4.14-stable review patch. If anyone has any objections, please let me know.
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From: Yang Shi yang.shi@linux.alibaba.com
[ Upstream commit f0849ac0b8e072073ec5fcc7fadd05a77434364e ]
For PTE-mapped THP, the compound THP has not been split to normal 4K pages yet, the whole THP is considered referenced if any one of sub page is referenced.
When walking PTE-mapped THP by pvmw, all relevant PTEs will be checked to retrieve referenced bit. But, the current code just returns the result of the last PTE. If the last PTE has not referenced, the referenced flag will be cleared.
Just set referenced when ptep{pmdp}_clear_young_notify() returns true.
Link: http://lkml.kernel.org/r/1518212451-87134-1-git-send-email-yang.shi@linux.al... Signed-off-by: Yang Shi yang.shi@linux.alibaba.com Reported-by: Gang Deng gavin.dg@linux.alibaba.com Suggested-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Reviewed-by: Andrew Morton akpm@linux-foundation.org Cc: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/page_idle.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
--- a/mm/page_idle.c +++ b/mm/page_idle.c @@ -65,11 +65,15 @@ static bool page_idle_clear_pte_refs_one while (page_vma_mapped_walk(&pvmw)) { addr = pvmw.address; if (pvmw.pte) { - referenced = ptep_clear_young_notify(vma, addr, - pvmw.pte); + /* + * For PTE-mapped THP, one sub page is referenced, + * the whole THP is referenced. + */ + if (ptep_clear_young_notify(vma, addr, pvmw.pte)) + referenced = true; } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) { - referenced = pmdp_clear_young_notify(vma, addr, - pvmw.pmd); + if (pmdp_clear_young_notify(vma, addr, pvmw.pmd)) + referenced = true; } else { /* unexpected pmd-mapped page? */ WARN_ON_ONCE(1);