mm, slub: restore irqs around calling new_slab()

allocate_slab() currently re-enables irqs before calling to the page allocator.
It depends on gfpflags_allow_blocking() to determine if it's safe to do so.
Now we can instead simply restore irq before calling it through new_slab().
The other caller early_kmem_cache_node_alloc() is unaffected by this.
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

mm/slub.c

@@ -1809,9 +1809,6 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 
 	flags &= gfp_allowed_mask;
 
-	if (gfpflags_allow_blocking(flags))
-		local_irq_enable();
-
 	flags |= s->allocflags;
 
 	/*
@@ -1870,8 +1867,6 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 	page->frozen = 1;
 
 out:
-	if (gfpflags_allow_blocking(flags))
-		local_irq_disable();
 	if (!page)
 		return NULL;
 
@@ -2812,16 +2807,17 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 		goto check_new_page;
 	}
 
+	local_irq_restore(flags);
 	put_cpu_ptr(s->cpu_slab);
 	page = new_slab(s, gfpflags, node);
 	c = get_cpu_ptr(s->cpu_slab);
 
 	if (unlikely(!page)) {
-		local_irq_restore(flags);
 		slab_out_of_memory(s, gfpflags, node);
 		return NULL;
 	}
 
+	local_irq_save(flags);
 	if (c->page)
 		flush_slab(s, c);