I've experienced many times that when I reboot an el6 node that was running Kudu tservers, fsck reports issues like:
data6 contains a file system with errors, check forced.
data6: Interior extent node level 0 of inode 5259348:
Logical start 154699 does not match logical start 2623046 at next level.
After some investigation, I've determined that this is due to an ext4 kernel bug: https://patchwork.ozlabs.org/patch/206123/
Details in a comment to follow.