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

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

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.