mm: compaction: capture a suitable high-order page immediately when it is made available

While compaction is migrating pages to free up large contiguous blocks
for allocation it races with other allocation requests that may steal
these blocks or break them up.  This patch alters direct compaction to
capture a suitable free page as soon as it becomes available to reduce
this race.  It uses similar logic to split_free_page() to ensure that
watermarks are still obeyed.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 3 insertions, 2 deletions

diff --git a/include/linux/compaction.h b/include/linux/compaction.h
index ef658147e4e8..0e38a1deeb23 100644
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -22,7 +22,7 @@ extern int sysctl_extfrag_handler(struct ctl_table *table, int write,
 extern int fragmentation_index(struct zone *zone, unsigned int order);
 extern unsigned long try_to_compact_pages(struct zonelist *zonelist,
                         int order, gfp_t gfp_mask, nodemask_t *mask,
-                        bool sync, bool *contended);
+                        bool sync, bool *contended, struct page **page);
 extern int compact_pgdat(pg_data_t *pgdat, int order);
 extern unsigned long compaction_suitable(struct zone *zone, int order);
 
@@ -64,7 +64,7 @@ static inline bool compaction_deferred(struct zone *zone, int order)
 #else
 static inline unsigned long try_to_compact_pages(struct zonelist *zonelist,
                         int order, gfp_t gfp_mask, nodemask_t *nodemask,
-                        bool sync, bool *contended)
+                        bool sync, bool *contended, struct page **page)
 {
         return COMPACT_CONTINUE;
 }
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0514fe9d3c84..5ddb11b2b4bb 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -442,6 +442,7 @@ void put_pages_list(struct list_head *pages);
 
 void split_page(struct page *page, unsigned int order);
 int split_free_page(struct page *page);
+int capture_free_page(struct page *page, int alloc_order, int migratetype);
 
 /*
  * Compound pages have a destructor function.  Provide a