linux-kernel - [PATCH bugfix] proc/pagemap: correctly report non-present ptes and holes between vmas

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Date:	Sat, 28 Apr 2012 20:22:30 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Andi Kleen <ak@...ux.intel.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: [PATCH bugfix] proc/pagemap: correctly report non-present ptes and
 holes between vmas

This patch resets current pagemap-entry if current pte isn't present,
or if current vma is over. Otherwise pagemap reports last entry again and again.

non-present pte reporting was broken in commit v3.3-3738-g092b50b
("pagemap: introduce data structure for pagemap entry")

reporting for holes was broken in commit v3.3-3734-g5aaabe8
("pagemap: avoid splitting thp when reading /proc/pid/pagemap")

Signed-off-by: Konstantin Khlebnikov <khlebnikov@...nvz.org>
Reported-by: Pavel Emelyanov <xemul@...allels.com>
Cc: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc: Andi Kleen <ak@...ux.intel.com>
---
 fs/proc/task_mmu.c |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index a580c69..9f9c033 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -747,6 +747,8 @@ static void pte_to_pagemap_entry(pagemap_entry_t *pme, pte_t pte)
 	else if (pte_present(pte))
 		*pme = make_pme(PM_PFRAME(pte_pfn(pte))
 				| PM_PSHIFT(PAGE_SHIFT) | PM_PRESENT);
+	else
+		*pme = make_pme(PM_NOT_PRESENT);
 }
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
@@ -761,6 +763,8 @@ static void thp_pmd_to_pagemap_entry(pagemap_entry_t *pme,
 	if (pmd_present(pmd))
 		*pme = make_pme(PM_PFRAME(pmd_pfn(pmd) + offset)
 				| PM_PSHIFT(PAGE_SHIFT) | PM_PRESENT);
+	else
+		*pme = make_pme(PM_NOT_PRESENT);
 }
 #else
 static inline void thp_pmd_to_pagemap_entry(pagemap_entry_t *pme,
@@ -801,8 +805,10 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 
 		/* check to see if we've left 'vma' behind
 		 * and need a new, higher one */
-		if (vma && (addr >= vma->vm_end))
+		if (vma && (addr >= vma->vm_end)) {
 			vma = find_vma(walk->mm, addr);
+			pme = make_pme(PM_NOT_PRESENT);
+		}
 
 		/* check that 'vma' actually covers this address,
 		 * and that it isn't a huge page vma */
@@ -830,6 +836,8 @@ static void huge_pte_to_pagemap_entry(pagemap_entry_t *pme,
 	if (pte_present(pte))
 		*pme = make_pme(PM_PFRAME(pte_pfn(pte) + offset)
 				| PM_PSHIFT(PAGE_SHIFT) | PM_PRESENT);
+	else
+		*pme = make_pme(PM_NOT_PRESENT);
 }
 
 /* This function walks within one hugetlb entry in the single call */
@@ -839,7 +847,7 @@ static int pagemap_hugetlb_range(pte_t *pte, unsigned long hmask,
 {
 	struct pagemapread *pm = walk->private;
 	int err = 0;
-	pagemap_entry_t pme = make_pme(PM_NOT_PRESENT);
+	pagemap_entry_t pme;
 
 	for (; addr != end; addr += PAGE_SIZE) {
 		int offset = (addr & ~hmask) >> PAGE_SHIFT;

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