[patch] Allow any filesystem on MTD Nand when Read Only

[Pantelis Antoniou]

Hello there.

The following patch allows you to have any filesystem over NAND when mounted
read only.

The main drive for this was that I wanted to use CRAMFS over NAND flash 
since
it has a much higher compression ratio than JFFS2.

How it works is pretty simple.

It's pretty reasonable assumption that bad blocks are created only when
writting to NAND. So in the read-only case it is possible to skip over 
the bad
blocks and offer a bad-block free block device to the upper layers.
This allows us to utilize any filesystem when  read-only.

In order to speed the mount operation the bad block detection is 
performed lazilly.

Using the patch I was able to mount as read-only CRAMFS/JFFS2 partitions
which contained simulated bad-blocks.

Awaiting your comments...

Regards

Pantelis

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