netdev - Re: [patch net-next v4 5/7] bridge: defer switchdev fdb del call in fdb_del_external

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Date:	Mon, 12 Oct 2015 20:28:20 -0700
From:	Scott Feldman <sfeldma@...il.com>
To:	Jiri Pirko <jiri@...nulli.us>
Cc:	Netdev <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Ido Schimmel <idosch@...lanox.com>,
	Elad Raz <eladr@...lanox.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
	"andrew@...n.ch" <andrew@...n.ch>,
	john fastabend <john.fastabend@...il.com>,
	David Laight <David.Laight@...lab.com>,
	"stephen@...workplumber.org" <stephen@...workplumber.org>
Subject: Re: [patch net-next v4 5/7] bridge: defer switchdev fdb del call in fdb_del_external_learn

On Mon, Oct 12, 2015 at 11:03 AM, Jiri Pirko <jiri@...nulli.us> wrote:
> From: Jiri Pirko <jiri@...lanox.com>
>
> Since spinlock is held here, defer the switchdev operation.
>
> Signed-off-by: Jiri Pirko <jiri@...lanox.com>
> ---
>  net/bridge/br_fdb.c | 5 ++++-
>  net/bridge/br_if.c  | 3 +++
>  2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
> index f5e7da0..c88bd8e 100644
> --- a/net/bridge/br_fdb.c
> +++ b/net/bridge/br_fdb.c
> @@ -134,7 +134,10 @@ static void fdb_del_hw_addr(struct net_bridge *br, const unsigned char *addr)
>  static void fdb_del_external_learn(struct net_bridge_fdb_entry *f)
>  {
>         struct switchdev_obj_port_fdb fdb = {
> -               .obj.id = SWITCHDEV_OBJ_ID_PORT_FDB,
> +               .obj = {
> +                       .id = SWITCHDEV_OBJ_ID_PORT_FDB,
> +                       .flags = SWITCHDEV_F_DEFER,
> +               },
>                 .vid = f->vlan_id,
>         };
>
> diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
> index 934cae9..09147cb 100644
> --- a/net/bridge/br_if.c
> +++ b/net/bridge/br_if.c
> @@ -24,6 +24,7 @@
>  #include <linux/slab.h>
>  #include <net/sock.h>
>  #include <linux/if_vlan.h>
> +#include <net/switchdev.h>
>
>  #include "br_private.h"
>
> @@ -249,6 +250,8 @@ static void del_nbp(struct net_bridge_port *p)
>         list_del_rcu(&p->list);
>
>         br_fdb_delete_by_port(br, p, 0, 1);
> +       switchdev_flush_deferred();
> +

This potentially flushes other (valid) work on the deferred queue not
related to FDB del.

I wonder if this flush step is necessary at all?  The work we deferred
to delete the FDB entry can still happen after the port has been
removed (del_nbp).  If the port driver/device find the FDB entry, then
delete it, otherwise ignore it.
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