linux-kernel - [PATCH 3.16.y-ckt 102/183] mm/hugetlb: add migration entry check in __unmap_hugepage

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Message-Id: <1425635874-19087-103-git-send-email-luis.henriques@canonical.com>
Date:	Fri,  6 Mar 2015 09:56:33 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	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>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 102/183] mm/hugetlb: add migration entry check in __unmap_hugepage_range

3.16.7-ckt8 -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: Luis Henriques <luis.henriques@...onical.com>
---
 mm/hugetlb.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 5aab37914cbd..5f217e906ff9 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2660,9 +2660,10 @@ 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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