ldd3 scullp编译出错处理

关于main.c中的错误可以参考scullp中的处理方法：
这里主要处理mmap的错误处理：

包含头文件，否则会提示struct semaphore sem没有定义之类的错误。

关键的改变在mmap.c中，由于vm_operations_struct的变化，需要对mmap.c做如下变化：

1. 包含头文件，否则在函数scull_mmap中，会提示

        vma->vm_private_data = filp->private_data;

dereferencing pointer to incomplete type.这是因为其找不到struct file的定义。

2. 以前的函数

        struct page *scullv_vma_nopage(struct vm_area_struct *vma, unsigned long address, int *type)

现在其后面的参数address, type都可以通过结构struct vm_fault来获得。该函数需要改变为：

        static int scullv_vma_fault (struct vm_area_struct *vma, struct vm_fault *vmf)

其函数体也需要作出相应改变：

1. 
   

   static int scullv_vma_fault(struct vm_area_struct *vma,
                               struct vm_fault *vmf)
   {
       unsigned long offset;
       struct scullv_dev *ptr, *dev = vma->vm_private_data;
           struct page *page;
       void *pageptr = NULL; /* default to "missing" */
           pgoff_t pgoff = vmf->pgoff;
   
       down(&dev->sem);
       offset = (pgoff << PAGE_SHIFT) + (vma->vm_pgoff << PAGE_SHIFT);
       if (offset >= dev->size) goto out; /* out of range */
   
       /*
        * Now retrieve the scullv device from the list,then the page.
        * If the device has holes, the process receives a SIGBUS when
        * accessing the hole.
       */
      offset >>= PAGE_SHIFT; /* offset is a number of pages */
      for (ptr = dev; ptr && offset >= dev->qset;) {
           ptr = ptr->next;
           offset -= dev->qset;
       }
       if (ptr && ptr->data) pageptr = ptr->data[offset];
       if (!pageptr) goto out; /* hole or end-of-file */
   
       /*
        * After scullv lookup, "page" is now the address of the page
        * needed by the current process. Since it's a vmalloc address,
        * turn it into a struct page.
        */
        page = vmalloc_to_page(pageptr);
        if (!page)
             return VM_FAULT_SIGBUS;
   
        /* got it, now increment the count */
        vmf->page = page;
   
   out:
        up(&dev->sem);
        return 0;
   }

3. 在结构scull_vm_ops初始化时：

去掉.nopage = scullv_vma_nopage,

修改为.fault = scullv_vma_fault,