Re: ubiblock RW

Ezequiel Garcia
2016-03-24T14:24:37Z

+MTD

On 23 March 2016 at 14:40, Benson Young <benson6877@gmail.com> wrote:
> Hello Ezequiel,
>
> I came upon the discussion about block device emulation over UBI.
> http://linux-mtd.infradead.narkive.com/YF0XOFxY/block-device-emulation-on-top-of-ubi-volumes-with-read-write-support
>
> I understand the most recent implementation is read-only emulation for
> mounting squashfs based file system.
> However, I would really like to see the write option be brought back. If
> not, can you please help me about enabling the write option in my build?
> I have used the patch listed in the following link
> https://lwn.net/Articles/525957/
> but i couldn't find any accompanying util that allows me to create the ubi
> block volume.
>

You should be able to use mtd-utils' ubiblock tool (maybe you'll need to do
some modifications).

http://www.linux-mtd.infradead.org/doc/ubi.html#L_ubiblock

> Reason for this request is that I am looking into root file system
> encryption over un-managed NAND flash. Now the mainline method of disk
> encryption in Linux revolves around
> dm-crypt module which requires a block device. i am under the impression
> that using mtdblock works to an extent until the partition you try to
> map/encrypt has bad blocks in it.
> I have seen discussion about using UBIFS, and I have seen a paper discussing
> it, where the author embeds the encryption engine within UBI layer, so each
> write and read is encrypted. However, its a path I would take when I have no
> choice. Right now dm-crypt is my first choice basically because of the
> availability of support/discussion/information.
>
> I also saw you mentioned that you don't have NAND flash for testing, this is
> something that I can help with. I have an abundance of NAND flash devices.

I have some devices with SLC NANDs now, but thanks for the offer.

> For simplicity sake, I work with SLC because of better endurance compared to
> MLC. I am also curious about flash endurance with EXT4 over UBI. Destructive
> erase/write will definitely on my to-do list.
>

So, like I said here:

http://linux-mtd.infradead.narkive.com/YF0XOFxY/block-device-emulation-on-top-of-ubi-volumes-with-read-write-support

We can definitely implement write support if we have a good use case for it.
Encryption might be one.

Richard, what do you think?
--
Ezequiel García, VanguardiaSur