Re: unable to mount using overlayfs.v22 on kernel 3.15.5

From: Klaus A. Kreil
Date: Thu Jul 24 2014 - 09:49:00 EST


Woody,
my message obviously ended up in the wrong list due to a mistake of mine. I originally thought it got lost until your reply as I am not subscribed to linux-kernel@xxxxxxxxxxxxxxxx

But: There is already a discussion about this issue going on at linux-unionfs@xxxxxxxxxxxxxxx with Miklos Szeredi, the author of overlayfs.

He has kindly pointed me towards the correct list when I sent him a PM about the problem and he rightly has taken the issue to linux-unionfs@xxxxxxxxxxxxxxxx I think it would be good if you joined us there to keep related things together.

Thanks,

Klaus

Am 24.07.14 14:14, schrieb Woody Suwalski:
Klaus A. Kreil wrote:
Hello list,
I have just found out about this mailing list which obviously also
takes care of overlayfs.

I have been a happy user of overlayfs for quiet some time using it to
propagate a shared r/o LVM ext4 lowerdir rootfs with a small r/w ext4
upperdir for a number of XEN domU guests. I started with overlayfs on
kernel version 3.11.7 (all on gentoo-hardened). Recently I have
switched from 3.13.10 (using overlayfs.v21) to 3.15.5 with overlayfs.v22.

overlayfs.v22 seems to have changed insofar as there's a new parameter
workdir=/dir with dir required to be an empty directory on the same
filesystem as upperdir. So I have changed my initramfs to include that
parameter and have also created my /dir directory (named /.work, owned
by root:root and 0755 mode) on all my individual upperdir filesystems
for all of my XEN domUs.

Now when I start the new kernel 3.15.5 with the modified init script
from the newly created initramfs, I am ending up in a rescue shell.
Both the upper and lower filesystem are (as expected) mounted
appropriately to /mnt/root_ro and /mnt/root_rw amd /mnt/root exists.
Howeverm, trying to combine those two filesystems on /mnt/root (as
before and regardless of whether used with or without the workdir=
parameter) fails with an error message as follows:

# mount -t overlayfs overlayfs -o
lowerdir=/mnt/root_ro,upperdir=/mnt/root_rw,workdir=/.work /mnt/root
mount: mounting overlayfs on /mnt/root failed: Invalid argument

The error message stays the same regardless of where on the command
line the overlayfs "device" parameter appears. I can't see what's
wrong with the command line given that - with the exception of the
workdir=/.work part - the command has not changed from 3.13.10
(overlayfs.v21), therefore currently leaving me at loss.

I would very much appreciate any help and support in tracking down
this unexpected issue.

Regards Atom2
Klaus, I have run into similar problems...
What works for me:
Once you mount the upperdir /mnt/root_rw, create /mnt/root_rw/root and
/mnt/root_rw/workdir and use these for overlayfs mountpoints.

Woody
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