Re: [PATCH net/for-next V1 1/1] IB/ipoib: break linkage to neighbouring system

[Or Gerlitz <or.gerlitz@gmail.com>]

On Thu, Jul 19, 2012 at 4:18 PM, Or Gerlitz <ogerlitz@mellanox.com> wrote:
> From: Shlomo Pongratz <shlomop@mellanox.com>
>
> Dave Miller <davem@davemloft.net> provided a detailed description of why the
> way IPoIB is using neighbours for its own ipoib_neigh struct is buggy:
[...]

> This patch aims to solve the race conditions found in the IPoIB driver.
>
> The patch breaks the connection between the core networking neighbour structure
> and the ipoib_neigh structure. Except for avoiding the race, it allows to in
> under a setup where SKBs carrying IP packets that don't have any associated
> neighbour are transmitted through IPoIB.
>
> We add an ipoib_neigh hash table with 1024 buckets. The hash table key is the destin
> hardware address. Thus the ipoib_neigh is fetched from the hash table and not
> dereferenced from the stashed location at the neighbour structure. The hash table uses
> both RCU and reference count mechanisms to guarantee that no ipoib_neigh instance is
> ever deleted while in use.
>
> Fetching the ipoib_neigh structure instance from the hash also makes the special
> code in ipoib_start_xmit that handles remote and local bonding failover redundant.
>
> Aged ipoib_neigh instances are deleted by a garbage collection task that runs every
> 30 seconds and deletes every ipoib_neigh instance that was idle for at least 60
> seconds. The deletion is safe since the ipoib_neigh instances are protected
> using RCU and reference count mechanisms.

Hi Dave, Roland, Eric

So how does this look? in the right direction? anything that need to be fixed?

Or.