+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;
+}
+