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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3E020C677F1 for ; Thu, 19 Jan 2023 01:19:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230104AbjASBTc (ORCPT ); Wed, 18 Jan 2023 20:19:32 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39272 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230037AbjASBRn (ORCPT ); Wed, 18 Jan 2023 20:17:43 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D343B6C540 for ; Wed, 18 Jan 2023 17:15:37 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 2A731B81FBC for ; Thu, 19 Jan 2023 01:15:37 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C9956C433D2; Thu, 19 Jan 2023 01:15:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1674090935; bh=H75ST6c4bHRwqomZrl9d4nTJ95sa1Wj8V9ffsJhs2f0=; h=Date:To:From:Subject:From; b=qZXrMAROn2KpyQxzbuIE1XcWugMi8m+pl9IMV+gflYxJSTKIUXY22WHd9F8ZYhaHS C91mL4boC+Ua3HIvV5wHKViVFPd1H6xIGKU0rM1RNnOqzvDDa2mdcsuDq8CWIh8kNy ve72+xK1QaTVkoIqOrj5/heTRpQn6w+lJgaj7xoU= Date: Wed, 18 Jan 2023 17:15:35 -0800 To: mm-commits@vger.kernel.org, willy@infradead.org, linmiaohe@huawei.com, alexander.h.duyck@linux.intel.com, sj@kernel.org, akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-stable] mm-page_reporting-replace-rcu_access_pointer-with-rcu_dereference_protected.patch removed from -mm tree Message-Id: <20230119011535.C9956C433D2@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The quilt patch titled Subject: mm/page_reporting: replace rcu_access_pointer() with rcu_dereference_protected() has been removed from the -mm tree. Its filename was mm-page_reporting-replace-rcu_access_pointer-with-rcu_dereference_protected.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: SeongJae Park Subject: mm/page_reporting: replace rcu_access_pointer() with rcu_dereference_protected() Date: Wed, 28 Dec 2022 17:59:42 +0000 Page reporting fetches pr_dev_info using rcu_access_pointer(), which is for safely fetching a pointer that will not be dereferenced but could concurrently updated. The code indeed does not dereference pr_dev_info after fetching it using rcu_access_pointer(), but it fetches the pointer while concurrent updates to the pointer is avoided by holding the update side lock, page_reporting_mutex. In the case, rcu_dereference_protected() should be used instead because it provides better readability and performance on some cases, as rcu_dereference_protected() avoids use of READ_ONCE(). Replace the rcu_access_pointer() calls with rcu_dereference_protected(). Link: https://lkml.kernel.org/r/20221228175942.149491-1-sj@kernel.org Fixes: 36e66c554b5c ("mm: introduce Reported pages") Signed-off-by: SeongJae Park Cc: Alexander Duyck Cc: Matthew Wilcox Cc: Miaohe Lin Signed-off-by: Andrew Morton --- mm/page_reporting.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/mm/page_reporting.c~mm-page_reporting-replace-rcu_access_pointer-with-rcu_dereference_protected +++ a/mm/page_reporting.c @@ -356,7 +356,8 @@ int page_reporting_register(struct page_ mutex_lock(&page_reporting_mutex); /* nothing to do if already in use */ - if (rcu_access_pointer(pr_dev_info)) { + if (rcu_dereference_protected(pr_dev_info, + lockdep_is_held(&page_reporting_mutex))) { err = -EBUSY; goto err_out; } @@ -401,7 +402,8 @@ void page_reporting_unregister(struct pa { mutex_lock(&page_reporting_mutex); - if (rcu_access_pointer(pr_dev_info) == prdev) { + if (prdev == rcu_dereference_protected(pr_dev_info, + lockdep_is_held(&page_reporting_mutex))) { /* Disable page reporting notification */ RCU_INIT_POINTER(pr_dev_info, NULL); synchronize_rcu(); _ Patches currently in -mm which might be from sj@kernel.org are mm-damon-core-update-kernel-doc-comments-for-damos-action-supports-of-each-damon-operations-set.patch mm-damon-core-update-kernel-doc-comments-for-damos-filters-supports-of-each-damon-operations-set.patch docs-mm-damon-index-mention-damos-on-the-intro.patch docs-admin-guide-mm-damon-usage-update-damos-actions-filters-supports-of-each-damon-operations-set.patch docs-mm-damon-add-a-maintainer-profile-for-damon.patch maintainers-damon-link-maintainer-profile-git-trees-and-website.patch selftests-damon-sysfs-hide-expected-write-failures.patch selftests-damon-debugfs_rm_non_contexts-hide-expected-write-error-messages.patch scripts-spelling-add-a-few-more-typos.patch