From ef85e0be874a627e89ab9ae3e2d33cd2263707e2 Mon Sep 17 00:00:00 2001
From: Dobrica Pavlinusic <dpavlin@rot13.org>
Date: Thu, 4 Oct 2018 12:21:51 +0200
Subject: [PATCH] remove PARTITION_ALIGNMENT and fix 4k block size instance
 disks

Since sfdisk doesn't supprot forced chs geometry any more, in situations
where underlaying storage has 4k block, this script will create correct
partition table for host, but not for guest which expects 512b blocks.

This will make machine unbootable, since once kvm starts partition will
be at wrong offset and it won't boot.

Solution is to re-create partition table at end using losetup which has
512b blocks.

Since PARTITION_ALIGNMENT is created using 4k block as base, it will
create filesystem at wrong place if you are using default value of 2048.
This hard-codes host partition table to 1M (which will work on hosts
with both 512b and 4k blocks) and then use 2048 when using 512b blocks.
---
 common.sh.in | 17 ++++++++++++++---
 defaults     |  6 ------
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/common.sh.in b/common.sh.in
index d21ed0c..402fcd5 100644
--- a/common.sh.in
+++ b/common.sh.in
@@ -101,9 +101,9 @@ format_disk0() {
   if sfdisk --help | fgrep -q -- '--no-reread'; then
     ARGS="--no-reread $ARGS"
   fi
-
+  ARGS="--label dos $ARGS"
   sfdisk $ARGS --quiet "$1" <<EOF
-${PARTITION_ALIGNMENT},,L,*
+1M,,L,*
 EOF
 }
 
@@ -127,6 +127,18 @@ map_disk0() {
 
 unmap_disk0() {
   kpartx -d -p- $1
+
+  if sfdisk --help | fgrep -q -- '--no-reread'; then
+    ARGS="--no-reread $ARGS"
+  fi
+
+  # loopback device has correct 512b blocks
+  blockdev=$(losetup --show -f $1)
+  sfdisk $ARGS --delete "$blockdev"
+  sfdisk $ARGS --label dos --quiet $blockdev <<EOF
+2048,,L,*
+EOF
+  losetup -d $blockdev
 }
 
 cleanup() {
@@ -161,7 +173,6 @@ fi
 : ${VARIANTS_DIR:="@sysconfdir@/ganeti/instance-debootstrap/variants"}
 : ${GENERATE_CACHE:="yes"}
 : ${CLEAN_CACHE:="14"} # number of days to keep a cache file
-: ${PARTITION_ALIGNMENT:=2048} # sectors to align partition (1Mib default)
 if [ -z "$OS_API_VERSION" -o "$OS_API_VERSION" = "5" ]; then
   DEFAULT_PARTITION_STYLE="none"
 else
diff --git a/defaults b/defaults
index fdf28e5..b24aac9 100644
--- a/defaults
+++ b/defaults
@@ -74,9 +74,3 @@ CLEAN_CACHE="14"
 # Ganeti 1.2 (os api version 5)
 # PARTITION_STYLE="none"
 
-# PARTITION_ALIGNMENT: the alignment of the partitions in sectors
-# (512B); this defaults to 1MiB to give grub enough space for
-# embedding and for better alignment with modern media (HDDs and
-# SSDs), feel free to increase it if your media has even bigger
-# allocation blocks
-# PARTITION_ALIGNMENT=2048