btrfsck --repair /dev/sdf1
enabling repair mode
WARNING:

	Do not use --repair unless you are advised to do so by a developer
	or an experienced user, and then only after having accepted that no
	fsck can successfully repair all types of filesystem corruption. Eg.
	some software or hardware bugs can fatally damage a volume.
	The operation will start in 10 seconds.
	Use Ctrl-C to stop it.
10 9 8 7 6 5 4 3 2 1
Starting repair.
Opening filesystem to check...
Checking filesystem on /dev/sdf1
UUID: 314a88f5-d210-4c03-b79b-8c284e9de0ca
[1/7] checking root items
Fixed 0 roots.
[2/7] checking extents
No device size related problem found
[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 5988193943552 bytes used, no error found
total csum bytes: 5835425576
total tree bytes: 10667114496
total fs tree bytes: 4041867264
total extent tree bytes: 429441024
btree space waste bytes: 996912757
file data blocks allocated: 6038381948928
 referenced 6257201074176