madvise: use split_vma() instead of __split_vma()

The split_vma() wrapper is specifically for this use case, so use it.

[Liam.Howlett@oracle.com: fix VMA_ITERATOR start position]
  Link: https://lkml.kernel.org/r/20230125135809.85262-1-Liam.Howlett@oracle.com
Link: https://lkml.kernel.org/r/20230120162650.984577-34-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/madvise.c

@@ -142,7 +142,7 @@ static int madvise_update_vma(struct vm_area_struct *vma,
 	struct mm_struct *mm = vma->vm_mm;
 	int error;
 	pgoff_t pgoff;
-	VMA_ITERATOR(vmi, mm, 0);
+	VMA_ITERATOR(vmi, mm, start);
 
 	if (new_flags == vma->vm_flags && anon_vma_name_eq(anon_vma_name(vma), anon_name)) {
 		*prev = vma;
@@ -161,17 +161,13 @@ static int madvise_update_vma(struct vm_area_struct *vma,
 	*prev = vma;
 
 	if (start != vma->vm_start) {
-		if (unlikely(mm->map_count >= sysctl_max_map_count))
-			return -ENOMEM;
-		error = __split_vma(&vmi, vma, start, 1);
+		error = split_vma(&vmi, vma, start, 1);
 		if (error)
 			return error;
 	}
 
 	if (end != vma->vm_end) {
-		if (unlikely(mm->map_count >= sysctl_max_map_count))
-			return -ENOMEM;
-		error = __split_vma(&vmi, vma, end, 0);
+		error = split_vma(&vmi, vma, end, 0);
 		if (error)
 			return error;
 	}