[CF] Delete SuperVersion in a special function

Summary: Added a function DeleteSuperVersion that can be called in DBImpl destructor before PurgingObsoleteFiles. That way, PurgeObsoleteFiles will be able to delete all files held by alive super versions.

Test Plan: column_family_test with valgrind

Reviewers: dhruba, haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16545

db/column_family.cc

@@ -222,28 +222,6 @@ ColumnFamilyData::~ColumnFamilyData() {
   prev->next_ = next;
   next->prev_ = prev;
 
-  // Release SuperVersion reference kept in ThreadLocalPtr.
-  // This must be done outside of mutex_ since unref handler can lock mutex.
-  // It also needs to be done after FlushMemTable, which can trigger local_sv_
-  // access.
-  auto sv = static_cast<SuperVersion*>(local_sv_->Get());
-  if (sv != nullptr) {
-    auto mutex = sv->db_mutex;
-    mutex->Unlock();
-    delete local_sv_;
-    mutex->Lock();
-  } else {
-    delete local_sv_;
-  }
-
-  if (super_version_ != nullptr) {
-    bool is_last_reference __attribute__((unused));
-    is_last_reference = super_version_->Unref();
-    assert(is_last_reference);
-    super_version_->Cleanup();
-    delete super_version_;
-  }
-
   // it's nullptr for dummy CFD
   if (column_family_set_ != nullptr) {
     // remove from column_family_set
@@ -254,6 +232,8 @@ ColumnFamilyData::~ColumnFamilyData() {
     current_->Unref();
   }
 
+  DeleteSuperVersion();
+
   if (dummy_versions_ != nullptr) {
     // List must be empty
     assert(dummy_versions_->next_ == dummy_versions_);
@@ -330,6 +310,23 @@ void ColumnFamilyData::ResetThreadLocalSuperVersions() {
   }
 }
 
+void ColumnFamilyData::DeleteSuperVersion() {
+  if (super_version_ != nullptr) {
+    // Release SuperVersion reference kept in ThreadLocalPtr.
+    // This must be done outside of mutex_ since unref handler can lock mutex.
+    super_version_->db_mutex->Unlock();
+    local_sv_.reset();
+    super_version_->db_mutex->Lock();
+
+    bool is_last_reference __attribute__((unused));
+    is_last_reference = super_version_->Unref();
+    assert(is_last_reference);
+    super_version_->Cleanup();
+    delete super_version_;
+    super_version_ = nullptr;
+  }
+}
+
 ColumnFamilySet::ColumnFamilySet(const std::string& dbname,
                                  const DBOptions* db_options,
                                  const EnvOptions& storage_options,

db/column_family.h

@@ -180,6 +180,9 @@ class ColumnFamilyData {
                                     port::Mutex* db_mutex);
 
   void ResetThreadLocalSuperVersions();
+  // REQUIRED: db mutex held
+  // Do not access column family after calling this method
+  void DeleteSuperVersion();
 
   // A Flag indicating whether write needs to slowdown because of there are
   // too many number of level0 files.
@@ -227,7 +230,7 @@ class ColumnFamilyData {
 
   // Thread's local copy of SuperVersion pointer
   // This needs to be destructed before mutex_
-  ThreadLocalPtr* local_sv_;
+  std::unique_ptr<ThreadLocalPtr> local_sv_;
 
   // pointers for a circular linked list. we use it to support iterations
   // that can be concurrent with writes

db/db_impl.cc

@@ -300,6 +300,10 @@ DBImpl::~DBImpl() {
     bg_cv_.Wait();
   }
 
+  for (auto cfd : *versions_->GetColumnFamilySet()) {
+    cfd->DeleteSuperVersion();
+  }
+
   if (options_.allow_thread_local) {
     // Clean up obsolete files due to SuperVersion release.
     // (1) Need to delete to obsolete files before closing because RepairDB()
@@ -329,9 +333,11 @@ DBImpl::~DBImpl() {
     env_->UnlockFile(db_lock_);
   }
 
+  mutex_.Lock();
   // versions need to be destroyed before table_cache since it can hold
   // references to table_cache.
   versions_.reset();
+  mutex_.Unlock();
 
   LogFlush(options_.info_log);
 }