[PATCH -mm 5/6] slqb: introduce __kfree_rcu

[Lai Jiangshan <laijs@cn.fujitsu.com>]

Introduce __kfree_rcu() for kfree_rcu()

It like __kfree_rcu() in slab.c, slub.c
We can calculate the object poiter from a poiter inside this
object in slqb.c, so we can use it for rcu callback and free
the object.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
diff --git a/mm/slqb.c b/mm/slqb.c
index 48bdf3b..c258ddc 100644
--- a/mm/slqb.c
+++ b/mm/slqb.c
@@ -2482,6 +2484,23 @@ void kfree(const void *object)
 }
 EXPORT_SYMBOL(kfree);
 
+static void kfree_rcu_callback(struct rcu_head *rcu)
+{
+	void *portion = rcu;
+	struct slqb_page *page = virt_to_head_slqb_page(portion);
+	struct kmem_cache *s = page->list->cache;
+	unsigned int index = (portion - page->s_mem) / s->size;
+	void *object = page->s_mem + s->size * index;
+
+	slab_free(s, page, object);
+}
+
+void __kfree_rcu(const void *objp, struct rcu_head *rcu)
+{
+	call_rcu(rcu, kfree_rcu_callback);
+}
+EXPORT_SYMBOL(__kfree_rcu);
+
 static void kmem_cache_trim_percpu(void *arg)
 {
 	int cpu = smp_processor_id();