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    SubjectRe: [patch -mm 0/4] mqueue namespace
    Quoting Eric W. Biederman (ebiederm@xmission.com):
    > ebiederm@xmission.com (Eric W. Biederman) writes:
    >
    > > One way to fix that is to add a hidden directory to the mnt namespace.
    > > Where magic in kernel filesystems can be mounted. Only visible
    > > with a magic openat flag. Then:
    > >
    > > fd = openat(AT_FDKERN, ".", O_DIRECTORY)
    > > fchdir(fd);
    > > umount("./mqueue", MNT_DETACH);
    > > mount(("none", "./mqueue", "mqueue", 0, NULL);
    > >
    > > Would unshare the mqueue namespace.
    > >
    > > Implemented for plan9 this would solve a problem of how do you get
    > > access to all of it's special filesystems. As only bind mounts
    > > and remote filesystem mounts are available. For linux thinking about
    > > it might shake the conversation up a bit.
    >
    > Thinking about this some more. What is especially attractive if we do
    > all namespaces this way is that it solves two lurking problems.
    > 1) How do you keep a namespace around without a process in it.
    > 2) How do you enter a container.
    >
    > If we could land the namespaces in the filesystem we could easily
    > persist them past the point where a process is present in one if we so
    > choose.
    >
    > Entering a container would be a matter of replacing your current
    > namespaces mounts with namespace mounts take from the filesystem.
    >
    > I expect performance would degrade in practice, but it is tempting
    > to implement it and run a benchmark and see if we can measure anything.

    The device ns could be a mount of an fs with the devices created in it,
    while mknod becomes a symlink from that fs. And once a network
    namespace is a filesystem, we can aim for the plan9 NAT solution of
    mounting a remote /net onto ours. Neat.

    But bye-bye posix?

    -serge


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