[CRIU] [PATCH v2 resent 1/4] ipc/sysctl: c/r fs.mqueue.msg_default fs.mqueue.msgsize_default

[Pavel Tikhomirov]

On 07/14/2016 01:52 PM, Pavel Emelyanov wrote:
> On 07/13/2016 05:12 PM, Pavel Tikhomirov wrote:
>>
>>
>> On 07/13/2016 03:58 PM, Pavel Tikhomirov wrote:
>>>
>>>
>>> On 07/13/2016 03:52 PM, Pavel Emelyanov wrote:
>>>> On 07/04/2016 10:47 AM, Pavel Tikhomirov wrote:
>>>>> we already have 3/5 fs.mqueue.xxx sysctls so why not have all:
>>>>>
>>>>> /proc/sys/fs/mqueue/msg_default is  a read/write  file for
>>>>> setting/getting the default number of messages in a queue value
>>>>> if attr parameter of mq_open(2) is NULL. If it exceed msg_max,
>>>>> the default value is initialized msg_max.
>>>>>
>>>>> /proc/sys/fs/mqueue/msgsize_default is a read/write file for
>>>>> setting/getting the default message size value if attr parameter
>>>>> of mq_open(2) is NULL. If it exceed msgsize_max, the default
>>>>> value is initialized msgsize_max.
>>>>>
>>>>> *We have these sysctls writable in VZ7 CT.
>>>>
>>>> What about upstream kernel? Are these writable for it as well? If yes,
>>>> how
>>>> has it happened that vzkernel DIDN'T have them as such at some point?
>>>
>>
>> Sorry, I though it was about net sysctls but that is about ipc...
>>
>> So, for ipc sysctls:
>>
>> Sysctls are writable in sub-ipcns:
>> # unshare -ri
>> # cat /proc/sys/fs/mqueue/msgsize_default
>> 8192
>> # echo 16384 > /proc/sys/fs/mqueue/msgsize_default
>> # cat /proc/sys/fs/mqueue/msgsize_default
>> 16384
>>
>> Sysctls msg(size)_default become writable in vzkernel in commit:
>
> No no no, my question was different. They are read-write in vanilla kernel, but
> have been read-only for some time in vzkenrel. So when and why have they become
> read-only in vzkernel?

See vzkernel commit 44b7b87ec555 ("VE/SYSCTL: write permission 
restriction") and commit ad336c529a36 ("VE: use ve environtment for 
sysctl restrictions") here we add readonly restriction for inCT sysctls 
on sysctl_table_root, we had almost the same in VZ6.

>
>> commit 42faae2077ff33775d612b0d4f17aedc000e0a37
>> Author: Andrew Vagin <avagin at openvz.org>
>> Date:   Thu Dec 19 13:28:27 2013 +0400
>>
>>      ve/sysctl: allow to change mqueue sysctl-s
>>
>>      All mqueue data are accounted into the kmem ubc.
>>      These sysctl belong to ipcns, so all changes doesn't affect other
>> containers.
>>
>>      https://jira.sw.ru/browse/PSBM-20102
>>
>>      Signed-off-by: Andrew Vagin <avagin at openvz.org>
>>      Acked-by: Cyrill Gorcunov <gorcunov at openvz.org>
>>
>

-- 
Best regards, Tikhomirov Pavel
Software Developer, Virtuozzo.