shmem_recalc_inode: unable to handle kernel NULL pointer dereference

[Alex Xu (Hello71)]

I get this BUG in 5.1-rc1 sometimes when powering off the machine. I 
suspect my setup erroneously executes two swapoff+cryptsetup close 
operations simultaneously, so a race condition is triggered.

I am using a single swap on a plain dm-crypt device on a MBR partition 
on a SATA drive.

I think the problem is probably related to 
b56a2d8af9147a4efe4011b60d93779c0461ca97, so CCing the related people.

Thanks,
Alex.