From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 08894E9537B for ; Wed, 4 Feb 2026 11:57:50 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 593C06B00A0; Wed, 4 Feb 2026 06:57:50 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 54A656B00A1; Wed, 4 Feb 2026 06:57:50 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 46A146B00A2; Wed, 4 Feb 2026 06:57:50 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 33B4F6B00A0 for ; Wed, 4 Feb 2026 06:57:50 -0500 (EST) Received: from smtpin25.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id D5B395240A for ; Wed, 4 Feb 2026 11:57:49 +0000 (UTC) X-FDA: 84406625058.25.7E36EA9 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf04.hostedemail.com (Postfix) with ESMTP id 2605740008 for ; Wed, 4 Feb 2026 11:57:47 +0000 (UTC) Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=Itkw+GCN; spf=pass (imf04.hostedemail.com: domain of a.hindborg@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=a.hindborg@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1770206268; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=Tb8JW9JPEachGIm2llkrEDVUyBAPphq8yqh+qpyCAKg=; b=UBg/XcWKX/GJ6EhN5EIemxCcH2iZWqb8yQ2nIveXkJk08CPUD5ePvImZ2CMyNzp3jK/GN8 dQg1Y44NtqOlnPw+pWS2wnLvwyTRac3kOWZhkXtwvRH/25H17za4UTcXEfrwWQyCKcSncS s6F4keV94cA/p8PYet1iwhFVsCmgluM= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1770206268; a=rsa-sha256; cv=none; b=uUN2dwocP+b1lhvdRsQFEXI9mjVM/WVnvOy6Ni5Ro7pz9y7Njws/88yM/ox4ouzAVmcnV5 KWKKfzluC1UA88bT1qm6cG5l7jAF/lbPE9Q0iHVp15NlTU00AcNv2YQ3m6r2ilklcZioFs sqD9Ou+x2l207BDFoBy8Uv2rxuWfVm0= ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=Itkw+GCN; spf=pass (imf04.hostedemail.com: domain of a.hindborg@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=a.hindborg@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 47425437CB; Wed, 4 Feb 2026 11:57:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E7E66C4AF0E; Wed, 4 Feb 2026 11:57:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770206267; bh=xYW/EeCkC7WedEcSi5MqPHN0tL67nyGJDfMj502jbkc=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=Itkw+GCNuRyDWXobTgUJcS0pi6d1d1IBIwP+ooRlXy0f3+lPDetjhnmjZeS9VJgHt r0yLrn7GditsJD2Tm1N1gbCQN9s+9IUvKv+et91wsaWYk3qwciisdi/+iCDbxHrROQ wiNXxV37ZbzioI73sfI7hl2MbwGmKU+oxHIVm/pl4lah4z2qmWPuRA0KZ1Lp1sqJnr E4BMpjqZqXsjZHvQiO/iq/7sEudkcmLBqaFL2tsdS7WyAEjlPz/Uw9ze+TegewBRRe RhJYceIJMBvayhDJ6sZrJ2AzSrWAH0c5De27h1++JVNt20VygfPsTBEoN6/Uz5WkaD lqBWsvmAuVsKw== From: Andreas Hindborg Date: Wed, 04 Feb 2026 12:56:52 +0100 Subject: [PATCH v14 8/9] rust: implement `ForeignOwnable` for `Owned` MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260204-unique-ref-v14-8-17cb29ebacbb@kernel.org> References: <20260204-unique-ref-v14-0-17cb29ebacbb@kernel.org> In-Reply-To: <20260204-unique-ref-v14-0-17cb29ebacbb@kernel.org> To: Miguel Ojeda , Boqun Feng , Gary Guo , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Alice Ryhl , Trevor Gross , Danilo Krummrich , Greg Kroah-Hartman , Dave Ertman , Ira Weiny , Leon Romanovsky , Paul Moore , Serge Hallyn , "Rafael J. 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Howlett" , Viresh Kumar , Nishanth Menon , Stephen Boyd , Bjorn Helgaas , =?utf-8?q?Krzysztof_Wilczy=C5=84ski?= Cc: linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-block@vger.kernel.org, linux-security-module@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-pm@vger.kernel.org, linux-pci@vger.kernel.org, Andreas Hindborg X-Mailer: b4 0.15-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=2835; i=a.hindborg@kernel.org; h=from:subject:message-id; bh=xYW/EeCkC7WedEcSi5MqPHN0tL67nyGJDfMj502jbkc=; b=owEBbQKS/ZANAwAKAeG4Gj55KGN3AcsmYgBpgzQFB4UxUyi+TEbDKWq5K/ySzEfM5XJVGiPel DNbl61aM+mJAjMEAAEKAB0WIQQSwflHVr98KhXWwBLhuBo+eShjdwUCaYM0BQAKCRDhuBo+eShj d8QnEAC7f+kfpFQ8VLvycQ5Uf37pSzh9CYSYLkEq9ijS1CiF4hKH9X3nU3Jh81xadjC2JLKPzWO XhZrVS7p05z3yuXExsxLGrfdzQMdGZfmg9tz4wSK3Kqp7zkSV842fbhhHF+1Sv282MFdRUkypLM TtXX4NRi3xI334xjlcthZgupM0rUmr16rmKrB9ftOZ8apraAqlOLUTmq80/rC9P2cIYbZufq6Ue WnVWMmbo4mZaPLhlxtSg5zW7+1NveUwbbhfbUt8iWEZN3xH5F+ZAo7xV5LSyw2T2kim3dUDy07I Mdvgncb8HdJ35ird6WIQTOCi0uWHGsB+377g0ILl4Q2Cwd/rg5R3BhB+ssit3WwMN0wAVlqpBs2 pkmVCrdCTGZG66fHJhioyeIl0jWzpBYEmBhwjnDwCjjiJRkqRGCUx/xm61UB/CSRV4Pj1omlZ8d qq4cmZhByK/hOGcEnn9GSxNaNFE4GOIrpueIw/DrBR0i3MEFbhsvzIISSq+IvHqzYgTBHNZx+IV dIyYk9FkYSmd/xopL6yAlO+RCfDEfdd9RIehEPoNy67J+egJGn82xW2nTOba4kLHA4p13PQeiPc hJm/5hN4Jk/emxqkuTYm7z0c3EHsegKGgDQz7+X5xcwk1sHkRLP3YmaH/E/6xsWw/HkG6HVV/M+ eaj7ey+B3OL2jXw== X-Developer-Key: i=a.hindborg@kernel.org; a=openpgp; fpr=3108C10F46872E248D1FB221376EB100563EF7A7 X-Rspamd-Queue-Id: 2605740008 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: bz64yefcckm68wxxruya6szd13mg7g6e X-HE-Tag: 1770206267-72064 X-HE-Meta: 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 R1Q== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Implement `ForeignOwnable` for `Owned`. This allows use of `Owned` in places such as the `XArray`. Note that `T` does not need to implement `ForeignOwnable` for `Owned` to implement `ForeignOwnable`. Signed-off-by: Andreas Hindborg --- rust/kernel/owned.rs | 45 ++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 44 insertions(+), 1 deletion(-) diff --git a/rust/kernel/owned.rs b/rust/kernel/owned.rs index 85251c57f86c6..0b22de4aaf584 100644 --- a/rust/kernel/owned.rs +++ b/rust/kernel/owned.rs @@ -16,7 +16,10 @@ }; use kernel::{ sync::aref::ARef, - types::RefCounted, // + types::{ + ForeignOwnable, // + RefCounted, + }, // }; /// Types that specify their own way of performing allocation and destruction. Typically, this trait @@ -120,6 +123,7 @@ pub unsafe trait Ownable { /// /// - The [`Owned`] has exclusive access to the instance of `T`. /// - The instance of `T` will stay alive at least as long as the [`Owned`] is alive. +#[repr(transparent)] pub struct Owned { ptr: NonNull, } @@ -201,6 +205,45 @@ fn drop(&mut self) { } } +// SAFETY: We derive the pointer to `T` from a valid `T`, so the returned +// pointer satisfy alignment requirements of `T`. +unsafe impl ForeignOwnable for Owned { + const FOREIGN_ALIGN: usize = core::mem::align_of::>(); + + type Borrowed<'a> = &'a T; + type BorrowedMut<'a> = Pin<&'a mut T>; + + fn into_foreign(self) -> *mut kernel::ffi::c_void { + let ptr = self.ptr.as_ptr().cast(); + core::mem::forget(self); + ptr + } + + unsafe fn from_foreign(ptr: *mut kernel::ffi::c_void) -> Self { + Self { + // SAFETY: By function safety contract, `ptr` came from + // `into_foreign` and cannot be null. + ptr: unsafe { NonNull::new_unchecked(ptr.cast()) }, + } + } + + unsafe fn borrow<'a>(ptr: *mut kernel::ffi::c_void) -> Self::Borrowed<'a> { + // SAFETY: By function safety requirements, `ptr` is valid for use as a + // reference for `'a`. + unsafe { &*ptr.cast() } + } + + unsafe fn borrow_mut<'a>(ptr: *mut kernel::ffi::c_void) -> Self::BorrowedMut<'a> { + // SAFETY: By function safety requirements, `ptr` is valid for use as a + // unique reference for `'a`. + let inner = unsafe { &mut *ptr.cast() }; + + // SAFETY: We never move out of inner, and we do not hand out mutable + // references when `T: !Unpin`. + unsafe { Pin::new_unchecked(inner) } + } +} + /// A trait for objects that can be wrapped in either one of the reference types [`Owned`] and /// [`ARef`]. /// -- 2.51.2