8322166: Files.isReadable/isWritable/isExecutable expensive when file does not exist

Reviewed-by: alanb

src/java.base/share/classes/java/nio/file/Files.java

@@ -80,6 +80,7 @@ import java.util.stream.StreamSupport;
 import jdk.internal.util.ArraysSupport;
 import sun.nio.ch.FileChannelImpl;
 import sun.nio.cs.UTF_8;
+import sun.nio.fs.AbstractFileSystemProvider;
 
 /**
  * This class consists exclusively of static methods that operate on files,
@@ -2609,7 +2610,11 @@ public final class Files {
      *          is invoked to check read access to the file.
      */
     public static boolean isReadable(Path path) {
-        return isAccessible(path, AccessMode.READ);
+        FileSystemProvider provider = provider(path);
+        if (provider instanceof AbstractFileSystemProvider afsp)
+            return afsp.isReadable(path);
+        else
+            return isAccessible(path, AccessMode.READ);
     }
 
     /**
@@ -2640,7 +2645,11 @@ public final class Files {
      *          is invoked to check write access to the file.
      */
     public static boolean isWritable(Path path) {
-        return isAccessible(path, AccessMode.WRITE);
+        FileSystemProvider provider = provider(path);
+        if (provider instanceof AbstractFileSystemProvider afsp)
+            return afsp.isWritable(path);
+        else
+            return isAccessible(path, AccessMode.WRITE);
     }
 
     /**
@@ -2675,7 +2684,11 @@ public final class Files {
      *          checkExec} is invoked to check execute access to the file.
      */
     public static boolean isExecutable(Path path) {
-        return isAccessible(path, AccessMode.EXECUTE);
+        FileSystemProvider provider = provider(path);
+        if (provider instanceof AbstractFileSystemProvider afsp)
+            return afsp.isExecutable(path);
+        else
+            return isAccessible(path, AccessMode.EXECUTE);
     }
 
     // -- Recursive operations --

src/java.base/share/classes/sun/nio/fs/AbstractFileSystemProvider.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2011, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2011, 2023, 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
@@ -25,8 +25,9 @@
 
 package sun.nio.fs;
 
-import java.nio.file.Path;
+import java.nio.file.AccessMode;
 import java.nio.file.LinkOption;
+import java.nio.file.Path;
 import java.nio.file.spi.FileSystemProvider;
 import java.io.IOException;
 import java.util.Map;
@@ -115,4 +116,40 @@ public abstract class AbstractFileSystemProvider extends FileSystemProvider {
      * If path is empty, then an empty byte[] is returned.
      */
     public abstract byte[] getSunPathForSocketFile(Path path);
+
+    /**
+     * Tests whether a file is readable.
+     */
+    public boolean isReadable(Path path) {
+        try {
+            checkAccess(path, AccessMode.READ);
+        } catch (IOException e) {
+            return false;
+        }
+        return true;
+    }
+
+    /**
+     * Tests whether a file is writable.
+     */
+    public boolean isWritable(Path path) {
+        try {
+            checkAccess(path, AccessMode.WRITE);
+        } catch (IOException e) {
+            return false;
+        }
+        return true;
+    }
+
+    /**
+     * Tests whether a file is executable.
+     */
+    public boolean isExecutable(Path path) {
+        try {
+            checkAccess(path, AccessMode.EXECUTE);
+        } catch (IOException e) {
+            return false;
+        }
+        return true;
+    }
 }

src/java.base/unix/classes/sun/nio/fs/UnixFileSystem.java

@@ -893,7 +893,9 @@ abstract class UnixFileSystem
             sourceAttrs = UnixFileAttributes.get(source, false);
             if (sourceAttrs.isDirectory()) {
                 // ensure source can be moved
-                access(source, W_OK);
+                int errno = access(source, W_OK);
+                if (errno != 0)
+                    new UnixException(errno).rethrowAsIOException(source);
             }
         } catch (UnixException x) {
             x.rethrowAsIOException(source);
@@ -1024,13 +1026,11 @@ abstract class UnixFileSystem
 
         // ensure source can be copied
         if (!sourceAttrs.isSymbolicLink() || flags.followLinks) {
-            try {
+            // the access(2) system call always follows links so it
-                // the access(2) system call always follows links so it
+            // is suppressed if the source is an unfollowed link
-                // is suppressed if the source is an unfollowed link
+            int errno = access(source, R_OK);
-                access(source, R_OK);
+            if (errno != 0)
-            } catch (UnixException exc) {
+                new UnixException(errno).rethrowAsIOException(source);
-                exc.rethrowAsIOException(source);
-            }
         }
 
         // get attributes of target file (don't follow links)

src/java.base/unix/classes/sun/nio/fs/UnixFileSystemProvider.java

@@ -349,11 +349,35 @@ public abstract class UnixFileSystemProvider
             }
             mode |= X_OK;
         }
-        try {
+        int errno = access(file, mode);
-            access(file, mode);
+        if (errno != 0)
-        } catch (UnixException exc) {
+            new UnixException(errno).rethrowAsIOException(file);
-            exc.rethrowAsIOException(file);
+    }
+
+    @Override
+    public boolean isReadable(Path path) {
+        UnixPath file = UnixPath.toUnixPath(path);
+        file.checkRead();
+        return access(file, R_OK) == 0;
+    }
+
+    @Override
+    public boolean isWritable(Path path) {
+        UnixPath file = UnixPath.toUnixPath(path);
+        file.checkWrite();
+        return access(file, W_OK) == 0;
+    }
+
+    @Override
+    public boolean isExecutable(Path path) {
+        UnixPath file = UnixPath.toUnixPath(path);
+        @SuppressWarnings("removal")
+        SecurityManager sm = System.getSecurityManager();
+        if (sm != null) {
+            // not cached
+            sm.checkExec(file.getPathForPermissionCheck());
         }
+        return access(file, X_OK) == 0;
     }
 
     @Override
@@ -561,7 +585,7 @@ public abstract class UnixFileSystemProvider
         if (Util.followLinks(options)) {
             UnixPath file = UnixPath.toUnixPath(path);
             file.checkRead();
-            return UnixNativeDispatcher.exists(file);
+            return access(file, F_OK) == 0;
         } else {
             return super.exists(path, options);
         }

src/java.base/unix/classes/sun/nio/fs/UnixNativeDispatcher.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2008, 2023, 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
@@ -597,34 +597,17 @@ class UnixNativeDispatcher {
     /**
      * access(const char* path, int amode);
      */
-    static void access(UnixPath path, int amode) throws UnixException {
+    static int access(UnixPath path, int amode) {
         try (NativeBuffer buffer = copyToNativeBuffer(path)) {
             long comp = Blocker.begin();
             try {
-                access0(buffer.address(), amode);
+                return access0(buffer.address(), amode);
             } finally {
                 Blocker.end(comp);
             }
         }
     }
-    private static native void access0(long pathAddress, int amode) throws UnixException;
+    private static native int access0(long pathAddress, int amode);
-
-    /**
-     * access(constant char* path, F_OK)
-     *
-     * @return true if the file exists, false otherwise
-     */
-    static boolean exists(UnixPath path) {
-        try (NativeBuffer buffer = copyToNativeBuffer(path)) {
-            long comp = Blocker.begin();
-            try {
-                return exists0(buffer.address());
-            } finally {
-                Blocker.end(comp);
-            }
-        }
-    }
-    private static native boolean exists0(long pathAddress);
 
     /**
      * struct passwd *getpwuid(uid_t uid);

src/java.base/unix/native/libnio/fs/UnixNativeDispatcher.c

@@ -1190,7 +1190,7 @@ Java_sun_nio_fs_UnixNativeDispatcher_realpath0(JNIEnv* env, jclass this,
     return result;
 }
 
-JNIEXPORT void JNICALL
+JNIEXPORT jint JNICALL
 Java_sun_nio_fs_UnixNativeDispatcher_access0(JNIEnv* env, jclass this,
     jlong pathAddress, jint amode)
 {
@@ -1198,17 +1198,8 @@ Java_sun_nio_fs_UnixNativeDispatcher_access0(JNIEnv* env, jclass this,
     const char* path = (const char*)jlong_to_ptr(pathAddress);
 
     RESTARTABLE(access(path, (int)amode), err);
-    if (err == -1) {
-        throwUnixException(env, errno);
-    }
-}
 
-JNIEXPORT jboolean JNICALL
+    return (err == -1) ? errno : 0;
-Java_sun_nio_fs_UnixNativeDispatcher_exists0(JNIEnv* env, jclass this, jlong pathAddress) {
-    int err;
-    const char* path = (const char*)jlong_to_ptr(pathAddress);
-    RESTARTABLE(access(path, F_OK), err);
-    return (err == 0) ? JNI_TRUE : JNI_FALSE;
 }
 
 JNIEXPORT void JNICALL