[PATCH v3 10/14] mm: soft-dirty: keep soft-dirty bits over thp migration

[Zi Yan]

From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>

Soft dirty bit is designed to keep tracked over page migration. This patch
makes it work in the same manner for thp migration too.

Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
---
ChangeLog v1 -> v2:
- separate diff moving _PAGE_SWP_SOFT_DIRTY from bit 7 to bit 1
- clear_soft_dirty_pmd can handle migration entry
---
 arch/x86/include/asm/pgtable.h | 17 +++++++++++++++++
 fs/proc/task_mmu.c             | 17 +++++++++++------
 include/asm-generic/pgtable.h  | 34 +++++++++++++++++++++++++++++++++-
 include/linux/swapops.h        |  2 ++
 mm/huge_memory.c               | 24 +++++++++++++++++++++++-
 5 files changed, 86 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 1cfb36b8c024..e57abf8e926c 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -1088,6 +1088,23 @@ static inline pte_t pte_swp_clear_soft_dirty(pte_t pte)
 {
 	return pte_clear_flags(pte, _PAGE_SWP_SOFT_DIRTY);
 }
+
+#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
+static inline pmd_t pmd_swp_mksoft_dirty(pmd_t pmd)
+{
+	return pmd_set_flags(pmd, _PAGE_SWP_SOFT_DIRTY);
+}
+
+static inline int pmd_swp_soft_dirty(pmd_t pmd)
+{
+	return pmd_flags(pmd) & _PAGE_SWP_SOFT_DIRTY;
+}
+
+static inline pmd_t pmd_swp_clear_soft_dirty(pmd_t pmd)
+{
+	return pmd_clear_flags(pmd, _PAGE_SWP_SOFT_DIRTY);
+}
+#endif
 #endif
 
 #define PKRU_AD_BIT 0x1
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 1e64d6898c68..e367dc3afea3 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -900,12 +900,17 @@ static inline void clear_soft_dirty(struct vm_area_struct *vma,
 static inline void clear_soft_dirty_pmd(struct vm_area_struct *vma,
 		unsigned long addr, pmd_t *pmdp)
 {
-	pmd_t pmd = pmdp_huge_get_and_clear(vma->vm_mm, addr, pmdp);
-
-	pmd = pmd_wrprotect(pmd);
-	pmd = pmd_clear_soft_dirty(pmd);
-
-	set_pmd_at(vma->vm_mm, addr, pmdp, pmd);
+	pmd_t pmd = *pmdp;
+
+	if (pmd_present(pmd)) {
+		pmd = pmdp_huge_get_and_clear(vma->vm_mm, addr, pmdp);
+		pmd = pmd_wrprotect(pmd);
+		pmd = pmd_clear_soft_dirty(pmd);
+		set_pmd_at(vma->vm_mm, addr, pmdp, pmd);
+	} else if (is_migration_entry(pmd_to_swp_entry(pmd))) {
+		pmd = pmd_swp_clear_soft_dirty(pmd);
+		set_pmd_at(vma->vm_mm, addr, pmdp, pmd);
+	}
 }
 #else
 static inline void clear_soft_dirty_pmd(struct vm_area_struct *vma,
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 6cf9e9b5a7be..f4c4ee5bce2b 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -550,7 +550,24 @@ static inline void ptep_modify_prot_commit(struct mm_struct *mm,
 #define arch_start_context_switch(prev)	do {} while (0)
 #endif
 
-#ifndef CONFIG_HAVE_ARCH_SOFT_DIRTY
+#ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY
+#ifndef CONFIG_ARCH_ENABLE_THP_MIGRATION
+static inline pmd_t pmd_swp_mksoft_dirty(pmd_t pmd)
+{
+	return pmd;
+}
+
+static inline int pmd_swp_soft_dirty(pmd_t pmd)
+{
+	return 0;
+}
+
+static inline pmd_t pmd_swp_clear_soft_dirty(pmd_t pmd)
+{
+	return pmd;
+}
+#endif
+#else /* !CONFIG_HAVE_ARCH_SOFT_DIRTY */
 static inline int pte_soft_dirty(pte_t pte)
 {
 	return 0;
@@ -595,6 +612,21 @@ static inline pte_t pte_swp_clear_soft_dirty(pte_t pte)
 {
 	return pte;
 }
+
+static inline pmd_t pmd_swp_mksoft_dirty(pmd_t pmd)
+{
+	return pmd;
+}
+
+static inline int pmd_swp_soft_dirty(pmd_t pmd)
+{
+	return 0;
+}
+
+static inline pmd_t pmd_swp_clear_soft_dirty(pmd_t pmd)
+{
+	return pmd;
+}
 #endif
 
 #ifndef __HAVE_PFNMAP_TRACKING
diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index 50e4aa7e7ff9..c22f30a88959 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -179,6 +179,8 @@ static inline swp_entry_t pmd_to_swp_entry(pmd_t pmd)
 {
 	swp_entry_t arch_entry;
 
+	if (pmd_swp_soft_dirty(pmd))
+		pmd = pmd_swp_clear_soft_dirty(pmd);
 	arch_entry = __pmd_to_swp_entry(pmd);
 	return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry));
 }
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 4ac923539372..283c27dd3f36 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -904,6 +904,8 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 		if (is_write_migration_entry(entry)) {
 			make_migration_entry_read(&entry);
 			pmd = swp_entry_to_pmd(entry);
+			if (pmd_swp_soft_dirty(pmd))
+				pmd = pmd_swp_mksoft_dirty(pmd);
 			set_pmd_at(src_mm, addr, src_pmd, pmd);
 		}
 		set_pmd_at(dst_mm, addr, dst_pmd, pmd);
@@ -1726,6 +1728,17 @@ static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
 }
 #endif
 
+static pmd_t move_soft_dirty_pmd(pmd_t pmd)
+{
+#ifdef CONFIG_MEM_SOFT_DIRTY
+	if (unlikely(is_pmd_migration_entry(pmd)))
+		pmd = pmd_swp_mksoft_dirty(pmd);
+	else if (pmd_present(pmd))
+		pmd = pmd_mksoft_dirty(pmd);
+#endif
+	return pmd;
+}
+
 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
 		  unsigned long new_addr, unsigned long old_end,
 		  pmd_t *old_pmd, pmd_t *new_pmd, bool *need_flush)
@@ -1768,7 +1781,8 @@ bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
 			pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
 			pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
 		}
-		set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
+		pmd = move_soft_dirty_pmd(pmd);
+		set_pmd_at(mm, new_addr, new_pmd, pmd);
 		if (new_ptl != old_ptl)
 			spin_unlock(new_ptl);
 		if (force_flush)
@@ -1816,6 +1830,8 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 
 				make_migration_entry_read(&entry);
 				newpmd = swp_entry_to_pmd(entry);
+				if (pmd_swp_soft_dirty(newpmd))
+					newpmd = pmd_swp_mksoft_dirty(newpmd);
 				set_pmd_at(mm, addr, pmd, newpmd);
 			}
 			goto unlock;
@@ -2740,6 +2756,8 @@ void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
 			set_page_dirty(page);
 		entry = make_migration_entry(page, pmd_write(pmdval));
 		pmdswp = swp_entry_to_pmd(entry);
+		if (pmd_soft_dirty(pmdval))
+			pmdswp = pmd_swp_mksoft_dirty(pmdswp);
 		set_pmd_at(mm, address, pvmw->pmd, pmdswp);
 		page_remove_rmap(page, true);
 		put_page(page);
@@ -2756,6 +2774,8 @@ void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
 			set_page_dirty(subpage);
 		entry = make_migration_entry(subpage, pte_write(pteval));
 		swp_pte = swp_entry_to_pte(entry);
+		if (pte_soft_dirty(pteval))
+			swp_pte = pte_swp_mksoft_dirty(swp_pte);
 		set_pte_at(mm, address, pvmw->pte, swp_pte);
 		page_remove_rmap(subpage, false);
 		put_page(subpage);
@@ -2778,6 +2798,8 @@ void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
 		entry = pmd_to_swp_entry(*pvmw->pmd);
 		get_page(new);
 		pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
+		if (pmd_swp_soft_dirty(*pvmw->pmd))
+			pmde = pmd_mksoft_dirty(pmde);
 		if (is_write_migration_entry(entry))
 			pmde = maybe_pmd_mkwrite(pmde, vma);
 
-- 
2.11.0