block allocations for the refcount btree

[Dave Chinner]

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 at fromorbit.com