Fix calling GetCurrentMutableCFOptions in CompactionJob::ProcessKeyValueCompaction()

Summary: GetCurrentMutableCFOptions() can only be called when DB mutex is held so we cannot call it in CompactionJob::ProcessKeyValueCompaction() since it's not holding the db mutex

Test Plan: make check -j64

Reviewers: sdong, andrewkr

Reviewed By: andrewkr

Subscribers: andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D57471

db/column_family.h

@@ -209,7 +209,7 @@ class ColumnFamilyData {
   const ImmutableCFOptions* ioptions() const { return &ioptions_; }
   // REQUIRES: DB mutex held
   // This returns the MutableCFOptions used by current SuperVersion
-  // You shoul use this API to reference MutableCFOptions most of the time.
+  // You should use this API to reference MutableCFOptions most of the time.
   const MutableCFOptions* GetCurrentMutableCFOptions() const {
     return &(super_version_->mutable_cf_options);
   }

db/compaction_job.cc

@@ -669,6 +669,8 @@ void CompactionJob::ProcessKeyValueCompaction(SubcompactionState* sub_compact) {
   }
 
   ColumnFamilyData* cfd = sub_compact->compaction->column_family_data();
+  const MutableCFOptions* mutable_cf_options =
+      sub_compact->compaction->mutable_cf_options();
 
   // To build compression dictionary, we sample the first output file, assuming
   // it'll reach the maximum length, and then use the dictionary for compressing
@@ -680,8 +682,7 @@ void CompactionJob::ProcessKeyValueCompaction(SubcompactionState* sub_compact) {
       cfd->ioptions()->compression_opts.max_dict_bytes > 0) {
     const size_t kMaxSamples =
         cfd->ioptions()->compression_opts.max_dict_bytes >> kSampleLenShift;
-    const size_t kOutFileLen =
-        cfd->GetCurrentMutableCFOptions()->MaxFileSizeForLevel(
+    const size_t kOutFileLen = mutable_cf_options->MaxFileSizeForLevel(
         compact_->compaction->output_level());
     if (kOutFileLen != port::kMaxSizet) {
       const size_t kOutFileNumSamples = kOutFileLen >> kSampleLenShift;