1 files changed, 45 insertions, 7 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 057e44b97aa1..79a98d98ed33 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))