RE: [RESEND][PATCH 0/2v5] ns, procfs: pid conversion between ns and showing pidns hierarchy

[Chen, Hanxiao]

> -----Original Message-----
> From: containers-bounces@xxxxxxxxxxxxxxxxxxxxxxxxxx
> [mailto:containers-bounces@xxxxxxxxxxxxxxxxxxxxxxxxxx] On Behalf Of Chen
> Hanxiao
> Sent: Friday, October 24, 2014 6:16 PM
> To: containers@xxxxxxxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Cc: Richard Weinberger; Serge Hallyn; Oleg Nesterov; Mateusz Guzik; David Howells;
> Eric W. Biederman
> Subject: [RESEND][PATCH 0/2v5] ns, procfs: pid conversion between ns and showing
> pidns hierarchy
> 
> This series will expose pid inside containers
> via procfs.
> Also show the hierarchy of pid namespcae.
> Then we could know how pid looks inside a container
> and their ns relationships.
> 
> 1. helpful for nested container check/restore
> From /proc/PID/ns/pid, we could know whether two pid lived
> in the same ns.
> From this patch, we could know whether two pid had relationship
> between each other.
> 
> 2. used for pid translation from container
> Ex:
>      init_pid_ns    ns1         ns2
>  t1  2
>  t2   `- 3          1
>  t3   `- 4          3
>  t4       `- 5      `- 5        1
>  t5       `- 6      `- 8        3
> 
> It could solve problems like: we see a pid 3 goes wrong
> in container's log, what is its pid on hosts:
> a) inside container:
> # readlink /proc/3/ns/pid
> pid:[4026532388]
> 
> b) on host:
> # cat /proc/pidns_hierarchy
> 14918 16263
> 16581
> Then we could easily find /proc/16263/ns/pid->4026532388.
> On host, we knew that reported pid 3 is in level 2,
>    and its parental pid ns is from pid 14918.
> 
> c) on host, check child of 16263, grep it from status:
> NSpid:  16268   8       3
> 
> We knew that pid 16268 is pid 3 reported by container.
> 

Hi,

Any comments?

Thanks,
- Chen