/*
   * linux/mm/page_isolation.c
   */
  
  #include <linux/mm.h>
  #include <linux/page-isolation.h>
  #include <linux/pageblock-flags.h>
  #include <linux/memory.h>
  #include <linux/hugetlb.h>
  #include "internal.h"
  
  int set_migratetype_isolate(struct page *page, bool skip_hwpoisoned_pages)
  {
  	struct zone *zone;
  	unsigned long flags, pfn;
  	struct memory_isolate_notify arg;
  	int notifier_ret;
  	int ret = -EBUSY;
  
  	zone = page_zone(page);
  
  	spin_lock_irqsave(&zone->lock, flags);
  
  	pfn = page_to_pfn(page);
  	arg.start_pfn = pfn;
  	arg.nr_pages = pageblock_nr_pages;
  	arg.pages_found = 0;
  
  	/*
  	 * It may be possible to isolate a pageblock even if the
  	 * migratetype is not MIGRATE_MOVABLE. The memory isolation
  	 * notifier chain is used by balloon drivers to return the
  	 * number of pages in a range that are held by the balloon
  	 * driver to shrink memory. If all the pages are accounted for
  	 * by balloons, are free, or on the LRU, isolation can continue.
  	 * Later, for example, when memory hotplug notifier runs, these
  	 * pages reported as "can be isolated" should be isolated(freed)
  	 * by the balloon driver through the memory notifier chain.
  	 */
  	notifier_ret = memory_isolate_notify(MEM_ISOLATE_COUNT, &arg);
  	notifier_ret = notifier_to_errno(notifier_ret);
  	if (notifier_ret)
  		goto out;
  	/*
  	 * FIXME: Now, memory hotplug doesn't call shrink_slab() by itself.
  	 * We just check MOVABLE pages.
  	 */
  	if (!has_unmovable_pages(zone, page, arg.pages_found,
  				 skip_hwpoisoned_pages))
  		ret = 0;
  
  	/*
  	 * immobile means "not-on-lru" paes. If immobile is larger than
  	 * removable-by-driver pages reported by notifier, we'll fail.
  	 */
  
  out:
  	if (!ret) {
  		unsigned long nr_pages;
  		int migratetype = get_pageblock_migratetype(page);
  
  		set_pageblock_migratetype(page, MIGRATE_ISOLATE);
  		nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE);
  
  		__mod_zone_freepage_state(zone, -nr_pages, migratetype);
  	}
  
  	spin_unlock_irqrestore(&zone->lock, flags);
  	if (!ret)
  		drain_all_pages();
  	return ret;
  }
  
  void unset_migratetype_isolate(struct page *page, unsigned migratetype)
  {
  	struct zone *zone;
  	unsigned long flags, nr_pages;
  
  	zone = page_zone(page);
  	spin_lock_irqsave(&zone->lock, flags);
  	if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
  		goto out;
  	nr_pages = move_freepages_block(zone, page, migratetype);
  	__mod_zone_freepage_state(zone, nr_pages, migratetype);
  	set_pageblock_migratetype(page, migratetype);
  out:
  	spin_unlock_irqrestore(&zone->lock, flags);
  }
  
  static inline struct page *
  __first_valid_page(unsigned long pfn, unsigned long nr_pages)
  {
  	int i;
  	for (i = 0; i < nr_pages; i++)
  		if (pfn_valid_within(pfn + i))
  			break;
  	if (unlikely(i == nr_pages))
  		return NULL;
  	return pfn_to_page(pfn + i);
  }
  
  /*
   * start_isolate_page_range() -- make page-allocation-type of range of pages
   * to be MIGRATE_ISOLATE.
   * @start_pfn: The lower PFN of the range to be isolated.
   * @end_pfn: The upper PFN of the range to be isolated.
   * @migratetype: migrate type to set in error recovery.
   *
   * Making page-allocation-type to be MIGRATE_ISOLATE means free pages in
   * the range will never be allocated. Any free pages and pages freed in the
   * future will not be allocated again.
   *
   * start_pfn/end_pfn must be aligned to pageblock_order.
   * Returns 0 on success and -EBUSY if any part of range cannot be isolated.
   */
  int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
  			     unsigned migratetype, bool skip_hwpoisoned_pages)
  {
  	unsigned long pfn;
  	unsigned long undo_pfn;
  	struct page *page;
  
  	BUG_ON((start_pfn) & (pageblock_nr_pages - 1));
  	BUG_ON((end_pfn) & (pageblock_nr_pages - 1));
  
  	for (pfn = start_pfn;
  	     pfn < end_pfn;
  	     pfn += pageblock_nr_pages) {
  		page = __first_valid_page(pfn, pageblock_nr_pages);
  		if (page &&
  		    set_migratetype_isolate(page, skip_hwpoisoned_pages)) {
  			undo_pfn = pfn;
  			goto undo;
  		}
  	}
  	return 0;
  undo:
  	for (pfn = start_pfn;
  	     pfn < undo_pfn;
  	     pfn += pageblock_nr_pages)
  		unset_migratetype_isolate(pfn_to_page(pfn), migratetype);
  
  	return -EBUSY;
  }
  
  /*
   * Make isolated pages available again.
   */
  int undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
  			    unsigned migratetype)
  {
  	unsigned long pfn;
  	struct page *page;
  	BUG_ON((start_pfn) & (pageblock_nr_pages - 1));
  	BUG_ON((end_pfn) & (pageblock_nr_pages - 1));
  	for (pfn = start_pfn;
  	     pfn < end_pfn;
  	     pfn += pageblock_nr_pages) {
  		page = __first_valid_page(pfn, pageblock_nr_pages);
  		if (!page || get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
  			continue;
  		unset_migratetype_isolate(page, migratetype);
  	}
  	return 0;
  }
  /*
   * Test all pages in the range is free(means isolated) or not.
   * all pages in [start_pfn...end_pfn) must be in the same zone.
   * zone->lock must be held before call this.
   *
   * Returns 1 if all pages in the range are isolated.
   */
  static int
  __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn,
  				  bool skip_hwpoisoned_pages)
  {
  	struct page *page;
  
  	while (pfn < end_pfn) {
  		if (!pfn_valid_within(pfn)) {
  			pfn++;
  			continue;
  		}
  		page = pfn_to_page(pfn);
  		if (PageBuddy(page)) {
  			/*
  			 * If race between isolatation and allocation happens,
  			 * some free pages could be in MIGRATE_MOVABLE list
  			 * although pageblock's migratation type of the page
  			 * is MIGRATE_ISOLATE. Catch it and move the page into
  			 * MIGRATE_ISOLATE list.
  			 */
  			if (get_freepage_migratetype(page) != MIGRATE_ISOLATE) {
  				struct page *end_page;
  
  				end_page = page + (1 << page_order(page)) - 1;
  				move_freepages(page_zone(page), page, end_page,
  						MIGRATE_ISOLATE);
  			}
  			pfn += 1 << page_order(page);
  		}
  		else if (page_count(page) == 0 &&
  			get_freepage_migratetype(page) == MIGRATE_ISOLATE)
  			pfn += 1;
  		else if (skip_hwpoisoned_pages && PageHWPoison(page)) {
  			/*
  			 * The HWPoisoned page may be not in buddy
  			 * system, and page_count() is not 0.
  			 */
  			pfn++;
  			continue;
  		}
  		else
  			break;
  	}
  	if (pfn < end_pfn)
  		return 0;
  	return 1;
  }
  
  int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
  			bool skip_hwpoisoned_pages)
  {
  	unsigned long pfn, flags;
  	struct page *page;
  	struct zone *zone;
  	int ret;
  
  	/*
  	 * Note: pageblock_nr_pages != MAX_ORDER. Then, chunks of free pages
  	 * are not aligned to pageblock_nr_pages.
  	 * Then we just check migratetype first.
  	 */
  	for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
  		page = __first_valid_page(pfn, pageblock_nr_pages);
  		if (page && get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
  			break;
  	}
  	page = __first_valid_page(start_pfn, end_pfn - start_pfn);
  	if ((pfn < end_pfn) || !page)
  		return -EBUSY;
  	/* Check all pages are free or marked as ISOLATED */
  	zone = page_zone(page);
  	spin_lock_irqsave(&zone->lock, flags);
  	ret = __test_page_isolated_in_pageblock(start_pfn, end_pfn,
  						skip_hwpoisoned_pages);
  	spin_unlock_irqrestore(&zone->lock, flags);
  	return ret ? 0 : -EBUSY;
  }
  
  struct page *alloc_migrate_target(struct page *page, unsigned long private,
  				  int **resultp)
  {
  	gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;
  
  	/*
  	 * TODO: allocate a destination hugepage from a nearest neighbor node,
  	 * accordance with memory policy of the user process if possible. For
  	 * now as a simple work-around, we use the next node for destination.
  	 */
  	if (PageHuge(page)) {
  		nodemask_t src = nodemask_of_node(page_to_nid(page));
  		nodemask_t dst;
  		nodes_complement(dst, src);
  		return alloc_huge_page_node(page_hstate(compound_head(page)),
  					    next_node(page_to_nid(page), dst));
  	}
  
  	if (PageHighMem(page))
  		gfp_mask |= __GFP_HIGHMEM;
  
  	return alloc_page(gfp_mask);
  }