linux-kernel - [PATCH] mm: initialize hotplugged pages as reserved

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Message-ID: <20150803081922.GG5840@techsingularity.net>
Date:	Mon, 3 Aug 2015 09:19:22 +0100
From:	Mel Gorman <mgorman@...hsingularity.net>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	David Vrabel <david.vrabel@...rix.com>,
	Alex Ng <alexng@...rosoft.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: [PATCH] mm: initialize hotplugged pages as reserved

Commit 92923ca3aace (mm: meminit: only set page reserved in the memblock
region) broke memory hotplug which expects the memmap for newly added
sections to be reserved until onlined by online_pages_range(). This patch
marks hotplugged pages as reserved when adding new zones.

Signed-off-by: Mel Gorman <mgorman@...e.de>
Reported-and-tested-by: David Vrabel <david.vrabel@...rix.com>
---
 mm/memory_hotplug.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 460d0fe..169770a 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -446,7 +446,7 @@ static int __meminit __add_zone(struct zone *zone, unsigned long phys_start_pfn)
 	int nr_pages = PAGES_PER_SECTION;
 	int nid = pgdat->node_id;
 	int zone_type;
-	unsigned long flags;
+	unsigned long flags, pfn;
 	int ret;
 
 	zone_type = zone - pgdat->node_zones;
@@ -461,6 +461,14 @@ static int __meminit __add_zone(struct zone *zone, unsigned long phys_start_pfn)
 	pgdat_resize_unlock(zone->zone_pgdat, &flags);
 	memmap_init_zone(nr_pages, nid, zone_type,
 			 phys_start_pfn, MEMMAP_HOTPLUG);
+
+	/* online_page_range is called later and expects pages reserved */
+	for (pfn = phys_start_pfn; pfn < phys_start_pfn + nr_pages; pfn++) {
+		if (!pfn_valid(pfn))
+			continue;
+
+		SetPageReserved(pfn_to_page(pfn));
+	}
 	return 0;
 }
 
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