Paper/patches/server/0721-Only-write-chunk-data-to-disk-if-it-serializes-witho.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Sun, 19 Dec 2021 09:13:41 -0800
Subject: [PATCH] Only write chunk data to disk if it serializes without
 throwing

This ensures at least a valid version of the chunk exists
on disk, even if outdated

diff --git a/src/main/java/net/minecraft/world/level/chunk/storage/RegionFile.java b/src/main/java/net/minecraft/world/level/chunk/storage/RegionFile.java
index 13ab2d2d8d0d3ab0facbae8285b09267765cc97d..a030d149d7b65d9d3983fecc77a560fbd304f0d3 100644
--- a/src/main/java/net/minecraft/world/level/chunk/storage/RegionFile.java
+++ b/src/main/java/net/minecraft/world/level/chunk/storage/RegionFile.java
@@ -520,6 +520,9 @@ public class RegionFile implements AutoCloseable {
         }
 
     }
+
+    public static final int MAX_CHUNK_SIZE = 500 * 1024 * 1024; // Paper - don't write garbage data to disk if writing serialization fails
+
     // Paper end
     private class ChunkBuffer extends ByteArrayOutputStream {
 
@@ -535,6 +538,24 @@ public class RegionFile implements AutoCloseable {
             this.pos = chunkcoordintpair;
         }
 
+        // Paper start - don't write garbage data to disk if writing serialization fails
+        @Override
+        public void write(final int b) {
+            if (this.count > MAX_CHUNK_SIZE) {
+                throw new RegionFileStorage.RegionFileSizeException("Region file too large: " + this.count);
+            }
+            super.write(b);
+        }
+
+        @Override
+        public void write(final byte[] b, final int off, final int len) {
+            if (this.count + len > MAX_CHUNK_SIZE) {
+                throw new RegionFileStorage.RegionFileSizeException("Region file too large: " + (this.count + len));
+            }
+            super.write(b, off, len);
+        }
+        // Paper end
+
         public void close() throws IOException {
             ByteBuffer bytebuffer = ByteBuffer.wrap(this.buf, 0, this.count);
 
diff --git a/src/main/java/net/minecraft/world/level/chunk/storage/RegionFileStorage.java b/src/main/java/net/minecraft/world/level/chunk/storage/RegionFileStorage.java
index 16346d727a854996ec1d2adb56ebca2a9ff7ab3b..96e5d67f9150c0962b06b2fb67222857fd948db1 100644
--- a/src/main/java/net/minecraft/world/level/chunk/storage/RegionFileStorage.java
+++ b/src/main/java/net/minecraft/world/level/chunk/storage/RegionFileStorage.java
@@ -239,10 +239,17 @@ public final class RegionFileStorage implements AutoCloseable {
                 NbtIo.write(nbt, (DataOutput) dataoutputstream);
                 regionfile.setStatus(pos.x, pos.z, ChunkSerializer.getStatus(nbt)); // Paper - cache status on disk
                 regionfile.setOversized(pos.x, pos.z, false); // Paper - We don't do this anymore, mojang stores differently, but clear old meta flag if it exists to get rid of our own meta file once last oversized is gone
+                dataoutputstream.close(); // Paper - only write if successful
+            // Paper start - don't write garbage data to disk if writing serialization fails
+            } catch (RegionFileSizeException e) {
+                attempts = 5; // Don't retry
+                regionfile.clear(pos);
+                throw e;
+                // Paper end - don't write garbage data to disk if writing serialization fails
             } catch (Throwable throwable) {
                 if (dataoutputstream != null) {
                     try {
-                        dataoutputstream.close();
+                        //dataoutputstream.close(); // Paper - don't write garbage data to disk if writing serialization fails
                     } catch (Throwable throwable1) {
                         throwable.addSuppressed(throwable1);
                     }
@@ -250,10 +257,7 @@ public final class RegionFileStorage implements AutoCloseable {
 
                 throw throwable;
             }
-
-            if (dataoutputstream != null) {
-                dataoutputstream.close();
-            }
+            // Paper - move into try block to only write if successfully serialized
         }
         // Paper start
         return;
@@ -296,4 +300,13 @@ public final class RegionFileStorage implements AutoCloseable {
         }
 
     }
+
+    // Paper start
+    public static final class RegionFileSizeException extends RuntimeException {
+
+        public RegionFileSizeException(String message) {
+            super(message);
+        }
+    }
+    // Paper end
 }