commit f1365b8dcc2793f2842c1c464f2091c918b2b8d1
author Mike Frysinger <vapier@chromium.org> Fri Oct 06 16:11:18 2017 -0400
committer chrome-bot <chrome-bot@chromium.org> Sat Oct 21 11:46:53 2017 -0700
tree c81b359b03bcf1e6b91d36c58e7f4db2f72418d7
parent 237117b1f1f2c473b586ebc67a8cef91fdcffacf

disk_layout_util: use losetup for GPT parsing when possible

Newer versions of losetup have a --partscan option which will create
partitions via the local GPT for us.  Use that when available so we're
more flexible with changing disk images (relative to the base layout).

BUG=None
TEST=created a VM image and used mount_image.sh

Change-Id: I115d769eac2710915ac098304969bdecbe25d317
Reviewed-on: https://chromium-review.googlesource.com/705759
Commit-Ready: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Gwendal Grignou <gwendal@google.com>

build_library/disk_layout_util.sh

diff --git a/build_library/disk_layout_util.sh b/build_library/disk_layout_util.sh
index 8fd1077..04c2198 100644
--- a/build_library/disk_layout_util.sh
+++ b/build_library/disk_layout_util.sh
@@ -254,6 +254,24 @@
 esac
 
 EOF
+
+    if [[ "${x}" != "${umount}" ]]; then
+      cat >>"${x}" <<\EOF
+# If losetup is new enough to create the partition table, use that instead.
+LOOPDEV=''
+cleanup() {
+  if [[ -n "${LOOPDEV}" ]]; then
+    sudo losetup -d "${LOOPDEV}"
+  fi
+}
+trap cleanup EXIT
+if sudo losetup --help |& grep -q -e--partscan; then
+  LOOPDEV=$(sudo losetup -P -f --show "${TARGET}") || exit 1
+fi
+
+EOF
+    fi
+
     echo "${gpt_layout}" >> "${x}"
   done
 
@@ -275,18 +293,31 @@
     done
 
     cat <<EOF >> "${unpack}"
-dd if=${target} of=${file} ${dd_args} skip=${start}
+if [[ -n "\${LOOPDEV}" ]]; then
+  sudo dd if="\${LOOPDEV}p${part}" of="${file}"
+else
+  dd if=${target} of="${file}" ${dd_args} skip=${start}
+fi
 ln -sfT ${file} "${file}_${label}"
 EOF
     cat <<EOF >> "${pack}"
-dd if=${file} of=${target} ${dd_args} seek=${start} conv=notrunc
+if [[ -n "\${LOOPDEV}" ]]; then
+  sudo dd if="${file}" of="\${LOOPDEV}p${part}"
+else
+  dd if="${file}" of=${target} ${dd_args} seek=${start} conv=notrunc
+fi
 EOF
 
     if [[ ${size} -gt 1 ]]; then
       cat <<-EOF >>"${mount}"
 (
-mkdir -p ${dir}
-m=( sudo mount -o loop,offset=${start_b},sizelimit=${size_b} ${target} ${dir} )
+mkdir -p "${dir}"
+m=( sudo mount )
+if [[ -n "\${LOOPDEV}" ]]; then
+  m+=( "\${LOOPDEV}p${part}" "${dir}" )
+else
+  m+=( -o loop,offset=${start_b},sizelimit=${size_b} "${target}" "${dir}" )
+fi
 if ! "\${m[@]}"; then
   if ! "\${m[@]}" -o ro; then
     rmdir ${dir}