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Message-ID: <e0a96b50-85ec-1c3d-a798-3a2e7fcab470@oracle.com>
Date: Mon, 12 Feb 2018 09:55:48 -0800
From: Shannon Nelson <shannon.nelson@...cle.com>
To: Eyal Birger <eyal.birger@...il.com>, steffen.klassert@...unet.com
Cc: herbert@...dor.apana.org.au, davem@...emloft.net,
netdev@...r.kernel.org, fw@...len.de, shmulik@...anetworks.com
Subject: Re: [PATCH ipsec] net: xfrm_policy: fix device unregistration hang
On 2/12/2018 9:21 AM, Eyal Birger wrote:
> In setups like the following:
>
> Host A -- Host B
> tun0 -- ipsec -- eth0 -- eth0 -- ipsec -- tun0
>
> where tun0 are tunnel devices using dst_cache (ipip, ipip6, etc...).
>
> Unregistration of an underlying eth0 device leads to the following log
> messages:
>
> unregister_netdevice: waiting for eth0 to become free. Usage count = 2
>
> This is since xfrm dsts device references are not released upon device
> unregistration when the xfrm dst is cached in a dst_cache.
>
> Several approaches for fixing this were discussed in [1]; this commit keeps
> track of allocated xdsts and releases their device references on a netdev
> unregister event.
>
> Signed-off-by: Eyal Birger <eyal.birger@...il.com>
>
> [1] https://patchwork.ozlabs.org/patch/869025/
> ---
> include/net/xfrm.h | 10 ++-----
> net/xfrm/xfrm_policy.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 84 insertions(+), 7 deletions(-)
>
> diff --git a/include/net/xfrm.h b/include/net/xfrm.h
> index 7d20776..c1c8493 100644
> --- a/include/net/xfrm.h
> +++ b/include/net/xfrm.h
> @@ -994,6 +994,8 @@ struct xfrm_dst {
> u32 child_mtu_cached;
> u32 route_cookie;
> u32 path_cookie;
> + struct list_head xfrm_dst_gc;
> + struct xfrm_dst_list *xfrm_dst_gc_list;
> };
>
> static inline struct dst_entry *xfrm_dst_path(const struct dst_entry *dst)
> @@ -1025,13 +1027,7 @@ static inline void xfrm_dst_set_child(struct xfrm_dst *xdst, struct dst_entry *c
> xdst->child = child;
> }
>
> -static inline void xfrm_dst_destroy(struct xfrm_dst *xdst)
> -{
> - xfrm_pols_put(xdst->pols, xdst->num_pols);
> - dst_release(xdst->route);
> - if (likely(xdst->u.dst.xfrm))
> - xfrm_state_put(xdst->u.dst.xfrm);
> -}
> +void xfrm_dst_destroy(struct xfrm_dst *xdst);
> #endif
>
> void xfrm_dst_ifdown(struct dst_entry *dst, struct net_device *dev);
> diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
> index 7a23078..1da8a65 100644
> --- a/net/xfrm/xfrm_policy.c
> +++ b/net/xfrm/xfrm_policy.c
> @@ -45,6 +45,12 @@ struct xfrm_flo {
> u8 flags;
> };
>
> +struct xfrm_dst_list {
> + spinlock_t lock; /* sync writers */
> + struct list_head head;
> +};
> +
> +static DEFINE_PER_CPU_ALIGNED(struct xfrm_dst_list, xfrm_dst_gc_list);
> static DEFINE_PER_CPU(struct xfrm_dst *, xfrm_last_dst);
> static struct work_struct *xfrm_pcpu_work __read_mostly;
> static DEFINE_SPINLOCK(xfrm_policy_afinfo_lock);
> @@ -94,6 +100,51 @@ __xfrm6_selector_match(const struct xfrm_selector *sel, const struct flowi *fl)
> (fl6->flowi6_oif == sel->ifindex || !sel->ifindex);
> }
>
> +static void xfrm_dst_add_to_gc_list(struct xfrm_dst *xdst)
> +{
> + struct xfrm_dst_list *xl = raw_cpu_ptr(&xfrm_dst_gc_list);
> +
> + xdst->xfrm_dst_gc_list = xl;
> +
> + spin_lock_bh(&xl->lock);
> + list_add_tail(&xdst->xfrm_dst_gc, &xl->head);
> + spin_unlock_bh(&xl->lock);
> +}
> +
> +void xfrm_dst_destroy(struct xfrm_dst *xdst)
> +{
> + xfrm_pols_put(xdst->pols, xdst->num_pols);
> + dst_release(xdst->route);
> + if (likely(xdst->u.dst.xfrm))
> + xfrm_state_put(xdst->u.dst.xfrm);
> + if (!list_empty(&xdst->xfrm_dst_gc)) {
> + struct xfrm_dst_list *xl = xdst->xfrm_dst_gc_list;
> +
> + spin_lock_bh(&xl->lock);
> + list_del(&xdst->xfrm_dst_gc);
> + spin_unlock_bh(&xl->lock);
> + }
> +}
> +EXPORT_SYMBOL_GPL(xfrm_dst_destroy);
> +
> +static void xfrm_flush_dev(struct net_device *dev)
> +{
> + struct xfrm_dst *xdst;
> + int cpu;
> +
> + for_each_possible_cpu(cpu) {
> + struct xfrm_dst_list *xl = &per_cpu(xfrm_dst_gc_list, cpu);
> +
> + spin_lock_bh(&xl->lock);
> + list_for_each_entry(xdst, &xl->head, xfrm_dst_gc) {
> + if (xdst->u.dst.dev != dev)
> + continue;
> + dst_dev_put(&xdst->u.dst);
> + }
> + spin_unlock_bh(&xl->lock);
> + }
> +}
> +
> bool xfrm_selector_match(const struct xfrm_selector *sel, const struct flowi *fl,
> unsigned short family)
> {
> @@ -1581,6 +1632,8 @@ static struct dst_entry *xfrm_bundle_create(struct xfrm_policy *policy,
> }
>
> bundle[i] = xdst;
> + xfrm_dst_add_to_gc_list(xdst);
> +
> if (!xdst_prev)
> xdst0 = xdst;
> else
> @@ -2937,6 +2990,20 @@ static void xfrm_policy_fini(struct net *net)
> xfrm_hash_free(net->xfrm.policy_byidx, sz);
> }
>
> +static int xfrm_netdev_event(struct notifier_block *this, unsigned long event,
> + void *ptr)
> +{
> + struct net_device *dev = netdev_notifier_info_to_dev(ptr);
> +
> + if (event == NETDEV_UNREGISTER)
> + xfrm_flush_dev(dev);
> + return NOTIFY_DONE;
> +}
> +
> +static struct notifier_block xfrm_netdev_notifier = {
> + .notifier_call = xfrm_netdev_event,
> +};
> +
Instead of creating yet another netdev notifier, can this be wired into
xfrm_dev_unregister(), the existing notifier in xfrm_decide.c which
calls into xfrm_policy_cache_flush()?
sln
> static int __net_init xfrm_net_init(struct net *net)
> {
> int rv;
> @@ -2984,6 +3051,19 @@ static struct pernet_operations __net_initdata xfrm_net_ops = {
> .exit = xfrm_net_exit,
> };
>
> +static void __init xfrm_dst_gc_init(void)
> +{
> + int cpu;
> +
> + for_each_possible_cpu(cpu) {
> + struct xfrm_dst_list *xl = &per_cpu(xfrm_dst_gc_list, cpu);
> +
> + INIT_LIST_HEAD(&xl->head);
> + spin_lock_init(&xl->lock);
> + }
> + register_netdevice_notifier(&xfrm_netdev_notifier);
> +}
> +
> void __init xfrm_init(void)
> {
> int i;
> @@ -2998,6 +3078,7 @@ void __init xfrm_init(void)
> register_pernet_subsys(&xfrm_net_ops);
> seqcount_init(&xfrm_policy_hash_generation);
> xfrm_input_init();
> + xfrm_dst_gc_init();
> }
>
> #ifdef CONFIG_AUDITSYSCALL
>
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