From patchwork Tue Feb 4 23:41:09 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Hubbard X-Patchwork-Id: 11365459 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 1205817E0 for ; Tue, 4 Feb 2020 23:42:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E51CD21582 for ; Tue, 4 Feb 2020 23:42:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="m3DL424c" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727926AbgBDXmO (ORCPT ); Tue, 4 Feb 2020 18:42:14 -0500 Received: from hqnvemgate26.nvidia.com ([216.228.121.65]:4040 "EHLO hqnvemgate26.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727664AbgBDXlV (ORCPT ); Tue, 4 Feb 2020 18:41:21 -0500 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate26.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Tue, 04 Feb 2020 15:41:06 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Tue, 04 Feb 2020 15:41:20 -0800 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Tue, 04 Feb 2020 15:41:20 -0800 Received: from HQMAIL107.nvidia.com (172.20.187.13) by HQMAIL111.nvidia.com (172.20.187.18) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Tue, 4 Feb 2020 23:41:20 +0000 Received: from rnnvemgw01.nvidia.com (10.128.109.123) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3 via Frontend Transport; Tue, 4 Feb 2020 23:41:19 +0000 Received: from blueforge.nvidia.com (Not Verified[10.110.48.28]) by rnnvemgw01.nvidia.com with Trustwave SEG (v7,5,8,10121) id ; Tue, 04 Feb 2020 15:41:19 -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 Subject: [PATCH v4 04/12] mm: introduce page_ref_sub_return() Date: Tue, 4 Feb 2020 15:41:09 -0800 Message-ID: <20200204234117.2974687-5-jhubbard@nvidia.com> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200204234117.2974687-1-jhubbard@nvidia.com> References: <20200204234117.2974687-1-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=1580859666; bh=eGaNN16zOGlpqgBYnD+qS5CoX6lMktFz46tjMpWu0K4=; 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=m3DL424ceOUdqPIcEv4fvFteh7CP3YVJXATD1jE4kBe/uqOBlVoeMZJnpG54qLPqi LS4h54t2eUR+P11uvSih3VuwVd8jf/B3Q+TI7dbaEIcsJIx5Kxlxek9hX7M58hkiiw N43uwtFs4tgl/n63rhFntpjRP3ZeMlMhhV67NNMOMpB0SEUf3HKSWTHQWFhdWEXB6+ HQ/jrVmgnB0jGlJ9rU0cDt3U1cux8KoQIFdR0rUDFYkYVppvb1SfSPFVV/eUdzK4TX Zs7wDNjspwR6vj9vWmJaedKN3dBZdkBEI/G/hcY6nprBOuCdgCq7vrZqv1IxOMEb+S mLC9EgDmYvetw== Sender: linux-rdma-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rdma@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 Reviewed-by: Jan Kara --- 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..a0e171265b79 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)) + __page_ref_mod_and_return(page, -nr, ret); + return ret; +} + static inline void page_ref_inc(struct page *page) { atomic_inc(&page->_refcount);