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Subject: Re: [PATCH v3 6/6] mm/memory_hotplug: fix unpaired
 mem_hotplug_begin/done
To:     Jia He <justin.he@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>, Tony Luck <tony.luck@intel.com>,
        Fenghua Yu <fenghua.yu@intel.com>,
        Yoshinori Sato <ysato@users.sourceforge.jp>,
        Rich Felker <dalias@libc.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Vishal Verma <vishal.l.verma@intel.com>,
        Dave Jiang <dave.jiang@intel.com>, Baoquan He <bhe@redhat.com>,
        Chuhong Yuan <hslester96@gmail.com>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Logan Gunthorpe <logang@deltatee.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Michal Hocko <mhocko@suse.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org,
        linux-nvdimm@lists.01.org, linux-mm@kvack.org,
        Jonathan Cameron <Jonathan.Cameron@Huawei.com>,
        Kaly Xin <Kaly.Xin@arm.com>, stable@vger.kernel.org
References: <20200709020629.91671-1-justin.he@arm.com>
 <20200709020629.91671-7-justin.he@arm.com>
From:   David Hildenbrand <david@redhat.com>
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Message-ID: <2dfaf00b-9b08-8b90-6056-b53f7aa9b51c@redhat.com>
Date:   Thu, 9 Jul 2020 11:11:57 +0200
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On 09.07.20 04:06, 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]
> 
> Fixes: f1037ec0cc8a ("mm/memory_hotplug: fix remove_memory() lockdep splat")
> Cc: stable@vger.kernel.org # v5.6+
> Signed-off-by: Jia He <justin.he@arm.com>
> Reviewed-by: David Hildenbrand <david@redhat.com>
> Acked-by: Michal Hocko <mhocko@suse.com>
> Acked-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  mm/memory_hotplug.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index b49ab743d914..3e0645387daf 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1752,7 +1752,7 @@ static int __ref try_remove_memory(int nid, u64 start, u64 size)
>  	 */
>  	rc = walk_memory_blocks(start, size, NULL, check_memblock_offlined_cb);
>  	if (rc)
> -		goto done;
> +		return rc;
>  
>  	/* remove memmap entry */
>  	firmware_map_remove(start, start + size, "System RAM");
> @@ -1776,9 +1776,8 @@ static int __ref try_remove_memory(int nid, u64 start, u64 size)
>  
>  	try_offline_node(nid);
>  
> -done:
>  	mem_hotplug_done();
> -	return rc;
> +	return 0;
>  }
>  
>  /**
> 

@Andrew, can you pick that up directly? It's independent of the other stuff.

-- 
Thanks,

David / dhildenb