linux-kernel - [PATCH v2] mm/memory_hotplug: Drop memory device reference after find_memory

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Message-Id: <20190411110955.1430-1-david@redhat.com>
Date:   Thu, 11 Apr 2019 13:09:55 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.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>,
        Wei Yang <richard.weiyang@...il.com>, Qian Cai <cai@....pw>,
        Arun KS <arunks@...eaurora.org>,
        Mathieu Malaterre <malat@...ian.org>
Subject: [PATCH v2] mm/memory_hotplug: Drop memory device reference after find_memory_block()

Right now we are using find_memory_block() to get the node id for the
pfn range to online. We are missing to drop a reference to the memory
block device. While the device still gets unregistered via
device_unregister(), resulting in no user visible problem, the device is
never released via device_release(), resulting in a memory leak. Fix
that by properly using a put_device().

Fixes: d0dc12e86b31 ("mm/memory_hotplug: optimize memory hotplug")
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Oscar Salvador <osalvador@...e.de>
Cc: Michal Hocko <mhocko@...e.com>
Cc: David Hildenbrand <david@...hat.com>
Cc: Pavel Tatashin <pasha.tatashin@...een.com>
Cc: Wei Yang <richard.weiyang@...il.com>
Cc: Qian Cai <cai@....pw>
Cc: Arun KS <arunks@...eaurora.org>
Cc: Mathieu Malaterre <malat@...ian.org>
Reviewed-by: Oscar Salvador <osalvador@...e.de>
Reviewed-by: Wei Yang <richard.weiyang@...il.com>
Acked-by: Michal Hocko <mhocko@...e.com>
Signed-off-by: David Hildenbrand <david@...hat.com>
---
 mm/memory_hotplug.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 5eb4a4c7c21b..328878b6799d 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -854,6 +854,7 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
 	 */
 	mem = find_memory_block(__pfn_to_section(pfn));
 	nid = mem->nid;
+	put_device(&mem->dev);
 
 	/* associate pfn range with the zone */
 	zone = move_pfn_range(online_type, nid, pfn, nr_pages);
-- 
2.20.1