netdev - Re: [PATCH v2 net-next 04/10] net: switchdev: remove the transaction structure from port attributes

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Date:   Wed, 6 Jan 2021 19:47:23 +0200
From:   Ido Schimmel <idosch@...sch.org>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Kurt Kanzenbach <kurt@...utronix.de>,
        Hauke Mehrtens <hauke@...ke-m.de>,
        Woojung Huh <woojung.huh@...rochip.com>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Vadym Kochan <vkochan@...vell.com>,
        Taras Chornyi <tchornyi@...vell.com>,
        Jiri Pirko <jiri@...dia.com>, Ido Schimmel <idosch@...dia.com>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        Ivan Vecera <ivecera@...hat.com>
Subject: Re: [PATCH v2 net-next 04/10] net: switchdev: remove the transaction
 structure from port attributes

On Wed, Jan 06, 2021 at 03:10:00PM +0200, Vladimir Oltean wrote:
> From: Vladimir Oltean <vladimir.oltean@....com>
> 
> Since the introduction of the switchdev API, port attributes were
> transmitted to drivers for offloading using a two-step transactional
> model, with a prepare phase that was supposed to catch all errors, and a
> commit phase that was supposed to never fail.
> 
> Some classes of failures can never be avoided, like hardware access, or
> memory allocation. In the latter case, merely attempting to move the
> memory allocation to the preparation phase makes it impossible to avoid
> memory leaks, since commit 91cf8eceffc1 ("switchdev: Remove unused
> transaction item queue") which has removed the unused mechanism of
> passing on the allocated memory between one phase and another.
> 
> It is time we admit that separating the preparation from the commit
> phase is something that is best left for the driver to decide, and not
> something that should be baked into the API, especially since there are
> no switchdev callers that depend on this.
> 
> This patch removes the struct switchdev_trans member from switchdev port
> attribute notifier structures, and converts drivers to not look at this
> member.
> 
> In part, this patch contains a revert of my previous commit 2e554a7a5d8a
> ("net: dsa: propagate switchdev vlan_filtering prepare phase to
> drivers").
> 
> For the most part, the conversion was trivial except for:
> - Rocker's world implementation based on Broadcom OF-DPA had an odd
>   implementation of ofdpa_port_attr_bridge_flags_set. The conversion was
>   done mechanically, by pasting the implementation twice, then only
>   keeping the code that would get executed during prepare phase on top,
>   then only keeping the code that gets executed during the commit phase
>   on bottom, then simplifying the resulting code until this was obtained.
> - DSA's offloading of STP state, bridge flags, VLAN filtering and
>   multicast router could be converted right away. But the ageing time
>   could not, so a shim was introduced and this was left for a further
>   commit.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> Acked-by: Linus Walleij <linus.walleij@...aro.org>
> Acked-by: Jiri Pirko <jiri@...dia.com>
> Reviewed-by: Kurt Kanzenbach <kurt@...utronix.de> # hellcreek
> Reviewed-by: Linus Walleij <linus.walleij@...aro.org> # RTL8366RB

Reviewed-by: Ido Schimmel <idosch@...dia.com>