netdev - Re: RFH: problems with adjacency graph

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Message-ID: <20161011065432.GA2018@nanopsycho>
Date:   Tue, 11 Oct 2016 08:54:32 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     David Ahern <dsahern@...il.com>
Cc:     vfalico@...il.com,
        Nikolay Aleksandrov <nikolay@...ulusnetworks.com>,
        roopa <roopa@...ulusnetworks.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: RFH: problems with adjacency graph

Tue, Oct 11, 2016 at 04:18:52AM CEST, dsahern@...il.com wrote:
>Jiri / Veaceslav:
>
>As author's of the adjacency tracking code in dev.c I am hoping you can help with suggested patches for a couple of problems. The start point needs to include commit 93409033ae65 which resolved a different problem from what I am seeing now.
>
>At the moment I have 2 cases both for this topology:
>        +--------+
>        |  myvrf |
>        +--------+
>          |    |
>          |  +---------+
>          |  | macvlan |
>          |  +---------+
>          |    |
>      +----------+
>      |  bridge  |
>      +----------+
>          |
>      +--------+
>      | bond0  |
>      +--------+
>          |
>      +--------+
>      |  eth3  |
>      +--------+
>
>
>Base set of commands for both cases:
>
>ip link add bond1 type bond
>ip link set bond1 up
>ip link set eth3 down
>ip link set eth3 master bond1
>ip link set eth3 up
>
>ip link add bridge type bridge
>ip link set bridge up
>ip link add macvlan link bridge type macvlan
>ip link set macvlan up
>
>ip link add myvrf type vrf table 1234
>ip link set myvrf up
>
>ip link set bridge master myvrf
>
>
>############################################################
># case 1
>
>ip link set macvlan master myvrf
>ip link set bond1 master bridge
>
>ip link delete myvrf
>
>dmesg has a splat triggered in __netdev_adjacent_dev_remove() where you currently see the BUG(). If you convert that to a WARN_ON (which it should be, no need to panic on the remove path) it will show you 4 missing adjacencies: eth3 - myvrf, mvrf - eth3, bond1 - myvrf and myvrf - bond1. All of those are because the dev_link function does not link macvlan lower devices to myvrf when it is enslaved. (Enable the debugging to see that those messages are missing.)
>
>
>
>############################################################
># case 2
>
>This case just flips the ordering of the enslavements:
>
>ip link set bond1 master bridge
>ip link set macvlan master myvrf
>
>Then run:
>ip link delete bond1
>ip link delete myvrf
>
>The last command hangs because myvrf has a reference that has not been released. If you do not have commit 93409033ae65 the delete of bond1 hangs for the same reason. For this case, the debug messages show that the macvlan lower devices (eth3 and bond1) are connected to myvrf on the enslavement, but the link delete the path only removes one of them hence the unreleased refcnt on myvrf.
>
>
>In the end it seems that the code for the dependency graph is not making the complete mesh which causes problems on the tear down. I have attempted a few changes that so far fix 1 problem and uncover a different one. Hence the request for help from the author's of this code.

Agreed. We need to fix the code to work with duplicates so the graph is
complete.


>
>It seems like the complete mesh is not really needed, but cscope shows spectrum, ixgbe and bonding all using the for_each upper and lower device macros.
>
>Suggestions?

Well other possibility is to traverse the tree recursively. But that is
exactly why the colided lists of all uppers/lowers were introduced to
avoid this.


>
>David