ipv6: Avoid double dst_free
It is a prep work to get dst freeing from fib tree undergo
a rcu grace period.
The following is a common paradigm:
if (ip6_del_rt(rt))
dst_free(rt)
which means, if rt cannot be deleted from the fib tree, dst_free(rt) now.
1. We don't know the ip6_del_rt(rt) failure is because it
was not managed by fib tree (e.g. DST_NOCACHE) or it had already been
removed from the fib tree.
2. If rt had been managed by the fib tree, ip6_del_rt(rt) failure means
dst_free(rt) has been called already. A second
dst_free(rt) is not always obviously safe. The rt may have
been destroyed already.
3. If rt is a DST_NOCACHE, dst_free(rt) should not be called.
4. It is a stopper to make dst freeing from fib tree undergo a
rcu grace period.
This patch is to use a DST_NOCACHE flag to indicate a rt is
not managed by the fib tree.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
3 files changed