mmap: Use the VMA iterator in count_vma_pages_range()

This simplifies the implementation and is faster than using the linked
list.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

diff --git a/mm/mmap.c b/mm/mmap.c
index 9fee6e6b276f5c288b87da65c61577f310013d68..de78fc0ce8094789501bd8c8ad3252f5d2587489 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -669,29 +669,19 @@ munmap_vma_range(struct mm_struct *mm, unsigned long start, unsigned long len,
 
        return 0;
 }
+
 static unsigned long count_vma_pages_range(struct mm_struct *mm,
                unsigned long addr, unsigned long end)
 {
-       unsigned long nr_pages = 0;
+       VMA_ITERATOR(vmi, mm, addr);
        struct vm_area_struct *vma;
+       unsigned long nr_pages = 0;
 
-       /* Find first overlapping mapping */
-       vma = find_vma_intersection(mm, addr, end);
-       if (!vma)
-               return 0;
-
-       nr_pages = (min(end, vma->vm_end) -
-               max(addr, vma->vm_start)) >> PAGE_SHIFT;
-
-       /* Iterate over the rest of the overlaps */
-       for (vma = vma->vm_next; vma; vma = vma->vm_next) {
-               unsigned long overlap_len;
-
-               if (vma->vm_start > end)
-                       break;
+       for_each_vma_range(vmi, vma, end) {
+               unsigned long vm_start = max(addr, vma->vm_start);
+               unsigned long vm_end = min(end, vma->vm_end);
 
-               overlap_len = min(end, vma->vm_end) - vma->vm_start;
-               nr_pages += overlap_len >> PAGE_SHIFT;
+               nr_pages += (vm_end - vm_start) / PAGE_SIZE;
        }
 
        return nr_pages;