XFS write cache flush policy

[Dave Chinner]

On Tue, Dec 18, 2012 at 01:34:38AM +0100, Matthias Schniedermeyer wrote:
> On 18.12.2012 10:24, Dave Chinner wrote:
> > 
> > diff --git a/fs/xfs/xfs_sync.c b/fs/xfs/xfs_sync.c
> > index 9500caf..7bf85e8 100644
> > --- a/fs/xfs/xfs_sync.c
> > +++ b/fs/xfs/xfs_sync.c
> > @@ -400,7 +400,7 @@ xfs_sync_worker(
> >  	 * 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) &&
> > +	if ((mp->m_super->s_flags & MS_ACTIVE) &&
> >  	    !(mp->m_flags & XFS_MOUNT_RDONLY)) {
> >  		/* dgc: errors ignored here */
> >  		if (mp->m_super->s_writers.frozen == SB_UNFROZEN &&
> > 
> > 
> 
> This also appears to fix the other case.
> When the activity ceases sharply and the log is still not written after 
> minutes.
> 
> After writing 10 files, waiting a minute, yanking ... all 10 files where 
> there.
> So the OP-case MIGHT have been this same error.
> But that's the amateuer talking again.

I kinda deserved that, didn't I? ;)

But now I understand the problem, I agree with you that the OP was
probably seeing the same bug. I understand the cause, and can
explain exactly how it would cause both sets of symptoms reported...

Cheers,

Dave.
-- 
Dave Chinner
david at fromorbit.com