From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <rust-for-linux-owner@vger.kernel.org>
X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on
	aws-us-west-2-korg-lkml-1.web.codeaurora.org
Received: from vger.kernel.org (vger.kernel.org [23.128.96.18])
	by smtp.lore.kernel.org (Postfix) with ESMTP id F1404C6FD1D
	for <rust-for-linux@archiver.kernel.org>; Tue, 21 Mar 2023 19:50:09 +0000 (UTC)
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S229513AbjCUTuI (ORCPT
        <rfc822;rust-for-linux@archiver.kernel.org>);
        Tue, 21 Mar 2023 15:50:08 -0400
Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48048 "EHLO
        lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S229610AbjCUTuG (ORCPT
        <rfc822;rust-for-linux@vger.kernel.org>);
        Tue, 21 Mar 2023 15:50:06 -0400
Received: from mail-4322.protonmail.ch (mail-4322.protonmail.ch [185.70.43.22])
        by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5923B9EE1
        for <rust-for-linux@vger.kernel.org>; Tue, 21 Mar 2023 12:50:02 -0700 (PDT)
Date:   Tue, 21 Mar 2023 19:49:55 +0000
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=protonmail.com;
        s=protonmail3; t=1679428200; x=1679687400;
        bh=5wFTfQvkkunlIrsARX4Vq7hYHVmiJWCfu28xcLcdviI=;
        h=Date:To:From:Cc:Subject:Message-ID:In-Reply-To:References:
         Feedback-ID:From:To:Cc:Date:Subject:Reply-To:Feedback-ID:
         Message-ID:BIMI-Selector;
        b=yo3gFfxMfaxuil6kpYNQ51W526MtY1XzriLAqtUMsU0wfTlOKpcjd6bWdEB4zJvCK
         EO9rf+vJFjiQCEsarmSXWn1yMJLfbMI+/d+ufWy9ZgpjQRMnVu0eymjMAT6UJ9kPmF
         LiNAF8i9KPRDecEJlTM5LEaW0nlUmq78H/IFkQXYSRGamiWBT448a9HLgwC2QZZoLu
         sIE/ivUqLaPUY5pKp8CL1RGEPoH72x0VjHLExdvu/7Ga+LX1U8sbDGK5L4MdDzZ2ed
         xZzPxbWPYTiTZP9KSs6dNPwJqlalOo1Zoysefsd0mVxf45dCAA4LI6KH0ahkrPnTJX
         MVu5aeUxjc+aA==
To:     Miguel Ojeda <ojeda@kernel.org>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Wedson Almeida Filho <wedsonaf@gmail.com>,
        Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
        =?utf-8?Q?Bj=C3=B6rn_Roy_Baron?= <bjorn3_gh@protonmail.com>
From:   Benno Lossin <y86-dev@protonmail.com>
Cc:     rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
        patches@lists.linux.dev
Subject: [PATCH v2 2/5] rust: sync: add `assume_init` to `UniqueArc`
Message-ID: <20230321194934.908891-3-y86-dev@protonmail.com>
In-Reply-To: <20230321194934.908891-1-y86-dev@protonmail.com>
References: <20230321194934.908891-1-y86-dev@protonmail.com>
Feedback-ID: 40624463:user:proton
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
Precedence: bulk
List-ID: <rust-for-linux.vger.kernel.org>
X-Mailing-List: rust-for-linux@vger.kernel.org

Adds the `assume_init` function to `UniqueArc<MaybeUninit<T>>` that
unsafely assumes the value to be initialized and yields a value of type
`UniqueArc<T>`. This function is used when manually initializing the
pointee of an `UniqueArc`.

Signed-off-by: Benno Lossin <y86-dev@protonmail.com>
---
 rust/kernel/sync/arc.rs | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
index f2f1c83d72ba..16ec174637b2 100644
--- a/rust/kernel/sync/arc.rs
+++ b/rust/kernel/sync/arc.rs
@@ -489,6 +489,17 @@ impl<T> UniqueArc<MaybeUninit<T>> {
     /// Converts a `UniqueArc<MaybeUninit<T>>` into a `UniqueArc<T>` by wr=
iting a value into it.
     pub fn write(mut self, value: T) -> UniqueArc<T> {
         self.deref_mut().write(value);
+        // SAFETY: We just wrote the value to be initialized.
+        unsafe { self.assume_init() }
+    }
+
+    /// Unsafely assume that `self` is initialized.
+    ///
+    /// # Safety
+    ///
+    /// The caller guarantees that the value behind this pointer has been =
initialized. It is
+    /// *immediate* UB to call this when the value is not initialized.
+    pub unsafe fn assume_init(self) -> UniqueArc<T> {
         let inner =3D ManuallyDrop::new(self).inner.ptr;
         UniqueArc {
             // SAFETY: The new `Arc` is taking over `ptr` from `self.inner=
` (which won't be
--
2.39.2