Fix file checksum mismatch due to padded bytes when block_align=true (#12542)

Summary:
**Context/Summary:**
When `BlockBasedTableOptions::block_align=true`, we pad bytes to align blocks https://github.com/facebook/rocksdb/blob/d41e568b1cc67e8a248dce7197b8a8aebaf3bb2f/table/block_based/block_based_table_builder.cc#L1415-L1421.
Those bytes are not included in generating the file checksum upon file creation. But `VerifyFileChecksums()` includes those bytes in generating the file check to compare against the checksum generating upon file creation. Therefore a file checksum mismatch is returned in `VerifyFileChecksums()`.

We decided to include those padded bytes in generating the checksum upon file creation.

Bonus: also fix surrounding code to use actual padded bytes for verification - see https://github.com/facebook/rocksdb/pull/12542#discussion_r1571429163

Pull Request resolved: https://github.com/facebook/rocksdb/pull/12542

Test Plan:
- New UT
- Benchmark
```
TEST_TMPDIR=/dev/shm  ./db_bench --benchmarks=fillseq[-X300] --num=100000 --block_align=1 --compression_type=none
```
Pre-PR:
fillseq [AVG    300 runs] : 422857 (± 3942) ops/sec;   46.8 (± 0.4) MB/sec
Post-PR:
fillseq [AVG    300 runs] : 424707 (± 3799) ops/sec;   47.0 (± 0.4) MB/sec

Reviewed By: ajkr

Differential Revision: D56168447

Pulled By: hx235

fbshipit-source-id: 96209ef950d42943d336f11968ae3fcf9872fc2c

1 files changed, 23 insertions, 0 deletions

diff --git a/table/table_test.cc b/table/table_test.cc
index 02a8d899d..ba44b95b3 100644
--- a/table/table_test.cc
+++ b/table/table_test.cc
@@ -5505,6 +5505,29 @@ TEST_P(BlockBasedTableTest, BlockAlignTest) {
   table_reader.reset();
 }
 
+TEST_P(BlockBasedTableTest, FixBlockAlignMismatchedFileChecksums) {
+  Options options;
+  options.create_if_missing = true;
+  options.compression = kNoCompression;
+  options.file_checksum_gen_factory = GetFileChecksumGenCrc32cFactory();
+  BlockBasedTableOptions bbto;
+  bbto.block_align = true;
+  bbto.block_size = 1024;
+  options.table_factory.reset(NewBlockBasedTableFactory(bbto));
+  const std::string kDBPath =
+      test::PerThreadDBPath("block_align_padded_bytes_verify_file_checksums");
+  ASSERT_OK(DestroyDB(kDBPath, options));
+  DB* db;
+  ASSERT_OK(DB::Open(options, kDBPath, &db));
+  ASSERT_OK(db->Put(WriteOptions(), "k1", "v1"));
+  ASSERT_OK(db->Flush(FlushOptions()));
+  // Before the fix, VerifyFileChecksums() will fail as padded bytes from
+  // aligning blocks are used to generate the checksum to compare against the
+  // one not generated by padded bytes
+  ASSERT_OK(db->VerifyFileChecksums(ReadOptions()));
+  delete db;
+}
+
 TEST_P(BlockBasedTableTest, PropertiesBlockRestartPointTest) {
   BlockBasedTableOptions bbto = GetBlockBasedTableOptions();
   bbto.block_align = true;