mm, vmscan: remove highmem_file_pages

With the reintroduction of per-zone LRU stats, highmem_file_pages is
redundant so remove it.

[mgorman@techsingularity.net: wrong stat is being accumulated in highmem_dirtyable_memory]
  Link: http://lkml.kernel.org/r/20160725092324.GM10438@techsingularity.netLink: http://lkml.kernel.org/r/1469110261-7365-3-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: gormanm

include/linux/mm_inline.h

@@ -4,22 +4,6 @@
 #include <linux/huge_mm.h>
 #include <linux/swap.h>
 
-#ifdef CONFIG_HIGHMEM
-extern atomic_t highmem_file_pages;
-
-static inline void acct_highmem_file_pages(int zid, enum lru_list lru,
-							int nr_pages)
-{
-	if (is_highmem_idx(zid) && is_file_lru(lru))
-		atomic_add(nr_pages, &highmem_file_pages);
-}
-#else
-static inline void acct_highmem_file_pages(int zid, enum lru_list lru,
-							int nr_pages)
-{
-}
-#endif
-
 /**
  * page_is_file_cache - should the page be on a file LRU or anon LRU?
  * @page: the page to test
@@ -47,7 +31,6 @@ static __always_inline void __update_lru_size(struct lruvec *lruvec,
 	__mod_node_page_state(pgdat, NR_LRU_BASE + lru, nr_pages);
 	__mod_zone_page_state(&pgdat->node_zones[zid],
 				NR_ZONE_LRU_BASE + lru, nr_pages);
-	acct_highmem_file_pages(zid, lru, nr_pages);
 }
 
 static __always_inline void update_lru_size(struct lruvec *lruvec,

mm/page-writeback.c

@@ -299,17 +299,13 @@ static unsigned long node_dirtyable_memory(struct pglist_data *pgdat)
 
 	return nr_pages;
 }
-#ifdef CONFIG_HIGHMEM
-atomic_t highmem_file_pages;
-#endif
 
 static unsigned long highmem_dirtyable_memory(unsigned long total)
 {
 #ifdef CONFIG_HIGHMEM
 	int node;
-	unsigned long x;
+	unsigned long x = 0;
 	int i;
-	unsigned long dirtyable = 0;
 
 	for_each_node_state(node, N_HIGH_MEMORY) {
 		for (i = ZONE_NORMAL + 1; i < MAX_NR_ZONES; i++) {
@@ -326,12 +322,12 @@ static unsigned long highmem_dirtyable_memory(unsigned long total)
 			nr_pages = zone_page_state(z, NR_FREE_PAGES);
 			/* watch for underflows */
 			nr_pages -= min(nr_pages, high_wmark_pages(z));
-			dirtyable += nr_pages;
+			nr_pages += zone_page_state(z, NR_ZONE_INACTIVE_FILE);
+			nr_pages += zone_page_state(z, NR_ZONE_ACTIVE_FILE);
+			x += nr_pages;
 		}
 	}
 
-	x = dirtyable + atomic_read(&highmem_file_pages);
-
 	/*
 	 * Unreclaimable memory (kernel memory or anonymous memory
 	 * without swap) can bring down the dirtyable pages below