Re: [PATCH v6 10/10] mm/memory_hotplug: Cleanup __remove_pages()

Oscar Salvador
2020-02-04T09:46:53Z

On Sun, Oct 06, 2019 at 10:56:46AM +0200, David Hildenbrand wrote:
> Let's drop the basically unused section stuff and simplify.
>
> Also, let's use a shorter variant to calculate the number of pages to
> the next section boundary.
>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Oscar Salvador <osalvador@suse.de>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Wei Yang <richardw.yang@linux.intel.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>

I have to confess that it took me while to wrap around my head
with the new min() change, but looks ok:

Reviewed-by: Oscar Salvador <osalvador@suse.de>

> ---
> mm/memory_hotplug.c | 17 ++++++-----------
> 1 file changed, 6 insertions(+), 11 deletions(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 843481bd507d..2275240cfa10 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -490,25 +490,20 @@ static void __remove_section(unsigned long pfn, unsigned long nr_pages,
> void __remove_pages(unsigned long pfn, unsigned long nr_pages,
> struct vmem_altmap *altmap)
> {
> + const unsigned long end_pfn = pfn + nr_pages;
> + unsigned long cur_nr_pages;
> unsigned long map_offset = 0;
> - unsigned long nr, start_sec, end_sec;
>
> map_offset = vmem_altmap_offset(altmap);
>
> if (check_pfn_span(pfn, nr_pages, "remove"))
> return;
>
> - start_sec = pfn_to_section_nr(pfn);
> - end_sec = pfn_to_section_nr(pfn + nr_pages - 1);
> - for (nr = start_sec; nr <= end_sec; nr++) {
> - unsigned long pfns;
> -
> + for (; pfn < end_pfn; pfn += cur_nr_pages) {
> cond_resched();
> - pfns = min(nr_pages, PAGES_PER_SECTION
> - - (pfn & ~PAGE_SECTION_MASK));
> - __remove_section(pfn, pfns, map_offset, altmap);
> - pfn += pfns;
> - nr_pages -= pfns;
> + /* Select all remaining pages up to the next section boundary */
> + cur_nr_pages = min(end_pfn - pfn, -(pfn | PAGE_SECTION_MASK));
> + __remove_section(pfn, cur_nr_pages, map_offset, altmap);
> map_offset = 0;
> }
> }
> --
> 2.21.0
>
>

--
Oscar Salvador
SUSE L3