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.

Fixes: 27e1f8273113 ("khugepaged: enable collapse pmd for pte-mapped THP")
Signed-off-by: Hugh Dickins <>
Signed-off-by: Andrew Morton <>
Acked-by: Kirill A. Shutemov <>
Cc: Andrea Arcangeli <>
Cc: Mike Kravetz <>
Cc: Song Liu <>
Cc: <>	[5.4+]
Signed-off-by: Linus Torvalds <>
1 file changed