[PATCH 3/3] xfs: borrow indirect blocks from freed extent when available

[Christoph Hellwig]

I've been wrapping my head around this since yersterday..

It looks reasonable, but I'd be much more comfortable if you could
split this into two patches:

 - one to just factor out a helper to update the temp and temp2
   values (great variable names while we're at it..  not your fault,
   though)
 - one to actually change the algorithm used.