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

rev 16220 : 8168628: (fc) SIGBUS when extending file size to map it
Summary: Synchronize file extension and subsequent map0(); on Linux use fallocate64() instead of ftruncate64().
Reviewed-by: rehn, simonis, alanb

*** 1,7 ****
  /*
!  * Copyright (c) 2000, 2012, 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.  Oracle designates this
--- 1,7 ----
  /*
!  * Copyright (c) 2000, 2016, 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.  Oracle designates this
*** 184,193 ****
--- 184,214 ----
      return handle(env,
                    ftruncate64(fdval(env, fdo), size),
                    "Truncation failed");
  }
  
+ JNIEXPORT jint JNICALL
+ Java_sun_nio_ch_FileDispatcherImpl_allocate0(JNIEnv *env, jobject this,
+                                              jobject fdo, jlong size)
+ {
+ #if defined(__linux__)
+     /*
+      * On Linux, if the file size is being increased, then ftruncate64()
+      * will modify the metadata value of the size without actually allocating
+      * any blocks which can cause a SIGBUS error if the file is subsequently
+      * memory-mapped.
+      */
+     return handle(env,
+                   fallocate64(fdval(env, fdo), 0, 0, size),
+                   "Allocation failed");
+ #else
+     return handle(env,
+                   ftruncate64(fdval(env, fdo), size),
+                   "Truncation failed");
+ #endif
+ }
+ 
  JNIEXPORT jlong JNICALL
  Java_sun_nio_ch_FileDispatcherImpl_size0(JNIEnv *env, jobject this, jobject fdo)
  {
      jint fd = fdval(env, fdo);
      struct stat64 fbuf;