[RFC] [MTD-utils] mkfs.jffs2: JFFS2 and minimal erase block size

[Artem Bityutskiy]

On Wed, 2010-09-01 at 17:36 +0200, Yegor Yefremov wrote:
> Hello,
> 
> I'm using a NOR flash SST39VF3201. According to its data sheet the
> erase size is 2 Kword. That corresponds to -e 0x1000 value. But the
> mkfs.jffs2 utility has a limit of 0x2000 bytes. If I change this limit
> to 0x1000 and create an image, I can successfully mount and use it,
> with 8KiB value the jffs2 driver fails to work with such an image. I
> have found some similar complains like this one
> http://lists.infradead.org/pipermail/linux-mtd/2009-February/024523.html,
> but no one seems to have asked this question on the list.
> 
> Is there any reason for limiting erase block to 0x2000?
> 
> I've created a patch to decrease this value to 0x1000, but perhaps
> there are any other way?

JFFS2 should be able to fit at least one node to eraseblock. The maximum
node size is 4KiB+few bytes. This is why the minimum eraseblocks size is
8KiB.

But in practice, even 8KiB is bad because you and up with wasting a lot
of space at the end of eraseblocks.

You should join several erasblock into one virtual eraseblock of 64 or
128 KiB and use it - this will be more optiomal.

So, nack for the patch.

-- 
Best Regards,
Artem Bityutskiy (Битюцкий Артём)