From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Date: Wed, 11 Feb 2015 23:25:32 +0000 (-0800)
Subject: mm/hugetlb: add migration entry check in __unmap_hugepage_range
X-Git-Url: https://git.stricted.de/?p=GitHub%2Fmt8127%2Fandroid_kernel_alcatel_ttab.git;a=commitdiff_plain;h=1a25fb791ab61358715554597701d7d708be9c63

mm/hugetlb: add migration entry check in __unmap_hugepage_range

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@ah.jp.nec.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Steve Capper <steve.capper@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 7de4f67c81fe..d9bc87ca062b 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2451,9 +2451,10 @@ again:
 			continue;
 
 		/*
-		 * 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);
 			continue;
 		}