From patchwork Tue Oct 13 23:52:33 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 11836363 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 6AC3B61C for ; Tue, 13 Oct 2020 23:52:37 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 273E222227 for ; Tue, 13 Oct 2020 23:52:37 +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 273E222227 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) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id DCC7D6B00CB; Tue, 13 Oct 2020 19:52:35 -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 CBB956B00CC; Tue, 13 Oct 2020 19:52:35 -0400 (EDT) X-Original-To: linux-mm@kvack.org 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-Spam-Summary: 1,0,0,a5a4dc08460bc2ae,d41d8cd98f00b204,akpm@linux-foundation.org,,RULES_HIT:41:355:379:800:877:960:967:973:988:989:1260:1345:1359:1381:1431:1437:1534:1541:1711:1730:1747:1777:1792:2194:2198:2199:2200:2393:2525:2553:2559:2564:2682:2685:2859:2897:2902:2933:2937:2939:2942:2945:2947:2951:2954:3022:3138:3139:3140:3141:3142:3352:3865:3867:3871:3872:3874:3934:3936:3938:3941:3944:3947:3950:3953:3956:3959:4321:5007:6119:6261:6653:7576:9025:9545:10004:11026:11473:11658:11914:12043:12048:12296:12297:12438:12517:12519:12555:12679:12986:13069:13311:13357:13846:14096:14181:14384:14721:21080:21433:21451:21627:21740:21811:21939:21990:30054:30056:30064:30070:30090,0,RBL:198.145.29.99:@linux-foundation.org:.lbl8.mailshell.net-64.100.201.201 62.2.0.100;04yrikg1mwbshb58drb8ccakmg3pkocwzim3qmrureii5mf4mito3nyb4hygjnx.ra66igsxpmyjwtdq1ukp53fqgsg3edfajxk9teye4t36ma3m4afaij4jik39ryh.6-lbl8.mailshell.net-223.238.255.100,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MS F:not bu 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