linux-kernel - Re: [PATCH] rust: Test page_align usize::MAX boundary edges

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Message-ID: <CANiq72mdkb6A82oy0DoUWn=jv75-R7EHTNvJRW7o=JeNa3eeHg@mail.gmail.com>
Date: Tue, 30 Dec 2025 11:14:37 +0100
From: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To: Brendan Shephard <bshephar@...-home.net>
Cc: aliceryhl@...gle.com, lorenzo.stoakes@...cle.com, Liam.Howlett@...cle.com, 
	ojeda@...nel.org, boqun.feng@...il.com, gary@...yguo.net, 
	bjorn3_gh@...tonmail.com, lossin@...nel.org, a.hindborg@...nel.org, 
	tmgross@...ch.edu, dakr@...nel.org, linux-mm@...ck.org, 
	rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rust: Test page_align usize::MAX boundary edges

On Tue, Dec 30, 2025 at 10:55 AM Brendan Shephard <bshephar@...-home.net> wrote:
>
> @miguel, Thanks for the pointers in:
> https://lore.kernel.org/all/CANiq72kcMLXz=xyZeKC0=j_e0BzJEY3wGpBTTxfJsc6EZhCnXA@mail.gmail.com/
> https://lore.kernel.org/rust-for-linux/CANiq72mLPvB_6Ow3bW5-V4-km=RyA59chQ1g1x9qUt2P-zZweg@mail.gmail.com/
>
> Let me know if this addresses the points you were raising in those.
> Maybe you just wanted usize::MAX and then one over? The first test
> case might be unnecessary. The last two do a fine job of illustrating the
> point I think.

Thanks! Yeah, either way looks good to me. Personally, I tend to like
tests that check both edges.

By the way, the original comment mentioned "overflow" explicitly,
which was good since it conceptually links to the main docs which also
mention it. It also seemed more aligned with the other two comments.
Perhaps you changed it since now one of them doesn't return `None`? In
that case, I would just remove that bit e.g.

    // Requested address causes overflow.

i.e. I think it is clear that the first case is not the overflow one.
But it is not a big deal either way.

By the way, in commit messages, we normally don't use paragraphs like:

    This patch is a follow-up of: "[PATCH v8] rust: Return Option from
page_align and ensure no usize overflow"

Instead, it is better to provide a lore.kernel.org permalink to the
patch or, if the patch was already applied, refer directly to the
commit with the hash and title. However, in cases like this where it
is not really important for the change itself, I would just move that
line below the `---` line so that it is not part of the commit
message.

I hope that helps!

Cheers,
Miguel