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

Dave Chinner
2012-09-05T04:29:05Z

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.
--
Dave Chinner
david@fromorbit.com