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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7CA02C3DA7F for ; Fri, 26 Jul 2024 08:26:55 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 0A42C6B0083; Fri, 26 Jul 2024 04:26:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 054B56B0085; Fri, 26 Jul 2024 04:26:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E84FA6B008A; Fri, 26 Jul 2024 04:26:54 -0400 (EDT) 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 C29746B0083 for ; Fri, 26 Jul 2024 04:26:54 -0400 (EDT) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 3DE1F1A16BF for ; Fri, 26 Jul 2024 08:26:54 +0000 (UTC) X-FDA: 82381223148.23.7D7E278 Received: from mail-40131.protonmail.ch (mail-40131.protonmail.ch [185.70.40.131]) by imf21.hostedemail.com (Postfix) with ESMTP id 542CC1C001A for ; Fri, 26 Jul 2024 08:26:52 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=proton.me header.s=protonmail header.b="dBIKDXc/"; spf=pass (imf21.hostedemail.com: domain of benno.lossin@proton.me designates 185.70.40.131 as permitted sender) smtp.mailfrom=benno.lossin@proton.me; dmarc=pass (policy=quarantine) header.from=proton.me ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1721982362; 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=T76SZ6qLi+QJY5P2rlncRmCRboug4BcadueEcGPkj5g=; b=ExsUoDG+jdixOLufQtI6NelMqdv5DPbuHznjbNiYRaxg6MzGdyK3ymZFvbysXWkFQKtmVT rJ1ZsTO33LuQ1IZWpLkIOKHmpqkmlROxaVW+VsrzZqp9NFvERPwrThHaPCPA6fYXT8jwW2 B3QxG9DexptCqLnqnr1st0KkP4+A3iU= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1721982362; a=rsa-sha256; cv=none; b=SVJ4UiM3kdV/8v0WhSzt3m13JoQGZmhPt/UJaIzA/QLEFYh/ybiPGOhNawTcFow26ShfT0 0il9qSART3vicXxqmWso9VW3PBmg0bcDTDH6KdgZCLZhsF+bk9ZykYW4qOkiNWsqOgFfhP pWMF2hS+VZDN6hwot5vo58m4NinQXVA= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=proton.me header.s=protonmail header.b="dBIKDXc/"; spf=pass (imf21.hostedemail.com: domain of benno.lossin@proton.me designates 185.70.40.131 as permitted sender) smtp.mailfrom=benno.lossin@proton.me; dmarc=pass (policy=quarantine) header.from=proton.me DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=proton.me; s=protonmail; t=1721982410; x=1722241610; bh=T76SZ6qLi+QJY5P2rlncRmCRboug4BcadueEcGPkj5g=; 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=dBIKDXc/MCuJkhRc6r5uTDMvPMi5owDGNkQv/rzWJI0BJ+xtRrz5OOvcgvsWL/r4d ZUWLRlNzYedr9il1gOXChWqXbBC1zn6pSo+pobWX9iw9kfPjSE78uFAOU7CFTWpMtA 8G9XmFOphT3OmcuYnSi8Z5tfHjJ8FhOb0Ff2NV1DCzwSAZQHCtmjkTig1b6hl9BCFV lk5Yy9rdQjJiSgqmH1D4kt/zxgAPPxi937fPFoQBMPflGsqA7ogiLgOwWVme9M9t4m RQ82dGfDyzBzdB5/Opr3z19bqbYRjgXoDq1USlJaaHu3osj0NwMfsj0x8VhMKGT7mQ j74DcSMgy63lA== Date: Fri, 26 Jul 2024 08:26:46 +0000 To: Alice Ryhl From: Benno Lossin Cc: Miguel Ojeda , Andrew Morton , Alex Gaynor , Wedson Almeida Filho , Boqun Feng , Gary Guo , =?utf-8?Q?Bj=C3=B6rn_Roy_Baron?= , Andreas Hindborg , linux-kernel@vger.kernel.org, linux-mm@kvack.org, rust-for-linux@vger.kernel.org Subject: Re: [PATCH] rust: mm: add abstractions for mm_struct and vm_area_struct Message-ID: <324d3628-a537-431f-8dd4-f33184600537@proton.me> In-Reply-To: References: <20240723-vma-v1-1-32ad5a0118ee@google.com> <3bf6bfdc-84af-442a-acec-a58f023d1164@proton.me> Feedback-ID: 71780778:user:proton X-Pm-Message-ID: 15db2875872a64e93eb9af0276362e416da08e74 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Stat-Signature: 4dtyu45xje1upw73nfrwmzdu9y47eg5x X-Rspamd-Queue-Id: 542CC1C001A X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1721982412-200669 X-HE-Meta: U2FsdGVkX18uG9B8f/L0mLEICHEivUV3Sy2wmOansdk3JvZ+53MDv+OULDJMvMyac2k2i2k6hInNlhUzAEulzpuBVV8BWeW+snIY05ZojAaYWfjLSOoXWUeYhNxxrglKVVtu33gCQuc1XxlQxpkjDYZqhuWPsA2EOpQaT6Cz9LSRp59C+Odn68qtGNPaqkPlXiGYXD1z+4SXPOWmkQc/muI2jPhMu/VFbwlNUKXtQAfHBRlVRHF8EbQ1Hs8e/96HADReIQa0aatE+86SbvNtW0dkE9WImtQ38bl88kyKpBx4vgYdCHg1VzAYXGtX6BoHNbiF5oonuGoq6iRpSRRjv4Nm7Qod38MFgWATx8GbJ+7mUaZFq2XbFyJwuFvLOynELrSFd7KnUoCoidTvkVYXvqshZuhc6ATTKrmdc49JVUmNsnTIA9xToX9YQBazL+wo9VDRQr8gKozp5EZuac62zfo4TVmBrIzaXTYfII5JRtxY5sO6Ao+3JiUr1q1HzAAQUS305kl6OwmC1lVT+h7X4ZP2ZEtrDpTp1g0xSOEIC4+QcBOaXXLCVhv5grHQNVFreytNYBXoNiPyetmlqjBFEgcS8t4O8aHUIqw6SDHoz+i4D2NIi9Sf/fVnO/5R30kU2k4RJ1hAiSxC1YYreWRh62AzpAiRPtjQCjLRGFF4QlbRtxmGVJdhXPNnxgb6waKe+pti5N5kjiS4fhERG0JgycmDwdWIffq2ZteumO01QOH66alIAd8H6foDNFo8s/lXmD1jzWqMFsFdjnyuTHyEqwdWB7b+CVsQQ4ekUNYHu7qB+ms5DmacCIdjuwvGfUxqwTzOUsrCAaKnyiDQ9342Uz2jG5ReLnrWClhQZPKuUpHXz9cWOItZyfu+/Le03T2izvMdsy+TOybr0fjnGiqppzAQZHr/DatMMMQIOkhu7l18Z8KX3ne0QlEW5Wzlv84ejQXg29xXSBTqE3fnzOE 8Urovi0y e82iyADMFKzlJLq7ZQx8tMG8Aa19tSbQEdQNyapriXSgieijZeNoy2LpuQkDaueeA8NWl6b7faItzq34LBW8+r5fDJzCu7qswV4mWTK9dC+mSHqaNj7F9msvp5YuZE+89rYdHXemXxbyuRazp2xWxoqCcJFvSSQVLi43c+PoyRt0A3D6ORmYy2t2P+a5QjJlGM2YXBoDPZJ+GMq0+74IIvC8br8Q/i5N2rVLVy1b2zcsPyBEybJOV+Cuss0XH5wUuq0VvRvV3VbNFLvyQLMUjoA8ZOX5xHqT+50R46cj5CWRjAnwkNn4/6JdZdngyISJdbvsP9TCpr1bQYRCAZcTxWWDOMgkG3/1e6ISGypaqY/5tZbqx5yi8p+2eVTfDXWIZArJot86lS7DRI6UFAuoKfbeP6A== 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: On 26.07.24 10:14, Alice Ryhl wrote: > On Fri, Jul 26, 2024 at 10:11=E2=80=AFAM Benno Lossin wrote: >> >> On 23.07.24 16:32, Alice Ryhl wrote: >>> +pub struct MmGet { >>> + mm: NonNull, >>> +} >>> + >>> +impl MmGet { >>> + /// Lock the mmap read lock. >>> + #[inline] >>> + pub fn mmap_write_lock(&self) -> MmapWriteLock<'_> { >>> + // SAFETY: The pointer is valid since we hold a refcount. >>> + unsafe { bindings::mmap_write_lock(self.mm.as_ptr()) }; >>> + >>> + // INVARIANT: We just acquired the write lock, so we can trans= fer to this guard. >>> + // >>> + // The signature of this function ensures that the `MmapWriteL= ock` will not outlive this >>> + // `mmget` refcount. >>> + MmapWriteLock { >>> + mm: self.mm, >>> + _lifetime: PhantomData, >>> + } >>> + } >>> + >>> + /// When dropping this refcount, use `mmput_async` instead of `mmp= ut`. >> >> I don't get this comment. >=20 > The C side provides two ways to decrement the mmget refcount. One is > mmput and the other is mmput_async. The difference is that when the > refcount hits zero, mmput_async cleans up the mm_struct on the > workqueue, whereas mmput cleans it up immediately. This means that > mmput_async is safe in atomic context, but mmput is not. I see, IMO this would be a better comment: /// Converts to this `MmGet` to `MmGetAsync`. /// /// `MmGetAsync` uses `mmput_async` instead of `mmput` for decrementing /// the refcount. Since from a Rust perspective, this is just a conversion function. Maybe the name should also reflect that ie `to_mm_get_async` or similar. --- Cheers, Benno