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From: Andrea Arcangeli <aarcange@redhat.com>
To: Borislav Petkov <bp@amd64.org>
Cc: werner <w.landgraf@ru.ru>,
	linux-kernel@vger.kernel.org, linux-mm <linux-mm@kvack.org>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: 2.6.38-rc1 problems with khugepaged
Date: Wed, 19 Jan 2011 23:21:50 +0100	[thread overview]
Message-ID: <20110119222150.GP9506@random.random> (raw)
In-Reply-To: <20110119155954.GA2272@kryptos.osrc.amd.com>

Hello Werner,

this should fix your oops, it's untested still so let me know if you
test it.

It's a noop for x86_64 and it only affected x86 32bit with highpte enabled.

====
Subject: khugepaged: fix pte_unmap for highpte x86_32

From: Andrea Arcangeli <aarcange@redhat.com>

__collapse_huge_page_copy is still dereferencing the pte passed as parameter so
we must pte_unmap after __collapse_huge_page_copy returns, not before.

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

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 004c9c2..c4f634b 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1837,9 +1837,9 @@ static void collapse_huge_page(struct mm_struct *mm,
 	spin_lock(ptl);
 	isolated = __collapse_huge_page_isolate(vma, address, pte);
 	spin_unlock(ptl);
-	pte_unmap(pte);
 
 	if (unlikely(!isolated)) {
+		pte_unmap(pte);
 		spin_lock(&mm->page_table_lock);
 		BUG_ON(!pmd_none(*pmd));
 		set_pmd_at(mm, address, pmd, _pmd);
@@ -1856,6 +1856,7 @@ static void collapse_huge_page(struct mm_struct *mm,
 	anon_vma_unlock(vma->anon_vma);
 
 	__collapse_huge_page_copy(pte, new_page, vma, address, ptl);
+	pte_unmap(pte);
 	__SetPageUptodate(new_page);
 	pgtable = pmd_pgtable(_pmd);
 	VM_BUG_ON(page_count(pgtable) != 1);



  parent reply	other threads:[~2011-01-19 22:22 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-01-19 13:45 werner
2011-01-19 15:59 ` Borislav Petkov
2011-01-19 19:55   ` Andrea Arcangeli
2011-01-19 21:45   ` Johannes Weiner
2011-01-20  0:01     ` Andrea Arcangeli
2011-01-20  1:10       ` Johannes Weiner
2011-01-20  1:21         ` Andrea Arcangeli
2011-01-19 22:21   ` Andrea Arcangeli [this message]
2011-01-20 20:13     ` Steven Rostedt
2011-01-21  8:36 werner
2011-01-21 10:43 werner
2011-01-21 19:17 ` Andrea Arcangeli
2011-01-21 21:14   ` Steven Rostedt

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