[patch 062/134] mm/memory_hotplug: drop PageReserved() check in online_pages_range()

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From: David Hildenbrand <david@xxxxxxxxxx>
Subject: mm/memory_hotplug: drop PageReserved() check in online_pages_range()

move_pfn_range_to_zone() will set all pages to PG_reserved via
memmap_init_zone().  The only way a page could no longer be reserved would
be if a MEM_GOING_ONLINE notifier would clear PG_reserved - which is not
done (the online_page callback is used for that purpose by e.g., Hyper-V
instead).  walk_system_ram_range() will never call online_pages_range()
with duplicate PFNs, so drop the PageReserved() check.

This seems to be a leftover from ancient times where the memmap was
initialized when adding memory and we wanted to check for already onlined
memory.

Link: http://lkml.kernel.org/r/20190814154109.3448-3-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Arun KS <arunks@xxxxxxxxxxxxxx>
Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Nadav Amit <namit@xxxxxxxxxx>
Cc: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/memory_hotplug.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

--- a/mm/memory_hotplug.c~mm-memory_hotplug-drop-pagereserved-check-in-online_pages_range
+++ a/mm/memory_hotplug.c
@@ -653,9 +653,7 @@ static int online_pages_range(unsigned l
 {
 	unsigned long onlined_pages = *(unsigned long *)arg;
 
-	if (PageReserved(pfn_to_page(start_pfn)))
-		onlined_pages += online_pages_blocks(start_pfn, nr_pages);
-
+	onlined_pages += online_pages_blocks(start_pfn, nr_pages);
 	online_mem_sections(start_pfn, start_pfn + nr_pages);
 
 	*(unsigned long *)arg = onlined_pages;
_



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