[Unionfs] unionfs and sys_readahead and squashfs

[Phillip Lougher]

On Nov 9, 2007 5:56 PM, Paul Albrecht <albrecht at rdi1.com> wrote:
> On Fri, 2007-11-09 at 12:39 -0500, Erez Zadok wrote:
> > In message <1194629290.3270.2.camel at albrecht.rdi1.com>, Paul Albrecht writes:
> > > On Thu, 2007-11-08 at 20:55 -0500, Erez Zadok wrote:
> > > > Paul, I'm happy to report that I wasn't able to reproduce this bug with
> > > > unionfs-2.1.8 and 2.6.24-rc1.
> > > >
> > >
> > > OK, Thanks for the update. I didn't explain how I got the kernel oops so
> > > to make sure the bug got squashed, here's how I triggered the oops using
> > > ubuntu 7.10:
> > >
> > > echo "/mnt/bin/bash" > readlist
> > > mkdir -p /cow
> > > mount -t tmpfs tmpfs /cow
> > > mount -t unionfs -o dirs=/cow=rw;/=ro unionfs /mnt
> > > readahead-list readlist
> >
> > Just to confirm, but on my Fedora Core system, there's just a program called
> > /usr/bin/readahead: I think that's the same one b/c it also takes an arg
> > which is a file list.  Right?
> >
>
> Yes, readahead-list takes a file list as an argument. The list includes
> a file in a union mounted filesystem and that triggers the kernel oops.
> If you strace the call to readahead-list, you'll see the call the
> readahead syscall. When I do the systrace, I get a segfault which
> terminates the readahead syscall.
>
> > > > I've offered to help the ubuntu guys move to unionfs-2.x.  I hope now that
> > > > their new release is done, they'd have more time to work with me on this
> > > > upgrade.
> > >
> > > When ubuntu git repos for kernel and module source get upgraded will that be
> > > for "gutsy gibbon" or "hardy heron?"
> >
> > I don't know.  My understanding was that the apparmor patches are an issue.
> >
> > > Paul Albrecht
> >
>
> I think this is really a question for Phillip as I think he is a member
> of the canonical kernel team.
>
> Phillip, Any idea? Anything I can do to help?
>

As I implied in my previous email, the apparmor patches caused us
problems but these were all solved.  As far as my understanding is
concerned, the current issue is likely to be problems with the liveCD.

I've been off work for the last 7 weeks, and I've missed all the Hardy
Heron planning sessions, and so I don't know what the Hardy Heron
kernel roadmap will be.  I'll be surprised if there isn't time to look
into putting Unionfs 2.x into the Hardy kernel, but, I don't know when
or if that will happen at the moment.

Phillip

> Paul Albrecht
>