summarise aufs issues and possible patches

[Amit Kucheria]

Hi Junjiro,

On Wed, Feb 25, 2009 at 7:42 AM,  <hooanon05 at yahoo.co.jp> wrote:

<snip>

> Latest aufs is version 2 (aufs2) which was born responding the
> discussion at last UDS. It supports linux-2.6.27 and later, but some
> features/configurations are dropped in order to make source files
> simpler and easier to be reviewed. I found the ubuntu configuration
> enables CONFIG_AUFS_{EXPORT,SHWH,STAT}. If these features are important
> for ubuntu users, you cannot switch to aufs2 yet.

I don't think we use AUFS_SHWH and AUFS_STAT internally. It was
probably enabled as part of the configs carried over from Intrepid and
never reviewed.

> And I suspended maintaining aufs1 (which ubuntu adopts), so aufs1
> doesn't support linux-2.6.28.
>
> Finally there are several ways we choose.
>
> - Jaunty keeps old aufs1
>  This is the easiest way. You may want to select it until an actual
>  problem will be reported.

Since Jaunty is now in feature freeze, we would _not_ like to remove
version of AUFS and put in a completely new version. So, IMO we would
like to stick with Option 1 unless there is a very serious problem
with aufs1.

> - I upgrade aufs1 to support 2.6.28 and Jaunty adopts it
>  Because aufs2 is very new and doesn't support
>  CONFIG_AUFS_{EXPORT,SHWH,STAT}, you may want to keep using aufs1. In
>  this case, I will modify the latest aufs1 to support 2.6.28 (or
>  later). Also I may have to follow some ubuntu specific kernel changes.
>  You can keep on using the aufs features which are curretnly enabled in
>  ubuntu kernel.
>  FYI, debian stable(5.0.0, lenny)/testing/unstable adopt aufs1
>  20080714+their patch. And debian experimental adopts aufs1
>  20081208+their patch currently.
>
> - Jaunty adopts aufs2
>  This is my recommendation, but I can understand that you may not like
>  it. It is smaller and faster(hopefully) than aufs1 and support
>  linux-2.6.27 and later (but not yet 2.6.29-rcN).
>  In this case you cannot select CONFIG_AUFS_{EXPORT,SHWH,STAT}.

IMO, Ubuntu will start using aufs2 starting in Jaunty+1 on the
2.6.30-rc kernels. In the meanwhile, hopefully you will have more
feedback from LKML about upstreaming aufs2. I see that you have just
submitted aufs2 again.

Regards,
Amit