liblp: Add a helper method for upgrading metadata on retrofit devices.

This adds a new MetadataBuilder constructor, NewForUpdate, that can be
used by update_engine to simplify upgrading metadata. It is safe to call
whether or not the device is a retrofit. If the metadata has block
devices assigned to a specific slot, and that slot matches the slot
suffix, it will ensure that an equivalent entry exists for the alternate
slot.

Thus, if the source slot is _a and the target slot is _b, and the
metadata has "system_a" as a block device but not "system_b", this will
automatically add "system_b" as a block device.

Bug: 116802789
Test: liblp_test gtest
Change-Id: Ie89d4dbf4c708b5705e658220227ebf33fcb1930

1 files changed, 39 insertions, 0 deletions

diff --git a/fs_mgr/liblp/io_test.cpp b/fs_mgr/liblp/io_test.cpp
index 5f0d9c812..9acf23e8e 100644
--- a/fs_mgr/liblp/io_test.cpp
+++ b/fs_mgr/liblp/io_test.cpp
@@ -649,3 +649,42 @@ TEST(liblp, AutoSlotSuffixing) {
     ASSERT_EQ(metadata->block_devices.size(), static_cast<size_t>(1));
     EXPECT_EQ(GetBlockDevicePartitionName(metadata->block_devices[0]), "super_a");
 }
+
+TEST(liblp, UpdateRetrofit) {
+    unique_ptr<MetadataBuilder> builder = CreateDefaultBuilder();
+    ASSERT_NE(builder, nullptr);
+    ASSERT_TRUE(AddDefaultPartitions(builder.get()));
+    builder->SetAutoSlotSuffixing();
+
+    auto fd = CreateFakeDisk();
+    ASSERT_GE(fd, 0);
+
+    // Note: we bind the same fd to both names, since we want to make sure the
+    // exact same bits are getting read back in each test.
+    TestPartitionOpener opener({{"super_a", fd}, {"super_b", fd}},
+                               {{"super_a", kSuperInfo}, {"super_b", kSuperInfo}});
+    auto exported = builder->Export();
+    ASSERT_NE(exported, nullptr);
+    ASSERT_TRUE(FlashPartitionTable(opener, "super_a", *exported.get()));
+
+    builder = MetadataBuilder::NewForUpdate(opener, "super_a", 0, 1);
+    ASSERT_NE(builder, nullptr);
+    auto updated = builder->Export();
+    ASSERT_NE(updated, nullptr);
+    ASSERT_EQ(updated->block_devices.size(), static_cast<size_t>(2));
+    EXPECT_EQ(GetBlockDevicePartitionName(updated->block_devices[0]), "super_a");
+    EXPECT_EQ(GetBlockDevicePartitionName(updated->block_devices[1]), "super_b");
+}
+
+TEST(liblp, UpdateNonRetrofit) {
+    unique_fd fd = CreateFlashedDisk();
+    ASSERT_GE(fd, 0);
+
+    DefaultPartitionOpener opener(fd);
+    auto builder = MetadataBuilder::NewForUpdate(opener, "super", 0, 1);
+    ASSERT_NE(builder, nullptr);
+    auto updated = builder->Export();
+    ASSERT_NE(updated, nullptr);
+    ASSERT_EQ(updated->block_devices.size(), static_cast<size_t>(1));
+    EXPECT_EQ(GetBlockDevicePartitionName(updated->block_devices[0]), "super");
+}