Hi, thanks for the report, I've forwarded it to the issue tracker https://github.com/kdave/btrfs-progs/issues/148 The show command uses the information provided by blkid, that presumably caches that. The default behaviour of 'fi show' is to skip mount checks, so the delays are likely caused by blkid, but that's not the only possible reason. You may try to run the show command under strace to see where it blocks.
