From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp1040.oracle.com ([156.151.31.81]:26696 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751379AbdGRSPm (ORCPT ); Tue, 18 Jul 2017 14:15:42 -0400 Date: Tue, 18 Jul 2017 11:15:35 -0700 From: "Darrick J. Wong" Subject: Re: [PATCH, RFC] xfs: fix multi-AG deadlock in xfs_bunmapi Message-ID: <20170718181535.GJ4224@magnolia> References: <20170718172545.18065-1-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170718172545.18065-1-hch@lst.de> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Christoph Hellwig Cc: n.borisov.lkml@gmail.com, linux-xfs@vger.kernel.org On Tue, Jul 18, 2017 at 07:25:45PM +0200, Christoph Hellwig wrote: > Just like in the allocator we must avoid touching multiple AGs out of > order when freeing blocks, as freeing still locks the AGF and can cause > the same AB-BA deadlocks as in the allocation path. > > Signed-off-by: Christoph Hellwig > Reported-by: Nikolay Borisov Looks ok, though I wonder what the bug report looked like. :) Reviewed-by: Darrick J. Wong > --- > fs/xfs/libxfs/xfs_bmap.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c > index 0a9880777c9c..935adde72a8b 100644 > --- a/fs/xfs/libxfs/xfs_bmap.c > +++ b/fs/xfs/libxfs/xfs_bmap.c > @@ -5435,6 +5435,7 @@ __xfs_bunmapi( > xfs_fsblock_t sum; > xfs_filblks_t len = *rlen; /* length to unmap in file */ > xfs_fileoff_t max_len; > + xfs_agnumber_t prev_agno = NULLAGNUMBER, agno; > > trace_xfs_bunmap(ip, bno, len, flags, _RET_IP_); > > @@ -5534,6 +5535,17 @@ __xfs_bunmapi( > */ > del = got; > wasdel = isnullstartblock(del.br_startblock); > + > + /* > + * Make sure we don't touch multiple AGF headers out of order > + * in a single transaction, as that could cause AB-BA deadlocks. > + */ > + if (!wasdel) { > + agno = XFS_FSB_TO_AGNO(mp, del.br_startblock); > + if (prev_agno != NULLAGNUMBER && prev_agno > agno) > + break; > + prev_agno = agno; > + } > if (got.br_startoff < start) { > del.br_startoff = start; > del.br_blockcount -= start - got.br_startoff; > -- > 2.11.0 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html