/*

 * Copyright (c) 2015, 2018, 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 "gc/z/zBackingFile_linux_x86.hpp"

#include "gc/z/zBackingPath_linux_x86.hpp"

#include "gc/z/zErrno.hpp"

#include "gc/z/zLargePages.inline.hpp"

#include "logging/log.hpp"

#include "runtime/init.hpp"

#include "runtime/os.hpp"

#include "utilities/align.hpp"

#include "utilities/debug.hpp"

#include <fcntl.h>

#include <sys/mman.h>

#include <sys/stat.h>

#include <sys/statfs.h>

#include <sys/types.h>

#include <unistd.h>

// Filesystem names

#define ZFILESYSTEM_TMPFS                "tmpfs"

#define ZFILESYSTEM_HUGETLBFS            "hugetlbfs"

// Sysfs file for transparent huge page on tmpfs

#define ZFILENAME_SHMEM_ENABLED          "/sys/kernel/mm/transparent_hugepage/shmem_enabled"

// Default mount points

#define ZMOUNTPOINT_TMPFS                "/dev/shm"

#define ZMOUNTPOINT_HUGETLBFS            "/hugepages"

// Java heap filename

#define ZFILENAME_HEAP                   "java_heap"

// Support for building on older Linux systems

#ifndef __NR_memfd_create

#define __NR_memfd_create                319

#endif

#ifndef MFD_CLOEXEC

#define MFD_CLOEXEC                      0x0001U

#endif

#ifndef MFD_HUGETLB

#define MFD_HUGETLB                      0x0004U

#endif

#ifndef O_CLOEXEC

#define O_CLOEXEC                        02000000

#endif

#ifndef O_TMPFILE

#define O_TMPFILE                        (020000000 | O_DIRECTORY)

#endif

// Filesystem types, see statfs(2)

#ifndef TMPFS_MAGIC

#define TMPFS_MAGIC                      0x01021994

#endif

#ifndef HUGETLBFS_MAGIC

#define HUGETLBFS_MAGIC                  0x958458f6

#endif

static int z_memfd_create(const char *name, unsigned int flags) {

  return syscall(__NR_memfd_create, name, flags);

}

ZBackingFile::ZBackingFile() :

    _fd(-1),

    _filesystem(0),

    _initialized(false) {

  // Create backing file

  _fd = create_fd(ZFILENAME_HEAP);

  if (_fd == -1) {

    return;

  }

  // Get filesystem type

  struct statfs statfs_buf;

  if (fstatfs(_fd, &statfs_buf) == -1) {

    ZErrno err;

    log_error(gc, init)("Failed to determine filesystem type for backing file (%s)", err.to_string());

    return;

  }

  _filesystem = statfs_buf.f_type;

  // Make sure we're on a supported filesystem

  if (!is_tmpfs() && !is_hugetlbfs()) {

    log_error(gc, init)("Backing file must be located on a %s or a %s filesystem", ZFILESYSTEM_TMPFS, ZFILESYSTEM_HUGETLBFS);

    return;

  }

  // Make sure the filesystem type matches requested large page type

  if (ZLargePages::is_transparent() && !is_tmpfs()) {

    log_error(gc, init)("-XX:+UseTransparentHugePages can only be enable when using a %s filesystem", ZFILESYSTEM_TMPFS);

    return;

  }

  if (ZLargePages::is_transparent() && !tmpfs_supports_transparent_huge_pages()) {

    log_error(gc, init)("-XX:+UseTransparentHugePages on a %s filesystem not supported by kernel", ZFILESYSTEM_TMPFS);

    return;

  }

  if (ZLargePages::is_explicit() && !is_hugetlbfs()) {

    log_error(gc, init)("-XX:+UseLargePages (without -XX:+UseTransparentHugePages) can only be enabled when using a %s filesystem", ZFILESYSTEM_HUGETLBFS);

    return;

  }

  if (!ZLargePages::is_explicit() && is_hugetlbfs()) {

    log_error(gc, init)("-XX:+UseLargePages must be enabled when using a %s filesystem", ZFILESYSTEM_HUGETLBFS);

    return;

  }

  // Successfully initialized

  _initialized = true;

}

int ZBackingFile::create_mem_fd(const char* name) const {

  // Create file name

  char filename[PATH_MAX];

  snprintf(filename, sizeof(filename), "%s%s", name, ZLargePages::is_explicit() ? ".hugetlb" : "");

  // Create file

  const int extra_flags = ZLargePages::is_explicit() ? MFD_HUGETLB : 0;

  const int fd = z_memfd_create(filename, MFD_CLOEXEC | extra_flags);

  if (fd == -1) {

    ZErrno err;

    log_debug(gc, init)("Failed to create memfd file (%s)",

                        ((UseLargePages && err == EINVAL) ? "Hugepages not supported" : err.to_string()));

    return -1;

  }

  log_debug(gc, init)("Heap backed by file /memfd:%s", filename);

  return fd;

}

int ZBackingFile::create_file_fd(const char* name) const {

  const char* const filesystem = ZLargePages::is_explicit() ? ZFILESYSTEM_HUGETLBFS : ZFILESYSTEM_TMPFS;

  const char* const mountpoint = ZLargePages::is_explicit() ? ZMOUNTPOINT_HUGETLBFS : ZMOUNTPOINT_TMPFS;

  // Find mountpoint

  ZBackingPath path(filesystem, mountpoint);

  if (path.get() == NULL) {

    log_error(gc, init)("Use -XX:ZPath to specify the path to a %s filesystem", filesystem);

    return -1;

  }

  // Try to create an anonymous file using the O_TMPFILE flag. Note that this

  // flag requires kernel >= 3.11. If this fails we fall back to open/unlink.

  const int fd_anon = open(path.get(), O_TMPFILE|O_EXCL|O_RDWR|O_CLOEXEC, S_IRUSR|S_IWUSR);

  if (fd_anon == -1) {

    ZErrno err;

    log_debug(gc, init)("Failed to create anonymouns file in %s (%s)", path.get(),

                        (err == EINVAL ? "Not supported" : err.to_string()));

  } else {

    // Get inode number for anonymous file

    struct stat stat_buf;

    if (fstat(fd_anon, &stat_buf) == -1) {

      ZErrno err;

      log_error(gc, init)("Failed to determine inode number for anonymous file (%s)", err.to_string());

      return -1;

    }

    log_debug(gc, init)("Heap backed by file %s/#" UINT64_FORMAT, path.get(), (uint64_t)stat_buf.st_ino);

    return fd_anon;

  }

  log_debug(gc, init)("Falling back to open/unlink");

  // Create file name

  char filename[PATH_MAX];

  snprintf(filename, sizeof(filename), "%s/%s.%d", path.get(), name, os::current_process_id());

  // Create file

  const int fd = open(filename, O_CREAT|O_EXCL|O_RDWR|O_CLOEXEC, S_IRUSR|S_IWUSR);

  if (fd == -1) {

    ZErrno err;

    log_error(gc, init)("Failed to create file %s (%s)", filename, err.to_string());

    return -1;

  }

  // Unlink file

  if (unlink(filename) == -1) {

    ZErrno err;

    log_error(gc, init)("Failed to unlink file %s (%s)", filename, err.to_string());

    return -1;

  }

  log_debug(gc, init)("Heap backed by file %s", filename);

  return fd;

}

int ZBackingFile::create_fd(const char* name) const {

  if (ZPath == NULL) {

    // If the path is not explicitly specified, then we first try to create a memfd file

    // instead of looking for a tmpfd/hugetlbfs mount point. Note that memfd_create() might

    // not be supported at all (requires kernel >= 3.17), or it might not support large

    // pages (requires kernel >= 4.14). If memfd_create() fails, then we try to create a

    // file on an accessible tmpfs or hugetlbfs mount point.

    const int fd = create_mem_fd(name);

    if (fd != -1) {

      return fd;

    }

    log_debug(gc, init)("Falling back to searching for an accessible moint point");

  }

  return create_file_fd(name);

}

bool ZBackingFile::is_initialized() const {

  return _initialized;

}

int ZBackingFile::fd() const {

  return _fd;

}

bool ZBackingFile::is_tmpfs() const {

  return _filesystem == TMPFS_MAGIC;

}

bool ZBackingFile::is_hugetlbfs() const {

  return _filesystem == HUGETLBFS_MAGIC;

}

bool ZBackingFile::tmpfs_supports_transparent_huge_pages() const {

  // If the shmem_enabled file exists and is readable then we

  // know the kernel supports transparent huge pages for tmpfs.

  return access(ZFILENAME_SHMEM_ENABLED, R_OK) == 0;

}

bool ZBackingFile::try_split_and_expand_tmpfs(size_t offset, size_t length, size_t alignment) const {

  // Try first smaller part.

  const size_t offset0 = offset;

  const size_t length0 = align_up(length / 2, alignment);

  if (!try_expand_tmpfs(offset0, length0, alignment)) {

    return false;

  }

  // Try second smaller part.

  const size_t offset1 = offset0 + length0;

  const size_t length1 = length - length0;

  if (!try_expand_tmpfs(offset1, length1, alignment)) {

    return false;

  }

  return true;

}

bool ZBackingFile::try_expand_tmpfs(size_t offset, size_t length, size_t alignment) const {

  assert(length > 0, "Invalid length");

  assert(is_aligned(length, alignment), "Invalid length");

  ZErrno err = posix_fallocate(_fd, offset, length);

  if (err == EINTR && length > alignment) {

    // Calling posix_fallocate() with a large length can take a long

    // time to complete. When running profilers, such as VTune, this

    // syscall will be constantly interrupted by signals. Expanding

    // the file in smaller steps avoids this problem.

    return try_split_and_expand_tmpfs(offset, length, alignment);

  }

  if (err) {

    log_error(gc)("Failed to allocate backing file (%s)", err.to_string());

    return false;

  }

  return true;

}

bool ZBackingFile::expand_tmpfs(size_t offset, size_t length) const {

  assert(is_tmpfs(), "Wrong filesystem");

  return try_expand_tmpfs(offset, length, os::vm_page_size());

}

bool ZBackingFile::expand_hugetlbfs(size_t offset, size_t length) const {

  assert(is_hugetlbfs(), "Wrong filesystem");

  // Prior to kernel 4.3, hugetlbfs did not support posix_fallocate().

  // Instead of posix_fallocate() we can use a well-known workaround,

  // which involves truncating the file to requested size and then try

  // to map it to verify that there are enough huge pages available to

  // back it.

  while (ftruncate(_fd, offset + length) == -1) {

    ZErrno err;

    if (err != EINTR) {

      log_error(gc)("Failed to truncate backing file (%s)", err.to_string());

      return false;

    }

  }

  // If we fail mapping during initialization, i.e. when we are pre-mapping

  // the heap, then we wait and retry a few times before giving up. Otherwise

  // there is a risk that running JVMs back-to-back will fail, since there

  // is a delay between process termination and the huge pages owned by that

  // process being returned to the huge page pool and made available for new

  // allocations.

  void* addr = MAP_FAILED;

  const int max_attempts = 3;

  for (int attempt = 1; attempt <= max_attempts; attempt++) {

    addr = mmap(0, length, PROT_READ|PROT_WRITE, MAP_SHARED, _fd, offset);

    if (addr != MAP_FAILED || is_init_completed()) {

      // Mapping was successful or initialization phase has completed

      break;

    }

    ZErrno err;

    log_debug(gc)("Failed to map backing file (%s), attempt %d of %d",

                  err.to_string(), attempt, max_attempts);

    // Wait and retry in one second, in the hope that

    // huge pages will be available by then.

    sleep(1);

  }

  if (addr == MAP_FAILED) {

    // Not enough huge pages left

    ZErrno err;

    log_error(gc)("Failed to map backing file (%s)", err.to_string());

    return false;

  }

  // Successful mapping, unmap again. From now on the pages we mapped

  // will be reserved for this file.

  if (munmap(addr, length) == -1) {

    ZErrno err;

    log_error(gc)("Failed to unmap backing file (%s)", err.to_string());

    return false;

  }

  return true;

}

bool ZBackingFile::expand(size_t offset, size_t length) const {

  return is_hugetlbfs() ? expand_hugetlbfs(offset, length) : expand_tmpfs(offset, length);

}