On Mon, Nov 3, 2014 at 4:17 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
> On Mon, Nov 3, 2014 at 4:12 PM, Aditya Kali <adityakali@xxxxxxxxxx> wrote:
>> On Mon, Nov 3, 2014 at 3:48 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
>>> On Mon, Nov 3, 2014 at 3:23 PM, Aditya Kali <adityakali@xxxxxxxxxx> wrote:
>>>> On Mon, Nov 3, 2014 at 3:15 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
>>>>> On Mon, Nov 3, 2014 at 3:12 PM, Aditya Kali <adityakali@xxxxxxxxxx> wrote:
>>>>>> On Fri, Oct 31, 2014 at 5:07 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
>>>>>>> On Fri, Oct 31, 2014 at 12:19 PM, Aditya Kali <adityakali@xxxxxxxxxx> wrote:
>>>>>>>> if (opts->flags & CGRP_ROOT_SANE_BEHAVIOR) {
>>>>>>>> pr_warn("sane_behavior: this is still under development and its behaviors will change, proceed at your own risk\n");
>>>>>>>> - if (nr_opts != 1) {
>>>>>>>> + if (nr_opts > 1) {
>>>>>>>> pr_err("sane_behavior: no other mount options allowed\n");
>>>>>>>> return -EINVAL;
>>>>>>>
>>>>>>> This looks wrong. But, if you make the change above, then it'll be right.
>>>>>>>
>>>>>>
>>>>>> It would have been nice if simple 'mount -t cgroup cgroup <mnt>' from
>>>>>> cgroupns does the right thing automatically.
>>>>>>
>>>>>
>>>>> This is a debatable point, but it's not what I meant. Won't your code
>>>>> let 'mount -t cgroup -o one_evil_flag cgroup mountpoint' through?
>>>>>
>>>>
>>>> I don't think so. This check "if (nr_opts > 1)" is nested under "if
>>>> (opts->flags & CGRP_ROOT_SANE_BEHAVIOR)". So we know that there is
>>>> atleast 1 option ('__DEVEL__sane_behavior') present (implicit or not).
>>>> Addition of 'one_evil_flag' will make nr_opts = 2 and result in EINVAL
>>>> here.
>>>
>>> But the implicit __DEVEL__sane_behavior doesn't increment nr_opts, right?
>>>
>>
>> Yes. Hence this change makes sure that we don't return EINVAL when
>> nr_opts == 0 or nr_opts == 1 :)
>> That way, both of the following are equivalent when inside non-init cgroupns:
>>
>> (1) $ mount -t cgroup -o __DEVEL__sane_behavior cgroup mountpoint
>> (2) $ mount -t cgroup cgroup mountpoint
>>
>> Any other mount option will trigger the error here.
>
> I still don't get it. Can you walk me through why mount -o
> some_other_option -t cgroup cgroup mountpoint causes -EINVAL?
>
Argh! You are right. I was totally convinced that this works. But it
clearly doesn't if you specify 1 legit mount option. I wanted to make
it work for both cases (1) and (2) above. But then this check will
have to be changed :(
Sorry about the back and forth. I am just going to make it return
EINVAL if __DEVEL_sane_behavior is not specified as suggested in the
beginning.
> --Andy
--
Aditya
--
To unsubscribe from this list: send the line "unsubscribe linux-api" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
