From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3101C211710; Wed, 19 Mar 2025 19:14:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742411652; cv=none; b=UJr/EJJDieUh60YDpo3jOISOTmjvvJppurb6adsBl0Eormm6hR3i/hkfL+0FOi7wShH3B/910Wml1zraD2rOlRhcpUYRtXtfhGfQR1MCSqsWdCoyGzp085xwQWYoTBZXW33xZPcS+A87pXoa6HZkCvdSORuYjfmdZleF5K7W/qM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742411652; c=relaxed/simple; bh=Nf5X+seE6wNfFMoZueZ+SLUM5hVg0Q+PrIZTOAXNZZ8=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=fb7L7jK6ZP3ZuX03nYJVin6l52krOJCxWEzaCmCT3P3r0nJELz/E6aGvUw7949/5P4HBU8alQ5biIy/uQRrMv8GPjGvRRMu5mVXLZakel0Aik0093U6CHyn1U4KLRn+UBCOTPowwBsQP9mNbCUtmX1iit5FX8YXrhMRz4BOdE9c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fTk0UqF7; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="fTk0UqF7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 585D1C4CEE4; Wed, 19 Mar 2025 19:14:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1742411651; bh=Nf5X+seE6wNfFMoZueZ+SLUM5hVg0Q+PrIZTOAXNZZ8=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=fTk0UqF73i6ZbbJPkncCGndt9O00HCdKTrw/w5Pv5xLtu9Plt77/y73wiFRpbB/ym ozqdfubSymqX+zDiDWRV84CN8S8iTSjqy0dFmHOzZTQL7tmRr3rdQonhYIJBW/Ra0+ R0evCa3yP6FGunwlfzsBhX/IwyYk7+HsXmQfy6X+/ClZ4hpgyajJPoZE7CO8LhnQeu ORrQ+F30lte/AN75xeCU2r+DSS3HxjCBl3JvzpWXHdYzomHJnBJIqCTaqfrVOcj4j8 DVPMAlAG9QvKEQ3caOTj173RpyK+Y4gkmLSkEuaBKqY8Z7N1UXJ62UxdhDX9dWAqsp grnUkIq1qvxHQ== From: Andreas Hindborg To: "Christian Schrefl" Cc: "Alice Ryhl" , "Greg Kroah-Hartman" , "Alexander Viro" , "Arnd Bergmann" , "Miguel Ojeda" , "Boqun Feng" , "Gary Guo" , =?utf-8?Q?Bj=C3=B6rn?= Roy Baron , "Benno Lossin" , "Trevor Gross" , "Danilo Krummrich" , "Matthew Maurer" , "Lee Jones" , , Subject: Re: [PATCH 2/5] rust: iov: add iov_iter abstractions for ITER_DEST In-Reply-To: <439baec2-dba8-4dab-abb5-faa14fbda943@gmail.com> (Christian Schrefl's message of "Tue, 18 Mar 2025 21:13:01 +0100") References: <20250311-iov-iter-v1-0-f6c9134ea824@google.com> <20250311-iov-iter-v1-2-f6c9134ea824@google.com> <439baec2-dba8-4dab-abb5-faa14fbda943@gmail.com> User-Agent: mu4e 1.12.7; emacs 29.4 Date: Wed, 19 Mar 2025 20:14:00 +0100 Message-ID: <87v7s4g7ev.fsf@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain "Christian Schrefl" writes: > Hi Alice > > On 11.03.25 3:25 PM, Alice Ryhl wrote: >> 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, and that you can make a copy of it to >> get two IO vectors into the same buffers. >> >> Signed-off-by: Alice Ryhl >> --- >> rust/kernel/iov.rs | 140 ++++++++++++++++++++++++++++++++++++++++++++++++++++- >> 1 file changed, 139 insertions(+), 1 deletion(-) >> >> diff --git a/rust/kernel/iov.rs b/rust/kernel/iov.rs >> index 4498f65e1f65bd964909810c020db3a9f8fae389..dc32c27c5c76d059562fd7c6b9d4b178a8ea7c81 100644 >> --- a/rust/kernel/iov.rs >> +++ b/rust/kernel/iov.rs >> @@ -7,7 +7,12 @@ >> //! C headers: [`include/linux/iov_iter.h`](srctree/include/linux/iov_iter.h), >> //! [`include/linux/uio.h`](srctree/include/linux/uio.h) >> >> -use crate::{bindings, prelude::*, types::Opaque}; >> +use crate::{ >> + alloc::{Allocator, Flags}, >> + bindings, >> + prelude::*, >> + types::Opaque, >> +}; >> use core::{marker::PhantomData, mem::MaybeUninit, slice}; >> >> const ITER_SOURCE: bool = bindings::ITER_SOURCE != 0; >> @@ -168,3 +173,136 @@ fn clone(&self) -> IovIterSource<'data> { >> unsafe { core::ptr::read(self) } >> } >> } >> + >> +/// An IO vector that acts as a destination for data. >> +/// >> +/// # Invariants >> +/// >> +/// Must hold a valid `struct iov_iter` with `data_source` set to `ITER_DEST`. The buffers >> +/// referenced by the IO vector must be valid for writing for the duration of `'data`. >> +/// >> +/// Note that if the IO vector is backed by a userspace pointer, it is always considered valid for >> +/// writing. >> +#[repr(transparent)] >> +pub struct IovIterDest<'data> { >> + iov: Opaque, >> + /// Represent to the type system that this value contains a pointer to writable data it does >> + /// not own. >> + _source: PhantomData<&'data mut [u8]>, >> +} > > It might be a bit nicer to add a (private) struct 'IovIter' that implements the common operations. > Then 'IovIterDest' and 'IovIterSource' could store that struct and forward the implementations to > it. > But I'm not sure if that's really much better. Yea, I was thinking the same. Maybe we could have an `IovInner` and a local `AsIovInner` trait that would give all the shared methods? I am sure Alice knows the idiomatic way to achieve code sharing here. Best regards, Andreas Hindborg