Subject: [PATCHv3 net-next] xfrm: Namespacify xfrm_policy_sk_bundles

From: Fan Du <[email-masked]>
Date: Thu, 19 Dec 2013 11:17:39 +0800

On 2013年12月19日 10:15, Eric Dumazet wrote:
>> I think an analogy of llist_add_batch for the updating part will be ok for this:
>> >
>> >                            struct dst_entry *first;
>> >                            do {
>> >                                    xdst->u.dst.next = first = ACCESS_ONCE(xfrm_policy_sk_bundles);
>> >                            } while (cmpxchg(&xfrm_policy_sk_bundles, first,&xdst->u.dst) != first);
>> >
>> >
>> >  And the deleting part:
>> >
>> >                            head = xchg(&net->xfrm.xfrm_policy_sk_bundles, NULL);
>> >
>> >
> The point is to_use_  the helpers, so that code review is easy.
>
> llist.h is safe, it was extensively discussed and adopted.
>
> If you want to get rid of the spinlock, then use llist_del_all() for the
> deleting, and llist_add() for the addition.
>
> Really, its that simple.

Ok, I will use common api suggested by you, then locks is gone at the cost
of xfrm_dst growing up a bit, sizeof(struct llist_node).

 From b4c5fc86861abd98866111a7b1b51dc13d546a0c Mon Sep 17 00:00:00 2001
From: Fan Du <[email-masked]>
Date: Thu, 19 Dec 2013 11:03:20 +0800
Subject: [PATCHv3 net-next] xfrm: Namespacify xfrm_policy_sk_bundles

xfrm_policy_sk_bundles, protected by net->xfrm.xfrm_policy_sk_bundle_lock
should be put into netns xfrm structure, otherwise xfrm_policy_sk_bundles
can be corrupted from different net namespace.

Moreover current xfrm_policy_sk_bundle_lock used in below two scenarios:

1. xfrm_lookup(Process context)  vs  __xfrm_garbage_collect(softirq context)
2. xfrm_lookup(Process context)  vs  __xfrm_garbage_collect(Process context
                                                 when SPD change or dev down)

We can use lock less list to cater to those two scenarios as suggested by
Eric Dumazet.

Signed-off-by: Fan Du <[email-masked]>
Assisted-by: Eric Dumazet <[email-masked]>
---
v2:
   Fix incorrect commit log.

v3:
   Drop xchg, use llist instead, adviced by Eric Dumazet.
   Build test only.
---
  include/net/netns/xfrm.h |    2 +-
  include/net/xfrm.h       |    1 +
  net/xfrm/xfrm_policy.c   |   26 ++++++--------------------
  3 files changed, 8 insertions(+), 21 deletions(-)

diff --git a/include/net/netns/xfrm.h b/include/net/netns/xfrm.h
index 1006a26..22f4f90 100644
--- a/include/net/netns/xfrm.h
+++ b/include/net/netns/xfrm.h
@@ -58,9 +58,9 @@ struct netns_xfrm {
  	struct dst_ops		xfrm6_dst_ops;
  #endif
  	spinlock_t xfrm_state_lock;
-	spinlock_t xfrm_policy_sk_bundle_lock;
  	rwlock_t xfrm_policy_lock;
  	struct mutex xfrm_cfg_mutex;
+	struct llist_head xp_sk_bundles_list;
  };

  #endif
diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index 59f5d0a..05296ab 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -957,6 +957,7 @@ struct xfrm_dst {
  	u32 child_mtu_cached;
  	u32 route_cookie;
  	u32 path_cookie;
+	struct llist_node       xdst_llist;
  };

  #ifdef CONFIG_XFRM
diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index a7487f3..fb286af 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -39,8 +39,6 @@
  #define XFRM_QUEUE_TMO_MAX ((unsigned)(60*HZ))
  #define XFRM_MAX_QUEUE_LEN	100

-static struct dst_entry *xfrm_policy_sk_bundles;
-
  static DEFINE_SPINLOCK(xfrm_policy_afinfo_lock);
  static struct xfrm_policy_afinfo __rcu *xfrm_policy_afinfo[NPROTO]
  						__read_mostly;
@@ -2108,12 +2106,7 @@ struct dst_entry *xfrm_lookup(struct net *net, struct dst_entry *dst_orig,
  			}

  			dst_hold(&xdst->u.dst);
-
-			spin_lock_bh(&net->xfrm.xfrm_policy_sk_bundle_lock);
-			xdst->u.dst.next = xfrm_policy_sk_bundles;
-			xfrm_policy_sk_bundles = &xdst->u.dst;
-			spin_unlock_bh(&net->xfrm.xfrm_policy_sk_bundle_lock);
-
+			llist_add(&xdst->xdst_llist, &net->xfrm.xp_sk_bundles_list);
  			route = xdst->route;
  		}
  	}
@@ -2549,18 +2542,12 @@ static struct dst_entry *xfrm_negative_advice(struct dst_entry *dst)

  static void __xfrm_garbage_collect(struct net *net)
  {
-	struct dst_entry *head, *next;
-
-	spin_lock_bh(&net->xfrm.xfrm_policy_sk_bundle_lock);
-	head = xfrm_policy_sk_bundles;
-	xfrm_policy_sk_bundles = NULL;
-	spin_unlock_bh(&net->xfrm.xfrm_policy_sk_bundle_lock);
+	struct llist_node *head;
+	struct xfrm_dst *xdst;

-	while (head) {
-		next = head->next;
-		dst_free(head);
-		head = next;
-	}
+	head = llist_del_all(&net->xfrm.xp_sk_bundles_list);
+	llist_for_each_entry(xdst, head, xdst_llist)
+		dst_free(&xdst->u.dst);
  }

  void xfrm_garbage_collect(struct net *net)
@@ -2942,7 +2929,6 @@ static int __net_init xfrm_net_init(struct net *net)
  	/* Initialize the per-net locks here */
  	spin_lock_init(&net->xfrm.xfrm_state_lock);
  	rwlock_init(&net->xfrm.xfrm_policy_lock);
-	spin_lock_init(&net->xfrm.xfrm_policy_sk_bundle_lock);
  	mutex_init(&net->xfrm.xfrm_cfg_mutex);

  	return 0;
-- 
1.7.9.5

-- 
浮沉随浪只记今朝笑

--fan