8286671: (fc) Modify sun.nio.ch.FileChannelImpl.map0() to accept a FileDescriptor parameter

Reviewed-by: alanb, jpai

src/java.base/share/classes/sun/nio/ch/FileChannelImpl.java

@@ -1239,7 +1239,7 @@ public class FileChannelImpl
                 mapSize = size + pagePosition;
                 try {
                     // If map0 did not throw an exception, the address is valid
-                    addr = map0(prot, mapPosition, mapSize, isSync);
+                    addr = map0(fd, prot, mapPosition, mapSize, isSync);
                 } catch (OutOfMemoryError x) {
                     // An OutOfMemoryError may indicate that we've exhausted
                     // memory so force gc and re-attempt map
@@ -1250,7 +1250,7 @@ public class FileChannelImpl
                         Thread.currentThread().interrupt();
                     }
                     try {
-                        addr = map0(prot, mapPosition, mapSize, isSync);
+                        addr = map0(fd, prot, mapPosition, mapSize, isSync);
                     } catch (OutOfMemoryError y) {
                         // After a second OOME, fail
                         throw new IOException("Map failed", y);
@@ -1500,7 +1500,8 @@ public class FileChannelImpl
     // -- Native methods --
 
     // Creates a new mapping
-    private native long map0(int prot, long position, long length, boolean isSync)
+    private native long map0(FileDescriptor fd, int prot, long position,
+                             long length, boolean isSync)
         throws IOException;
 
     // Removes an existing mapping
@@ -1514,12 +1515,12 @@ public class FileChannelImpl
     // Retrieves the maximum size of a transfer
     private static native int maxDirectTransferSize0();
 
-    // Caches fieldIDs
+    // Retrieves allocation granularity
-    private static native long initIDs();
+    private static native long allocationGranularity0();
 
     static {
         IOUtil.load();
-        allocationGranularity = initIDs();
+        allocationGranularity = allocationGranularity0();
         MAX_DIRECT_TRANSFER_SIZE = maxDirectTransferSize0();
     }
 }

src/java.base/unix/native/libnio/ch/FileChannelImpl.c

@@ -50,13 +50,10 @@
 #include "java_lang_Integer.h"
 #include <assert.h>
 
-static jfieldID chan_fd;        /* jobject 'fd' in sun.nio.ch.FileChannelImpl */
-
 JNIEXPORT jlong JNICALL
-Java_sun_nio_ch_FileChannelImpl_initIDs(JNIEnv *env, jclass clazz)
+Java_sun_nio_ch_FileChannelImpl_allocationGranularity0(JNIEnv *env, jclass clazz)
 {
     jlong pageSize = sysconf(_SC_PAGESIZE);
-    chan_fd = (*env)->GetFieldID(env, clazz, "fd", "Ljava/io/FileDescriptor;");
     return pageSize;
 }
 
@@ -73,11 +70,10 @@ handle(JNIEnv *env, jlong rv, char *msg)
 
 
 JNIEXPORT jlong JNICALL
-Java_sun_nio_ch_FileChannelImpl_map0(JNIEnv *env, jobject this,
+Java_sun_nio_ch_FileChannelImpl_map0(JNIEnv *env, jobject this, jobject fdo,
                                      jint prot, jlong off, jlong len, jboolean map_sync)
 {
     void *mapAddress = 0;
-    jobject fdo = (*env)->GetObjectField(env, this, chan_fd);
     jint fd = fdval(env, fdo);
     int protections = 0;
     int flags = 0;

src/java.base/windows/native/libnio/ch/FileChannelImpl.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2022, 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
@@ -36,20 +36,16 @@
 #include <Mswsock.h>
 #pragma comment(lib, "Mswsock.lib")
 
-static jfieldID chan_fd; /* id for jobject 'fd' in java.io.FileChannel */
-
 /**************************************************************
- * static method to store field ID's in initializers
+ * static method to retrieve the allocation granularity
- * and retrieve the allocation granularity
  */
 JNIEXPORT jlong JNICALL
-Java_sun_nio_ch_FileChannelImpl_initIDs(JNIEnv *env, jclass clazz)
+Java_sun_nio_ch_FileChannelImpl_allocationGranularity0(JNIEnv *env, jclass clazz)
 {
     SYSTEM_INFO si;
     jint align;
     GetSystemInfo(&si);
     align = si.dwAllocationGranularity;
-    chan_fd = (*env)->GetFieldID(env, clazz, "fd", "Ljava/io/FileDescriptor;");
     return align;
 }
 
@@ -59,7 +55,7 @@ Java_sun_nio_ch_FileChannelImpl_initIDs(JNIEnv *env, jclass clazz)
  */
 
 JNIEXPORT jlong JNICALL
-Java_sun_nio_ch_FileChannelImpl_map0(JNIEnv *env, jobject this,
+Java_sun_nio_ch_FileChannelImpl_map0(JNIEnv *env, jobject this, jobject fdo,
                                      jint prot, jlong off, jlong len, jboolean map_sync)
 {
     void *mapAddress = 0;
@@ -68,7 +64,6 @@ Java_sun_nio_ch_FileChannelImpl_map0(JNIEnv *env, jobject this,
     jlong maxSize = off + len;
     jint lowLen = (jint)(maxSize);
     jint highLen = (jint)(maxSize >> 32);
-    jobject fdo = (*env)->GetObjectField(env, this, chan_fd);
     HANDLE fileHandle = (HANDLE)(handleval(env, fdo));
     HANDLE mapping;
     DWORD mapAccess = FILE_MAP_READ;