On Tue, Feb 13, 2018 at 6:54 PM, Eyal Birger <eyal.bir...@gmail.com> 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.
>
> This issue was first introduced in commit 52df157f17e5
> ("xfrm: take refcnt of dst when creating struct xfrm_dst bundle")
> as part of an effort to remove routing garbage collection.
>
> 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/down events.
>
> Signed-off-by: Eyal Birger <eyal.bir...@gmail.com>
> Fixes: 52df157f17e5 ("xfrm: take refcnt of dst when creating struct xfrm_dst 
> bundle")
I had another fix [1] for this issue in my local tree.
That reuses uncached_list to track xdsts, and fewer job to do for this.
As naturally uncached_list is already the list that is supposed to do this job.
We don't have to introduce a new list and members.

[1] https://paste.fedoraproject.org/paste/X8FQzEXjGXQBTKAVLnDn4w

Not sure if it makes more sense for xfrm?

Thanks.

>
> [1] https://patchwork.ozlabs.org/patch/869025/
>
> ---
>
> v3:
>   - add 'Fixes' tag and document appropriately
> v2:
>   - call gc flush from existing netdev notifier per Shannon Nelson's
>     suggestion.
> ---
>  include/net/xfrm.h     | 11 +++------
>  net/xfrm/xfrm_device.c |  2 ++
>  net/xfrm/xfrm_policy.c | 66 
> ++++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 72 insertions(+), 7 deletions(-)
>
> diff --git a/include/net/xfrm.h b/include/net/xfrm.h
> index 7d20776..4614047 100644
> --- a/include/net/xfrm.h
> +++ b/include/net/xfrm.h
> @@ -324,6 +324,7 @@ void xfrm_policy_unregister_afinfo(const struct 
> xfrm_policy_afinfo *afinfo);
>  void km_policy_notify(struct xfrm_policy *xp, int dir,
>                       const struct km_event *c);
>  void xfrm_policy_cache_flush(void);
> +void xfrm_policy_dst_gc_flush_dev(struct net_device *dev);
>  void km_state_notify(struct xfrm_state *x, const struct km_event *c);
>
>  struct xfrm_tmpl;
> @@ -994,6 +995,8 @@ 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 +1028,7 @@ 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_device.c b/net/xfrm/xfrm_device.c
> index 8e70291..5bd9892 100644
> --- a/net/xfrm/xfrm_device.c
> +++ b/net/xfrm/xfrm_device.c
> @@ -309,6 +309,7 @@ static int xfrm_dev_register(struct net_device *dev)
>  static int xfrm_dev_unregister(struct net_device *dev)
>  {
>         xfrm_policy_cache_flush();
> +       xfrm_policy_dst_gc_flush_dev(dev);
>         return NOTIFY_DONE;
>  }
>
> @@ -323,6 +324,7 @@ static int xfrm_dev_down(struct net_device *dev)
>                 xfrm_dev_state_flush(dev_net(dev), dev, true);
>
>         xfrm_policy_cache_flush();
> +       xfrm_policy_dst_gc_flush_dev(dev);
>         return NOTIFY_DONE;
>  }
>
> diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
> index 7a23078..c7b9a9a 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);
> +
> +void xfrm_policy_dst_gc_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
> @@ -2984,6 +3037,18 @@ 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);
> +       }
> +}
> +
>  void __init xfrm_init(void)
>  {
>         int i;
> @@ -2998,6 +3063,7 @@ 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
> --
> 2.7.4
>

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