linux-kernel - [PATCH memcg] mm/page_alloc.c: avoid statistic update with 0

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Date:   Fri, 8 Oct 2021 12:24:21 +0300
From:   Vasily Averin <vvs@...tuozzo.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kernel@...nvz.org,
        Mel Gorman <mgorman@...hsingularity.net>,
        Uladzislau Rezki <urezki@...il.com>,
        Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH memcg] mm/page_alloc.c: avoid statistic update with 0

__alloc_pages_bulk can call __count_zid_vm_events and zone_statistics
with nr_account = 0.

Fixes: 3e23060b2d0b ("mm/page_alloc: batch the accounting updates in the bulk allocator")
Signed-off-by: Vasily Averin <vvs@...tuozzo.com>
---
 mm/page_alloc.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 602819a232e5..e67113452ee8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5364,9 +5364,10 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
 	}
 
 	local_unlock_irqrestore(&pagesets.lock, flags);
-
-	__count_zid_vm_events(PGALLOC, zone_idx(zone), nr_account);
-	zone_statistics(ac.preferred_zoneref->zone, zone, nr_account);
+	if (nr_account) {
+		__count_zid_vm_events(PGALLOC, zone_idx(zone), nr_account);
+		zone_statistics(ac.preferred_zoneref->zone, zone, nr_account);
+	}
 	if (objcg)
 		memcg_bulk_post_charge_hook(objcg, nr_pre_charge - nr_account);
 
-- 
2.31.1