diff --git a/[refs] b/[refs]
index 529a63ec9ae2..263c3597139b 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 3b2710824e00d238554c13b5add347e6c701ab1a
+refs/heads/master: 5988ce239682854d4e632fb58bff000700830394
diff --git a/trunk/drivers/block/nbd.c b/trunk/drivers/block/nbd.c
index fdee7567fd15..f533f3375e24 100644
--- a/trunk/drivers/block/nbd.c
+++ b/trunk/drivers/block/nbd.c
@@ -754,9 +754,20 @@ static int __init nbd_init(void)
 		return -ENOMEM;
 
 	part_shift = 0;
-	if (max_part > 0)
+	if (max_part > 0) {
 		part_shift = fls(max_part);
 
+		/*
+		 * Adjust max_part according to part_shift as it is exported
+		 * to user space so that user can know the max number of
+		 * partition kernel should be able to manage.
+		 *
+		 * Note that -1 is required because partition 0 is reserved
+		 * for the whole disk.
+		 */
+		max_part = (1UL << part_shift) - 1;
+	}
+
 	if ((1UL << part_shift) > DISK_MAX_PARTS)
 		return -EINVAL;