fix dropping column family bug

Summary: 1. db/db_impl.cc:2324 (DBImpl::BackgroundCompaction) should not raise bg_error_ when column family is dropped during compaction.

Test Plan: 1. db_stress

Reviewers: ljin, yhchiang, dhruba, igor, sdong

Reviewed By: igor

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D22653

db/db_impl.cc

@@ -2321,7 +2321,7 @@ Status DBImpl::BackgroundCompaction(bool* madeProgress,
 
   if (status.ok()) {
     // Done
-  } else if (shutting_down_.Acquire_Load()) {
+  } else if (status.IsShutdownInProgress()) {
     // Ignore compaction errors found during shutting down
   } else {
     Log(InfoLogLevel::WARN_LEVEL, options_.info_log, "Compaction error: %s",

include/rocksdb/status.h

@@ -96,7 +96,7 @@ class Status {
   // Returns true iff the status indicates Incomplete
   bool IsIncomplete() const { return code() == kIncomplete; }
 
-  // Returns true iff the status indicates Incomplete
+  // Returns true iff the status indicates Shutdown In progress
   bool IsShutdownInProgress() const { return code() == kShutdownInProgress; }
 
   bool IsTimedOut() const { return code() == kTimedOut; }