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 03D5CC4451C for ; Sat, 18 Jul 2026 05:33:09 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3A0626B0141; Sat, 18 Jul 2026 01:33:06 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3034B6B0143; Sat, 18 Jul 2026 01:33:06 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1A3FE6B0144; Sat, 18 Jul 2026 01:33:06 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id C2FC86B0141 for ; Sat, 18 Jul 2026 01:33:05 -0400 (EDT) Received: from smtpin09.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 2591D120160 for ; Sat, 18 Jul 2026 05:33:05 +0000 (UTC) X-FDA: 85000778730.09.B60409A Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf15.hostedemail.com (Postfix) with ESMTP id 2E365A0005 for ; Sat, 18 Jul 2026 05:33:03 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=S74oZ+Kf; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf15.hostedemail.com: domain of boqun@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=boqun@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1784352783; 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-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=ANkivdWz9zJi28Ji5ZKsqedVfMZZkLTBuL3A5HXMgG4=; b=zD99imtk1MYtjM1RzYBknA2M01+WbEFy1/qDqMwAEYqrP+C7XX7mWZGstGmeEC/2lO1Dce +mHOG5M6SZIyoeK7V0iIjb5MXofubUq0kYOHva9r/AhwS9Mifjq/ZrAvHGAZcNLU4OLbP6 jyKr4jt2v1EoS6f15IkrwtRW0UFLITs= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=S74oZ+Kf; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf15.hostedemail.com: domain of boqun@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=boqun@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1784352783; b=YUVCuc6bvSLzjpZLFdeLMoFAWUECA2TnQE1flTlB8yuTr4jtK769F92IhvtUBTSaJOjNG8 4Tui281sLEBeU1B/2XzdIYFyoeKqUuV3mK6kfEhV/DTy2PL4BEaw0A9iE5yUOlC8NL4uJm t7t/KQ2hp7zJHjvpDQwcCBpbPkhZNUg= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 6B8674518E; Sat, 18 Jul 2026 05:33:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 525541F00A3D; Sat, 18 Jul 2026 05:33:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784352782; bh=ANkivdWz9zJi28Ji5ZKsqedVfMZZkLTBuL3A5HXMgG4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=S74oZ+Kf+W9DaTE/adZxHs/zT3jTY86uvo9csra4zk1fxvcoz87SLmi1zDEP3fW6b Rw/M7sccrpOA8NtpIc08mzE2JKpo/HJ4QhVOGiKUiqL7rZMilH6rjPXcZK2h72INHZ eaByKrAaXmSI0JgJqSEX9epJnXZTLTMWo3l3sXweHIaVeqBOpc4mFqgP8nefQV9KgW KQUhG8FlOnBNUuY9F94SLEDqTQEb6EfXuXpW0KDIhyvDL9fTwbeUKIMsoNCIcfo+rf ZxjDumuq+1trxbnnafqMpPzyLbP7QQQGWmyQrw6BKmcrSta+myUC9UXGq18JeLPJD8 03/0Bnn2jrosg== Received: from phl-compute-01.internal (phl-compute-01.internal [10.202.2.41]) by mailfauth.phl.internal (Postfix) with ESMTP id 82E0EF40067; Sat, 18 Jul 2026 01:33:00 -0400 (EDT) Received: from phl-frontend-03 ([10.202.2.162]) by phl-compute-01.internal (MEProxy); Sat, 18 Jul 2026 01:33:00 -0400 X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: dmFkZTEgEAJxx43zj+N2HexbcXxXpr8iZewHIC+wBoUe/3kHvIsxmf0uovnwyzmQf22fh5 PbBpjLE4M1x+gkTl4x5OuQgzkddFgVOLc7SPm8OVC3wj6PmDWqpG/wyzm0HbMF//9RDtvM cqERhXH8fRAethPTEdiPCDM2biIjvo2duSrcDNiRwIZ4PJTMN9f05eRQvmRRsxcI1+ZGXR GIOp0pU8kR4mYsSetTdmMF1Q09Qod6lgNc4Vx07svlwAfyl7KUdd5xFGJoXDRG1kaoRL4T /VNW+87mn/mN1dMvhE363j1dLxUYIFMMuhRaBTcK4fjHHNruAjFs082R/vn5pb6pwik6pX 3SHkN1ACEiezX0mrwyw4KfdbjmcRDjPvFlZoRAWQNQEQ3EJoP/wDviNR1nZpBknlDVOTAm 5dYtVMhKPL3ejT4Z+9iLU6DN6wRmWI4z6RdrjcnbevPeUXCNjW/MmqIagNfqcNHcvysGxf F03b3aVMnfh3U5HgzIMSYBanXCwMagUxvz5GKBlhVYIyKFcLfT6NwEhyGaJIOzCGE3faVH ZMdtpcaeMbwqM2mvR0yLwIk6IcpchHNeCuWKsiYXXPQcx8PqDKoFg2G0cPq0x543bCm8PT Sy+F7A9BzGFg985bJyfOkZcS3quFI+ZuDrrtYiKBfrcVpYvLCLmguRzokYZg X-ME-Proxy: Feedback-ID: i8dbe485b:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Sat, 18 Jul 2026 01:32:59 -0400 (EDT) From: Boqun Feng To: rust-for-linux@vger.kernel.org, rcu@vger.kernel.org Cc: Miguel Ojeda , Boqun Feng , Gary Guo , =?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Daniel Almeida , Tamir Duberstein , Alexandre Courbot , =?UTF-8?q?Onur=20=C3=96zkan?= , "Liam R. Howlett" , Andrew Ballance , Alexander Viro , Christian Brauner , Jan Kara , Lyude Paul , "Paul E. McKenney" , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Uladzislau Rezki , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Sumit Semwal , =?UTF-8?q?Christian=20K=C3=B6nig?= , Greg Kroah-Hartman , "Yury Norov (NVIDIA)" , Asahi Lina , Matthew Maurer , Lorenzo Stoakes , linux-kernel@vger.kernel.org, maple-tree@lists.infradead.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org Subject: [RFC PATCH v2 2/4] rust: maple_tree: Add load_rcu() Date: Fri, 17 Jul 2026 22:32:45 -0700 Message-ID: <20260718053247.25154-3-boqun@kernel.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260718053247.25154-1-boqun@kernel.org> References: <20260718053247.25154-1-boqun@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 2E365A0005 X-Stat-Signature: mqzcdajwraw1wgks5fieurn6zhzihb1t X-HE-Tag: 1784352783-517066 X-HE-Meta: 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 Hfp0QEuU 2X69O8u/qrCt5hECh7SFvecyFWO+zE1gJWI7gcX7t17xFdZdwoVVDDtTiCmAgB+LtLLvjKXj1FTriiS+u5zOuGsTMJ/7lg/l+JK3fwozW6M6D7qF1fvCBkctDnc8uPhOB7kNqCNlRt/zUwGKbx6QBpZykh9PsVAP1bM0ahEGWxRuCpL/IwtbXYDwP/kRT8xaTTqD+HvDNE5GSjQzmWf+gv/MOTWAYk+F7Tb+wEb5Poe/tTfS6qz5nn2HwGy2eaCE1nghMyqVeRSEWtvZQJ2ZgMgXu3jR0+gXUd8jUZ+803S8qQ4HV4E3mmNrkNbg5s3P4mu+1BjirVvbuO56n4RHwJ+b9vfxAkp0sIu7HHuw80QIjqwvf/YT2qAY7Swzui/zKfVndCwoPCBbJC13bOJhmPKDOZrGhFmevfaIt6cKURvdwi+o= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Alice Ryhl Now that we have a concept of rcu-safe containers, we may add a load_rcu() method to MapleTree that does not take the spinlock. Signed-off-by: Alice Ryhl --- rust/kernel/maple_tree.rs | 52 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 52 insertions(+) diff --git a/rust/kernel/maple_tree.rs b/rust/kernel/maple_tree.rs index 265d6396a78a..1499191b8935 100644 --- a/rust/kernel/maple_tree.rs +++ b/rust/kernel/maple_tree.rs @@ -16,6 +16,10 @@ alloc::Flags, error::to_result, prelude::*, + sync::rcu::{ + self, + ForeignOwnableRcu, // + }, types::{ForeignOwnable, Opaque}, }; @@ -233,6 +237,54 @@ pub fn erase(&self, index: usize) -> Option { unsafe { T::try_from_foreign(ret) } } + /// Load the value at the given index with rcu. + /// + /// # Examples + /// + /// Read the value under an rcu read lock. Even if the value is removed, it remains accessible + /// for one rcu grace period. + /// + /// ```ignore + /// use kernel::{ + /// maple_tree::MapleTree, + /// sync::rcu::{self, RcuBox}, + /// }; + /// + /// let tree = KBox::pin_init(MapleTree::>::new(), GFP_KERNEL)?; + /// + /// let ten = RcuBox::new(10, GFP_KERNEL)?; + /// tree.insert(100, ten, GFP_KERNEL)?; + /// + /// let rcu_read_lock = rcu::Guard::new(); + /// let ten = tree.load_rcu(100, &rcu_read_lock); + /// assert_eq!(ten, Some(&10)); + /// + /// // Even if the value gets removed, we may continue to access it for one rcu grace period. + /// tree.erase(100); + /// assert_eq!(ten, Some(&10)); + /// # Ok::<_, Error>(()) + /// ``` + #[inline] + pub fn load_rcu<'rcu>( + &self, + index: usize, + _rcu: &'rcu rcu::Guard, + ) -> Option> + where + T: ForeignOwnableRcu, + { + // SAFETY: `self.tree` contains a valid maple tree. + let ret = unsafe { bindings::mtree_load(self.tree.get(), index) }; + if ret.is_null() { + return None; + } + + // SAFETY: If the pointer is not null, then it references a valid instance of `T`. It is + // safe to borrow the instance for 'rcu because the signature of this function enforces that + // the borrow does not outlive an rcu grace period. + Some(unsafe { T::rcu_borrow(ret) }) + } + /// Lock the internal spinlock. #[inline] pub fn lock(&self) -> MapleGuard<'_, T> { -- 2.50.1 (Apple Git-155)