From patchwork Tue Feb 11 00:15:27 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Hubbard X-Patchwork-Id: 11374299 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 94DC5109A for ; Tue, 11 Feb 2020 00:16:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 74BB82072C for ; Tue, 11 Feb 2020 00:16:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="E4saXd/r" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727716AbgBKAPm (ORCPT ); Mon, 10 Feb 2020 19:15:42 -0500 Received: from hqnvemgate24.nvidia.com ([216.228.121.143]:4283 "EHLO hqnvemgate24.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727669AbgBKAPm (ORCPT ); Mon, 10 Feb 2020 19:15:42 -0500 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Mon, 10 Feb 2020 16:14:35 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Mon, 10 Feb 2020 16:15:38 -0800 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Mon, 10 Feb 2020 16:15:38 -0800 Received: from HQMAIL111.nvidia.com (172.20.187.18) by HQMAIL101.nvidia.com (172.20.187.10) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Tue, 11 Feb 2020 00:15:38 +0000 Received: from hqnvemgw03.nvidia.com (10.124.88.68) by HQMAIL111.nvidia.com (172.20.187.18) with Microsoft SMTP Server (TLS) id 15.0.1473.3 via Frontend Transport; Tue, 11 Feb 2020 00:15:38 +0000 Received: from blueforge.nvidia.com (Not Verified[10.110.48.28]) by hqnvemgw03.nvidia.com with Trustwave SEG (v7,5,8,10121) id ; Mon, 10 Feb 2020 16:15:37 -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?SsOpcsO0bWUgR2xpc3Nl?= , "Kirill A . Shutemov" , Michal Hocko , Mike Kravetz , Shuah Khan , Vlastimil Babka , Matthew Wilcox , , , , , , LKML , John Hubbard , "Kirill A . Shutemov" Subject: [PATCH v6 03/12] mm: introduce page_ref_sub_return() Date: Mon, 10 Feb 2020 16:15:27 -0800 Message-ID: <20200211001536.1027652-4-jhubbard@nvidia.com> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200211001536.1027652-1-jhubbard@nvidia.com> References: <20200211001536.1027652-1-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=1581380075; bh=Q5fLaghgFbabRh4AhaE8eo4PFQNGOCfHUCuIQWHMtww=; 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=E4saXd/rsLx1Jd/Hqpfy2VR1S/vr6n2rRE1yCnca9yyLBq3F/vV2Uet6L0Qye+uny KskQcpVdF+AdJ+aBTiA76vt9on1GhUmtZ/Yor21Z4R5H4hlfmezMPLqM7E25P+s671 cmmX3OaOw0WDUhKOEo0U0jtUnUlP6JPfrSXPqGjjTwLdNo90pH6CBuxc2qNtKlsM1X 1m5Pu0ViUqfmn/8U6Vqlw/EnO0zebRmhN7fZrn8sfVJXJv08CjeAEu+RFaEPCVYhLQ XF0F2/tQt6EJyet8TXxIxsHCwyYLKXvCCEyG2wV+VjoRJaF5eKMH3ao9VPkV4HBQNS ZxLBFKa29DTig== 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. Reviewed-by: Jan Kara Acked-by: Kirill A. Shutemov Signed-off-by: John Hubbard --- include/linux/page_ref.h | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/include/linux/page_ref.h b/include/linux/page_ref.h index 14d14beb1f7f..d27701199a4d 100644 --- a/include/linux/page_ref.h +++ b/include/linux/page_ref.h @@ -102,6 +102,15 @@ 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_and_return)) + __page_ref_mod_and_return(page, -nr, ret); + return ret; +} + static inline void page_ref_inc(struct page *page) { atomic_inc(&page->_refcount);