[Fwd: Maverick Union Mount Solution]

[Pete Graner]

Forwarding to ubuntu-devel for wider comment.


-------- Forwarded Message --------
From: Andy Whitcroft <apw at canonical.com>
To: Ubuntu Kernel Team <kernel-team at lists.ubuntu.com>
Subject: Maverick Union Mount Solution
Date: Thu, 24 Jun 2010 19:10:40 +0100

As for the Lucid cycle we have been evaluating whether VFS union-mounts
are feature rich and stable enough to use as our union mounts solution
of choice for Maverick, allowing us to deprecate aufs2 for an upstream
supported solution.  The union-mounts patches have seen a resurgence in
activity of late, indeed there has been two new sets of patches posted.
The latest of these is still only based on v2.6.34, some signicant
changes affecting this code have dropped since then making a roll-forward
difficult.  These patches also come with the note that the next step is
significant work to fix other review comments.  In short although progress
is swift these patches are not yet stable enough even to readily test
in the Ubuntu kernel and certianly not in a state where we could switch
to them before Alpha-3.  I do not think it is practicle to consider
any change of union-mount solution later than that.  The recommendation
therefore is that we put VFS union-mounts on the list for re-evaluation
for the N-cycle and continue to use aufs2 for Maverick.

Looking at the current aufs2 tree there are some updates and a slightly
different fix for the compile issues we saw in the existing code.
However I have just boot tested the latest nightly ISO which contains the
2.6.35-5.6 (2.6.35-rc3 based) kernel and the aufs2 implementation there
seems to hold together enough to boot the live image to the desktop.
Therefore given the kernel freeze date is tommorrow (25th Jun 2010) I do
not propose we touch aufs2 before Alpha-2.  I will add a task to re-update
aufs2 before Alpha-3, with a view to doing so right after Alpha-2 freeze
is done.

-apw


-- 
Pete Graner     <pgraner at canonical.com>
Manager         
Ubuntu Kernel   
Canonical Ltd.  http://www.canonical.com/