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Commit 7d348b9e authored by Joonsoo Kim's avatar Joonsoo Kim Committed by Linus Torvalds
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mm/compaction: disallow high-order page for migration target 



Purpose of compaction is to get a high order page.  Currently, if we
find high-order page while searching migration target page, we break it
to order-0 pages and use them as migration target.  It is contrary to
purpose of compaction, so disallow high-order page to be used for
migration target.

Additionally, clean-up logic in suitable_migration_target() to simplify
the code.  There is no functional changes from this clean-up.

Signed-off-by: default avatarJoonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 70ef57e6

mm/compaction.c

+3 −12
Original line number Diff line number Diff line
@@ -217,21 +217,12 @@ static inline bool compact_trylock_irqsave(spinlock_t *lock, 
/* 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_RESERVE)

		return false;



	if (is_migrate_isolate(migratetype))

		return false;



	/* If the page is a large free page, then allow migration */

	/* If the page is a large free page, then disallow migration */

	if (PageBuddy(page) && page_order(page) >= pageblock_order)

		return true;

		return false;



	/* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */

	if (migrate_async_suitable(migratetype))

	if (migrate_async_suitable(get_pageblock_migratetype(page)))

		return true;



	/* Otherwise skip the block */