From 06a2dcebea66153fc8efa6ccf7c77ada5c2896ff Mon Sep 17 00:00:00 2001
From: Zhichao Cao <zhichao@fb.com>
Date: Thu, 14 May 2020 14:56:10 -0700
Subject: [PATCH] Move checksum calculation ahead of memory copy (#6844)

Summary:
Originally, the checksum of appended data in writable file writer is calculated after the data is copied to the buffer. It will not be able to catch the bit flip happens during copy. Move the checksum calculation before it.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6844

Test Plan: pass make asan_check

Reviewed By: cheng-chang

Differential Revision: D21576726

Pulled By: zhichao-cao

fbshipit-source-id: 0a062a1f19886f6ea0d4e3f557e6f4b799773254
---
 file/writable_file_writer.cc | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/file/writable_file_writer.cc b/file/writable_file_writer.cc
index ec4e7c8c3..2f44f7f58 100644
--- a/file/writable_file_writer.cc
+++ b/file/writable_file_writer.cc
@@ -30,6 +30,9 @@ IOStatus WritableFileWriter::Append(const Slice& data) {
   TEST_KILL_RANDOM("WritableFileWriter::Append:0",
                    rocksdb_kill_odds * REDUCE_ODDS2);
 
+  // Calculate the checksum of appended data
+  CalculateFileChecksum(data);
+
   {
     IOSTATS_TIMER_GUARD(prepare_write_nanos);
     TEST_SYNC_POINT("WritableFileWriter::Append:BeforePrepareWrite");
@@ -89,7 +92,6 @@ IOStatus WritableFileWriter::Append(const Slice& data) {
   TEST_KILL_RANDOM("WritableFileWriter::Append:1", rocksdb_kill_odds);
   if (s.ok()) {
     filesize_ += data.size();
-    CalculateFileChecksum(data);
   }
   return s;
 }