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From:   Doug Berger <opendmb@gmail.com>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Jonathan Corbet <corbet@lwn.net>, Mike Rapoport <rppt@kernel.org>,
        Borislav Petkov <bp@suse.de>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Neeraj Upadhyay <quic_neeraju@quicinc.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Damien Le Moal <damien.lemoal@opensource.wdc.com>,
        Muchun Song <songmuchun@bytedance.com>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        Mel Gorman <mgorman@suse.de>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        David Hildenbrand <david@redhat.com>,
        Oscar Salvador <osalvador@suse.de>,
        Michal Hocko <mhocko@suse.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, Doug Berger <opendmb@gmail.com>
Subject: [PATCH v2 2/9] mm/vmstat: show start_pfn when zone spans pages
Date:   Wed, 28 Sep 2022 15:32:54 -0700
Message-Id: <20220928223301.375229-3-opendmb@gmail.com>
In-Reply-To: <20220928223301.375229-1-opendmb@gmail.com>
References: <20220928223301.375229-1-opendmb@gmail.com>
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A zone that overlaps with another zone may span a range of pages
that are not present. In this case, displaying the start_pfn of
the zone allows the zone page range to be identified.

Signed-off-by: Doug Berger <opendmb@gmail.com>
---
 mm/vmstat.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 90af9a8572f5..e2f19f2b7615 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1717,6 +1717,11 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
 
 	/* If unpopulated, no other information is useful */
 	if (!populated_zone(zone)) {
+		/* Show start_pfn for empty overlapped zones */
+		if (zone->spanned_pages)
+			seq_printf(m,
+				   "\n  start_pfn:           %lu",
+				   zone->zone_start_pfn);
 		seq_putc(m, '\n');
 		return;
 	}
-- 
2.25.1