Re: review: use correct buffer flags when reading superblock

[Lachlan McIlroy <lachlan@xxxxxxx>]

Christoph Hellwig wrote:
> On Wed, Oct 10, 2007 at 09:25:06PM +1000, David Chinner wrote:
> > > Where are these set up in the first time?  AFAICS the buffer only written
> > > out by xfs_unmountfs_writesb, xfs_syncsub and xfs_trans_log_buf, and all
> > > these should only ever happen after log recovery has finished.
> > It can also be written by xfsbufd when it has been bdwrite()
> > or as a result of log tail pushing.
> Hmm, true.
>
> > Because the superblock buffer is XBF_FS_MANAGED, it does not get
> > torn down when it is clean and has no references, so the XBF_ASYNC
> > flag never gets cleared unless the fs specifically clears it. If the
> > superblock is then not recovered out of any further transactions
> > during recovery after xfsbufd flushed it, the XBF_ASYNC flag remains
> > set for the re-read that is issued in xlog_do_recover() and we
> > hang.....
> Makes sense as an explanation.  I still don't really like patch, maybe
> we should always clear the ASYNC flag in the b_iodone callback?
That sounds like a good idea.  Or get rid of the XBF_FS_MANAGED special
case and get a new fresh buffer each time.