linux-kernel - Re: [PATCH v2 1/4] rust: iov: add iov_iter abstractions for ITER

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Message-ID: <874ium9h7v.fsf@kernel.org>
Date: Tue, 05 Aug 2025 12:48:52 +0200
From: Andreas Hindborg <a.hindborg@...nel.org>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Alexander Viro
 <viro@...iv.linux.org.uk>, Arnd Bergmann <arnd@...db.de>, Miguel Ojeda
 <ojeda@...nel.org>, Boqun Feng <boqun.feng@...il.com>, Gary Guo
 <gary@...yguo.net>, Björn Roy Baron
 <bjorn3_gh@...tonmail.com>, Trevor
 Gross <tmgross@...ch.edu>, Danilo
 Krummrich <dakr@...nel.org>, Matthew Maurer <mmaurer@...gle.com>, Lee
 Jones <lee@...nel.org>, linux-kernel@...r.kernel.org,
 rust-for-linux@...r.kernel.org, Benno Lossin <lossin@...nel.org>
Subject: Re: [PATCH v2 1/4] rust: iov: add iov_iter abstractions for
 ITER_SOURCE

"Alice Ryhl" <aliceryhl@...gle.com> writes:

> On Wed, Jul 09, 2025 at 07:05:01PM +0200, Andreas Hindborg wrote:
>> "Alice Ryhl" <aliceryhl@...gle.com> writes:
>>
>> > On Wed, Jul 09, 2025 at 01:56:37PM +0200, Andreas Hindborg wrote:
>> >> "Alice Ryhl" <aliceryhl@...gle.com> writes:
>> >>
>> >> > On Tue, Jul 08, 2025 at 04:45:14PM +0200, Andreas Hindborg wrote:
>> >> >> "Alice Ryhl" <aliceryhl@...gle.com> writes:
> The iov_iter type is like a giant enum with a bunch of different
> implementations. Some implementations just read from a simple kernel
> buffer that must, of course, be mapped. Some implementations traverse
> complex data structures and stitch the data together from multiple
> buffers. Other implementations map the data into memory on-demand inside
> the copy_from_iter call, without requiring it to be mapped at other
> times. And finally, some implementations perform IO by reading from
> userspace, in which case it's valid for the userspace pointer to be
> *literally any 64-bit integer*. If the address is dangling, that's
> caught inside the call to copy_from_iter and is not a safety issue.

At any rate, this is a very informative paragraph. It would be great if
you could have this information in the documentation for this type.


Best regards,
Andreas Hindborg