Re: [PATCH] gnu: Mark /gnu/store as needed for boot.

[Chris Marusich <cmmarusich@gmail.com>]

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John Darrington <jmd@gnu.org> writes:

> * gnu/system/file-systems.scm (all-subpaths): New procedure.
> (file-system-needed-for-boot?): Use it to check for ancestors
> of %store-directory.
> ---
>  gnu/system/file-systems.scm | 25 ++++++++++++++++++++++---
>  1 file changed, 22 insertions(+), 3 deletions(-)
>
> diff --git a/gnu/system/file-systems.scm b/gnu/system/file-systems.scm
> index 4cc1221..d42f271 100644
> --- a/gnu/system/file-systems.scm
> +++ b/gnu/system/file-systems.scm
> @@ -20,6 +20,7 @@
>    #:use-module (ice-9 match)
>    #:use-module (guix records)
>    #:use-module (guix store)
> +  #:use-module (guix build utils)
>    #:use-module ((gnu build file-systems)
>                  #:select (string->uuid uuid->string))
>    #:re-export (string->uuid
> @@ -95,11 +96,29 @@
>    (dependencies     file-system-dependencies      ; list of <file-system>
>                      (default '())))               ; or <mapped-device>
>  
> +
> +(define (all-subpaths path)
> +  "Given a directory PATH return a list of all paths which
> +are ancestors of this path, including PATH itself"
> + (let loop ((path (string-split path #\/))
> +	    (ac '()))
> +   (if (null? path)
> +       ac
> +       (loop (cdr path)
> +	     (cons
> +	      (string-append
> +	       (match ac
> +		 (()  "/")
> +		 ((x _ . _) (string-append x "/"))
> +		 ((x . _) x))
> +	       (car path))
> +	      ac)))))
> +

Is this procedure supposed to work with relative paths?  I get strange
results for "foo/bar":

--8<---------------cut here---------------start------------->8---
scheme@(guile-user)> (all-subpaths "foo/bar")
$4 = ("/foobar" "/foo")
scheme@(guile-user)>
--8<---------------cut here---------------end--------------->8---


>  (define-inlinable (file-system-needed-for-boot? fs)
> -  "Return true if FS has the 'needed-for-boot?' flag set, or if it's the root
> -file system."
> +  "Return true if FS has the 'needed-for-boot?' flag set, or if it holds
> +the store directory."
>    (or (%file-system-needed-for-boot? fs)
> -      (string=? "/" (file-system-mount-point fs))))
> +      (member (file-system-mount-point fs) (all-subpaths (%store-directory)))))

It seems to me like we could just use 'string-prefix?' here instead.  Am
I missing something?  Is it really necessary to define an 'all-subpaths'
procedure and use 'member' if 'string-prefix?' is good enough?

The title of this patch is "Mark /gnu/store as needed for boot."  I can
see how this change makes that happen.  But what is the purpose?  I
imagine that in some cases, if you don't do this, the initrd might not
mount the file system containing the store, which of course would not be
good.  Do you have a specific problem case in mind?

-- 
Chris

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