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    SubjectRe: [RFC][PATCH 0/7] Clone PTS namespace
    On Wed, 2008-04-09 at 20:59 -0500, Serge E. Hallyn wrote:

    > Feh, so of course sysfs would have the most interactions for a device
    > namespace, but now we have pty, network, and user namespace all needing
    > some sort of sysfs solution. For a quickfix for
    > CONFIG_USER_SCHED+CONFIG_USER_NS, I just moved /sys/kernel/uids/<uid>
    > to /sys/kernel/uids/<userns_address>/<uid>. But what would be a *good*
    > general solution?
    > ln -s /sys /proc/self/sys?


    In /proc I prefer the /proc/self approach because we can do it and it is
    just much easier to setup and use. (Plus we have weird problems if we
    try and capture more then the pid namespace).

    For other filesystems the only really viable option is to capture
    namespaces at mount time, as we are doing for devpts and proc with
    respect to the pid namespace.

    For the network namespace where it is very much more then a single
    directory with symlinks from physical devices pointing at logical
    network interfaces.

    My last effort in that area was ok'd by Tejun lightly tested by a few
    others and misplaced by gregkh so I don't think we have a real problem
    with resurrecting those patches cleaning them up a bit and merging them.

    The biggest gotcha with sysfs is that the VFS locking for the dcache
    is in the wrong order for distributed filesystems, where we would like
    to make the change atomically on the server and them make the change in
    the local cache. Or in this case the sysfs internal data structures.
    The truly nasty case is supporting rename (as sysfs does) as the VFS
    is not at all happy if you just punt and shoot down the dentries and
    instantiate new ones.

    I'm hoping to be able to get back at this in the week or so as things
    settle down from my move. My last patches should be in my proof of
    concept network namespace tree, if they don't show up elsewhere.

    It isn't my perception that we have a design problem rather, we just
    need to move an important piece of code in a subtle and moderately
    uninteresting direction for it's primary maintainer.

    Further what I did for the network namespace should easily handle the
    uid/gid namespace and should be a good starting place for a general
    device namespace.


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