linux-kernel - [PATCH v2 2/5] mm/memory_hotplug: Drop PageReserved() check in online_pages

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Date:   Wed, 14 Aug 2019 17:41:06 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Oscar Salvador <osalvador@...e.de>,
        Michal Hocko <mhocko@...e.com>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Dan Williams <dan.j.williams@...el.com>
Subject: [PATCH v2 2/5] 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.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Oscar Salvador <osalvador@...e.de>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Pavel Tatashin <pasha.tatashin@...een.com>
Cc: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: David Hildenbrand <david@...hat.com>
---
 mm/memory_hotplug.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 3706a137d880..10ad970f3f14 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -653,9 +653,7 @@ static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages,
 {
 	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;
-- 
2.21.0