Re: [PATCH v5 3/7] rust: alloc: add Vec::push_within_capacity

Alice Ryhl
2025-05-02T14:25:15Z

On Fri, May 2, 2025 at 4:07 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Fri, May 02, 2025 at 01:19:31PM +0000, Alice Ryhl wrote:
> > This introduces a new method called `push_within_capacity` for appending
> > to a vector without attempting to allocate if the capacity is full. Rust
> > Binder will use this in various places to safely push to a vector while
> > holding a spinlock.
> >
> > The implementation is moved to a push_within_capacity_unchecked method.
> > This is preferred over having push() call push_within_capacity()
> > followed by an unwrap_unchecked() for simpler unsafe.
> >
> > Panics in the kernel are best avoided when possible, so an error is
> > returned if the vector does not have sufficient capacity. An error type
> > is used rather than just returning Result<(),T> to make it more
> > convenient for callers (i.e. they can use ? or unwrap).
> >
> > Signed-off-by: Alice Ryhl <aliceryhl@google.com>
> > + /// Appends an element to the back of the [`Vec`] instance without reallocating.
> > + ///
> > + /// # Safety
> > + ///
> > + /// The length must be less than the capacity.
> > + pub unsafe fn push_within_capacity_unchecked(&mut self, v: T) {
>
> Why does this have to be public? Does binder need to call this instead
> of just push_within_capacity()?

It does not need to be public.

Alice