diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 2eeeb6fd631d..23f3411809f0 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -361,8 +361,7 @@ static int map_grant_pages(struct grant_map *map)
 	for (i = 0; i < map->count; i++) {
 		if (map->map_ops[i].status == GNTST_okay) {
 			map->unmap_ops[i].handle = map->map_ops[i].handle;
-			if (!use_ptemod)
-				alloced++;
+			alloced++;
 		} else if (!err)
 			err = -EINVAL;
 
@@ -371,8 +370,7 @@ static int map_grant_pages(struct grant_map *map)
 
 		if (use_ptemod) {
 			if (map->kmap_ops[i].status == GNTST_okay) {
-				if (map->map_ops[i].status == GNTST_okay)
-					alloced++;
+				alloced++;
 				map->kunmap_ops[i].handle = map->kmap_ops[i].handle;
 			} else if (!err)
 				err = -EINVAL;
@@ -388,8 +386,14 @@ static void __unmap_grant_pages_done(int result,
 	unsigned int i;
 	struct grant_map *map = data->data;
 	unsigned int offset = data->unmap_ops - map->unmap_ops;
+	int successful_unmaps = 0;
+	int live_grants;
 
 	for (i = 0; i < data->count; i++) {
+		if (map->unmap_ops[offset + i].status == GNTST_okay &&
+		    map->unmap_ops[offset + i].handle != -1)
+			successful_unmaps++;
+
 		WARN_ON(map->unmap_ops[offset+i].status &&
 			map->unmap_ops[offset+i].handle != -1);
 		pr_debug("unmap handle=%d st=%d\n",
@@ -397,6 +401,10 @@ static void __unmap_grant_pages_done(int result,
 			map->unmap_ops[offset+i].status);
 		map->unmap_ops[offset+i].handle = -1;
 		if (use_ptemod) {
+			if (map->kunmap_ops[offset + i].status == GNTST_okay &&
+			    map->kunmap_ops[offset + i].handle != -1)
+				successful_unmaps++;
+
 			WARN_ON(map->kunmap_ops[offset+i].status &&
 				map->kunmap_ops[offset+i].handle != -1);
 			pr_debug("kunmap handle=%u st=%d\n",
@@ -405,11 +413,15 @@ static void __unmap_grant_pages_done(int result,
 			map->kunmap_ops[offset+i].handle = -1;
 		}
 	}
+
 	/*
 	 * Decrease the live-grant counter.  This must happen after the loop to
 	 * prevent premature reuse of the grants by gnttab_mmap().
 	 */
-	atomic_sub(data->count, &map->live_grants);
+	live_grants = atomic_sub_return(successful_unmaps, &map->live_grants);
+	if (WARN_ON(live_grants < 0))
+		pr_err("%s: live_grants became negative (%d) after unmapping %d pages!\n",
+		       __func__, live_grants, successful_unmaps);
 
 	/* Release reference taken by unmap_grant_pages */
 	gntdev_put_map(NULL, map);