linux-kernel - [PATCH v2 5/5] mm/memory_hotplug: online_pages cannot be 0 in online

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Message-Id: <20190814154109.3448-6-david@redhat.com>
Date:   Wed, 14 Aug 2019 17:41:09 +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>,
        Oscar Salvador <osalvador@...e.de>,
        Michal Hocko <mhocko@...e.com>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Dan Williams <dan.j.williams@...el.com>
Subject: [PATCH v2 5/5] mm/memory_hotplug: online_pages cannot be 0 in online_pages()

walk_system_ram_range() will fail with -EINVAL in case
online_pages_range() was never called (== no resource applicable in the
range). Otherwise, we will always call online_pages_range() with
nr_pages > 0 and, therefore, have online_pages > 0.

Remove that special handling.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Oscar Salvador <osalvador@...e.de>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Pavel Tatashin <pasha.tatashin@...een.com>
Cc: Dan Williams <dan.j.williams@...el.com>
Acked-by: Michal Hocko <mhocko@...e.com>
Signed-off-by: David Hildenbrand <david@...hat.com>
---
 mm/memory_hotplug.c | 22 +++++++++-------------
 1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index f245fb50ba7f..01456fc66564 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -853,6 +853,7 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
 	ret = walk_system_ram_range(pfn, nr_pages, &onlined_pages,
 		online_pages_range);
 	if (ret) {
+		/* not a single memory resource was applicable */
 		if (need_zonelists_rebuild)
 			zone_pcp_reset(zone);
 		goto failed_addition;
@@ -866,27 +867,22 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
 
 	shuffle_zone(zone);
 
-	if (onlined_pages) {
-		node_states_set_node(nid, &arg);
-		if (need_zonelists_rebuild)
-			build_all_zonelists(NULL);
-		else
-			zone_pcp_update(zone);
-	}
+	node_states_set_node(nid, &arg);
+	if (need_zonelists_rebuild)
+		build_all_zonelists(NULL);
+	else
+		zone_pcp_update(zone);
 
 	init_per_zone_wmark_min();
 
-	if (onlined_pages) {
-		kswapd_run(nid);
-		kcompactd_run(nid);
-	}
+	kswapd_run(nid);
+	kcompactd_run(nid);
 
 	vm_total_pages = nr_free_pagecache_pages();
 
 	writeback_set_ratelimit();
 
-	if (onlined_pages)
-		memory_notify(MEM_ONLINE, &arg);
+	memory_notify(MEM_ONLINE, &arg);
 	mem_hotplug_done();
 	return 0;
 
-- 
2.21.0