Always use updatingChunks for saveAllChunks (#6534)

patches/server/Use-updatingChunks-for-saving.patch

@@ -0,0 +1,39 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Jason Penilla <11360596+jpenilla@users.noreply.github.com>
+Date: Tue, 31 Aug 2021 17:12:01 -0700
+Subject: [PATCH] Use updatingChunks for saving
+
+
+diff --git a/src/main/java/net/minecraft/server/level/ChunkMap.java b/src/main/java/net/minecraft/server/level/ChunkMap.java
+index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
+--- a/src/main/java/net/minecraft/server/level/ChunkMap.java
++++ b/src/main/java/net/minecraft/server/level/ChunkMap.java
+@@ -0,0 +0,0 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
+     }
+     // Paper end
+ 
++    // Paper start
++    public Long2ObjectLinkedOpenHashMap<ChunkHolder> getVisibleChunks() {
++        synchronized (this.updatingChunks) {
++            return this.updatingChunks.getVisibleMap().clone();
++        }
++    }
++    // Paper end
++
+     protected void saveAllChunks(boolean flush) {
++        final Long2ObjectLinkedOpenHashMap<ChunkHolder> visibleChunks = this.getVisibleChunks(); // Paper
+         if (flush) {
+-            List<ChunkHolder> list = (List) this.visibleChunkMap.values().stream().filter(ChunkHolder::wasAccessibleSinceLastSave).peek(ChunkHolder::refreshAccessibility).collect(Collectors.toList());
++            List<ChunkHolder> list = visibleChunks.values().stream().filter(ChunkHolder::wasAccessibleSinceLastSave).peek(ChunkHolder::refreshAccessibility).collect(Collectors.toList()); // Paper
+             MutableBoolean mutableboolean = new MutableBoolean();
+ 
+             do {
+@@ -0,0 +0,0 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
+             this.level.asyncChunkTaskManager.flush(); // Paper - flush to preserve behavior compat with pre-async behaviour
+ //            this.i(); // Paper - nuke IOWorker
+         } else {
+-            this.visibleChunkMap.values().stream().filter(ChunkHolder::wasAccessibleSinceLastSave).forEach((playerchunk) -> {
++            visibleChunks.values().stream().filter(ChunkHolder::wasAccessibleSinceLastSave).forEach((playerchunk) -> { // Paper
+                 ChunkAccess ichunkaccess = (ChunkAccess) playerchunk.getChunkToSave().getNow(null); // CraftBukkit - decompile error
+ 
+                 if (ichunkaccess instanceof ImposterProtoChunk || ichunkaccess instanceof LevelChunk) {