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=-5.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,USER_AGENT_SANE_1 autolearn=unavailable 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 DA5DEC33CA9 for ; Tue, 14 Jan 2020 01:30:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ADB112084D for ; Tue, 14 Jan 2020 01:30:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="GKgg2CgD" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729509AbgANBaY (ORCPT ); Mon, 13 Jan 2020 20:30:24 -0500 Received: from aserp2120.oracle.com ([141.146.126.78]:58216 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729436AbgANBaW (ORCPT ); Mon, 13 Jan 2020 20:30:22 -0500 Received: from pps.filterd (aserp2120.oracle.com [127.0.0.1]) by aserp2120.oracle.com (8.16.0.27/8.16.0.27) with SMTP id 00E1TE0t105524; Tue, 14 Jan 2020 01:30:11 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-2019-08-05; bh=A6M6k3ikXF8yBWj9VHiQxI6pJTnSUujmxK2S/8NxTcw=; b=GKgg2CgDiqDxyhrkWOqF5UoV2rsi4K9yH9eAVdbJxkCwdoEtLoEPutV0eO8fXq9FQ4a6 64D23mOZG1H98R4V+rWk5icqO2pxgB5ZEy7If5GR3rlVDKTm44wtUbooYstWE61y6xLY 3jqHo/KXOoArSRRa61aEhf2kSx6MJiyH5TCJTIfzIL/hKG7bndLDlQ5IGAqf9RWA9hn8 f/4mPMz0qC85XqsvtE9d4ye8zPyOCwMCpYQfp58opVNt268rwz3Pk6MKRv3BCfTnsOo5 PGSvO9I4sMNUyPjm+uWgIOcA3XjZWib8IHOcfxro+uwIJRtbvmu/PhZxHqGr76yD9CbZ 7A== Received: from userp3020.oracle.com (userp3020.oracle.com [156.151.31.79]) by aserp2120.oracle.com with ESMTP id 2xf73tjpw8-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 14 Jan 2020 01:30:11 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.27/8.16.0.27) with SMTP id 00E1TDD3176589; Tue, 14 Jan 2020 01:30:10 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by userp3020.oracle.com with ESMTP id 2xfrgjp4mg-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 14 Jan 2020 01:30:10 +0000 Received: from abhmp0014.oracle.com (abhmp0014.oracle.com [141.146.116.20]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 00E1U68n006854; Tue, 14 Jan 2020 01:30:06 GMT Received: from localhost (/67.169.218.210) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 13 Jan 2020 17:30:06 -0800 Date: Mon, 13 Jan 2020 17:30:04 -0800 From: "Darrick J. Wong" To: Ira Weiny Cc: linux-kernel@vger.kernel.org, Alexander Viro , Dan Williams , Dave Chinner , Christoph Hellwig , "Theodore Y. Ts'o" , Jan Kara , linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [RFC PATCH V2 09/12] fs: Prevent mode change if file is mmap'ed Message-ID: <20200114013004.GU8247@magnolia> References: <20200110192942.25021-1-ira.weiny@intel.com> <20200110192942.25021-10-ira.weiny@intel.com> <20200113222212.GO8247@magnolia> <20200114004610.GD29860@iweiny-DESK2.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200114004610.GD29860@iweiny-DESK2.sc.intel.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9499 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-2001140011 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9499 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-2001140011 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 13, 2020 at 04:46:10PM -0800, Ira Weiny wrote: > On Mon, Jan 13, 2020 at 02:22:12PM -0800, Darrick J. Wong wrote: > > On Fri, Jan 10, 2020 at 11:29:39AM -0800, ira.weiny@intel.com wrote: > > > From: Ira Weiny > > > > > [snip] > > > > > > > diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c > > > index bc3654fe3b5d..1ab0906c6c7f 100644 > > > --- a/fs/xfs/xfs_ioctl.c > > > +++ b/fs/xfs/xfs_ioctl.c > > > @@ -1200,6 +1200,14 @@ xfs_ioctl_setattr_dax_invalidate( > > > goto out_unlock; > > > } > > > > > > + /* > > > + * If there is a mapping in place we must remain in our current mode. > > > + */ > > > + if (atomic64_read(&inode->i_mapped)) { > > > > Urk, should we really be messing around with the address space > > internals? > > I contemplated a function call instead of checking i_mapped directly? Is that > what you mean? Yeah. Abstracting the details just enough that filesystems don't have to know that i_mapped is atomic64 etc. > > > > > > + error = -EBUSY; > > > + goto out_unlock; > > > + } > > > + > > > error = filemap_write_and_wait(inode->i_mapping); > > > if (error) > > > goto out_unlock; > > > diff --git a/include/linux/fs.h b/include/linux/fs.h > > > index 631f11d6246e..6e7dc626b657 100644 > > > --- a/include/linux/fs.h > > > +++ b/include/linux/fs.h > > > @@ -740,6 +740,7 @@ struct inode { > > > #endif > > > > > > void *i_private; /* fs or device private pointer */ > > > + atomic64_t i_mapped; > > > > I would have expected to find this in struct address_space since the > > mapping count is a function of the address space, right? > > I suppose but the only external call (above) would be passing an inode. So to > me it seemed better here. But the number of memory mappings reflects the state of the address space, not the inode. Or maybe put another way, if I were an mm developer I would not expect to look in struct inode for mm state. static inline bool inode_has_mappings(struct inode *inode) { return atomic64_read(&inode->i_mapping->mapcount) > 0; } OTOH if there exist other mm developers who /do/ find that storing the mmap count in struct inode is more logical, please let me know. :) --D > Ira > > > > > --D > >