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Wed, 14 Aug 2024 13:55:21 +0200 Message-ID: Date: Wed, 14 Aug 2024 13:55:09 +0200 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-Originating-IP: [10.139.217.196] 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; X-Microsoft-Antispam-Message-Info: =?utf-8?B?UWhoeXo5bnN4SXlaZEJLSVIwV1d5SkZjUU90aUpoM1VNQ21rZURhS0xNaWhT?= =?utf-8?B?V1A2Q3B5cGRPYzRxdXk2TmZpQnlIR0k0OGp5dE53WlhWMnBINkg3c2hWdDdK?= =?utf-8?B?QjZjU2dxdlYzaXFZNlJXOHRGWUdOQ0ticmVpZEFwY3htallqcU5Xdm5QZkNR?= =?utf-8?B?V2Z3VUoyVVVEY1c5a3JjeVo5eFRmbWV6VGwzWGhpRG9COWF6cjlPK3ZwK3hT?= =?utf-8?B?eXc1eHByb1IwU0xQdDN5UkFyVHlOM2pRVlBsVGZrK3htbW5FaDN3NTFVQWd3?= =?utf-8?B?a3BXci81cHRjWEg3RXc5L2tEZktDOEdUcDNhUVE5UmdMVDlteGlWZUg4dUZ5?= =?utf-8?B?cloydTJpSlhmZlZCNmh5cGgxV0FSeWZ3QWp3M1RIcDJjcU41ZDBiZjlvS2tJ?= =?utf-8?B?bU9abkdtRWU5NThTcnNNWU9aSHZXZFA1TzdYZnVJL3A2bjZVM3Z6dDc4c2Jj?= =?utf-8?B?dUthbG1QWUdkRUNqdDNsaE5ZTitOV09oQnJuWCtDRUgvOVdORVZEZ0VjdEw0?= =?utf-8?B?R3Q5THdZelpiWWN5eGZsMmExTUhxR3d4YWF6aWJFQVA4VGhIWkZCWWYwTDY0?= =?utf-8?B?b3c0NWZRMlpkSWZSUU1YM05DQi95M0NuK29BNklWWVpoYnI2ZW1kRUthMyt1?= =?utf-8?B?Nm8yOHRZeXhYN284ZExCZ1pXQ25WYUZLNVlzMXc1cmFtQjFFYnJpQ2JucCtz?= =?utf-8?B?VllQRW9rT3dpMjZMd1A3TGdDcTZrM1NsTmRGMDRxUGlHV3owNi90T3lSb2k3?= =?utf-8?B?Wk9NL3M3RUJpWHpIVWlWSE1ZRU9LZXIzSnUzUStYeTZ5M0lEWlp3MzUvTDl3?= =?utf-8?B?VHFoTE1KM1hiNno4bktWVGMwTGJ2MzRrVGRNOStqUGYzV25IT0dremxQNW9G?= =?utf-8?B?S1c5WTdmcTJQd2JKV1pPR3RCV3pKdEU4YW1OVEhkSEp6UnY4SGF1TlZ3UWEz?= =?utf-8?B?M1c4ZjN3MGtibEdFajFMSTU4UnN0MExscUxhVktiNmVtTHdkYVlDUXlwdGJB?= =?utf-8?B?bjczTWFaSTBQUDhIcnlZa2N2d1Jvc1ZwelE5VkNUK2FoWDIwdk1mTHFhSVVV?= =?utf-8?B?N1BiTDNuZ0U0bVM5dmJ5VS9NYWJNQVBXRTl6QnhBWEJPYW5zSkd1NHByMm9w?= =?utf-8?B?d2k4N0IrbTBicVVtZENEelVISjQ0MkhhUUgxMk5mMUZUUUdTTHV6YlcvSUYy?= =?utf-8?B?Q09BUHVmbmw5eGxzeXdtNEdlS2NhcUovaGRzZDZuSGpjQlEvMkRyV1hEcVM5?= =?utf-8?B?VlBUNDRYbFRYL2xpaE5pVWdpMGpObE5BbHJBUEtrUG1BZ0s0YmZNQUJtSy81?= =?utf-8?B?TlBSc3JsUXRSS1BDWVZuZlFWTXI0T1FQTzY0Q09PT0c4ckkrSjVsQUhLcTZt?= =?utf-8?B?UWg0bXMxc3IvYitRaUc4NlBDNCtDR0ZzQ2tXWVRyUHNtVXlyYXkrZ3FrUVNF?= =?utf-8?B?d1gzVENTTzhBblpmVkZFbDJaVlpDekdBbnRYZ1htY0dXMVVZVmdDZXlSdFpU?= =?utf-8?B?WWUvbnk1bmxSZlpURGIrbWNCUCtBdTJzNFNUTncyazZKeVNuR1d4bk12UkYz?= =?utf-8?B?VS9HWURNUXpjUkQrUGYrMlk5aTYyU2NzZWhJSHhSQUY4Y2w1VmdTQnlnR09M?= =?utf-8?B?QTZWVFlUeDlGOXJtS2doRGF0YVFNMFliRW1zYk0zelZyQTBOUCtZSDNPc2pN?= =?utf-8?B?L0pmUEZyT0NneVYvbU82RG9OdlpCdVplVGZaTDFDT1NKTzNKK2hDRjhsUlZm?= =?utf-8?B?N0tQQWhCaE1sWXc1ajBMNUdIdW9UcTdzb0dFbGVsWE0zcHZnZlYzMlFJeDJj?= =?utf-8?B?RFBoa3JLQ0IrVGRYZ3gySE1GUzVlaVFHd3ZVNklzMUJEZW1iT1RzRlIxTE9r?= =?utf-8?B?OFpLOHZhWU9YWEVhVXJ5aWtlSnFOSFdtR0xFckdCaEN3d0E9PQ==?= X-Forefront-Antispam-Report: CIP:139.15.153.206;CTRY:DE;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:eop.bosch-org.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(82310400026)(1800799024)(36860700013)(376014)(7416014)(921020);DIR:OUT;SFP:1101; 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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] --