On Thu, May 11, 2017 at 5:07 PM, Cong Wang <xiyou.wangc...@gmail.com> wrote:
> So, if I understand you correctly it is safe to NULL'ing
> nh_dev in NETDEV_UNREGISTER_FINAL, right?
>
> If still not, how about transfer nh_dev's to loopback_dev
> too in NETDEV_UNREGISTER? Like we transfer dst->dev.
>
> I don't want to touch the fast path to check for NULL, as
> it will change more code and slow down performance.
Finally I come up with the attached patch. Please let me know if
I still miss anything.
commit edc38ecab7101487b35fc9152e166a2670467e49
Author: Cong Wang <xiyou.wangc...@gmail.com>
Date: Tue May 9 14:35:10 2017 -0700
ipv4: restore rt->fi for reference counting, try #2
Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
index 6692c57..0f04f4d 100644
--- a/include/net/ip_fib.h
+++ b/include/net/ip_fib.h
@@ -392,6 +392,7 @@ int fib_unmerge(struct net *net);
/* Exported by fib_semantics.c */
int ip_fib_check_default(__be32 gw, struct net_device *dev);
int fib_sync_down_dev(struct net_device *dev, unsigned long event, bool force);
+void fib_put_nh_devs(struct net_device *dev);
int fib_sync_down_addr(struct net_device *dev, __be32 local);
int fib_sync_up(struct net_device *dev, unsigned int nh_flags);
diff --git a/include/net/route.h b/include/net/route.h
index 2cc0e14..4335eb7 100644
--- a/include/net/route.h
+++ b/include/net/route.h
@@ -69,6 +69,7 @@ struct rtable {
struct list_head rt_uncached;
struct uncached_list *rt_uncached_list;
+ struct fib_info *fi; /* for refcnt to shared metrics */
};
static inline bool rt_is_input_route(const struct rtable *rt)
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 39bd1ed..59b0a1d 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -1178,6 +1178,9 @@ static int fib_netdev_event(struct notifier_block *this,
unsigned long event, vo
fib_disable_ip(dev, event, true);
rt_flush_dev(dev);
return NOTIFY_DONE;
+ } else if (event == NETDEV_UNREGISTER_FINAL) {
+ fib_put_nh_devs(dev);
+ return NOTIFY_DONE;
}
in_dev = __in_dev_get_rtnl(dev);
diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index da449dd..b85c5bb 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -1453,6 +1453,36 @@ int fib_sync_down_dev(struct net_device *dev, unsigned
long event, bool force)
return ret;
}
+/* We have to release these nh_dev here because a dst could still hold a
+ * fib_info via rt->fi, we can't wait for GC, a socket could hold the dst
+ * for a long time.
+ */
+void fib_put_nh_devs(struct net_device *dev)
+{
+ struct fib_info *prev_fi = NULL;
+ unsigned int hash = fib_devindex_hashfn(dev->ifindex);
+ struct hlist_head *head = &fib_info_devhash[hash];
+ struct fib_nh *nh;
+
+ hlist_for_each_entry(nh, head, nh_hash) {
+ struct fib_info *fi = nh->nh_parent;
+
+ if (nh->nh_dev != dev || fi == prev_fi)
+ continue;
+ prev_fi = fi;
+ change_nexthops(fi) {
+ if (nexthop_nh->nh_dev == dev) {
+ /* This should be safe, we are on unregister
+ * path, after synchronize_net() and
+ * rcu_barrier(), no one could see this.
+ */
+ RCU_INIT_POINTER(nexthop_nh->nh_dev, NULL);
+ dev_put(dev);
+ }
+ } endfor_nexthops(fi)
+ }
+}
+
/* Must be invoked inside of an RCU protected region. */
static void fib_select_default(const struct flowi4 *flp, struct fib_result
*res)
{
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 655d9ee..f647310 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1387,6 +1387,11 @@ static void ipv4_dst_destroy(struct dst_entry *dst)
{
struct rtable *rt = (struct rtable *) dst;
+ if (rt->fi) {
+ fib_info_put(rt->fi);
+ rt->fi = NULL;
+ }
+
if (!list_empty(&rt->rt_uncached)) {
struct uncached_list *ul = rt->rt_uncached_list;
@@ -1424,6 +1429,16 @@ static bool rt_cache_valid(const struct rtable *rt)
!rt_is_expired(rt);
}
+static void rt_init_metrics(struct rtable *rt, struct fib_info *fi)
+{
+ if (fi->fib_metrics != (u32 *)dst_default_metrics) {
+ fib_info_hold(fi);
+ rt->fi = fi;
+ }
+
+ dst_init_metrics(&rt->dst, fi->fib_metrics, true);
+}
+
static void rt_set_nexthop(struct rtable *rt, __be32 daddr,
const struct fib_result *res,
struct fib_nh_exception *fnhe,
@@ -1438,7 +1453,7 @@ static void rt_set_nexthop(struct rtable *rt, __be32
daddr,
rt->rt_gateway = nh->nh_gw;
rt->rt_uses_gateway = 1;
}
- dst_init_metrics(&rt->dst, fi->fib_metrics, true);
+ rt_init_metrics(rt, fi);
#ifdef CONFIG_IP_ROUTE_CLASSID
rt->dst.tclassid = nh->nh_tclassid;
#endif
@@ -1490,6 +1505,7 @@ struct rtable *rt_dst_alloc(struct net_device *dev,
rt->rt_gateway = 0;
rt->rt_uses_gateway = 0;
rt->rt_table_id = 0;
+ rt->fi = NULL;
INIT_LIST_HEAD(&rt->rt_uncached);
rt->dst.output = ip_output;
