From 8ec6dba2581754e375be66f7bedd708d856d8b30 Mon Sep 17 00:00:00 2001 From: Jan Rekorajski Date: Mon, 16 Nov 2009 11:57:02 +0000 Subject: [PATCH 1/2] XFS bug in log recover with quota (bugzilla id 855) Hi, I was hit by a bug in linux 2.6.31 when XFS is not able to recover the log after a crash if fs was mounted with quotas. Gory details in XFS bugzilla: http://oss.sgi.com/bugzilla/show_bug.cgi?id=855. It looks like wrong struct is used in buffer length check, and the following patch should fix the problem. xfs_dqblk_t has a size of 104+32 bytes, while xfs_disk_dquot_t is 104 bytes long, and this is exactly what I see in system logs - "XFS: dquot too small (104) in xlog_recover_do_dquot_trans." Signed-off-by: Jan Rekorajski Reviewed-by: Christoph Hellwig Signed-off-by: Alex Elder --- fs/xfs/xfs_log_recover.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c index 1099395d7d6c..fb17f8226b09 100644 --- a/fs/xfs/xfs_log_recover.c +++ b/fs/xfs/xfs_log_recover.c @@ -1980,7 +1980,7 @@ xlog_recover_do_reg_buffer( "XFS: NULL dquot in %s.", __func__); goto next; } - if (item->ri_buf[i].i_len < sizeof(xfs_dqblk_t)) { + if (item->ri_buf[i].i_len < sizeof(xfs_disk_dquot_t)) { cmn_err(CE_ALERT, "XFS: dquot too small (%d) in %s.", item->ri_buf[i].i_len, __func__); @@ -2635,7 +2635,7 @@ xlog_recover_do_dquot_trans( "XFS: NULL dquot in %s.", __func__); return XFS_ERROR(EIO); } - if (item->ri_buf[1].i_len < sizeof(xfs_dqblk_t)) { + if (item->ri_buf[1].i_len < sizeof(xfs_disk_dquot_t)) { cmn_err(CE_ALERT, "XFS: dquot too small (%d) in %s.", item->ri_buf[1].i_len, __func__); From 6c06f072c2d797ddbb2270363de97c53ebbe0385 Mon Sep 17 00:00:00 2001 From: "Nathaniel W. Turner" Date: Mon, 16 Nov 2009 19:51:48 +0000 Subject: [PATCH 2/2] xfs: copy li_lsn before dropping AIL lock Access to log items on the AIL is generally protected by m_ail_lock; this is particularly needed when we're getting or setting the 64-bit li_lsn on a 32-bit platform. This patch fixes a couple places where we were accessing the log item after dropping the AIL lock on 32-bit machines. This can result in a partially-zeroed log->l_tail_lsn if xfs_trans_ail_delete is racing with xfs_trans_ail_update, and in at least some cases, this can leave the l_tail_lsn with a zero cycle number, which means xlog_space_left will think the log is full (unless CONFIG_XFS_DEBUG is set, in which case we'll trip an ASSERT), leading to processes stuck forever in xlog_grant_log_space. Thanks to Adrian VanderSpek for first spotting the race potential and to Dave Chinner for debug assistance. Signed-off-by: Nathaniel W. Turner Reviewed-by: Christoph Hellwig Signed-off-by: Alex Elder --- fs/xfs/xfs_trans_ail.c | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-) diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c index f31271c30de9..2ffc570679be 100644 --- a/fs/xfs/xfs_trans_ail.c +++ b/fs/xfs/xfs_trans_ail.c @@ -467,6 +467,7 @@ xfs_trans_ail_update( { xfs_log_item_t *dlip = NULL; xfs_log_item_t *mlip; /* ptr to minimum lip */ + xfs_lsn_t tail_lsn; mlip = xfs_ail_min(ailp); @@ -483,8 +484,16 @@ xfs_trans_ail_update( if (mlip == dlip) { mlip = xfs_ail_min(ailp); + /* + * It is not safe to access mlip after the AIL lock is + * dropped, so we must get a copy of li_lsn before we do + * so. This is especially important on 32-bit platforms + * where accessing and updating 64-bit values like li_lsn + * is not atomic. + */ + tail_lsn = mlip->li_lsn; spin_unlock(&ailp->xa_lock); - xfs_log_move_tail(ailp->xa_mount, mlip->li_lsn); + xfs_log_move_tail(ailp->xa_mount, tail_lsn); } else { spin_unlock(&ailp->xa_lock); } @@ -514,6 +523,7 @@ xfs_trans_ail_delete( { xfs_log_item_t *dlip; xfs_log_item_t *mlip; + xfs_lsn_t tail_lsn; if (lip->li_flags & XFS_LI_IN_AIL) { mlip = xfs_ail_min(ailp); @@ -527,9 +537,16 @@ xfs_trans_ail_delete( if (mlip == dlip) { mlip = xfs_ail_min(ailp); + /* + * It is not safe to access mlip after the AIL lock + * is dropped, so we must get a copy of li_lsn + * before we do so. This is especially important + * on 32-bit platforms where accessing and updating + * 64-bit values like li_lsn is not atomic. + */ + tail_lsn = mlip ? mlip->li_lsn : 0; spin_unlock(&ailp->xa_lock); - xfs_log_move_tail(ailp->xa_mount, - (mlip ? mlip->li_lsn : 0)); + xfs_log_move_tail(ailp->xa_mount, tail_lsn); } else { spin_unlock(&ailp->xa_lock); }