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Subject: [PATCH 27 of 31] pmd_trans_huge migrate bugcheck
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Date: Tue, 26 Jan 2010 14:52:22 +0100
From: Andrea Arcangeli <aarcange@redhat.com>
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To: linux-mm@kvack.org
Cc: Marcelo Tosatti <mtosatti@redhat.com>, Adam Litke <agl@us.ibm.com>, Avi Kivity <avi@redhat.com>, Izik Eidus <ieidus@redhat.com>, Hugh Dickins <hugh.dickins@tiscali.co.uk>, Nick Piggin <npiggin@suse.de>, Rik van Riel <riel@redhat.com>, Mel Gorman <mel@csn.ul.ie>, Andi Kleen <andi@firstfloor.org>, Dave Hansen <dave@linux.vnet.ibm.com>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Ingo Molnar <mingo@elte.hu>, Mike Travis <travis@sgi.com>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, Christoph Lameter <cl@linux-foundation.org>, Chris Wright <chrisw@sous-sol.org>, Andrew Morton <akpm@linux-foundation.org>, bpicco@redhat.com, Christoph Hellwig <chellwig@redhat.com>, KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
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From: Andrea Arcangeli <aarcange@redhat.com>

No pmd_trans_huge should ever materialize in migration ptes areas, because
we split the hugepage before migration ptes are instantiated.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
---

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -107,6 +107,10 @@ static inline int PageTransHuge(struct p
 	VM_BUG_ON(PageTail(page));
 	return PageHead(page);
 }
+static inline int PageTransCompound(struct page *page)
+{
+	return PageCompound(page);
+}
 #else /* CONFIG_TRANSPARENT_HUGEPAGE */
 #define transparent_hugepage_enabled(__vma) 0
 #define transparent_hugepage_defrag(__vma) 0
@@ -124,6 +128,7 @@ static inline int split_huge_page(struct
 #define wait_split_huge_page(__anon_vma, __pmd)	\
 	do { } while (0)
 #define PageTransHuge(page) 0
+#define PageTransCompound(page) 0
 static inline int hugepage_madvise(unsigned long *vm_flags)
 {
 	BUG_ON(0);
diff --git a/mm/migrate.c b/mm/migrate.c
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -99,6 +99,7 @@ static int remove_migration_pte(struct p
 		goto out;
 
 	pmd = pmd_offset(pud, addr);
+	VM_BUG_ON(pmd_trans_huge(*pmd));
 	if (!pmd_present(*pmd))
 		goto out;
 
@@ -819,6 +820,10 @@ static int do_move_page_to_node_array(st
 		if (PageReserved(page) || PageKsm(page))
 			goto put_and_set;
 
+		if (unlikely(PageTransCompound(page)))
+			if (unlikely(split_huge_page(page)))
+				goto put_and_set;
+
 		pp->page = page;
 		err = page_to_nid(page);
 

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