Commit 7d348b9e authored by Joonsoo Kim's avatar Joonsoo Kim Committed by Linus Torvalds

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 <>
Acked-by: default avatarVlastimil Babka <>
Cc: Mel Gorman <>
Cc: Rik van Riel <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 70ef57e6
......@@ -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 */
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