Fix NewRandomRWFile and ReuseWritableFile in KeyManagedEncryptedEnv (#6)

apache/incubator-pegasus#1575

Cherry-pick from
tikv@2360562

Summary:
Fix NewRandomRWFile and ReuseWritableFile misuse of `GetFile()` and
`NewFile()`. See inline comments.

Test Plan:
manual test with tikv

Signed-off-by: Yi Wu <yiwu@pingcap.com>

Co-authored-by: yiwu-arbug <yiwu@pingcap.com>

encryption/encryption.cc

@@ -361,7 +361,10 @@ Status KeyManagedEncryptedEnv::ReuseWritableFile(
     const std::string& fname, const std::string& old_fname,
     std::unique_ptr<WritableFile>* result, const EnvOptions& options) {
   FileEncryptionInfo file_info;
-  Status s = key_manager_->GetFile(fname, &file_info);
+  // ReuseWritableFile is only used in the context of rotating WAL file and
+  // reuse them. Old content is discardable and new WAL records are to
+  // overwrite the file. So NewFile() should be called.
+  Status s = key_manager_->NewFile(fname, &file_info);
   if (!s.ok()) {
     return s;
   }
@@ -389,7 +392,10 @@ Status KeyManagedEncryptedEnv::NewRandomRWFile(
     const std::string& fname, std::unique_ptr<RandomRWFile>* result,
     const EnvOptions& options) {
   FileEncryptionInfo file_info;
-  Status s = key_manager_->NewFile(fname, &file_info);
+  // NewRandomRWFile is only used in the context of external file ingestion,
+  // for rewriting global seqno. So it should call GetFile() instead of
+  // NewFile().
+  Status s = key_manager_->GetFile(fname, &file_info);
   if (!s.ok()) {
     return s;
   }