[Devel] Re: [PATCH 2/4] sysfs: Implement sysfs manged shadow directory support.

[Tejun Heo]

Hello,

Eric W. Biederman wrote:
> How close are we to the point where we can get mount sysfs multiple
> times and get multiple dentry trees with different super blocks?

Yeah, that sounds much better.  We only have to pay attention to getting
sysfs_dirent tree correct.  The rest can be done by just looking up the
correct sysfs_dirent in sysfs_lookup().  We would still need to pin all
shadows to keep sysfs_get_dentry() working.

> That really does sound like the right way to go.  Especially as it
> simplifies the monitoring of containers.  If you want to watch what
> the view looks like in some container your bind mount his sysfs and
> look at that.
> 
> If we can do that the dcache side at least will be beautiful.  And
> with a little care we may be able to reduce the work to a special case
> in lookup, some extra handling to mark directories as belonging only
> to a certain mount of sysfs.
> 
> If we can find something that is stupid and simple I'm all for that.

Amen.

> To reach the no-kobj utopia we may also need a special device_migrate
> that is a super set of device_rename (because sometimes we need to
> rename devices when we move them between namespaces).

One thing I'm curious about is which semantic is appropriate behavior
when a node is migrated from one namespace to another - renaming or
deactivation followed by activation in new name space.  I guess it
doesn't really matter.

> So are we close to having a sysfs that we can have multiple super
> blocks for?

Sorry but I dunno.  It sounds much more appealing than other approaches tho.

-- 
tejun
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