linux-kernel - [PATCH v1 04/11] mm/memory_hotplug: simplify offlining of pages in offline

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Date:   Wed, 19 Aug 2020 12:11:50 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Wei Yang <richard.weiyang@...ux.alibaba.com>,
        Baoquan He <bhe@...hat.com>,
        Pankaj Gupta <pankaj.gupta.linux@...il.com>,
        Oscar Salvador <osalvador@...e.de>
Subject: [PATCH v1 04/11] mm/memory_hotplug: simplify offlining of pages in offline_pages()

We make sure that we cannot have any memory holes right at the beginning
of offline_pages(). We no longer need walk_system_ram_range() and can
call __offline_isolated_pages() directly.

offlined_pages always corresponds to nr_pages, so we can simplify that.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Wei Yang <richard.weiyang@...ux.alibaba.com>
Cc: Baoquan He <bhe@...hat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@...il.com>
Cc: Oscar Salvador <osalvador@...e.de>
Signed-off-by: David Hildenbrand <david@...hat.com>
---
 mm/memory_hotplug.c | 28 ++++++++--------------------
 1 file changed, 8 insertions(+), 20 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index f64478349148d..50aa5df696e9d 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1373,17 +1373,6 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 	return ret;
 }
 
-/* Mark all sections offline and remove all free pages from the buddy. */
-static int
-offline_isolated_pages_cb(unsigned long start, unsigned long nr_pages,
-			void *data)
-{
-	unsigned long *offlined_pages = (unsigned long *)data;
-
-	*offlined_pages += __offline_isolated_pages(start, start + nr_pages);
-	return 0;
-}
-
 static int __init cmdline_parse_movable_node(char *p)
 {
 	movable_node_enabled = true;
@@ -1470,7 +1459,7 @@ static int count_system_ram_pages_cb(unsigned long start_pfn,
 int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
 {
 	const unsigned long end_pfn = start_pfn + nr_pages;
-	unsigned long pfn, system_ram_pages = 0, offlined_pages = 0;
+	unsigned long pfn, system_ram_pages = 0;
 	int ret, node, nr_isolate_pageblock;
 	unsigned long flags;
 	struct zone *zone;
@@ -1570,11 +1559,10 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
 		}
 	} while (test_pages_isolated(start_pfn, end_pfn, MEMORY_OFFLINE));
 
-	/* Ok, all of our target is isolated.
-	   We cannot do rollback at this point. */
-	walk_system_ram_range(start_pfn, end_pfn - start_pfn,
-			      &offlined_pages, offline_isolated_pages_cb);
-	pr_info("Offlined Pages %ld\n", offlined_pages);
+	/* Mark all sections offline and remove free pages from the buddy. */
+	__offline_isolated_pages(start_pfn, end_pfn);
+	pr_info("Offlined Pages %ld\n", nr_pages);
+
 	/*
 	 * Onlining will reset pagetype flags and makes migrate type
 	 * MOVABLE, so just need to decrease the number of isolated
@@ -1585,11 +1573,11 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
 	spin_unlock_irqrestore(&zone->lock, flags);
 
 	/* removal success */
-	adjust_managed_page_count(pfn_to_page(start_pfn), -offlined_pages);
-	zone->present_pages -= offlined_pages;
+	adjust_managed_page_count(pfn_to_page(start_pfn), -nr_pages);
+	zone->present_pages -= nr_pages;
 
 	pgdat_resize_lock(zone->zone_pgdat, &flags);
-	zone->zone_pgdat->node_present_pages -= offlined_pages;
+	zone->zone_pgdat->node_present_pages -= nr_pages;
 	pgdat_resize_unlock(zone->zone_pgdat, &flags);
 
 	init_per_zone_wmark_min();
-- 
2.26.2