netdev - Re: [PATCH net-next 00/11] net: Fix netdev adjacency tracking

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Message-ID: <eedea44e-24de-e6f7-c42f-a13461d16d6a@cumulusnetworks.com>
Date:   Thu, 13 Oct 2016 08:32:40 -0600
From:   David Ahern <dsa@...ulusnetworks.com>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     jiri@...lanox.com, netdev@...r.kernel.org, davem@...emloft.net,
        dledford@...hat.com, sean.hefty@...el.com,
        hal.rosenstock@...il.com, linux-rdma@...r.kernel.org,
        j.vosburgh@...il.com, vfalico@...il.com, andy@...yhouse.net,
        jeffrey.t.kirsher@...el.com, intel-wired-lan@...ts.osuosl.org
Subject: Re: [PATCH net-next 00/11] net: Fix netdev adjacency tracking

On 10/13/16 1:34 AM, Jiri Pirko wrote:
> 
> Although I didn't like the "all-list" idea when Veaceslav pushed it
> because it looked to me like a big hammer, it turned out to be very handy
> and quick for traversing neighbours. Why it cannot be fixed?
> 
> The walks with possibly hundreds of function calls instead of a single
> list traverse worries me.
> 

I have been looking at this code for a week now. Every solution I came up with that solved the original problems introduced new ones -- usually with adjacency remove expecting an adjacency that did not exist. In the end I came to the conclusion it is not possible to maintain an all_adj_list when the upper tree can have multiple paths to the top device. If someone thinks otherwise I am happy to test a patch.