linux-kernel - Re: [PATCH v3 2/2] rust: support align and NUMA id in allocations

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Message-ID: <aFv11ORZDmM7g6S-@Mac.home>
Date: Wed, 25 Jun 2025 06:12:52 -0700
From: Boqun Feng <boqun.feng@...il.com>
To: Vitaly Wool <vitaly.wool@...sulko.se>
Cc: linux-mm@...ck.org, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, Uladzislau Rezki <urezki@...il.com>,
	Danilo Krummrich <dakr@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>, rust-for-linux@...r.kernel.org
Subject: Re: [PATCH v3 2/2] rust: support align and NUMA id in allocations

On Wed, Jun 25, 2025 at 08:30:26AM +0200, Vitaly Wool wrote:
[...]
> @@ -151,16 +159,11 @@ unsafe fn realloc(
>          layout: Layout,
>          old_layout: Layout,
>          flags: Flags,
> +        nid: Option<i32>,
>      ) -> Result<NonNull<[u8]>, AllocError> {
> -        // TODO: Support alignments larger than PAGE_SIZE.

Thanks a lot for doing this! While you're at it, maybe we can add a few
tests for various alignments of allocation? I'm thinking:

#[repr(align(65536)]
pub struct Test64k {
    a: i32
}

#[kunit_tests(rust_vbox)]
mod tests {
    #[test]
    fn large_allocation() -> Result {
        // Better use `new_uninit()` to avoid allocation on the stack.
        let x = VBox::<Test64k>::new_uninit(...)?;

	assert!(x.as_ptr().addr() & (kernel::sizes::SZ_64K - 1) == 0);
    }
}

Thoughts?

Regards,
Boqun

> -        if layout.align() > bindings::PAGE_SIZE {
> -            pr_warn!("Vmalloc does not support alignments larger than PAGE_SIZE yet.\n");
> -            return Err(AllocError);
> -        }
> -
>          // SAFETY: If not `None`, `ptr` is guaranteed to point to valid memory, which was previously
>          // allocated with this `Allocator`.
> -        unsafe { ReallocFunc::VREALLOC.call(ptr, layout, old_layout, flags) }
> +        unsafe { ReallocFunc::VREALLOC.call(ptr, layout, old_layout, flags, nid) }
>      }
>  }
>  
[...]