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

To: Mark Tinguely <tinguely@xxxxxxx>
Subject: Re: [PATCH 03/13] xfs: rationalise xfs_mount_wq users
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Wed, 5 Sep 2012 14:30:00 +1000
Cc: xfs@xxxxxxxxxxx
In-reply-to: <504622C1.20201@xxxxxxx>
References: <1346328017-2795-1-git-send-email-david@xxxxxxxxxxxxx> <1346328017-2795-4-git-send-email-david@xxxxxxxxxxxxx> <504622C1.20201@xxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
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@xxxxxxxxxxxxx

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