From patchwork Mon Aug 10 23:53:19 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ira Weiny X-Patchwork-Id: 11708371 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id E73DA13A4 for ; Mon, 10 Aug 2020 23:53:25 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BE5DB206DC for ; Mon, 10 Aug 2020 23:53:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BE5DB206DC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id C93C36B0003; Mon, 10 Aug 2020 19:53:24 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id C44096B0005; Mon, 10 Aug 2020 19:53:24 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B810A6B0006; Mon, 10 Aug 2020 19:53:24 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0078.hostedemail.com [216.40.44.78]) by kanga.kvack.org (Postfix) with ESMTP id A294D6B0003 for ; Mon, 10 Aug 2020 19:53:24 -0400 (EDT) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 497C4181AEF09 for ; Mon, 10 Aug 2020 23:53:24 +0000 (UTC) X-FDA: 77136313128.15.drink69_480334026fde Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin15.hostedemail.com (Postfix) with ESMTP id 000321814B0C1 for ; Mon, 10 Aug 2020 23:53:23 +0000 (UTC) X-Spam-Summary: 1,0,0,,d41d8cd98f00b204,ira.weiny@intel.com,,RULES_HIT:30054:30056:30064:30070:30090,0,RBL:192.55.52.136:@intel.com:.lbl8.mailshell.net-64.95.201.95 62.18.0.100;04y8rgtfxugc5mxyww45miiqnudtkycwzim3qmrubxx8513imhshtdn7mubmksu.we4x554ugzga599g1dt7q1ckicti1p7rosc9x53hos3yqipbkhsuj19r6jnxrbs.g-lbl8.mailshell.net-223.238.255.100,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:ft,MSBL:0,DNSBL:neutral,Custom_rules:0:0:0,LFtime:23,LUA_SUMMARY:none X-HE-Tag: drink69_480334026fde X-Filterd-Recvd-Size: 3310 Received: from mga12.intel.com (mga12.intel.com [192.55.52.136]) by imf02.hostedemail.com (Postfix) with ESMTP for ; Mon, 10 Aug 2020 23:53:22 +0000 (UTC) IronPort-SDR: amjP4+tU36C6ZUKGk4Wh0yUHzioRDEX4gzu/F3kz3u7fMaMHRRoIjACjXJFJMO7FMfjyZIj6I1 8UeGCHIpQgpQ== X-IronPort-AV: E=McAfee;i="6000,8403,9709"; a="133179868" X-IronPort-AV: E=Sophos;i="5.75,458,1589266800"; d="scan'208";a="133179868" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga106.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 X-Rspamd-Queue-Id: 000321814B0C1 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 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: 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 Reviewed-by: William Kucharski --- 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