Flush Buffered Info Logs Before Doing Compaction (one line change)

Summary: Flushing log buffer earlier to avoid confusion of time holding the locks.

Test Plan: Should be safe as long as several related db test passes

Reviewers: haobo, igor, ljin

Reviewed By: igor

CC: nkg-, leveldb

Differential Revision: https://reviews.facebook.net/D17493

db/db_impl.cc

@@ -2945,6 +2945,7 @@ Status DBImpl::DoCompactionWork(CompactionState* compact,
 
   // Release mutex while we're actually doing the compaction work
   mutex_.Unlock();
+  log_buffer->FlushBufferToLog();
 
   const uint64_t start_micros = env_->NowMicros();
   unique_ptr<Iterator> input(versions_->MakeInputIterator(compact->compaction));