1 files changed, 65 insertions, 13 deletions

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 003f7bc..86fe697 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -606,7 +606,7 @@ static int __do_huge_pmd_anonymous_page(struct vm_fault *vmf, struct page *page,
 		pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
 		set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
 		add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
-		atomic_long_inc(&vma->vm_mm->nr_ptes);
+		mm_inc_nr_ptes(vma->vm_mm);
 		spin_unlock(vmf->ptl);
 		count_vm_event(THP_FAULT_ALLOC);
 	}
@@ -662,7 +662,7 @@ static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
 	if (pgtable)
 		pgtable_trans_huge_deposit(mm, pmd, pgtable);
 	set_pmd_at(mm, haddr, pmd, entry);
-	atomic_long_inc(&mm->nr_ptes);
+	mm_inc_nr_ptes(mm);
 	return true;
 }
 
@@ -747,7 +747,7 @@ static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 
 	if (pgtable) {
 		pgtable_trans_huge_deposit(mm, pmd, pgtable);
-		atomic_long_inc(&mm->nr_ptes);
+		mm_inc_nr_ptes(mm);
 	}
 
 	set_pmd_at(mm, addr, pmd, entry);
@@ -942,7 +942,7 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 			set_pmd_at(src_mm, addr, src_pmd, pmd);
 		}
 		add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
-		atomic_long_inc(&dst_mm->nr_ptes);
+		mm_inc_nr_ptes(dst_mm);
 		pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
 		set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 		ret = 0;
@@ -978,7 +978,7 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 	get_page(src_page);
 	page_dup_rmap(src_page, true);
 	add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
-	atomic_long_inc(&dst_mm->nr_ptes);
+	mm_inc_nr_ptes(dst_mm);
 	pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
 
 	pmdp_set_wrprotect(src_mm, addr, src_pmd);
@@ -1189,8 +1189,15 @@ static int do_huge_pmd_wp_page_fallback(struct vm_fault *vmf, pmd_t orig_pmd,
 		goto out_free_pages;
 	VM_BUG_ON_PAGE(!PageHead(page), page);
 
+	/*
+	 * Leave pmd empty until pte is filled note we must notify here as
+	 * concurrent CPU thread might write to new page before the call to
+	 * mmu_notifier_invalidate_range_end() happens which can lead to a
+	 * device seeing memory write in different order than CPU.
+	 *
+	 * See Documentation/vm/mmu_notifier.txt
+	 */
 	pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
-	/* leave pmd empty until pte is filled */
 
 	pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
 	pmd_populate(vma->vm_mm, &_pmd, pgtable);
@@ -1216,7 +1223,12 @@ static int do_huge_pmd_wp_page_fallback(struct vm_fault *vmf, pmd_t orig_pmd,
 	page_remove_rmap(page, true);
 	spin_unlock(vmf->ptl);
 
-	mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
+	/*
+	 * No need to double call mmu_notifier->invalidate_range() callback as
+	 * the above pmdp_huge_clear_flush_notify() did already call it.
+	 */
+	mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
+						mmun_end);
 
 	ret |= VM_FAULT_WRITE;
 	put_page(page);
@@ -1365,7 +1377,12 @@ alloc:
 	}
 	spin_unlock(vmf->ptl);
 out_mn:
-	mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
+	/*
+	 * No need to double call mmu_notifier->invalidate_range() callback as
+	 * the above pmdp_huge_clear_flush_notify() did already call it.
+	 */
+	mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
+					       mmun_end);
 out:
 	return ret;
 out_unlock:
@@ -1678,7 +1695,7 @@ static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
 
 	pgtable = pgtable_trans_huge_withdraw(mm, pmd);
 	pte_free(mm, pgtable);
-	atomic_long_dec(&mm->nr_ptes);
+	mm_dec_nr_ptes(mm);
 }
 
 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
@@ -2017,7 +2034,12 @@ void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
 
 out:
 	spin_unlock(ptl);
-	mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PUD_SIZE);
+	/*
+	 * No need to double call mmu_notifier->invalidate_range() callback as
+	 * the above pudp_huge_clear_flush_notify() did already call it.
+	 */
+	mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +
+					       HPAGE_PUD_SIZE);
 }
 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
 
@@ -2029,8 +2051,15 @@ static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
 	pmd_t _pmd;
 	int i;
 
-	/* leave pmd empty until pte is filled */
-	pmdp_huge_clear_flush_notify(vma, haddr, pmd);
+	/*
+	 * Leave pmd empty until pte is filled note that it is fine to delay
+	 * notification until mmu_notifier_invalidate_range_end() as we are
+	 * replacing a zero pmd write protected page with a zero pte write
+	 * protected page.
+	 *
+	 * See Documentation/vm/mmu_notifier.txt
+	 */
+	pmdp_huge_clear_flush(vma, haddr, pmd);
 
 	pgtable = pgtable_trans_huge_withdraw(mm, pmd);
 	pmd_populate(mm, &_pmd, pgtable);
@@ -2085,6 +2114,15 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
 		add_mm_counter(mm, MM_FILEPAGES, -HPAGE_PMD_NR);
 		return;
 	} else if (is_huge_zero_pmd(*pmd)) {
+		/*
+		 * FIXME: Do we want to invalidate secondary mmu by calling
+		 * mmu_notifier_invalidate_range() see comments below inside
+		 * __split_huge_pmd() ?
+		 *
+		 * We are going from a zero huge page write protected to zero
+		 * small page also write protected so it does not seems useful
+		 * to invalidate secondary mmu at this time.
+		 */
 		return __split_huge_zero_page_pmd(vma, haddr, pmd);
 	}
 
@@ -2220,7 +2258,21 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 	__split_huge_pmd_locked(vma, pmd, haddr, freeze);
 out:
 	spin_unlock(ptl);
-	mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
+	/*
+	 * No need to double call mmu_notifier->invalidate_range() callback.
+	 * They are 3 cases to consider inside __split_huge_pmd_locked():
+	 *  1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
+	 *  2) __split_huge_zero_page_pmd() read only zero page and any write
+	 *    fault will trigger a flush_notify before pointing to a new page
+	 *    (it is fine if the secondary mmu keeps pointing to the old zero
+	 *    page in the meantime)
+	 *  3) Split a huge pmd into pte pointing to the same page. No need
+	 *     to invalidate secondary tlb entry they are all still valid.
+	 *     any further changes to individual pte will notify. So no need
+	 *     to call mmu_notifier->invalidate_range()
+	 */
+	mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +
+					       HPAGE_PMD_SIZE);
 }
 
 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,