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From:   Wei Yang <richard.weiyang@gmail.com>
To:     akpm@linux-foundation.org, mgorman@techsingularity.net,
        mhocko@suse.com
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Wei Yang <richard.weiyang@gmail.com>
Subject: [PATCH] mm/memory_hotplug: build zonelist for managed_zone
Date:   Thu, 27 Jan 2022 01:20:23 +0000
Message-Id: <20220127012023.18095-1-richard.weiyang@gmail.com>
Precedence: bulk

During memory hotplug, when online/offline a zone, we need to rebuild
the zonelist for all node. There are two checks to decide whether a zone
would be added to zonelist:

  * one in online_pages/offline_pages to decide necessity
  * one in build_zonerefs_node to do real add

Currently we use different criteria at these two places, which is
different from the original behavior.

Originally during memory hotplug, zonelist is re-built when zone hasn't
been populated. This in introduced in 'commit 6811378e7d8b ("[PATCH]
wait_table and zonelist initializing for memory hotadd: update zonelists")'.
And at that moment, build_zonelists_node() also use populated_zone() to
decide whether the zone should be added to zonelist.

While in 'commit 6aa303defb74 ("mm, vmscan: only allocate and reclaim
from zones with pages managed by the buddy allocator")',
build_zonelists_node() changed to use managed_zone() to add zonelist.
But we still use populated_zone() to decide the necessity.

This patch restore the original behavior by using the same criteria to
add a zone in zonelist during memory hotplug.

Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Fixes: 6aa303defb74 ("mm, vmscan: only allocate and reclaim from zones with pages managed by the buddy allocator")
CC: Mel Gorman <mgorman@techsingularity.net>
---
 mm/memory_hotplug.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 2a9627dc784c..8f1906b33937 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1102,11 +1102,11 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages,
 	spin_unlock_irqrestore(&zone->lock, flags);
 
 	/*
-	 * If this zone is not populated, then it is not in zonelist.
+	 * If this zone is not managed, then it is not in zonelist.
 	 * This means the page allocator ignores this zone.
 	 * So, zonelist must be updated after online.
 	 */
-	if (!populated_zone(zone)) {
+	if (!managed_zone(zone)) {
 		need_zonelists_rebuild = 1;
 		setup_zone_pageset(zone);
 	}
@@ -1985,7 +1985,7 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages,
 	/* reinitialise watermarks and update pcp limits */
 	init_per_zone_wmark_min();
 
-	if (!populated_zone(zone)) {
+	if (!managed_zone(zone)) {
 		zone_pcp_reset(zone);
 		build_all_zonelists(NULL);
 	}
-- 
2.33.1