linux-kernel - [PATCH] mm: pagewalk: call pte_hole() for VM_PFNMAP during walk_page

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Date:	Wed, 21 Jan 2015 11:43:13 +0530
From:	Shiraz Hashim <shashim@...eaurora.org>
To:	linux-mm@...ck.org
Cc:	akpm@...ux-foundation.org, oleg@...hat.com, gorcunov@...nvz.org,
	linux-kernel@...r.kernel.org, n-horiguchi@...jp.nec.com,
	Shiraz Hashim <shashim@...eaurora.org>
Subject: [PATCH] mm: pagewalk: call pte_hole() for VM_PFNMAP during walk_page_range

walk_page_range silently skips vma having VM_PFNMAP set,
which leads to undesirable behaviour at client end (who
called walk_page_range). For example for pagemap_read,
when no callbacks are called against VM_PFNMAP vma,
pagemap_read may prepare pagemap data for next virtual
address range at wrong index.

Signed-off-by: Shiraz Hashim <shashim@...eaurora.org>
---
The fix is revised, based upon the suggestion here at
http://www.spinics.net/lists/linux-mm/msg83058.html

 mm/pagewalk.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index ad83195..b264bda 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -199,7 +199,10 @@ int walk_page_range(unsigned long addr, unsigned long end,
 			 */
 			if ((vma->vm_start <= addr) &&
 			    (vma->vm_flags & VM_PFNMAP)) {
-				next = vma->vm_end;
+				if (walk->pte_hole)
+					err = walk->pte_hole(addr, next, walk);
+				if (err)
+					break;
 				pgd = pgd_offset(walk->mm, next);
 				continue;
 			}
-- 
Shiraz Hashim

QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
member of the Code Aurora Forum, hosted by The Linux Foundation

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