laci200270@lacinote ~ $ sudo btrfsck --readonly /dev/sdb1
Opening filesystem to check...
Checking filesystem on /dev/sdb1
UUID: 5a578c37-6ec2-48fa-808f-480b96d6a286
[1/7] checking root items
[2/7] checking extents
[3/7] checking free space cache
cache and super generation don't match, space cache will be invalidated
[4/7] checking fs roots
[5/7] checking only csums items (without verifying data)
[6/7] checking root refs
[7/7] checking quota groups skipped (not enabled on this FS)
found 1415857594368 bytes used, no error found
total csum bytes: 1376862936
total tree bytes: 5599068160
total fs tree bytes: 3839393792
total extent tree bytes: 210993152
btree space waste bytes: 775719124
file data blocks allocated: 60372213657600
 referenced 1404108206080