linux-kernel - [PATCH] mm, memory_hotplug: Fix the wrong usage of N_HIGH

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Date:   Wed, 20 Mar 2019 16:07:32 +0800
From:   Baoquan He <bhe@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     akpm@...ux-foundation.org, osalvador@...e.de, mhocko@...e.com,
        david@...hat.com, richard.weiyang@...il.com, rppt@...ux.ibm.com,
        Baoquan He <bhe@...hat.com>
Subject: [PATCH] mm, memory_hotplug: Fix the wrong usage of N_HIGH_MEMORY

In function node_states_check_changes_online(), N_HIGH_MEMORY is used
to substitute ZONE_HIGHMEM directly. This is not right. N_HIGH_MEMORY
always has value '3' if CONFIG_HIGHMEM=y, while ZONE_HIGHMEM's value
is not. It depends on whether CONFIG_ZONE_DMA/CONFIG_ZONE_DMA32 are
enabled. Obviously it's not true for CONFIG_ZONE_DMA32 on 32bit system,
and CONFIG_ZONE_DMA is also optional.

Replace it with ZONE_HIGHMEM.

Fixes: 8efe33f40f3e ("mm/memory_hotplug.c: simplify node_states_check_changes_online")
Signed-off-by: Baoquan He <bhe@...hat.com>
---
 mm/memory_hotplug.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 6b05576fb4ec..09911d34a3be 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -712,7 +712,7 @@ static void node_states_check_changes_online(unsigned long nr_pages,
 	if (zone_idx(zone) <= ZONE_NORMAL && !node_state(nid, N_NORMAL_MEMORY))
 		arg->status_change_nid_normal = nid;
 #ifdef CONFIG_HIGHMEM
-	if (zone_idx(zone) <= N_HIGH_MEMORY && !node_state(nid, N_HIGH_MEMORY))
+	if (zone_idx(zone) <= ZONE_HIGHMEM && !node_state(nid, N_HIGH_MEMORY))
 		arg->status_change_nid_high = nid;
 #endif
 }
-- 
2.17.2