Subject: XFS read-only bind mount issue
From: Eric Schoeller <eschoeller@users.sourceforge.net>
Date: Wed, 31 Mar 2010 21:15:51 -0600

Good Evening,

I have an interesting problem that apparently seems to be vserver 
related. I have an XFS filesystem on a Debian Lenny host that I bind 
mount on several linux-vserver guests, all running Debian Lenny as well. 
Some guests bind mount this filesystem read-only, others read-write. 
After a clean reboot, all guests and the host O/S have no trouble 
accessing this filesystem. Once I restart a guest which bind mounts this 
filesystem read-only the entire host no longer has read/write access. I 
see nothing in dmesg or syslog about this apparent "re-mount read-only" 
behavior.

To fix this issue, I have to stop all guests that have this fileystem 
bind-mounted, unmount it from the host O/S and then re-mount it. Once I 
fire up a single guest with the read-only bind-mount, the problem occurs 
again. Now, if I switch one of these read-only guests to bind-mount 
read/write the problem is resolved. If it's not a vserver issue (which 
is entirely likely) any hint on where else I should be looking is 
greatly appreciated.

I first observed this problem after an upgrade to 2.6.22.19-vs2.2.0.7 
which I built myself. After reading about various XFS issues in "recent" 
kernels I tried using an image from the psand repository: 
2.6.31.12-vs2.3.0.36.28-beng. I still observe the same behavior. Up 
until this recent upgrade I had been using the debian etch kernel 
2.6.18-6-vserver-amd64. Oddly, switching back to this kernel doesn't 
resolve the issue, so perhaps it's not vserver related at all ... or it 
could be util-vserver related. I haven't tried changing my util-vserver 
version yet.

Thanks!

Eric