liblp: MetadataBuilder::GetBlockDevicePartitionName

Allow to retrieve name of a block device partition at
a certain index. If the index is out of range, return
empty string.

This is needed for an hypothetical edge case when an
intersection of two LinearExtent needs to be computed,
and the two metadata have a different list of block
device names. In reality, Virtual A/B devices are always
launched with dynamic partitions, so it will always return
"super" for index 0 and "" otherwise.

Test: liblp_test_static
Bug: 135752105

Change-Id: I9ea59edefdc41d0e69e3644aa2452676372938b4

2 files changed, 18 insertions, 7 deletions

diff --git a/fs_mgr/liblp/builder.cpp b/fs_mgr/liblp/builder.cpp
index 33ea8c5927..e789524f5f 100644
--- a/fs_mgr/liblp/builder.cpp
+++ b/fs_mgr/liblp/builder.cpp
@@ -140,7 +140,7 @@ std::unique_ptr<MetadataBuilder> MetadataBuilder::New(const LpMetadata& metadata
     }
     if (opener) {
         for (size_t i = 0; i < builder->block_devices_.size(); i++) {
-            std::string partition_name = GetBlockDevicePartitionName(builder->block_devices_[i]);
+            std::string partition_name = builder->GetBlockDevicePartitionName(i);
             BlockDeviceInfo device_info;
             if (opener->GetInfo(partition_name, &device_info)) {
                 builder->UpdateBlockDeviceInfo(i, device_info);
@@ -164,7 +164,7 @@ std::unique_ptr<MetadataBuilder> MetadataBuilder::NewForUpdate(const IPartitionO
     // name and system properties.
     // See comments for UpdateMetadataForOtherSuper.
     auto super_device = GetMetadataSuperBlockDevice(*metadata.get());
-    if (GetBlockDevicePartitionName(*super_device) != "super" &&
+    if (android::fs_mgr::GetBlockDevicePartitionName(*super_device) != "super" &&
         IsRetrofitDynamicPartitionsDevice()) {
         if (!UpdateMetadataForOtherSuper(metadata.get(), source_slot_number, target_slot_number)) {
             return nullptr;
@@ -192,7 +192,8 @@ bool MetadataBuilder::UpdateMetadataForOtherSuper(LpMetadata* metadata, uint32_t
     // Translate block devices.
     auto source_block_devices = std::move(metadata->block_devices);
     for (const auto& source_block_device : source_block_devices) {
-        std::string partition_name = GetBlockDevicePartitionName(source_block_device);
+        std::string partition_name =
+                android::fs_mgr::GetBlockDevicePartitionName(source_block_device);
         std::string slot_suffix = GetPartitionSlotSuffix(partition_name);
         if (slot_suffix.empty() || slot_suffix != source_slot_suffix) {
             // This should never happen. It means that the source metadata
@@ -375,7 +376,7 @@ bool MetadataBuilder::Init(const std::vector<BlockDeviceInfo>& block_devices,
             block_devices_.emplace_back(out);
         }
     }
-    if (GetBlockDevicePartitionName(block_devices_[0]) != super_partition) {
+    if (GetBlockDevicePartitionName(0) != super_partition) {
         LERROR << "No super partition was specified.";
         return false;
     }
@@ -849,7 +850,7 @@ uint64_t MetadataBuilder::AlignSector(const LpMetadataBlockDevice& block_device,
 bool MetadataBuilder::FindBlockDeviceByName(const std::string& partition_name,
                                             uint32_t* index) const {
     for (size_t i = 0; i < block_devices_.size(); i++) {
-        if (GetBlockDevicePartitionName(block_devices_[i]) == partition_name) {
+        if (GetBlockDevicePartitionName(i) == partition_name) {
             *index = i;
             return true;
         }
@@ -974,7 +975,8 @@ static bool CompareBlockDevices(const LpMetadataBlockDevice& first,
     // Note: we don't compare alignment, since it's a performance thing and
     // won't affect whether old extents continue to work.
     return first.first_logical_sector == second.first_logical_sector && first.size == second.size &&
-           GetBlockDevicePartitionName(first) == GetBlockDevicePartitionName(second);
+           android::fs_mgr::GetBlockDevicePartitionName(first) ==
+                   android::fs_mgr::GetBlockDevicePartitionName(second);
 }
 
 bool MetadataBuilder::ImportPartitions(const LpMetadata& metadata,
@@ -1057,7 +1059,7 @@ bool MetadataBuilder::IsRetrofitDynamicPartitionsDevice() {
 }
 
 bool MetadataBuilder::IsRetrofitMetadata() const {
-    return GetBlockDevicePartitionName(block_devices_[0]) != LP_METADATA_DEFAULT_PARTITION_NAME;
+    return GetBlockDevicePartitionName(0) != LP_METADATA_DEFAULT_PARTITION_NAME;
 }
 
 bool MetadataBuilder::AddLinearExtent(Partition* partition, const std::string& block_device,
@@ -1121,5 +1123,11 @@ bool MetadataBuilder::ChangeGroupSize(const std::string& group_name, uint64_t ma
     return true;
 }
 
+std::string MetadataBuilder::GetBlockDevicePartitionName(uint64_t index) const {
+    return index < block_devices_.size()
+                   ? android::fs_mgr::GetBlockDevicePartitionName(block_devices_[index])
+                   : "";
+}
+
 }  // namespace fs_mgr
 }  // namespace android
diff --git a/fs_mgr/liblp/include/liblp/builder.h b/fs_mgr/liblp/include/liblp/builder.h
index d2a206be46..1f7029ece4 100644
--- a/fs_mgr/liblp/include/liblp/builder.h
+++ b/fs_mgr/liblp/include/liblp/builder.h
@@ -287,6 +287,9 @@ class MetadataBuilder {
     // Return true if a block device is found, else false.
     bool HasBlockDevice(const std::string& partition_name) const;
 
+    // Return the name of the block device at |index|.
+    std::string GetBlockDevicePartitionName(uint64_t index) const;
+
   private:
     MetadataBuilder();
     MetadataBuilder(const MetadataBuilder&) = delete;