Pull btrfs data corruption fix from Chris Mason:
"I'm testing a pull with more fixes, but wanted to get this one out so
Greg can pick it up.
The corruption isn't easy to hit, you have to do a readonly snapshot
and have orphans in the snapshot. But my review and testing missed
the bug. Filipe has added a better xfstest to cover it"
* 'for-linus-update' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs:
Revert "Btrfs: race free update of commit root for ro snapshots"