linux-kernel - Re: [PATCH] rust: alloc: add __GFP

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Message-ID: <CANiq72kO2rpPBf0Gxfqmt7cUMMsrH9kx0==63rthwXQD3fgAqw@mail.gmail.com>
Date: Tue, 9 Jul 2024 09:55:18 +0200
From: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: Miguel Ojeda <ojeda@...nel.org>, Matthew Wilcox <willy@...radead.org>, 
	Al Viro <viro@...iv.linux.org.uk>, Andrew Morton <akpm@...ux-foundation.org>, 
	Kees Cook <keescook@...omium.org>, Alex Gaynor <alex.gaynor@...il.com>, 
	Wedson Almeida Filho <wedsonaf@...il.com>, Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, 
	Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
	Benno Lossin <benno.lossin@...ton.me>, Andreas Hindborg <a.hindborg@...sung.com>, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org
Subject: Re: [PATCH] rust: alloc: add __GFP_HIGHMEM flag

On Fri, Jun 7, 2024 at 10:23 AM Alice Ryhl <aliceryhl@...gle.com> wrote:
>
> Make it possible to allocate memory that doesn't need to mapped into the
> kernel's address space. This flag is useful together with
> Page::alloc_page [1].
>
> Rust Binder needs this for the memory that holds incoming transactions
> for each process. Each process will have a few megabytes of memory
> allocated with this flag, which is mapped into the process using
> vm_insert_page. When the kernel copies data for an incoming transaction
> into a process's memory region, it will use kmap_local_page to
> temporarily map pages that are being modified. There is no need for them
> to take up address space in the kernel when the kernel is not writing an
> incoming transaction into the page.
>
> Link: https://lore.kernel.org/all/20240528-alice-mm-v7-4-78222c31b8f4@google.com/ [1]
> Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>

Applied to `rust-next`, thanks!

Cheers,
Miguel