Comment 213 for bug 1470250

I also plan on building a test kernel with just commit cd4842f4 reverted. It's not straight forward because a later xfs commit started using a function added by this commit(set_page_writeback_keepwrite()).

I think the easiest thing for testing and confirming this is the bad commit is to just drop the xfs commit as well, for now. If cd4842f4 ends up being the bad commit, we can also address the xfs dependency with the patch authors and ext4 maintainers.