On Fri, Jun 17, 2022 at 09:43:33AM +0200, David Hildenbrand wrote:
> VmemmapSelfHosted, then the function names get nicer.
Definitely.
>
> > +#endif
> > +
> > /*
> > * On an anonymous page mapped into a user virtual memory area,
> > * page->mapping points to its anon_vma, not to a struct address_space;
> > diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
> > index 1089ea8a9c98..e2de7ed27e9e 100644
> > --- a/mm/hugetlb_vmemmap.c
> > +++ b/mm/hugetlb_vmemmap.c
> > @@ -101,6 +101,14 @@ void hugetlb_vmemmap_free(struct hstate *h, struct page *head)
> > {
> > unsigned long vmemmap_addr = (unsigned long)head;
> > unsigned long vmemmap_end, vmemmap_reuse, vmemmap_pages;
> > + struct mem_section *ms = __pfn_to_section(page_to_pfn(head));
> > + struct page *memmap;
> > +
> > + memmap = sparse_decode_mem_map(ms->section_mem_map,
> > + pfn_to_section_nr(page_to_pfn(head)));
>
> Why can't we check the head page directly? Either I need more coffee or
> this can be simplified.
Uhm, maybe I'm the one who needs coffe here but we have something like:
[ hot-plugges section ]
[memmap pages][normal pages]
we only mark as VmemmapSelfHosted the memmap pages.
head page points to [normal pages] range, that is why we need to go
and get its mem_map to see whether those pages are marked.
Does it make sense? Or am I missing something?
> > +
> > + if (PageVmemmap_self_hosted(memmap))
>
> Maybe that's the right place for a comment, an ascii art, and how it is
> safe to only check the first vmemmap page due to alignment restrictions.
Yes, definitely worth putting in a comment.
> > + /*
> > + * Let us flag self-hosted memmap
> > + */
>
> I think that comment can be dropped because the code does exactly that.
Yeah, was mainly to picture it, but it needs to go as it is worthless.
--
Oscar Salvador
SUSE Labs
