Re: [PATCH v2 net-next 02/10] net: switchdev: remove the transaction structure from port object notifiers

From: Ido Schimmel <idosch@idosch.org>
To: Vladimir Oltean <olteanv@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	netdev@vger.kernel.org, Florian Fainelli <f.fainelli@gmail.com>,
	Andrew Lunn <andrew@lunn.ch>,
	Vivien Didelot <vivien.didelot@gmail.com>,
	Kurt Kanzenbach <kurt@linutronix.de>,
	Hauke Mehrtens <hauke@hauke-m.de>,
	Woojung Huh <woojung.huh@microchip.com>,
	Microchip Linux Driver Support <UNGLinuxDriver@microchip.com>,
	Sean Wang <sean.wang@mediatek.com>,
	Landen Chao <Landen.Chao@mediatek.com>,
	Claudiu Manoil <claudiu.manoil@nxp.com>,
	Alexandre Belloni <alexandre.belloni@bootlin.com>,
	Linus Walleij <linus.walleij@linaro.org>,
	Vadym Kochan <vkochan@marvell.com>,
	Taras Chornyi <tchornyi@marvell.com>,
	Jiri Pirko <jiri@nvidia.com>, Ido Schimmel <idosch@nvidia.com>,
	Grygorii Strashko <grygorii.strashko@ti.com>,
	Ioana Ciornei <ioana.ciornei@nxp.com>,
	Ivan Vecera <ivecera@redhat.com>
Subject: Re: [PATCH v2 net-next 02/10] net: switchdev: remove the transaction structure from port object notifiers
Date: Wed, 6 Jan 2021 19:42:02 +0200	[thread overview]
Message-ID: <20210106174202.GA1082997@shredder.lan> (raw)
In-Reply-To: <20210106131006.577312-3-olteanv@gmail.com>

On Wed, Jan 06, 2021 at 03:09:58PM +0200, Vladimir Oltean wrote:
> From: Vladimir Oltean <vladimir.oltean@nxp.com>
> 
> Since the introduction of the switchdev API, port objects 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
> object notifier structures, and converts drivers to not look at this
> member.
> 
> Where driver conversion is trivial (like in the case of the Marvell
> Prestera driver, NXP DPAA2 switch, TI CPSW, and Rocker drivers), it is
> done in this patch.
> 
> Where driver conversion needs more attention (DSA, Mellanox Spectrum),
> the conversion is left for subsequent patches and here we only fake the
> prepare/commit phases at a lower level, just not in the switchdev
> notifier itself.
> 
> Where the code has a natural structure that is best left alone as a
> preparation and a commit phase (as in the case of the Ocelot switch),
> that structure is left in place, just made to not depend upon the
> switchdev transactional model.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
> Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
> Acked-by: Linus Walleij <linus.walleij@linaro.org>
> Acked-by: Jiri Pirko <jiri@nvidia.com>

This looks good to me. I think that faking the prepare/commit phase made
it easier to review.

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