Re: [PATCH] net: mpls: Fix nexthop alive tracking on down events

[David Miller <davem@davemloft.net>]

From: David Ahern <dsa@cumulusnetworks.com>
Date: Mon, 13 Mar 2017 16:49:10 -0700

> Alive tracking of nexthops can account for a link twice if the carrier
> goes down followed by an admin down of the same link rendering multipath
> routes useless. This is similar to 79099aab38c8 for UNREGISTER events and
> DOWN events.
> 
> Fix by tracking number of alive nexthops in mpls_ifdown similar to the
> logic in mpls_ifup. Checking the flags per nexthop once after all events
> have been processed is simpler than trying to maintian a running count
> through all event combinations.
> 
> Also, WRITE_ONCE is used instead of ACCESS_ONCE to set rt_nhn_alive
> per a comment from checkpatch:
>     WARNING: Prefer WRITE_ONCE(<FOO>, <BAR>) over ACCESS_ONCE(<FOO>) = <BAR>
> 
> Fixes: c89359a42e2a4 ("mpls: support for dead routes")
> Signed-off-by: David Ahern <dsa@cumulusnetworks.com>

Applied.