On Wed, Aug 12, 2020 at 2:05 AM David Howells [off-list ref] wrote:

quoted

  {
     int fd, attrfd;

     fd = open(path, O_PATH);
     attrfd = openat(fd, name, O_ALT);
     close(fd);
     read(attrfd, value, size);
     close(attrfd);
  }

Please don't go down this path.  You're proposing five syscalls - including
creating two file descriptors - to do what fsinfo() does in one.

So what?  People argued against readfile() for exactly the opposite of
reasons, even though that's a lot less specialized than fsinfo().

Worried about performance?  Io-uring will allow you to do all those
five syscalls (or many more) with just one I/O submission.

Thanks,
Miklos