---

yaml
---
r: 332437
b: refs/heads/master
c: f40d1e4
h: refs/heads/master
i:
  332435: 398b79a
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 2a1402aa044b55c2d30ab0ed9405693ef06fb07c
+refs/heads/master: f40d1e42bb988d2a26e8e111ea4c4c7bac819b7e

trunk/mm/compaction.c

@@ -93,6 +93,27 @@ static inline bool compact_trylock_irqsave(spinlock_t *lock,
 	return compact_checklock_irqsave(lock, flags, false, cc);
 }
 
+/* Returns true if the page is within a block suitable for migration to */
+static bool suitable_migration_target(struct page *page)
+{
+	int migratetype = get_pageblock_migratetype(page);
+
+	/* Don't interfere with memory hot-remove or the min_free_kbytes blocks */
+	if (migratetype == MIGRATE_ISOLATE || migratetype == MIGRATE_RESERVE)
+		return false;
+
+	/* If the page is a large free page, then allow migration */
+	if (PageBuddy(page) && page_order(page) >= pageblock_order)
+		return true;
+
+	/* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
+	if (migrate_async_suitable(migratetype))
+		return true;
+
+	/* Otherwise skip the block */
+	return false;
+}
+
 static void compact_capture_page(struct compact_control *cc)
 {
 	unsigned long flags;
@@ -153,38 +174,56 @@ static void compact_capture_page(struct compact_control *cc)
  * pages inside of the pageblock (even though it may still end up isolating
  * some pages).
  */
-static unsigned long isolate_freepages_block(unsigned long blockpfn,
+static unsigned long isolate_freepages_block(struct compact_control *cc,
+				unsigned long blockpfn,
 				unsigned long end_pfn,
 				struct list_head *freelist,
 				bool strict)
 {
 	int nr_scanned = 0, total_isolated = 0;
 	struct page *cursor;
+	unsigned long nr_strict_required = end_pfn - blockpfn;
+	unsigned long flags;
+	bool locked = false;
 
 	cursor = pfn_to_page(blockpfn);
 
-	/* Isolate free pages. This assumes the block is valid */
+	/* Isolate free pages. */
 	for (; blockpfn < end_pfn; blockpfn++, cursor++) {
 		int isolated, i;
 		struct page *page = cursor;
 
-		if (!pfn_valid_within(blockpfn)) {
-			if (strict)
-				return 0;
-			continue;
-		}
 		nr_scanned++;
+		if (!pfn_valid_within(blockpfn))
+			continue;
+		if (!PageBuddy(page))
+			continue;
+
+		/*
+		 * The zone lock must be held to isolate freepages.
+		 * Unfortunately this is a very coarse lock and can be
+		 * heavily contended if there are parallel allocations
+		 * or parallel compactions. For async compaction do not
+		 * spin on the lock and we acquire the lock as late as
+		 * possible.
+		 */
+		locked = compact_checklock_irqsave(&cc->zone->lock, &flags,
+								locked, cc);
+		if (!locked)
+			break;
+
+		/* Recheck this is a suitable migration target under lock */
+		if (!strict && !suitable_migration_target(page))
+			break;
 
-		if (!PageBuddy(page)) {
-			if (strict)
-				return 0;
+		/* Recheck this is a buddy page under lock */
+		if (!PageBuddy(page))
 			continue;
-		}
 
 		/* Found a free page, break it into order-0 pages */
 		isolated = split_free_page(page);
 		if (!isolated && strict)
-			return 0;
+			break;
 		total_isolated += isolated;
 		for (i = 0; i < isolated; i++) {
 			list_add(&page->lru, freelist);
@@ -199,6 +238,18 @@ static unsigned long isolate_freepages_block(unsigned long blockpfn,
 	}
 
 	trace_mm_compaction_isolate_freepages(nr_scanned, total_isolated);
+
+	/*
+	 * If strict isolation is requested by CMA then check that all the
+	 * pages requested were isolated. If there were any failures, 0 is
+	 * returned and CMA will fail.
+	 */
+	if (strict && nr_strict_required != total_isolated)
+		total_isolated = 0;
+
+	if (locked)
+		spin_unlock_irqrestore(&cc->zone->lock, flags);
+
 	return total_isolated;
 }
 
@@ -218,12 +269,17 @@ static unsigned long isolate_freepages_block(unsigned long blockpfn,
 unsigned long
 isolate_freepages_range(unsigned long start_pfn, unsigned long end_pfn)
 {
-	unsigned long isolated, pfn, block_end_pfn, flags;
+	unsigned long isolated, pfn, block_end_pfn;
 	struct zone *zone = NULL;
 	LIST_HEAD(freelist);
 
+	/* cc needed for isolate_freepages_block to acquire zone->lock */
+	struct compact_control cc = {
+		.sync = true,
+	};
+
 	if (pfn_valid(start_pfn))
-		zone = page_zone(pfn_to_page(start_pfn));
+		cc.zone = 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)))
@@ -236,10 +292,8 @@ isolate_freepages_range(unsigned long start_pfn, unsigned long end_pfn)
 		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,
+		isolated = isolate_freepages_block(&cc, pfn, block_end_pfn,
 						   &freelist, true);
-		spin_unlock_irqrestore(&zone->lock, flags);
 
 		/*
 		 * In strict mode, isolate_freepages_block() returns 0 if
@@ -483,29 +537,6 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
 
 #endif /* CONFIG_COMPACTION || CONFIG_CMA */
 #ifdef CONFIG_COMPACTION
-
-/* Returns true if the page is within a block suitable for migration to */
-static bool suitable_migration_target(struct page *page)
-{
-
-	int migratetype = get_pageblock_migratetype(page);
-
-	/* Don't interfere with memory hot-remove or the min_free_kbytes blocks */
-	if (migratetype == MIGRATE_ISOLATE || migratetype == MIGRATE_RESERVE)
-		return false;
-
-	/* If the page is a large free page, then allow migration */
-	if (PageBuddy(page) && page_order(page) >= pageblock_order)
-		return true;
-
-	/* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
-	if (migrate_async_suitable(migratetype))
-		return true;
-
-	/* Otherwise skip the block */
-	return false;
-}
-
 /*
  * Returns the start pfn of the last page block in a zone.  This is the starting
  * point for full compaction of a zone.  Compaction searches for free pages from
@@ -529,7 +560,6 @@ static void isolate_freepages(struct zone *zone,
 {
 	struct page *page;
 	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;
 
@@ -577,30 +607,12 @@ static void isolate_freepages(struct zone *zone,
 		if (!suitable_migration_target(page))
 			continue;
 
-		/*
-		 * Found a block suitable for isolating free pages from. Now
-		 * we disabled interrupts, double check things are ok and
-		 * isolate the pages. This is to minimise the time IRQs
-		 * are disabled
-		 */
+		/* Found a block suitable for isolating free pages from */
 		isolated = 0;
-
-		/*
-		 * The zone lock must be held to isolate freepages. This
-		 * unfortunately this is a very coarse lock and can be
-		 * heavily contended if there are parallel allocations
-		 * or parallel compactions. For async compaction do not
-		 * spin on the lock
-		 */
-		if (!compact_trylock_irqsave(&zone->lock, &flags, cc))
-			break;
-		if (suitable_migration_target(page)) {
-			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);
+		end_pfn = min(pfn + pageblock_nr_pages, zone_end_pfn);
+		isolated = isolate_freepages_block(cc, pfn, end_pfn,
+						   freelist, false);
+		nr_freepages += isolated;
 
 		/*
 		 * Record the highest PFN we isolated pages from. When next