Re: [PATCH v6] rust: Return Option from page_align and ensure no usize overflow

[Brendan Shephard <bshephar@bne-home.net>]

On Wed, Dec 03, 2025 at 07:39:06PM +0900, Alexandre Courbot wrote:
> On Tue Dec 2, 2025 at 6:35 PM JST, Brendan Shephard wrote:
> > Change `page_align()` to return `Option<usize>` to allow validation
> > of the provided `addr` value. This ensures that any value that is
> > within one `PAGE_SIZE` of `usize::MAX` will not panic, and instead
> > returns `None` to indicate overflow.
> >
> > Signed-off-by: Brendan Shephard <bshephar@bne-home.net>
> 
> Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
> 
> A few nits below.
> 
> > +/// Returns [`None`] on integer overflow.
> > +///
> > +/// # Examples
> > +///
> > +/// ```rust
> 
> I never see the language specified in other doctests. I guess it doesn't
> hurt, but just mentioning it for consistency.
> 
Fair, I just took this from the example on the rustdocs page:
https://doc.rust-lang.org/rustdoc/write-documentation/documentation-tests.html

And I didn't give it much additional thought. But I probably should have
confirmed formatting of other examples in the project.

> > +/// use kernel::page::{page_align, PAGE_SIZE};
> > +/// // Case 1: Already aligned
> 
> Why number the examples? It doesn't add anything since we don't refer to
> them later.
> 

Another valid point. I think a common theme in my reviews is that I'm
being a bit too verbose. Most of it, like in this case comes from my own
internal monologue while I'm figuring it out. I'll take that on-board
and try to be more INFO and less DEBUG moving forward.