How to reserve disk space in XFS to make the blocks over many files continuous?

[Roger Willcocks]

> > My question is, how can I guarantee the file system blocks over files
> > continuous? Thanks for your time and appreciate your answer.
> 
> You can't, directly. 

We needed to do this so I added code to swapext to support transferring
leading blocks from one (preallocated single extent) file to another
empty file. It's pretty straightforward but perhaps too special case for
general consumption.

-- 
Roger Willcocks <roger at filmlight.ltd.uk>