Update libsnapshot to handle partial update

For partial update, the payload will not include all dynamic
partitions on the device, update the logic libsnapshot to better
handle such case.

Bug: 157778739
Test: run a partial OTA, unit tests pass

Change-Id: I4339a81ed31161bab3ba9666c1d05fb8bf57dbf9

fs_mgr/libsnapshot/snapshot.cpp

@@ -2277,6 +2277,10 @@ Return SnapshotManager::CreateUpdateSnapshotsInternal(
         auto operations_it = install_operation_map.find(target_partition->name());
         if (operations_it != install_operation_map.end()) {
             cow_creator->operations = operations_it->second;
+        } else {
+            LOG(INFO) << target_partition->name()
+                      << " isn't included in the payload, skipping the cow creation.";
+            continue;
         }
 
         cow_creator->extra_extents.clear();

fs_mgr/libsnapshot/snapshot_metadata_updater.cpp

@@ -62,6 +62,8 @@ SnapshotMetadataUpdater::SnapshotMetadataUpdater(MetadataBuilder* builder, uint3
                                                std::string(it->second) + target_suffix_, &p});
         }
     }
+
+    partial_update_ = manifest.partial_update();
 }
 
 bool SnapshotMetadataUpdater::ShrinkPartitions() const {
@@ -82,6 +84,18 @@ bool SnapshotMetadataUpdater::ShrinkPartitions() const {
 }
 
 bool SnapshotMetadataUpdater::DeletePartitions() const {
+    // For partial update, not all dynamic partitions are included in the payload.
+    // TODO(xunchang) delete the untouched partitions whose group is in the payload.
+    // e.g. Delete vendor in the following scenario
+    // On device:
+    //   Group A: system, vendor
+    // In payload:
+    //   Group A: system
+    if (partial_update_) {
+        LOG(INFO) << "Skip deleting partitions for partial update";
+        return true;
+    }
+
     std::vector<std::string> partitions_to_delete;
     // Don't delete partitions in groups where the group name doesn't have target_suffix,
     // e.g. default.
@@ -139,6 +153,11 @@ bool SnapshotMetadataUpdater::ShrinkGroups() const {
 }
 
 bool SnapshotMetadataUpdater::DeleteGroups() const {
+    if (partial_update_) {
+        LOG(INFO) << "Skip deleting groups for partial update";
+        return true;
+    }
+
     std::vector<std::string> existing_groups = builder_->ListGroups();
     for (const auto& existing_group_name : existing_groups) {
         // Don't delete groups without target suffix, e.g. default.

fs_mgr/libsnapshot/snapshot_metadata_updater.h

@@ -79,6 +79,7 @@ class SnapshotMetadataUpdater {
     const std::string target_suffix_;
     std::vector<Group> groups_;
     std::vector<Partition> partitions_;
+    bool partial_update_{false};
 };
 
 }  // namespace snapshot

fs_mgr/libsnapshot/update_engine/update_metadata.proto

@@ -77,4 +77,5 @@ message DynamicPartitionMetadata {
 message DeltaArchiveManifest {
     repeated PartitionUpdate partitions = 13;
     optional DynamicPartitionMetadata dynamic_partition_metadata = 15;
+    optional bool partial_update = 16;
 }