Merge "libsnapshot: MapCowImage returns the COW device path"

3 files changed, 13 insertions, 12 deletions

diff --git a/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h b/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h
index fcaa73ad7..120340c21 100644
--- a/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h
+++ b/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h
@@ -19,6 +19,7 @@
 #include <chrono>
 #include <map>
 #include <memory>
+#include <optional>
 #include <ostream>
 #include <string>
 #include <string_view>
@@ -298,7 +299,8 @@ class SnapshotManager final {
                      std::string* dev_path);
 
     // Map a COW image that was previous created with CreateCowImage.
-    bool MapCowImage(const std::string& name, const std::chrono::milliseconds& timeout_ms);
+    std::optional<std::string> MapCowImage(const std::string& name,
+                                           const std::chrono::milliseconds& timeout_ms);
 
     // Remove the backing copy-on-write image and snapshot states for the named snapshot. The
     // caller is responsible for ensuring that the snapshot is unmapped.
diff --git a/fs_mgr/libsnapshot/snapshot.cpp b/fs_mgr/libsnapshot/snapshot.cpp
index 48a94e4f3..2c5eed11e 100644
--- a/fs_mgr/libsnapshot/snapshot.cpp
+++ b/fs_mgr/libsnapshot/snapshot.cpp
@@ -450,9 +450,9 @@ bool SnapshotManager::MapSnapshot(LockedFile* lock, const std::string& name,
     return true;
 }
 
-bool SnapshotManager::MapCowImage(const std::string& name,
-                                  const std::chrono::milliseconds& timeout_ms) {
-    if (!EnsureImageManager()) return false;
+std::optional<std::string> SnapshotManager::MapCowImage(
+        const std::string& name, const std::chrono::milliseconds& timeout_ms) {
+    if (!EnsureImageManager()) return std::nullopt;
     auto cow_image_name = GetCowImageDeviceName(name);
 
     bool ok;
@@ -468,10 +468,10 @@ bool SnapshotManager::MapCowImage(const std::string& name,
 
     if (ok) {
         LOG(INFO) << "Mapped " << cow_image_name << " to " << cow_dev;
-    } else {
-        LOG(ERROR) << "Could not map image device: " << cow_image_name;
+        return cow_dev;
     }
-    return ok;
+    LOG(ERROR) << "Could not map image device: " << cow_image_name;
+    return std::nullopt;
 }
 
 bool SnapshotManager::UnmapSnapshot(LockedFile* lock, const std::string& name) {
@@ -1443,7 +1443,7 @@ bool SnapshotManager::MapCowDevices(LockedFile* lock, const CreateLogicalPartiti
         auto remaining_time = GetRemainingTime(params.timeout_ms, begin);
         if (remaining_time.count() < 0) return false;
 
-        if (!MapCowImage(partition_name, remaining_time)) {
+        if (!MapCowImage(partition_name, remaining_time).has_value()) {
             LOG(ERROR) << "Could not map cow image for partition: " << partition_name;
             return false;
         }
diff --git a/fs_mgr/libsnapshot/snapshot_test.cpp b/fs_mgr/libsnapshot/snapshot_test.cpp
index a00829421..f6a47222a 100644
--- a/fs_mgr/libsnapshot/snapshot_test.cpp
+++ b/fs_mgr/libsnapshot/snapshot_test.cpp
@@ -254,12 +254,11 @@ class SnapshotTest : public ::testing::Test {
 
     AssertionResult MapCowImage(const std::string& name,
                                 const std::chrono::milliseconds& timeout_ms, std::string* path) {
-        if (!sm->MapCowImage(name, timeout_ms)) {
+        auto cow_image_path = sm->MapCowImage(name, timeout_ms);
+        if (!cow_image_path.has_value()) {
             return AssertionFailure() << "Cannot map cow image " << name;
         }
-        if (!dm_.GetDmDevicePathByName(name + "-cow-img"s, path)) {
-            return AssertionFailure() << "No path for " << name << "-cow-img";
-        }
+        *path = *cow_image_path;
         return AssertionSuccess();
     }