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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F0FC7C433F5 for ; Wed, 9 Mar 2022 21:48:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231774AbiCIVtY (ORCPT ); Wed, 9 Mar 2022 16:49:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37268 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231300AbiCIVtY (ORCPT ); Wed, 9 Mar 2022 16:49:24 -0500 Received: from mail104.syd.optusnet.com.au (mail104.syd.optusnet.com.au [211.29.132.246]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 858BC48E4D for ; Wed, 9 Mar 2022 13:48:23 -0800 (PST) Received: from dread.disaster.area (pa49-186-150-27.pa.vic.optusnet.com.au [49.186.150.27]) by mail104.syd.optusnet.com.au (Postfix) with ESMTPS id 6505753168E; Thu, 10 Mar 2022 08:48:22 +1100 (AEDT) Received: from dave by dread.disaster.area with local (Exim 4.92.3) (envelope-from ) id 1nS4AP-003Xfr-RU; Thu, 10 Mar 2022 08:48:21 +1100 Date: Thu, 10 Mar 2022 08:48:21 +1100 From: Dave Chinner To: "Darrick J. Wong" Cc: linux-xfs@vger.kernel.org Subject: Re: [PATCH 1/2] xfs: reserve quota for dir expansion when linking/unlinking files Message-ID: <20220309214821.GH661808@dread.disaster.area> References: <164685374120.495923.2523387358442198692.stgit@magnolia> <164685374682.495923.2923492909223420951.stgit@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <164685374682.495923.2923492909223420951.stgit@magnolia> X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.4 cv=VuxAv86n c=1 sm=1 tr=0 ts=622920a6 a=sPqof0Mm7fxWrhYUF33ZaQ==:117 a=sPqof0Mm7fxWrhYUF33ZaQ==:17 a=kj9zAlcOel0A:10 a=o8Y5sQTvuykA:10 a=VwQbUJbxAAAA:8 a=7-415B0cAAAA:8 a=VRkXK53dqWtryug5LAwA:9 a=CjuIK1q_8ugA:10 a=AjGcO6oz07-iQ99wixmX:22 a=biEYGPWJfzWAr4FL6Ov7:22 Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Wed, Mar 09, 2022 at 11:22:26AM -0800, Darrick J. Wong wrote: > From: Darrick J. Wong > > XFS does not reserve quota for directory expansion when linking or > unlinking children from a directory. This means that we don't reject > the expansion with EDQUOT when we're at or near a hard limit, which > means that unprivileged userspace can use link()/unlink() to exceed > quota. > > The fix for this is nuanced -- link operations don't always expand the > directory, and we allow a link to proceed with no space reservation if > we don't need to add a block to the directory to handle the addition. > Unlink operations generally do not expand the directory (you'd have to > free a block and then cause a btree split) and we can defer the > directory block freeing if there is no space reservation. > > Moreover, there is a further bug in that we do not trigger the blockgc > workers to try to clear space when we're out of quota. > > To fix both cases, create a new xfs_trans_alloc_dir function that > allocates the transaction, locks and joins the inodes, and reserves > quota for the directory. If there isn't sufficient space or quota, > we'll switch the caller to reservationless mode. This should prevent > quota usage overruns with the least restriction in functionality. > > Signed-off-by: Darrick J. Wong > --- > fs/xfs/xfs_inode.c | 30 +++++------------- > fs/xfs/xfs_trans.c | 86 ++++++++++++++++++++++++++++++++++++++++++++++++++++ > fs/xfs/xfs_trans.h | 3 ++ > 3 files changed, 97 insertions(+), 22 deletions(-) Overall looks good, minor nits below: > > > diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c > index 04bf467b1090..a131bbfe74e4 100644 > --- a/fs/xfs/xfs_inode.c > +++ b/fs/xfs/xfs_inode.c > @@ -1217,7 +1217,7 @@ xfs_link( > { > xfs_mount_t *mp = tdp->i_mount; > xfs_trans_t *tp; > - int error; > + int error, space_error; > int resblks; > > trace_xfs_link(tdp, target_name); > @@ -1236,19 +1236,11 @@ xfs_link( > goto std_return; > > resblks = XFS_LINK_SPACE_RES(mp, target_name->len); > - error = xfs_trans_alloc(mp, &M_RES(mp)->tr_link, resblks, 0, 0, &tp); > - if (error == -ENOSPC) { > - resblks = 0; > - error = xfs_trans_alloc(mp, &M_RES(mp)->tr_link, 0, 0, 0, &tp); > - } > + error = xfs_trans_alloc_dir(tdp, &M_RES(mp)->tr_link, sip, &resblks, > + &tp, &space_error); It's the nospace_error, isn't it? The code reads a lot better when it's called that, too. > if (error) > goto std_return; > > - xfs_lock_two_inodes(sip, XFS_ILOCK_EXCL, tdp, XFS_ILOCK_EXCL); > - > - xfs_trans_ijoin(tp, sip, XFS_ILOCK_EXCL); > - xfs_trans_ijoin(tp, tdp, XFS_ILOCK_EXCL); > - > error = xfs_iext_count_may_overflow(tdp, XFS_DATA_FORK, > XFS_IEXT_DIR_MANIP_CNT(mp)); > if (error) > @@ -1267,6 +1259,8 @@ xfs_link( > > if (!resblks) { > error = xfs_dir_canenter(tp, tdp, target_name); > + if (error == -ENOSPC && space_error) > + error = space_error; This would be better in the error_return stack, I think. That way the transformation only has to be done once, and it will be done for all functions that can potentially return ENOSPC. > if (error) > goto error_return; > } > @@ -2755,6 +2749,7 @@ xfs_remove( > xfs_mount_t *mp = dp->i_mount; > xfs_trans_t *tp = NULL; > int is_dir = S_ISDIR(VFS_I(ip)->i_mode); > + int dontcare; > int error = 0; > uint resblks; > > @@ -2781,22 +2776,13 @@ xfs_remove( > * block from the directory. > */ > resblks = XFS_REMOVE_SPACE_RES(mp); > - error = xfs_trans_alloc(mp, &M_RES(mp)->tr_remove, resblks, 0, 0, &tp); > - if (error == -ENOSPC) { > - resblks = 0; > - error = xfs_trans_alloc(mp, &M_RES(mp)->tr_remove, 0, 0, 0, > - &tp); > - } > + error = xfs_trans_alloc_dir(dp, &M_RES(mp)->tr_remove, ip, &resblks, > + &tp, &dontcare); > if (error) { > ASSERT(error != -ENOSPC); > goto std_return; > } So we just ignore -EDQUOT when it is returned in @dontcare? I'd like a comment to explain why we don't care about EDQUOT here, because the next time I look at this I will have forgotten all about this... Cheers, Dave. -- Dave Chinner david@fromorbit.com