Commit 453c7192 authored Jan 20, 2011 by Johannes Weiner Committed by Linus Torvalds Jan 20, 2011

thp: keep highpte mapped until it is no longer needed



Two users reported THP-related crashes on 32-bit x86 machines.  Their oops
reports indicated an invalid pte, and subsequent code inspection showed
that the highpte is actually used after unmap.

The fix is to unmap the pte only after all operations against it are
finished.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Ilya Dryomov <idryomov@gmail.com>
Reported-by: werner <w.landgraf@ru.ru>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Tested-by: Ilya Dryomov <idryomov@gmail.com>
Tested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 6a108a14

mm/huge_memory.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -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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