Re: [PATCH v2] rust: page: add Rust version of PAGE_ALIGN

[Alice Ryhl <alice@ryhl.io>]

On 10/21/24 8:20 PM, John Hubbard wrote:
> On 10/16/24 4:34 AM, Alice Ryhl wrote:
>> This is a useful for helper for working with indices into buffers that
>> consist of several pages. I forgot to include it when I added PAGE_SIZE
>> and PAGE_MASK for the same purpose in commit fc6e66f4696b ("rust: add
>> abstraction for `struct page`").
>>
>> Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
>> Signed-off-by: Alice Ryhl <aliceryhl@google.com>
>> ---
>> Changes in v2:
>> - Make the function const.
>> - Address integer overflow in docs.
>> - Link to v1: https://lore.kernel.org/r/20241015-page-align- 
>> v1-1-68fbd8b6d10c@google.com
>> ---
>>   rust/kernel/page.rs | 9 +++++++++
>>   1 file changed, 9 insertions(+)
>>
>> diff --git a/rust/kernel/page.rs b/rust/kernel/page.rs
>> index 208a006d587c..9ef01929e7d0 100644
>> --- a/rust/kernel/page.rs
>> +++ b/rust/kernel/page.rs
>> @@ -20,6 +20,15 @@
>>   /// A bitmask that gives the page containing a given address.
>>   pub const PAGE_MASK: usize = !(PAGE_SIZE - 1);
>> +/// Round up the given number to the next multiple of `PAGE_SIZE`.
>> +///
>> +/// It is incorrect to pass an address where the next multiple of 
>> `PAGE_SIZE` doesn't fit in a
>> +/// `usize`.
>> +pub const fn page_align(addr: usize) -> usize {
>> +    // Brackets around PAGE_SIZE-1 to avoid triggering overflow 
>> sanitizers in the wrong cases.
> 
> Silly nit, but I did start looking for brackets that aren't there, so:
> 
> s/Brackets/parentheses/
This isn't a distinction that exists in my vocabulary, shrug.

Miguel, feel free to reword when you pick this.

Alice