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Re: block allocations for the refcount btree

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: block allocations for the refcount btree
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Sun, 14 Feb 2016 11:21:35 +1100
Cc: "Darrick J. Wong" <darrick.wong@xxxxxxxxxx>, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20160213074827.GA11543@xxxxxxxxxxxxx>
References: <20160210093011.GA19147@xxxxxxxxxxxxx> <20160210095010.GC23904@xxxxxxxxxxxxxxxx> <20160210190738.GA13051@xxxxxxxxxxxxx> <20160210214058.GN14668@dastard> <20160212191046.GA28421@xxxxxxxxxxxxx> <20160213023310.GC14668@dastard> <20160213074827.GA11543@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Fri, Feb 12, 2016 at 11:48:27PM -0800, Christoph Hellwig wrote:
> On Sat, Feb 13, 2016 at 01:33:10PM +1100, Dave Chinner wrote:
> > > allocate an extent (or rather just a single block) in xfs_alloc_ag_vextent
> > > as called from xfs_refcountbt_alloc_block.  The reservation helps us to
> > > ensure this block is always available, but we still need to account for
> > > that in xfs_trans_reserve(), which we currently don't do for itruncate
> > > transactions.  
> > 
> > Ok, so we may have two different issues with a similar failure
> > symptom. As it is, I don't think this is a show stopper - we're
> > expecting to find these sorts of issues as we go along (hence the
> > experimental tag on the feature) and I think, at this point, getting
> > review and an initial merge done is more important...
> 
> This triggers 100% reproducible over NFS, and as outlined I'm
> also pretty sure about the root cause.  I don't think this is something
> to be ignored.

I didn't say we should to ignore it - I simply stated my priority
was getting the code reviewed and merged.  That doesn't stop you or
Darrick from working on a fix - if that happens after the initial
merge, we've still got the whole -rc cycle to find and fix issues
like this.

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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