devmapper: Keep track of number of deleted devices

Keep track of number of deleted devices and export this information through
"docker info".

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Upstream-commit: d295dc66521e2734390473ec1f1da8a73ad3288a
Component: engine

components/engine/daemon/graphdriver/devmapper/driver.go

@@ -85,6 +85,7 @@ func (d *Driver) Status() [][2]string {
 		{"Udev Sync Supported", fmt.Sprintf("%v", s.UdevSyncSupported)},
 		{"Deferred Removal Enabled", fmt.Sprintf("%v", s.DeferredRemoveEnabled)},
 		{"Deferred Deletion Enabled", fmt.Sprintf("%v", s.DeferredDeleteEnabled)},
+		{"Deferred Deleted Device Count", fmt.Sprintf("%v", s.DeferredDeletedDeviceCount)},
 	}
 	if len(s.DataLoopback) > 0 {
 		status = append(status, [2]string{"Data loop file", s.DataLoopback})