lofi does mismanage size(9P) properties
Test: /opt/zfs-tests/tests/functional/slog/slog_013_pos (run as root) [00:01] [FAIL]
The failure was caused by:
00:56:17.88 ERROR: /usr/sbin/zpool add testpool.457037 log /dev/lofi/1 exited 1
While investigating I found that Nblocks / Size properties are actually set wrong and does not conform to description in size(9P). Implemented change does fix this use case.