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@xxxxxxxxxx>
__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@xxxxxxxxxx>
---
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);
--
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