mm, compaction: change COMPACT_ constants into enum

Compaction code is doing weird dances between COMPACT_FOO -> int ->
unsigned long

But there doesn't seem to be any reason for that.  All functions which
return/use one of those constants are not expecting any other value so it
really makes sense to define an enum for them and make it clear that no
other values are expected.

This is a pure cleanup and shouldn't introduce any functional changes.

Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 27 insertions, 18 deletions

diff --git a/include/linux/compaction.h b/include/linux/compaction.h
index 242b660f64e6..706cbf00e919 100644
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -2,21 +2,29 @@
 #define _LINUX_COMPACTION_H
 
 /* Return values for compact_zone() and try_to_compact_pages() */
-/* compaction didn't start as it was deferred due to past failures */
-#define COMPACT_DEFERRED	0
-/* compaction didn't start as it was not possible or direct reclaim was more suitable */
-#define COMPACT_SKIPPED		1
-/* compaction should continue to another pageblock */
-#define COMPACT_CONTINUE	2
-/* direct compaction partially compacted a zone and there are suitable pages */
-#define COMPACT_PARTIAL		3
-/* The full zone was compacted */
-#define COMPACT_COMPLETE	4
-/* For more detailed tracepoint output */
-#define COMPACT_NO_SUITABLE_PAGE	5
-#define COMPACT_NOT_SUITABLE_ZONE	6
-#define COMPACT_CONTENDED		7
 /* When adding new states, please adjust include/trace/events/compaction.h */
+enum compact_result {
+	/* compaction didn't start as it was deferred due to past failures */
+	COMPACT_DEFERRED,
+	/*
+	 * compaction didn't start as it was not possible or direct reclaim
+	 * was more suitable
+	 */
+	COMPACT_SKIPPED,
+	/* compaction should continue to another pageblock */
+	COMPACT_CONTINUE,
+	/*
+	 * direct compaction partially compacted a zone and there are suitable
+	 * pages
+	 */
+	COMPACT_PARTIAL,
+	/* The full zone was compacted */
+	COMPACT_COMPLETE,
+	/* For more detailed tracepoint output */
+	COMPACT_NO_SUITABLE_PAGE,
+	COMPACT_NOT_SUITABLE_ZONE,
+	COMPACT_CONTENDED,
+};
 
 /* Used to signal whether compaction detected need_sched() or lock contention */
 /* No contention detected */
@@ -38,12 +46,13 @@ extern int sysctl_extfrag_handler(struct ctl_table *table, int write,
 extern int sysctl_compact_unevictable_allowed;
 
 extern int fragmentation_index(struct zone *zone, unsigned int order);
-extern unsigned long try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
+extern enum compact_result try_to_compact_pages(gfp_t gfp_mask,
+			unsigned int order,
 		unsigned int alloc_flags, const struct alloc_context *ac,
 		enum migrate_mode mode, int *contended);
 extern void compact_pgdat(pg_data_t *pgdat, int order);
 extern void reset_isolation_suitable(pg_data_t *pgdat);
-extern unsigned long compaction_suitable(struct zone *zone, int order,
+extern enum compact_result compaction_suitable(struct zone *zone, int order,
 		unsigned int alloc_flags, int classzone_idx);
 
 extern void defer_compaction(struct zone *zone, int order);
@@ -57,7 +66,7 @@ extern void kcompactd_stop(int nid);
 extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx);
 
 #else
-static inline unsigned long try_to_compact_pages(gfp_t gfp_mask,
+static inline enum compact_result try_to_compact_pages(gfp_t gfp_mask,
 			unsigned int order, int alloc_flags,
 			const struct alloc_context *ac,
 			enum migrate_mode mode, int *contended)
@@ -73,7 +82,7 @@ static inline void reset_isolation_suitable(pg_data_t *pgdat)
 {
 }
 
-static inline unsigned long compaction_suitable(struct zone *zone, int order,
+static inline enum compact_result compaction_suitable(struct zone *zone, int order,
 					int alloc_flags, int classzone_idx)
 {
 	return COMPACT_SKIPPED;