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=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY 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 38041C433E0 for ; Tue, 5 Jan 2021 01:15:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EB9C122582 for ; Tue, 5 Jan 2021 01:15:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726163AbhAEBPX (ORCPT ); Mon, 4 Jan 2021 20:15:23 -0500 Received: from aserp2120.oracle.com ([141.146.126.78]:58232 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726026AbhAEBPW (ORCPT ); Mon, 4 Jan 2021 20:15:22 -0500 Received: from pps.filterd (aserp2120.oracle.com [127.0.0.1]) by aserp2120.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 10519pvZ050123; Tue, 5 Jan 2021 01:14:38 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-2020-01-29; bh=f8IfE5rAKu34ysqIqeNAPMq783yDDGbSQ/TxvIKPJ8E=; b=U4GMbF0WHdhYdjJ3Lsk2SUWsL4/HPFQM6WEQ4XwMgDmsrry48Ao2wkOlfnnUhJm7z9wg MA4GoysPiXkH4kO9ApCwl65pSFqupmoclphkvQC7I7i+MQmkQB2fGDBNXJTWsqWeQodl fnptaipSOhRb2evYBouZCoyfniIFcT9Odx3VL8Dc4kJj7NGrxnp1nfDME0aiZ6hGhRs8 TIIroUHLFgHbhJGwoxzJjy4AhKUv93J+1hMrMvV/F54/aW9cNNR8CT4TTNrcAu8gnnyO c5b5JsFCQGbNnsghf5PhSs5iCPe2cjfDqHQMreYF2uYFLPG1q9HC/Y/OA17cdVSLzNy5 8g== Received: from userp3020.oracle.com (userp3020.oracle.com [156.151.31.79]) by aserp2120.oracle.com with ESMTP id 35tgskpsx5-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Tue, 05 Jan 2021 01:14:37 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 1051AJjS151340; Tue, 5 Jan 2021 01:14:37 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by userp3020.oracle.com with ESMTP id 35uxnry1dq-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 05 Jan 2021 01:14:37 +0000 Received: from abhmp0012.oracle.com (abhmp0012.oracle.com [141.146.116.18]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 1051EX8M031600; Tue, 5 Jan 2021 01:14:35 GMT Received: from localhost (/67.169.218.210) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 05 Jan 2021 01:14:33 +0000 Date: Mon, 4 Jan 2021 17:14:32 -0800 From: "Darrick J. Wong" To: Brian Foster Cc: wenli xie , xfs , chiluk@ubuntu.com Subject: Re: [PATCH] xfs: fix an ABBA deadlock in xfs_rename Message-ID: <20210105011432.GS6918@magnolia> References: <20210104194437.GJ38809@magnolia> <20210104202714.GE254939@bfoster> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210104202714.GE254939@bfoster> X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9854 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 phishscore=0 spamscore=0 malwarescore=0 mlxscore=0 mlxlogscore=999 suspectscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2101050003 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9854 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxscore=0 spamscore=0 malwarescore=0 phishscore=0 impostorscore=0 bulkscore=0 clxscore=1015 priorityscore=1501 lowpriorityscore=0 adultscore=0 suspectscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2101050003 Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Mon, Jan 04, 2021 at 03:27:14PM -0500, Brian Foster wrote: > On Mon, Jan 04, 2021 at 11:44:37AM -0800, Darrick J. Wong wrote: > > From: Darrick J. Wong > > > > When overlayfs is running on top of xfs and the user unlinks a file in > > the overlay, overlayfs will create a whiteout inode and ask xfs to > > "rename" the whiteout file atop the one being unlinked. If the file > > being unlinked loses its one nlink, we then have to put the inode on the > > unlinked list. > > > > This requires us to grab the AGI buffer of the whiteout inode to take it > > off the unlinked list (which is where whiteouts are created) and to grab > > the AGI buffer of the file being deleted. If the whiteout was created > > in a higher numbered AG than the file being deleted, we'll lock the AGIs > > in the wrong order and deadlock. > > > > Therefore, grab all the AGI locks we think we'll need ahead of time, and > > in the correct order. > > > > Reported-by: wenli xie > > Tested-by: wenli xie > > Fixes: 93597ae8dac0 ("xfs: Fix deadlock between AGI and AGF when target_ip exists in xfs_rename()") > > Signed-off-by: Darrick J. Wong > > --- > > fs/xfs/xfs_inode.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 46 insertions(+) > > > > diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c > > index b7352bc4c815..dd419a1bc6ba 100644 > > --- a/fs/xfs/xfs_inode.c > > +++ b/fs/xfs/xfs_inode.c > > @@ -3000,6 +3000,48 @@ xfs_rename_alloc_whiteout( > > return 0; > > } > > > > +/* > > + * For the general case of renaming files, lock all the AGI buffers we need to > > + * handle bumping the nlink of the whiteout inode off the unlinked list and to > > + * handle dropping the nlink of the target inode. We have to do this in > > + * increasing AG order to avoid deadlocks. > > + */ > > +static int > > +xfs_rename_lock_agis( > > + struct xfs_trans *tp, > > + struct xfs_inode *wip, > > + struct xfs_inode *target_ip) > > +{ > > + struct xfs_mount *mp = tp->t_mountp; > > + struct xfs_buf *bp; > > + xfs_agnumber_t agi_locks[2] = { NULLAGNUMBER, NULLAGNUMBER }; > > + int error; > > + > > + if (wip) > > + agi_locks[0] = XFS_INO_TO_AGNO(mp, wip->i_ino); > > + > > + if (target_ip && VFS_I(target_ip)->i_nlink == 1) > > + agi_locks[1] = XFS_INO_TO_AGNO(mp, target_ip->i_ino); > > + > > + if (agi_locks[0] != NULLAGNUMBER && agi_locks[1] != NULLAGNUMBER && > > + agi_locks[0] > agi_locks[1]) > > + swap(agi_locks[0], agi_locks[1]); > > + > > + if (agi_locks[0] != NULLAGNUMBER) { > > + error = xfs_read_agi(mp, tp, agi_locks[0], &bp); > > + if (error) > > + return error; > > + } > > + > > + if (agi_locks[1] != NULLAGNUMBER) { > > + error = xfs_read_agi(mp, tp, agi_locks[1], &bp); > > + if (error) > > + return error; > > + } > > + > > + return 0; > > +} > > This all looks reasonable to me, but I wonder if we can simplify > a bit by reusing the sorted inodes array we've already created earlier > in xfs_rename(). E.g., something like: > > for (i = 0; i < num_inodes; i++) { > if (inodes[i] != wip && inodes[i] != target_ip) > continue; > error = xfs_read_agi(...); > ... > } > > IOW, similar to how xfs_lock_inodes() and xfs_qm_vop_rename_dqattach() > work. I think it would be difficult to do that because we only need to grab target_ip's AGI if we're going to droplink it, and we haven't yet taken target_ip's ILOCK when we invoke the sorting hat so the link count isn't stable. --D > Brian > > > + > > /* > > * xfs_rename > > */ > > @@ -3130,6 +3172,10 @@ xfs_rename( > > } > > } > > > > + error = xfs_rename_lock_agis(tp, wip, target_ip); > > + if (error) > > + return error; > > + > > /* > > * Directory entry creation below may acquire the AGF. Remove > > * the whiteout from the unlinked list first to preserve correct > > >