[libvirt] [RFC] [PATCH v2 1/6] add configure option --with-fuse for libvirt

[Gao feng]

于 2012年09月05日 20:42, Daniel P. Berrange 写道:
> On Wed, Sep 05, 2012 at 05:41:40PM +0800, Gao feng wrote:
>> Hi Daniel & Glauber
>>
>> 于 2012年07月31日 17:27, Daniel P. Berrange 写道:
>>> Hi Gao,
>>>
>>> I'm wondering if you are planning to attend the Linux Plumbers Conference
>>> in San Diego at the end of August ?  Glauber is going to be giving a talk
>>> on precisely the subject of virtualizing /proc in containers which is
>>> exactly what your patch is looking at
>>>
>>>   https://blueprints.launchpad.net/lpc/+spec/lpc2012-cont-proc
>>>
>>> I'll review your patches now, but I think I'd like to wait to hear what
>>> Glauber talks about at LPC before we try to merge this support in libvirt,
>>> so we have an broadly agreed long term strategy for /proc between all the
>>> interested userspace & kernel guys.
>>
>> I did not attend the LPC,so can you tell me what's the situation of the
>> /proc virtualization?
>>
>> I think maybe we should just apply this patchset first,and wait for somebody
>> sending patches to implement /proc virtualization.
> 
> So there were three main approaches discussed
> 
>  1. FUSE based /proc + a real hidden /.proc. The FUSE /proc provides custom
>     handling of various files like meminfo, otherwise forwards I/O requests
>     through to the hidden /.proc files. This was the original proof of
>     concept.
> 
>  2. One FUSE filesystem for all containers + a real /proc. Bind mount files
>     from the FUSE filesystem into the container's /proc. This is what Glauber
>     has done.
> 
>  3. One FUSE filesystem per container + a real /proc. Bind mount files from
>     the FUSE filesystem into the container's /proc. This is what your patch
>     is doing
> 
> Options 2 & 3 have a clear a win over option 1 in efficiency terms, since
> they avoid doubling the I/O required for the majority of files.
> 
> Glaubar thinks it is perferrable to have a single FUSE filesystem that
> has one sub-directory for each container. Then bind mount the appropriate
> sub dir into each container.
> 
> I kinda like the way you have done things, having a private FUSE filesystem
> per container, for security reasons. By having the FUSE backend be part of
> the libvirt_lxc process we have strictly isolated each containers' environment.
> 
> If we wanted a single shared FUSE for all containers, we'd need to have some
> single shared daemon to maintain it. This could not be libvirtd itself, since
> we need the containers & their filesystems to continue to work when libvirtd
> itself is not running. We could introduce a separate libvirt_fused which
> provided a shared filesystem, but this still has the downside that any
> flaw in its impl could provide a way for one container to attack another
> container

Agree,if we choose the option 2,we have to organize the sub-directory for each
container in fuse,it will make fuse filesystem complicated.

> 
> So in summary, I think your patches which add a private FUSE per container
> in libvirt_lxc appear to be the best option at this time.
> 

Ok,I will rebase this patchset and send the v3 patchset.

Thanks
Gao