slub: Push irq disable into allocate_slab()

Do the irq handling in allocate_slab() instead of __slab_alloc().

__slab_alloc() is already cluttered and allocate_slab() is already
fiddling around with gfp flags.

v6->v7:
	Only increment ORDER_FALLBACK if we get a page during fallback
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

mm/slub.c

@@ -1187,6 +1187,11 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 	struct kmem_cache_order_objects oo = s->oo;
 	gfp_t alloc_gfp;
 
+	flags &= gfp_allowed_mask;
+
+	if (flags & __GFP_WAIT)
+		local_irq_enable();
+
 	flags |= s->allocflags;
 
 	/*
@@ -1203,12 +1208,17 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 		 * Try a lower order alloc if possible
 		 */
 		page = alloc_slab_page(flags, node, oo);
-		if (!page)
-			return NULL;
 
+		if (page)
 			stat(s, ORDER_FALLBACK);
 	}
 
+	if (flags & __GFP_WAIT)
+		local_irq_disable();
+
+	if (!page)
+		return NULL;
+
 	if (kmemcheck_enabled
 		&& !(s->flags & (SLAB_NOTRACK | DEBUG_DEFAULT_FLAGS))) {
 		int pages = 1 << oo_order(oo);
@@ -1849,15 +1859,8 @@ static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 		goto load_freelist;
 	}
 
-	gfpflags &= gfp_allowed_mask;
-	if (gfpflags & __GFP_WAIT)
-		local_irq_enable();
-
 	page = new_slab(s, gfpflags, node);
 
-	if (gfpflags & __GFP_WAIT)
-		local_irq_disable();
-
 	if (page) {
 		c = __this_cpu_ptr(s->cpu_slab);
 		stat(s, ALLOC_SLAB);