RE: [PATCH v8 1/2] procfs: show hierarchy of pid namespace

[Chen, Hanxiao]

> -----Original Message-----
> From: containers-bounces@xxxxxxxxxxxxxxxxxxxxxxxxxx
> [mailto:containers-bounces@xxxxxxxxxxxxxxxxxxxxxxxxxx] On Behalf Of Chen
> Hanxiao
> Sent: Tuesday, November 18, 2014 5:30 PM
> To: Eric W. Biederman; Serge Hallyn; Oleg Nesterov; Richard Weinberger
> Cc: containers@xxxxxxxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> Mateusz Guzik; David Howells
> Subject: [PATCH v8 1/2] procfs: show hierarchy of pid namespace
> 
> We lack of pid hierarchy information, and this will lead to:
> a) we don't know pids' relationship, who is whose child:
>    /proc/PID/ns/pid only tell us whether two pids live in different ns
> b) bring trouble to nested lxc container check/restore/migration
> c) bring trouble to pid translation between containers;
> 
> This patch will show the hierarchy of pid namespace
> by pidns_hierarchy like:
> 
> <init_PID> <parent_of_init_PID> <relative PID level>
> 
> Ex:
> [root@localhost ~]#cat /proc/pidns_hierarchy
> 18060 1 1
> 18102 18060 2
> 1534  18102 3
> 1600  18102 3
> 1550  1 1
> *Note: numbers represent the pid 1 in different ns
> 
> It shows the pid hierarchy below:
> 
>       init_pid_ns 1
>               â
> ââââââââââââââ
> ns1                      ns2
> â                        â
> 1550                    18060
>                           â
>                           â
>                          ns3
>                           â
>                         18102
>                           â
>                  ââââââââââââ
>                  ns4                   ns5
>                  â                    â
>                 1534                  1600
> 
> Every pid printed in pidns_hierarchy
> is the init pid of that pid ns level.
> 
> Signed-off-by: Chen Hanxiao <chenhanxiao@xxxxxxxxxxxxxx>
> ---
> v8: fix some improper comments
>     use max() from kernel.h
> v7: change stype to be consistent with current interface like
>     <init_PID> <parent_of_init_PID> <relative PID level>
>     remove EXPERT dependent in Kconfig
> v6: fix a get_pid leak and do some cleanups;
> v5: collect pid by find_ge_pid;
>     use local list inside nslist_proc_show;
>     use get_pid, remove mutex lock.
> v4: simplify pid collection and some performance optimizamtion
>     fix another race issue.
> v3: fix a race issue and memory leak issue
> v2: use a procfs text file instead of dirs under /proc
> 

Hi,

Any comments?

Thanks,
- Chen