smb3: fix unneeded error message on change notify

We should not be logging a warning repeatedly on change notify.

CC: Stable <stable@vger.kernel.org> # v5.6+
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>

fs/cifs/smb2misc.c

@@ -354,9 +354,13 @@ smb2_get_data_area_len(int *off, int *len, struct smb2_sync_hdr *shdr)
 		  ((struct smb2_ioctl_rsp *)shdr)->OutputCount);
 		break;
 	case SMB2_CHANGE_NOTIFY:
+		*off = le16_to_cpu(
+		  ((struct smb2_change_notify_rsp *)shdr)->OutputBufferOffset);
+		*len = le32_to_cpu(
+		  ((struct smb2_change_notify_rsp *)shdr)->OutputBufferLength);
+		break;
 	default:
-		/* BB FIXME for unimplemented cases above */
-		cifs_dbg(VFS, "no length check for command\n");
+		cifs_dbg(VFS, "no length check for command %d\n", le16_to_cpu(shdr->Command));
 		break;
 	}