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

[Jiri Pirko <jiri@resnulli.us>]

Tue, Jul 14, 2026 at 04:28:01AM +0200, cui.tao@linux.dev wrote:
>
>
>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.

Exposing this from ib side is not doable, as IB may be compiled as a
module. So what I do is I intrododuce "static bool rdmacg_netns_shared"
in cgroup/rdma.c and exported function rdmacg_set_netns_shared() to set
it from IB.


>
>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
>> 
>> 
>> 
>