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 X-Spam-Level: X-Spam-Status: No, score=-13.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1DDBDC433E0 for ; Mon, 10 Aug 2020 23:53:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E70F620731 for ; Mon, 10 Aug 2020 23:53:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727899AbgHJXxV (ORCPT ); Mon, 10 Aug 2020 19:53:21 -0400 Received: from mga11.intel.com ([192.55.52.93]:1236 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726649AbgHJXxV (ORCPT ); Mon, 10 Aug 2020 19:53:21 -0400 IronPort-SDR: WK2668p5xheWOSL8Wytnb4l9f/jU+s3n0jobp7Mfo6BTLeW4DNdb8jxVQGJ9ZV1PUFcZug0WWy 5Dc7NzU59zPQ== X-IronPort-AV: E=McAfee;i="6000,8403,9709"; a="151317486" X-IronPort-AV: E=Sophos;i="5.75,458,1589266800"; d="scan'208";a="151317486" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Aug 2020 16:53:21 -0700 IronPort-SDR: MrAtgg6/Tp9kq/6WFClZ5dVMtaAdGvG6mrQbzRwmTNwY85Vg7FRwZY3+lWkAxSlnrMzpfkmEcG v6oJk6gdbnLQ== X-IronPort-AV: E=Sophos;i="5.75,458,1589266800"; d="scan'208";a="334395937" Received: from iweiny-desk2.sc.intel.com (HELO localhost) ([10.3.52.147]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Aug 2020 16:53:20 -0700 From: ira.weiny@intel.com To: Andrew Morton , Vishal Verma Cc: Ira Weiny , Dan Williams , "Aneesh Kumar K.V" , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH] memremap: Convert devmap static branch to {inc,dec} Date: Mon, 10 Aug 2020 16:53:19 -0700 Message-Id: <20200810235319.2796597-1-ira.weiny@intel.com> X-Mailer: git-send-email 2.28.0.rc0.12.gb6a658bd00c9 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ira Weiny While reviewing Protection Key Supervisor support it was pointed out that using a counter to track static branch enable was an anti-pattern which was better solved using the provided static_branch_{inc,dec} functions.[1] Fix up devmap_managed_key to work the same way. Also this should be safer because there is a very small (very unlikely) race when multiple callers try to enable at the same time. [1] https://lore.kernel.org/lkml/20200714194031.GI5523@worktop.programming.kicks-ass.net/ Cc: Dan Williams Cc: Vishal Verma Signed-off-by: Ira Weiny --- mm/memremap.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/mm/memremap.c b/mm/memremap.c index 03e38b7a38f1..9fb9ad500e78 100644 --- a/mm/memremap.c +++ b/mm/memremap.c @@ -40,12 +40,10 @@ EXPORT_SYMBOL_GPL(memremap_compat_align); #ifdef CONFIG_DEV_PAGEMAP_OPS DEFINE_STATIC_KEY_FALSE(devmap_managed_key); EXPORT_SYMBOL(devmap_managed_key); -static atomic_t devmap_managed_enable; static void devmap_managed_enable_put(void) { - if (atomic_dec_and_test(&devmap_managed_enable)) - static_branch_disable(&devmap_managed_key); + static_branch_dec(&devmap_managed_key); } static int devmap_managed_enable_get(struct dev_pagemap *pgmap) @@ -56,8 +54,7 @@ static int devmap_managed_enable_get(struct dev_pagemap *pgmap) return -EINVAL; } - if (atomic_inc_return(&devmap_managed_enable) == 1) - static_branch_enable(&devmap_managed_key); + static_branch_inc(&devmap_managed_key); return 0; } #else -- 2.28.0.rc0.12.gb6a658bd00c9