Merge pull request #123 from marineam/align

Align partitions

build_library/cgpt.py

@@ -12,7 +12,7 @@ import uuid
 from optparse import OptionParser
 
 # First sector we can use.
-START_SECTOR = 64
+GPT_RESERVED_SECTORS = 34
 
 class ConfigNotFound(Exception):
   pass
@@ -36,7 +36,7 @@ def LoadPartitionConfig(filename):
   valid_keys = set(('_comment', 'metadata', 'layouts'))
   valid_layout_keys = set((
       '_comment', 'type', 'num', 'label', 'blocks', 'block_size', 'fs_blocks',
-      'fs_block_size', 'features', 'uuid'))
+      'fs_block_size', 'features', 'uuid', 'alignment'))
 
   if not os.path.exists(filename):
     raise ConfigNotFound('Partition config %s was not found!' % filename)
@@ -45,9 +45,14 @@ def LoadPartitionConfig(filename):
 
   try:
     metadata = config['metadata']
-    for key in ('block_size', 'fs_block_size'):
+    for key in ('alignment', 'block_size', 'fs_block_size'):
       metadata[key] = int(metadata[key])
 
+    # Sometimes qemu-img expects disks sizes aligned to 64k
+    align_bytes = metadata['alignment'] * metadata['block_size']
+    if align_bytes < 65536 or align_bytes % 65536 != 0:
+      raise InvalidLayout('Invalid alignment, 64KB or better required')
+
     unknown_keys = set(config.keys()) - valid_keys
     if unknown_keys:
       raise InvalidLayout('Unknown items: %r' % unknown_keys)
@@ -67,6 +72,7 @@ def LoadPartitionConfig(filename):
             if not s in part:
               raise InvalidLayout('Layout "%s" missing "%s"' % (layout_name, s))
 
+        part['alignment'] = int(part.get('alignment', metadata['alignment']))
         part['blocks'] = int(part['blocks'])
         part['bytes'] = part['blocks'] * metadata['block_size']
 
@@ -220,17 +226,30 @@ def WritePartitionTable(options, image_type, layout_filename, disk_filename):
   def Cgpt(*args):
     subprocess.check_call(['cgpt'] + [str(a) for a in args])
 
+  def Align(count, alignment):
+    offset = count % alignment
+    if offset:
+      count += alignment - offset
+    return count
+
   config = LoadPartitionConfig(layout_filename)
+  metadata = config['metadata']
   partitions = GetPartitionTable(options, config, image_type)
-  disk_block_count = START_SECTOR * config['metadata']['block_size']
+  disk_block_count = GPT_RESERVED_SECTORS
 
   for partition in partitions:
+    disk_block_count = Align(disk_block_count, partition['alignment'])
     disk_block_count += partition['blocks']
 
-  sector = START_SECTOR
+  disk_block_count += GPT_RESERVED_SECTORS
+  # Sometimes qemu-img expects disks sizes aligned to 64k
+  disk_block_count = Align(disk_block_count, config['metadata']['alignment'])
+
   Cgpt('create', '-c', '-s', disk_block_count, disk_filename)
 
+  sector = GPT_RESERVED_SECTORS
   for partition in partitions:
+    sector = Align(sector, partition['alignment'])
     if partition['type'] != 'blank':
       Cgpt('add', '-i', partition['num'],
                   '-b', sector,

build_library/legacy_disk_layout.json

@@ -1,6 +1,7 @@
 {
   "_comment": "See http://www.chromium.org/chromium-os/building-chromium-os/disk-layout-format",
   "metadata":{
+    "alignment": 2048,
     "block_size": 512,
     "fs_block_size": 4096
   },
@@ -38,8 +39,8 @@
         "num": 5,
         "label":"ROOT-C",
         "uuid":"d82521b4-07ac-4f1c-8840-ddefedc332f3",
-        "type":"coreos-rootfs",
-        "blocks":"1"
+        "type":"blank",
+        "blocks":"0"
       },
       {
         "num": 6,
@@ -49,15 +50,15 @@
       },
       {
         "num": 7,
-        "type":"coreos-reserved",
+        "type":"blank",
         "label":"coreos-reserved",
-        "blocks":"1"
+        "blocks":"0"
       },
       {
         "num": 8,
-        "type":"coreos-reserved",
+        "type":"blank",
         "label":"coreos-reserved",
-        "blocks":"1"
+        "blocks":"0"
       },
       {
         "num": 9,