diff --git a/mm/mmap.c b/mm/mmap.c
index d49736f..a65efd4 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -122,9 +122,17 @@
 		return 0;
 
 	if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
-		unsigned long n;
+		free = global_page_state(NR_FREE_PAGES);
+		free += global_page_state(NR_FILE_PAGES);
 
-		free = global_page_state(NR_FILE_PAGES);
+		/*
+		 * shmem pages shouldn't be counted as free in this
+		 * case, they can't be purged, only swapped out, and
+		 * that won't affect the overall amount of available
+		 * memory in the system.
+		 */
+		free -= global_page_state(NR_SHMEM);
+
 		free += nr_swap_pages;
 
 		/*
@@ -136,6 +144,14 @@
 		free += global_page_state(NR_SLAB_RECLAIMABLE);
 
 		/*
+		 * Leave reserved pages. The pages are not for anonymous pages.
+		 */
+		if (free <= totalreserve_pages)
+			goto error;
+		else
+			free -= totalreserve_pages;
+
+		/*
 		 * Leave the last 3% for root
 		 */
 		if (!cap_sys_admin)
@@ -144,30 +160,6 @@
 		if (free > pages)
 			return 0;
 
-		/*
-		 * nr_free_pages() is very expensive on large systems,
-		 * only call if we're about to fail.
-		 */
-		n = nr_free_pages();
-
-		/*
-		 * Leave reserved pages. The pages are not for anonymous pages.
-		 */
-		if (n <= totalreserve_pages)
-			goto error;
-		else
-			n -= totalreserve_pages;
-
-		/*
-		 * Leave the last 3% for root
-		 */
-		if (!cap_sys_admin)
-			n -= n / 32;
-		free += n;
-
-		if (free > pages)
-			return 0;
-
 		goto error;
 	}