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    SubjectRe: [PATCH 2/7] proc: Implement support for automounts in task directories
    On Thu, 06 Nov 2008 19:51:23 -0800 (Eric W. Biederman) wrote:

    > If we could do all of this with reference counting so that the
    > mount would persist exactly until the last user of it has gone
    > away without a periodic poll I would love it. But the infrastructure
    > doesn't support that today,

    Well that sucks. The free-on-last-put idiom occurs in so many places
    and serves us so well. I wonder what went wrong here?

    I guess it has interactions with dentry and inode cache aging which
    could get tricky.

    > and where this is at least partially
    > a bug fix I would rather not have the change depend on enhancing
    > the VFS.
    > The algorithm is actually very aggressive and in practice you don't
    > see any /proc/<pid>/net showing up as a mount point.

    Do you think it has failure modes? Most particularly: obscure usage
    patterns which can cause memory exhaustion?

    > > Obviously, that becomes clearer as one spends more time with the code,
    > > but I wonder whether this has all been made as maintainble as it
    > > possibly could be.
    > Good question.
    > In the sense of will we have to go through and futz with the code all
    > of the time. The abstraction seems good. You put a mount on
    > the proc_automounts list with do_add_mounts and it goes away eventually
    > with all of the vfs rules maintained.
    > In the sense of can the code be read? Perhaps it could be better.
    > I expect it helps to have run the code and see /proc/net as a filesystem.
    > that is magically mounted.

    'twould be a useful contribution if you were to enshrine your
    discoveries in /*these things*/. You knew I was working up to that :)

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