Adding a new field to task_struct - stuck on booting

I added a new field to the task_struct and also 2 very basic syscalls the set and get this field.Now when I try to boot the VM (I am using Linux 4.15.18 Ubuntu on VirtualBox) I get the following message:madam: no arrays found in config file or automatically (repeating many times)gave up waiting for root file system device.alert! uuid=xxxx does not exist, dropping to a shell!I really don't understand what could I have done to cause this.

Those are all the changes that I have made:in include/linux/sched.h:

struct task_struct{volatile long state;int new_field;  //my addition...}

in include/linux/init_task.h:

#define INIT_TASK(tsk) \{INIT_TASK_TI(tsk)  \.state = 0, \.new_field = 0, \  //my addition...}

I also added my syscalls to include/linux/syscalls.h and to arch/x86/entry/syscalls/syscall_64.tblbut I don't think this is what causing the problem/