linux-kernel - [PATCH] mm/page_alloc: fix counting of managed

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Date:   Thu, 27 May 2021 20:57:07 +0800
From:   Liu Shixin <liushixin2@...wei.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        yangerkun <yangerkun@...wei.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        Liu Shixin <liushixin2@...wei.com>
Subject: [PATCH] mm/page_alloc: fix counting of managed_pages

The commit f63661566fad (mm/page_alloc.c: clear out zone->lowmem_reserve[]
if the zone is empty) clear out zone->lowmem_reserve[] if zone is empty.
But when zone is not empty and sysctl_lowmem_reserve_ratio[i] is set to zero,
zone_managed_pages(zone) is not counted in the managed_pages either. This is
inconsistent with the description of lowmen_reserve, so fix it.

Fixes: f63661566fad ("mm/page_alloc.c: clear out zone->lowmem_reserve[] if the zone is empty")
Reported-by: yangerkun <yangerkun@...wei.com>
Signed-off-by: Liu Shixin <liushixin2@...wei.com>
---
 mm/page_alloc.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index aaa1655cf682..49a2efce5a84 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8061,14 +8061,14 @@ static void setup_per_zone_lowmem_reserve(void)
 			unsigned long managed_pages = 0;
 
 			for (j = i + 1; j < MAX_NR_ZONES; j++) {
-				if (clear) {
-					zone->lowmem_reserve[j] = 0;
-				} else {
-					struct zone *upper_zone = &pgdat->node_zones[j];
+				struct zone *upper_zone = &pgdat->node_zones[j];
+
+				managed_pages += zone_managed_pages(upper_zone);
 
-					managed_pages += zone_managed_pages(upper_zone);
+				if (clear)
+					zone->lowmem_reserve[j] = 0;
+				else
 					zone->lowmem_reserve[j] = managed_pages / ratio;
-				}
 			}
 		}
 	}
-- 
2.18.0.huawei.25