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

[Huang Shijie <shijie8@gmail.com>]

 
>> I read the kernel code again. In my case ,the kernel will pin the pages 
>> in memory.
>> I missed function is_page_cache_freeable() in the pageout().
>>
>> In my case, is_page_cache_freeable()will return false ,for 
>> page_count(page) is 3 now:
>> <1> one is from alloc_page_* in page fault.
>> <2> one is from get_usr_pages()
>> <3> one is from add_to_swap() in shrink_page_list()
>>     
>
> One more, try_to_unmap will call page_cache_release. 
> So, count is 2. 
>
>   
I found I missed something.When code reachs is_page_cache_freeable(). 
page_count(page) is 3:

<1> alloc_page_* in page fault . [page count is 1]
<2> get_usr_pages().             [page count is 2]
<3> isolate_pages_global()	 [page count is 3]
<4> add_to_swap()                [page count is 4]
<5> try_to_unmap()               [page count is 3]

so it not a bug, just a vicious circle.

Do i miss something?
 

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