// SPDX-License-Identifier: GPL-2.0

  /*
   * 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 <linux/page_owner.h>

  #include <linux/migrate.h>

  #include "internal.h"

  #define CREATE_TRACE_POINTS
  #include <trace/events/page_isolation.h>

  static int set_migratetype_isolate(struct page *page, int migratetype, int isol_flags)

  {
  	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);

  	/*
  	 * We assume the caller intended to SET migrate type to isolate.
  	 * If it is already set, then someone else must have raced and
  	 * set it before us.  Return -EBUSY
  	 */
  	if (is_migrate_isolate_page(page))
  		goto out;

  	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, migratetype,
  				 isol_flags))

  		ret = 0;
  
  	/*

  	 * immobile means "not-on-lru" pages. If immobile is larger than

  	 * removable-by-driver pages reported by notifier, we'll fail.
  	 */
  
  out:
  	if (!ret) {

  		unsigned long nr_pages;

  		int mt = get_pageblock_migratetype(page);

  		set_pageblock_migratetype(page, MIGRATE_ISOLATE);

  		zone->nr_isolate_pageblock++;

  		nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE,
  									NULL);

  		__mod_zone_freepage_state(zone, -nr_pages, mt);

  	}
  
  	spin_unlock_irqrestore(&zone->lock, flags);
  	if (!ret)

  		drain_all_pages(zone);

  	return ret;
  }

  static void unset_migratetype_isolate(struct page *page, unsigned migratetype)

  {
  	struct zone *zone;

  	unsigned long flags, nr_pages;

  	bool isolated_page = false;

  	unsigned int order;

  	unsigned long pfn, buddy_pfn;

  	struct page *buddy;

  	zone = page_zone(page);
  	spin_lock_irqsave(&zone->lock, flags);

  	if (!is_migrate_isolate_page(page))

  		goto out;

  
  	/*
  	 * Because freepage with more than pageblock_order on isolated
  	 * pageblock is restricted to merge due to freepage counting problem,
  	 * it is possible that there is free buddy page.
  	 * move_freepages_block() doesn't care of merge so we need other
  	 * approach in order to merge them. Isolation and free will make
  	 * these pages to be merged.
  	 */
  	if (PageBuddy(page)) {
  		order = page_order(page);
  		if (order >= pageblock_order) {

  			pfn = page_to_pfn(page);
  			buddy_pfn = __find_buddy_pfn(pfn, order);
  			buddy = page + (buddy_pfn - pfn);

  			if (pfn_valid_within(buddy_pfn) &&

  			    !is_migrate_isolate_page(buddy)) {

  				__isolate_free_page(page, order);

  				isolated_page = true;

  			}
  		}
  	}
  
  	/*
  	 * If we isolate freepage with more than pageblock_order, there
  	 * should be no freepage in the range, so we could avoid costly
  	 * pageblock scanning for freepage moving.
  	 */
  	if (!isolated_page) {

  		nr_pages = move_freepages_block(zone, page, migratetype, NULL);

  		__mod_zone_freepage_state(zone, nr_pages, migratetype);
  	}

  	set_pageblock_migratetype(page, migratetype);

  	zone->nr_isolate_pageblock--;

  out:
  	spin_unlock_irqrestore(&zone->lock, flags);

  	if (isolated_page) {

  		post_alloc_hook(page, order, __GFP_MOVABLE);

  		__free_pages(page, order);

  	}

  }

  static inline struct page *
  __first_valid_page(unsigned long pfn, unsigned long nr_pages)
  {
  	int i;

  
  	for (i = 0; i < nr_pages; i++) {
  		struct page *page;

  		page = pfn_to_online_page(pfn + i);
  		if (!page)
  			continue;
  		return page;
  	}
  	return NULL;

  }

  /**
   * 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.
   *			start_pfn/end_pfn must be aligned to pageblock_order.
   * @migratetype:	Migrate type to set in error recovery.
   * @flags:		The following flags are allowed (they can be combined in
   *			a bit mask)
   *			SKIP_HWPOISON - ignore hwpoison pages
   *			REPORT_FAILURE - report details about the failure to
   *			isolate the range

   *
   * 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. If specified range includes migrate types
   * other than MOVABLE or CMA, this will fail with -EBUSY. For isolating all
   * pages in the range finally, the caller have to free all pages in the range.
   * test_page_isolated() can be used for test it.

   *
   * There is no high level synchronization mechanism that prevents two threads

   * from trying to isolate overlapping ranges. If this happens, one thread

   * will notice pageblocks in the overlapping range already set to isolate.
   * This happens in set_migratetype_isolate, and set_migratetype_isolate

   * returns an error. We then clean up by restoring the migration type on
   * pageblocks we may have modified and return -EBUSY to caller. This

   * prevents two threads from simultaneously working on overlapping ranges.

   *

   * Please note that there is no strong synchronization with the page allocator
   * either. Pages might be freed while their page blocks are marked ISOLATED.
   * In some cases pages might still end up on pcp lists and that would allow
   * for their allocation even when they are in fact isolated already. Depending
   * on how strong of a guarantee the caller needs drain_all_pages might be needed
   * (e.g. __offline_pages will need to call it after check for isolated range for
   * a next retry).
   *

   * Return: the number of isolated pageblocks 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, int flags)

  {
  	unsigned long pfn;
  	unsigned long undo_pfn;
  	struct page *page;

  	int nr_isolate_pageblock = 0;

  	BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
  	BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));

  
  	for (pfn = start_pfn;
  	     pfn < end_pfn;
  	     pfn += pageblock_nr_pages) {
  		page = __first_valid_page(pfn, pageblock_nr_pages);

  		if (page) {
  			if (set_migratetype_isolate(page, migratetype, flags)) {
  				undo_pfn = pfn;
  				goto undo;
  			}
  			nr_isolate_pageblock++;

  		}
  	}

  	return nr_isolate_pageblock;

  undo:
  	for (pfn = start_pfn;

  	     pfn < undo_pfn;

  	     pfn += pageblock_nr_pages) {
  		struct page *page = pfn_to_online_page(pfn);
  		if (!page)
  			continue;
  		unset_migratetype_isolate(page, migratetype);
  	}

  
  	return -EBUSY;
  }
  
  /*
   * Make isolated pages available again.
   */

  void undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,

  			    unsigned migratetype)

  {
  	unsigned long pfn;
  	struct page *page;

  
  	BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
  	BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));

  	for (pfn = start_pfn;
  	     pfn < end_pfn;
  	     pfn += pageblock_nr_pages) {
  		page = __first_valid_page(pfn, pageblock_nr_pages);

  		if (!page || !is_migrate_isolate_page(page))

  			continue;

  		unset_migratetype_isolate(page, migratetype);

  	}

  }
  /*
   * 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 the last tested pfn.

   */

  static unsigned long

  __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 the page is on a free list, it has to be on
  			 * the correct MIGRATE_ISOLATE freelist. There is no
  			 * simple way to verify that as VM_BUG_ON(), though.

  			 */

  			pfn += 1 << page_order(page);

  		else if (skip_hwpoisoned_pages && PageHWPoison(page))
  			/* A HWPoisoned page cannot be also PageBuddy */

  			pfn++;

  		else
  			break;
  	}

  
  	return pfn;

  }

  /* Caller should ensure that requested range is in a single zone */

  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;

  	/*

  	 * 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 && !is_migrate_isolate_page(page))

  			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);

  	pfn = __test_page_isolated_in_pageblock(start_pfn, end_pfn,

  						skip_hwpoisoned_pages);

  	spin_unlock_irqrestore(&zone->lock, flags);

  	trace_test_pages_isolated(start_pfn, end_pfn, pfn);

  	return pfn < end_pfn ? -EBUSY : 0;

  }

  struct page *alloc_migrate_target(struct page *page, unsigned long private)

  {

  	return new_page_nodemask(page, numa_node_id(), &node_states[N_MEMORY]);

  }