btrfs file usage output incorrect for RAID10?

resumably calculated by subtracting the size of the data and metadata from the total size of the disk, is therefore incorrect. Can someone familiar with the source code of btrfs-progs confirm if this is correct or, if the figures are correct, my RAID1 is actually being converted to RAID0! Thank

kernel BUG as fs/btrfs/extent-tree/c:1833 while executing device remove under 4.2.0-rc5

btrfs xor raid6_pq dm_mod hid_generic usbhid hid sd_mod usb_storage ohci_pci tg3 ptp pps_core libphy ahci libahci libata ehci_pci ohci_hcd ehci_hcd scsi_mod usbcore usb_common Aug 15 10:42:44 capella kernel: CPU: 1 PID: 95 Comm: kworker/u8:7 Tainted: P O4.2.0-rc5-derek-00033-g6c84461-di