mm/page_isolation.c - linux - Git at Google

 /*
  * 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"

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

 static 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);
 		zone->nr_isolate_pageblock++;
 		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(zone);
 	return ret;
 }

 static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
 {
 	struct zone *zone;
 	unsigned long flags, nr_pages;
 	struct page *isolated_page = NULL;
 	unsigned int order;
 	unsigned long page_idx, buddy_idx;
 	struct page *buddy;

 	zone = page_zone(page);
 	spin_lock_irqsave(&zone->lock, flags);
 	if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
 		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) {
 			page_idx = page_to_pfn(page) & ((1 << MAX_ORDER) - 1);
 			buddy_idx = __find_buddy_index(page_idx, order);
 			buddy = page + (buddy_idx - page_idx);

 			if (pfn_valid_within(page_to_pfn(buddy)) &&
 			    !is_migrate_isolate_page(buddy)) {
 				__isolate_free_page(page, order);
 				kernel_map_pages(page, (1 << order), 1);
 				set_page_refcounted(page);
 				isolated_page = page;
 			}
 		}
 	}

 	/*
 	 * 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);
 		__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)
 		__free_pages(isolated_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++)
 		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 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;
 }

 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 && 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);
 	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,
 				  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);
 }
	/*
	* 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"

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

	static 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);
	zone->nr_isolate_pageblock++;
	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(zone);
	return ret;
	}

	static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
	{
	struct zone *zone;
	unsigned long flags, nr_pages;
	struct page *isolated_page = NULL;
	unsigned int order;
	unsigned long page_idx, buddy_idx;
	struct page *buddy;

	zone = page_zone(page);
	spin_lock_irqsave(&zone->lock, flags);
	if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
	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) {
	page_idx = page_to_pfn(page) & ((1 << MAX_ORDER) - 1);
	buddy_idx = __find_buddy_index(page_idx, order);
	buddy = page + (buddy_idx - page_idx);

	if (pfn_valid_within(page_to_pfn(buddy)) &&
	!is_migrate_isolate_page(buddy)) {
	__isolate_free_page(page, order);
	kernel_map_pages(page, (1 << order), 1);
	set_page_refcounted(page);
	isolated_page = page;
	}
	}
	}

	/*
	* 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);
	__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)
	__free_pages(isolated_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++)
	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 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;
	}

	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 && 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);
	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,
	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);
	}