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
// 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));