do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
{
	unsigned long pfn;
	struct page *page;
	int move_pages = NR_OFFLINE_AT_ONCE_PAGES;
	int not_managed = 0;
	int ret = 0;
	LIST_HEAD(source);

	for (pfn = start_pfn; pfn < end_pfn && move_pages > 0; pfn++) {
		if (!pfn_valid(pfn))
			continue;
		page = pfn_to_page(pfn);
		if (!get_page_unless_zero(page))
			continue;
		/*
		 * We can skip free pages. And we can only deal with pages on
		 * LRU.
		 */
		ret = isolate_lru_page(page);
		if (!ret) { /* Success */
			put_page(page);
			list_add_tail(&page->lru, &source);
			move_pages--;
			inc_zone_page_state(page, NR_ISOLATED_ANON +
					    page_is_file_cache(page));

		} else {
#ifdef CONFIG_DEBUG_VM
			printk(KERN_ALERT "removing pfn %lx from LRU failed\n",
			       pfn);
			dump_page(page);
#endif
			put_page(page);
			/* Because we don't have big zone->lock. we should
			   check this again here. */
			if (page_count(page)) {
				not_managed++;
				ret = -EBUSY;
				break;
			}
		}
	}
	if (!list_empty(&source)) {
		if (not_managed) {
			putback_lru_pages(&source);
			goto out;
		}
		/* this function returns # of failed pages */
		ret = migrate_pages(&source, hotremove_migrate_alloc, 0,
							true, MIGRATE_SYNC);
		if (ret)
			putback_lru_pages(&source);
	}
out:
	return ret;
}

Unknown