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    Subject[PATCH net-next v2 3/3] ipv6: per netns FIB garbage collection
    Date
    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 <mkubecek@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
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