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    SubjectRE: [PATCH] /proc/pid/status: show all sets of pid according to ns
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    Hi Vasily,

    > -----Original Message-----
    > From: Vasily Kulikov [mailto:segooon@gmail.com]
    > Sent: Tuesday, May 27, 2014 2:05 AM
    > To: Chen, Hanxiao/陈 晗霄
    > Cc: containers@lists.linux-foundation.org; linux-kernel@vger.kernel.org; Serge
    > Hallyn; Oleg Nesterov; David Howells; Eric W. Biederman; Andrew Morton; Al Viro
    > Subject: Re: [PATCH] /proc/pid/status: show all sets of pid according to ns
    >
    > Hi Chen,
    >
    > On Mon, May 26, 2014 at 18:05 +0800, Chen Hanxiao wrote:
    > > We need a direct method of getting the pid inside containers.
    > > If some issues occurred inside a container guest, host user
    > > could not know which process is in trouble just by guest pid:
    > > the users of container guest only knew the pid inside containers.
    > > This will bring obstacle for trouble shooting.
    > >
    > > This patch expands fields of Tgid and Pid:
    > > a) In init_pid_ns, nothing changed;
    > >
    > > b) In one pidns, they will tell the pid inside containers:
    > > Tgid: 1628 9 3
    > > Pid: 1628 9 3
    > > ** process id is 1628 in level 0, 9 in level 1, 3 in level 2.
    >
    > 1. It breaks ABI. Any application which does something like "grep pid: | cut -d:
    > -f2"
    > is now broken by the patch. Maybe add a new field like 'Pid-ns', 'PidNS',
    > or 'Pids' and leave the old one for compatibility?
    >

    Thanks for your comments.
    Adding a new field could solve backward compatibility issue.

    > 2. Is it OK to show internal pids to unprivileged processes? I cannot
    > see anything obviously dangerous with it, though.
    >

    I thinks just 'showing' them would not bring some troubles.

    > > c) If pidns is nested, it depends on which pidns are you in.
    > > Tgid: 9 3
    > > Pid: 9 3
    > > ** Views from level 1 for Pid 1628 in host.
    >
    > --
    > Vasily

    Thanks,
    - Chen
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