On 10/15/24 8:33 PM, Boqun Feng wrote:
On Tue, Oct 15, 2024 at 02:28:28PM +0000, 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`").
Signed-off-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>
---
rust/kernel/page.rs | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/rust/kernel/page.rs b/rust/kernel/page.rs
index 208a006d587c..90846e3fe829 100644
--- a/rust/kernel/page.rs
+++ b/rust/kernel/page.rs
@@ -20,6 +20,11 @@
/// A bitmask that gives the page containing a given address.
pub const PAGE_MASK: usize = !(PAGE_SIZE - 1);
+/// Round up the given number to a multiple of `PAGE_SIZE`.
+pub fn page_align(addr: usize) -> usize {
Make it a `const` function? For example, there is a VMBUS_RING_SIZE()
macro in C that calculates a const number for a vmbus ringbuffer size,
so it will be useful.
Good idea.
+ (addr + (PAGE_SIZE - 1)) & PAGE_MASK
I guess overflows are unexpected, i.e. the users should not pass a
`addr` that `> usize::MAX - PAGE_SIZE + 1`?
Correct. If this wraps around to zero, that's incorrect. Note that the
minus one is in brackets to only trigger overflow detection in the right
cases.
I can mention this in the docs.
Alice
