netdev - RE: [PATCH bpf-next v2 1/2] xdp: Move devmap bulk queue into struct net

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Date:   Wed, 15 Jan 2020 11:45:20 -0800
From:   John Fastabend <john.fastabend@...il.com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>,
        netdev@...r.kernel.org
Cc:     bpf@...r.kernel.org, Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        David Miller <davem@...emloft.net>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Björn Töpel <bjorn.topel@...il.com>,
        John Fastabend <john.fastabend@...il.com>
Subject: RE: [PATCH bpf-next v2 1/2] xdp: Move devmap bulk queue into struct
 net_device

Toke Høiland-Jørgensen wrote:
> From: Toke Høiland-Jørgensen <toke@...hat.com>
> 
> Commit 96360004b862 ("xdp: Make devmap flush_list common for all map
> instances"), changed devmap flushing to be a global operation instead of a
> per-map operation. However, the queue structure used for bulking was still
> allocated as part of the containing map.
> 
> This patch moves the devmap bulk queue into struct net_device. The
> motivation for this is reusing it for the non-map variant of XDP_REDIRECT,
> which will be changed in a subsequent commit.  To avoid other fields of
> struct net_device moving to different cache lines, we also move a couple of
> other members around.
> 
> We defer the actual allocation of the bulk queue structure until the
> NETDEV_REGISTER notification devmap.c. This makes it possible to check for
> ndo_xdp_xmit support before allocating the structure, which is not possible
> at the time struct net_device is allocated. However, we keep the freeing in
> free_netdev() to avoid adding another RCU callback on NETDEV_UNREGISTER.
> 
> Because of this change, we lose the reference back to the map that
> originated the redirect, so change the tracepoint to always return 0 as the
> map ID and index. Otherwise no functional change is intended with this
> patch.
> 
> Acked-by: Björn Töpel <bjorn.topel@...el.com>
> Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
> ---

LGTM. I didn't check the net_device layout with pahole though so I'm
trusting they are good from v1 discussion.

Acked-by: John Fastabend <john.fastabend@...il.com>