This has been initially observed with the test case runtime/os/TestTracePageSizes on a debian testing.
$ uname -srv
Linux 5.10.0-6-amd64 #1 SMP Debian 5.10.28-1 (2021-04-09)

Tests is test/jdk/java/nio are all passing.

java.nio.file.FileSystemException: /proc/self/smaps -> smaps-copy-31084-0.txt: Invalid argument
at java.base/sun.nio.fs.UnixException.translateToIOException(UnixException.java:100)
at java.base/sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:106)
at java.base/sun.nio.fs.UnixCopyFile.copyFile(UnixCopyFile.java:256)
at java.base/sun.nio.fs.UnixCopyFile.copy(UnixCopyFile.java:603)
at java.base/sun.nio.fs.UnixFileSystemProvider.copy(UnixFileSystemProvider.java:258)
at java.base/java.nio.file.Files.copy(Files.java:1305)
at TestTracePageSizes.copySmaps(TestTracePageSizes.java:122)
at TestTracePageSizes.parseSmaps(TestTracePageSizes.java:134)
at TestTracePageSizes.main(TestTracePageSizes.java:258)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:568)
at com.sun.javatest.regtest.agent.MainWrapper$MainThread.run(MainWrapper.java:127)
at java.base/java.lang.Thread.run(Thread.java:833)

The man page says:

EINVAL Descriptor is not valid or locked, or an mmap(2)-like operation is not available for in_fd, or count is negative.

Probably, an fd pointing to a file in /proc does not support mmap like operations on all kernel versions.