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rust: page: add Rust version of PAGE_ALIGN

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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 fc6e66f469 ("rust: add
abstraction for `struct page`").

Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20241016-page-align-v2-1-e0afe85fc4b4@google.com
[ Added intra-doc links, formatted comment and replaced "Brackets" with
  "Parentheses" as discussed in the list. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
This commit is contained in:
Alice Ryhl 2024-10-16 11:34:25 +00:00 committed by Miguel Ojeda
parent d4d7c05f96
commit 6e86292f21
1 changed files with 10 additions and 0 deletions
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10
rust/kernel/page.rs
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@ -20,6 +20,16 @@
/// 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 {
// Parentheses around `PAGE_SIZE - 1` to avoid triggering overflow sanitizers in the wrong
// cases.
(addr + (PAGE_SIZE - 1)) & PAGE_MASK
}
/// A pointer to a page that owns the page allocation.
///
/// # Invariants