[PATCH AUTOSEL 4.14 15/61] arm64: hugetlb: Fix handling of young ptes

Sasha Levin
2018-10-16T04:14:22Z

From: Steve Capper <steve.capper@arm.com>

[ Upstream commit 469ed9d823b7d240d6b9574f061ded7c3834c167 ]

In the contiguous bit hugetlb break-before-make code we assume that all
hugetlb pages are young.

In fact, remove_migration_pte is able to place an old hugetlb pte so
this assumption is not valid.

This patch fixes the contiguous hugetlb scanning code to preserve young
ptes.

Fixes: d8bdcff28764 ("arm64: hugetlb: Add break-before-make logic for contiguous entries")
Signed-off-by: Steve Capper <steve.capper@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/arm64/mm/hugetlbpage.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index 6cb0fa92a651..9f6ae9686dac 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -118,11 +118,14 @@ static pte_t get_clear_flush(struct mm_struct *mm,

/*
* If HW_AFDBM is enabled, then the HW could turn on
- * the dirty bit for any page in the set, so check
- * them all. All hugetlb entries are already young.
+ * the dirty or accessed bit for any page in the set,
+ * so check them all.
*/
if (pte_dirty(pte))
orig_pte = pte_mkdirty(orig_pte);
+
+ if (pte_young(pte))
+ orig_pte = pte_mkyoung(orig_pte);
}

if (valid)
@@ -347,10 +350,13 @@ int huge_ptep_set_access_flags(struct vm_area_struct *vma,
if (!pte_same(orig_pte, pte))
changed = 1;

- /* Make sure we don't lose the dirty state */
+ /* Make sure we don't lose the dirty or young state */
if (pte_dirty(orig_pte))
pte = pte_mkdirty(pte);

+ if (pte_young(orig_pte))
+ pte = pte_mkyoung(pte);
+
hugeprot = pte_pgprot(pte);
for (i = 0; i < ncontig; i++, ptep++, addr += pgsize, pfn += dpfn)
set_pte_at(vma->vm_mm, addr, ptep, pfn_pte(pfn, hugeprot));
--
2.17.1