Re: [PATCH 1/2] rust: alloc: replace `Vec::set_len` with `inc_len`

Alice Ryhl
2025-03-17T10:50:18Z

On Sun, Mar 16, 2025 at 06:32:00PM -0400, Tamir Duberstein wrote:
> Rename `set_len` to `inc_len` and simplify its safety contract.

You're missing a Signed-off-by tag.

> rust/kernel/alloc/kvec.rs | 19 +++++++++----------
> rust/kernel/str.rs | 2 +-
> rust/kernel/uaccess.rs | 2 +-
> 3 files changed, 11 insertions(+), 12 deletions(-)
>
> diff --git a/rust/kernel/alloc/kvec.rs b/rust/kernel/alloc/kvec.rs
> index ae9d072741ce..d43a1d609434 100644
> --- a/rust/kernel/alloc/kvec.rs
> +++ b/rust/kernel/alloc/kvec.rs
> @@ -183,17 +183,16 @@ pub fn len(&self) -> usize {
> self.len
> }
>
> - /// Forcefully sets `self.len` to `new_len`.
> + /// Increments `self.len` by `additional`.
> ///
> /// # Safety
> ///
> - /// - `new_len` must be less than or equal to [`Self::capacity`].
> - /// - If `new_len` is greater than `self.len`, all elements within the interval
> - /// [`self.len`,`new_len`) must be initialized.
> + /// - `self.len + additional` must be less than or equal to [`Self::capacity`].
> + /// - All elements within the interval [`self.len`,`self.len + additional`) must be initialized.
> #[inline]
> - pub unsafe fn set_len(&mut self, new_len: usize) {
> - debug_assert!(new_len <= self.capacity());
> - self.len = new_len;
> + pub unsafe fn inc_len(&mut self, additional: usize) {
> + debug_assert!(self.len() + additional <= self.capacity());
> + self.len += additional;

I guess we could use an INVARIANT: comment here.

Alice