diff --git a/base/include/android-base/result.h b/base/include/android-base/result.h
index 897c48f..4a8e1ef 100644
--- a/base/include/android-base/result.h
+++ b/base/include/android-base/result.h
@@ -81,8 +81,7 @@
 
 struct ResultError {
   template <typename T>
-  ResultError(T&& message, int code)
-      : message_(std::forward<T>(message)), code_(code) {}
+  ResultError(T&& message, int code) : message_(std::forward<T>(message)), code_(code) {}
 
   template <typename T>
   operator android::base::expected<T, ResultError>() {
@@ -122,18 +121,16 @@
 
   template <typename T>
   Error& operator<<(T&& t) {
+    if constexpr (std::is_same_v<std::remove_cv_t<std::remove_reference_t<T>>, ResultError>) {
+      errno_ = t.code();
+      return (*this) << t.message();
+    }
     int saved = errno;
     ss_ << t;
     errno = saved;
     return *this;
   }
 
-  Error& operator<<(const ResultError& result_error) {
-    (*this) << result_error.message();
-    errno_ = result_error.code();
-    return *this;
-  }
-
   const std::string str() const {
     std::string str = ss_.str();
     if (append_errno_) {
diff --git a/base/result_test.cpp b/base/result_test.cpp
index 72f97f4..e864b97 100644
--- a/base/result_test.cpp
+++ b/base/result_test.cpp
@@ -143,8 +143,8 @@
   ASSERT_FALSE(result2);
   ASSERT_FALSE(result2.has_value());
 
-  EXPECT_EQ(0, result.error().code());
-  EXPECT_EQ(error_text, result.error().message());
+  EXPECT_EQ(0, result2.error().code());
+  EXPECT_EQ(error_text, result2.error().message());
 }
 
 TEST(result, result_error_through_ostream) {
@@ -159,8 +159,8 @@
   ASSERT_FALSE(result2);
   ASSERT_FALSE(result2.has_value());
 
-  EXPECT_EQ(0, result.error().code());
-  EXPECT_EQ(error_text, result.error().message());
+  EXPECT_EQ(0, result2.error().code());
+  EXPECT_EQ(error_text, result2.error().message());
 }
 
 TEST(result, result_errno_error_through_ostream) {
@@ -179,8 +179,8 @@
   ASSERT_FALSE(result2);
   ASSERT_FALSE(result2.has_value());
 
-  EXPECT_EQ(test_errno, result.error().code());
-  EXPECT_EQ(error_text + ": " + strerror(test_errno), result.error().message());
+  EXPECT_EQ(test_errno, result2.error().code());
+  EXPECT_EQ(error_text + ": " + strerror(test_errno), result2.error().message());
 }
 
 TEST(result, constructor_forwarding) {
diff --git a/fastboot/device/commands.cpp b/fastboot/device/commands.cpp
index 1b09f79..2e9c2d6 100644
--- a/fastboot/device/commands.cpp
+++ b/fastboot/device/commands.cpp
@@ -94,7 +94,7 @@
             {FB_VAR_HAS_SLOT, {GetHasSlot, GetAllPartitionArgsNoSlot}},
             {FB_VAR_SLOT_SUCCESSFUL, {GetSlotSuccessful, nullptr}},
             {FB_VAR_SLOT_UNBOOTABLE, {GetSlotUnbootable, nullptr}},
-            {FB_VAR_PARTITION_SIZE, {GetPartitionSize, GetAllPartitionArgsWithSlot}},
+            {FB_VAR_PARTITION_SIZE, {::GetPartitionSize, GetAllPartitionArgsWithSlot}},
             {FB_VAR_PARTITION_TYPE, {GetPartitionType, GetAllPartitionArgsWithSlot}},
             {FB_VAR_IS_LOGICAL, {GetPartitionIsLogical, GetAllPartitionArgsWithSlot}},
             {FB_VAR_IS_USERSPACE, {GetIsUserspace, nullptr}},
diff --git a/fs_mgr/liblp/builder_test.cpp b/fs_mgr/liblp/builder_test.cpp
index 46bfe92..45c3ede 100644
--- a/fs_mgr/liblp/builder_test.cpp
+++ b/fs_mgr/liblp/builder_test.cpp
@@ -106,6 +106,13 @@
     EXPECT_EQ(extent->num_sectors(), 32768 / LP_SECTOR_SIZE);
     EXPECT_EQ(extent->physical_sector(), 32);
 
+    auto exported = builder->Export();
+    ASSERT_NE(exported, nullptr);
+    ASSERT_EQ(FindPartition(*exported.get(), "not found"), nullptr);
+    auto entry = FindPartition(*exported.get(), "system");
+    ASSERT_NE(entry, nullptr);
+    ASSERT_EQ(GetPartitionSize(*exported.get(), *entry), 32768);
+
     // Test shrinking to 0.
     builder->ResizePartition(system, 0);
     EXPECT_EQ(system->size(), 0);
diff --git a/fs_mgr/liblp/include/liblp/liblp.h b/fs_mgr/liblp/include/liblp/liblp.h
index d3a7b93..135a1b3 100644
--- a/fs_mgr/liblp/include/liblp/liblp.h
+++ b/fs_mgr/liblp/include/liblp/liblp.h
@@ -107,6 +107,10 @@
 std::string SlotSuffixForSlotNumber(uint32_t slot_number);
 std::string GetPartitionSlotSuffix(const std::string& partition_name);
 
+// Helpers for common functions.
+const LpMetadataPartition* FindPartition(const LpMetadata& metadata, const std::string& name);
+uint64_t GetPartitionSize(const LpMetadata& metadata, const LpMetadataPartition& partition);
+
 }  // namespace fs_mgr
 }  // namespace android
 
diff --git a/fs_mgr/liblp/utility.cpp b/fs_mgr/liblp/utility.cpp
index 72a3c57..338b525 100644
--- a/fs_mgr/liblp/utility.cpp
+++ b/fs_mgr/liblp/utility.cpp
@@ -135,6 +135,24 @@
     return list;
 }
 
+const LpMetadataPartition* FindPartition(const LpMetadata& metadata, const std::string& name) {
+    for (const auto& partition : metadata.partitions) {
+        if (GetPartitionName(partition) == name) {
+            return &partition;
+        }
+    }
+    return nullptr;
+}
+
+uint64_t GetPartitionSize(const LpMetadata& metadata, const LpMetadataPartition& partition) {
+    uint64_t total_size = 0;
+    for (uint32_t i = 0; i < partition.num_extents; i++) {
+        const auto& extent = metadata.extents[partition.first_extent_index + i];
+        total_size += extent.num_sectors * LP_SECTOR_SIZE;
+    }
+    return total_size;
+}
+
 std::string GetPartitionSlotSuffix(const std::string& partition_name) {
     if (partition_name.size() <= 2) {
         return "";