1 files changed, 17 insertions, 5 deletions

diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 84b143eef395..eb0586b9767d 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -367,8 +367,7 @@ int gntdev_map_grant_pages(struct gntdev_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;
 
@@ -377,8 +376,7 @@ int gntdev_map_grant_pages(struct gntdev_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;
@@ -394,8 +392,14 @@ static void __unmap_grant_pages_done(int result,
 	unsigned int i;
 	struct gntdev_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 != INVALID_GRANT_HANDLE)
+			successful_unmaps++;
+
 		WARN_ON(map->unmap_ops[offset + i].status != GNTST_okay &&
 			map->unmap_ops[offset + i].handle != INVALID_GRANT_HANDLE);
 		pr_debug("unmap handle=%d st=%d\n",
@@ -403,6 +407,10 @@ static void __unmap_grant_pages_done(int result,
 			map->unmap_ops[offset+i].status);
 		map->unmap_ops[offset+i].handle = INVALID_GRANT_HANDLE;
 		if (use_ptemod) {
+			if (map->kunmap_ops[offset + i].status == GNTST_okay &&
+			    map->kunmap_ops[offset + i].handle != INVALID_GRANT_HANDLE)
+				successful_unmaps++;
+
 			WARN_ON(map->kunmap_ops[offset + i].status != GNTST_okay &&
 				map->kunmap_ops[offset + i].handle != INVALID_GRANT_HANDLE);
 			pr_debug("kunmap handle=%u st=%d\n",
@@ -411,11 +419,15 @@ static void __unmap_grant_pages_done(int result,
 			map->kunmap_ops[offset+i].handle = INVALID_GRANT_HANDLE;
 		}
 	}
+
 	/*
 	 * 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);