Add the option to reserve headroom for partition images.

This is useful for devices with low disk space with different
build variants.

Bug: 37469715
Test: Regular image builds successfully, errors occur when
the headroom size is greater than available partition space.

Change-Id: I526cdd0f84981bbd16e3afcfe1cd7fc43dce98ef

core/Makefile

@@ -897,6 +897,7 @@ $(if $(BOARD_SYSTEMIMAGE_SQUASHFS_COMPRESSOR_OPT),$(hide) echo "system_squashfs_
 $(if $(BOARD_SYSTEMIMAGE_SQUASHFS_BLOCK_SIZE),$(hide) echo "system_squashfs_block_size=$(BOARD_SYSTEMIMAGE_SQUASHFS_BLOCK_SIZE)" >> $(1))
 $(if $(BOARD_SYSTEMIMAGE_SQUASHFS_DISABLE_4K_ALIGN),$(hide) echo "system_squashfs_disable_4k_align=$(BOARD_SYSTEMIMAGE_SQUASHFS_DISABLE_4K_ALIGN)" >> $(1))
 $(if $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SYSTEM_BASE_FS_PATH),$(hide) echo "system_base_fs_file=$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SYSTEM_BASE_FS_PATH)" >> $(1))
+$(if $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SYSTEM_HEADROOM),$(hide) echo "system_headroom=$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SYSTEM_HEADROOM)" >> $(1))
 $(if $(BOARD_USERDATAIMAGE_FILE_SYSTEM_TYPE),$(hide) echo "userdata_fs_type=$(BOARD_USERDATAIMAGE_FILE_SYSTEM_TYPE)" >> $(1))
 $(if $(BOARD_USERDATAIMAGE_PARTITION_SIZE),$(hide) echo "userdata_size=$(BOARD_USERDATAIMAGE_PARTITION_SIZE)" >> $(1))
 $(if $(BOARD_FLASH_LOGICAL_BLOCK_SIZE), $(hide) echo "flash_logical_block_size=$(BOARD_FLASH_LOGICAL_BLOCK_SIZE)" >> $(1))

core/product.mk

@@ -131,6 +131,7 @@ _product_var_list := \
     VENDOR_EXCEPTION_PATHS \
     PRODUCT_ART_USE_READ_BARRIER \
     PRODUCT_IOT \
+    PRODUCT_SYSTEM_HEADROOM \
 
 
 

core/product_config.mk

@@ -429,3 +429,7 @@ PRODUCT_IOT := \
 # Package list to apply enforcing RRO.
 PRODUCT_ENFORCE_RRO_TARGETS := \
     $(strip $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_ENFORCE_RRO_TARGETS))
+
+# Add reserved headroom to a system image.
+PRODUCT_SYSTEM_HEADROOM := \
+    $(strip $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SYSTEM_HEADROOM))

tools/releasetools/build_image.py

@@ -493,11 +493,11 @@ def BuildImage(in_dir, prop_dict, out_file, target_out=None):
     shutil.rmtree(staging_system, ignore_errors=True)
     shutil.copytree(origin_in, staging_system, symlinks=True)
 
-  reserved_blocks = prop_dict.get("has_ext4_reserved_blocks") == "true"
+  has_reserved_blocks = prop_dict.get("has_ext4_reserved_blocks") == "true"
   ext4fs_output = None
 
   try:
-    if reserved_blocks and fs_type.startswith("ext4"):
+    if fs_type.startswith("ext4"):
       (ext4fs_output, exit_code) = RunCommand(build_command)
     else:
       (_, exit_code) = RunCommand(build_command)
@@ -518,7 +518,9 @@ def BuildImage(in_dir, prop_dict, out_file, target_out=None):
   # not writable even with root privilege. It only affects devices using
   # file-based OTA and a kernel version of 3.10 or greater (currently just
   # sprout).
-  if reserved_blocks and fs_type.startswith("ext4"):
+  # Separately, check if there's enough headroom space available. This is useful for
+  # devices with low disk space that have system image variation between builds.
+  if (has_reserved_blocks or "partition_headroom" in prop_dict) and fs_type.startswith("ext4"):
     assert ext4fs_output is not None
     ext4fs_stats = re.compile(
         r'Created filesystem with .* (?P<used_blocks>[0-9]+)/'
@@ -526,14 +528,21 @@ def BuildImage(in_dir, prop_dict, out_file, target_out=None):
     m = ext4fs_stats.match(ext4fs_output.strip().split('\n')[-1])
     used_blocks = int(m.groupdict().get('used_blocks'))
     total_blocks = int(m.groupdict().get('total_blocks'))
-    reserved_blocks = min(4096, int(total_blocks * 0.02))
-    adjusted_blocks = total_blocks - reserved_blocks
+    reserved_blocks = 0
+    headroom_blocks = 0
+    adjusted_blocks = total_blocks
+    if has_reserved_blocks:
+      reserved_blocks = min(4096, int(total_blocks * 0.02))
+      adjusted_blocks -= reserved_blocks
+    if "partition_headroom" in prop_dict:
+      headroom_blocks = int(prop_dict.get('partition_headroom')) / BLOCK_SIZE
+      adjusted_blocks -= headroom_blocks
     if used_blocks > adjusted_blocks:
       mount_point = prop_dict.get("mount_point")
       print("Error: Not enough room on %s (total: %d blocks, used: %d blocks, "
-            "reserved: %d blocks, available: %d blocks)" % (
+            "reserved: %d blocks, headroom: %d blocks, available: %d blocks)" % (
                 mount_point, total_blocks, used_blocks, reserved_blocks,
-                adjusted_blocks))
+                headroom_blocks, adjusted_blocks))
       return False
 
   if not fs_spans_partition:
@@ -614,9 +623,10 @@ def ImagePropFromGlobalDict(glob_dict, mount_point):
   d["mount_point"] = mount_point
   if mount_point == "system":
     copy_prop("fs_type", "fs_type")
-    # Copy the generic sysetem fs type first, override with specific one if
+    # Copy the generic system fs type first, override with specific one if
     # available.
     copy_prop("system_fs_type", "fs_type")
+    copy_prop("system_headroom", "partition_headroom")
     copy_prop("system_size", "partition_size")
     copy_prop("system_journal_size", "journal_size")
     copy_prop("system_verity_block_device", "verity_block_device")