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Commit 85aa125f authored by Michal Nazarewicz's avatar Michal Nazarewicz Committed by Marek Szyprowski
Browse files

mm: compaction: introduce isolate_freepages_range() 



This commit introduces isolate_freepages_range() function which
generalises isolate_freepages_block() so that it can be used on
arbitrary PFN ranges.

isolate_freepages_block() is left with only minor changes.

Signed-off-by: default avatarMichal Nazarewicz <mina86@mina86.com>
Signed-off-by: default avatarMarek Szyprowski <m.szyprowski@samsung.com>
Acked-by: default avatarMel Gorman <mel@csn.ul.ie>
Reviewed-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Tested-by: default avatarRob Clark <rob.clark@linaro.org>
Tested-by: default avatarOhad Ben-Cohen <ohad@wizery.com>
Tested-by: default avatarBenjamin Gaignard <benjamin.gaignard@linaro.org>
Tested-by: default avatarRobert Nelson <robertcnelson@gmail.com>
Tested-by: default avatarBarry Song <Baohua.Song@csr.com>
parent 03d44192

mm/compaction.c

+93 −18
Original line number Diff line number Diff line
@@ -54,24 +54,20 @@ static unsigned long release_freepages(struct list_head *freelist) 
	return count;

}



/* Isolate free pages onto a private freelist. Must hold zone->lock */

static unsigned long isolate_freepages_block(struct zone *zone,

				unsigned long blockpfn,

				struct list_head *freelist)

/*

 * Isolate free pages onto a private freelist. Caller must hold zone->lock.

 * If @strict is true, will abort returning 0 on any invalid PFNs or non-free

 * pages inside of the pageblock (even though it may still end up isolating

 * some pages).

 */

static unsigned long isolate_freepages_block(unsigned long blockpfn,

				unsigned long end_pfn,

				struct list_head *freelist,

				bool strict)

{

	unsigned long zone_end_pfn, end_pfn;

	int nr_scanned = 0, total_isolated = 0;

	struct page *cursor;



	/* Get the last PFN we should scan for free pages at */

	zone_end_pfn = zone->zone_start_pfn + zone->spanned_pages;

	end_pfn = min(blockpfn + pageblock_nr_pages, zone_end_pfn);



	/* Find the first usable PFN in the block to initialse page cursor */

	for (; blockpfn < end_pfn; blockpfn++) {

		if (pfn_valid_within(blockpfn))

			break;

	}

	cursor = pfn_to_page(blockpfn);



	/* Isolate free pages. This assumes the block is valid */
@@ -79,15 +75,23 @@ static unsigned long isolate_freepages_block(struct zone *zone, 
		int isolated, i;

		struct page *page = cursor;



		if (!pfn_valid_within(blockpfn))

		if (!pfn_valid_within(blockpfn)) {

			if (strict)

				return 0;

			continue;

		}

		nr_scanned++;



		if (!PageBuddy(page))

		if (!PageBuddy(page)) {

			if (strict)

				return 0;

			continue;

		}



		/* Found a free page, break it into order-0 pages */

		isolated = split_free_page(page);

		if (!isolated && strict)

			return 0;

		total_isolated += isolated;

		for (i = 0; i < isolated; i++) {

			list_add(&page->lru, freelist);
@@ -105,6 +109,73 @@ static unsigned long isolate_freepages_block(struct zone *zone, 
	return total_isolated;

}



/**

 * isolate_freepages_range() - isolate free pages.

 * @start_pfn: The first PFN to start isolating.

 * @end_pfn:   The one-past-last PFN.

 *

 * Non-free pages, invalid PFNs, or zone boundaries within the

 * [start_pfn, end_pfn) range are considered errors, cause function to

 * undo its actions and return zero.

 *

 * Otherwise, function returns one-past-the-last PFN of isolated page

 * (which may be greater then end_pfn if end fell in a middle of

 * a free page).

 */

static unsigned long

isolate_freepages_range(unsigned long start_pfn, unsigned long end_pfn)

{

	unsigned long isolated, pfn, block_end_pfn, flags;

	struct zone *zone = NULL;

	LIST_HEAD(freelist);



	if (pfn_valid(start_pfn))

		zone = page_zone(pfn_to_page(start_pfn));



	for (pfn = start_pfn; pfn < end_pfn; pfn += isolated) {

		if (!pfn_valid(pfn) || zone != page_zone(pfn_to_page(pfn)))

			break;



		/*

		 * On subsequent iterations ALIGN() is actually not needed,

		 * but we keep it that we not to complicate the code.

		 */

		block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);

		block_end_pfn = min(block_end_pfn, end_pfn);



		spin_lock_irqsave(&zone->lock, flags);

		isolated = isolate_freepages_block(pfn, block_end_pfn,

						   &freelist, true);

		spin_unlock_irqrestore(&zone->lock, flags);



		/*

		 * In strict mode, isolate_freepages_block() returns 0 if

		 * there are any holes in the block (ie. invalid PFNs or

		 * non-free pages).

		 */

		if (!isolated)

			break;



		/*

		 * If we managed to isolate pages, it is always (1 << n) *

		 * pageblock_nr_pages for some non-negative n.  (Max order

		 * page may span two pageblocks).

		 */

	}



	/* split_free_page does not map the pages */

	map_pages(&freelist);



	if (pfn < end_pfn) {

		/* Loop terminated early, cleanup. */

		release_freepages(&freelist);

		return 0;

	}



	/* We don't use freelists for anything. */

	return pfn;

}



/* Returns true if the page is within a block suitable for migration to */

static bool suitable_migration_target(struct page *page)

{
@@ -145,7 +216,7 @@ static void isolate_freepages(struct zone *zone, 
				struct compact_control *cc)

{

	struct page *page;

	unsigned long high_pfn, low_pfn, pfn;

	unsigned long high_pfn, low_pfn, pfn, zone_end_pfn, end_pfn;

	unsigned long flags;

	int nr_freepages = cc->nr_freepages;

	struct list_head *freelist = &cc->freepages;
@@ -165,6 +236,8 @@ static void isolate_freepages(struct zone *zone, 
	 */

	high_pfn = min(low_pfn, pfn);



	zone_end_pfn = zone->zone_start_pfn + zone->spanned_pages;



	/*

	 * Isolate free pages until enough are available to migrate the

	 * pages on cc->migratepages. We stop searching if the migrate
@@ -201,7 +274,9 @@ static void isolate_freepages(struct zone *zone, 
		isolated = 0;

		spin_lock_irqsave(&zone->lock, flags);

		if (suitable_migration_target(page)) {

			isolated = isolate_freepages_block(zone, pfn, freelist);

			end_pfn = min(pfn + pageblock_nr_pages, zone_end_pfn);

			isolated = isolate_freepages_block(pfn, end_pfn,

							   freelist, false);

			nr_freepages += isolated;

		}

		spin_unlock_irqrestore(&zone->lock, flags);