From: Michael Chang <mchang@suse.com>
Subject: create menus for btrfs snapshot 

References: fate#316522, fate#316232
Patch-Mainline: no

This patch adds a new script that will create the menus used for
booting btrfs snapshots.

v1:
* Support existing snapshots by creating their missing slave configs.
* Temporarily default to disable this feature until receiving more
  tests from QA.
* Introduce GRUB_ENABLE_CUSTOM_SNAPSHOT_SUBMENU to allow custom
  submenu for listing snapshots rather than the default one.

v2:
* Fix bootable snapshots not found while root is on Btrfs subvolume
  (bnc#859587)
* Create missing slave config in /.snapshots/<num>/
* Prefix with SUSE_ for related options

v3:
* When booting btrfs snapshots disabled, deleting snapshot master config
  if it's not customized

Signed-off-by: Michael Chang <mchang@suse.com>

Index: grub-2.02~beta2/Makefile.util.def
===================================================================
--- grub-2.02~beta2.orig/Makefile.util.def
+++ grub-2.02~beta2/Makefile.util.def
@@ -509,6 +509,13 @@ script = {
   installdir = grubconf;
 };
 
+script = {
+  name = '80_btrfs_snapshot';
+  common = util/grub.d/80_btrfs_snapshot.in;
+  installdir = grubconf;
+  condition = COND_HOST_LINUX;
+};
+
 program = {
   mansection = 1;
   name = grub-mkrescue;
Index: grub-2.02~beta2/util/grub-mkconfig.in
===================================================================
--- grub-2.02~beta2.orig/util/grub-mkconfig.in
+++ grub-2.02~beta2/util/grub-mkconfig.in
@@ -250,7 +250,10 @@ export GRUB_DEFAULT \
   GRUB_OS_PROBER_SKIP_LIST \
   GRUB_DISABLE_SUBMENU \
   GRUB_CMDLINE_LINUX_RECOVERY \
-  GRUB_USE_LINUXEFI
+  GRUB_USE_LINUXEFI \
+  SUSE_DISABLE_BOOTING_SNAPSHOT \
+  SUSE_DISABLE_BOOTING_SNAPSHOT_SUBMENU \
+  SUSE_ENABLE_CUSTOM_SNAPSHOT_SUBMENU
 
 if test "x${grub_cfg}" != "x"; then
   rm -f "${grub_cfg}.new"
Index: grub-2.02~beta2/util/grub.d/80_btrfs_snapshot.in
===================================================================
--- /dev/null
+++ grub-2.02~beta2/util/grub.d/80_btrfs_snapshot.in
@@ -0,0 +1,174 @@
+#! /bin/sh
+set -e
+
+# grub-mkconfig helper script.
+# Copyright (C) 2006,2007,2008,2009,2010  Free Software Foundation, Inc.
+#
+# GRUB is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# GRUB is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
+
+prefix="@prefix@"
+exec_prefix="@exec_prefix@"
+datarootdir="@datarootdir@"
+
+. "${datarootdir}/grub2/grub-mkconfig_lib"
+
+# It's pointless to proceed if not using Btrfs
+if [ "x${GRUB_FS}" != "xbtrfs" ]; then
+  exit 0
+fi
+
+# The default master/main config path looked up by core.img
+master_cfg="/boot/grub2/grub.cfg"
+
+# The config with submenu of bootable btrfs snapshots
+master_snapshot_cfg="/boot/grub2/snapshot_submenu.cfg"
+
+# The slave config path in btrfs snapshot that will be sourced by master config
+# The menu entries in slave config will have it's root overridable by specified
+# subvolume name
+slave_cfg_name="snapshot_menuentry.cfg"
+slave_cfg="boot/grub2/${slave_cfg_name}"
+
+# The current config which is being outputted by grub-mkconfig
+output_cfg=`readlink /proc/$PPID/fd/1 | sed s/.new$//`
+
+grub_mkconfig_dir=`dirname $0`
+grub_script_check="${bindir}/grub2-script-check"
+
+
+# The real root (subvolume) where system installed to
+rel_root=`make_system_path_relative_to_its_root /`
+
+# Remove any slave config if booting snapshot gets disabled, in case it will become
+# inconsistent on further updates, note this also removes master_snapshot_cfg
+
+# Temporarily we disable this as it is quite new and still in developing
+# It's subjected to be enabled by default in future as the option name
+# SUSE_DISABLE_BOOTING_SNAPSHOT suggests. So for new you'll need to explicit
+# specify SUSE_DISABLE_BOOTING_SNAPSHOT=false the update the config
+if [ "x${SUSE_DISABLE_BOOTING_SNAPSHOT}" != "xfalse" ]; then
+  rm -f "/${slave_cfg}"
+# Delete snapshot master config if not customized
+  if [ "x${SUSE_ENABLE_CUSTOM_SNAPSHOT_SUBMENU}" != "xtrue" ]; then
+    rm -f "${master_snapshot_cfg}"
+  fi
+  exit 0
+fi
+
+# Only attempt to update slave config with master
+if [ "x$output_cfg" = "x$master_cfg"  ]; then
+  # Create the slave config by redirecting the standard output to it
+  # Output menu entries with overridable root
+  overridable_root_by_subvol=true ${grub_mkconfig_dir}/10_linux >"/${slave_cfg}.new"
+
+  # Check if the config is sane to use
+  if ${grub_script_check} "/${slave_cfg}.new"; then
+      mv -f "/${slave_cfg}.new" "/${slave_cfg}"
+  fi
+
+  # Scan existing snapshots to create their missing slave configs
+  # This should only be done once
+
+  for s_dir in /.snapshots/*; do
+
+    snapshot="${s_dir}/snapshot"
+    config="${snapshot}/etc/default/grub"
+    bootdir="${snapshot}/boot"
+
+    if [ ! -d "$snapshot" ]; then
+      continue
+    elif [ -f "${snapshot}/${slave_cfg}" ]; then
+      continue
+    elif [ -f "${s_dir}/${slave_cfg_name}" ]; then
+      continue
+    fi
+
+    (
+    # source config for kernel command lines .. etc
+    if [ -f "$config" ]; then
+      . "$config"
+    else
+    # skip when no config
+      continue
+    fi
+
+    overridable_root_by_subvol=true boot_prefix="$bootdir" ${grub_mkconfig_dir}/10_linux > "/${slave_cfg}.new"
+    )
+
+    # Check if the config is sane to use
+    if ${grub_script_check} "/${slave_cfg}.new"; then
+        mv -f "/${slave_cfg}.new" "${s_dir}/${slave_cfg_name}"
+    fi
+  done
+
+fi
+
+# Create the bootable snapshots submenus in master config, use the ${OS} to indicate
+# distribution that owns these snapshots.
+if [ "x${GRUB_DISTRIBUTOR}" = "x" ] ; then
+  OS=GNU/Linux
+else
+  OS="${GRUB_DISTRIBUTOR}"
+fi
+
+# Offer an option to allow disabling (built-in) snapshot submenu. It's possible to use
+# any other submenu with more integrated information retrieved from certain snapshot
+# utility's metadata and this option would help to get their boot menu tidy without
+# submenu with duplicated purpose.
+if [ "x${SUSE_DISABLE_BOOTING_SNAPSHOT_SUBMENU}" != "xtrue" ]; then
+  cat <<EOF
+if [ -f  \${config_directory}/`basename ${master_snapshot_cfg}` ]; then
+  source \${config_directory}/`basename ${master_snapshot_cfg}`
+elif [ -z "\${config_directory}" -a -f  \$prefix/`basename ${master_snapshot_cfg}` ]; then
+  source \$prefix/`basename ${master_snapshot_cfg}`;
+fi
+EOF
+fi
+
+# Still we create the file regardless SUSE_DISABLE_BOOTING_SNAPSHOT_SUBMENU, as it
+# could be source to run as a backup
+# Here we search and list snapshots created by snapper by using it's convention on
+# naming snapshots
+
+if [ "x${SUSE_ENABLE_CUSTOM_SNAPSHOT_SUBMENU}" != "xtrue" ]; then
+
+# Write default config if custom one not in use
+  cat <<EOF >"${master_snapshot_cfg}"
+insmod regexp
+submenu "Bootable snapshots for ${OS}" {
+  for x in ${rel_root}/.snapshots/*; do
+    if [ -f "\$x/${slave_cfg_name}" ]; then
+      snapshot_found=true
+	submenu "\$x" "\$x/snapshot" "\$x/${slave_cfg_name}" {
+		set subvol="\$2"
+		export subvol
+		source "\$3"
+	}
+    elif [ -f "\$x/snapshot/${slave_cfg}" ]; then
+      snapshot_found=true
+	submenu "\$x" "\$x/snapshot" "\$x/snapshot/${slave_cfg}" {
+		set subvol="\$2"
+		export subvol
+		source "\$3"
+	}
+    fi
+  done
+  if [ x\$snapshot_found != xtrue ]; then
+	submenu "Not Found" {true}
+  fi
+}
+EOF
+
+fi
+