Re: [PATCH rdma-next 08/13] RDMA/cgroup: Scope rdma cgroup device visibility to the net namespace

[Tao Cui <cui.tao@linux.dev>]

在 2026/7/13 17:34, Jiri Pirko 写道:
> Thu, Jul 09, 2026 at 03:04:23PM +0200, mkoutny@suse.com wrote:
>> Hi.
>>
>> On Thu, Jul 09, 2026 at 11:55:27AM +0200, Jiri Pirko <jiri@resnulli.us> wrote:
>>> index 993446ab66d0..4523c1884d67 100644
>>> --- a/Documentation/admin-guide/cgroup-v2.rst
>>> +++ b/Documentation/admin-guide/cgroup-v2.rst
>>> @@ -2752,6 +2752,13 @@ RDMA
>>>  The "rdma" controller regulates the distribution and accounting of
>>>  RDMA resources.
>>>  
>>> +When RDMA devices are isolated per network namespace (exclusive mode),
>>> +device names are unique only within a network namespace. The device lines
>>> +below are therefore scoped to the reading or writing process's network
>>> +namespace: only devices accessible from that namespace are listed, and a
>>> +limit is applied to the device of that name in that namespace. Configure
>>> +limits from the same network namespace as the workloads.
>>
>> OK.
>>
>>> --- a/include/linux/cgroup_rdma.h
>>> +++ b/include/linux/cgroup_rdma.h
>>> @@ -7,6 +7,7 @@
>>>  #define _CGROUP_RDMA_H
>>>  
>>>  #include <linux/cgroup.h>
>>> +#include <net/net_namespace.h>
>>>  
>>>  enum rdmacg_resource_type {
>>>  	RDMACG_RESOURCE_HCA_HANDLE,
>>> @@ -34,6 +35,15 @@ struct rdmacg_device {
>>>  	struct list_head	dev_node;
>>>  	struct list_head	rpools;
>>>  	char			*name;
>>> +	/*
>>> +	 * Net namespace the device belongs to. @netns_shared mirrors
>>> +	 * ib_devices_shared_netns: when true the device is visible from every
>>> +	 * net namespace (shared mode); otherwise @net is the only namespace
>>> +	 * that may see and configure it. @netns_shared is updated when the
>>> +	 * sharing mode changes, so use {READ,WRITE}_ONCE() to access it.
>>> +	 */
>>> +	possible_net_t		net;
>>> +	bool			netns_shared;
>>
>> Any reason to store the netns_shared split per device? (IIUC, it's a
>> global parameter.)
> 
> No reason, changed.
> 
Hi Jiri,

A question on the v2 you mentioned to Michal.

Once netns_shared stops being cached per rdmacg_device,
rdmacg_device_visible() in kernel/cgroup/rdma.c still needs the current
sharing mode, whose authoritative value lives in the IB core
(ib_devices_shared_netns). How do you plan to expose it there without
the generic cgroup controller reaching back into drivers/infiniband/?
Exporting the global, or keeping an IB-side update hook, both feel a bit
awkward; it would be good to see which direction you took.

On the mechanism itself: it's the right call that rdmacg_try_charge()
stays out of the scoping. Charging takes the rdmacg_device pointer
directly (no name lookup), and a task can only charge a device it
already holds a handle to, so applying visibility there would be wrong.
The scoping deliberately touches only the name-based lookup (the write
path) and the enumeration (read/show) paths -- worth keeping that
invariant in mind so a later patch doesn't grow the filter.

Thanks,
Tao> Thanks!
> 
>>
>> Thanks,
>> Michal
> 
> 
>