linux-kernel - [RFC PATCH 2/5] mm/memory_hotplug: Avoid node_set/clear_state(N_HIGH_MEMORY) when !CONFIG

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Date:   Wed, 22 Aug 2018 11:32:23 +0200
From:   Oscar Salvador <osalvador@...hadventures.net>
To:     akpm@...ux-foundation.org
Cc:     mhocko@...e.com, dan.j.williams@...el.com, malat@...ian.org,
        david@...hat.com, Pavel.Tatashin@...rosoft.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Oscar Salvador <osalvador@...e.de>
Subject: [RFC PATCH 2/5] mm/memory_hotplug: Avoid node_set/clear_state(N_HIGH_MEMORY) when !CONFIG_HIGHMEM

From: Oscar Salvador <osalvador@...e.de>

Currently, when !CONFIG_HIGHMEM, status_change_nid_high is being set
to status_change_nid_normal, but on such systems, N_HIGH_MEMORY equals
N_NORMAL_MEMORY.
That means that if status_change_nid_normal is not -1,
we will perform two calls to node_set_state for the same memory type.

Set status_change_nid_high to -1 for !CONFIG_HIGHMEM, so we skip the
double call in node_states_set_node.

The same goes for node_clear_state.

Signed-off-by: Oscar Salvador <osalvador@...e.de>
---
 mm/memory_hotplug.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 4a89915e1467..1cfd0b5a9cc7 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -724,7 +724,11 @@ static void node_states_check_changes_online(unsigned long nr_pages,
 	else
 		arg->status_change_nid_high = -1;
 #else
-	arg->status_change_nid_high = arg->status_change_nid_normal;
+	/*
+	 * When !CONFIG_HIGHMEM, N_HIGH_MEMORY equals N_NORMAL_MEMORY
+	 * so setting the node for N_NORMAL_MEMORY is enough.
+	 */
+	arg->status_change_nid_high = -1;
 #endif
 
 	/*
@@ -1547,7 +1551,11 @@ static void node_states_check_changes_offline(unsigned long nr_pages,
 	else
 		arg->status_change_nid_high = -1;
 #else
-	arg->status_change_nid_high = arg->status_change_nid_normal;
+	/*
+	 * When !CONFIG_HIGHMEM, N_HIGH_MEMORY equals N_NORMAL_MEMORY
+	 * so clearing the node for N_NORMAL_MEMORY is enough.
+	 */
+	arg->status_change_nid_high = -1;
 #endif
 
 	/*
-- 
2.13.6