mm: use self-explanatory macros rather than "2"

Signed-off-by: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Alex Shi <alex.shi@linux.alibaba.com>
Link: http://lkml.kernel.org/r/20200831175042.3527153-2-yuzhao@google.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/mmzone.h

@@ -266,6 +266,8 @@ static inline bool is_active_lru(enum lru_list lru)
 	return (lru == LRU_ACTIVE_ANON || lru == LRU_ACTIVE_FILE);
 }
 
+#define ANON_AND_FILE 2
+
 enum lruvec_flags {
 	LRUVEC_CONGESTED,		/* lruvec has many dirty pages
 					 * backed by a congested BDI
@@ -283,8 +285,8 @@ struct lruvec {
 	unsigned long			file_cost;
 	/* Non-resident age, driven by LRU movement */
 	atomic_long_t			nonresident_age;
-	/* Refaults at the time of last reclaim cycle, anon=0, file=1 */
-	unsigned long			refaults[2];
+	/* Refaults at the time of last reclaim cycle */
+	unsigned long			refaults[ANON_AND_FILE];
 	/* Various lruvec state flags (enum lruvec_flags) */
 	unsigned long			flags;
 #ifdef CONFIG_MEMCG
@@ -441,6 +443,8 @@ enum zone_type {
 
 #ifndef __GENERATING_BOUNDS_H
 
+#define ASYNC_AND_SYNC 2
+
 struct zone {
 	/* Read-mostly fields */
 
@@ -560,8 +564,8 @@ struct zone {
 #if defined CONFIG_COMPACTION || defined CONFIG_CMA
 	/* pfn where compaction free scanner should start */
 	unsigned long		compact_cached_free_pfn;
-	/* pfn where async and sync compaction migration scanner should start */
-	unsigned long		compact_cached_migrate_pfn[2];
+	/* pfn where compaction migration scanner should start */
+	unsigned long		compact_cached_migrate_pfn[ASYNC_AND_SYNC];
 	unsigned long		compact_init_migrate_pfn;
 	unsigned long		compact_init_free_pfn;
 #endif

include/linux/vmstat.h

@@ -28,7 +28,7 @@ struct reclaim_stat {
 	unsigned nr_writeback;
 	unsigned nr_immediate;
 	unsigned nr_pageout;
-	unsigned nr_activate[2];
+	unsigned nr_activate[ANON_AND_FILE];
 	unsigned nr_ref_keep;
 	unsigned nr_unmap_fail;
 	unsigned nr_lazyfree_fail;

mm/vmscan.c

@@ -2239,7 +2239,7 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
 	unsigned long anon_cost, file_cost, total_cost;
 	int swappiness = mem_cgroup_swappiness(memcg);
-	u64 fraction[2];
+	u64 fraction[ANON_AND_FILE];
 	u64 denominator = 0;	/* gcc */
 	enum scan_balance scan_balance;
 	unsigned long ap, fp;