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From: Liam Helmer (lists_at_strongboxlinux.com)
Date: Mon 12 Jul 2004 - 20:58:07 BST

Hey Herbert,

We chatted a bit about this on IRC, but I wanted to try and get this
resolved, so I'll make a more thorough report on the matter:

I'm using kernel 2.6.7 with vserver 1.9.2-rc5.
The problem I'm running into is with the squashfs file system
(http://squashfs.sf.net). This bug affects both the development version
(2.0Alpha) and the stable version (1.3r3).

I'm using the new vserver tools: version 0.29.214. The problem is not
with the legacy tools, it's only with the new tools/system calls. It
only affects vserver > 1.9.1... 1.9.1 seems unaffected by this.

So, the simplest test scenario:

1) Create a squashfs file with binary excecutables in it
2) Mount it as a loop device

Then excecute:
3) #vcontext --create --xid 100 md5sum /loopdir/*
4) #vcontext --create --xid 101 md5sum /loopdir/*

The second command (in context 101) will fail, with each file giving
permission denied messages.

If you then excecure:

#vcontext --create --xid 100 md5sum /loopdir/*

That will work fine.

Also, if you do md5sum /loopdir/* beforehand from context 0, you'll get
no errors in either context.

My current theory is that the filesystem cache that squashfs creates for
one virtual context is unreadeable by other virtual contexts, resulting
in the permission denied errors. Squashfs is a compressed filesystem, so
it creates it's own filesystem cache to speed up read times. I've sent
off a couple of emails to the creator of squashfs as well.

So, do you have any ideas as to how this could be resolved?


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