Comment cleanup

Author: samueldlightfoot

src/java/org/apache/cassandra/config/DatabaseDescriptor.java

@@ -3412,9 +3412,6 @@ public static void initializeCommitLogDiskAccessMode()
         commitLogWriteDiskAccessMode = accessModeDirectIoPair.left;
     }
 
-    /**
-     * Return background write disk access mode.
-     */
     public static DiskAccessMode getBackgroundWriteDiskAccessMode()
     {
         return backgroundWriteDiskAccessMode;
@@ -3437,13 +3434,11 @@ public static void initializeBackgroundWriteDiskAccessMode()
     {
         DiskAccessMode providedMode = conf.background_write_disk_access_mode;
 
-        // For 'auto', default to standard (conservative, safe default)
         if (providedMode == DiskAccessMode.auto)
         {
             providedMode = DiskAccessMode.standard;
         }
 
-        // Validate Direct IO is supported on ALL data directories if requested
         if (providedMode == DiskAccessMode.direct)
         {
             // DataStorageSpec already rejects negatives at parse time; zero is the remaining
@@ -3453,7 +3448,6 @@ public static void initializeBackgroundWriteDiskAccessMode()
                 throw new ConfigurationException("direct_write_buffer_size must be > 0 when background_write_disk_access_mode is 'direct'. " +
                                                  "Got: " + conf.direct_write_buffer_size, false);
 
-            // Only check Direct IO support if not running as a tool
             if (!toolInitialized)
             {
                 List<String> unsupportedLocations = new ArrayList<>();

src/java/org/apache/cassandra/io/compress/CompressedSequentialWriter.java

@@ -47,7 +47,6 @@
 
 public class CompressedSequentialWriter extends SequentialWriter
 {
-    // Checksum writer for CRC per chunk and full file digest
     private final ChecksumWriter crcMetadata;
 
     // holds offset in the file where current chunk should be written

src/java/org/apache/cassandra/io/compress/DirectCompressedSequentialWriter.java

@@ -67,7 +67,6 @@ public class DirectCompressedSequentialWriter extends CompressedSequentialWriter
     // per JVM so a misconfiguration is operator-visible without per-SSTable spam.
     private static final AtomicBoolean undersizedBufferWarned = new AtomicBoolean(false);
 
-    // Per-chunk CRC32 trailer width in bytes (CRC32.getValue() stored via putInt).
     private static final int CRC_LENGTH = Integer.BYTES;
 
     // Sized to hold at least one full chunk + CRC + post-flush leftover:

src/java/org/apache/cassandra/io/util/SequentialWriter.java

@@ -185,16 +185,6 @@ public SequentialWriter(File file, SequentialWriterOption option, boolean strict
         this(file, option.allocateBuffer(), option, strictFlushing);
     }
 
-    /**
-     * Constructor that accepts a buffer and optional open options for the file channel.
-     * This allows subclasses to provide custom buffers and specify options like O_DIRECT for Direct IO.
-     *
-     * @param file the file being written
-     * @param buffer write buffer
-     * @param option writer options
-     * @param strictFlushing whether to enforce strict flushing
-     * @param extraOpenOptions additional options to pass to FileChannel.open (e.g., ExtendedOpenOption.DIRECT)
-     */
     protected SequentialWriter(File file, ByteBuffer buffer, SequentialWriterOption option, boolean strictFlushing,
                                OpenOption... extraOpenOptions)
     {

src/java/org/apache/cassandra/service/StartupChecks.java

@@ -260,7 +260,6 @@ public void execute(StartupChecksConfiguration configuration) throws StartupExce
             if (DatabaseDescriptor.getCommitLogWriteDiskAccessMode() == Config.DiskAccessMode.direct)
                 directIOWritePaths.add(new File(DatabaseDescriptor.getCommitLogLocation()).toPath());
 
-            // Add data directories when Direct IO is enabled for background writes
             if (DatabaseDescriptor.getBackgroundWriteDiskAccessMode() == Config.DiskAccessMode.direct)
             {
                 for (String dataDir : DatabaseDescriptor.getAllDataFileLocations())
@@ -739,7 +738,6 @@ public void execute(StartupChecksConfiguration configuration) throws StartupExce
             if (configuration.isDisabled(name()))
                 return;
 
-            // Check if either compaction reads or writes use Direct IO
             boolean directReads = DatabaseDescriptor.getCompactionReadDiskAccessMode() == Config.DiskAccessMode.direct;
             boolean directWrites = DatabaseDescriptor.getBackgroundWriteDiskAccessMode() == Config.DiskAccessMode.direct;
 

test/distributed/org/apache/cassandra/distributed/test/StreamingDirectWriteTest.java

@@ -29,18 +29,12 @@
 
 import static org.assertj.core.api.Assertions.assertThat;
 
-/**
- * Verifies the chunked streaming receiver path (CassandraStreamReader / CassandraCompressedStreamReader →
- * BigTableWriter.openDataWriter → DataComponent.buildWriter with OperationType.STREAM) writes via
- * {@link org.apache.cassandra.io.compress.DirectCompressedSequentialWriter} when direct background writes
- * are enabled. Entire-SSTable (zero-copy) streaming bypasses DataComponent.buildWriter, so it must be
- * disabled here.
- */
 public class StreamingDirectWriteTest extends TestBaseImpl
 {
     @Test
     public void testChunkedStreamReceiverWithDirectWrites() throws IOException
     {
+        // ZCS streaming bypasses DataComponent.buildWriter; disable to exercise the chunked receiver path.
         try (Cluster cluster = init(Cluster.build(2)
                                            .withConfig(c -> c.with(Feature.NETWORK, Feature.GOSSIP)
                                                              .set("stream_entire_sstables", false)