From 1a3e63250edef398f95bbd16c6e412a85e83e36c Mon Sep 17 00:00:00 2001
From: Rutherther <rutherther@ditigal.xyz>
Date: Wed, 14 May 2025 21:44:20 +0200
Subject: [PATCH] Improve shared guix cache

- Add -o nonempty option to make sure the service can run even with
users that already have a cache
- Rename the config with -config suffix
---
 modules/ruther/services/bind.scm | 32 +++++++++++++++++++-------------
 1 file changed, 19 insertions(+), 13 deletions(-)

diff --git a/modules/ruther/services/bind.scm b/modules/ruther/services/bind.scm
index 1bad1fc32245ff17ae205cc85c0918bc564c69d7..ca3cac5190df96410e069570f82fe777cb526223 100644
--- a/modules/ruther/services/bind.scm
+++ b/modules/ruther/services/bind.scm
@@ -13,11 +13,11 @@
             user-info-user
             user-info-home
 
-            guix-shared-cache
-            guix-shared-cache-bindfs
-            guix-shared-cache-main-user
-            guix-shared-cache-shared-directory
-            guix-shared-cache-users
+            guix-shared-cache-config
+            guix-shared-cache-config-bindfs
+            guix-shared-cache-config-main-user
+            guix-shared-cache-config-shared-directory
+            guix-shared-cache-config-users
 
             guix-shared-cache-service-type))
 
@@ -39,7 +39,7 @@
     (group "root")
     (home "/root"))))
 
-(define-configuration/no-serialization guix-shared-cache
+(define-configuration/no-serialization guix-shared-cache-config
   (bindfs (file-like bindfs) "The bindfs package to use.")
   (fuse (file-like fuse-2) "The fuse package to use")
 
@@ -51,21 +51,24 @@
 (define (shared-guix-cache-shepherd-services config)
   (map
    (lambda (user)
-     (let* ((fuse (guix-shared-cache-fuse config))
-            (bindfs (guix-shared-cache-bindfs config))
+     (let* ((fuse (guix-shared-cache-config-fuse config))
+            (bindfs (guix-shared-cache-config-bindfs config))
             (user-name (user-info-user user))
             (user-home (user-info-home user))
             (user-group (user-info-group user))
             (user-files (user-info-files user))
-            (main-group (guix-shared-cache-main-group config))
-            (main-user (guix-shared-cache-main-user config))
-            (shared-dir-base (guix-shared-cache-shared-directory config))
+            (main-group (guix-shared-cache-config-main-group config))
+            (main-user (guix-shared-cache-config-main-user config))
+            (shared-dir-base (guix-shared-cache-config-shared-directory config))
             (mount-dir-base (string-append user-home "/.cache/guix")))
        (shepherd-service
+        ;; Each user has their own service
         (provision (list (symbol-append 'shared-guix-cache-
                                         (string->symbol user-name))))
+        ;; Make sure the homes are already present
         (requirement '(file-systems user-homes))
         (stop #~(lambda args
+                  ;; For each mounted directory, unmount it
                   (for-each
                    (lambda (dir)
                      (let ((mount-dir (string-append #$mount-dir-base "/" dir) ))
@@ -76,6 +79,8 @@
                    '#$user-files)
                   #f))
         (start #~(lambda args
+                   ;; Like mkdir-p, but chown all created directories
+                   ;; by the user specified.
                    (define (mkdir-recursively dir user group)
                      (unless (eq? dir "/")
                        (when (not (file-exists? dir))
@@ -87,7 +92,7 @@
                                 (gid (passwd:gid pw)))
                            (chown dir uid gid)))))
 
-
+                   ;; For each mount directory, mount it to the shared directory
                    (for-each
                     (lambda (dir)
                       (let ((mount-dir (string-append #$mount-dir-base "/" dir))
@@ -100,6 +105,7 @@
                          (string-append "--create-for-user=" #$main-user)
                          (string-append "--force-user=" #$user-name)
                          (string-append "--force-group=" #$user-group)
+                         "-o" "nonempty"
                          shared-dir mount-dir)))
                     '#$user-files)
                    #t)))))
@@ -116,7 +122,7 @@
              (guix-shared-cache
               (inherit original)
               (users (append (guix-shared-cache-users original))))))
-   (default-value (guix-shared-cache))
+   (default-value (guix-shared-cache-config))
    (description "Share ~/.cache/guix between
 multiple users. The root user is going to own the shared checkout,
 and will be part of the users who can use the shared checkout.