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    SubjectRe: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup
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    On April 11, 2016 5:10:47 PM PDT, ebiederm@xmission.com wrote:
    >Linus Torvalds <torvalds@linux-foundation.org> writes:
    >
    >> On Mon, Apr 11, 2016 at 4:37 PM, Eric W. Biederman
    >> <ebiederm@xmission.com> wrote:
    >>>
    >>> My practical concern if we worked through the implementation details
    >>> would be how would it interact with people who bind mount
    >/dev/pts/ptmx
    >>> on top of /dev/ptmx. We might get some strange new errors.
    >>
    >> Yes, please don't let's play "clever" games. The semantics should be
    >> fairly straightforward.
    >
    >Actually for me this is about keeping the semantics simpler, and coming
    >up with a higher performance implementation.
    >
    >A dentry that does an automount is already well defined.
    >
    >Making the rule that accessing /dev/ptmx causes an automount of
    >/dev/pts/ptmx on top of the device node at /dev/ptmx is really simple,
    >with no special games. It also makes it more obvious to userspace what
    >is going on. AKA allows userspace to know which superblock does an
    >open
    >ptmx master tty belongs to (and it happens in a backwards and forwards
    >compatible way).
    >
    >My only concern is with this very minor change in semantics will
    >anything care. I need to implement and test to find out.
    >
    >I think I see an implementation that Al won't grumble too loudly about.
    >
    >Anyway I am going to try this and see what I can see.
    >
    >Eric

    Why bother with an automount? You can look up ../ptmx from the devpts get_super method and just do the bind mount once. No fuss, no muss. What's wrong with that?
    --
    Sent from my Android device with K-9 Mail. Please excuse brevity and formatting.

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