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Date: Tue, 15 Jul 2025 12:21:49 +0200
Message-Id: <DBCJYEIGYQIG.2E341O2W3LX2S@kernel.org>
Subject: Re: [PATCH 0/3] rust: allocator: Vmalloc: Support alignments larger
 than PAGE_SIZE
Cc: "Andrew Morton" <akpm@linux-foundation.org>, "Uladzislau Rezki"
 <urezki@gmail.com>, "Miguel Ojeda" <ojeda@kernel.org>, "Alex Gaynor"
 <alex.gaynor@gmail.com>, "Boqun Feng" <boqun.feng@gmail.com>, "Gary Guo"
 <gary@garyguo.net>, <bjorn3_gh@protonmail.com>, "Benno Lossin"
 <lossin@kernel.org>, "Andreas Hindborg" <a.hindborg@kernel.org>, "Alice
 Ryhl" <aliceryhl@google.com>, "Trevor Gross" <tmgross@umich.edu>, "Geliang
 Tang" <geliang@kernel.org>, "Hui Zhu" <zhuhui@kylinos.cn>,
 <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
 <rust-for-linux@vger.kernel.org>
To: "Hui Zhu" <hui.zhu@linux.dev>
From: "Danilo Krummrich" <dakr@kernel.org>
References: <cover.1752573305.git.zhuhui@kylinos.cn>
In-Reply-To: <cover.1752573305.git.zhuhui@kylinos.cn>

Hi Hui,

On Tue Jul 15, 2025 at 11:59 AM CEST, Hui Zhu wrote:
> From: Hui Zhu <zhuhui@kylinos.cn>
>
> There is a TODO in Vmalloc::realloc "Support alignments larger than
> PAGE_SIZE."
>
> These commits make allocator vmalloc support alignments larger than
> PAGE_SIZE.
> The function vrealloc_align is added to vmalloc.c to support reallocating
> aligned vmap pages.
> When Vmalloc::realloc intends to reallocate memory aligned beyond PAGE_SI=
ZE,
> vrealloc_align should be used instead of vrealloc, thus enabling support
> for alignments larger than PAGE_SIZE.

Thanks for the patch!

Please note that there is already a rather progressed patch series addressi=
ng
this [1].

However, I'd be interested in your use-case for alignments larger than
PAGE_SIZE. :)

> And add a sample to the samples memory allocator usage.

The example looks a bit odd, more on that in the corresponding patch.

We already have other examples in the form of documentation tests [2]. Not =
all
of them are for VVec, some of them are for KVec and KVVec, however, they al=
l
share the same code, only the allocator backend differs.

If you'd like to introduce additional examples, please do so in the context=
 of
documentation tests in rust/kernel/alloc/kvec.rs.

If you enable CONFIG_RUST_KERNEL_DOCTESTS they're compiled and executed at =
boot
time.

[1] https://lore.kernel.org/lkml/20250709172345.1031907-1-vitaly.wool@konsu=
lko.se/
[2] https://rust.docs.kernel.org/kernel/alloc/kvec/type.VVec.html