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Date:   Mon, 6 Jul 2020 09:49:24 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Jia He <justin.he@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Baoquan He <bhe@...hat.com>,
        Chuhong Yuan <hslester96@...il.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Kaly Xin <Kaly.Xin@....com>,
        Dan Williams <dan.j.williams@...el.com>,
        Michal Hocko <mhocko@...nel.org>
Subject: Re: [PATCH 3/3] mm/memory_hotplug: fix unpaired
 mem_hotplug_begin/done

On 06.07.20 03:19, Jia He wrote:
> When check_memblock_offlined_cb() returns failed rc(e.g. the memblock is
> online at that time), mem_hotplug_begin/done is unpaired in such case.
> 
> Therefore a warning:
>  Call Trace:
>   percpu_up_write+0x33/0x40
>   try_remove_memory+0x66/0x120
>   ? _cond_resched+0x19/0x30
>   remove_memory+0x2b/0x40
>   dev_dax_kmem_remove+0x36/0x72 [kmem]
>   device_release_driver_internal+0xf0/0x1c0
>   device_release_driver+0x12/0x20
>   bus_remove_device+0xe1/0x150
>   device_del+0x17b/0x3e0
>   unregister_dev_dax+0x29/0x60
>   devm_action_release+0x15/0x20
>   release_nodes+0x19a/0x1e0
>   devres_release_all+0x3f/0x50
>   device_release_driver_internal+0x100/0x1c0
>   driver_detach+0x4c/0x8f
>   bus_remove_driver+0x5c/0xd0
>   driver_unregister+0x31/0x50
>   dax_pmem_exit+0x10/0xfe0 [dax_pmem]
> 
> This fixes it by moving mem_hotplug_done ahead of "done"
> 
> Signed-off-by: Jia He <justin.he@....com>
> ---
>  mm/memory_hotplug.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index e1e290577b45..86b36714342b 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1769,8 +1769,8 @@ static int __ref try_remove_memory(int nid, u64 start, u64 size)
>  
>  	try_offline_node(nid);
>  
> -done:
>  	mem_hotplug_done();
> +done:
>  	return rc;
>  }
>  
> 

Just drop the "done" label, use "return rc;" directly instead of the
goto, and "return 0;" at the end.

Also, please add

Fixes: f1037ec0cc8a ("mm/memory_hotplug: fix remove_memory() lockdep splat")

and

Cc: stable@...r.kernel.org # v5.6+

Thanks!

-- 
Thanks,

David / dhildenb

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