Re: lockdep annotations?

[Lachlan McIlroy <lachlan@sgi.com>]

David Chinner wrote:
> On Mon, Sep 03, 2007 at 12:46:30PM +1000, Lachlan McIlroy wrote:
>> This is a locking inversion between the iolock and iprune_mutex.  I
>> hadn't seen this one before.  Was your system running low on memory
>> at the time?
>>
>> We can't drop the iolock in the write path so we'll have to avoid
>> acquiring the iolock in xfs_ireclaim() which means we'll need another
>> way to synchronise with xfs_sync_inodes().
> 
> I don't think a deadlock exists here - we have to be going through
> memory reclaim to hit this inversion, so the only place that we
> can deadlock is if we are holding the iprune_mutex across a memory
> allocation. I don't think we do that....
> 
> Not to mention that the inode we hold the iolock on won't be on the
> inode free list so we won't ever try to lock it during reclaim, either.
> 
Yep.  This is just another case where we've confused lockdep.