On 02/05/20 at 02:20pm, David Hildenbrand wrote:

On 05.02.20 13:43, Baoquan He wrote:

quoted

On 02/04/20 at 03:42pm, David Hildenbrand wrote:

quoted

On 04.02.20 15:25, Baoquan He wrote:

quoted

On 10/06/19 at 10:56am, David Hildenbrand wrote:

quoted

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 <redacted>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Dan Williams <redacted>
Cc: Wei Yang <redacted>
Signed-off-by: David Hildenbrand <redacted>
---
 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.