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

[KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>]

> > I can't understand your point exactly yet.
> > But what I mean is following as in user mode
> >
> > posix_memalignq(&buffer);
> > mlock(buffer,  buffer_len); 
> >
> >   
> I also wish the VLC use  the mlock,but it does not.If it uses mlock(),
> the pages will be put in LRU_UNEVICETABL LIST.
> 
> Maybe the programmer of VLC thinks: Why i add mlock, for the kernel has the
> gup() which could pin the pages in memory?

more weakness.

mlock() only gurantee the address range is memory-resident, not gurantee to no change 
virtual-physical mappings.

There are different operation.

example, gup() prevent page migration but mlock doesn't.


> > I will not dirty your driver. 
> > Do I miss something ?
> >   
> I did add the Mlock bit to the VMA->vm_flags in my driver before,but I 
> think that's ugly.



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