Merge "libsnapshot:snapuserd: Fix memory leak" am: ef8d3c39b5

Original change: https://android-review.googlesource.com/c/platform/system/core/+/1662684

Change-Id: Ic8b4f2221f14f40bed88d0957b6700caef89db36

fs_mgr/libsnapshot/snapuserd.h

@@ -158,6 +158,7 @@ class Snapuserd : public std::enable_shared_from_this<Snapuserd> {
     bool CommitMerge(int num_merge_ops);
 
     void CloseFds() { cow_fd_ = {}; }
+    void FreeResources() { worker_threads_.clear(); }
     size_t GetMetadataAreaSize() { return vec_.size(); }
     void* GetExceptionBuffer(size_t i) { return vec_[i].get(); }
 

fs_mgr/libsnapshot/snapuserd_server.cpp

@@ -219,7 +219,13 @@ void SnapuserdServer::RunThread(std::shared_ptr<DmUserHandler> handler) {
         auto iter = FindHandler(&lock, handler->misc_name());
         if (iter == dm_users_.end()) {
             // RemoveAndJoinHandler() already removed us from the list, and is
-            // now waiting on a join(), so just return.
+            // now waiting on a join(), so just return. Additionally, release
+            // all the resources held by snapuserd object which are shared
+            // by worker threads. This should be done when the last reference
+            // of "handler" is released; but we will explicitly release here
+            // to make sure snapuserd object is freed as it is the biggest
+            // consumer of memory in the daemon.
+            handler->FreeResources();
             LOG(INFO) << "Exiting handler thread to allow for join: " << misc_name;
             return;
         }

fs_mgr/libsnapshot/snapuserd_server.h

@@ -49,7 +49,15 @@ class DmUserHandler {
   public:
     explicit DmUserHandler(std::shared_ptr<Snapuserd> snapuserd);
 
-    void FreeResources() { snapuserd_ = nullptr; }
+    void FreeResources() {
+        // Each worker thread holds a reference to snapuserd.
+        // Clear them so that all the resources
+        // held by snapuserd is released
+        if (snapuserd_) {
+            snapuserd_->FreeResources();
+            snapuserd_ = nullptr;
+        }
+    }
     const std::shared_ptr<Snapuserd>& snapuserd() const { return snapuserd_; }
     std::thread& thread() { return thread_; }