Can not remove the subdirectory in cgroup pseudo-filesystem

Can not remove the subdirectory in cgroup pseudo-filesystem

[anqin]

Dear all,

I have met a straight problem in my recent operation.
Previously, I can do the following operations:

# mount -t cgroup cgroup /mnt/cgrp
# cd /mnt/cgrp
# mkdir test
# echo $$ > test/tasks
# rm  -rf test

but now I met the straight permission with the same
operation while I am root:

# mount -t cgroup cgroup /mnt/cgrp
# cd /mnt/cgrp
# mkdir test
# echo $$ > test/tasks
-bash: echo: write error: No space left on device
# rm  -rf test
rm: cannot remove `/mnt/cgrp/test/cpuset.memory_spread_slab':
Operation not permitted
rm: cannot remove `/mnt/cgrp/test/cpuset.memory_spread_page':
Operation not permitted
rm: cannot remove `/mnt/cgrp/test/cpuset.memory_pressure': Operation
not permitted
...

I guess maybe the permission attributes block my operation, but I
checked with lsattr
and got the following message:

# lsattr /mnt/cgrp/test
lsattr: Inappropriate ioctl for device While reading flags on
/mnt/cgrp/test/cpuset.memory_spread_slab
lsattr: Inappropriate ioctl for device While reading flags on
/mnt/cgrp/test/cpuset.memory_spread_page
lsattr: Inappropriate ioctl for device While reading flags on
/mnt/cgrp/test/cpuset.memory_pressure
...

I have no idea how to fix it. Any help?

Thank you very much,

Anqin

Re: Can not remove the subdirectory in cgroup pseudo-filesystem

[Serge E. Hallyn]

Quoting anqin (anqin.qin-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org):
> Dear all,
> 
> I have met a straight problem in my recent operation.
> Previously, I can do the following operations:
> 
> # mount -t cgroup cgroup /mnt/cgrp
> # cd /mnt/cgrp
> # mkdir test
> # echo $$ > test/tasks
> # rm  -rf test

I doubt this ever worked - rather, you have to do
	rmdir test

rm -rf will try to delete the files under test/ first,
and fail.

> 
> but now I met the straight permission with the same
> operation while I am root:
> 
> # mount -t cgroup cgroup /mnt/cgrp
> # cd /mnt/cgrp
> # mkdir test
> # echo $$ > test/tasks

Yes you have to initialize some cpuset files first.  Otherwise
the tasks have no access to any memory or cpus.

echo 0 > /cgroup/1/cpuset.mems
echo 0-3 > /cgroup/1/cpuset.cpus
echo $$ > /cgroup/1//tasks
	(success)

> -bash: echo: write error: No space left on device
> # rm  -rf test
> rm: cannot remove `/mnt/cgrp/test/cpuset.memory_spread_slab':
> Operation not permitted
> rm: cannot remove `/mnt/cgrp/test/cpuset.memory_spread_page':
> Operation not permitted
> rm: cannot remove `/mnt/cgrp/test/cpuset.memory_pressure': Operation
> not permitted
> ...
> 
> I guess maybe the permission attributes block my operation, but I
> checked with lsattr
> and got the following message:
> 
> # lsattr /mnt/cgrp/test
> lsattr: Inappropriate ioctl for device While reading flags on
> /mnt/cgrp/test/cpuset.memory_spread_slab
> lsattr: Inappropriate ioctl for device While reading flags on
> /mnt/cgrp/test/cpuset.memory_spread_page
> lsattr: Inappropriate ioctl for device While reading flags on
> /mnt/cgrp/test/cpuset.memory_pressure
> ...
> 
> I have no idea how to fix it. Any help?
> 
> Thank you very much,
> 
> Anqin
> _______________________________________________
> Containers mailing list
> Containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
> https://lists.linux-foundation.org/mailman/listinfo/containers

Re: Can not remove the subdirectory in cgroup pseudo-filesystem

[anqin]

>
> Yes you have to initialize some cpuset files first.  Otherwise
> the tasks have no access to any memory or cpus.
>

Oh... thank you for reminding. Previously, I run my tests in
a experimental kernel, it seems someone has set the
parameters.


BTW, is it possible currently to combine two tasks into
one cgroup? for instance, I have run two bashes (bash_A and
bash_B). Now, in bash_A, I created a cgroup in procfs:

# mount -t cgroup cgroup /mnt/cgrp
# cd /mnt/cgrp
# mkdir test
# echo $$ > test/tasks

Then, I would like to add bash_B in this task group but
fail:

# echo #(PID_OF_bash_B) >  test/tasks
-bash: echo: write error: Operation not permitted

It seems the cgroup can not couple two irrelevant
task together, right?


Best,

Anqin

Re: Can not remove the subdirectory in cgroup pseudo-filesystem

[Li Zefan]

anqin wrote:
>> Yes you have to initialize some cpuset files first.  Otherwise
>> the tasks have no access to any memory or cpus.
>>
> 
> Oh... thank you for reminding. Previously, I run my tests in
> a experimental kernel, it seems someone has set the
> parameters.
> 
> 
> BTW, is it possible currently to combine two tasks into
> one cgroup? for instance, I have run two bashes (bash_A and

I recomend you to read Documentation/cgroups/cgroups.txt to know
cgroup better. Cgroup is used to aggregate/partition sets of tasks,
so of course you can put more than 1 task into a cgroup.

> bash_B). Now, in bash_A, I created a cgroup in procfs:
> 
> # mount -t cgroup cgroup /mnt/cgrp

mount cgroupfs with all cgroup subsystems is not so sane IMO.

> # cd /mnt/cgrp
> # mkdir test
> # echo $$ > test/tasks
> 
> Then, I would like to add bash_B in this task group but
> fail:
> 
> # echo #(PID_OF_bash_B) >  test/tasks
> -bash: echo: write error: Operation not permitted
> 

That's because ns_cgroup is binded in this cgroup hierarchy, and
it's ns_cgroup that prevents the task attaching, but a patch in
-mm tree relaxes this check, and you won't see this restriction
when using ns_cgroup.

> It seems the cgroup can not couple two irrelevant
> task together, right?
> 
> 
> Best,
> 
> Anqin

Re: Can not remove the subdirectory in cgroup pseudo-filesystem

[Serge E. Hallyn]

Quoting Li Zefan (lizf-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org):
> anqin wrote:
> >> Yes you have to initialize some cpuset files first.  Otherwise
> >> the tasks have no access to any memory or cpus.
> >>
> > 
> > Oh... thank you for reminding. Previously, I run my tests in
> > a experimental kernel, it seems someone has set the
> > parameters.
> > 
> > 
> > BTW, is it possible currently to combine two tasks into
> > one cgroup? for instance, I have run two bashes (bash_A and
> 
> I recomend you to read Documentation/cgroups/cgroups.txt to know
> cgroup better. Cgroup is used to aggregate/partition sets of tasks,
> so of course you can put more than 1 task into a cgroup.
> 
> > bash_B). Now, in bash_A, I created a cgroup in procfs:
> > 
> > # mount -t cgroup cgroup /mnt/cgrp
> 
> mount cgroupfs with all cgroup subsystems is not so sane IMO.
> 
> > # cd /mnt/cgrp
> > # mkdir test
> > # echo $$ > test/tasks
> > 
> > Then, I would like to add bash_B in this task group but
> > fail:
> > 
> > # echo #(PID_OF_bash_B) >  test/tasks
> > -bash: echo: write error: Operation not permitted
> > 
> 
> That's because ns_cgroup is binded in this cgroup hierarchy, and
> it's ns_cgroup that prevents the task attaching, but a patch in
> -mm tree relaxes this check, and you won't see this restriction
> when using ns_cgroup.

Ooh, right, you can only enter an empty cgroup in "older" kernels...

In my defense, that made sense when the ns cgroup was still possibly
going to be used for allowing tasks to enter each other's namespaces. :)

-serge

> > It seems the cgroup can not couple two irrelevant
> > task together, right?
> > 
> > 
> > Best,
> > 
> > Anqin

Re: Can not remove the subdirectory in cgroup pseudo-filesystem

[anqin]

Thank you,

when I mount all cgroup subsystem to cgroupfs, it mounts also
the ns_cgroup which blocks the adding new taskes into given
cgroup.

If I mount a single subsystem (such as a memory), it can work.


>> # mount -t cgroup cgroup /mnt/cgrp
>
> mount cgroupfs with all cgroup subsystems is not so sane IMO.
>
>> # cd /mnt/cgrp
>> # mkdir test
>> # echo $$ > test/tasks
>>
>> Then, I would like to add bash_B in this task group but
>> fail:
>>
>> # echo #(PID_OF_bash_B) >  test/tasks
>> -bash: echo: write error: Operation not permitted
>>
>
> That's because ns_cgroup is binded in this cgroup hierarchy, and
> it's ns_cgroup that prevents the task attaching, but a patch in
> -mm tree relaxes this check, and you won't see this restriction
> when using ns_cgroup.
>