[PATCH v8 10/70] mm: add VMA iterator

[Liam Howlett <liam.howlett@oracle.com>]

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

This thin layer of abstraction over the maple tree state is for iterating
over VMAs.  You can go forwards, go backwards or ask where the iterator
is.  Rename the existing vma_next() to __vma_next() -- it will be removed
by the end of this series.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
---
 include/linux/mm.h       | 31 +++++++++++++++++++++++++++++++
 include/linux/mm_types.h | 21 +++++++++++++++++++++
 mm/mmap.c                | 10 +++++-----
 3 files changed, 57 insertions(+), 5 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 4024ccc94c71..2c639b0a9853 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -658,6 +658,37 @@ static inline bool vma_is_accessible(struct vm_area_struct *vma)
 	return vma->vm_flags & VM_ACCESS_FLAGS;
 }
 
+static inline
+struct vm_area_struct *vma_find(struct vma_iterator *vmi, unsigned long max)
+{
+	return mas_find(&vmi->mas, max);
+}
+
+static inline struct vm_area_struct *vma_next(struct vma_iterator *vmi)
+{
+	/*
+	 * Uses vma_find() to get the first VMA when the iterator starts.
+	 * Calling mas_next() could skip the first entry.
+	 */
+	return vma_find(vmi, ULONG_MAX);
+}
+
+static inline struct vm_area_struct *vma_prev(struct vma_iterator *vmi)
+{
+	return mas_prev(&vmi->mas, 0);
+}
+
+static inline unsigned long vma_iter_addr(struct vma_iterator *vmi)
+{
+	return vmi->mas.index;
+}
+
+#define for_each_vma(vmi, vma)		while ((vma = vma_next(&(vmi))) != NULL)
+
+/* The MM code likes to work with exclusive end addresses */
+#define for_each_vma_range(vmi, vma, end)				\
+	while ((vma = vma_find(&(vmi), (end) - 1)) != NULL)
+
 #ifdef CONFIG_SHMEM
 /*
  * The vma_is_shmem is not inline because it is used only by slow
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 0953add99518..6b31c5252b76 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -678,6 +678,27 @@ static inline cpumask_t *mm_cpumask(struct mm_struct *mm)
 	return (struct cpumask *)&mm->cpu_bitmap;
 }
 
+struct vma_iterator {
+	struct ma_state mas;
+};
+
+#define VMA_ITERATOR(name, mm, addr) 					\
+	struct vma_iterator name = {					\
+		.mas = {						\
+			.tree = &mm->mm_mt,				\
+			.index = addr,					\
+			.node = MAS_START,				\
+		},							\
+	}
+
+static inline void vma_iter_init(struct vma_iterator *vmi,
+		struct mm_struct *mm, unsigned long addr)
+{
+	vmi->mas.tree = &mm->mm_mt;
+	vmi->mas.index = addr;
+	vmi->mas.node = MAS_START;
+}
+
 struct mmu_gather;
 extern void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm);
 extern void tlb_gather_mmu_fullmm(struct mmu_gather *tlb, struct mm_struct *mm);
diff --git a/mm/mmap.c b/mm/mmap.c
index 4512f64a30ab..176f114c2ad2 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -635,7 +635,7 @@ static int find_vma_links(struct mm_struct *mm, unsigned long addr,
 }
 
 /*
- * vma_next() - Get the next VMA.
+ * __vma_next() - Get the next VMA.
  * @mm: The mm_struct.
  * @vma: The current vma.
  *
@@ -643,7 +643,7 @@ static int find_vma_links(struct mm_struct *mm, unsigned long addr,
  *
  * Returns: The next VMA after @vma.
  */
-static inline struct vm_area_struct *vma_next(struct mm_struct *mm,
+static inline struct vm_area_struct *__vma_next(struct mm_struct *mm,
 					 struct vm_area_struct *vma)
 {
 	if (!vma)
@@ -1317,7 +1317,7 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm,
 	if (vm_flags & VM_SPECIAL)
 		return NULL;
 
-	next = vma_next(mm, prev);
+	next = __vma_next(mm, prev);
 	area = next;
 	if (area && area->vm_end == end)		/* cases 6, 7, 8 */
 		next = next->vm_next;
@@ -2836,7 +2836,7 @@ static void unmap_region(struct mm_struct *mm,
 		struct vm_area_struct *vma, struct vm_area_struct *prev,
 		unsigned long start, unsigned long end)
 {
-	struct vm_area_struct *next = vma_next(mm, prev);
+	struct vm_area_struct *next = __vma_next(mm, prev);
 	struct mmu_gather tlb;
 
 	lru_add_drain();
@@ -3035,7 +3035,7 @@ int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
 		if (error)
 			return error;
 	}
-	vma = vma_next(mm, prev);
+	vma = __vma_next(mm, prev);
 
 	if (unlikely(uf)) {
 		/*
-- 
2.35.1