Description: Handle filesystems loop-mounted on file images
 Improve prepare_grub_to_access_device to emit appropriate commands for such
 filesystems, and ignore them in Linux grub.d scripts.
 .
 This is needed for Ubuntu's Wubi installation method.
 .
 This patch isn't inherently Debian/Ubuntu-specific.  losetup and
 /proc/mounts are Linux-specific, though, so we might need to refine this
 before sending it upstream.  The changes to the Linux grub.d scripts might
 be better handled by integrating 10_lupin properly instead.

Index: b/util/grub-mkconfig_lib.in
===================================================================
--- a/util/grub-mkconfig_lib.in
+++ b/util/grub-mkconfig_lib.in
@@ -105,6 +105,21 @@
 {
   device="$1"
 
+  loop_file=
+  case ${device} in
+    /dev/loop/*|/dev/loop[0-9])
+      grub_loop_device="${device#/dev/}"
+      loop_file=`losetup "${device}" | sed -e "s/^[^(]*(\([^)]\+\)).*/\1/"`
+      case $loop_file in
+        /dev/*) ;;
+        *)
+          loop_device="${device}"
+          device=`"${grub_probe}" --target=device "${loop_file}"`
+        ;;
+      esac
+    ;;
+  esac
+
   if dmsetup status $device 2>/dev/null | grep -q 'crypt[[:space:]]$'; then
     grub_warn \
       "$device is a crypto device, which GRUB cannot read directly.  Some" \
@@ -141,6 +156,14 @@
   if fs_uuid="`"${grub_probe}" --device "${device}" --target=fs_uuid 2> /dev/null`" ; then
     echo "search --no-floppy --fs-uuid --set=root ${fs_uuid}"
   fi
+
+  if [ "x${loop_file}" != x ]; then
+    loop_mountpoint="$(awk '"'${loop_file}'" ~ "^"$2 && $2 != "/" { print $2 }' /proc/mounts | tail -n1)"
+    if [ "x${loop_mountpoint}" != x ]; then
+      echo "loopback ${grub_loop_device} ${loop_file#$loop_mountpoint}"
+      echo "set root=(${grub_loop_device})"
+    fi
+  fi
 }
 
 grub_file_is_not_garbage ()
Index: b/util/grub.d/10_linux.in
===================================================================
--- a/util/grub.d/10_linux.in
+++ b/util/grub.d/10_linux.in
@@ -40,6 +40,11 @@
 case ${GRUB_DEVICE} in
   /dev/loop/*|/dev/loop[0-9])
     GRUB_DEVICE=`losetup ${GRUB_DEVICE} | sed -e "s/^[^(]*(\([^)]\+\)).*/\1/"`
+    # We can't cope with devices loop-mounted from files here.
+    case ${GRUB_DEVICE} in
+      /dev/*) ;;
+      *) exit 0 ;;
+    esac
   ;;
 esac
 
Index: b/util/grub.d/20_linux_xen.in
===================================================================
--- a/util/grub.d/20_linux_xen.in
+++ b/util/grub.d/20_linux_xen.in
@@ -40,6 +40,11 @@
 case ${GRUB_DEVICE} in
   /dev/loop/*|/dev/loop[0-9])
     GRUB_DEVICE=`losetup ${GRUB_DEVICE} | sed -e "s/^[^(]*(\([^)]\+\)).*/\1/"`
+    # We can't cope with devices loop-mounted from files here.
+    case ${GRUB_DEVICE} in
+      /dev/*) ;;
+      *) exit 0 ;;
+    esac
   ;;
 esac