As suggested on irc channel: http://logs.tvrrug.org.uk/logs/%23btrfs/2019-03-11.html#2019-03-11T23:28:40 I should file a bug on btrfs tools:check/main.c:4728: add_data_backref: BUG_ON `!back` triggered, value 1 items checked)
after doing btrfs checkon a btrfs file system that shows 355 GB (giga) free space, but when trying to do anything on files dumps error "no space left on device".
