linux-kernel - [PATCH 3.19 033/177] mm/hugetlb: add migration entry check in __unmap_hugepage

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Message-Id: <20150316140814.611761335@linuxfoundation.org>
Date:	Mon, 16 Mar 2015 15:07:20 +0100
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Hugh Dickins <hughd@...gle.com>,
	James Hogan <james.hogan@...tec.com>,
	David Rientjes <rientjes@...gle.com>,
	Mel Gorman <mel@....ul.ie>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>, Rik van Riel <riel@...hat.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Luiz Capitulino <lcapitulino@...hat.com>,
	Nishanth Aravamudan <nacc@...ux.vnet.ibm.com>,
	Lee Schermerhorn <lee.schermerhorn@...com>,
	Steve Capper <steve.capper@...aro.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 3.19 033/177] mm/hugetlb: add migration entry check in __unmap_hugepage_range

3.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Naoya Horiguchi <n-horiguchi@...jp.nec.com>

commit 9fbc1f635fd0bd28cb32550211bf095753ac637a upstream.

If __unmap_hugepage_range() tries to unmap the address range over which
hugepage migration is on the way, we get the wrong page because pte_page()
doesn't work for migration entries.  This patch simply clears the pte for
migration entries as we do for hwpoison entries.

Fixes: 290408d4a2 ("hugetlb: hugepage migration core")
Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: James Hogan <james.hogan@...tec.com>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Mel Gorman <mel@....ul.ie>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: Michal Hocko <mhocko@...e.cz>
Cc: Rik van Riel <riel@...hat.com>
Cc: Andrea Arcangeli <aarcange@...hat.com>
Cc: Luiz Capitulino <lcapitulino@...hat.com>
Cc: Nishanth Aravamudan <nacc@...ux.vnet.ibm.com>
Cc: Lee Schermerhorn <lee.schermerhorn@...com>
Cc: Steve Capper <steve.capper@...aro.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 mm/hugetlb.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2657,9 +2657,10 @@ again:
 			goto unlock;
 
 		/*
-		 * HWPoisoned hugepage is already unmapped and dropped reference
+		 * Migrating hugepage or HWPoisoned hugepage is already
+		 * unmapped and its refcount is dropped, so just clear pte here.
 		 */
-		if (unlikely(is_hugetlb_entry_hwpoisoned(pte))) {
+		if (unlikely(!pte_present(pte))) {
 			huge_pte_clear(mm, address, ptep);
 			goto unlock;
 		}


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