要按照链表中节点的值对链表进行排序，可以使用以下步骤：

1. 定义链表节点的数据结构：

class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next

2. 编写一个函数来合并两个有序链表：

def mergeTwoLists(l1, l2):
    if not l1:
        return l2
    if not l2:
        return l1
    
    if l1.val < l2.val:
        l1.next = mergeTwoLists(l1.next, l2)
        return l1
    else:
        l2.next = mergeTwoLists(l1, l2.next)
        return l2

3. 编写一个函数来拆分链表：

def splitList(head):
    if not head or not head.next:
        return head
    
    slow = head
    fast = head.next
    
    while fast and fast.next:
        slow = slow.next
        fast = fast.next.next
    
    second_half = slow.next
    slow.next = None
    
    return head, second_half

4. 编写一个函数来进行归并排序：

def mergeSort(head):
    if not head or not head.next:
        return head
    
    first_half, second_half = splitList(head)
    
    first_half = mergeSort(first_half)
    second_half = mergeSort(second_half)
    
    return mergeTwoLists(first_half, second_half)

5. 调用归并排序函数对链表进行排序：

def sortList(head):
    return mergeSort(head)

这样，就可以通过调用sortList(head)函数对链表进行排序。