Re: Does get_user_pages_fast lock the user pages in memory in my case?

[Huang Shijie <shijie8@gmail.com>]

KOSAKI Motohiro a??e??:
>> In the V4L2_MEMORY_USERPTR method, what I want to do is pin the 
>> anonymous pages in memory.
>>
>> I used to add the VM_LOCKED to vma associated with the pages.In my 
>> opinion, the pages will:
>> LRU_ACTIVE_ANON ---> LRU_INACTIVE_ANON---> LRU_UNEVICTABLE
>>
>> so the pages are pinned in memory.It was ugly, but it works I think.
>> Do you have any suggestions about this method?
>>     
>
> page migration (e.g. move_pages) ignore MLOCK.
> maybe, VM_LOCKED + gut()ed solved it partially :)
>
>   
My old codes used the get_user_pages()/VM_LOCKED just as you said.

I will read the  migration  code, I am not clear about why the gup() can 
stop the migraion.

> but, user process still can call munlock. it cause disaster.
> I still think -EINVAL is better.
>
>
>   
Why the user process call munlock? VLC or Mplayer do not call it, so I 
don't worry about that.

Our video card is still not on sale.So I can wait until the bug is fixed. :)
If there is no method to bypass the problem in future,I will return -EINVAL.

thanks
>
>   

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