Re: Review: Fix dbflush panic in xfs_qm_sync

[Christoph Hellwig <hch@infradead.org>]

On Tue, Oct 16, 2007 at 09:29:23AM +1000, Donald Douwsma wrote:
> The recent behaviour layer removal dropped the check for quotas that have 
> been
> requested at mount time but have subsequently been turned off. This results
> in a panic when accessing m_quotainfo which has been freed.
> 
> This patch adds the check originally made by xfs_qm_syncall() to 
> xfs_qm_sync()

Hmm.  We do the same check just a few lines below, but inbetween
we access ->m_quotainfo to take the lock.  I was under the impression
that's the only safe way to check anyway, but ->m_quotainfo might not
actually be present.  It might me better to move the lock into xfs_mount
directly, but it's embedded into a xfs_dqhash and there's some complex
mess with gazillions of macros around it.

So I suspect restoring it to the original state might be good enough.