[lxc-devel] lxc-clone do not work when overlayfs.v22 or higher is used

[Serge Hallyn]

Quoting KATOH Yasufumi (karma at jazz.email.ne.jp):
> Hi,
> 
> Now, lxc-clone with overlayfs (lxc-clone -s -B overlayfs) runs internally:
>   mount -t overlayfs -oupperdir=${upper},lowerdir=${lower} lower dest
> 
> But, overlayfs.v22(kernel 3.15) or higher need the option "workdir=",
> so lxc-clone do not work.
> 
> On 3.17 with overlayfs.v24, without workdir option:
>   # mount -n -t overlayfs -o lowerdir=1,upperdir=2 overlayfs 3
>   mount: wrong fs type, bad option, bad superblock on overlayfs,
>          missing codepage or helper program, or other error
> 
>          In some cases useful info is found in syslog - try
>          dmesg | tail or so.
>   # dmesg | tail
>   [  683.456473] overlayfs: missing upperdir or lowerdir or workdir
> 
> On 3.17 with overlayfs.v24, with workdir option:
>   # mount -n -t overlayfs -o lowerdir=1,upperdir=2,workdir=3 overlayfs 4
>   # cat /proc/mounts | grep overlayfs
>   overlayfs /root/overlayfs/4 overlayfs rw,relatime,lowerdir=1,upperdir=2,workdir=3 0 0
> 
> See
>   https://git.kernel.org/cgit/linux/kernel/git/mszeredi/vfs.git/tree/Documentation/filesystems/overlayfs.txt?h=overlayfs.v24

The older version (which is still in use in the 3.16 kernel in Ubuntu 14.10)
fails with that option, so it looks like there's not much to do but try
the workdir=, then if that fails try without workdir=.

Can you send a patch to do that?