--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/os_cpu/linux_aarch64/gc/z/zBackingPath_linux_aarch64.cpp	Thu Jun 13 15:24:34 2019 +0100
@@ -0,0 +1,149 @@
+/*
+ * Copyright (c) 2016, 2019, 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.
+ */
+
+#include "precompiled.hpp"
+#include "gc/z/zArray.inline.hpp"
+#include "zBackingPath_linux_aarch64.hpp"
+#include "gc/z/zErrno.hpp"
+#include "logging/log.hpp"
+
+#include <stdio.h>
+#include <unistd.h>
+
+// Mount information, see proc(5) for more details.
+#define PROC_SELF_MOUNTINFO        "/proc/self/mountinfo"
+
+ZBackingPath::ZBackingPath(const char* filesystem, const char** preferred_mountpoints) {
+  if (ZPath != NULL) {
+    // Use specified path
+    _path = strdup(ZPath);
+  } else {
+    // Find suitable path
+    _path = find_mountpoint(filesystem, preferred_mountpoints);
+  }
+}
+
+ZBackingPath::~ZBackingPath() {
+  free(_path);
+  _path = NULL;
+}
+
+char* ZBackingPath::get_mountpoint(const char* line, const char* filesystem) const {
+  char* line_mountpoint = NULL;
+  char* line_filesystem = NULL;
+
+  // Parse line and return a newly allocated string containing the mount point if
+  // the line contains a matching filesystem and the mount point is accessible by
+  // the current user.
+  if (sscanf(line, "%*u %*u %*u:%*u %*s %ms %*[^-]- %ms", &line_mountpoint, &line_filesystem) != 2 ||
+      strcmp(line_filesystem, filesystem) != 0 ||
+      access(line_mountpoint, R_OK|W_OK|X_OK) != 0) {
+    // Not a matching or accessible filesystem
+    free(line_mountpoint);
+    line_mountpoint = NULL;
+  }
+
+  free(line_filesystem);
+
+  return line_mountpoint;
+}
+
+void ZBackingPath::get_mountpoints(const char* filesystem, ZArray<char*>* mountpoints) const {
+  FILE* fd = fopen(PROC_SELF_MOUNTINFO, "r");
+  if (fd == NULL) {
+    ZErrno err;
+    log_error(gc)("Failed to open %s: %s", PROC_SELF_MOUNTINFO, err.to_string());
+    return;
+  }
+
+  char* line = NULL;
+  size_t length = 0;
+
+  while (getline(&line, &length, fd) != -1) {
+    char* const mountpoint = get_mountpoint(line, filesystem);
+    if (mountpoint != NULL) {
+      mountpoints->add(mountpoint);
+    }
+  }
+
+  free(line);
+  fclose(fd);
+}
+
+void ZBackingPath::free_mountpoints(ZArray<char*>* mountpoints) const {
+  ZArrayIterator<char*> iter(mountpoints);
+  for (char* mountpoint; iter.next(&mountpoint);) {
+    free(mountpoint);
+  }
+  mountpoints->clear();
+}
+
+char* ZBackingPath::find_preferred_mountpoint(const char* filesystem,
+                                              ZArray<char*>* mountpoints,
+                                              const char** preferred_mountpoints) const {
+  // Find preferred mount point
+  ZArrayIterator<char*> iter1(mountpoints);
+  for (char* mountpoint; iter1.next(&mountpoint);) {
+    for (const char** preferred = preferred_mountpoints; *preferred != NULL; preferred++) {
+      if (!strcmp(mountpoint, *preferred)) {
+        // Preferred mount point found
+        return strdup(mountpoint);
+      }
+    }
+  }
+
+  // Preferred mount point not found
+  log_error(gc)("More than one %s filesystem found:", filesystem);
+  ZArrayIterator<char*> iter2(mountpoints);
+  for (char* mountpoint; iter2.next(&mountpoint);) {
+    log_error(gc)("  %s", mountpoint);
+  }
+
+  return NULL;
+}
+
+char* ZBackingPath::find_mountpoint(const char* filesystem, const char** preferred_mountpoints) const {
+  char* path = NULL;
+  ZArray<char*> mountpoints;
+
+  get_mountpoints(filesystem, &mountpoints);
+
+  if (mountpoints.size() == 0) {
+    // No mount point found
+    log_error(gc)("Failed to find an accessible %s filesystem", filesystem);
+  } else if (mountpoints.size() == 1) {
+    // One mount point found
+    path = strdup(mountpoints.at(0));
+  } else {
+    // More than one mount point found
+    path = find_preferred_mountpoint(filesystem, &mountpoints, preferred_mountpoints);
+  }
+
+  free_mountpoints(&mountpoints);
+
+  return path;
+}
+
+const char* ZBackingPath::get() const {
+  return _path;
+}