Re: [PATCH v6 4/5] mm/sparse: Optimize memmap allocation during sparse_init()

Pavel Tatashin
2018-06-28T12:12:46Z

> > + if (nr_consumed_maps >= nr_present_sections) {
> > + pr_err("nr_consumed_maps goes beyond nr_present_sections\n");
> > + break;
> > + }
>
> Hi Baoquan,
>
> I am sure I am missing something here, but is this check really needed?
>
> I mean, for_each_present_section_nr() only returns the section nr if the section
> has been marked as SECTION_MARKED_PRESENT.
> That happens in memory_present(), where now we also increment nr_present_sections whenever
> we find a present section.
>
> So, for_each_present_section_nr() should return the same nr of section as nr_present_sections.
> Since we only increment nr_consumed_maps once in the loop, I am not so sure we can
> go beyond nr_present_sections.
>
> Did I overlook something?

You did not, this is basically a safety check. A BUG_ON() would be
better here. As, this something that should really not happening, and
would mean a bug in the current project.