[158/163] khugepaged: collapse_pte_mapped_thp() flush the right range
diff mbox series

Message ID 20200807062615.qiADx5DeQ%akpm@linux-foundation.org
State New
Headers show
  • [001/163] mm/memory.c: avoid access flag update TLB flush for retried page fault
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Commit Message

Andrew Morton Aug. 7, 2020, 6:26 a.m. UTC
From: Hugh Dickins <hughd@google.com>
Subject: khugepaged: collapse_pte_mapped_thp() flush the right range

pmdp_collapse_flush() should be given the start address at which the huge
page is mapped, haddr: it was given addr, which at that point has been
used as a local variable, incremented to the end address of the extent.

Found by source inspection while chasing a hugepage locking bug, which I
then could not explain by this.  At first I thought this was very bad;
then saw that all of the page translations that were not flushed would
actually still point to the right pages afterwards, so harmless; then
realized that I know nothing of how different architectures and models
cache intermediate paging structures, so maybe it matters after all -
particularly since the page table concerned is immediately freed.

Much easier to fix than to think about.

Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2008021204390.27773@eggly.anvils
Fixes: 27e1f8273113 ("khugepaged: enable collapse pmd for pte-mapped THP")
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: <stable@vger.kernel.org>	[5.4+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

 mm/khugepaged.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff mbox series

--- a/mm/khugepaged.c~khugepaged-collapse_pte_mapped_thp-flush-the-right-range
+++ a/mm/khugepaged.c
@@ -1502,7 +1502,7 @@  void collapse_pte_mapped_thp(struct mm_s
 	/* step 4: collapse pmd */
 	ptl = pmd_lock(vma->vm_mm, pmd);
-	_pmd = pmdp_collapse_flush(vma, addr, pmd);
+	_pmd = pmdp_collapse_flush(vma, haddr, pmd);
 	pte_free(mm, pmd_pgtable(_pmd));