libsnapshot:snapuserd: Terminate daemon after applying OTA.

When all threads are terminated, dm-user handler's are removed
from the list. When the last handler is removed, daemon is
shutdown gracefully.

Bug: 183652708
Test: 1: Apply full OTA and verify daemon is terminated; reapply the OTA
      to verify daemon is restarted again.
      2:  vts_libsnapshot_test

Signed-off-by: Akilesh Kailash <akailash@google.com>
Change-Id: Ibd41223fc0eba884993a533fcc95661f72805db2

fs_mgr/libsnapshot/include/libsnapshot/snapuserd_client.h

@@ -69,6 +69,8 @@ class SnapuserdClient {
     // must ONLY be called if the control device has already been deleted.
     bool WaitForDeviceDelete(const std::string& control_device);
 
+    void CloseConnection() { sockfd_ = {}; }
+
     // Detach snapuserd. This shuts down the listener socket, and will cause
     // snapuserd to gracefully exit once all handler threads have terminated.
     // This should only be used on first-stage instances of snapuserd.

fs_mgr/libsnapshot/snapshot.cpp

@@ -2297,6 +2297,17 @@ bool SnapshotManager::UnmapAllSnapshots(LockedFile* lock) {
             return false;
         }
     }
+
+    // Terminate the daemon and release the snapuserd_client_ object.
+    // If we need to re-connect with the daemon, EnsureSnapuserdConnected()
+    // will re-create the object and establish the socket connection.
+    if (snapuserd_client_) {
+        LOG(INFO) << "Shutdown snapuserd daemon";
+        snapuserd_client_->DetachSnapuserd();
+        snapuserd_client_->CloseConnection();
+        snapuserd_client_ = nullptr;
+    }
+
     return true;
 }
 

fs_mgr/libsnapshot/snapshot_test.cpp

@@ -2019,6 +2019,8 @@ TEST_F(SnapshotUpdateTest, MapAllSnapshots) {
 
     // Read bytes back and verify they match the cache.
     ASSERT_TRUE(IsPartitionUnchanged("sys_b"));
+
+    ASSERT_TRUE(sm->UnmapAllSnapshots());
 }
 
 TEST_F(SnapshotUpdateTest, CancelOnTargetSlot) {