From patchwork Sat Feb 1 03:40:21 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Hubbard X-Patchwork-Id: 208837 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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 F0A6BC35250 for ; Sat, 1 Feb 2020 03:41:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C87F7207FD for ; Sat, 1 Feb 2020 03:41:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="iDX4gxpQ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726698AbgBADlP (ORCPT ); Fri, 31 Jan 2020 22:41:15 -0500 Received: from hqnvemgate24.nvidia.com ([216.228.121.143]:4473 "EHLO hqnvemgate24.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727164AbgBADkj (ORCPT ); Fri, 31 Jan 2020 22:40:39 -0500 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Fri, 31 Jan 2020 19:39:42 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Fri, 31 Jan 2020 19:40:35 -0800 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Fri, 31 Jan 2020 19:40:35 -0800 Received: from HQMAIL105.nvidia.com (172.20.187.12) by HQMAIL109.nvidia.com (172.20.187.15) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Sat, 1 Feb 2020 03:40:35 +0000 Received: from rnnvemgw01.nvidia.com (10.128.109.123) by HQMAIL105.nvidia.com (172.20.187.12) with Microsoft SMTP Server (TLS) id 15.0.1473.3 via Frontend Transport; Sat, 1 Feb 2020 03:40:35 +0000 Received: from blueforge.nvidia.com (Not Verified[10.110.48.28]) by rnnvemgw01.nvidia.com with Trustwave SEG (v7, 5, 8, 10121) id ; Fri, 31 Jan 2020 19:40:34 -0800 From: John Hubbard To: Andrew Morton CC: Al Viro , Christoph Hellwig , Dan Williams , Dave Chinner , Ira Weiny , Jan Kara , Jason Gunthorpe , Jonathan Corbet , =?utf-8?b?SsOpcsO0bWUgR2xp?= =?utf-8?q?sse?= , "Kirill A . Shutemov" , Michal Hocko , Mike Kravetz , Shuah Khan , Vlastimil Babka , Matthew Wilcox , , , , , , LKML , John Hubbard Subject: [PATCH v3 04/12] mm: introduce page_ref_sub_return() Date: Fri, 31 Jan 2020 19:40:21 -0800 Message-ID: <20200201034029.4063170-5-jhubbard@nvidia.com> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200201034029.4063170-1-jhubbard@nvidia.com> References: <20200201034029.4063170-1-jhubbard@nvidia.com> MIME-Version: 1.0 X-NVConfidentiality: public DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1580528382; bh=VhVwoCFqTx48m7C67hmpKfI2lp8OYGAP7BWu53hCs80=; h=X-PGP-Universal:From:To:CC:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:X-NVConfidentiality: Content-Transfer-Encoding:Content-Type; b=iDX4gxpQL2C0C9cMl4/0o9eEAC7Hffol4qeTM8bdozImGlWGXqrTALpzFzNxnt84/ RP6GdlgNzoWj4sRyEUs8oyVGWXe+luTZElPfdyPd6vZfePeURd2Ux1fkG4/x2z70pn XJ2izDvgoWSUjZFwNRu1IjGXJZ+3MnE5RojJLRoNlgb+5a8aplp4kvEs3lPpb1Tg+0 EHKeLOExY9j98deZAlBlmkzFh1D2x7PgVif+1weB34UZlIrezOItQEENKUD7tLo9Jt 6TLR7YuU1IULbseyKPQlc2LYomTvJPzqML/kdsxGpziYRoKXXdjiZffwif2bKYuB8k lyJ7bq5UVNBsA== Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org An upcoming patch requires subtracting a large chunk of refcounts from a page, and checking what the resulting refcount is. This is a little different than the usual "check for zero refcount" that many of the page ref functions already do. However, it is similar to a few other routines that (like this one) are generally useful for things such as 1-based refcounting. Add page_ref_sub_return(), that subtracts a chunk of refcounts atomically, and returns an atomic snapshot of the result. Signed-off-by: John Hubbard --- include/linux/page_ref.h | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/include/linux/page_ref.h b/include/linux/page_ref.h index 14d14beb1f7f..b9cbe553d1e7 100644 --- a/include/linux/page_ref.h +++ b/include/linux/page_ref.h @@ -102,6 +102,16 @@ static inline void page_ref_sub(struct page *page, int nr) __page_ref_mod(page, -nr); } +static inline int page_ref_sub_return(struct page *page, int nr) +{ + int ret = atomic_sub_return(nr, &page->_refcount); + + if (page_ref_tracepoint_active(__tracepoint_page_ref_mod)) + __page_ref_mod(page, -nr); + + return ret; +} + static inline void page_ref_inc(struct page *page) { atomic_inc(&page->_refcount);