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 20CBCC33CAF for ; Tue, 14 Jan 2020 01:04:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E9BDE21556 for ; Tue, 14 Jan 2020 01:04:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="q49gJ62u" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729251AbgANBEe (ORCPT ); Mon, 13 Jan 2020 20:04:34 -0500 Received: from aserp2120.oracle.com ([141.146.126.78]:36218 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728896AbgANBEe (ORCPT ); Mon, 13 Jan 2020 20:04:34 -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 00E13GnB085465; Tue, 14 Jan 2020 01:04:25 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=7jBHH4oOQP9IrNSe4g8pOXVxUUR5i6Dekv8HSEosktE=; b=q49gJ62uRjgjD6IaNwvxQbHBzO6WlK2GucQc7AR6OZxlLWMotZvd9XOqZ1vGG69Z4EDX VdqF5U1wK8g7Pr5lFGBTg171P7DQcUiHDEVHRi6/Ram8BKUz2XY7UwMuqehMf9sXUmn3 ukFgJeiSNQmrdmFcMjMf2jXrH8xOtd01f6iVSEUEIGnXpJfbs3N836jRs8Vev2s2F7hK A+LNbxni8wynofU3YSaldKp1HASUi7JevUc3AtTgVnPuhO+ZvD6dXq34cFrboLoze392 KhyyQiB62M/bOTmkmAL4cC8B8G02w1g2miOIee+/7joxjYF4ctqXl/qiE6Dy8gUfWPUF wg== Received: from userp3030.oracle.com (userp3030.oracle.com [156.151.31.80]) by aserp2120.oracle.com with ESMTP id 2xf73tjkcb-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 14 Jan 2020 01:04:24 +0000 Received: from pps.filterd (userp3030.oracle.com [127.0.0.1]) by userp3030.oracle.com (8.16.0.27/8.16.0.27) with SMTP id 00E14FB5170858; Tue, 14 Jan 2020 01:04:23 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userp3030.oracle.com with ESMTP id 2xh2sbjdc2-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 14 Jan 2020 01:04:22 +0000 Received: from abhmp0011.oracle.com (abhmp0011.oracle.com [141.146.116.17]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 00E13OGJ020546; Tue, 14 Jan 2020 01:03:24 GMT Received: from localhost (/67.169.218.210) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 13 Jan 2020 17:03:24 -0800 Date: Mon, 13 Jan 2020 17:03:22 -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 07/12] fs: Add locking for a dynamic inode 'mode' Message-ID: <20200114010322.GS8247@magnolia> References: <20200110192942.25021-1-ira.weiny@intel.com> <20200110192942.25021-8-ira.weiny@intel.com> <20200113221218.GM8247@magnolia> <20200114002005.GA29860@iweiny-DESK2.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200114002005.GA29860@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-2001140007 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-2001140007 Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Mon, Jan 13, 2020 at 04:20:05PM -0800, Ira Weiny wrote: > On Mon, Jan 13, 2020 at 02:12:18PM -0800, Darrick J. Wong wrote: > > On Fri, Jan 10, 2020 at 11:29:37AM -0800, ira.weiny@intel.com wrote: > > > From: Ira Weiny > > [snip] > > > > > > > The File Object > > > --------------- > > > @@ -437,6 +459,8 @@ As of kernel 2.6.22, the following members are defined: > > > int (*atomic_open)(struct inode *, struct dentry *, struct file *, > > > unsigned open_flag, umode_t create_mode); > > > int (*tmpfile) (struct inode *, struct dentry *, umode_t); > > > + void (*lock_mode)(struct inode *); > > > + void (*unlock_mode)(struct inode *); > > > > Yikes. "mode" has a specific meaning for inodes, and this lock isn't > > related to i_mode. This lock protects aops from changing while an > > address space operation is in use. > > Ah... yea ok mode is a bad name. > > > > > > }; > > > > > > Again, all methods are called without any locks being held, unless > > > @@ -584,6 +608,12 @@ otherwise noted. > > > atomically creating, opening and unlinking a file in given > > > directory. > > > > > > +``lock_mode`` > > > + called to prevent operations which depend on the inode's mode from > > > + proceeding should a mode change be in progress > > > > "Inodes can't change mode, because files do not suddenly become > > directories". ;) > > Yea sorry. > > > > > Oh, you meant "lock_XXXX is called to prevent a change in the pagecache > > mode from proceeding while there are address space operations in > > progress". So these are really more aops get and put functions... > > At first I actually did have aops get/put functions but this is really > protecting more than the aops vector because as Christoph said there are file > operations which need to be protected not just address space operations. > > But I agree "mode" is a bad name... Sorry... inode_fops_{get,set}(), then? inode_start_fileop() inode_end_fileop() ? Trying to avoid sounding foppish > > > > > +``unlock_mode`` > > > + called when critical mode dependent operation is complete > > > > > > The Address Space Object > > > ======================== > > > diff --git a/fs/ioctl.c b/fs/ioctl.c > > > index 7c9a5df5a597..ed6ab5303a24 100644 > > > --- a/fs/ioctl.c > > > +++ b/fs/ioctl.c > > > @@ -55,18 +55,29 @@ EXPORT_SYMBOL(vfs_ioctl); > > > static int ioctl_fibmap(struct file *filp, int __user *p) > > > { > > > struct address_space *mapping = filp->f_mapping; > > > + struct inode *inode = filp->f_inode; > > > int res, block; > > > > > > + lock_inode_mode(inode); > > > + > > > /* do we support this mess? */ > > > - if (!mapping->a_ops->bmap) > > > - return -EINVAL; > > > - if (!capable(CAP_SYS_RAWIO)) > > > - return -EPERM; > > > + if (!mapping->a_ops->bmap) { > > > + res = -EINVAL; > > > + goto out; > > > + } > > > + if (!capable(CAP_SYS_RAWIO)) { > > > + res = -EPERM; > > > + goto out; > > > > Why does the order of these checks change here? > > I don't understand? The order does not change we just can't return without > releasing the lock. And to protect against bmap changing the lock needs to be > taken first. Doh. -ENOCOFFEE, I plead. --D > [snip] > > > > > > > +static inline void lock_inode_mode(struct inode *inode) > > > > inode_aops_get()? > > Let me think on this. This is not just getting a reference to the aops vector. > It is more than that... and inode_get is not right either! ;-P > > > > > > +{ > > > + WARN_ON_ONCE(inode->i_op->lock_mode && > > > + !inode->i_op->unlock_mode); > > > + if (inode->i_op->lock_mode) > > > + inode->i_op->lock_mode(inode); > > > +} > > > +static inline void unlock_inode_mode(struct inode *inode) > > > +{ > > > + WARN_ON_ONCE(inode->i_op->unlock_mode && > > > + !inode->i_op->lock_mode); > > > + if (inode->i_op->unlock_mode) > > > + inode->i_op->unlock_mode(inode); > > > +} > > > + > > > static inline ssize_t call_read_iter(struct file *file, struct kiocb *kio, > > > struct iov_iter *iter) > > > > inode_aops_put()? > > ... something like that but not 'aops'... > > Ira > > > > > --D > >