Seems like this particular issue has been reported here:
http://www.spinics.net/lists/linux-btrfs/msg43084.html
and fixed with upstream fix:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=3d84be799194147e04c0e3129ed44a948773b80a
which explains why 4.1-rc2 fixes this issue.
Seems like this particular issue has been reported here:
http:// www.spinics. net/lists/ linux-btrfs/ msg43084. html
and fixed with upstream fix:
https:/ /git.kernel. org/cgit/ linux/kernel/ git/torvalds/ linux.git/ commit/ ?id=3d84be79919 4147e04c0e3129e d44a948773b80a
which explains why 4.1-rc2 fixes this issue.