Re: [PATCH] Fast status update interface (/selinux/status)

[Eric Paris <eparis@parisplace.org>]

On Fri, Aug 27, 2010 at 11:48 AM, Eric Paris <eparis@parisplace.org> wrote:
> 2010/8/27 KaiGai Kohei <kaigai@ak.jp.nec.com>:
>> I revised the /selinux/status implementation.
>>
>> * It becomes to report 'deny_unknown'. Userspace object manager
>>  also reference this flag to decide its behavior when the loaded
>>  policy does not support expected object classes.
>> * It provided PAGE_READONLY to remap_pfn_range() as page protection
>>  flag independent from argument of mmap(2), but it was uncommon.
>>  I fixed to pass vma->vm_page_prot instead of the hardwired flag
>>  according to any other implementation style.
>>  Now it returns an error, if user tries to map /selinux/status as
>>  writable pages.
>
> I really hate blowing 4k of memory on every system to show 40 bytes of
> data on just a few systems.  Is there any change we could allocate the
> page the first time it is needed rather that at boot?  I know compared
> to the size of policy and other memory usage in SELinux it's odd for
> me to complain, but I've decided to get on a reduction if possible
> kick.
>
> Only other comment is that __initcall() is deprecated and we are
> supposed to use device_initcall() now.
>
> If you plan to use it, I'll ack if you change both of those things....

actually if you move to dynamic allocation of the status page and use
static DEFINE_SPINLOCK instead of static spinlock_t you can get rid of
the __init() code altogether....

-Eric


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