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

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Date:   Thu, 11 Apr 2019 07:20:08 -0400 (EDT)
From:   Pankaj Gupta <pagupta@...hat.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        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: Re: [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

Good catch it is.

Acked-by: Pankaj Gupta <pagupta@...hat.com>

> 
>