How does UBI FS handle invalid PEB on nand flash

[Steven Munk Østergaard]

Been reading all of the available documentation on UBI and UBIFS but I 
cannot  find a clear statement on how UBIFS handles production marked 
invalid PEB's, and if their location is saved; So when a format is done, 
this information is not lost.

is there a way to make sure UBIFS allways checks for production marked 
invalid PEB's when a device is started the first time?

Thanks in advance, hope the questions aren't too stupid. :)

- Steven Lauridsen