mm, swap: add swap_cluster_list

This is a code clean up patch without functionality changes.  The
swap_cluster_list data structure and its operations are introduced to
provide some better encapsulation for the free cluster and discard
cluster list operations.  This avoid some code duplication, improved the
code readability, and reduced the total line number.

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/1472067356-16004-1-git-send-email-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Tim Chen <tim.c.chen@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Shaohua Li <shli@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 63 insertions, 70 deletions

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 2657acc..134c085 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -257,6 +257,53 @@ static inline void cluster_set_null(struct swap_cluster_info *info)
 	info->data = 0;
 }
 
+static inline bool cluster_list_empty(struct swap_cluster_list *list)
+{
+	return cluster_is_null(&list->head);
+}
+
+static inline unsigned int cluster_list_first(struct swap_cluster_list *list)
+{
+	return cluster_next(&list->head);
+}
+
+static void cluster_list_init(struct swap_cluster_list *list)
+{
+	cluster_set_null(&list->head);
+	cluster_set_null(&list->tail);
+}
+
+static void cluster_list_add_tail(struct swap_cluster_list *list,
+				  struct swap_cluster_info *ci,
+				  unsigned int idx)
+{
+	if (cluster_list_empty(list)) {
+		cluster_set_next_flag(&list->head, idx, 0);
+		cluster_set_next_flag(&list->tail, idx, 0);
+	} else {
+		unsigned int tail = cluster_next(&list->tail);
+
+		cluster_set_next(&ci[tail], idx);
+		cluster_set_next_flag(&list->tail, idx, 0);
+	}
+}
+
+static unsigned int cluster_list_del_first(struct swap_cluster_list *list,
+					   struct swap_cluster_info *ci)
+{
+	unsigned int idx;
+
+	idx = cluster_next(&list->head);
+	if (cluster_next(&list->tail) == idx) {
+		cluster_set_null(&list->head);
+		cluster_set_null(&list->tail);
+	} else
+		cluster_set_next_flag(&list->head,
+				      cluster_next(&ci[idx]), 0);
+
+	return idx;
+}
+
 /* Add a cluster to discard list and schedule it to do discard */
 static void swap_cluster_schedule_discard(struct swap_info_struct *si,
 		unsigned int idx)
@@ -270,17 +317,7 @@ static void swap_cluster_schedule_discard(struct swap_info_struct *si,
 	memset(si->swap_map + idx * SWAPFILE_CLUSTER,
 			SWAP_MAP_BAD, SWAPFILE_CLUSTER);
 
-	if (cluster_is_null(&si->discard_cluster_head)) {
-		cluster_set_next_flag(&si->discard_cluster_head,
-						idx, 0);
-		cluster_set_next_flag(&si->discard_cluster_tail,
-						idx, 0);
-	} else {
-		unsigned int tail = cluster_next(&si->discard_cluster_tail);
-		cluster_set_next(&si->cluster_info[tail], idx);
-		cluster_set_next_flag(&si->discard_cluster_tail,
-						idx, 0);
-	}
+	cluster_list_add_tail(&si->discard_clusters, si->cluster_info, idx);
 
 	schedule_work(&si->discard_work);
 }
@@ -296,15 +333,8 @@ static void swap_do_scheduled_discard(struct swap_info_struct *si)
 
 	info = si->cluster_info;
 
-	while (!cluster_is_null(&si->discard_cluster_head)) {
-		idx = cluster_next(&si->discard_cluster_head);
-
-		cluster_set_next_flag(&si->discard_cluster_head,
-						cluster_next(&info[idx]), 0);
-		if (cluster_next(&si->discard_cluster_tail) == idx) {
-			cluster_set_null(&si->discard_cluster_head);
-			cluster_set_null(&si->discard_cluster_tail);
-		}
+	while (!cluster_list_empty(&si->discard_clusters)) {
+		idx = cluster_list_del_first(&si->discard_clusters, info);
 		spin_unlock(&si->lock);
 
 		discard_swap_cluster(si, idx * SWAPFILE_CLUSTER,
@@ -312,19 +342,7 @@ static void swap_do_scheduled_discard(struct swap_info_struct *si)
 
 		spin_lock(&si->lock);
 		cluster_set_flag(&info[idx], CLUSTER_FLAG_FREE);
-		if (cluster_is_null(&si->free_cluster_head)) {
-			cluster_set_next_flag(&si->free_cluster_head,
-						idx, 0);
-			cluster_set_next_flag(&si->free_cluster_tail,
-						idx, 0);
-		} else {
-			unsigned int tail;
-
-			tail = cluster_next(&si->free_cluster_tail);
-			cluster_set_next(&info[tail], idx);
-			cluster_set_next_flag(&si->free_cluster_tail,
-						idx, 0);
-		}
+		cluster_list_add_tail(&si->free_clusters, info, idx);
 		memset(si->swap_map + idx * SWAPFILE_CLUSTER,
 				0, SWAPFILE_CLUSTER);
 	}
@@ -353,13 +371,8 @@ static void inc_cluster_info_page(struct swap_info_struct *p,
 	if (!cluster_info)
 		return;
 	if (cluster_is_free(&cluster_info[idx])) {
-		VM_BUG_ON(cluster_next(&p->free_cluster_head) != idx);
-		cluster_set_next_flag(&p->free_cluster_head,
-			cluster_next(&cluster_info[idx]), 0);
-		if (cluster_next(&p->free_cluster_tail) == idx) {
-			cluster_set_null(&p->free_cluster_tail);
-			cluster_set_null(&p->free_cluster_head);
-		}
+		VM_BUG_ON(cluster_list_first(&p->free_clusters) != idx);
+		cluster_list_del_first(&p->free_clusters, cluster_info);
 		cluster_set_count_flag(&cluster_info[idx], 0, 0);
 	}
 
@@ -398,14 +411,7 @@ static void dec_cluster_info_page(struct swap_info_struct *p,
 		}
 
 		cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
-		if (cluster_is_null(&p->free_cluster_head)) {
-			cluster_set_next_flag(&p->free_cluster_head, idx, 0);
-			cluster_set_next_flag(&p->free_cluster_tail, idx, 0);
-		} else {
-			unsigned int tail = cluster_next(&p->free_cluster_tail);
-			cluster_set_next(&cluster_info[tail], idx);
-			cluster_set_next_flag(&p->free_cluster_tail, idx, 0);
-		}
+		cluster_list_add_tail(&p->free_clusters, cluster_info, idx);
 	}
 }
 
@@ -421,8 +427,8 @@ scan_swap_map_ssd_cluster_conflict(struct swap_info_struct *si,
 	bool conflict;
 
 	offset /= SWAPFILE_CLUSTER;
-	conflict = !cluster_is_null(&si->free_cluster_head) &&
-		offset != cluster_next(&si->free_cluster_head) &&
+	conflict = !cluster_list_empty(&si->free_clusters) &&
+		offset != cluster_list_first(&si->free_clusters) &&
 		cluster_is_free(&si->cluster_info[offset]);
 
 	if (!conflict)
@@ -447,11 +453,11 @@ static void scan_swap_map_try_ssd_cluster(struct swap_info_struct *si,
 new_cluster:
 	cluster = this_cpu_ptr(si->percpu_cluster);
 	if (cluster_is_null(&cluster->index)) {
-		if (!cluster_is_null(&si->free_cluster_head)) {
-			cluster->index = si->free_cluster_head;
+		if (!cluster_list_empty(&si->free_clusters)) {
+			cluster->index = si->free_clusters.head;
 			cluster->next = cluster_next(&cluster->index) *
 					SWAPFILE_CLUSTER;
-		} else if (!cluster_is_null(&si->discard_cluster_head)) {
+		} else if (!cluster_list_empty(&si->discard_clusters)) {
 			/*
 			 * we don't have free cluster but have some clusters in
 			 * discarding, do discard now and reclaim them
@@ -2292,10 +2298,8 @@ static int setup_swap_map_and_extents(struct swap_info_struct *p,
 
 	nr_good_pages = maxpages - 1;	/* omit header page */
 
-	cluster_set_null(&p->free_cluster_head);
-	cluster_set_null(&p->free_cluster_tail);
-	cluster_set_null(&p->discard_cluster_head);
-	cluster_set_null(&p->discard_cluster_tail);
+	cluster_list_init(&p->free_clusters);
+	cluster_list_init(&p->discard_clusters);
 
 	for (i = 0; i < swap_header->info.nr_badpages; i++) {
 		unsigned int page_nr = swap_header->info.badpages[i];
@@ -2341,19 +2345,8 @@ static int setup_swap_map_and_extents(struct swap_info_struct *p,
 	for (i = 0; i < nr_clusters; i++) {
 		if (!cluster_count(&cluster_info[idx])) {
 			cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
-			if (cluster_is_null(&p->free_cluster_head)) {
-				cluster_set_next_flag(&p->free_cluster_head,
-								idx, 0);
-				cluster_set_next_flag(&p->free_cluster_tail,
-								idx, 0);
-			} else {
-				unsigned int tail;
-
-				tail = cluster_next(&p->free_cluster_tail);
-				cluster_set_next(&cluster_info[tail], idx);
-				cluster_set_next_flag(&p->free_cluster_tail,
-								idx, 0);
-			}
+			cluster_list_add_tail(&p->free_clusters, cluster_info,
+					      idx);
 		}
 		idx++;
 		if (idx == nr_clusters)