mm/vmscan: define macros for refaults in struct lruvec

The magic number 0 and 1 are used in several places in vmscan.c.
Define macros for them to improve code readability.

Link: https://lkml.kernel.org/r/20220808005644.1721066-1-yang.yang29@zte.com.cnSigned-off-by: Yang Yang <yang.yang29@zte.com.cn>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/mmzone.h

@@ -306,6 +306,8 @@ static inline bool is_active_lru(enum lru_list lru)
 	return (lru == LRU_ACTIVE_ANON || lru == LRU_ACTIVE_FILE);
 }
 
+#define WORKINGSET_ANON 0
+#define WORKINGSET_FILE 1
 #define ANON_AND_FILE 2
 
 enum lruvec_flags {

mm/vmscan.c

@@ -3230,7 +3230,7 @@ static void shrink_node(pg_data_t *pgdat, struct scan_control *sc)
 
 		refaults = lruvec_page_state(target_lruvec,
 				WORKINGSET_ACTIVATE_ANON);
-		if (refaults != target_lruvec->refaults[0] ||
+		if (refaults != target_lruvec->refaults[WORKINGSET_ANON] ||
 			inactive_is_low(target_lruvec, LRU_INACTIVE_ANON))
 			sc->may_deactivate |= DEACTIVATE_ANON;
 		else
@@ -3243,7 +3243,7 @@ static void shrink_node(pg_data_t *pgdat, struct scan_control *sc)
 		 */
 		refaults = lruvec_page_state(target_lruvec,
 				WORKINGSET_ACTIVATE_FILE);
-		if (refaults != target_lruvec->refaults[1] ||
+		if (refaults != target_lruvec->refaults[WORKINGSET_FILE] ||
 		    inactive_is_low(target_lruvec, LRU_INACTIVE_FILE))
 			sc->may_deactivate |= DEACTIVATE_FILE;
 		else
@@ -3559,9 +3559,9 @@ static void snapshot_refaults(struct mem_cgroup *target_memcg, pg_data_t *pgdat)
 
 	target_lruvec = mem_cgroup_lruvec(target_memcg, pgdat);
 	refaults = lruvec_page_state(target_lruvec, WORKINGSET_ACTIVATE_ANON);
-	target_lruvec->refaults[0] = refaults;
+	target_lruvec->refaults[WORKINGSET_ANON] = refaults;
 	refaults = lruvec_page_state(target_lruvec, WORKINGSET_ACTIVATE_FILE);
-	target_lruvec->refaults[1] = refaults;
+	target_lruvec->refaults[WORKINGSET_FILE] = refaults;
 }
 
 /*