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8293502: (fc) FileChannel::transfer methods fail to copy /proc files on Linux

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Reviewed-by: alanb
This commit is contained in:
Brian Burkhalter 2022-09-19 15:57:06 +00:00
parent 1f9ff41312
commit 6e23b43220
2 changed files with 205 additions and 13 deletions
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40
src/java.base/share/classes/sun/nio/ch/FileChannelImpl.java
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@ -761,23 +761,33 @@ public class FileChannelImpl
throw new NonWritableChannelException();
if ((position < 0) || (count < 0))
throw new IllegalArgumentException();
long sz = size();
final long sz = size();
if (position > sz)
return 0;
if ((sz - position) < count)
count = sz - position;
// Now position <= sz so remaining >= 0 and
// remaining == 0 if and only if sz == 0
long remaining = sz - position;
// Attempt a direct transfer, if the kernel supports it, limiting
// the number of bytes according to which platform
int icount = (int)Math.min(count, MAX_DIRECT_TRANSFER_SIZE);
long n;
if ((n = transferToDirectly(position, icount, target)) >= 0)
return n;
// Adjust count only if remaining > 0, i.e.,
// sz > position which means sz > 0
if (remaining > 0 && remaining < count)
count = remaining;
// Attempt a mapped transfer, but only to trusted channel types
if ((n = transferToTrustedChannel(position, count, target)) >= 0)
return n;
// System calls supporting fast transfers might not work on files
// which advertise zero size such as those in Linux /proc
if (sz > 0) {
// Attempt a direct transfer, if the kernel supports it, limiting
// the number of bytes according to which platform
int icount = (int)Math.min(count, MAX_DIRECT_TRANSFER_SIZE);
long n;
if ((n = transferToDirectly(position, icount, target)) >= 0)
return n;
// Attempt a mapped transfer, but only to trusted channel types
if ((n = transferToTrustedChannel(position, count, target)) >= 0)
return n;
}
// Slow path for untrusted targets
return transferToArbitraryChannel(position, count, target);
@ -925,6 +935,8 @@ public class FileChannelImpl
ensureOpen();
if (!src.isOpen())
throw new ClosedChannelException();
if (src instanceof FileChannelImpl fci && !fci.readable)
throw new NonReadableChannelException();
if (!writable)
throw new NonWritableChannelException();
if ((position < 0) || (count < 0))
@ -932,7 +944,9 @@ public class FileChannelImpl
if (position > size())
return 0;
if (src instanceof FileChannelImpl fci) {
// System calls supporting fast transfers might not work on files
// which advertise zero size such as those in Linux /proc
if (src instanceof FileChannelImpl fci && fci.size() > 0) {
long n;
if ((n = transferFromDirectly(fci, position, count)) >= 0)
return n;