1 files changed, 45 insertions, 7 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 057e44b97aa..79a98d98ed3 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2356,6 +2356,48 @@ int sysctl_min_unmapped_ratio = 1;
  */
 int sysctl_min_slab_ratio = 5;
 
+static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
+{
+	unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
+	unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
+		zone_page_state(zone, NR_ACTIVE_FILE);
+
+	/*
+	 * It's possible for there to be more file mapped pages than
+	 * accounted for by the pages on the file LRU lists because
+	 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
+	 */
+	return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
+}
+
+/* Work out how many page cache pages we can reclaim in this reclaim_mode */
+static long zone_pagecache_reclaimable(struct zone *zone)
+{
+	long nr_pagecache_reclaimable;
+	long delta = 0;
+
+	/*
+	 * If RECLAIM_SWAP is set, then all file pages are considered
+	 * potentially reclaimable. Otherwise, we have to worry about
+	 * pages like swapcache and zone_unmapped_file_pages() provides
+	 * a better estimate
+	 */
+	if (zone_reclaim_mode & RECLAIM_SWAP)
+		nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
+	else
+		nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
+
+	/* If we can't clean pages, remove dirty pages from consideration */
+	if (!(zone_reclaim_mode & RECLAIM_WRITE))
+		delta += zone_page_state(zone, NR_FILE_DIRTY);
+
+	/* Watch for any possible underflows due to delta */
+	if (unlikely(delta > nr_pagecache_reclaimable))
+		delta = nr_pagecache_reclaimable;
+
+	return nr_pagecache_reclaimable - delta;
+}
+
 /*
  * Try to free up some pages from this zone through reclaim.
  */
@@ -2390,9 +2432,7 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
 	reclaim_state.reclaimed_slab = 0;
 	p->reclaim_state = &reclaim_state;
 
-	if (zone_page_state(zone, NR_FILE_PAGES) -
-		zone_page_state(zone, NR_FILE_MAPPED) >
-		zone->min_unmapped_pages) {
+	if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
 		/*
 		 * Free memory by calling shrink zone with increasing
 		 * priorities until we have enough memory freed.
@@ -2450,10 +2490,8 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
 	 * if less than a specified percentage of the zone is used by
 	 * unmapped file backed pages.
 	 */
-	if (zone_page_state(zone, NR_FILE_PAGES) -
-	    zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages
-	    && zone_page_state(zone, NR_SLAB_RECLAIMABLE)
-			<= zone->min_slab_pages)
+	if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
+	    zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
 		return 0;
 
 	if (zone_is_all_unreclaimable(zone))