The USB storage area file system is corrupt.
Enter the 'Recovery Menu' -
use the 'Format USB storage' (or similar name) on the device -
then reboot.
Don't try to re-format it from Windows, it uses some non-MicroSoft configuration options.
- - - -
/var/local (mmcblk0p3) may be corrupt also.
What with the unexpected changes to mmcblk0p2 -
we may have to intentionally use that 'Erase MMC' option and then re-load it with fastboot.
So make sure you have a copy of the GRAYSCALE Kindle (not the fire (Android)) fastboot for your PC and that it is working with your Kindle before doing the 'Erase All' trick.
Note: If (it is very much a 'last choice' thing) this has to be done, it will be the first time in forum history that it was done intentionally - all others, it was unintentional.