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Date: Tue, 27 Feb 2024 15:37:11 +0000
From: Matthew Wilcox <willy@infradead.org>
To: Alice Ryhl <aliceryhl@google.com>
Cc: 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>,
	=?iso-8859-1?Q?Bj=F6rn?= Roy Baron <bjorn3_gh@protonmail.com>,
	Benno Lossin <benno.lossin@proton.me>,
	Andreas Hindborg <a.hindborg@samsung.com>,
	Kees Cook <keescook@chromium.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Andrew Morton <akpm@linux-foundation.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Arve =?iso-8859-1?B?SGr4bm5lduVn?= <arve@android.com>,
	Todd Kjos <tkjos@android.com>, Martijn Coenen <maco@android.com>,
	Joel Fernandes <joel@joelfernandes.org>,
	Carlos Llamas <cmllamas@google.com>,
	Suren Baghdasaryan <surenb@google.com>,
	Arnd Bergmann <arnd@arndb.de>, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org,
	Christian Brauner <brauner@kernel.org>
Subject: Re: [PATCH v2 4/4] rust: add abstraction for `struct page`
Message-ID: <Zd4Bp6ohjb7H9poA@casper.infradead.org>
References: <20240208-alice-mm-v2-0-d821250204a6@google.com>
 <20240208-alice-mm-v2-4-d821250204a6@google.com>
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On Thu, Feb 08, 2024 at 03:47:54PM +0000, Alice Ryhl wrote:
> +impl Page {
> +    /// Allocates a new page.
> +    pub fn new() -> Result<Self, AllocError> {
> +        // SAFETY: These are the correct arguments to allocate a single page.
> +        let page = unsafe {
> +            bindings::alloc_pages(
> +                bindings::GFP_KERNEL | bindings::__GFP_ZERO | bindings::__GFP_HIGHMEM,

I thought I raised this last time, but this is over-specialised for
Binder's purposes.  Many places that want to allocate a page want
different GFP flags from this; they shouldn't even be the default flags.
So either what you're defining here is a BinderPage, or new() needs
to take GFP flags.