Don't fail if iface is being used by iSCSI session

pkg/volume/iscsi/BUILD

@@ -27,6 +27,7 @@ go_library(
         "//staging/src/k8s.io/apimachinery/pkg/types:go_default_library",
         "//staging/src/k8s.io/apiserver/pkg/util/feature:go_default_library",
         "//vendor/k8s.io/klog:go_default_library",
+        "//vendor/k8s.io/utils/exec:go_default_library",
         "//vendor/k8s.io/utils/keymutex:go_default_library",
         "//vendor/k8s.io/utils/strings:go_default_library",
     ],

pkg/volume/iscsi/iscsi_util.go

@@ -34,6 +34,7 @@ import (
 	"k8s.io/kubernetes/pkg/util/mount"
 	"k8s.io/kubernetes/pkg/volume"
 	volumeutil "k8s.io/kubernetes/pkg/volume/util"
+	utilexec "k8s.io/utils/exec"
 )
 
 const (
@@ -51,6 +52,10 @@ const (
 
 	// How many seconds to wait for a multipath device if at least two paths are available.
 	multipathDeviceTimeout = 10
+
+	// 'iscsiadm' error code stating that a session is logged in
+	// See https://github.com/open-iscsi/open-iscsi/blob/7d121d12ad6ba7783308c25ffd338a9fa0cc402b/include/iscsi_err.h#L37-L38
+	iscsiadmErrorSessExists = 15
 )
 
 var (
@@ -872,8 +877,13 @@ func cloneIface(b iscsiDiskMounter, newIface string) error {
 	// create new iface
 	out, err = b.exec.Run("iscsiadm", "-m", "iface", "-I", newIface, "-o", "new")
 	if err != nil {
-		lastErr = fmt.Errorf("iscsi: failed to create new iface: %s (%v)", string(out), err)
-		return lastErr
+		exit, ok := err.(utilexec.ExitError)
+		if ok && exit.ExitStatus() == iscsiadmErrorSessExists {
+			klog.Infof("iscsi: there is a session already logged in with iface %s", newIface)
+		} else {
+			lastErr = fmt.Errorf("iscsi: failed to create new iface: %s (%v)", string(out), err)
+			return lastErr
+		}
 	}
 	// update new iface records
 	for key, val := range params {