Re: Review: Fix dbflush panic in xfs_qm_sync

Donald Douwsma
2007-10-17T01:54:37Z

David Chinner wrote:
> On Tue, Oct 16, 2007 at 03:18:02PM +1000, Lachlan McIlroy wrote:
>> Could mp->m_quotainfo become NULL after this check but before we
>> lock the list with xfs_qm_mplist_lock()? There doesn't seem to
>> be any locking to protect changes to this field?
>
> Possible - in theory. Likely - no. We do the same unlocked check in a
> few places...
>

The mplist lock doesnt prevent the quotainfo going away while its held.
It's just guarding a hashlist that lives in quotainfo structure.
So none of this code prevents a quotaoff race.

In the short term this change restores the original checks. But in the
longer term we should review the locking in the quota system, possibly
adding a quotaoff lock to xfs_mount_t.

Don