path: root/fs/xfs/xfs_fsops.c
diff options
authorDave Chinner <dchinner@redhat.com>2010-08-24 11:46:31 +1000
committerDave Chinner <david@fromorbit.com>2010-08-24 11:46:31 +1000
commit1a387d3be2b30c90f20d49a3497a8fc0693a9d18 (patch)
tree4c8081f6620976dbfc3ecee0e26296c0890bceba /fs/xfs/xfs_fsops.c
parent2fe33661fcd79d4c53022509f7223d526b5fa233 (diff)
xfs: dummy transactions should not dirty VFS state
When we need to cover the log, we issue dummy transactions to ensure the current log tail is on disk. Unfortunately we currently use the root inode in the dummy transaction, and the act of committing the transaction dirties the inode at the VFS level. As a result, the VFS writeback of the dirty inode will prevent the filesystem from idling long enough for the log covering state machine to complete. The state machine gets stuck in a loop issuing new dummy transactions to cover the log and never makes progress. To avoid this problem, the dummy transactions should not cause externally visible state changes. To ensure this occurs, make sure that dummy transactions log an unchanging field in the superblock as it's state is never propagated outside the filesystem. This allows the log covering state machine to complete successfully and the filesystem now correctly enters a fully idle state about 90s after the last modification was made. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de>
Diffstat (limited to 'fs/xfs/xfs_fsops.c')
1 files changed, 18 insertions, 13 deletions
diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
index dbca5f5c37b..43b1d569933 100644
--- a/fs/xfs/xfs_fsops.c
+++ b/fs/xfs/xfs_fsops.c
@@ -604,31 +604,36 @@ out:
return 0;
+ * Dump a transaction into the log that contains no real change. This is needed
+ * to be able to make the log dirty or stamp the current tail LSN into the log
+ * during the covering operation.
+ *
+ * We cannot use an inode here for this - that will push dirty state back up
+ * into the VFS and then periodic inode flushing will prevent log covering from
+ * making progress. Hence we log a field in the superblock instead.
+ */
- xfs_mount_t *mp)
+ xfs_mount_t *mp,
+ int flags)
xfs_trans_t *tp;
- xfs_inode_t *ip;
int error;
tp = _xfs_trans_alloc(mp, XFS_TRANS_DUMMY1, KM_SLEEP);
- error = xfs_trans_reserve(tp, 0, XFS_ICHANGE_LOG_RES(mp), 0, 0, 0);
+ error = xfs_trans_reserve(tp, 0, mp->m_sb.sb_sectsize + 128, 0, 0,
if (error) {
xfs_trans_cancel(tp, 0);
return error;
- ip = mp->m_rootip;
- xfs_ilock(ip, XFS_ILOCK_EXCL);
- xfs_trans_ijoin(tp, ip);
- xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
- xfs_trans_set_sync(tp);
- error = xfs_trans_commit(tp, 0);
- xfs_iunlock(ip, XFS_ILOCK_EXCL);
- return error;
+ /* log the UUID because it is an unchanging field */
+ xfs_mod_sb(tp, XFS_SB_UUID);
+ if (flags & SYNC_WAIT)
+ xfs_trans_set_sync(tp);
+ return xfs_trans_commit(tp, 0);