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Wed, 14 Aug 2024 13:55:21 +0200 Message-ID: Date: Wed, 14 Aug 2024 13:55:09 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 11/26] rust: alloc: remove `BoxExt` extension To: Danilo Krummrich , , , , , , , , , , CC: , , , , , , , , , , , , , References: <20240812182355.11641-1-dakr@kernel.org> <20240812182355.11641-12-dakr@kernel.org> Content-Language: en-US From: Dirk Behme In-Reply-To: <20240812182355.11641-12-dakr@kernel.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: AMS1EPF00000041:EE_|DB9PR10MB8141:EE_ X-MS-Office365-Filtering-Correlation-Id: 70dffa1b-464d-4526-3f80-08dcbc57fa26 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|1800799024|36860700013|376014|7416014|921020; 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X-OriginatorOrg: de.bosch.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Aug 2024 11:55:22.3973 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 70dffa1b-464d-4526-3f80-08dcbc57fa26 X-MS-Exchange-CrossTenant-Id: 0ae51e19-07c8-4e4b-bb6d-648ee58410f4 X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=0ae51e19-07c8-4e4b-bb6d-648ee58410f4;Ip=[139.15.153.206];Helo=[eop.bosch-org.com] X-MS-Exchange-CrossTenant-AuthSource: AMS1EPF00000041.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DB9PR10MB8141 On 12.08.2024 20:22, Danilo Krummrich wrote: > Now that all existing `Box` users were moved to the kernel `Box` type, > remove the `BoxExt` extension and all other related extensions. I just noticed that in the recent 'rust-dev' branch we have a change which *adds* something to BoxExt: rust: kernel: add drop_contents to BoxExt https://github.com/Rust-for-Linux/linux/commit/62c34da1da6c01a635ea2308cb42996d0571059e I'm unclear how relevant that is. Just want to mention this in case it would make sense to include that directly in this patch series to avoid a future add-on patch ;) Thanks, Dirk P.S.: It looks like anything like this at least makes the compiler happy: diff --git a/rust/kernel/alloc/kbox.rs b/rust/kernel/alloc/kbox.rs index d67f975502246..e91d441835d54 100644 --- a/rust/kernel/alloc/kbox.rs +++ b/rust/kernel/alloc/kbox.rs @@ -9,6 +9,7 @@ use core::mem::MaybeUninit; use core::ops::{Deref, DerefMut}; use core::pin::Pin; +use core::ptr; use core::ptr::NonNull; use core::result::Result; @@ -270,6 +271,28 @@ pub fn new_uninit(flags: Flags) -> Result, A>, AllocError> { Ok(Box(ptr, PhantomData::)) } + /// Drops the contents, but keeps the allocation. + /// + /// # Examples + /// + /// ``` + /// use kernel::alloc::{Flags, KBox}; + /// let value = KBox::new([0; 32], GFP_KERNEL)?; + /// assert_eq!(*value, [0; 32]); + /// let value = KBox::drop_contents(value); + /// // Now we can re-use `value`: + /// let value = KBox::write(value, [1; 32]); + /// assert_eq!(*value, [1; 32]); + /// # Ok::<(), Error>(()) + /// ``` + pub fn drop_contents(this: Self) -> Box, A> { + let ptr = Box::into_raw(this); + // SAFETY: `ptr` is valid, because it came from `Box::into_raw`. + unsafe { ptr::drop_in_place(ptr) }; + // SAFETY: `ptr` is valid, because it came from `Box::into_raw`. + unsafe { Box::from_raw(ptr.cast()) } + } + /// Constructs a new `Pin>`. If `T` does not implement [`Unpin`], then `x` will be /// pinned in memory and can't be moved. #[inline] --