Re: [PATCH v2 2/3] selftests/memfd_secret: add vmsplice() test

[David Hildenbrand]

> > +static void test_vmsplice(int fd, const char *desc)
> > +{
> > +       ssize_t transferred;
> > +       struct iovec iov;
> > +       int pipefd[2];
> > +       char *mem;
> > +
> > +       if (pipe(pipefd)) {
> > +               fail("pipe failed: %s\n", strerror(errno));
> > +               return;
> > +       }
> > +
> > +       mem = mmap(NULL, page_size, prot, mode, fd, 0);
> > +       if (mem == MAP_FAILED) {
> > +               fail("Unable to mmap secret memory\n");
> > +               goto close_pipe;
> > +       }
> > +
> > +       /*
> > +        * vmsplice() may use GUP-fast, which must also fail. Prefault the
> > +        * page table, so GUP-fast could find it.
> > +        */
> > +       memset(mem, PATTERN, page_size);
>
> Shouldn't the non-prefault case be tested as well?

That's the "easy" case where GUP-fast is never involved, and it should 
mostly be covered by the ptrace/process_vm_read() tests already.

--
Cheers,

David / dhildenb