vm_insert_page

vm_insert_page.c

int _mmap(struct file *f, struct vm_area_struct *vma) {
  unsigned long pages = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
  unsigned long addr;
  struct page *page;
  int i,rc=-ENODEV;
  // TODO need any semaphore for vma manipulation?
  printk(KERN_DEBUG "vma->vm_end %lu vm_start %lu len %lu pages %lu vm_pgoff %lu\n",
    vma->vm_end, vma->vm_start, vma->vm_end - vma->vm_start, pages, vma->vm_pgoff);
  /* allocate and insert pages to fill the vma. */ 
  for(i=0; i < pages; i++) {
    page = alloc_page(GFP_KERNEL); // TODO IO RESERVE?
    if (!page) { 
      // TODO free previous pages
      printk(KERN_DEBUG "alloc_page failed\n");
      goto done;
    }
    addr = vma->vm_start+i*PAGE_SIZE;
    if (vm_insert_page(vma,addr,page) < 0) {
      // TODO free previous pages
      printk(KERN_DEBUG "vm_insert_page failed\n");
      goto done;
    }
    printk(KERN_DEBUG "inserted page %d at %p\n",i,(void*)addr);
    // TODO __free_page now, should be ok, since vm_insert_page incremented its
    // refcount. that way, upon munmap, refcount hits zer0, pages get freed 
    __free_page(page);
  }
  printk(KERN_DEBUG "completed inserting %lu pages\n", pages);
  
  rc = 0;

 done:
  return rc;
}

vm_insert_page_2.c

  pos = usbvision->frame[i].data;
	while (size > 0) {
		if (vm_insert_page(vma, start, vmalloc_to_page(pos))) {
			PDEBUG(DBG_MMAP, "mmap: vm_insert_page failed");
			return -EAGAIN;
		}
		start += PAGE_SIZE;
		pos += PAGE_SIZE;
		size -= PAGE_SIZE;
	}