Re: Review: fix null files exposure growing via truncate V2

[Lachlan McIlroy <lachlan@sgi.com>]

Looks good to me.  Thanks for fixing it Dave.

David Chinner wrote:
> Test 140 fails due to the ftruncate() logging the new file size
> before any data that had previously been written had hit the
> disk. IOWs, it violates the data write/inode size update rule
> that fixes the null files problem.
> 
> The fix here checks when growing the file as to whether it the disk
> inode size is different to the in memory size. If they are
> different, we have data that needs to be written to disk beyond the
> existing on disk EOF. Hence to maintain ordering we need to flush
> this data out before we log the changed file size.
> 
> Version 2:
> 
> o Only flush the range between the old on disk size and the current
>   in memory size.
> 
> Cheers,
> 
> Dave.