memory unplug: page isolation

Implement generic chunk-of-pages isolation method by using page grouping ops.

This patch add MIGRATE_ISOLATE to MIGRATE_TYPES. By this
 - MIGRATE_TYPES increases.
 - bitmap for migratetype is enlarged.

pages of MIGRATE_ISOLATE migratetype will not be allocated even if it is free.
By this, you can isolated *freed* pages from users. How-to-free pages is not
a purpose of this patch. You may use reclaim and migrate codes to free pages.

If start_isolate_page_range(start,end) is called,
 - migratetype of the range turns to be MIGRATE_ISOLATE  if
   its type is MIGRATE_MOVABLE. (*) this check can be updated if other
   memory reclaiming works make progress.
 - MIGRATE_ISOLATE is not on migratetype fallback list.
 - All free pages and will-be-freed pages are isolated.
To check all pages in the range are isolated or not,  use test_pages_isolated(),
To cancel isolation, use undo_isolate_page_range().

Changes V6 -> V7
 - removed unnecessary #ifdef

There are HOLES_IN_ZONE handling codes...I'm glad if we can remove them..

Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 44 insertions, 0 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 71ced519c31..a44715e8205 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -41,6 +41,7 @@
 #include <linux/pfn.h>
 #include <linux/backing-dev.h>
 #include <linux/fault-inject.h>
+#include <linux/page-isolation.h>
 
 #include <asm/tlbflush.h>
 #include <asm/div64.h>
@@ -4433,3 +4434,46 @@ void set_pageblock_flags_group(struct page *page, unsigned long flags,
 		else
 			__clear_bit(bitidx + start_bitidx, bitmap);
 }
+
+/*
+ * This is designed as sub function...plz see page_isolation.c also.
+ * set/clear page block's type to be ISOLATE.
+ * page allocater never alloc memory from ISOLATE block.
+ */
+
+int set_migratetype_isolate(struct page *page)
+{
+	struct zone *zone;
+	unsigned long flags;
+	int ret = -EBUSY;
+
+	zone = page_zone(page);
+	spin_lock_irqsave(&zone->lock, flags);
+	/*
+	 * In future, more migrate types will be able to be isolation target.
+	 */
+	if (get_pageblock_migratetype(page) != MIGRATE_MOVABLE)
+		goto out;
+	set_pageblock_migratetype(page, MIGRATE_ISOLATE);
+	move_freepages_block(zone, page, MIGRATE_ISOLATE);
+	ret = 0;
+out:
+	spin_unlock_irqrestore(&zone->lock, flags);
+	if (!ret)
+		drain_all_local_pages();
+	return ret;
+}
+
+void unset_migratetype_isolate(struct page *page)
+{
+	struct zone *zone;
+	unsigned long flags;
+	zone = page_zone(page);
+	spin_lock_irqsave(&zone->lock, flags);
+	if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
+		goto out;
+	set_pageblock_migratetype(page, MIGRATE_MOVABLE);
+	move_freepages_block(zone, page, MIGRATE_MOVABLE);
+out:
+	spin_unlock_irqrestore(&zone->lock, flags);
+}