[Unionfs] unionfs and sys_readahead and squashfs

[Paul Albrecht]

On Tue, 2007-11-06 at 16:12 +0000, Phillip Lougher wrote:
> On 11/6/07, Paul Albrecht <albrecht at rdi1.com> wrote:
> > Hi,
> >
> > Can I use readahead-list on on union mounted files? Whenever I use
> > readahead-list on a union mount the program hangs. If the union mount
> > includes a squashed filesystem I get a kernel oops.
> 
> Do you get a hang or kernel oops performing readahead-list directly on
> a Squashfs filesystem?  Knowing that would help narrow down the issue.
> 

There doesn't seem to be any problem using readahead-list unless the
file system is union mounted.

I have disabled readahead-list to work around the problem. If I run the
readahead-list program from the command line it segfaults. This happens
whether or not the filesystem is squashed.

> It would also be useful to see the kernel oops you're getting.
> 

As I have disabled readahead-list to work around the problem, I haven't
seen the oops for a while but I think it's failing in readpage(?).

Don't know if this helps, but I'm using ubuntu--7.04 or 7.10, doesn't
make any difference--and I noticed there's a comment in their initrd to
the effect that unionfs + squashfs don't play well together so they
disable readahead-list if they need to union mount a squashed
filesystem.

I'll try and get some more information on the oops.

Paul Albrecht