Function mount

src/linux/fs.cpp:479–517

Try<Nothing> mount(const Option<string>& _source,
                   const string& target,
                   const Option<string>& _type,
                   unsigned long flags,
                   const void* data)
{
  const char * source = _source.isSome() ? _source->c_str() : nullptr;
  const char * type = _type.isSome() ? _type->c_str() : nullptr;

  // The prototype of function 'mount' on Linux is as follows:
  // int mount(const char *source,
  //           const char *target,
  //           const char *filesystemtype,
  //           unsigned long mountflags,
  //           const void *data);
  if (::mount(source, target.c_str(), type, flags, data) < 0) {
    return ErrnoError();
  }

  const unsigned READ_ONLY_FLAG = MS_BIND | MS_RDONLY;
  const unsigned READ_ONLY_MASK = MS_BIND | MS_RDONLY | MS_REC;

  // Bind mounts need to be remounted for the read-only flag to take
  // effect. If this was a read-only bind mount, automatically remount
  // so that every caller doesn't have to deal with this. We don't do
  // anything if this was already a remount.
  if ((flags & (READ_ONLY_FLAG | MS_REMOUNT)) == READ_ONLY_FLAG) {
    if (::mount(
            nullptr,
            target.c_str(),
            nullptr,
            MS_REMOUNT | (flags & READ_ONLY_MASK),
            nullptr) < 0) {
      return ErrnoError("Read-only remount failed");
    }
  }

  return Nothing();
}


Try<Nothing> mount(const Option<string>& source,