Re: [PATCH v3 2/4] rust: iov: add iov_iter abstractions for ITER_DEST

[Alice Ryhl <aliceryhl@google.com>]

On Tue, Aug 5, 2025 at 1:31 PM Andreas Hindborg <a.hindborg@kernel.org> wrote:
>
> "Alice Ryhl" <aliceryhl@google.com> writes:
>
> > This adds abstractions for the iov_iter type in the case where
> > data_source is ITER_DEST. This will make Rust implementations of
> > fops->read_iter possible.
> >
> > This series only has support for using existing IO vectors created by C
> > code. Additional abstractions will be needed to support the creation of
> > IO vectors in Rust code.
> >
> > These abstractions make the assumption that `struct iov_iter` does not
> > have internal self-references, which implies that it is valid to move it
> > between different local variables.
> >
> > This patch adds an IovIterDest struct that is very similar to the
> > IovIterSource from the previous patch. However, as the methods on the
> > two structs have very little overlap (just getting the length and
> > advance/revert), I do not think it is worth it to try and deduplicate
> > this logic.
>
> Is it not like 50% duplication? `as_raw`, `len`, `is_empty`, `advance`,
> `revert`. It looks like it makes sense to me, but 🤷 We can always do it
> later.

Well, maybe. But I think having those be duplicated leads to a simpler
API for the end-user.

> Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>

Thanks!