[PATCH v2 16/70] mm: Move find_vma_intersection to mmap.c and change implementation to maple tree.

["Liam R. Howlett" <Liam.Howlett@Oracle.com>]

When searching for a vma within a range, it is easier to use the maple
tree interface.  This means the find_vma() call changes to a special
case of the find_vma_intersection().  Exported for kvm module.

Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
---
 include/linux/mm.h | 10 ++--------
 mm/mmap.c          | 41 ++++++++++++++++++++++++++++-------------
 2 files changed, 30 insertions(+), 21 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index baaad07c43c99..996353a057500 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2651,14 +2651,8 @@ extern struct vm_area_struct * find_vma_prev(struct mm_struct * mm, unsigned lon
 
 /* Look up the first VMA which intersects the interval start_addr..end_addr-1,
    NULL if none.  Assume start_addr < end_addr. */
-static inline struct vm_area_struct * find_vma_intersection(struct mm_struct * mm, unsigned long start_addr, unsigned long end_addr)
-{
-	struct vm_area_struct * vma = find_vma(mm,start_addr);
-
-	if (vma && end_addr <= vma->vm_start)
-		vma = NULL;
-	return vma;
-}
+extern struct vm_area_struct *find_vma_intersection(struct mm_struct *mm,
+		     unsigned long start_addr, unsigned long end_addr);
 
 static inline unsigned long vm_start_gap(struct vm_area_struct *vma)
 {
diff --git a/mm/mmap.c b/mm/mmap.c
index cab665a6daa05..6be58594afb3d 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2067,32 +2067,47 @@ get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
 
 EXPORT_SYMBOL(get_unmapped_area);
 
-/**
- * find_vma() - Find the VMA for a given address, or the next vma.
- * @mm The mm_struct to check
- * @addr: The address
+/*
+ * find_vma_intersection - Find the first vma between [@start, @end)
+ * @mm: The mm_struct to use.
+ * @start: The start address
+ * @end: The end address
  *
- * Returns: The VMA assoicated with addr, or the next vma.
- * May return NULL in the case of no vma at addr or above.
+ * Returns: The VMA associated with the @start or the next VMA within the range.
  */
-struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
+struct vm_area_struct *find_vma_intersection(struct mm_struct *mm,
+					     unsigned long start_addr,
+					     unsigned long end_addr)
 {
 	struct vm_area_struct *vma;
-	MA_STATE(mas, &mm->mm_mt, start_addr, start_addr);
+	unsigned long addr = start_addr;
 
 	/* Check the cache first. */
-	vma = vmacache_find(mm, addr);
+	vma = vmacache_find(mm, start_addr);
 	if (likely(vma))
 		return vma;
 
-	rcu_read_lock();
-	vma = mas_find(&mas, end_addr - 1);
-	rcu_read_unlock();
+	vma = mt_find(&mm->mm_mt, &addr, end_addr - 1);
 	if (vma)
-		vmacache_update(addr, vma);
+		vmacache_update(start_addr, vma);
 
 	return vma;
 }
+EXPORT_SYMBOL(find_vma_intersection);
+
+/**
+ * find_vma() - Find the VMA for a given address, or the next vma.
+ * @mm:  The mm_struct to check
+ * @addr: The address
+ *
+ * Returns: The VMA associated with addr, or the next vma.
+ * May return NULL in the case of no vma at addr or above.
+ */
+struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
+{
+	// Note find_vma_intersection will decrease 0 to underflow to ULONG_MAX
+	return find_vma_intersection(mm, addr, 0);
+}
 EXPORT_SYMBOL(find_vma);
 
 /**
-- 
2.28.0