XFS Invalid block length (0x0) for buffer

xfs_repair /dev/vgpool/lvol1
Phase 1 - find and verify superblock...
- reporting progress in intervals of 15 minutes
Phase 2 - using internal log
- zero log...
Invalid block length (0x0) for buffer
Log inconsistent (didn't find previous header)
empty log check failed
zero_log: cannot find log head/tail (xlog_find_tail=5)
ERROR: The log head and/or tail cannot be discovered. Attempt to mount the
filesystem to replay the log or use the -L option to destroy the log and
attempt a repair.

I have not found much about this on the web but in one place someone said it relates to an underlying hardware problem so the disk (spinning, SSD) is in a zombie state and near to a complete failure.
You should get identical disk, clone it and check the filesystem damage.