From 6079cd014a65dca5cf6d2e3eaee5ccd85605d19b Mon Sep 17 00:00:00 2001
From: Yifan Hong <elsk@google.com>
Date: Fri, 2 Aug 2019 18:15:40 -0700
Subject: [PATCH] liblp: refactor MetadataBuilder::NewForUpdate

Move the logic for retrofit DAP to its new function. The new flow
in NewForUpdate is:
    metadata = ReadMetadata();
    if (retrofit dap) UpdateMetadataForOtherSuper(metadata)
    return metadata;

Test: liblp_test_static
Change-Id: I6890fff3a7c44ebe2004de96b2ccbe1e8ce37546
---
 fs_mgr/liblp/builder.cpp             | 31 +++++++++++++++++++---------
 fs_mgr/liblp/include/liblp/builder.h |  3 +++
 2 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/fs_mgr/liblp/builder.cpp b/fs_mgr/liblp/builder.cpp
index 247e3a92c..777743ca2 100644
--- a/fs_mgr/liblp/builder.cpp
+++ b/fs_mgr/liblp/builder.cpp
@@ -159,16 +159,27 @@ std::unique_ptr<MetadataBuilder> MetadataBuilder::NewForUpdate(const IPartitionO
         return nullptr;
     }
 
-    // On non-retrofit devices there is only one location for metadata: the
-    // super partition. update_engine will remove and resize partitions as
-    // needed. On the other hand, for retrofit devices, we'll need to
-    // translate block device and group names to update their slot suffixes.
+    // On retrofit DAP devices, modify the metadata so that it is suitable for being written
+    // to the target slot later. We detect retrofit DAP devices by checking the super partition
+    // name and system properties.
+    // See comments for UpdateMetadataForOtherSuper.
     auto super_device = GetMetadataSuperBlockDevice(*metadata.get());
-    if (GetBlockDevicePartitionName(*super_device) == "super" ||
-        !IsRetrofitDynamicPartitionsDevice()) {
-        return New(*metadata.get(), &opener);
+    if (GetBlockDevicePartitionName(*super_device) != "super" &&
+        IsRetrofitDynamicPartitionsDevice()) {
+        if (!UpdateMetadataForOtherSuper(metadata.get(), source_slot_number, target_slot_number)) {
+            return nullptr;
+        }
     }
 
+    return New(*metadata.get(), &opener);
+}
+
+// For retrofit DAP devices, there are (conceptually) two super partitions. We'll need to translate
+// block device and group names to update their slot suffixes.
+// (On the other hand, On non-retrofit DAP devices there is only one location for metadata: the
+// super partition. update_engine will remove and resize partitions as needed.)
+bool MetadataBuilder::UpdateMetadataForOtherSuper(LpMetadata* metadata, uint32_t source_slot_number,
+                                                  uint32_t target_slot_number) {
     // Clear partitions and extents, since they have no meaning on the target
     // slot. We also clear groups since they are re-added during OTA.
     metadata->partitions.clear();
@@ -188,7 +199,7 @@ std::unique_ptr<MetadataBuilder> MetadataBuilder::NewForUpdate(const IPartitionO
             // refers to a target or unknown block device.
             LERROR << "Invalid block device for slot " << source_slot_suffix << ": "
                    << partition_name;
-            return nullptr;
+            return false;
         }
         std::string new_name =
                 partition_name.substr(0, partition_name.size() - slot_suffix.size()) +
@@ -197,12 +208,12 @@ std::unique_ptr<MetadataBuilder> MetadataBuilder::NewForUpdate(const IPartitionO
         auto new_device = source_block_device;
         if (!UpdateBlockDevicePartitionName(&new_device, new_name)) {
             LERROR << "Partition name too long: " << new_name;
-            return nullptr;
+            return false;
         }
         metadata->block_devices.emplace_back(new_device);
     }
 
-    return New(*metadata.get(), &opener);
+    return true;
 }
 
 MetadataBuilder::MetadataBuilder() : auto_slot_suffixing_(false) {
diff --git a/fs_mgr/liblp/include/liblp/builder.h b/fs_mgr/liblp/include/liblp/builder.h
index a2294efd7..3b229bde5 100644
--- a/fs_mgr/liblp/include/liblp/builder.h
+++ b/fs_mgr/liblp/include/liblp/builder.h
@@ -345,6 +345,9 @@ class MetadataBuilder {
                                                     const std::vector<Interval>& free_list,
                                                     uint64_t sectors_needed) const;
 
+    static bool UpdateMetadataForOtherSuper(LpMetadata* metadata, uint32_t source_slot_number,
+                                            uint32_t target_slot_number);
+
     LpMetadataGeometry geometry_;
     LpMetadataHeader header_;
     std::vector<std::unique_ptr<Partition>> partitions_;