--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/jdk/java/nio/channels/FileChannel/directio/libDirectIO.c	Tue Oct 17 16:51:11 2017 -0700
@@ -0,0 +1,103 @@
+/*
+ * Copyright (c) 2017, 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 if a file exists in the file system cache
+ */
+#include <stdlib.h>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <sys/mman.h>
+
+#include "jni.h"
+
+/*
+ * Throws an exception with the given class name and detail message
+ */
+static void ThrowException(JNIEnv *env, const char *name, const char *msg) {
+    jclass cls = (*env)->FindClass(env, name);
+    if (cls != NULL) {
+        (*env)->ThrowNew(env, cls, msg);
+    }
+}
+
+/*
+ * Class:     DirectIO
+ * Method:    isFileInCache0
+ * Signature: (ILjava/lang/String;)Z
+ */
+JNIEXPORT jboolean Java_DirectIOTest_isFileInCache0(JNIEnv *env,
+                                                jclass cls,
+                                                jint file_size,
+                                                jstring file_path) {
+    void *f_mmap;
+#ifdef __linux__
+    unsigned char *f_seg;
+#else
+    char *f_seg;
+#endif
+
+#ifdef __APPLE__
+    size_t mask = MINCORE_INCORE;
+#else
+    size_t mask = 0x1;
+#endif
+
+    size_t page_size = getpagesize();
+    size_t index = (file_size + page_size - 1) /page_size;
+    jboolean result = JNI_FALSE;
+
+    const char* path = (*env)->GetStringUTFChars(env, file_path, JNI_FALSE);
+
+    int fd = open(path, O_RDWR);
+
+    (*env)->ReleaseStringUTFChars(env, file_path, path);
+
+    f_mmap = mmap(0, file_size, PROT_NONE, MAP_SHARED, fd, 0);
+    if (f_mmap == MAP_FAILED) {
+        close(fd);
+        ThrowException(env, "java/io/IOException",
+            "test of whether file exists in cache failed");
+    }
+    f_seg = malloc(index);
+    if (f_seg != NULL) {
+        if(mincore(f_mmap, file_size, f_seg) == 0) {
+            size_t i;
+            for (i = 0; i < index; i++) {
+                if (f_seg[i] & mask) {
+                    result = JNI_TRUE;
+                    break;
+                }
+            }
+        }
+        free(f_seg);
+    } else {
+        ThrowException(env, "java/io/IOException",
+            "test of whether file exists in cache failed");
+    }
+    close(fd);
+    munmap(f_mmap, file_size);
+    return result;
+}