Subject: bug#59425: guix shell --container fails to mount host filesystem

From: bbb ee <[email-masked]>
Date: Mon, 21 Nov 2022 00:48:24 +0100

## description
guix shell --container can only mount subdir in /tmp, and fail for all
other dir:
```
# success mount in all subdir of  /tmp
dev_1@dev_1 /tmp/test2$ df .
Filesystem     1K-blocks      Used Available Use% Mounted on
/dev/nvme0n1p7 209921236 180793652  19663932  91% /
dev_1@dev_1 /tmp/test2$ guix shell --container coreutils -- echo Elmo
Elmo
dev_1@dev_1 /tmp/test2$ cd /tmp/
dev_1@dev_1 /tmp$ df .
Filesystem     1K-blocks      Used Available Use% Mounted on
/dev/nvme0n1p7 209921236 180793720  19663864  91% /
dev_1@dev_1 /tmp$ guix shell --container coreutils -- echo Elmo
Elmo

# fail for all other dir
dev_1@dev_1 /tmp$ cd /
dev_1@dev_1 /$ df .
Filesystem     1K-blocks      Used Available Use% Mounted on
/dev/nvme0n1p7 209921236 180793808  19663776  91% /
dev_1@dev_1 /$ guix shell --container coreutils -- echo Elmo
guix shell: error: mount: mount "/" on "/tmp/guix-directory.fKcwvT//":
Invalid argument

dev_1@dev_1 /mnt/recoverData$ cd ~
dev_1@dev_1 ~$ df .
Filesystem     1K-blocks      Used Available Use% Mounted on
/dev/nvme0n1p7 209921236 180793732  19663852  91% /
dev_1@dev_1 ~$ guix shell --container coreutils -- echo Elmo
guix shell: error: mount: mount "/home/dev_1" on
"/tmp/guix-directory.LUuYdU//home/dev_1": Invalid argument

# Other partition is also no mountable:
dev_1@dev_1 /mnt$ cd recoverData/
dev_1@dev_1 /mnt/recoverData$ df .
Filesystem     1K-blocks     Used Available Use% Mounted on
/dev/nvme0n1p8 122503676 91394804  25287412  79% /mnt/recoverData
dev_1@dev_1 /mnt/recoverData$ guix shell --container coreutils -- echo Elmo
guix shell: error: mount: mount "/mnt/recoverData" on
"/tmp/guix-directory.ut68VE//mnt/recoverData": Invalid argument
```

## environment
```
$ uname -a
Linux dev_1 5.18.18 #1 SMP PREEMPT_DYNAMIC 1 x86_64 GNU/Linux
$ guix describe
Generation 9 Oct 22 2022 16:05:50 (current)
  guix 85aff4d
    repository URL: https://git.savannah.gnu.org/git/guix.git
    branch: master
    commit: 85aff4de30686359ffb50845eb0930c0a18dc8ba
  nonguix 3f00d57
    repository URL: https://gitlab.com/nonguix/nonguix
    branch: master
    commit: 3f00d57adce5d0a185708fd5c7c5ff6f852c2bf7
```

## similar issue:
https://issues.guix.gnu.org/46782