Greg, Please add mainline commit 848c23b78faf aka: "btrfs: Remove false alert when fiemap range is smaller than on-disk extent" to the 4.12-stable pile. It fixes false-positive WARNING noise which spams people's logs for no reason, as discussed e.g. in: https://www.mail-archive.com/linux-btrfs@xxxxxxxxxxxxxxx/msg66660.html It should apply cleanly to 4.12. Thanks, Holger