[PATCH][RFC] Cleanup in namespaces unsharing

[Pavel Emelianov]

Cedric Le Goater wrote:
> Pavel Emelianov wrote:
>> Currently we have two funtions to copy the namespaces:
>> copy_namespaces() and unshare_nsproxy_namespaces(). The
>> second one checks for unsupported functionality with
>>
>> #ifndef CONFIG_IPC_NS
>> 	if (unshare_flags & CLONE_NEWIPC)
>> 		return -EINVAL;
>> #endif
>>
>> -like constructions, while the first one does not. One
>> of the side effects of this is that clone() with the
>> CLONE_NEWXXX set will return 0 if the kernel doesn't
>> support XXX namespaces thus confusing the user-level.
>>
>> The proposal is to make these calls clean from the ifdefs
>> and move these checks into each namespaces' stubs. This
>> will make the code cleaner and (!) return -EINVAL from 
>> fork() in case the desired namespaces are not supported.
>>
>> Did I miss something in the design or this patch worth merging?
> 
> I've sent a more brutal patch in the past removing CONFIG_IPC_NS
> and CONFIG_UTS_NS. Might be a better idea ? 

In case namespaces do not produce performance loss - yes.

By that patch I also wanted to note that we'd better make
all the other namespaces check for flags themselves, not
putting this in the generic code.

> Let me refresh it and resend.
> 
> C.
>