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    SubjectRe: [PATCH v6 08/10] mm/memory_hotplug: Don't check for "all holes" in shrink_zone_span()
    On 02/05/20 at 02:20pm, David Hildenbrand wrote:
    > On 05.02.20 13:43, Baoquan He wrote:
    > > On 02/04/20 at 03:42pm, David Hildenbrand wrote:
    > >> On 04.02.20 15:25, Baoquan He wrote:
    > >>> On 10/06/19 at 10:56am, David Hildenbrand wrote:
    > >>>> If we have holes, the holes will automatically get detected and removed
    > >>>> once we remove the next bigger/smaller section. The extra checks can
    > >>>> go.
    > >>>>
    > >>>> Cc: Andrew Morton <akpm@linux-foundation.org>
    > >>>> Cc: Oscar Salvador <osalvador@suse.de>
    > >>>> Cc: Michal Hocko <mhocko@suse.com>
    > >>>> Cc: David Hildenbrand <david@redhat.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>
    > >>>> ---
    > >>>> mm/memory_hotplug.c | 34 +++++++---------------------------
    > >>>> 1 file changed, 7 insertions(+), 27 deletions(-)
    > >>>>
    > >>>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
    > >>>> index f294918f7211..8dafa1ba8d9f 100644
    > >>>> --- a/mm/memory_hotplug.c
    > >>>> +++ b/mm/memory_hotplug.c
    > >>>> @@ -393,6 +393,9 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn,
    > >>>> if (pfn) {
    > >>>> zone->zone_start_pfn = pfn;
    > >>>> zone->spanned_pages = zone_end_pfn - pfn;
    > >>>> + } else {
    > >>>> + zone->zone_start_pfn = 0;
    > >>>> + zone->spanned_pages = 0;
    > >>>> }
    > >>>> } else if (zone_end_pfn == end_pfn) {
    > >>>> /*
    > >>>> @@ -405,34 +408,11 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn,
    > >>>> start_pfn);
    > >>>> if (pfn)
    > >>>> zone->spanned_pages = pfn - zone_start_pfn + 1;
    > >>>> + else {
    > >>>> + zone->zone_start_pfn = 0;
    > >>>> + zone->spanned_pages = 0;
    > >>>
    > >>> Thinking in which case (zone_start_pfn != start_pfn) and it comes here.
    > >>
    > >> Could only happen in case the zone_start_pfn would have been "out of the
    > >> zone already". If you ask me: unlikely :)
    > >
    > > Yeah, I also think it's unlikely to come here.
    > >
    > > The 'if (zone_start_pfn == start_pfn)' checking also covers the case
    > > (zone_start_pfn == start_pfn && zone_end_pfn == end_pfn). So this
    > > zone_start_pfn/spanned_pages resetting can be removed to avoid
    > > confusion.
    >
    > At least I would find it more confusing without it (or want a comment
    > explaining why this does not have to be handled and why the !pfn case is
    > not possible).

    I don't get why being w/o it will be more confusing, but it's OK since
    it doesn't impact anything.

    >
    > Anyhow, that patch is already upstream and I don't consider this high
    > priority. Thanks :)

    Yeah, noticed you told Wei the status in another patch thread, I am fine
    with it, just leave it to you to decide. Thanks.

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