_PARTIAL */
 }
 
@@ -2439,14 +2443,11 @@ static void put_cpu_partial(struct kmem_cache *s, struct page *page, int drain)
 			pobjects = oldpage->pobjects;
 			pages = oldpage->pages;
 			if (drain && pobjects > slub_cpu_partial(s)) {
-				unsigned long flags;
 				/*
 				 * partial array is full. Move the existing
 				 * set to the per node partial list.
 				 */
-				local_irq_save(flags);
 				unfreeze_partials(s, this_cpu_ptr(s->cpu_slab));
-				local_irq_restore(flags);
 				oldpage = NULL;
 				pobjects = 0;
 				pages = 0;