[PATCH 098/102] xfs: shutdown xfs_sync_worker before the log

Dave Chinner
2012-08-23T05:05:15Z

From: Ben Myers <bpm@sgi.com>

Upstream commit: 8866fc6fa55e31b2bce931b7963ff16641b39dc7

Revert commit 1307bbd, which uses the s_umount semaphore to provide
exclusion between xfs_sync_worker and unmount, in favor of shutting down
the sync worker before freeing the log in xfs_log_unmount. This is a
cleaner way of resolving the race between xfs_sync_worker and unmount
than using s_umount.

Signed-off-by: Ben Myers <bpm@sgi.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
---
fs/xfs/linux-2.6/xfs_sync.c | 33 ++++++++++++++++-----------------
fs/xfs/xfs_log.c | 1 +
2 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/fs/xfs/linux-2.6/xfs_sync.c b/fs/xfs/linux-2.6/xfs_sync.c
index 74ea9b1..5b6f46b 100644
--- a/fs/xfs/linux-2.6/xfs_sync.c
+++ b/fs/xfs/linux-2.6/xfs_sync.c
@@ -470,24 +470,23 @@ xfs_sync_worker(
* We shouldn't write/force the log if we are in the mount/unmount
* process or on a read only filesystem. The workqueue still needs to be
* active in both cases, however, because it is used for inode reclaim
- * during these times. Use the s_umount semaphore to provide exclusion
- * with unmount.
+ * during these times. Use the MS_ACTIVE flag to avoid doing anything
+ * during mount. Doing work during unmount is avoided by calling
+ * cancel_delayed_work_sync on this work queue before tearing down
+ * the ail and the log in xfs_log_unmount.
*/
- if (down_read_trylock(&mp->m_super->s_umount)) {
- if (!(mp->m_super->s_flags & MS_ACTIVE) &&
- !(mp->m_flags & XFS_MOUNT_RDONLY)) {
- /* dgc: errors ignored here */
- if (mp->m_super->s_frozen == SB_UNFROZEN &&
- xfs_log_need_covered(mp))
- error = xfs_fs_log_dummy(mp);
- else
- xfs_log_force(mp, 0);
- error = xfs_qm_sync(mp, SYNC_TRYLOCK);
-
- /* start pushing all the metadata that is currently dirty */
- xfs_ail_push_all(mp->m_ail);
- }
- up_read(&mp->m_super->s_umount);
+ if (!(mp->m_super->s_flags & MS_ACTIVE) &&
+ !(mp->m_flags & XFS_MOUNT_RDONLY)) {
+ /* dgc: errors ignored here */
+ if (mp->m_super->s_frozen == SB_UNFROZEN &&
+ xfs_log_need_covered(mp))
+ error = xfs_fs_log_dummy(mp);
+ else
+ xfs_log_force(mp, 0);
+ error = xfs_qm_sync(mp, SYNC_TRYLOCK);
+
+ /* start pushing all the metadata that is currently dirty */
+ xfs_ail_push_all(mp->m_ail);
}

/* queue us up again */
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index dc37cdb..3030618 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -813,6 +813,7 @@ xfs_log_unmount_write(xfs_mount_t *mp)
void
xfs_log_unmount(xfs_mount_t *mp)
{
+ cancel_delayed_work_sync(&mp->m_sync_work);
xfs_trans_ail_destroy(mp);
xlog_dealloc_log(mp->m_log);