bug#53194: System test partition.img differs in size across hosts(?)

[Maxim Cournoyer]

Hi Tobias,

[...]

> diff --git a/gnu/build/image.scm b/gnu/build/image.scm
> index bdd5ec25a9..81caa424f8 100644
> --- a/gnu/build/image.scm
> +++ b/gnu/build/image.scm
> @@ -3,7 +3,7 @@
>  ;;; Copyright © 2016 Christine Lemmer-Webber <cwebber@dustycloud.org>
>  ;;; Copyright © 2016, 2017 Leo Famulari <leo@famulari.name>
>  ;;; Copyright © 2017 Marius Bakke <mbakke@fastmail.com>
> -;;; Copyright © 2020 Tobias Geerinckx-Rice <me@tobias.gr>
> +;;; Copyright © 2020, 2022 Tobias Geerinckx-Rice <me@tobias.gr>
>  ;;; Copyright © 2020 Mathieu Othacehe <m.othacehe@gmail.com>
>  ;;;
>  ;;; This file is part of GNU Guix.
> @@ -62,8 +62,10 @@ (define (size-in-kib size)
>  
>  (define (estimate-partition-size root)
>    "Given the ROOT directory, evaluate and return its size.  As this doesn't
> -take the partition metadata size into account, take a 25% margin."
> -  (* 1.25 (file-size root)))
> +take the partition metadata size into account, take a 25% margin.  As this in
> +turn doesn't take any constant overhead into account, force a 1-MiB minimum."
> +  (max (ash 1 20)
> +       (* 1.25 (file-size root))))
>  
>  (define* (make-ext-image partition target root
>                           #:key

Looks reasonable to me (although it is interesting that the behavior is
not the same across machines...).

While at it, you may want to fix this docstring:

--8<---------------cut here---------------start------------->8---
 (define (file-size file)
-  "Return the size of bytes of FILE, entering it if FILE is a directory."
+  "Return the size in bytes of FILE, entering it if FILE is a directory."
   (file-system-fold (const #t)
                     (lambda (file stat result)    ;leaf
                       (+ (stat:size stat) result))
--8<---------------cut here---------------end--------------->8---

in guix/build/store-copy.scm.

Thanks!

Maxim