[PATCH] xfs: shutdown xfs_sync_worker before the log

Ben Myers
2012-05-25T20:40:16Z

Hey Dave,

On Thu, May 24, 2012 at 05:39:52PM -0500, Ben Myers wrote:
> Anyway, I'll make some time to work on this tomorrow so I can test it over
> the weekend.

This is going to spin over the weekend. See what you think.

-----------

xfs: shutdown xfs_sync_worker before the log

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.

Index: xfs/fs/xfs/xfs_log.c
===================================================================
--- xfs.orig/fs/xfs/xfs_log.c
+++ xfs/fs/xfs/xfs_log.c
@@ -810,6 +810,7 @@ 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);
}
Index: xfs/fs/xfs/xfs_sync.c
===================================================================
--- xfs.orig/fs/xfs/xfs_sync.c
+++ xfs/fs/xfs/xfs_sync.c
@@ -386,23 +386,23 @@ 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_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);
+ 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);

- /* start pushing all the metadata that is currently
- * dirty */
- xfs_ail_push_all(mp->m_ail);
- }
- up_read(&mp->m_super->s_umount);
+ /* start pushing all the metadata that is currently
+ * dirty */
+ xfs_ail_push_all(mp->m_ail);
}

/* queue us up again */