Re: [RFC/PATCH 0/1] ubi: Add ubiblock driver

Ezequiel Garcia
2012-11-24T21:03:02Z

Hi Thomas and everyone,

On Wed, Nov 21, 2012 at 7:05 AM, Thomas Petazzoni
<thomas.petazzoni@free-electrons.com> wrote:
> Dear Ricard Wanderlof,
>
> On Wed, 21 Nov 2012 11:00:49 +0100, Ricard Wanderlof wrote:
>
>> > The idea, when David Wagner implemented this, was to be able to use
>> > read-only block filesystems such as squashfs on top of a UBI volume.
>> > squashfs provides an excellent compression ratio, which makes it
>> > interesting.
>>
>> Yes, I agree, that would be useful.
>
> Yes, but only the read-only side of ubiblock. The write side is
> dangerous and useless, IMO.
>

I've started working on a workload scenario to measure if ubiblock write
is useful or just plain nonsense.

This scenario is based on qemu + nandsim, and the workloads
consists on mounting a fs over nandsim and untaring an armstrong distribution.
I plan to compare eraseblock wear on ubifs, jffs2, ubiblock+ext2, ubiblock+f2fs.

To get eraseblock wear I've patched nandsim to output wear report
on a debugfs entry, instead of printing it.
I'll post this patch in case because it may turn out to be useful.

Since read-only ubiblock is less controversial, I'll post a read-only
version of ubiblock (with an option to use a vmalloced
buffer to cache reads?).
We can add write support later, if it's not useless.

Any thoughts?

Thanks,

Ezequiel