SLUB: Move sysfs operations outside of slub_lock

Sysfs can do a gazillion things when called.  Make sure that we do not call
any sysfs functions while holding the slub_lock.

Just protect the essentials:

1. The list of all slab caches
2. The kmalloc_dma array
3. The ref counters of the slabs.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/slub.c

@@ -2192,11 +2192,12 @@ void kmem_cache_destroy(struct kmem_cache *s)
 	s->refcount--;
 	if (!s->refcount) {
 		list_del(&s->list);
+		up_write(&slub_lock);
 		if (kmem_cache_close(s))
 			WARN_ON(1);
 		sysfs_slab_remove(s);
 		kfree(s);
-	}
+	} else
 		up_write(&slub_lock);
 }
 EXPORT_SYMBOL(kmem_cache_destroy);
@@ -2679,25 +2680,26 @@ struct kmem_cache *kmem_cache_create(const char *name, size_t size,
 		 */
 		s->objsize = max(s->objsize, (int)size);
 		s->inuse = max_t(int, s->inuse, ALIGN(size, sizeof(void *)));
+		up_write(&slub_lock);
 		if (sysfs_slab_alias(s, name))
 			goto err;
-	} else {
+		return s;
+	}
 	s = kmalloc(kmem_size, GFP_KERNEL);
-		if (s && kmem_cache_open(s, GFP_KERNEL, name,
+	if (s) {
+		if (kmem_cache_open(s, GFP_KERNEL, name,
 				size, align, flags, ctor)) {
-			if (sysfs_slab_add(s)) {
-				kfree(s);
+			list_add(&s->list, &slab_caches);
+			up_write(&slub_lock);
+			if (sysfs_slab_add(s))
 				goto err;
+			return s;
 		}
-			list_add(&s->list, &slab_caches);
-		} else
 		kfree(s);
 	}
 	up_write(&slub_lock);
-	return s;
 
 err:
-	up_write(&slub_lock);
 	if (flags & SLAB_PANIC)
 		panic("Cannot create slabcache %s\n", name);
 	else