On Wed, 2018-08-01 at 17:12 -0700, Andrew Morton wrote:
> On Thu, 2 Aug 2018 00:36:36 +0100 Dmitry Safonov <[email protected]>
> wrote:
>
> > As many other projects, we use some shmalloc allocator.
> > At some point we need to make a part of allocated pages back
> > private to
> > process. And it should be populated straight away.
> > Check that (MAP_PRIVATE | MAP_POPULATE) actually copies the private
> > page.
> >
> > ...
> >
> > --- /dev/null
> > +++ b/tools/testing/selftests/vm/map_populate.c
> >
> > ...
> >
> > +#define BUG_ON(condition, description)
> > \
> > + do {
> > \
> > + if (condition) {
> > \
> > + fprintf(stderr, "[FAIL]\t%s:%d\t%s:%s\n",
> > __func__, \
> > + __LINE__, (description),
> > strerror(errno)); \
> > + exit(1);
> > \
> > + }
> > \
> > + } while (0)
>
> This is userspace. Why not use assert()?
I wanted to print errno too. Of cause it's possible to get it from
coredump - but I think it's easier if you get buildbot reply to see
what the error is from the log.
>
> >
> > ...
> >
> > +int main(int argc, char **argv)
> > +{
> > + int sock[2], child, ret;
> > + FILE *ftmp;
> > + unsigned long *smap;
> > +
> > + ftmp = tmpfile();
>
> Seems odd to putz around with stdio when you just want the fd.
> mkstemp(), maybe?
It needs a template and unlink() call.. I can do it.
I initially thought about memfd_create(), can change it that way.
The only downside is that it will be syscall(NR_memfd_create,...)
>
> > + BUG_ON(ftmp == 0, "tmpfile()");
> > +
> > + ret = ftruncate(fileno(ftmp), MMAP_SZ);
> > + BUG_ON(ret, "ftruncate()");
> > +
> > + smap = mmap(0, MMAP_SZ, PROT_READ | PROT_WRITE,
> > + MAP_SHARED, fileno(ftmp), 0);
> > + BUG_ON(smap == MAP_FAILED, "mmap()");
> > +
> > + *smap = 0xdeadbabe;
> > + /* Probably unnecessary, but let it be. */
> > + ret = msync(smap, MMAP_SZ, MS_SYNC);
> > + BUG_ON(ret, "msync()");
> > +
> > + ret = socketpair(PF_LOCAL, SOCK_SEQPACKET, 0, sock);
> > + BUG_ON(ret, "socketpair()");
> > +
> > + child = fork();
> > + BUG_ON(child == -1, "fork()");
> > +
> > + if (child) {
> > + ret = close(sock[0]);
> > + BUG_ON(ret, "close()");
> > +
> > + return parent_f(sock[1], smap, child);
> > + }
> > +
> > + ret = close(sock[1]);
> > + BUG_ON(ret, "close()");
> > +
> > + return child_f(sock[0], smap, fileno(ftmp));
> > +}
> >
> > ...
> >
