[PATCH 2/2 v3] drm/exynos: added userptr feature.

[KOSAKI Motohiro]

>>> let's assume that one application want to allocate user space memory
>>> region using malloc() and then write something on the region. as you
>>> may know, user space buffer doen't have real physical pages once
>>> malloc() call so if user tries to access the region then page fault
>>> handler would be triggered
>>
>>
>> Understood.
>>
>>> and then in turn next process like swap in to fill physical frame number
>> into entry of the page faulted.
>>
>>
>> Sorry, I can't understand your point due to my poor English.
>> Could you rewrite it easiliy? :)
>>
>
> Simply saying, handle_mm_fault would be called to update pte after finding
> vma and checking access right. and as you know, there are many cases to
> process page fault such as COW or demand paging.

Hmm. If I understand correctly, you guys misunderstand mlock. it doesn't page pinning
nor prevent pfn change. It only guarantee to don't make swap out. e.g. memory campaction
feature may automatically change page physical address.