mm, slab: move kfence_shutdown_cache() outside slab_mutex

kfence_shutdown_cache() is called under slab_mutex when the cache is
destroyed synchronously, and outside slab_mutex during the delayed
destruction of SLAB_TYPESAFE_BY_RCU caches.

It seems it should always be safe to call it outside of slab_mutex so we
can just move the call to kmem_cache_release(), which is called outside.

Reviewed-by: Jann Horn <jannh@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

mm/slab_common.c

@@ -492,6 +492,7 @@ EXPORT_SYMBOL(kmem_buckets_create);
  */
 static void kmem_cache_release(struct kmem_cache *s)
 {
+	kfence_shutdown_cache(s);
 	if (__is_defined(SLAB_SUPPORTS_SYSFS) && slab_state >= FULL)
 		sysfs_slab_release(s);
 	else
@@ -521,10 +522,8 @@ static void slab_caches_to_rcu_destroy_workfn(struct work_struct *work)
 
 	rcu_barrier();
 
-	list_for_each_entry_safe(s, s2, &to_destroy, list) {
+	list_for_each_entry_safe(s, s2, &to_destroy, list)
-		kfence_shutdown_cache(s);
 		kmem_cache_release(s);
-	}
 }
 
 void slab_kmem_cache_release(struct kmem_cache *s)
@@ -563,9 +562,6 @@ void kmem_cache_destroy(struct kmem_cache *s)
 
 	list_del(&s->list);
 
-	if (!err && !rcu_set)
-		kfence_shutdown_cache(s);
-
 	mutex_unlock(&slab_mutex);
 	cpus_read_unlock();