Subject: [PATCH 3/3] gnu: Don't abuse check-btrfs-file-system to scan.

From: Tobias Geerinckx-Rice <[email-masked]>
Date: Wed, 30 Jun 2021 22:20:18 +0200

It was never guaranteed to be run for non-root file systems.  It was for
root file systems only due to a bug now fixed.

* gnu/build/file-systems.scm (check-btrfs-file-system): Don't invoke
‘btrfs device scan’ here.
* gnu/system/linux-initrd.scm (raw-initrd): Do so here if any btrfs file
systems are present.
---
 gnu/build/file-systems.scm  |  2 --
 gnu/system/linux-initrd.scm | 13 ++++++++++++-
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/gnu/build/file-systems.scm b/gnu/build/file-systems.scm
index 8f76d8d564..607d9f418f 100644
--- a/gnu/build/file-systems.scm
+++ b/gnu/build/file-systems.scm
@@ -327,8 +327,6 @@ the file system even if it's marked as clean.  This is not recommended!  See
 @uref{https://bugzilla.redhat.com/show_bug.cgi?id=625967#c8}.  If REPAIR is
 false, do not write to DEVICE.  If it's #t, fix any errors found.  Otherwise,
 fix only those considered safe to repair automatically."
-  ;; XXX Why make this conditional on (check? #t) at all?
-  (system* "btrfs" "device" "scan")     ; ignore errors
   (if force?
       (match (status:exit-val
               (apply system* `("btrfs" "check" "--progress"
diff --git a/gnu/system/linux-initrd.scm b/gnu/system/linux-initrd.scm
index c6ba9bb560..46fe24b24e 100644
--- a/gnu/system/linux-initrd.scm
+++ b/gnu/system/linux-initrd.scm
@@ -210,6 +210,16 @@ upon error."
              (open source targets)))
          mapped-devices))
 
+  (define file-system-scan-commands
+    ;; File systems like btrfs need help to assemble multi-device file systems
+    ;; but do not use manually-specified <mapped-devices>.
+    (let ((file-system-types (map file-system-type file-systems)))
+      (if (member "btrfs" file-system-types)
+          ;; Ignore errors: if the system manages to boot anyway, the better.
+          #~((system* (string-append #$btrfs-progs/static "/bin/btrfs")
+                      "device" "scan"))
+          #~())))
+
   (define kodir
     (flat-linux-module-directory linux linux-modules))
 
@@ -245,7 +255,8 @@ upon error."
                         (map spec->file-system
                              '#$(map file-system->spec file-systems))
                         #:pre-mount (lambda ()
-                                      (and #$@device-mapping-commands))
+                                      (and #$@device-mapping-commands
+                                           #$@file-system-scan-commands))
                         #:linux-modules '#$linux-modules
                         #:linux-module-directory '#$kodir
                         #:keymap-file #+(and=> keyboard-layout
-- 
2.32.0