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=-6.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 AA72CC433E7 for ; Tue, 13 Oct 2020 23:52:36 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4941621D7B for ; Tue, 13 Oct 2020 23:52:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="F20R9S98" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4941621D7B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E43816B00CA; Tue, 13 Oct 2020 19:52:35 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DCC7D6B00CB; Tue, 13 Oct 2020 19:52:35 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CBB956B00CC; Tue, 13 Oct 2020 19:52:35 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0217.hostedemail.com [216.40.44.217]) by kanga.kvack.org (Postfix) with ESMTP id 9B2F96B00CA for ; Tue, 13 Oct 2020 19:52:35 -0400 (EDT) Received: from smtpin18.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 39E8E1EE6 for ; Tue, 13 Oct 2020 23:52:35 +0000 (UTC) X-FDA: 77368554270.18.boat57_4802dbf27207 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin18.hostedemail.com (Postfix) with ESMTP id 175A81015E996 for ; Tue, 13 Oct 2020 23:52:35 +0000 (UTC) X-HE-Tag: boat57_4802dbf27207 X-Filterd-Recvd-Size: 3299 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf35.hostedemail.com (Postfix) with ESMTP for ; Tue, 13 Oct 2020 23:52:34 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 7E04921D7B; Tue, 13 Oct 2020 23:52:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602633153; bh=pQ/fx9SwOVZ3UpfdSvTg6Va21OAz6g0thpuxuObBGaA=; h=Date:From:To:Subject:In-Reply-To:From; b=F20R9S98eoCZIJq01/qtdYC94j6y4NEchGEgljbFmjlhyAaS/L+N8bmmCR5ceo+TD /SBb0fJyH/i8IXGP6DeeRJ41VwynfS0ZApIaPWY34pwJk9ILNZeZYJNw2RQiXhjxuP YOuw+1i3wJ8HYGk9AF3BBtVTtFZSNvMoq0z0O79I= Date: Tue, 13 Oct 2020 16:52:33 -0700 From: Andrew Morton To: akpm@linux-foundation.org, dan.j.williams@intel.com, ira.weiny@intel.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org, vishal.l.verma@intel.com, william.kucharski@oracle.com Subject: [patch 077/181] mm/memremap.c: convert devmap static branch to {inc,dec} Message-ID: <20201013235233.t-QL6UOhs%akpm@linux-foundation.org> In-Reply-To: <20201013164658.3bfd96cc224d8923e66a9f4e@linux-foundation.org> User-Agent: s-nail v14.8.16 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 Subject: mm/memremap.c: convert devmap static branch to {inc,dec} 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/ Link: https://lkml.kernel.org/r/20200810235319.2796597-1-ira.weiny@intel.com Signed-off-by: Ira Weiny Reviewed-by: William Kucharski Cc: Dan Williams Cc: Vishal Verma Signed-off-by: Andrew Morton --- mm/memremap.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) --- a/mm/memremap.c~memremap-convert-devmap-static-branch-to-incdec +++ a/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(str 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 _