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From: Alice Ryhl <aliceryhl@google.com>
Date: Tue, 30 Jan 2024 10:06:09 +0100
Message-ID: <CAH5fLghoxdAQaWRpDpn32A5YUM20oW=7Vck1fPUz1rk5ruH_AA@mail.gmail.com>
Subject: Re: [PATCH 3/3] rust: add abstraction for `struct page`
To: Andreas Hindborg <a.hindborg@samsung.com>
Cc: Matthew Wilcox <willy@infradead.org>, Miguel Ojeda <ojeda@kernel.org>, 
	Alex Gaynor <alex.gaynor@gmail.com>, Wedson Almeida Filho <wedsonaf@gmail.com>, 
	Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>, 
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	Al Viro <viro@zeniv.linux.org.uk>, Andrew Morton <akpm@linux-foundation.org>, 
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>, =?UTF-8?B?QXJ2ZSBIasO4bm5ldsOlZw==?= <arve@android.com>, 
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	Suren Baghdasaryan <surenb@google.com>, Arnd Bergmann <arnd@arndb.de>, 
	"linux-mm@kvack.org" <linux-mm@kvack.org>, 
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, 
	"rust-for-linux@vger.kernel.org" <rust-for-linux@vger.kernel.org>, Christian Brauner <brauner@kernel.org>
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On Tue, Jan 30, 2024 at 10:02=E2=80=AFAM Andreas Hindborg
<a.hindborg@samsung.com> wrote:
>
>
> Matthew Wilcox <willy@infradead.org> writes:
>
> > On Wed, Jan 24, 2024 at 11:20:23AM +0000, Alice Ryhl wrote:
> >> +impl Page {
> >> +    /// Allocates a new set of contiguous pages.
> >> +    pub fn new() -> Result<Self, AllocError> {
> >> +        // SAFETY: These are the correct arguments to allocate a sing=
le page.
> >> +        let page =3D unsafe {
> >> +            bindings::alloc_pages(
> >> +                bindings::GFP_KERNEL | bindings::__GFP_ZERO | binding=
s::__GFP_HIGHMEM,
> >> +                0,
> >> +            )
> >> +        };
> >
> > This feels too Binder-specific to be 'Page'.  Pages are not necessarily
> > allocated with GFP_HIGHMEM, nor are they necessarily zeroed.  Maybe you
> > want a BinderPage type?
>
> Rust null block uses the same definition of these flags [1], so there is
> at least that synergy.
>
> I feel like we had the discussion of the flags before, although I can't
> find the thread now. I think the conclusion was that we fix them until
> we have code that need to actually change them (as to not add dead
> code).

I don't think there's any problem with replacing the constructor with
one that takes a flag argument dead-code-wise. I can definitely do
that.

Alice