linux-kernel - Re: [PATCH v3 0/4] rust: alloc: add Vec shrinking methods

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Message-ID: <CAH5fLgjwWQSHydyM6AMPiziBQjeO4rcNaOzuNV=CrHxRvYuaVw@mail.gmail.com>
Date: Wed, 11 Feb 2026 07:51:16 +0100
From: Alice Ryhl <aliceryhl@...gle.com>
To: Shivam Kalra <shivamkalra98@...il.com>
Cc: Danilo Krummrich <dakr@...nel.org>, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/4] rust: alloc: add Vec shrinking methods

On Wed, Feb 11, 2026 at 2:08 AM Shivam Kalra <shivamkalra98@...il.com> wrote:
>
> On 11/02/26 02:41, Danilo Krummrich wrote:
> > On Tue Feb 10, 2026 at 9:58 PM CET, Alice Ryhl wrote:
> >> On Tue, Feb 10, 2026 at 9:54 PM Danilo Krummrich <dakr@...nel.org> wrote:
> >> Yes that's what I meant. Only provide shrink_to() for those. After
> >> all, if Kmalloc never actually shrinks when you call realloc, what's
> >> the point of having KVec::shrink_to()?
> >
> > Nothing, but eventually we want a generic impl of shrink_to() with A::realloc().
> > But again, for now that's fine.
> Thanks for the discussion. Just want to confirm my understanding
> of the agreed approach:
>
> Since VVec and KVVec are type aliases for Vec<T, Vmalloc> and
> Vec<T, KVmalloc>, implementing shrink_to() on "only VVec and KVVec"
> means writing separate impl blocks:
>
>   impl<T> Vec<T, Vmalloc> { fn shrink_to() { ... } }
>   impl<T> Vec<T, KVmalloc> { fn shrink_to() { ... } }
>
> Is that what you had in mind, with the shrink logic duplicated
> in both? Or would you prefer a shared impl with a trait bound to
> avoid duplication?

I would prefer either a single stand-alone function that both impls
blocks call, or implementing it for KVmalloc only. Trait is overkill
here.

Alice