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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>,
        Ilias Apalodimas <ilias.apalodimas@linaro.org>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        John Fastabend <john.fastabend@gmail.com>,
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        "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 17:52:20 +0000
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> -----Original Message-----
> From: Andrew Lunn <andrew@lunn.ch>
> Sent: Tuesday, November 15, 2022 11:43 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: Re: [EXT] Re: [PATCH v4 1/2] net: page_pool: export page_pool_st=
ats
> definition
>=20
> Caution: EXT Email
>=20
> > > I agree the API is broken, but i think there is a better fix.
> > >
> > > There should be a stub of page_pool_get_stats() for when
> > > CONFIG_PAGE_POOL_STATS is disabled.
> > >
> > > Nothing actually dereferences struct page_pool_stats when you have th=
is
> stub.
> > > So it might be enough to simply have
> > >
> > > struct page_pool_stats{
> > > };
> > >
> >
> > As the structure is open when the CONFIG_PAGE_POOL_STATS is enabled,
> > you can not prevent a user to access its members. The empty stub will
> > still have problems in this kind of situations.
>=20
> The users, i.e. the driver, has no need to access its members. The member=
s can
> change, new ones can be added, and it will not cause a problem, given the=
 way
> this API is defined. Ideally, page_pool_stats would of been an opaque coo=
kie,
> but that is not how it was implemented :-(
>=20

Okay if the assumption is the user would never access its members.

Regards,
Shenwei

>             Andrew