Bind mount at boot

[7e9wc56emjakcm]

Hello, I have a system where I had a bind mount at boot that's no longer 
booting after updating.  Unfortunately, I hadn't updated it in a while 
(updated about a year ago) so I'm not sure when this might have started.

I'm booting from a USB stick.

Here's the rough definition:

    (file-systems (let
        ( )
        (define mount1 (file-system
            (mount-point "/rw")
            (type "ext4")
            (device (uuid "d1fecab6-998a-4ae7-8a9f-21c3501b1371"))
            (options "data=ordered")
            (flags '(no-atime))
            (needed-for-boot? #t)
    ))
        (cons*
            (file-system
                (mount-point "/")
                (type "ext4")
                (device (file-system-label "IGNORED"))
            )

            mount1

            (file-system
                (mount-point "/var")
                (type "none")
                (device "/root/rw/var")
                (flags '(bind-mount))
                (dependencies (list mount1))
                (needed-for-boot? #t)
            )

            %base-file-systems
        )
    ))


Here's the boot log:

GC Warning: pthread_getattr_np or pthread_attr_getstack failed for main 
thread
GC Warning: Couldn't read /proc/stat
Welcome, this is GNU's early boot Guile.
Use '--repl' for an initrd REPL.

loading kernel modules...
waiting for partition '369bb03e-86ee-c56c-43e6-2c31369bb03e' to appear...
waiting for partition '369bb03e-86ee-c56c-43e6-2c31369bb03e' to appear...
Guix_image: recovering journal
Guix_image: clean, 94899/186944 files, 669355/747090 blocks
/dev/sda3: recovering journal
/dev/sda3: clean, 60270/4792320 files, 1988760/19144192 blocks
ice-9/boot-9.scm:1669:16: In procedure raise-exception:
In procedure statfs64: Function not implemented

Entering a new prompt.  Type `,bt' for a backtrace or `,q' to continue.
GNU Guile 3.0.2
Copyright (C) 1995-2020 Free Software Foundation, Inc.

Guile comes with ABSOLUTELY NO WARRANTY; for details type `,show w'.
This program is free software, and you are welcome to redistribute it
under certain conditions; type `,show c' for details.

Enter `,help' for help.
scheme@(guile-user)> [  150.243364] blk_update_request: I/O error, dev 
sdb, sector 0 op 0x1:(WRITE) flags 0x800 phys_seg 0 prio class 0
,bt
,bt

In gnu/build/linux-boot.scm:
    623:8  5 (_)
In srfi/srfi-1.scm:
    634:9  4 (for-each #<procedure mount-file-system (fs #:key root)> …)
In gnu/build/file-systems.scm:
   924:56  3 (mount-file-system #<<file-system> device: "/root/rw/v…> …)
In guix/build/syscalls.scm:
   848:31  2 (_ "/root/rw/var")
    435:8  1 (_ . _)
In ice-9/boot-9.scm:
  1669:16  0 (raise-exception _ #:continuable? _)