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Subject[RFC PATCH v2 11/30] mm: thp: handling PUD THP reference bit.
Date
From: Zi Yan <ziy@nvidia.com>

Add PUD-level TLB flush ops and teach page_vma_mapped_talk about PUD
THPs.

Signed-off-by: Zi Yan <ziy@nvidia.com>
---
arch/x86/include/asm/pgtable.h | 3 +++
arch/x86/mm/pgtable.c | 13 +++++++++++++
include/linux/mmu_notifier.h | 13 +++++++++++++
include/linux/pgtable.h | 14 ++++++++++++++
include/linux/rmap.h | 1 +
mm/page_vma_mapped.c | 33 +++++++++++++++++++++++++++++----
mm/rmap.c | 12 +++++++++---
7 files changed, 82 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 199de6be2f6d..8bf7bfd71a46 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -1127,6 +1127,9 @@ extern int pudp_test_and_clear_young(struct vm_area_struct *vma,
extern int pmdp_clear_flush_young(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmdp);

+#define __HAVE_ARCH_PUDP_CLEAR_YOUNG_FLUSH
+extern int pudp_clear_flush_young(struct vm_area_struct *vma,
+ unsigned long address, pud_t *pudp);

#define pmd_write pmd_write
static inline int pmd_write(pmd_t pmd)
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 7be73aee6183..e4a2dffcc418 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -633,6 +633,19 @@ int pmdp_clear_flush_young(struct vm_area_struct *vma,

return young;
}
+int pudp_clear_flush_young(struct vm_area_struct *vma,
+ unsigned long address, pud_t *pudp)
+{
+ int young;
+
+ VM_BUG_ON(address & ~HPAGE_PUD_MASK);
+
+ young = pudp_test_and_clear_young(vma, address, pudp);
+ if (young)
+ flush_tlb_range(vma, address, address + HPAGE_PUD_SIZE);
+
+ return young;
+}
#endif

/**
diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
index b8200782dede..4ffa179e654f 100644
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -557,6 +557,19 @@ static inline void mmu_notifier_range_init_migrate(
__young; \
})

+#define pudp_clear_flush_young_notify(__vma, __address, __pudp) \
+({ \
+ int __young; \
+ struct vm_area_struct *___vma = __vma; \
+ unsigned long ___address = __address; \
+ __young = pudp_clear_flush_young(___vma, ___address, __pudp); \
+ __young |= mmu_notifier_clear_flush_young(___vma->vm_mm, \
+ ___address, \
+ ___address + \
+ PUD_SIZE); \
+ __young; \
+})
+
#define ptep_clear_young_notify(__vma, __address, __ptep) \
({ \
int __young; \
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 1f6d46465c54..bb163504fb01 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -243,6 +243,20 @@ static inline int pmdp_clear_flush_young(struct vm_area_struct *vma,
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
#endif

+#ifndef __HAVE_ARCH_PUDP_CLEAR_YOUNG_FLUSH
+#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
+extern int pudp_clear_flush_young(struct vm_area_struct *vma,
+ unsigned long address, pud_t *pudp);
+#else
+int pudp_clear_flush_young(struct vm_area_struct *vma,
+ unsigned long address, pud_t *pudp)
+{
+ BUILD_BUG();
+ return 0;
+}
+#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
+#endif
+
#ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR
static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
unsigned long address,
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 3a6adfa70fb0..0af61dd193d2 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -206,6 +206,7 @@ struct page_vma_mapped_walk {
struct page *page;
struct vm_area_struct *vma;
unsigned long address;
+ pud_t *pud;
pmd_t *pmd;
pte_t *pte;
spinlock_t *ptl;
diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 5e77b269c330..f88e845ad5e6 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -145,9 +145,12 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
struct page *page = pvmw->page;
pgd_t *pgd;
p4d_t *p4d;
- pud_t *pud;
+ pud_t pude;
pmd_t pmde;

+ if (!pvmw->pte && !pvmw->pmd && pvmw->pud)
+ return not_found(pvmw);
+
/* The only possible pmd mapping has been handled on last iteration */
if (pvmw->pmd && !pvmw->pte)
return not_found(pvmw);
@@ -174,10 +177,32 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
p4d = p4d_offset(pgd, pvmw->address);
if (!p4d_present(*p4d))
return false;
- pud = pud_offset(p4d, pvmw->address);
- if (!pud_present(*pud))
+ pvmw->pud = pud_offset(p4d, pvmw->address);
+
+ /*
+ * Make sure the pud value isn't cached in a register by the
+ * compiler and used as a stale value after we've observed a
+ * subsequent update.
+ */
+ pude = READ_ONCE(*pvmw->pud);
+ if (pud_trans_huge(pude)) {
+ pvmw->ptl = pud_lock(mm, pvmw->pud);
+ if (likely(pud_trans_huge(*pvmw->pud))) {
+ if (pvmw->flags & PVMW_MIGRATION)
+ return not_found(pvmw);
+ if (pud_page(*pvmw->pud) != page)
+ return not_found(pvmw);
+ return true;
+ } else if (!pud_present(*pvmw->pud))
+ return not_found(pvmw);
+
+ /* THP pud was split under us: handle on pmd level */
+ spin_unlock(pvmw->ptl);
+ pvmw->ptl = NULL;
+ } else if (!pud_present(pude))
return false;
- pvmw->pmd = pmd_offset(pud, pvmw->address);
+
+ pvmw->pmd = pmd_offset(pvmw->pud, pvmw->address);
/*
* Make sure the pmd value isn't cached in a register by the
* compiler and used as a stale value after we've observed a
diff --git a/mm/rmap.c b/mm/rmap.c
index 5683f367a792..629f8fe7ffac 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -803,9 +803,15 @@ static bool page_referenced_one(struct page *page, struct vm_area_struct *vma,
referenced++;
}
} else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
- if (pmdp_clear_flush_young_notify(vma, address,
- pvmw.pmd))
- referenced++;
+ if (pvmw.pmd) {
+ if (pmdp_clear_flush_young_notify(vma, address,
+ pvmw.pmd))
+ referenced++;
+ } else if (pvmw.pud) {
+ if (pudp_clear_flush_young_notify(vma, address,
+ pvmw.pud))
+ referenced++;
+ }
} else {
/* unexpected pmd-mapped page? */
WARN_ON_ONCE(1);
--
2.28.0
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