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=-8.6 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_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED, USER_AGENT_MUTT autolearn=ham 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 A7049C282D9 for ; Thu, 31 Jan 2019 23:28:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 758B12086C for ; Thu, 31 Jan 2019 23:28:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="CX/kAc9d" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726287AbfAaX2Y (ORCPT ); Thu, 31 Jan 2019 18:28:24 -0500 Received: from aserp2130.oracle.com ([141.146.126.79]:53558 "EHLO aserp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725854AbfAaX2Y (ORCPT ); Thu, 31 Jan 2019 18:28:24 -0500 Received: from pps.filterd (aserp2130.oracle.com [127.0.0.1]) by aserp2130.oracle.com (8.16.0.22/8.16.0.22) with SMTP id x0VNOceN035558; Thu, 31 Jan 2019 23:28:18 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to; s=corp-2018-07-02; bh=56jNfu7Y+iQPJPSTc9C+zKrA2uw9SqL30L6DxG1RA3E=; b=CX/kAc9dQcUxMxVuNleBAzXc44tRyo6y974Z/EA1h5pKX1rXRzWHvvHEjYKwPR8Xzofx ylkrh21+WDsN/zGgCHLf8B3DY1jwSU582yIfHEk/IT25p4f6ZmtHJkreCVntGB9Ke+B+ laTId54CQbNJIlh+hmfbD1uQCNX/zBBvbX5dpLyk8kAEaRYGZK3qW7C0U8ACUiplms8S C2DX8d2eWydSGtDHnHw7Ak0vONbea1Q18IsmPuwum3XlgpA01OqSZOryCjFsYSWughp1 dYrI133SUDBWuO0TxSTWm7DI4SZyZEjjJAgwH2ei5F4C8oTFFOyW9104I/BW1lm2wPoN xA== Received: from aserv0021.oracle.com (aserv0021.oracle.com [141.146.126.233]) by aserp2130.oracle.com with ESMTP id 2q8d2ekv3m-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 31 Jan 2019 23:28:18 +0000 Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by aserv0021.oracle.com (8.14.4/8.14.4) with ESMTP id x0VNSHvs025506 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 31 Jan 2019 23:28:18 GMT Received: from abhmp0007.oracle.com (abhmp0007.oracle.com [141.146.116.13]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x0VNSH8R008132; Thu, 31 Jan 2019 23:28:17 GMT Received: from localhost (/67.169.218.210) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 31 Jan 2019 15:28:17 -0800 Date: Thu, 31 Jan 2019 15:28:16 -0800 From: "Darrick J. Wong" To: Christoph Hellwig Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, Piotr Jaroszynski Subject: Re: [PATCH] iomap: get/put the page in iomap_page_create/release() Message-ID: <20190131232816.GF5761@magnolia> References: <20190121151702.28863-1-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190121151702.28863-1-hch@lst.de> User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9153 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1901310168 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Mon, Jan 21, 2019 at 04:17:02PM +0100, Christoph Hellwig wrote: > From: Piotr Jaroszynski > > migrate_page_move_mapping() expects pages with private data set to have > a page_count elevated by 1. This is what used to happen for xfs through > the buffer_heads code before the switch to iomap in commit 82cb14175e7d > ("xfs: add support for sub-pagesize writeback without buffer_heads"). > Not having the count elevated causes move_pages() to fail on memory > mapped files coming from xfs. > > Make iomap compatible with the migrate_page_move_mapping() assumption by > elevating the page count as part of iomap_page_create() and lowering it > in iomap_page_release(). > > It causes the move_pages() syscall to misbehave on memory mapped files > from xfs. It does not not move any pages, which I suppose is "just" a > perf issue, but it also ends up returning a positive number which is out > of spec for the syscall. Talking to Michal Hocko, it sounds like > returning positive numbers might be a necessary update to move_pages() > anyway though. > > Fixes: 82cb14175e7d ("xfs: add support for sub-pagesize writeback without buffer_heads") > Signed-off-by: Piotr Jaroszynski > [hch: actually get/put the page iomap_migrate_page() to make it work > properly] > Signed-off-by: Christoph Hellwig Looks ok (apparently I forgot to ack this explicitly...) Reviewed-by: Darrick J. Wong --D > --- > fs/iomap.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/fs/iomap.c b/fs/iomap.c > index 987fefc054b4..47362397cb82 100644 > --- a/fs/iomap.c > +++ b/fs/iomap.c > @@ -116,6 +116,12 @@ iomap_page_create(struct inode *inode, struct page *page) > atomic_set(&iop->read_count, 0); > atomic_set(&iop->write_count, 0); > bitmap_zero(iop->uptodate, PAGE_SIZE / SECTOR_SIZE); > + > + /* > + * migrate_page_move_mapping() assumes that pages with private data have > + * their count elevated by 1. > + */ > + get_page(page); > set_page_private(page, (unsigned long)iop); > SetPagePrivate(page); > return iop; > @@ -132,6 +138,7 @@ iomap_page_release(struct page *page) > WARN_ON_ONCE(atomic_read(&iop->write_count)); > ClearPagePrivate(page); > set_page_private(page, 0); > + put_page(page); > kfree(iop); > } > > @@ -569,8 +576,10 @@ iomap_migrate_page(struct address_space *mapping, struct page *newpage, > > if (page_has_private(page)) { > ClearPagePrivate(page); > + get_page(newpage); > set_page_private(newpage, page_private(page)); > set_page_private(page, 0); > + put_page(page); > SetPagePrivate(newpage); > } > > -- > 2.20.1 >