Re: ubiblock RW

[Richard Weinberger <richard@nod.at>]

Hi!

Am 24.03.2016 um 15:23 schrieb Ezequiel Garcia:
> +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?

I'm definitely not fond of adding write support to ubiblock without turning it into a proper FTL.
Otherwise it will be abused and will cause serious damage.

Regarding encryption, encryption for UBIFS is in the pipes, Dave and I did already some preliminary
work. It will materialize within this year, depending on how much we get distracted by other projects.
So far it is a spare time project. The plan is adding file level encryption like ext4 and f2fs have.

Thanks,
//richard