mm: introduce page_lru_base_type()

Instead of abusing page_is_file_cache() for LRU list index arithmetic, add
another helper with a more appropriate name and convert the non-boolean
users of page_is_file_cache() accordingly.

This new helper gives the LRU base type a page is supposed to live on,
inactive anon or inactive file.

[hugh.dickins@tiscali.co.uk: convert del_page_from_lru() also]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 24 insertions, 9 deletions

diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
index 7fbb97267556..99977ff45b83 100644
--- a/include/linux/mm_inline.h
+++ b/include/linux/mm_inline.h
@@ -39,21 +39,36 @@ del_page_from_lru_list(struct zone *zone, struct page *page, enum lru_list l)
         mem_cgroup_del_lru_list(page, l);
 }
 
+/**
+ * page_lru_base_type - which LRU list type should a page be on?
+ * @page: the page to test
+ *
+ * Used for LRU list index arithmetic.
+ *
+ * Returns the base LRU type - file or anon - @page should be on.
+ */
+static inline enum lru_list page_lru_base_type(struct page *page)
+{
+        if (page_is_file_cache(page))
+                return LRU_INACTIVE_FILE;
+        return LRU_INACTIVE_ANON;
+}
+
 static inline void
 del_page_from_lru(struct zone *zone, struct page *page)
 {
-        enum lru_list l = LRU_BASE;
+        enum lru_list l;
 
         list_del(&page->lru);
         if (PageUnevictable(page)) {
                 __ClearPageUnevictable(page);
                 l = LRU_UNEVICTABLE;
         } else {
+                l = page_lru_base_type(page);
                 if (PageActive(page)) {
                         __ClearPageActive(page);
                         l += LRU_ACTIVE;
                 }
-                l += page_is_file_cache(page);
         }
         __dec_zone_state(zone, NR_LRU_BASE + l);
         mem_cgroup_del_lru_list(page, l);
@@ -68,14 +83,14 @@ del_page_from_lru(struct zone *zone, struct page *page)
  */
 static inline enum lru_list page_lru(struct page *page)
 {
-        enum lru_list lru = LRU_BASE;
+        enum lru_list lru;
 
         if (PageUnevictable(page))
                 lru = LRU_UNEVICTABLE;
         else {
+                lru = page_lru_base_type(page);
                 if (PageActive(page))
                         lru += LRU_ACTIVE;
-                lru += page_is_file_cache(page);
         }
 
         return lru;
diff --git a/mm/swap.c b/mm/swap.c
index cb29ae5d33ab..168d53e6e58e 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -118,7 +118,7 @@ static void pagevec_move_tail(struct pagevec *pvec)
                         spin_lock(&zone->lru_lock);
                 }
                 if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
-                        int lru = page_is_file_cache(page);
+                        int lru = page_lru_base_type(page);
                         list_move_tail(&page->lru, &zone->lru[lru].list);
                         pgmoved++;
                 }
@@ -181,7 +181,7 @@ void activate_page(struct page *page)
         spin_lock_irq(&zone->lru_lock);
         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
                 int file = page_is_file_cache(page);
-                int lru = LRU_BASE + file;
+                int lru = page_lru_base_type(page);
                 del_page_from_lru_list(zone, page, lru);
 
                 SetPageActive(page);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index cad5d528a6f0..30e56ee833f8 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -531,7 +531,7 @@ redo:
                  * unevictable page on [in]active list.
                  * We know how to handle that.
                  */
-                lru = active + page_is_file_cache(page);
+                lru = active + page_lru_base_type(page);
                 lru_cache_add_lru(page, lru);
         } else {
                 /*
@@ -986,7 +986,7 @@ static unsigned long clear_active_flags(struct list_head *page_list,
         struct page *page;
 
         list_for_each_entry(page, page_list, lru) {
-                lru = page_is_file_cache(page);
+                lru = page_lru_base_type(page);
                 if (PageActive(page)) {
                         lru += LRU_ACTIVE;
                         ClearPageActive(page);
@@ -2652,7 +2652,7 @@ static void check_move_unevictable_page(struct page *page, struct zone *zone)
 retry:
         ClearPageUnevictable(page);
         if (page_evictable(page, NULL)) {
-                enum lru_list l = LRU_INACTIVE_ANON + page_is_file_cache(page);
+                enum lru_list l = page_lru_base_type(page);
 
                 __dec_zone_state(zone, NR_UNEVICTABLE);
                 list_move(&page->lru, &zone->lru[l].list);