Subject: Re: bug#37977: Mount options ignored for root file system

From: Guillaume Le Vaillant <[email-masked]>
Date: Sun, 17 Nov 2019 15:17:24 +0100

Ludovic Courtès skribis:

> The root file system is mounted by ‘mount-root-file-system’ in
> linux-boot.scm, and you’re right: it happily ignores any options in the
> <file-system> object for “/”.  :-)
>
> A solution would be to have ‘boot-system’ take an additional
> #:root-file-system-options parameter that it would pass down to
> ‘mount-root-file-system’, which would honor it.
>
> Would you like to give it a try?

The attached patch adds an 'options' parameter to
'mount-root-file-system' and makes 'boot-system' use it with the
content of the 'options' field of the <file-system> object for "/".

It's not exactly the solution you described (adding a keyword argument
to 'boot-system'), but I think it should work. What do you think?

I tried it with my btrfs root file system, and it is correctly mounted
with the options declared in my '/etc/config.scm' file.

>From 3597f0fda6f6a13bf1fdab0fcde4f72ece688d93 Mon Sep 17 00:00:00 2001
From: Guillaume Le Vaillant <[email-masked]>
Date: Sun, 17 Nov 2019 14:15:21 +0100
Subject: [PATCH] linux-boot: Don't ignore options when mounting root file
 system.

* gnu/build/linux-boot.scm (mount-root-file-system): Add the 'options'
  keyword argument and use it when mounting the root file system.
  (boot-system): Pass the root file system options to
  'mount-root-file-system'.
---
 gnu/build/linux-boot.scm | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/gnu/build/linux-boot.scm b/gnu/build/linux-boot.scm
index 84a5447977..a8a9c2e2c8 100644
--- a/gnu/build/linux-boot.scm
+++ b/gnu/build/linux-boot.scm
@@ -1,6 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2013, 2014, 2015, 2016, 2017, 2018, 2019 Ludovic Courtès <[email-masked]>
 ;;; Copyright © 2017 Mathieu Othacehe <[email-masked]>
+;;; Copyright © 2019 Guillaume Le Vaillant <[email-masked]>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -357,15 +358,16 @@ the last argument of `mknod'."
           (filter-map string->number (scandir "/proc")))))
 
 (define* (mount-root-file-system root type
-                                 #:key volatile-root?)
+                                 #:key volatile-root? options)
   "Mount the root file system of type TYPE at device ROOT.  If VOLATILE-ROOT?
 is true, mount ROOT read-only and make it an overlay with a writable tmpfs
-using the kernel built-in overlayfs."
+using the kernel built-in overlayfs.  OPTIONS indicates the options to use
+to mount ROOT."
 
   (if volatile-root?
       (begin
         (mkdir-p "/real-root")
-        (mount root "/real-root" type MS_RDONLY)
+        (mount root "/real-root" type MS_RDONLY options)
         (mkdir-p "/rw-root")
         (mount "none" "/rw-root" "tmpfs")
 
@@ -382,7 +384,7 @@ using the kernel built-in overlayfs."
                "lowerdir=/real-root,upperdir=/rw-root/upper,workdir=/rw-root/work"))
       (begin
         (check-file-system root type)
-        (mount root "/root" type)))
+        (mount root "/root" type 0 options)))
 
   ;; Make sure /root/etc/mtab is a symlink to /proc/self/mounts.
   (false-if-exception
@@ -472,6 +474,12 @@ upon error."
              mounts)
         "ext4"))
 
+  (define root-fs-options
+    (any (lambda (fs)
+           (and (root-mount-point? fs)
+                (file-system-options fs)))
+         mounts))
+
   (display "Welcome, this is GNU's early boot Guile.\n")
   (display "Use '--repl' for an initrd REPL.\n\n")
 
@@ -524,7 +532,8 @@ upon error."
                              (else (file-system-label root)))))
              (mount-root-file-system (canonicalize-device-spec root)
                                      root-fs-type
-                                     #:volatile-root? volatile-root?))
+                                     #:volatile-root? volatile-root?
+                                     #:options root-fs-options))
            (mount "none" "/root" "tmpfs"))
 
        ;; Mount the specified file systems.
-- 
2.24.0