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

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 <redacted>
Reviewed-by: Toshi Kani <redacted>
Cc: Matthew Wilcox <redacted>

Acked-by: Matthew Wilcox <redacted>

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