UBIFS read-only rootfs needs 1 or more eraseblocks to mount

[Darwin Rambo]

On a read-only UBIFS rootfs, why do you need at least 1 eraseblock? There is nothing to replace since nothing is ever written to this partition on the fly and a block that goes bad cannot be recovered anyways?

UBI error: ubi_eba_init_scan: no enough physical eraseblocks (0, need 1)
UBI error: ubi_init: cannot attach mtd6
UBI error: ubi_init: UBI error: cannot initialize UBI, error -28

Note that adding room for a single bad block PEB allows the mount to work, and you get a warning like this:
"UBI warning: ubi_eba_init_scan: cannot reserve enough PEBs for bad PEB handling, reserved 0, need 19"

It looks like the normal read/write code is reserving/requiring blocks that the read-only mode doesn't actually use? All this is probably just a future suggestion to support read-only mode a little bit better with less block wastage.

Thanks.
Darwin