Fix pooled buffer leak resulting in dynmap black spots - Fixes #3386

Dynmap accessed the raw bytes because it utilized NBT locally, but the
NBTTagcompound was garbage collected while the bytes were still being used.

This will return getBytes() back to being safe, and add a new PoolSafe method
that will prevent the additional allocations for general chunk loading.

Also fixed applyPatches for people with paths in their working directory
if they have mcdev sources built.

Spigot-Server-Patches/0522-Optimize-NibbleArray-to-use-pooled-buffers.patch

@@ -9,10 +9,36 @@ an object pool for these.
 Uses lots of advanced new capabilities of the Paper codebase :)
 
 diff --git a/src/main/java/net/minecraft/server/ChunkRegionLoader.java b/src/main/java/net/minecraft/server/ChunkRegionLoader.java
-index e625842e524f18e469f7695b27d52d4d04892266..82264bf651b9d1f6614fef5efc29419947407eca 100644
+index e625842e524f18e469f7695b27d52d4d04892266..7c7b5212d8603627f260344a2fdcf575f81d7f63 100644
 --- a/src/main/java/net/minecraft/server/ChunkRegionLoader.java
 +++ b/src/main/java/net/minecraft/server/ChunkRegionLoader.java
-@@ -387,11 +387,15 @@ public class ChunkRegionLoader {
+@@ -105,7 +105,11 @@ public class ChunkRegionLoader {
+             if (flag) {
+                 if (nbttagcompound2.hasKeyOfType("BlockLight", 7)) {
+                     // Paper start - delay this task since we're executing off-main
+-                    NibbleArray blockLight = new NibbleArray(nbttagcompound2.getByteArray("BlockLight"));
++                    // Pool safe get and clean
++                    NBTTagByteArray blockLightArray = nbttagcompound2.getByteArrayTag("BlockLight");
++                    // NibbleArray will copy the data in the ctor
++                    NibbleArray blockLight = new NibbleArray(blockLightArray.getBytesPoolSafe());
++                    blockLightArray.cleanPooledBytes();
+                     // Note: We move the block light nibble array creation here for perf & in case the compound is modified
+                     tasksToExecuteOnMain.add(() -> {
+                         lightengine.a(EnumSkyBlock.BLOCK, SectionPosition.a(chunkcoordintpair, b0), blockLight);
+@@ -115,7 +119,11 @@ public class ChunkRegionLoader {
+ 
+                 if (flag2 && nbttagcompound2.hasKeyOfType("SkyLight", 7)) {
+                     // Paper start - delay this task since we're executing off-main
+-                    NibbleArray skyLight = new NibbleArray(nbttagcompound2.getByteArray("SkyLight"));
++                    // Pool safe get and clean
++                    NBTTagByteArray skyLightArray = nbttagcompound2.getByteArrayTag("SkyLight");
++                    // NibbleArray will copy the data in the ctor
++                    NibbleArray skyLight = new NibbleArray(skyLightArray.getBytesPoolSafe());
++                    skyLightArray.cleanPooledBytes();
+                     // Note: We move the block light nibble array creation here for perf & in case the compound is modified
+                     tasksToExecuteOnMain.add(() -> {
+                         lightengine.a(EnumSkyBlock.SKY, SectionPosition.a(chunkcoordintpair, b0), skyLight);
+@@ -387,11 +395,15 @@ public class ChunkRegionLoader {
                  }
  
                  if (nibblearray != null && !nibblearray.c()) {
@@ -57,7 +83,7 @@ index 06bc8371fe9de4d23fdd47e5a3919541bb399fd8..bf37e4ec1f3f4f73c27e1eecffa96423
                  return new NibbleArray();
              }
 diff --git a/src/main/java/net/minecraft/server/NBTTagByteArray.java b/src/main/java/net/minecraft/server/NBTTagByteArray.java
-index 034244c2465b9999c6fba63ab2310becef51b887..a964647d1464d33c69b860cce44d918a20054532 100644
+index 034244c2465b9999c6fba63ab2310becef51b887..5310246ec97b8a78848214b152a67195fd8ddef9 100644
 --- a/src/main/java/net/minecraft/server/NBTTagByteArray.java
 +++ b/src/main/java/net/minecraft/server/NBTTagByteArray.java
 @@ -17,10 +17,17 @@ public class NBTTagByteArray extends NBTList<NBTTagByte> {
@@ -73,13 +99,74 @@ index 034244c2465b9999c6fba63ab2310becef51b887..a964647d1464d33c69b860cce44d918a
 +            NBTTagByteArray nbt = new NBTTagByteArray(abyte);
 +            if (abyte.length == 2048) {
 +                // register cleaner
-+                MCUtil.registerCleaner(nbt, abyte, NibbleArray::releaseBytes);
++                nbt.cleaner = MCUtil.registerCleaner(nbt, abyte, NibbleArray::releaseBytes);
 +            }
 +            return nbt;
 +            // Paper end
          }
  
          @Override
+@@ -121,6 +128,35 @@ public class NBTTagByteArray extends NBTList<NBTTagByte> {
+     }
+ 
+     public byte[] getBytes() {
++        // Paper start
++        Runnable cleaner = this.cleaner;
++        if (cleaner != null) { // This will only be possible for 2048 byte arrays
++            // cleaners are thread safe if it tries to run twice, if getBytes is accessed concurrently, worse
++            // case is multiple clones
++            this.data = this.data.clone();
++            this.cleaner = null;
++            cleaner.run();
++        }
++        if (this.data == null) {
++            new Throwable("Horrible thing happened! Something hooked into Chunk Loading internals and accessed NBT after chunk was done loading. Please tell plugin to stop doing this, clone the memory before hand.").printStackTrace();
++        }
++        return this.data;
++    }
++    Runnable cleaner;
++    public void cleanPooledBytes() {
++        Runnable cleaner = this.cleaner;
++        if (cleaner != null) { // This will only be possible for 2048 byte arrays
++            this.cleaner = null;
++            this.data = null;
++            cleaner.run();
++        }
++    }
++    /**
++     * Use ONLY if you know the life of your usage of the bytes matches the life of the nbt node itself.
++     * If this NBT node can go unreachable before your usage of the bytes is over with, DO NOT use this
++     */
++    public byte[] getBytesPoolSafe() {
++        // Paper end
+         return this.data;
+     }
+ 
+diff --git a/src/main/java/net/minecraft/server/NBTTagCompound.java b/src/main/java/net/minecraft/server/NBTTagCompound.java
+index 02a2ed1baa3f82d302432b7bc627f3179751f886..5f38c962115f732fae20b61410dfc35b09248f4c 100644
+--- a/src/main/java/net/minecraft/server/NBTTagCompound.java
++++ b/src/main/java/net/minecraft/server/NBTTagCompound.java
+@@ -298,6 +298,20 @@ public class NBTTagCompound implements NBTBase {
+         return new byte[0];
+     }
+ 
++    // Paper start
++    public NBTTagByteArray getByteArrayTag(String s) {
++        try {
++            if (this.hasKeyOfType(s, 7)) {
++                return ((NBTTagByteArray) this.map.get(s));
++            }
++        } catch (ClassCastException classcastexception) {
++            throw new ReportedException(this.a(s, NBTTagByteArray.a, classcastexception));
++        }
++
++        return new NBTTagByteArray(new byte[0]);
++    }
++    // Paper end
++
+     public int[] getIntArray(String s) {
+         try {
+             if (this.hasKeyOfType(s, 11)) {
 diff --git a/src/main/java/net/minecraft/server/NibbleArray.java b/src/main/java/net/minecraft/server/NibbleArray.java
 index 996c8326387b5a7fe62db6a76e000144565cb85b..1fcb1bdab28f79320aef50a9bbb2fbee8c7a2964 100644
 --- a/src/main/java/net/minecraft/server/NibbleArray.java

scripts/applyPatches.sh

@@ -92,14 +92,14 @@ echo "Importing MC Dev"
 ./scripts/importmcdev.sh "$basedir" || exit 1
 
 # Apply paper
-cd "$basedir"
 (
     applyPatch "work/Spigot/Spigot-API" Paper-API HEAD &&
     applyPatch "work/Spigot/Spigot-Server" Paper-Server HEAD
+    cd "$basedir"
 
     # if we have previously ran ./paper mcdev, update it
     if [ -d "$workdir/Minecraft/$minecraftversion/src" ]; then
-        $basedir/scripts/makemcdevsrc.sh $basedir
+        ./scripts/makemcdevsrc.sh "$basedir"
     fi
 ) || (
     echo "Failed to apply Paper Patches"