On Mon, Dec 7, 2020 at 8:39 PM David Hildenbrand <david@xxxxxxxxxx> wrote:
>
> On 30.11.20 16:18, Muchun Song wrote:
> > In the later patch, we can use the free_vmemmap_page() to free the
> > unused vmemmap pages and initialize a page for vmemmap page using
> > via prepare_vmemmap_page().
> >
> > Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> > ---
> > include/linux/bootmem_info.h | 24 ++++++++++++++++++++++++
> > 1 file changed, 24 insertions(+)
> >
> > diff --git a/include/linux/bootmem_info.h b/include/linux/bootmem_info.h
> > index 4ed6dee1adc9..239e3cc8f86c 100644
> > --- a/include/linux/bootmem_info.h
> > +++ b/include/linux/bootmem_info.h
> > @@ -3,6 +3,7 @@
> > #define __LINUX_BOOTMEM_INFO_H
> >
> > #include <linux/mmzone.h>
> > +#include <linux/mm.h>
> >
> > /*
> > * Types for free bootmem stored in page->lru.next. These have to be in
> > @@ -22,6 +23,29 @@ void __init register_page_bootmem_info_node(struct pglist_data *pgdat);
> > void get_page_bootmem(unsigned long info, struct page *page,
> > unsigned long type);
> > void put_page_bootmem(struct page *page);
> > +
> > +static inline void free_vmemmap_page(struct page *page)
> > +{
> > + VM_WARN_ON(!PageReserved(page) || page_ref_count(page) != 2);
> > +
> > + /* bootmem page has reserved flag in the reserve_bootmem_region */
> > + if (PageReserved(page)) {
> > + unsigned long magic = (unsigned long)page->freelist;
> > +
> > + if (magic == SECTION_INFO || magic == MIX_SECTION_INFO)
> > + put_page_bootmem(page);
> > + else
> > + WARN_ON(1);
> > + }
> > +}
> > +
> > +static inline void prepare_vmemmap_page(struct page *page)
> > +{
> > + unsigned long section_nr = pfn_to_section_nr(page_to_pfn(page));
> > +
> > + get_page_bootmem(section_nr, page, SECTION_INFO);
> > + mark_page_reserved(page);
> > +}
>
> Can you clarify in the description when exactly these functions are
> called and on which type of pages?
Will do.
>
> Would indicating "bootmem" in the function names make it clearer what we
> are dealing with?
>
> E.g., any memory allocated via the memblock allocator and not via the
> buddy will be makred reserved already in the memmap. It's unclear to me
> why we need the mark_page_reserved() here - can you enlighten me? :)
Very thanks for your suggestions.
>
> --
> Thanks,
>
> David / dhildenb
>
--
Yours,
Muchun
