ext4: fix indirect punch hole corruption

Please include the following commit into 3.17.y, 3.18.y, and 3.19.y stable trees.
commit 6f30b7e37a8239f9d27db626a1d3427bc7951908

Author: Omar Sandoval <[email protected]>
Date:   Sat Feb 14 20:08:51 2015 -0500

ext4: fix indirect punch hole corruption

This bug fixes several corner case bugs related to hole punching on EXT file systems that use indirect mapping. One case was reproduced here, and I've tested with this patch and it resolves the issue:
http://bugs.launchpad.net/bugs/1292234

I've also been able to cherry-pick these cleanly into the aforementioned trees and they build. I've only tested on 3.19. I believe Omar may have additional test cases.

Thanks,
--chris j arges