Subject: Re: [PATCHv4 net-next] xfrm: Namespacify xfrm_policy_sk_bundles

From: Fan Du <[email-masked]>
Date: Tue, 24 Dec 2013 09:12:32 +0800

On 2013年12月20日 11:34, Fan Du wrote:
>
>
> On 2013年12月19日 11:44, Eric Dumazet wrote:
>> On Thu, 2013-12-19 at 11:17 +0800, Fan Du wrote:
>>>
>>
>>> 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;
>>> };
>>>
>>
>> Hmm... Thats not very nice.
>>
>> Please reuse the storage adding a llist_node in the union ?
>>
>> diff --git a/include/net/dst.h b/include/net/dst.h
>> index 44995c13e941..3f604f47cc58 100644
>> --- a/include/net/dst.h
>> +++ b/include/net/dst.h
>> @@ -14,6 +14,7 @@
>> #include<linux/rcupdate.h>
>> #include<linux/bug.h>
>> #include<linux/jiffies.h>
>> +#include<linux/llist.h>
>> #include<net/neighbour.h>
>> #include<asm/processor.h>
>>
>> @@ -103,6 +104,7 @@ struct dst_entry {
>> struct rtable __rcu *rt_next;
>> struct rt6_info *rt6_next;
>> struct dn_route __rcu *dn_next;
>> + struct llist_node llist;
>> };
>> };
>
> Hi, Eric
>
> You are correct on this, have fix the patch wrt your comments.
> Thank you very much.
>
>
>  From 1b929e1cdea978d0c8d10d731af84969bd37004b Mon Sep 17 00:00:00 2001
> From: Fan Du <[email-masked]>
> Date: Fri, 20 Dec 2013 11:23:27 +0800
> Subject: [PATCHv4 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.

Hi Dave

I saw this patch is marked 'Not Applicable' in patchwork.

Not sure what's the improperness in it, corruption of xfrm_policy_sk_bundles
from different netns is real problem here. If you don't like below lock less
addition to avoid original spinlock, I could drop this part if you would require
and then put xfrm_policy_sk_bundles in net.xfrm only.

Could you please comment on this?
Thanks a lot :)

> 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.
>
> v4:
> Incorporate Eric's comments.
> -Union llist with dst_entry->next, which is used for queuing previous,
> then it's safe to do so.
> -Use llist_for_each_entry_safe for purging list.
> -Rebase with net-next, as ipsec-next got pulled.
>
> ---
> include/net/dst.h | 5 +++++
> include/net/netns/xfrm.h | 2 +-
> net/xfrm/xfrm_policy.c | 26 ++++++--------------------
> 3 files changed, 12 insertions(+), 21 deletions(-)
>
> diff --git a/include/net/dst.h b/include/net/dst.h
> index 77eb53f..e9b81f0 100644
> --- a/include/net/dst.h
> +++ b/include/net/dst.h
> @@ -14,6 +14,7 @@
> #include <linux/rcupdate.h>
> #include <linux/bug.h>
> #include <linux/jiffies.h>
> +#include <linux/llist.h>
> #include <net/neighbour.h>
> #include <asm/processor.h>
>
> @@ -103,6 +104,10 @@ struct dst_entry {
> struct rtable __rcu *rt_next;
> struct rt6_info *rt6_next;
> struct dn_route __rcu *dn_next;
> +#ifdef CONFIG_XFRM
> + /* Used to queue each policy sk dst */
> + struct llist_node llist;
> +#endif
> };
> };
>
> 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/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
> index a7487f3..0cc7446 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->u.dst.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;
> + struct llist_node *head;
> + struct dst_entry *dst, *tmp;
>
> - 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);
> -
> - while (head) {
> - next = head->next;
> - dst_free(head);
> - head = next;
> - }
> + head = llist_del_all(&net->xfrm.xp_sk_bundles_list);
> + llist_for_each_entry_safe(dst, tmp, head, llist)
> + dst_free(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;

-- 
浮沉随浪只记今朝笑

--fan