It duplicates fs/mpage.c in bio building and introduces new generic API
(iomap, map_blocks_t, etc). In contrast, my trivial implementation re-use
existing code in fs/mpage.c, doesn't introduce new API and I tend to think
provides quite the same functionality. I can be wrong, of course ...

thanks, Alex

Jeff Garzik wrote:

The XFS one is proven and the work was already completed.

What were the specific technical issues that made it unsuitable for ext4?

I would rather not reinvent the wheel, particularly if the reinvention 
is less capable than the existing work.

    Jeff