[PATCH net-next v2 3/3] ipv6: per netns FIB garbage collection

[Michal Kubecek]

One of our customers observed issues with FIB6 garbage collectors
running in different network namespaces blocking each other, resulting
in soft lockups (fib6_run_gc() initiated from timer runs always in
forced mode).

Now that FIB6 walkers are separated per namespace, there is no more need
for instances of fib6_run_gc() in different namespaces blocking each
other. There is still a call to icmp6_dst_gc() which operates on shared
data but this function is protected by its own shared lock.

Signed-off-by: Michal Kubecek <mkube...@suse.cz>
---
 include/net/netns/ipv6.h | 1 +
 net/ipv6/ip6_fib.c       | 9 ++++-----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/net/netns/ipv6.h b/include/net/netns/ipv6.h
index f0109b973648..10d0848f5b8a 100644
--- a/include/net/netns/ipv6.h
+++ b/include/net/netns/ipv6.h
@@ -61,6 +61,7 @@ struct netns_ipv6 {
        struct list_head        fib6_walkers;
        struct dst_ops          ip6_dst_ops;
        rwlock_t                fib6_walker_lock;
+       spinlock_t              fib6_gc_lock;
        unsigned int             ip6_rt_gc_expire;
        unsigned long            ip6_rt_last_gc;
 #ifdef CONFIG_IPV6_MULTIPLE_TABLES
diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 883f2836beab..ea071fad67a0 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -1776,16 +1776,14 @@ static int fib6_age(struct rt6_info *rt, void *arg)
        return 0;
 }
 
-static DEFINE_SPINLOCK(fib6_gc_lock);
-
 void fib6_run_gc(unsigned long expires, struct net *net, bool force)
 {
        struct fib6_gc_args gc_args;
        unsigned long now;
 
        if (force) {
-               spin_lock_bh(&fib6_gc_lock);
-       } else if (!spin_trylock_bh(&fib6_gc_lock)) {
+               spin_lock_bh(&net->ipv6.fib6_gc_lock);
+       } else if (!spin_trylock_bh(&net->ipv6.fib6_gc_lock)) {
                mod_timer(&net->ipv6.ip6_fib_timer, jiffies + HZ);
                return;
        }
@@ -1804,7 +1802,7 @@ void fib6_run_gc(unsigned long expires, struct net *net, 
bool force)
                                        + net->ipv6.sysctl.ip6_rt_gc_interval));
        else
                del_timer(&net->ipv6.ip6_fib_timer);
-       spin_unlock_bh(&fib6_gc_lock);
+       spin_unlock_bh(&net->ipv6.fib6_gc_lock);
 }
 
 static void fib6_gc_timer_cb(unsigned long arg)
@@ -1816,6 +1814,7 @@ static int __net_init fib6_net_init(struct net *net)
 {
        size_t size = sizeof(struct hlist_head) * FIB6_TABLE_HASHSZ;
 
+       spin_lock_init(&net->ipv6.fib6_gc_lock);
        rwlock_init(&net->ipv6.fib6_walker_lock);
        INIT_LIST_HEAD(&net->ipv6.fib6_walkers);
        setup_timer(&net->ipv6.ip6_fib_timer, fib6_gc_timer_cb, (unsigned 
long)net);
-- 
2.7.2