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From:   Shenwei Wang <shenwei.wang@nxp.com>
To:     Andrew Lunn <andrew@lunn.ch>
CC:     "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Jesper Dangaard Brouer <hawk@kernel.org>,
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        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        John Fastabend <john.fastabend@gmail.com>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "imx@lists.linux.dev" <imx@lists.linux.dev>
Subject: RE: [EXT] Re: [PATCH v4 1/2] net: page_pool: export page_pool_stats
 definition
Thread-Topic: [EXT] Re: [PATCH v4 1/2] net: page_pool: export page_pool_stats
 definition
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Date:   Tue, 15 Nov 2022 17:18:48 +0000
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> -----Original Message-----
> From: Andrew Lunn <andrew@lunn.ch>
> Sent: Tuesday, November 15, 2022 11:12 AM
> To: Shenwei Wang <shenwei.wang@nxp.com>
> Cc: David S. Miller <davem@davemloft.net>; Eric Dumazet
> <edumazet@google.com>; Jakub Kicinski <kuba@kernel.org>; Paolo Abeni
> <pabeni@redhat.com>; Jesper Dangaard Brouer <hawk@kernel.org>; Ilias
> Apalodimas <ilias.apalodimas@linaro.org>; Alexei Starovoitov
> <ast@kernel.org>; Daniel Borkmann <daniel@iogearbox.net>; John Fastabend
> <john.fastabend@gmail.com>; netdev@vger.kernel.org; linux-
> kernel@vger.kernel.org; imx@lists.linux.dev
> Subject: [EXT] Re: [PATCH v4 1/2] net: page_pool: export page_pool_stats
> definition
>=20
> Caution: EXT Email
>=20
> On Tue, Nov 15, 2022 at 09:57:43AM -0600, Shenwei Wang wrote:
> > The definition of the 'struct page_pool_stats' is required even when
> > the CONFIG_PAGE_POOL_STATS is not defined. Otherwise, it is required
> > the drivers to handle the case of CONFIG_PAGE_POOL_STATS undefined.
>=20
> I agree the API is broken, but i think there is a better fix.
>=20
> There should be a stub of page_pool_get_stats() for when
> CONFIG_PAGE_POOL_STATS is disabled.
>=20
> Nothing actually dereferences struct page_pool_stats when you have this s=
tub.
> So it might be enough to simply have
>=20
> struct page_pool_stats{
> };
>=20

As the structure is open when the CONFIG_PAGE_POOL_STATS is enabled, you ca=
n not
prevent a user to access its members. The empty stub will still have proble=
ms in this
kind of situations.

Regards,
Shenwei

>        Andrew