[libvirt] Intend to add fuse filesystem support for libvirt lxc

[Daniel P. Berrange]

On Fri, Jun 29, 2012 at 11:05:33AM +0800, Gao feng wrote:
> Hi Everyone,
> 
> Now I'm working on making the container's system info(such as /proc/meminfo,cpuinfo..) isolate from
> the host.
> 
> I made a patch which implement showing the /proc/meminfo base on container's memcg,
> and sent it to the community.(http://marc.info/?l=linux-mm&m=133826035821338&w=2)
> 
> but I found it's difficult to be accepted, because this way is ugly,
> and somebody gave me some suggestions.
> 
> the first way is making another kernel file(just like memory.limit_in_bytes),and mount it to the container.
> I don't like this way,because there will be many redundance information between this new kernel file and
> the existing kernel file,some files such as memory.stat already contains memcg information.
> 
> the other way is adding fuse filesystem support for libvirt lxc.
> with this way,
> we can simply collect information from cgroup in fuse_operations.read function,
> and mount this file to the container.
> we can impletment isolate meminfo in userspace without changing kernel codes.
> 
> I have impletment fuse support for libvrit now, and ready to impletement the meminfo isolated.
> 
> I want to know if you have any comment or another ideas?

Having read that long thread you quote above, I tend to agree that
creating a FUSE filesystem is probably the best option we have for
dealing with /proc in the short term.  I'd expect it to be provided
either in the libvirt_lxc  controller process that is forked per
container, or even perhaps in a new process libvirt_lxc_fuse forked
per container.

I can see two ways todo it

  - Provide a FUSE filesystem that just contains the couple of files
    we need, and then bind them over the top of the files in /proc

  - Provide a FUSE filesystem that does a union-fs like layering on
    top of an existing /proc mount, avoiding the need for bind mounts


Daniel
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