From 4d74c72d99e6646cc6a210e6ea50a2e60e333d2c Mon Sep 17 00:00:00 2001
From: Anders Ingemann <anders@ingemann.de>
Date: Mon, 19 Jan 2015 01:22:12 +0100
Subject: [PATCH] Simplify GPT a little by explicitly taking care of the GPT
 primary & secondary Do the math for the GPT offset a little differently

---
 bootstrapvz/base/fs/partitionmaps/gpt.py | 34 +++++++++++-------------
 1 file changed, 16 insertions(+), 18 deletions(-)

diff --git a/bootstrapvz/base/fs/partitionmaps/gpt.py b/bootstrapvz/base/fs/partitionmaps/gpt.py
index be54c32..a9bf06e 100644
--- a/bootstrapvz/base/fs/partitionmaps/gpt.py
+++ b/bootstrapvz/base/fs/partitionmaps/gpt.py
@@ -24,12 +24,18 @@ class GPTPartitionMap(AbstractPartitionMap):
 		def last_partition():
 			return self.partitions[-1] if len(self.partitions) > 0 else None
 
-		# If we are using the grub bootloader we need to create an unformatted partition
-		# at the beginning of the map. Its size is 1007kb, which we will steal from the
-		# next partition.
+		# The first 34 sectors are reserved for the primary GPT
+		primary_gpt = PartitionGap(Sectors(34, sector_size), last_partition())
+		self.partitions.append(primary_gpt)
+
 		if bootloader == 'grub':
+			# If we are using the grub bootloader we need to create an unformatted partition
+			# at the beginning of the map. Its size is 1007kb, which seems to be chosen so that
+			# gpt_primary + grub = 1024KiB
+			# So lets just specify grub size as 1MiB - 34 sectors
 			from ..partitions.unformatted import UnformattedPartition
-			self.grub_boot = UnformattedPartition(Sectors('1007KiB', sector_size), last_partition())
+			grub_size = Sectors('1MiB', sector_size) - primary_gpt.size
+			self.grub_boot = UnformattedPartition(grub_size, last_partition())
 			# Mark the partition as a bios_grub partition
 			self.grub_boot.flags.append('bios_grub')
 			self.partitions.append(self.grub_boot)
@@ -48,22 +54,14 @@ class GPTPartitionMap(AbstractPartitionMap):
 		                         'root', last_partition())
 		self.partitions.append(self.root)
 
-		# We need to move the first partition to make space for the gpt offset
-		gpt_offset = Sectors('17KiB', sector_size)
-		self.partitions[0].offset += gpt_offset
+		# The last 34 sectors are reserved for the secondary GPT
+		secondary_gpt = PartitionGap(Sectors(34, sector_size), last_partition())
+		self.partitions.append(secondary_gpt)
 
+		# reduce the size of the root partition so that the overall volume size is not exceeded
+		self.root.size -= primary_gpt.size + secondary_gpt.size
 		if hasattr(self, 'grub_boot'):
-			# grub_boot should not increase the size of the volume,
-			# so we reduce the size of the succeeding partition.
-			# gpt_offset is included here, because of the offset we added above (grub_boot is partition[0])
-			self.partitions[1].size -= self.grub_boot.get_end()
-		else:
-			# Avoid increasing the volume size because of gpt_offset
-			self.partitions[0].size -= gpt_offset
-
-		# Leave the last sector unformatted
-		self.partitions[-1].size -= 1
-		self.partitions.append(PartitionGap(Sectors(1, sector_size), last_partition()))
+			self.root.size -= self.grub_boot.size
 
 		super(GPTPartitionMap, self).__init__(bootloader)