page_range_contiguous
bool page_range_contiguous(const struct page *page, unsigned long nr_pages);
VM_WARN_ON_ONCE(!page_range_contiguous(page, ALIGN(len + offset, PAGE_SIZE) / PAGE_SIZE));
if (!page_range_contiguous(page, count)) {
VM_WARN_ON_ONCE(!page_range_contiguous(page, npages));
EXPORT_SYMBOL(page_range_contiguous);