Fullfil the bmap operation

Hi,

When we tested btrfs with Josef's test-tools, a FAIL came to us.

After looking into it, we found that aops->bmap had been deleted because btrfs's COW + swapfile led to corruption.

So, is there a plan for this bmap operation?

The idea was the swap over NFS patches were going to help. Until then it is better to use fiemap anyway.

-chris