Re: [PATCH] mm: make GUP handle pfn mapping unless FOLL_GET is requested

[Matthew Wilcox]

On Wed, Jun 24, 2015 at 01:25:03PM +0300, Kirill A. Shutemov wrote:
> With DAX, pfn mapping becoming more common. The patch adjusts GUP code
> to cover pfn mapping for cases when we don't need struct page to
> proceed.
> 
> To make it possible, let's change follow_page() code to return -EEXIST
> error code if proper page table entry exists, but no corresponding
> struct page. __get_user_page() would ignore the error code and move to
> the next page frame.
> 
> The immediate effect of the change is working MAP_POPULATE and mlock()
> on DAX mappings.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Reviewed-by: Toshi Kani <toshi.kani@xxxxxx>
> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxxxx>

Acked-by: Matthew Wilcox <willy@xxxxxxxxxxxxxxx>
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