Block device emulation on top of ubi volumes with read/write support

[Daniel Ehrenberg]

On Wed, Jan 20, 2016 at 4:12 PM, Richard Weinberger <richard at nod.at> wrote:
> Am 21.01.2016 um 00:54 schrieb Daniel Ehrenberg:
>> On Wed, Jan 20, 2016 at 3:30 PM, Charles Godson <cestgodson at gmail.com> wrote:
>>> Thanks for quick reply. I replaced YAFFS2 root file system with SQUASHFS on
>>> top of UBI [1], and so far it works like a charm. I am currently using UBIFS
>>> on "user" partitions. Mostly, I needed quota on them, and there was nothing
>>> in the works about a year ago. I was exploring different avenues: add quota
>>> support to UBIFS or use [2]. However, I saw that UBIFS quota support is
>>> introduced somewhere in July [3].
>>>
>>> After your explanations and suggestions above, I think ext4 is not really an
>>> option for me. Since quota support for UBIFS is already in the works, the
>>> choice is fairly clear :) .
>>>
>>> Thanks for your help on this.
>>>
>>> [1] http://lists.infradead.org/pipermail/linux-mtd/2014-February/052261.html
>>> [2] https://lwn.net/Articles/525957/
>>> [3] https://lwn.net/Articles/651925/
>>>
>>> Best regards,
>>> Charles
>>>
>> I was also looking into using squashfs on top of ubiblock, hoping to
>> write to overwrite a particular entire UBI partition with read-write
>> ubiblock support. I ended up using separate MTD partitions each
>> squashfs volume, with an UBI instance on each one, which could then be
>> updated using the ubi formatting tools, rather than writing through
>> ubiblock. Maybe UBIFS would be a better design, in retrospect.
>
> What is wrong with having a single MTD parition and multiple UBI volumes?
> You can use ubiupdatevol to update your squahsfs.
>
> Thanks,
> //richard

Oh that's right. We considered that, but ultimately decided we wanted
to isolate the partitions from each other in terms of wear leveling.

Dan