From patchwork Mon Nov 19 10:16:09 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 10688365 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 20EBF13AD for ; Mon, 19 Nov 2018 10:16:42 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 120FC299E2 for ; Mon, 19 Nov 2018 10:16:42 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 0636129C24; Mon, 19 Nov 2018 10:16:42 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_NONE autolearn=unavailable version=3.3.1 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 922A9299E2 for ; Mon, 19 Nov 2018 10:16:41 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6B6B26B1A2B; Mon, 19 Nov 2018 05:16:40 -0500 (EST) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 63F7E6B1A2C; Mon, 19 Nov 2018 05:16:40 -0500 (EST) 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 506076B1A2D; Mon, 19 Nov 2018 05:16:40 -0500 (EST) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from mail-qk1-f198.google.com (mail-qk1-f198.google.com [209.85.222.198]) by kanga.kvack.org (Postfix) with ESMTP id 208556B1A2B for ; Mon, 19 Nov 2018 05:16:40 -0500 (EST) Received: by mail-qk1-f198.google.com with SMTP id d196so68241996qkb.6 for ; Mon, 19 Nov 2018 02:16:40 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-original-authentication-results:x-gm-message-state:from:to:cc :subject:date:message-id:in-reply-to:references; bh=Oq7Mm7RstKCl5jwQdxJ6ybQMpWdJOGauvDFhhJ6+35E=; b=SXSdyVJRTpJaTF14XM8S3MH9g9cUbzNyPgt4vInGiEjMcP/+cXzZyXFJO2nLA+lBAe kwBnU8OJ+3bk+mnGWAuN9EUTDCcjpJGihG1WWRQ5c7+U2/HKj5GInkueciLp527B9LGW Cjmg3+WIbdagSLuOWbzIM8Ex31txdV11OM7GTMHCGi0/Dt9Exh4VUGVkv3xr6UAYJCdt 0nlMzu8xPWNDfsAiA7DYBmjikZn4fMN8enT9zP6+oEM/CADeXZHyP1e6XaSvYASA1reK 0X/Ud92tRS802XtlnIhzgdtSbVfmMBeUZnAbFkE3kpsgsYleqrJclMOe30D6GbX5lX5i WIfg== X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of david@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com X-Gm-Message-State: AGRZ1gL97vwfYGcELVJy6M7+z5g2vA6aEMFwA25AGf8IaeHiVo2etDcY 9N0NknPhI1l0emLJcpEQcQH/Zq/OOIhZHXWBdekUIhbB2882osRqOH8kULpQcP0DDbz1+exQ/Yq lkLmHkJJ9eY1xsLadcWPHDmzZMiARoX2+UyANfppu3sR/zpXnuohIrH94YahqP4Hw1Q== X-Received: by 2002:a37:298f:: with SMTP id p15mr19810863qkp.327.1542622599877; Mon, 19 Nov 2018 02:16:39 -0800 (PST) X-Google-Smtp-Source: AJdET5crH42Eaf7SQImAErlR2w38gaRWZLoeFplwVkH+TfKt7kCbhoLqLuf4Zzy2/iAp5PbpiPMF X-Received: by 2002:a37:298f:: with SMTP id p15mr19810814qkp.327.1542622598665; Mon, 19 Nov 2018 02:16:38 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1542622598; cv=none; d=google.com; s=arc-20160816; b=fDqplYQ2j1aG98uGSPtzICNqDKZcnfU9GKhqzUoXbL+ukUjCP/ccA+ocnHTDunrIaV PizmJOoicDFCM/NXrJ2KYTfSlwSspYt2fg5QiSZhNiBS5rnf0LlSsV9sx5trQRY9qF5b Zb0ES1s2fEgvvwRR9DXh8TwbAiN6sMLtzvwhiSXd9fevoC/IJpFwY2+fI4I2Kibtkxkc 5Bo9c6+hQoUmEZqkvA4J8Lmi7aWJnEdb0aE5sFoquAYSWKznrqeSD/j9arBZ4pHJL6ZP TiFTOQa4QSTusulWVz/cNW/4c5HbtrTPbaK4afXhGOa67pEJPOU7bP/sUdsXeO5eWnB1 GV2w== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=references:in-reply-to:message-id:date:subject:cc:to:from; bh=Oq7Mm7RstKCl5jwQdxJ6ybQMpWdJOGauvDFhhJ6+35E=; b=RqLRawMLUedlfZgf+/9acg2zldY6ipJg+dT1xAAev9qOBX/LVkcYzrQ09Rf1DqAfVp bqWXqc0nAC+g/JnlVQuyCGiVOFl8BzUYCsNM+FoMOjce+bmEXHGG5aBxXl5ilX7qjNsz w+5jdG7QuCYrKF5y2PT7po+3GUfd8NpQxitYRTn4Ecxgqn+JShdPm3UnbCf5WR/vQa97 qm2SpL6ZRdHxoSbDmPwUARC8XqC+FNAina3AkdYfItn67ATBtmiI9qTragcWjPyyFMlS sYM/hvARmNpV5Cu5I8aBlPTZy4wvixxHscBz4qRhCfgPTwqJft5ZTbgwl5zvKqIRupH5 QmUw== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of david@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id f3si11264836qkf.49.2018.11.19.02.16.38 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 19 Nov 2018 02:16:38 -0800 (PST) Received-SPF: pass (google.com: domain of david@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of david@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 9EB02308FC5B; Mon, 19 Nov 2018 10:16:37 +0000 (UTC) Received: from t460s.redhat.com (ovpn-117-77.ams2.redhat.com [10.36.117.77]) by smtp.corp.redhat.com (Postfix) with ESMTP id F3674105706D; Mon, 19 Nov 2018 10:16:34 +0000 (UTC) From: David Hildenbrand To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, devel@linuxdriverproject.org, linux-fsdevel@vger.kernel.org, linux-pm@vger.kernel.org, xen-devel@lists.xenproject.org, kexec-ml , pv-drivers@vmware.com, David Hildenbrand , Andrew Morton , Matthew Wilcox , Michal Hocko , "Michael S. Tsirkin" Subject: [PATCH v1 1/8] mm: balloon: update comment about isolation/migration/compaction Date: Mon, 19 Nov 2018 11:16:09 +0100 Message-Id: <20181119101616.8901-2-david@redhat.com> In-Reply-To: <20181119101616.8901-1-david@redhat.com> References: <20181119101616.8901-1-david@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Mon, 19 Nov 2018 10:16:37 +0000 (UTC) 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: X-Virus-Scanned: ClamAV using ClamSMTP Commit b1123ea6d3b3 ("mm: balloon: use general non-lru movable page feature") reworked balloon handling to make use of the general non-lru movable page feature. The big comment block in balloon_compaction.h contains quite some outdated information. Let's fix this. Cc: Andrew Morton Cc: Matthew Wilcox Cc: Michal Hocko Cc: "Michael S. Tsirkin" Signed-off-by: David Hildenbrand Acked-by: Michael S. Tsirkin --- include/linux/balloon_compaction.h | 26 +++++++++----------------- 1 file changed, 9 insertions(+), 17 deletions(-) diff --git a/include/linux/balloon_compaction.h b/include/linux/balloon_compaction.h index 53051f3d8f25..cbe50da5a59d 100644 --- a/include/linux/balloon_compaction.h +++ b/include/linux/balloon_compaction.h @@ -4,15 +4,18 @@ * * Common interface definitions for making balloon pages movable by compaction. * - * Despite being perfectly possible to perform ballooned pages migration, they - * make a special corner case to compaction scans because balloon pages are not - * enlisted at any LRU list like the other pages we do compact / migrate. + * Balloon page migration makes use of the general non-lru movable page + * feature. + * + * page->private is used to reference the responsible balloon device. + * page->mapping is used in context of non-lru page migration to reference + * the address space operations for page isolation/migration/compaction. * * As the page isolation scanning step a compaction thread does is a lockless * procedure (from a page standpoint), it might bring some racy situations while * performing balloon page compaction. In order to sort out these racy scenarios * and safely perform balloon's page compaction and migration we must, always, - * ensure following these three simple rules: + * ensure following these simple rules: * * i. when updating a balloon's page ->mapping element, strictly do it under * the following lock order, independently of the far superior @@ -21,19 +24,8 @@ * +--spin_lock_irq(&b_dev_info->pages_lock); * ... page->mapping updates here ... * - * ii. before isolating or dequeueing a balloon page from the balloon device - * pages list, the page reference counter must be raised by one and the - * extra refcount must be dropped when the page is enqueued back into - * the balloon device page list, thus a balloon page keeps its reference - * counter raised only while it is under our special handling; - * - * iii. after the lockless scan step have selected a potential balloon page for - * isolation, re-test the PageBalloon mark and the PagePrivate flag - * under the proper page lock, to ensure isolating a valid balloon page - * (not yet isolated, nor under release procedure) - * - * iv. isolation or dequeueing procedure must clear PagePrivate flag under - * page lock together with removing page from balloon device page list. + * ii. isolation or dequeueing procedure must remove the page from balloon + * device page list under b_dev_info->pages_lock. * * The functions provided by this interface are placed to help on coping with * the aforementioned balloon page corner case, as well as to ensure the simple