[PATCH -next] fs: fix namespace.c build error when CONFIG_MOUNT_NOTIFICATIONS is not set

[Randy Dunlap]

From: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>

Fix build error when CONFIG_MOUNT_NOTIFICATIONS is not set/enabled.

../fs/namespace.c:4320:42: error: 'struct mount' has no member named 'mnt_topology_changes'

Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
---
 fs/namespace.c |    4 ++++
 1 file changed, 4 insertions(+)

--- linux-next-20200515.orig/fs/namespace.c
+++ linux-next-20200515/fs/namespace.c
@@ -4317,7 +4317,11 @@ int fsinfo_generic_mount_topology(struct
 
 	m = real_mount(path->mnt);
 
+#ifdef CONFIG_MOUNT_NOTIFICATIONS
 	p->mnt_topology_changes	= atomic_read(&m->mnt_topology_changes);
+#else
+	p->mnt_topology_changes	= 0;
+#endif
 	p->parent_id = m->mnt_parent->mnt_id;
 
 	if (path->mnt == root.mnt) {