After more debugging, I found out that efivarfs_probe fails because of:
statfs("/sys/firmware/efi/efivars/", 0x7ffedb26c490) = -1 EINVAL (Invalid argument)
which seems closely related to bug 2034705.
After more debugging, I found out that efivarfs_probe fails because of:
statfs( "/sys/firmware/ efi/efivars/ ", 0x7ffedb26c490) = -1 EINVAL (Invalid argument)
which seems closely related to bug 2034705.