On 06.02.20 06:39, Baoquan He wrote:
> In commit 950b68d9178b ("mm/memory_hotplug: don't check for "all holes"
> in shrink_zone_span()"), the zone->zone_start_pfn/->spanned_pages
> resetting is moved into the if()/else if() branches, if the zone becomes
> empty. However the 2nd resetting code block may cause misunderstanding.
>
> So take the resetting codes out of the conditional checking and handling
> branches just as the old code does, the find_smallest_section_pfn()and
> find_biggest_section_pfn() searching have done the the same thing as
> the old for loop did, the logic is kept the same as the old code. This
> can remove the possible confusion.
>
> Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
> ---
> mm/memory_hotplug.c | 14 ++++++--------
> 1 file changed, 6 insertions(+), 8 deletions(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 089b6c826a9e..475d0d68a32c 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -398,7 +398,7 @@ static unsigned long find_biggest_section_pfn(int nid, struct zone *zone,
> static void shrink_zone_span(struct zone *zone, unsigned long start_pfn,
> unsigned long end_pfn)
> {
> - unsigned long pfn;
> + unsigned long pfn = zone->zone_start_pfn;
> int nid = zone_to_nid(zone);
>
> zone_span_writelock(zone);
> @@ -414,9 +414,6 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn,
> if (pfn) {
> zone->spanned_pages = zone_end_pfn(zone) - pfn;
> zone->zone_start_pfn = pfn;
> - } else {
> - zone->zone_start_pfn = 0;
> - zone->spanned_pages = 0;
> }
> } else if (zone_end_pfn(zone) == end_pfn) {
> /*
> @@ -429,10 +426,11 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn,
> start_pfn);
> if (pfn)
> zone->spanned_pages = pfn - zone->zone_start_pfn + 1;
> - else {
> - zone->zone_start_pfn = 0;
> - zone->spanned_pages = 0;
> - }
> + }
> +
> + if (!pfn) {
> + zone->zone_start_pfn = 0;
> + zone->spanned_pages = 0;
> }
> zone_span_writeunlock(zone);
> }
>
So, what if your zone starts at pfn 0? Unlikely that we can actually
offline that, but still it is more confusing than the old code IMHO.
Then I prefer to drop the second else case as discussed instead.
--
Thanks,
David / dhildenb
