197 lines
8.2 KiB
Diff
197 lines
8.2 KiB
Diff
From ed7d354ccaa9465fd12030d6a0621780ecbe14fc Mon Sep 17 00:00:00 2001
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From: Spottedleaf <Spottedleaf@users.noreply.github.com>
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Date: Mon, 1 Apr 2019 18:57:32 -0700
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Subject: [PATCH] Make region files more reliable to write to
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Previously we would write to header before writing our chunk data,
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which opens a window for corruption (or we would overwrite entirely).
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Now the saving process has been changed to follow this chain of events:
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1. We always allocate a new space to write so we do not potentially
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overwrite and corrupt the current data
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2. Write the chunk data first (the order of the fields in
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the chunk data isn't relevant though)
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3. Flush to disk (if the launch flag is used)
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4. Write to the region header last
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5. Flush to disk (if the launch flag is used)
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6. Then we free the previous space allocated
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With this chain of events it is impossible for a chunk write to corrupt
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a region file, unless the operating system has lied and we have NOT flushed
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to disk.
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However server administrators are still recommended to continue performing
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regular backups.
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Note that when Mojang finally decides to change their region format
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to deal with oversized chunks this patch must be changed to deal with
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whatever system they decide to impose.
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If the paper.flush-on-save startup flag is set to true, then the
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steps 3 and 5 will make a call to sync() on the region file's fd,
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effectively flushing to disk.
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We also make use of two flushes to disk per chunk save (to ensure
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ordering and ensure data has gone to disk), so this will negatively
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affect save performance if the startup flag is used (especially on
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HDDs).
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diff --git a/src/main/java/net/minecraft/server/RegionFile.java b/src/main/java/net/minecraft/server/RegionFile.java
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index 82f7af46f8..e5659980b3 100644
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--- a/src/main/java/net/minecraft/server/RegionFile.java
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+++ b/src/main/java/net/minecraft/server/RegionFile.java
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@@ -29,7 +29,7 @@ public class RegionFile {
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private RandomAccessFile c;private RandomAccessFile getDataFile() { return c; } // Paper - OBFHELPER
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private final int[] d = new int[1024];private int[] offsets = d; // Paper - OBFHELPER
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private final int[] e = new int[1024];private int[] timestamps = e; // Paper - OBFHELPER
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- private List<Boolean> f;
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+ private List<Boolean> f; private List<Boolean> getFreeSectors() { return this.f; } // Paper - OBFHELPER
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private int g;
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private long h;
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@@ -211,14 +211,15 @@ public class RegionFile {
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protected synchronized void a(int i, int j, byte[] abyte, int k) {
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try {
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int l = this.getOffset(i, j);
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- int i1 = l >> 8;
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- int j1 = l & 255;
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+ int i1 = l >> 8; final int oldSectorOffset = i1; // Paper - store variable for later
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+ int j1 = l & 255; final int oldSectorCount; // Paper - store variable for later
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// Spigot start
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if (j1 == 255) {
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this.c.seek(i1 * 4096);
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j1 = (this.c.readInt() + 4) / 4096 + 1;
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}
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// Spigot end
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+ oldSectorCount = j1; // Paper - store variable for later (watch out for re-assignments of j1)
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int k1 = (k + 5) / 4096 + 1;
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if (k1 >= 256) {
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@@ -229,14 +230,12 @@ public class RegionFile {
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// Spigot end
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}
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- if (i1 != 0 && j1 == k1) {
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+ if (false && i1 != 0 && j1 == k1) { // Paper - We never want to overrite old data
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this.a(i1, abyte, k);
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} else {
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int l1;
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- for (l1 = 0; l1 < j1; ++l1) {
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- this.f.set(i1 + l1, true);
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- }
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+ // Paper - We do not free old sectors until we are done writing the new chunk data
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l1 = this.f.indexOf(true);
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int i2 = 0;
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@@ -263,13 +262,13 @@ public class RegionFile {
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if (i2 >= k1) {
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i1 = l1;
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- this.a(i, j, l1 << 8 | (k1 > 255 ? 255 : k1)); // Spigot
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+ //this.a(i, j, l1 << 8 | (k1 > 255 ? 255 : k1)); // Spigot // Paper - We only write to header after we've written chunk data
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for (j2 = 0; j2 < k1; ++j2) {
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this.f.set(i1 + j2, false);
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}
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- this.a(i1, abyte, k);
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+ this.writeChunk(i, j,i1 << 8 | (k1 > 255 ? 255 : k1), i1, abyte, k); // Paper - Ensure we do not corrupt region files
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} else {
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this.c.seek(this.c.length());
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i1 = this.f.size();
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@@ -280,9 +279,14 @@ public class RegionFile {
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}
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this.g += 4096 * k1;
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- this.a(i1, abyte, k);
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- this.a(i, j, i1 << 8 | (k1 > 255 ? 255 : k1)); // Spigot
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+ this.writeChunk(i, j, i1 << 8 | (k1 > 255 ? 255 : k1), i1, abyte, k); // Paper - Ensure we do not corrupt region files
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+ }
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+
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+ // Paper start - Now that we've written the new chunk we can free the old data
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+ for (int off = 0; off < oldSectorCount; ++off) {
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+ this.getFreeSectors().set(oldSectorOffset + off, true);
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}
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+ // Paper end
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}
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this.b(i, j, (int) (SystemUtils.getTimeMillis() / 1000L));
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@@ -292,10 +296,10 @@ public class RegionFile {
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}
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+ private void writeChunkData(final int sectorOffset, final byte[] data, final int dataLength) throws IOException { this.a(sectorOffset, data, dataLength); } // Paper - OBFHELPER
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private void a(int i, byte[] abyte, int j) throws IOException {
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this.c.seek((long) (i * 4096));
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- this.c.writeInt(j + 1);
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- this.c.writeByte(2);
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+ this.writeIntAndByte(j + 1, (byte)2); // Paper - Avoid 4 io write calls
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this.c.write(abyte, 0, j);
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}
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@@ -311,16 +315,17 @@ public class RegionFile {
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return this.getOffset(i, j) != 0;
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}
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+ private void updateChunkHeader(final int x, final int z, final int offset) throws IOException { this.a(x, z, offset); } // Paper - OBFHELPER
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private void a(int i, int j, int k) throws IOException {
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this.d[i + j * 32] = k;
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this.c.seek((long) ((i + j * 32) * 4));
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- this.c.writeInt(k);
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+ this.writeInt(k); // Paper - Avoid 3 io write calls
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}
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private void b(int i, int j, int k) throws IOException {
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this.e[i + j * 32] = k;
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this.c.seek((long) (4096 + (i + j * 32) * 4));
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- this.c.writeInt(k);
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+ this.writeInt(k); // Paper - Avoid 3 io write calls
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}
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public void close() throws IOException {
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@@ -331,6 +336,40 @@ public class RegionFile {
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}
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// Paper start
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+ private static final boolean FLUSH_ON_SAVE = Boolean.getBoolean("paper.flush-on-save");
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+ private void syncRegionFile() throws IOException {
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+ if (!FLUSH_ON_SAVE) {
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+ return;
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+ }
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+ this.getDataFile().getFD().sync(); // rethrow exception as we want to avoid corrupting a regionfile
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+ }
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+
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+ private final java.nio.ByteBuffer scratchBuffer = java.nio.ByteBuffer.allocate(8);
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+
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+ private void writeInt(final int value) throws IOException {
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+ synchronized (scratchBuffer) {
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+ this.scratchBuffer.putInt(0, value);
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+ this.getDataFile().write(this.scratchBuffer.array(), 0, 4);
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+ }
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+ }
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+
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+ // writes v1 then v2
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+ private void writeIntAndByte(final int v1, final byte v2) throws IOException {
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+ synchronized (scratchBuffer) {
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+ this.scratchBuffer.putInt(0, v1);
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+ this.scratchBuffer.put(4, v2);
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+ this.getDataFile().write(this.scratchBuffer.array(), 0, 5);
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+ }
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+ }
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+
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+ private void writeChunk(final int x, final int z, final int chunkHeaderData,
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+ final int chunkOffset, final byte[] chunkData, final int chunkDataLength) throws IOException {
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+ this.writeChunkData(chunkOffset, chunkData, chunkDataLength);
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+ this.syncRegionFile(); // Sync is required to ensure the previous data is written successfully
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+ this.updateChunkHeader(x, z, chunkHeaderData);
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+ this.syncRegionFile(); // Ensure header changes go through
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+ }
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+
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public synchronized void deleteChunk(int j1) {
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backup();
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int k = offsets[j1];
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--
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2.21.0
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