From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:36992 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751782AbdGEQQ3 (ORCPT ); Wed, 5 Jul 2017 12:16:29 -0400 From: Brian Foster Subject: [PATCH] xfs: fix contiguous dquot chunk iteration livelock Date: Wed, 5 Jul 2017 12:16:27 -0400 Message-Id: <20170705161627.52734-1-bfoster@redhat.com> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: linux-xfs@vger.kernel.org Cc: Christoph Hellwig The patch below updated xfs_dq_get_next_id() to use the XFS iext lookup helpers to locate the next quota id rather than to seek for data in the quota file. The updated code fails to correctly handle the case where the quota inode might have contiguous chunks part of the same extent. In this case, the start block offset is calculated based on the next expected id but the extent lookup returns the same start offset as for the previous chunk. This causes the returned id to go backwards and livelocks the quota iteration. This problem is reproduced intermittently by generic/232. To handle this case, check whether the startoff from the extent lookup is behind the startoff calculated from the next quota id. If so, bump up got.br_startoff to the specific file offset that is expected to hold the next dquot chunk. Fixes: bda250dbaf39 ("xfs: rewrite xfs_dq_get_next_id using xfs_iext_lookup_extent") Signed-off-by: Brian Foster --- This is still undergoing testing, but otherwise fixes the problem I've observed with generic/232. Brian fs/xfs/xfs_dquot.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/fs/xfs/xfs_dquot.c b/fs/xfs/xfs_dquot.c index 8848b39..f89f7b52 100644 --- a/fs/xfs/xfs_dquot.c +++ b/fs/xfs/xfs_dquot.c @@ -733,10 +733,15 @@ xfs_dq_get_next_id( return error; } - if (xfs_iext_lookup_extent(quotip, "ip->i_df, start, &idx, &got)) + if (xfs_iext_lookup_extent(quotip, "ip->i_df, start, &idx, &got)) { + /* contiguous chunk, bump startoff for the id calculation */ + if (got.br_startoff < start) + got.br_startoff = start; *id = got.br_startoff * mp->m_quotainfo->qi_dqperchunk; - else + } else { error = -ENOENT; + } + xfs_iunlock(quotip, lock_flags); return error; -- 2.9.4