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 E8373E9B251 for ; Tue, 24 Feb 2026 11:19:53 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 527EF6B0088; Tue, 24 Feb 2026 06:19:53 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 4BBD96B008A; Tue, 24 Feb 2026 06:19:53 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3C22B6B0095; Tue, 24 Feb 2026 06:19:53 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 26F4E6B0088 for ; Tue, 24 Feb 2026 06:19:53 -0500 (EST) Received: from smtpin22.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id A229B14055E for ; Tue, 24 Feb 2026 11:19:52 +0000 (UTC) X-FDA: 84479105424.22.F118F4B Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf24.hostedemail.com (Postfix) with ESMTP id A881518000C for ; Tue, 24 Feb 2026 11:19:50 +0000 (UTC) Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=dDpqaaZj; spf=pass (imf24.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=1771931990; 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=fH3R2cmeEIB2gPAkQWfs9E/OqttY1p4wDSkyU9WCeP8=; b=vVJs4HOnt26MtzT1ipG0fKTxdqored5EV4IKVUabjv3E2Wqb+nY73zGUN3MRSaB4HGXZ1T WrlSmCh4PrFK6dFq5HD2LI/bQhOBWA1MrlTINc61bV2xAlrh0YLiIlPNKVfvrn6SUxDawW 9Pefvmzw9lu34LED1bjh1fZnKPLoeC0= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1771931990; a=rsa-sha256; cv=none; b=jXn2gI0GZlduUMOS5wUFf2zDiv7k0JL4WC+c0kYr4qlMQG+HJZmX1jZVNLG3LzckBTpqfV GK0oaZsLquBaxsb4777NpDhGm/MEjBs55thkXgdferc0DApx8hPrs247t7lLhQ1Rf1ThCh tx+DREVmuoiT2Cy42+vFkF7Va47f1F4= ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=dDpqaaZj; spf=pass (imf24.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 CCE6940ADE; Tue, 24 Feb 2026 11:19:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 71FE0C116D0; Tue, 24 Feb 2026 11:19:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1771931989; bh=ZXVxYHlu0zHczyQ9RV4gzKJTzAnDzspoUnWv3esNFwE=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=dDpqaaZjsrKAAuBigQMTjSHyxPwyewaJ+Kh431pzCvN3W/5M0RWV/9LsDjrc8NJAn ji8U2nnjIczOlsmv9Cc8A8/xV2GqUP5ESuXy4HSP6AgQdIH6Q8oYe45W47lN8bPXWy dYy9O/c+OBIQAmB31y7RS0nduullT7ZOft6gWwXrfyBcNTM1LXOndDBQcMGZdltFCt kblbrFJuhKDqAQxsaH0YxOn7BGEr/kRvVDvQlDVo5VToqaNaIw5A9B4B2yN5sWcz62 jzbZSa9w5/3bCsNch90KohlPX2hcU2oWOPDfWIc7OQeB8SrVG8zCEdClApUuvgU7+4 MhoQkxKQ68UDg== From: Andreas Hindborg Date: Tue, 24 Feb 2026 12:18:04 +0100 Subject: [PATCH v16 09/10] rust: implement `ForeignOwnable` for `Owned` MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260224-unique-ref-v16-9-c21afcb118d3@kernel.org> References: <20260224-unique-ref-v16-0-c21afcb118d3@kernel.org> In-Reply-To: <20260224-unique-ref-v16-0-c21afcb118d3@kernel.org> To: Miguel Ojeda , 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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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 c81c2ea88124b..505ac2200d2d6 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 @@ -114,6 +117,7 @@ pub trait Ownable { /// /// - Until `T::release` is called, this `Owned` exclusively owns the underlying `T`. /// - The `T` value is pinned. +#[repr(transparent)] pub struct Owned { ptr: NonNull, } @@ -186,6 +190,45 @@ 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