Avoid getting confused by inaccessible loop device backing paths

(LP: #938724).

debian/changelog

@@ -6,6 +6,8 @@ grub2 (2.00-7) UNRELEASED; urgency=low
   * Merge from Ubuntu:
     - Prefer translations from language packs (LP: #537998).  (No-op for
       Debian, but harmless.)
+    - Avoid getting confused by inaccessible loop device backing paths
+      (LP: #938724).
 
  -- Colin Watson <cjwatson@debian.org>  Wed, 26 Sep 2012 13:16:52 +0100
 

debian/patches/mkconfig_nonexistent_loopback.patch

@@ -0,0 +1,46 @@
+Description: Avoid getting confused by inaccessible loop device backing paths
+Author: Colin Watson <cjwatson@ubuntu.com>
+Bug-Ubuntu: https://bugs.launchpad.net/bugs/938724
+Forwarded: no
+Last-Update: 2012-09-07
+
+Index: b/util/grub-mkconfig_lib.in
+===================================================================
+--- a/util/grub-mkconfig_lib.in
++++ b/util/grub-mkconfig_lib.in
+@@ -138,7 +138,7 @@
+         /dev/*) ;;
+         *)
+           loop_device="${device}"
+-          device=`"${grub_probe}" --target=device "${loop_file}"`
++          device=`"${grub_probe}" --target=device "${loop_file}"` || return 0
+         ;;
+       esac
+     ;;
+Index: b/util/grub.d/30_os-prober.in
+===================================================================
+--- a/util/grub.d/30_os-prober.in
++++ b/util/grub.d/30_os-prober.in
+@@ -169,6 +169,11 @@
+ 	  LINITRD="${LINITRD#/boot}"
+ 	fi
+ 
++	if [ -z "${prepare_boot_cache}" ]; then
++	  prepare_boot_cache="$(prepare_grub_to_access_device ${LBOOT} | sed -e "s/^/\t/")"
++	  [ "${prepare_boot_cache}" ] || continue
++	fi
++
+ 	onstr="$(gettext_printf "(on %s)" "${DEVICE}")"
+ 	recovery_params="$(echo "${LPARAMS}" | grep 'single\|recovery')" || true
+ 	counter=1
+@@ -180,10 +185,6 @@
+ 	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 ${LBOOT} | sed -e "s/^/\t/")"
+-	fi
+-
+ 	if [ "x$is_first_entry" = xtrue ]; then
+             cat << EOF
+ menuentry '$(echo "$OS" | grub_quote)' --class gnu-linux --class gnu --class os \$menuentry_id_option 'osprober-gnulinux-simple-$boot_device_id' {

debian/patches/series

@@ -26,3 +26,4 @@ emu_freebsd.patch
 mkconfig_stderr_handling.patch
 tftp_endianness.patch
 install_locale_langpack.patch
+mkconfig_nonexistent_loopback.patch

util/grub-mkconfig_lib.in

@@ -138,7 +138,7 @@ prepare_grub_to_access_device ()
         /dev/*) ;;
         *)
           loop_device="${device}"
-          device=`"${grub_probe}" --target=device "${loop_file}"`
+          device=`"${grub_probe}" --target=device "${loop_file}"` || return 0
         ;;
       esac
     ;;

util/grub.d/30_os-prober.in

@@ -169,6 +169,11 @@ EOF
 	  LINITRD="${LINITRD#/boot}"
 	fi
 
+	if [ -z "${prepare_boot_cache}" ]; then
+	  prepare_boot_cache="$(prepare_grub_to_access_device ${LBOOT} | sed -e "s/^/\t/")"
+	  [ "${prepare_boot_cache}" ] || continue
+	fi
+
 	onstr="$(gettext_printf "(on %s)" "${DEVICE}")"
 	recovery_params="$(echo "${LPARAMS}" | grep 'single\|recovery')" || true
 	counter=1
@@ -180,10 +185,6 @@ 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 ${LBOOT} | sed -e "s/^/\t/")"
-	fi
-
 	if [ "x$is_first_entry" = xtrue ]; then
             cat << EOF
 menuentry '$(echo "$OS" | grub_quote)' --class gnu-linux --class gnu --class os \$menuentry_id_option 'osprober-gnulinux-simple-$boot_device_id' {