From d4b0ac27604577075fc5f6e272a1340c6eaf6860 Mon Sep 17 00:00:00 2001
From: Islam AbdelRahman <tec@fb.com>
Date: Wed, 25 Jan 2017 14:03:49 -0800
Subject: [PATCH] Fix CompactFiles() bug when used with CompactionFilter using
 SuperVersion

Summary:
GetAndRefSuperVersion() should not be called again in the same thread before ReturnAndCleanupSuperVersion() is called.

If we have a compaction filter that is using DB::Get, This will happen
```
CompactFiles() {
  GetAndRefSuperVersion() // -- first call
    ..
    CompactionFilter() {
      GetAndRefSuperVersion() // -- second call
      ReturnAndCleanupSuperVersion()
    }
    ..
  ReturnAndCleanupSuperVersion()
}
```

We solve this issue in the same way Iterator is solving it, but using GetReferencedSuperVersion()

This was discovered in https://github.com/facebook/mysql-5.6/issues/427 by alxyang
Closes https://github.com/facebook/rocksdb/pull/1803

Differential Revision: D4460155

Pulled By: IslamAbdelRahman

fbshipit-source-id: 5e54322
---
 db/compact_files_test.cc | 55 ++++++++++++++++++++++++++++++++++++++++
 db/db_impl.cc            |  9 +++++--
 2 files changed, 62 insertions(+), 2 deletions(-)

diff --git a/db/compact_files_test.cc b/db/compact_files_test.cc
index 051cca8a4..76042b6e3 100644
--- a/db/compact_files_test.cc
+++ b/db/compact_files_test.cc
@@ -253,6 +253,61 @@ TEST_F(CompactFilesTest, CapturingPendingFiles) {
   delete db;
 }
 
+TEST_F(CompactFilesTest, CompactionFilterWithGetSv) {
+  class FilterWithGet : public CompactionFilter {
+   public:
+    virtual bool Filter(int level, const Slice& key, const Slice& value,
+                        std::string* new_value,
+                        bool* value_changed) const override {
+      if (db_ == nullptr) {
+        return true;
+      }
+      std::string res;
+      db_->Get(ReadOptions(), "", &res);
+      return true;
+    }
+
+    void SetDB(DB* db) {
+      db_ = db;
+    }
+
+    virtual const char* Name() const override { return "FilterWithGet"; }
+
+   private:
+    DB* db_;
+  };
+
+
+  std::shared_ptr<FilterWithGet> cf(new FilterWithGet());
+
+  Options options;
+  options.create_if_missing = true;
+  options.compaction_filter = cf.get();
+
+  DB* db = nullptr;
+  DestroyDB(db_name_, options);
+  Status s = DB::Open(options, db_name_, &db);
+  ASSERT_OK(s);
+
+  cf->SetDB(db);
+
+  // Write one L0 file
+  db->Put(WriteOptions(), "K1", "V1");
+  db->Flush(FlushOptions());
+
+  // Compact all L0 files using CompactFiles
+  rocksdb::ColumnFamilyMetaData meta;
+  db->GetColumnFamilyMetaData(&meta);
+  for (auto& file : meta.levels[0].files) {
+    std::string fname = file.db_path + "/" + file.name;
+    ASSERT_OK(
+        db->CompactFiles(rocksdb::CompactionOptions(), {fname}, 0));
+  }
+
+
+  delete db;
+}
+
 }  // namespace rocksdb
 
 int main(int argc, char** argv) {
diff --git a/db/db_impl.cc b/db/db_impl.cc
index e8e83626b..578fe7cbc 100644
--- a/db/db_impl.cc
+++ b/db/db_impl.cc
@@ -2149,7 +2149,7 @@ Status DBImpl::CompactFiles(
                        immutable_db_options_.info_log.get());
 
   // Perform CompactFiles
-  SuperVersion* sv = GetAndRefSuperVersion(cfd);
+  SuperVersion* sv = cfd->GetReferencedSuperVersion(&mutex_);
   {
     InstrumentedMutexLock l(&mutex_);
 
@@ -2161,7 +2161,12 @@ Status DBImpl::CompactFiles(
                          input_file_names, output_level,
                          output_path_id, &job_context, &log_buffer);
   }
-  ReturnAndCleanupSuperVersion(cfd, sv);
+  if (sv->Unref()) {
+    mutex_.Lock();
+    sv->Cleanup();
+    mutex_.Unlock();
+    delete sv;
+  }
 
   // Find and delete obsolete files
   {