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8140241: (fc) Data transfer from FileChannel to itself causes hang in…
… case of overlap

Reviewed-by: alanb
  • Loading branch information
Brian Burkhalter committed Aug 12, 2021
1 parent 93cab7d commit 428d51694f56788f89e8df100a74cbadd369ffa6
@@ -585,6 +585,15 @@ private long transferToTrustedChannel(long position, long count,
if (!((target instanceof FileChannelImpl) || isSelChImpl))
return IOStatus.UNSUPPORTED;

if (target == this) {
long posThis = position();
if (posThis - count + 1 <= position &&
position - count + 1 <= posThis &&
!nd.canTransferToFromOverlappedMap()) {
return IOStatus.UNSUPPORTED_CASE;
}
}

// Trusted target: Use a mapped buffer
long remaining = count;
while (remaining > 0L) {
@@ -677,7 +686,7 @@ public long transferTo(long position, long count,
return 0;

if ((sz - position) < count)
count = (int)(sz - position);
count = sz - position;

// Attempt a direct transfer, if the kernel supports it, limiting
// the number of bytes according to which platform
@@ -704,6 +713,14 @@ private long transferFromFileChannel(FileChannelImpl src,
long pos = src.position();
long max = Math.min(count, src.size() - pos);

if (src == this) {
if (position() - max + 1 <= pos &&
pos - max + 1 <= position() &&
!nd.canTransferToFromOverlappedMap()) {
return IOStatus.UNSUPPORTED_CASE;
}
}

long remaining = max;
long p = pos;
while (remaining > 0L) {
@@ -779,9 +796,12 @@ public long transferFrom(ReadableByteChannel src,
throw new IllegalArgumentException();
if (position > size())
return 0;
if (src instanceof FileChannelImpl)
return transferFromFileChannel((FileChannelImpl)src,
position, count);

if (src instanceof FileChannelImpl fci) {
long n = transferFromFileChannel(fci, position, count);
if (n >= 0)
return n;
}

return transferFromArbitraryChannel(src, position, count);
}
@@ -1,5 +1,5 @@
/*
* Copyright (c) 2007, 2018, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2007, 2021, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@@ -67,5 +67,7 @@ abstract FileDescriptor duplicateForMapping(FileDescriptor fd)

abstract boolean transferToDirectlyNeedsPositionLock();

abstract boolean canTransferToFromOverlappedMap();

abstract int setDirectIO(FileDescriptor fd, String path);
}
@@ -1,5 +1,5 @@
/*
* Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2000, 2021, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@@ -126,6 +126,10 @@ boolean transferToDirectlyNeedsPositionLock() {
return false;
}

boolean canTransferToFromOverlappedMap() {
return canTransferToFromOverlappedMap0();
}

int setDirectIO(FileDescriptor fd, String path) {
int result = -1;
try {
@@ -184,6 +188,8 @@ static native void release0(FileDescriptor fd, long pos, long size)

static native void closeIntFD(int fd) throws IOException;

static native boolean canTransferToFromOverlappedMap0();

static native int setDirect0(FileDescriptor fd) throws IOException;

static native void init();
@@ -338,6 +338,16 @@ Java_sun_nio_ch_FileDispatcherImpl_closeIntFD(JNIEnv *env, jclass clazz, jint fd
closeFileDescriptor(env, fd);
}

JNIEXPORT jboolean JNICALL
Java_sun_nio_ch_FileDispatcherImpl_canTransferToFromOverlappedMap0(JNIEnv *env, jclass clazz)
{
#ifdef MACOSX
return JNI_FALSE;
#else
return JNI_TRUE;
#endif
}

JNIEXPORT jint JNICALL
Java_sun_nio_ch_FileDispatcherImpl_setDirect0(JNIEnv *env, jclass clazz,
jobject fdo)
@@ -1,5 +1,5 @@
/*
* Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2000, 2021, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@@ -125,6 +125,10 @@ boolean transferToDirectlyNeedsPositionLock() {
return true;
}

boolean canTransferToFromOverlappedMap() {
return true;
}

int setDirectIO(FileDescriptor fd, String path) {
int result = -1;
String filePath = path.substring(0, path.lastIndexOf(File.separator));
@@ -0,0 +1,118 @@
/*
* Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/

/* @test
* @bug 8140241
* @summary Test transferring to and from same file channel
*/
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.OutputStream;
import java.io.RandomAccessFile;
import java.io.IOException;
import java.nio.channels.FileChannel;
import java.util.Random;

public class TransferOverlappedFileChannel {

public static void main(String[] args) throws Exception {
File file = File.createTempFile("readingin", null);
file.deleteOnExit();
generateBigFile(file);
RandomAccessFile raf = new RandomAccessFile(file, "rw");
try (FileChannel channel = raf.getChannel()) {
transferToNoOverlap(file, channel);
transferToOverlap(file, channel);
transferFromNoOverlap(file, channel);
transferFromOverlap(file, channel);
} finally {
file.delete();
}
}

private static void transferToNoOverlap(File file, FileChannel channel)
throws IOException {
final long length = file.length();

// position at three quarters
channel.position(length*3/4);
// copy last quarter to third quarter
// (copied and overwritten regions do NOT overlap)
// So: 1 2 3 4 -> 1 2 4 4
channel.transferTo(length / 2, length / 4, channel);
System.out.println("transferToNoOverlap: OK");
}

private static void transferToOverlap(File file, FileChannel channel)
throws IOException {
final long length = file.length();

// position at half
channel.position(length/2);
// copy last half to second quarter
// (copied and overwritten regions DO overlap)
// So: 1 2 3 4 -> 1 3 4 4
channel.transferTo(length / 4, length / 2, channel);
System.out.println("transferToOverlap: OK");
}

private static void transferFromNoOverlap(File file, FileChannel channel)
throws IOException {
final long length = file.length();

// position at three quarters
channel.position(length*3/4);
// copy last quarter to third quarter
// (copied and overwritten regions do NOT overlap)
// So: 1 2 3 4 -> 1 2 4 4
channel.transferFrom(channel, length / 2, length / 4);
System.out.println("transferFromNoOverlap: OK");
}

private static void transferFromOverlap(File file, FileChannel channel)
throws IOException {
final long length = file.length();

// position at half
channel.position(length/2);
// copy last half to second quarter
// (copied and overwritten regions DO overlap)
// So: 1 2 3 4 -> 1 3 4 4
channel.transferFrom(channel, length / 4, length / 2);
System.out.println("transferFromOverlap: OK");
}

private static void generateBigFile(File file) throws Exception {
try (OutputStream out = new BufferedOutputStream(
new FileOutputStream(file))) {
byte[] randomBytes = new byte[1024];
Random rand = new Random(0);
rand.nextBytes(randomBytes);
for (int i = 0; i < 1024; i++) {
out.write(randomBytes);
}
out.flush();
}
}
}

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