Clean up PosixWritableFile in env_posix.cc.

This is separated from the general cleanup because of the logic changes in SyncDirIfManifest(). General cleanup principles: * Use override when applicable. * Remove static when redundant (methods and globals in anonymous namespaces). * Use const on class members where possible. * Standardize on "status" for Status local variables. * Renames where clarity can be improved. * Qualify standard library names with std:: when possible, to distinguish from POSIX names. * Qualify POSIX names with the global namespace (::) when possible, to distinguish from standard library names. ------------- Created by MOE: https://github.com/google/moe MOE_MIGRATED_REVID=211709673
před 6 roky · bb88f25115
--- a/util/env_posix.cc
+++ b/util/env_posix.cc
@ -18,6 +18,7 @@
 #include <unistd.h>

 #include <atomic>
 #include <cstring>
 #include <deque>
 #include <limits>
 #include <set>
@ -44,7 +45,7 @@ namespace {
 static int open_read_only_file_limit = -1;
 static int mmap_limit = -1;

 static const size_t kBufSize = 65536;
 constexpr const size_t kWritableFileBufferSize = 65536;

 static Status PosixError(const std::string& context, int err_number) {
  if (err_number == ENOENT) {
@ -213,131 +214,165 @@ class PosixMmapReadableFile: public RandomAccessFile {
  }
 };

 class PosixWritableFile : public WritableFile {
 private:
  // buf_[0, pos_-1] contains data to be written to fd_.
  std::string filename_;
  int fd_;
  char buf_[kBufSize];
  size_t pos_;

 class PosixWritableFile final : public WritableFile {
 public:
  PosixWritableFile(const std::string& fname, int fd)
      : filename_(fname), fd_(fd), pos_(0) { }
  PosixWritableFile(std::string filename, int fd)
      : pos_(0), fd_(fd), is_manifest_(IsManifest(filename)),
        filename_(std::move(filename)), dirname_(Dirname(filename_)) {}

  ~PosixWritableFile() {
  ~PosixWritableFile() override {
    if (fd_ >= 0) {
      // Ignoring any potential errors
      Close();
    }
  }

  virtual Status Append(const Slice& data) {
    size_t n = data.size();
    const char* p = data.data();
  Status Append(const Slice& data) override {
    size_t write_size = data.size();
    const char* write_data = data.data();

    // Fit as much as possible into buffer.
    size_t copy = std::min(n, kBufSize - pos_);
    memcpy(buf_ + pos_, p, copy);
    p += copy;
    n -= copy;
    pos_ += copy;
    if (n == 0) {
    size_t copy_size = std::min(write_size, kWritableFileBufferSize - pos_);
    std::memcpy(buf_ + pos_, write_data, copy_size);
    write_data += copy_size;
    write_size -= copy_size;
    pos_ += copy_size;
    if (write_size == 0) {
      return Status::OK();
    }

    // Can't fit in buffer, so need to do at least one write.
    Status s = FlushBuffered();
    if (!s.ok()) {
      return s;
    Status status = FlushBuffer();
    if (!status.ok()) {
      return status;
    }

    // Small writes go to buffer, large writes are written directly.
    if (n < kBufSize) {
      memcpy(buf_, p, n);
      pos_ = n;
    if (write_size < kWritableFileBufferSize) {
      std::memcpy(buf_, write_data, write_size);
      pos_ = write_size;
      return Status::OK();
    }
    return WriteRaw(p, n);
    return WriteUnbuffered(write_data, write_size);
  }

  virtual Status Close() {
    Status result = FlushBuffered();
    const int r = close(fd_);
    if (r < 0 && result.ok()) {
      result = PosixError(filename_, errno);
  Status Close() override {
    Status status = FlushBuffer();
    const int close_result = ::close(fd_);
    if (close_result < 0 && status.ok()) {
      status = PosixError(filename_, errno);
    }
    fd_ = -1;
    return result;
    return status;
  }

  virtual Status Flush() {
    return FlushBuffered();
  }

  Status SyncDirIfManifest() {
    const char* f = filename_.c_str();
    const char* sep = strrchr(f, '/');
    Slice basename;
    std::string dir;
    if (sep == nullptr) {
      dir = ".";
      basename = f;
    } else {
      dir = std::string(f, sep - f);
      basename = sep + 1;
    }
    Status s;
    if (basename.starts_with("MANIFEST")) {
      int fd = open(dir.c_str(), O_RDONLY);
      if (fd < 0) {
        s = PosixError(dir, errno);
      } else {
        if (fsync(fd) < 0) {
          s = PosixError(dir, errno);
        }
        close(fd);
      }
    }
    return s;
  Status Flush() override {
    return FlushBuffer();
  }

  virtual Status Sync() {
  Status Sync() override {
    // Ensure new files referred to by the manifest are in the filesystem.
    Status s = SyncDirIfManifest();
    if (!s.ok()) {
      return s;
    //
    // This needs to happen before the manifest file is flushed to disk, to
    // avoid crashing in a state where the manifest refers to files that are not
    // yet on disk.
    Status status = SyncDirIfManifest();
    if (!status.ok()) {
      return status;
    }
    s = FlushBuffered();
    if (s.ok()) {
      if (fdatasync(fd_) != 0) {
        s = PosixError(filename_, errno);
      }

    status = FlushBuffer();
    if (status.ok() && ::fdatasync(fd_) != 0) {
      status = PosixError(filename_, errno);
    }
    return s;
    return status;
  }

 private:
  Status FlushBuffered() {
    Status s = WriteRaw(buf_, pos_);
  Status FlushBuffer() {
    Status status = WriteUnbuffered(buf_, pos_);
    pos_ = 0;
    return s;
    return status;
  }

  Status WriteRaw(const char* p, size_t n) {
    while (n > 0) {
      ssize_t r = write(fd_, p, n);
      if (r < 0) {
  Status WriteUnbuffered(const char* data, size_t size) {
    while (size > 0) {
      ssize_t write_result = ::write(fd_, data, size);
      if (write_result < 0) {
        if (errno == EINTR) {
          continue;  // Retry
        }
        return PosixError(filename_, errno);
      }
      p += r;
      n -= r;
      data += write_result;
      size -= write_result;
    }
    return Status::OK();
  }

  Status SyncDirIfManifest() {
    Status status;
    if (!is_manifest_) {
      return status;
    }

    int fd = ::open(dirname_.c_str(), O_RDONLY);
    if (fd < 0) {
      status = PosixError(dirname_, errno);
    } else {
      if (::fsync(fd) < 0) {
        status = PosixError(dirname_, errno);
      }
      ::close(fd);
    }
    return status;
  }

  // Returns the directory name in a path pointing to a file.
  //
  // Returns "." if the path does not contain any directory separator.
  static std::string Dirname(const std::string& filename) {
    std::string::size_type separator_pos = filename.rfind('/');
    if (separator_pos == std::string::npos) {
      return std::string(".");
    }
    // The filename component should not contain a path separator. If it does,
    // the splitting was done incorrectly.
    assert(filename.find('/', separator_pos + 1) == std::string::npos);

    return filename.substr(0, separator_pos);
  }

  // Extracts the file name from a path pointing to a file.
  //
  // The returned Slice points to |filename|'s data buffer, so it is only valid
  // while |filename| is alive and unchanged.
  static Slice Basename(const std::string& filename) {
    std::string::size_type separator_pos = filename.rfind('/');
    if (separator_pos == std::string::npos) {
      return Slice(filename);
    }
    // The filename component should not contain a path separator. If it does,
    // the splitting was done incorrectly.
    assert(filename.find('/', separator_pos + 1) == std::string::npos);

    return Slice(filename.data() + separator_pos + 1,
                 filename.length() - separator_pos - 1);
  }

  // True if the given file is a manifest file.
  static bool IsManifest(const std::string& filename) {
    return Basename(filename).starts_with("MANIFEST");
  }

  // buf_[0, pos_ - 1] contains data to be written to fd_.
  char buf_[kWritableFileBufferSize];
  size_t pos_;
  int fd_;

  const bool is_manifest_;  // True if the file's name starts with MANIFEST.
  const std::string filename_;
  const std::string dirname_;  // The directory of filename_.
 };

 static int LockOrUnlock(int fd, bool lock) {