linux-kernel - Re: [PATCH] mm: make GUP handle pfn mapping unless FOLL

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Message-ID: <20150624164059.GF1971@linux.intel.com>
Date:	Wed, 24 Jun 2015 12:40:59 -0400
From:	Matthew Wilcox <willy@...ux.intel.com>
To:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-nvdimm@...ts.01.org
Subject: 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 <kirill.shutemov@...ux.intel.com>
> Reviewed-by: Toshi Kani <toshi.kani@...com>
> Cc: Matthew Wilcox <willy@...ux.intel.com>

Acked-by: Matthew Wilcox <willy@...ux.intel.com>
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