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=-2.2 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 EB5A9C2D0CD for ; Wed, 18 Dec 2019 15:52:15 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 8A4962465E for ; Wed, 18 Dec 2019 15:52:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=shutemov-name.20150623.gappssmtp.com header.i=@shutemov-name.20150623.gappssmtp.com header.b="KDdHHJJR" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8A4962465E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=shutemov.name Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id DBA7C8E0119; Wed, 18 Dec 2019 10:52:14 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id D6A7D8E00F5; Wed, 18 Dec 2019 10:52:14 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C59658E0119; Wed, 18 Dec 2019 10:52:14 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0211.hostedemail.com [216.40.44.211]) by kanga.kvack.org (Postfix) with ESMTP id B0B768E00F5 for ; Wed, 18 Dec 2019 10:52:14 -0500 (EST) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with SMTP id 51C9840DD for ; Wed, 18 Dec 2019 15:52:14 +0000 (UTC) X-FDA: 76278703788.15.knife57_3091110015653 X-HE-Tag: knife57_3091110015653 X-Filterd-Recvd-Size: 5019 Received: from mail-lj1-f196.google.com (mail-lj1-f196.google.com [209.85.208.196]) by imf23.hostedemail.com (Postfix) with ESMTP for ; Wed, 18 Dec 2019 15:52:13 +0000 (UTC) Received: by mail-lj1-f196.google.com with SMTP id h23so2679017ljc.8 for ; Wed, 18 Dec 2019 07:52:13 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shutemov-name.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=9SaCbmKz1ngtAKjewhoah2l6ODU7+VciCnZ7nlhe26A=; b=KDdHHJJR0qVpHZqAH81m6HqiNucHS6+DyOVljs3zJhGM2FtVdbdAm0v2Xxx2kkMzcc COndoaW+YFAjiesHFNY+QGvBhkVduyh7QLCQeLwcNzFcgoRSyGgSLcKxln6/f1EUD6yP 0y/6+ZumAIbzC9iZaVPFSydS1BkjYoeUFSafS/fB2OWFlpyQaG5ZPEXYvAMbIqCKuFSL vWtk3rEHKc5uyahuOPC2nUQfw14PqKcbFsQXhuikgf46s/H3eDyiCMpavZwnwbAsy3mj YXZ/SZZpNe1V4549MQIslp0gnIgv8CLO8jjGejFKXWpzPMIfXWxDiYo5N9hhWPoVV8yK Z+eQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=9SaCbmKz1ngtAKjewhoah2l6ODU7+VciCnZ7nlhe26A=; b=b5BqrNVB7QNRy0YD5du6AqZn3jd/wUZzZAo+MCdEfUwWdglYmKDfq2XRv/hgF1vH3B C4BMYqf/ipxvGNt77X5tNV41aI4dKVhq9X/xLN7bwL0PhHEgylPxupmQIZh1bDrIzTYr ogjziF0yCw1lyr1iEnYB7Y0XNiLNhfECVI+0+iJiZsrVeNB5E5qPZFKzh77xk+Btfd4m li9awvzszUjZ6ibyj4MtdYWU7BgpDPQnZE2i6N4L6sV2aFgj03Eg2H1k/byXz8J80Kue P8fBDcMv5f+4n4OpKRSivPMLqAikgIsHiV+andL9BLEEM90qr8g+vSOYu5Tk/Eb2VluT 182w== X-Gm-Message-State: APjAAAVbvbgIp0X6ehMy4+T8KcCAS+HRCj6Vb147hhJhYc2MRP9o2OMZ DEyRLmoU6dK5pAUrYgp+mXbLgQ== X-Google-Smtp-Source: APXvYqwSmzkDxFfUqfRx+ol+ctreHSER3AZEkxHGbqQ5sNtLr5I/0+mwtD90Owb4uveY0c44Ujy5Kw== X-Received: by 2002:a2e:3312:: with SMTP id d18mr2333248ljc.222.1576684332255; Wed, 18 Dec 2019 07:52:12 -0800 (PST) Received: from box.localdomain ([86.57.175.117]) by smtp.gmail.com with ESMTPSA id s16sm1351312lfc.35.2019.12.18.07.52.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Dec 2019 07:52:11 -0800 (PST) Received: by box.localdomain (Postfix, from userid 1000) id 66C2E1012CF; Wed, 18 Dec 2019 18:52:11 +0300 (+03) Date: Wed, 18 Dec 2019 18:52:11 +0300 From: "Kirill A. Shutemov" To: John Hubbard Cc: Andrew Morton , Al Viro , Alex Williamson , Benjamin Herrenschmidt , =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= , Christoph Hellwig , Dan Williams , Daniel Vetter , Dave Chinner , David Airlie , "David S . Miller" , Ira Weiny , Jan Kara , Jason Gunthorpe , Jens Axboe , Jonathan Corbet , =?utf-8?B?SsOpcsO0bWU=?= Glisse , Magnus Karlsson , Mauro Carvalho Chehab , Michael Ellerman , Michal Hocko , Mike Kravetz , Paul Mackerras , Shuah Khan , Vlastimil Babka , bpf@vger.kernel.org, dri-devel@lists.freedesktop.org, kvm@vger.kernel.org, linux-block@vger.kernel.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-media@vger.kernel.org, linux-rdma@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, netdev@vger.kernel.org, linux-mm@kvack.org, LKML , Christoph Hellwig , "Aneesh Kumar K . V" Subject: Re: [PATCH v11 01/25] mm/gup: factor out duplicate code from four routines Message-ID: <20191218155211.emcegdp5uqgorfwe@box> References: <20191216222537.491123-1-jhubbard@nvidia.com> <20191216222537.491123-2-jhubbard@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191216222537.491123-2-jhubbard@nvidia.com> User-Agent: NeoMutt/20180716 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: On Mon, Dec 16, 2019 at 02:25:13PM -0800, John Hubbard wrote: > +static void put_compound_head(struct page *page, int refs) > +{ > + /* Do a get_page() first, in case refs == page->_refcount */ > + get_page(page); > + page_ref_sub(page, refs); > + put_page(page); > +} It's not terribly efficient. Maybe something like: VM_BUG_ON_PAGE(page_ref_count(page) < ref, page); if (refs > 2) page_ref_sub(page, refs - 1); put_page(page); ? -- Kirill A. Shutemov