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Re: XFS reclaim lock order bug

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: XFS reclaim lock order bug
From: Nick Piggin <npiggin@xxxxxxxxx>
Date: Wed, 24 Nov 2010 11:58:11 +1100
Cc: Nick Piggin <npiggin@xxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <20101123211258.GY22876@dastard>
References: <20101123121802.GA4785@amd> <20101123211258.GY22876@dastard>
User-agent: Mutt/1.5.20 (2009-06-14)
On Wed, Nov 24, 2010 at 08:12:58AM +1100, Dave Chinner wrote:
> On Tue, Nov 23, 2010 at 11:18:02PM +1100, Nick Piggin wrote:
> > Hi,
> > 
> > IIRC I've reported this before. Perhaps it is a false positive, but even
> > so it is still annoying that it triggers and turns off lockdep for
> > subsequent debugging.
> > 
> > Any chance it can get fixed or properly annotated?
> 
> It is supposed to be handled by the re-initialisation of the
> ip->i_iolock in ->evict_inode (xfs_fs_evict_inode). An inode found
> in the reclaim state must have passed through this reinitialisation,
> so from a lockdep perspective the iolock in the vfs path is a
> different context to the iolock in the reclaim path. That fixed all
> the non-reclaim state related lockdep false positives, so Perhaps
> there is an issue with the lockdep reclaim state checking that does
> not interact well with re-initialised lock contexts?

Hmm. I suppose that should work.

So xfs_reclaim_inode can only call xfs_ilock _after_ the Linux inode
has gone through ->evict_inode call? If so, then let's ask the lockdep
people.

Thanks,
Nick

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