LevelDB-course-Lab/util/env_posix_test.cc

// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.

#include <sys/resource.h>
#include <sys/wait.h>
#include <unistd.h>

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <unordered_set>
#include <vector>

#include "leveldb/env.h"
#include "port/port.h"
#include "util/env_posix_test_helper.h"
#include "util/testharness.h"

#if HAVE_O_CLOEXEC

namespace {

// Exit codes for the helper process spawned by TestCloseOnExec* tests.
// Useful for debugging test failures.
constexpr int kTextCloseOnExecHelperExecFailedCode = 61;
constexpr int kTextCloseOnExecHelperDup2FailedCode = 62;
constexpr int kTextCloseOnExecHelperFoundOpenFdCode = 63;

// Global set by main() and read in TestCloseOnExec.
//
// The argv[0] value is stored in a std::vector instead of a std::string because
// std::string does not return a mutable pointer to its buffer until C++17.
//
// The vector stores the string pointed to by argv[0], plus the trailing null.
std::vector<char>* GetArgvZero() {
  static std::vector<char> program_name;
  return &program_name;
}

// Command-line switch used to run this test as the CloseOnExecSwitch helper.
static const char kTestCloseOnExecSwitch[] = "--test-close-on-exec-helper";

// Executed in a separate process by TestCloseOnExec* tests.
//
// main() delegates to this function when the test executable is launched with
// a special command-line switch. TestCloseOnExec* tests fork()+exec() the test
// executable and pass the special command-line switch.
//

// main() delegates to this function when the test executable is launched with
// a special command-line switch. TestCloseOnExec* tests fork()+exec() the test
// executable and pass the special command-line switch.
//
// When main() delegates to this function, the process probes whether a given
// file descriptor is open, and communicates the result via its exit code.
int TestCloseOnExecHelperMain(char* pid_arg) {
  int fd = std::atoi(pid_arg);
  // When given the same file descriptor twice, dup2() returns -1 if the
  // file descriptor is closed, or the given file descriptor if it is open.
  if (::dup2(fd, fd) == fd) {
    std::fprintf(stderr, "Unexpected open fd %d\n", fd);
    return kTextCloseOnExecHelperFoundOpenFdCode;
  }
  // Double-check that dup2() is saying the file descriptor is closed.
  if (errno != EBADF) {
    std::fprintf(stderr, "Unexpected errno after calling dup2 on fd %d: %s\n",
                 fd, std::strerror(errno));
    return kTextCloseOnExecHelperDup2FailedCode;
  }
  return 0;
}

// File descriptors are small non-negative integers.
//
// Returns void so the implementation can use ASSERT_EQ.
void GetMaxFileDescriptor(int* result_fd) {
  // Get the maximum file descriptor number.
  ::rlimit fd_rlimit;
  ASSERT_EQ(0, ::getrlimit(RLIMIT_NOFILE, &fd_rlimit));
  *result_fd = fd_rlimit.rlim_cur;
}

// Iterates through all possible FDs and returns the currently open ones.
//
// Returns void so the implementation can use ASSERT_EQ.
void GetOpenFileDescriptors(std::unordered_set<int>* open_fds) {
  int max_fd = 0;
  GetMaxFileDescriptor(&max_fd);

  for (int fd = 0; fd < max_fd; ++fd) {
    if (::dup2(fd, fd) != fd) {
      // When given the same file descriptor twice, dup2() returns -1 if the
      // file descriptor is closed, or the given file descriptor if it is open.
      //
      // Double-check that dup2() is saying the fd is closed.
      ASSERT_EQ(EBADF, errno)
          << "dup2() should set errno to EBADF on closed file descriptors";
      continue;
    }
    open_fds->insert(fd);
  }
}

// Finds an FD open since a previous call to GetOpenFileDescriptors().
//
// |baseline_open_fds| is the result of a previous GetOpenFileDescriptors()
// call. Assumes that exactly one FD was opened since that call.
//
// Returns void so the implementation can use ASSERT_EQ.
void GetNewlyOpenedFileDescriptor(
    const std::unordered_set<int>& baseline_open_fds, int* result_fd) {
  std::unordered_set<int> open_fds;
  GetOpenFileDescriptors(&open_fds);
  for (int fd : baseline_open_fds) {
    ASSERT_EQ(1, open_fds.count(fd))
        << "Previously opened file descriptor was closed during test setup";
    open_fds.erase(fd);
  }
  ASSERT_EQ(1, open_fds.size())
      << "Expected exactly one newly opened file descriptor during test setup";
  *result_fd = *open_fds.begin();
}

// Check that a fork()+exec()-ed child process does not have an extra open FD.
void CheckCloseOnExecDoesNotLeakFDs(
    const std::unordered_set<int>& baseline_open_fds) {
  // Prepare the argument list for the child process.
  // execv() wants mutable buffers.
  char switch_buffer[sizeof(kTestCloseOnExecSwitch)];
  std::memcpy(switch_buffer, kTestCloseOnExecSwitch,
              sizeof(kTestCloseOnExecSwitch));

  int probed_fd;
  GetNewlyOpenedFileDescriptor(baseline_open_fds, &probed_fd);
  std::string fd_string = std::to_string(probed_fd);
  std::vector<char> fd_buffer(fd_string.begin(), fd_string.end());
  fd_buffer.emplace_back('\0');

  // The helper process is launched with the command below.
  //      env_posix_tests --test-close-on-exec-helper 3
  char* child_argv[] = {GetArgvZero()->data(), switch_buffer, fd_buffer.data(),
                        nullptr};

  constexpr int kForkInChildProcessReturnValue = 0;
  int child_pid = fork();
  if (child_pid == kForkInChildProcessReturnValue) {
    ::execv(child_argv[0], child_argv);
    std::fprintf(stderr, "Error spawning child process: %s\n", strerror(errno));
    std::exit(kTextCloseOnExecHelperExecFailedCode);
  }

  int child_status = 0;
  ASSERT_EQ(child_pid, ::waitpid(child_pid, &child_status, 0));
  ASSERT_TRUE(WIFEXITED(child_status))
      << "The helper process did not exit with an exit code";
  ASSERT_EQ(0, WEXITSTATUS(child_status))
      << "The helper process encountered an error";
}

}  // namespace

#endif  // HAVE_O_CLOEXEC

namespace leveldb {

static const int kReadOnlyFileLimit = 4;
static const int kMMapLimit = 4;

class EnvPosixTest {
 public:
  static void SetFileLimits(int read_only_file_limit, int mmap_limit) {
    EnvPosixTestHelper::SetReadOnlyFDLimit(read_only_file_limit);
    EnvPosixTestHelper::SetReadOnlyMMapLimit(mmap_limit);
  }

  EnvPosixTest() : env_(Env::Default()) {}

  Env* env_;
};

TEST(EnvPosixTest, TestOpenOnRead) {
  // Write some test data to a single file that will be opened |n| times.
  std::string test_dir;
  ASSERT_OK(env_->GetTestDirectory(&test_dir));
  std::string test_file = test_dir + "/open_on_read.txt";

  FILE* f = fopen(test_file.c_str(), "we");
  ASSERT_TRUE(f != nullptr);
  const char kFileData[] = "abcdefghijklmnopqrstuvwxyz";
  fputs(kFileData, f);
  fclose(f);

  // Open test file some number above the sum of the two limits to force
  // open-on-read behavior of POSIX Env leveldb::RandomAccessFile.
  const int kNumFiles = kReadOnlyFileLimit + kMMapLimit + 5;
  leveldb::RandomAccessFile* files[kNumFiles] = {0};
  for (int i = 0; i < kNumFiles; i++) {
    ASSERT_OK(env_->NewRandomAccessFile(test_file, &files[i]));
  }
  char scratch;
  Slice read_result;
  for (int i = 0; i < kNumFiles; i++) {
    ASSERT_OK(files[i]->Read(i, 1, &read_result, &scratch));
    ASSERT_EQ(kFileData[i], read_result[0]);
  }
  for (int i = 0; i < kNumFiles; i++) {
    delete files[i];
  }
  ASSERT_OK(env_->DeleteFile(test_file));
}

#if HAVE_O_CLOEXEC

TEST(EnvPosixTest, TestCloseOnExecSequentialFile) {
  std::unordered_set<int> open_fds;
  GetOpenFileDescriptors(&open_fds);

  std::string test_dir;
  ASSERT_OK(env_->GetTestDirectory(&test_dir));
  std::string file_path = test_dir + "/close_on_exec_sequential.txt";
  ASSERT_OK(WriteStringToFile(env_, "0123456789", file_path));

  leveldb::SequentialFile* file = nullptr;
  ASSERT_OK(env_->NewSequentialFile(file_path, &file));
  CheckCloseOnExecDoesNotLeakFDs(open_fds);
  delete file;

  ASSERT_OK(env_->DeleteFile(file_path));
}

TEST(EnvPosixTest, TestCloseOnExecRandomAccessFile) {
  std::unordered_set<int> open_fds;
  GetOpenFileDescriptors(&open_fds);

  std::string test_dir;
  ASSERT_OK(env_->GetTestDirectory(&test_dir));
  std::string file_path = test_dir + "/close_on_exec_random_access.txt";
  ASSERT_OK(WriteStringToFile(env_, "0123456789", file_path));

  // Exhaust the RandomAccessFile mmap limit. This way, the test
  // RandomAccessFile instance below is backed by a file descriptor, not by an
  // mmap region.
  leveldb::RandomAccessFile* mmapped_files[kReadOnlyFileLimit] = {nullptr};
  for (int i = 0; i < kReadOnlyFileLimit; i++) {
    ASSERT_OK(env_->NewRandomAccessFile(file_path, &mmapped_files[i]));
  }

  leveldb::RandomAccessFile* file = nullptr;
  ASSERT_OK(env_->NewRandomAccessFile(file_path, &file));
  CheckCloseOnExecDoesNotLeakFDs(open_fds);
  delete file;

  for (int i = 0; i < kReadOnlyFileLimit; i++) {
    delete mmapped_files[i];
  }
  ASSERT_OK(env_->DeleteFile(file_path));
}

TEST(EnvPosixTest, TestCloseOnExecWritableFile) {
  std::unordered_set<int> open_fds;
  GetOpenFileDescriptors(&open_fds);

  std::string test_dir;
  ASSERT_OK(env_->GetTestDirectory(&test_dir));
  std::string file_path = test_dir + "/close_on_exec_writable.txt";
  ASSERT_OK(WriteStringToFile(env_, "0123456789", file_path));

  leveldb::WritableFile* file = nullptr;
  ASSERT_OK(env_->NewWritableFile(file_path, &file));
  CheckCloseOnExecDoesNotLeakFDs(open_fds);
  delete file;

  ASSERT_OK(env_->DeleteFile(file_path));
}

TEST(EnvPosixTest, TestCloseOnExecAppendableFile) {
  std::unordered_set<int> open_fds;
  GetOpenFileDescriptors(&open_fds);

  std::string test_dir;
  ASSERT_OK(env_->GetTestDirectory(&test_dir));
  std::string file_path = test_dir + "/close_on_exec_appendable.txt";
  ASSERT_OK(WriteStringToFile(env_, "0123456789", file_path));

  leveldb::WritableFile* file = nullptr;
  ASSERT_OK(env_->NewAppendableFile(file_path, &file));
  CheckCloseOnExecDoesNotLeakFDs(open_fds);
  delete file;

  ASSERT_OK(env_->DeleteFile(file_path));
}

TEST(EnvPosixTest, TestCloseOnExecLockFile) {
  std::unordered_set<int> open_fds;
  GetOpenFileDescriptors(&open_fds);

  std::string test_dir;
  ASSERT_OK(env_->GetTestDirectory(&test_dir));
  std::string file_path = test_dir + "/close_on_exec_lock.txt";
  ASSERT_OK(WriteStringToFile(env_, "0123456789", file_path));

  leveldb::FileLock* lock = nullptr;
  ASSERT_OK(env_->LockFile(file_path, &lock));
  CheckCloseOnExecDoesNotLeakFDs(open_fds);
  ASSERT_OK(env_->UnlockFile(lock));

  ASSERT_OK(env_->DeleteFile(file_path));
}

TEST(EnvPosixTest, TestCloseOnExecLogger) {
  std::unordered_set<int> open_fds;
  GetOpenFileDescriptors(&open_fds);

  std::string test_dir;
  ASSERT_OK(env_->GetTestDirectory(&test_dir));
  std::string file_path = test_dir + "/close_on_exec_logger.txt";
  ASSERT_OK(WriteStringToFile(env_, "0123456789", file_path));

  leveldb::Logger* file = nullptr;
  ASSERT_OK(env_->NewLogger(file_path, &file));
  CheckCloseOnExecDoesNotLeakFDs(open_fds);
  delete file;

  ASSERT_OK(env_->DeleteFile(file_path));
}

#endif  // HAVE_O_CLOEXEC

}  // namespace leveldb

int main(int argc, char** argv) {
#if HAVE_O_CLOEXEC
  // Check if we're invoked as a helper program, or as the test suite.
  for (int i = 1; i < argc; ++i) {
    if (!std::strcmp(argv[i], kTestCloseOnExecSwitch)) {
      return TestCloseOnExecHelperMain(argv[i + 1]);
    }
  }

  // Save argv[0] early, because googletest may modify argv.
  GetArgvZero()->assign(argv[0], argv[0] + std::strlen(argv[0]) + 1);
#endif  // HAVE_O_CLOEXEC

  // All tests currently run with the same read-only file limits.
  leveldb::EnvPosixTest::SetFileLimits(leveldb::kReadOnlyFileLimit,
                                       leveldb::kMMapLimit);
  return leveldb::test::RunAllTests();
}