releases/5.10.50/mm-page_alloc-fix-counting-of-managed_pages.patch

From b8fef203560c9d010799ff6499d09e9fdff7a203 Mon Sep 17 00:00:00 2001
From: Sasha Levin <sashal@kernel.org>
Date: Mon, 28 Jun 2021 19:42:33 -0700
Subject: mm/page_alloc: fix counting of managed_pages

From: Liu Shixin <liushixin2@huawei.com>

[ Upstream commit f7ec104458e00d27a190348ac3a513f3df3699a4 ]

commit f63661566fad ("mm/page_alloc.c: clear out zone->lowmem_reserve[] if
the zone is empty") clears 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 lowmem_reserve, so fix it.

Link: https://lkml.kernel.org/r/20210527125707.3760259-1-liushixin2@huawei.com
Fixes: f63661566fad ("mm/page_alloc.c: clear out zone->lowmem_reserve[] if the zone is empty")
Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Reported-by: yangerkun <yangerkun@huawei.com>
Reviewed-by: Baoquan He <bhe@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 f955610fb552..e30d88efd7fb 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7798,14 +7798,14 @@ 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;
-				}
 			}
 		}
 	}
-- 
2.30.2