I should add that I have reproduced this even after doing `mount -o clear_cache /dev/... /mnt/...`, unmount, remount with `-o space_cache`. After the machine lockup and rebooting there are the warnings of the form: > [ 117.288248] BTRFS warning (device dm-0): block group 694165700608 has wrong amount of free space > [ 117.288253] BTRFS warning (device dm-0): failed to load free space cache for block group 694165700608, rebuild it now -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
