ipv6: Add rt6_make_pcpu_route()
It is a prep work for fixing a potential deadlock when creating
a pcpu rt.
The current rt6_get_pcpu_route() will also create a pcpu rt if one does not
exist. This patch moves the pcpu rt creation logic into another function,
rt6_make_pcpu_route().
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
CC: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index c95c319..0a82653 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -993,13 +993,21 @@
/* It should be called with read_lock_bh(&tb6_lock) acquired */
static struct rt6_info *rt6_get_pcpu_route(struct rt6_info *rt)
{
- struct rt6_info *pcpu_rt, *prev, **p;
+ struct rt6_info *pcpu_rt, **p;
p = this_cpu_ptr(rt->rt6i_pcpu);
pcpu_rt = *p;
- if (pcpu_rt)
- goto done;
+ if (pcpu_rt) {
+ dst_hold(&pcpu_rt->dst);
+ rt6_dst_from_metrics_check(pcpu_rt);
+ }
+ return pcpu_rt;
+}
+
+static struct rt6_info *rt6_make_pcpu_route(struct rt6_info *rt)
+{
+ struct rt6_info *pcpu_rt, *prev, **p;
pcpu_rt = ip6_rt_pcpu_alloc(rt);
if (!pcpu_rt) {
@@ -1009,6 +1017,7 @@
goto done;
}
+ p = this_cpu_ptr(rt->rt6i_pcpu);
prev = cmpxchg(p, NULL, pcpu_rt);
if (prev) {
/* If someone did it before us, return prev instead */
@@ -1093,8 +1102,11 @@
rt->dst.lastuse = jiffies;
rt->dst.__use++;
pcpu_rt = rt6_get_pcpu_route(rt);
- read_unlock_bh(&table->tb6_lock);
+ if (!pcpu_rt)
+ pcpu_rt = rt6_make_pcpu_route(rt);
+
+ read_unlock_bh(&table->tb6_lock);
return pcpu_rt;
}
}