From 989f83d664999deeb28d03a847e8f00a28639d7d Mon Sep 17 00:00:00 2001
From: Colin Watson <cjwatson@ubuntu.com>
Date: Mon, 13 Jan 2014 12:13:08 +0000
Subject: Avoid getting confused by inaccessible loop device backing paths

Bug-Ubuntu: https://bugs.launchpad.net/bugs/938724
Forwarded: no
Last-Update: 2021-09-24

Patch-Name: mkconfig-nonexistent-loopback.patch
---
 util/grub-mkconfig_lib.in   | 2 +-
 util/grub.d/30_os-prober.in | 9 +++++----
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/util/grub-mkconfig_lib.in b/util/grub-mkconfig_lib.in
index e62cfc22b..b6a1d7dec 100644
--- a/util/grub-mkconfig_lib.in
+++ b/util/grub-mkconfig_lib.in
@@ -143,7 +143,7 @@ prepare_grub_to_access_device ()
         *)
           loop_device="$1"
           shift
-          set -- `"${grub_probe}" --target=device "${loop_file}"` "$@"
+          set -- `"${grub_probe}" --target=device "${loop_file}"` "$@" || return 0
         ;;
       esac
     ;;
diff --git a/util/grub.d/30_os-prober.in b/util/grub.d/30_os-prober.in
index 37d5f05b5..e2ec80eb9 100644
--- a/util/grub.d/30_os-prober.in
+++ b/util/grub.d/30_os-prober.in
@@ -222,6 +222,11 @@ EOF
 	  LINITRD="${LINITRD#/boot}"
 	fi
 
+	if [ -z "${prepare_boot_cache}" ]; then
+	  prepare_boot_cache="$(prepare_grub_to_access_device ${LBOOT} | grub_add_tab)"
+	  [ "${prepare_boot_cache}" ] || continue
+	fi
+
 	onstr="$(gettext_printf "(on %s)" "${DEVICE}")"
 	recovery_params="$(echo "${LPARAMS}" | grep 'single\|recovery')" || true
 	counter=1
@@ -233,10 +238,6 @@ EOF
 	fi
 	used_osprober_linux_ids="$used_osprober_linux_ids 'osprober-gnulinux-$LKERNEL-${recovery_params}-$counter-$boot_device_id'"
 
-	if [ -z "${prepare_boot_cache}" ]; then
-	  prepare_boot_cache="$(prepare_grub_to_access_device ${LBOOT} | grub_add_tab)"
-	fi
-
 	# The GRUB_DISABLE_SUBMENU option used to be different than others since it was
 	# mentioned in the documentation that has to be set to 'y' instead of 'true' to
 	# enable it. This caused a lot of confusion to users that set the option to 'y',