Re: [PATCH 03/13] xfs: rationalise xfs_mount_wq users

Dave Chinner
2012-09-06T00:45:11Z

On Wed, Sep 05, 2012 at 08:16:59AM -0500, Mark Tinguely wrote:
> On 09/04/12 23:30, Dave Chinner wrote:
> >On Tue, Sep 04, 2012 at 10:48:17AM -0500, Mark Tinguely wrote:
> >>On 08/30/12 07:00, Dave Chinner wrote:
> >>>- /*
> >>>- * 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 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 (!(mp->m_super->s_flags& MS_ACTIVE)&&
> >>>- !(mp->m_flags& XFS_MOUNT_RDONLY)) {
> >>>+ if (!(mp->m_flags& XFS_MOUNT_RDONLY)) {
> >>> /* dgc: errors ignored here */
> >>> if (mp->m_super->s_writers.frozen == SB_UNFROZEN&&
> >>> xfs_log_need_covered(mp))
> >>>@@ -408,8 +398,7 @@ xfs_sync_worker(
> >>> else
> >>> xfs_log_force(mp, 0);
> >>>
> >>>- /* start pushing all the metadata that is currently
> >>>- * dirty */
> >>>+ /* start pushing all the metadata that is currently dirty */
> >>> xfs_ail_push_all(mp->m_ail);
> >>> }
> >>>
> >>
> >>It appears that the removal of the MS_ACTIVE flag is causing the
> >>"atomic_read(&bp->b_hold)> 0," ASSERT.
> >
> >I must be being slow today - I don't see why that would cause any
> >problems. The worker is not started at the end of the mount process
> >after everything is set up (i.e. just before MS_ACTIVE is removed),
> >and the worker is stopped before anything is torn down. That should
> >effectively replicate what the MS_ACTIVE flag is providing in the
> >old code.
> >
> >Can you explain in more detail what lead you to this conclusion?
> >
> >Cheers,
> >
> >Dave.
>
> You are correct, it does not make sense, but with the
> !(mp->m_super->s_flags & MS_ACTIVE)
> test removed, test 107 causes the above assert on
> different machines/architectures. Place the test in, the
> assert does not happen.

test 107 is not in the auto group. That means it is generally
unreliable as a regression test, so I don't run it. That said, I
don't see anything unusual in that test that would cause problems...

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com