linux-kernel - Re: [PATCH RFCv2 5/6] powerpc/powernv: hold device_hotplug_lock in memtrace_offline

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Message-ID: <226aaaf7-7d1c-6f7b-5bf4-e6eb99862ebd@microsoft.com>
Date:   Thu, 30 Aug 2018 19:38:26 +0000
From:   Pasha Tatashin <Pavel.Tatashin@...rosoft.com>
To:     David Hildenbrand <david@...hat.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Rashmica Gupta <rashmica.g@...il.com>,
        Balbir Singh <bsingharora@...il.com>,
        Michael Neuling <mikey@...ling.org>
Subject: Re: [PATCH RFCv2 5/6] powerpc/powernv: hold device_hotplug_lock in
 memtrace_offline_pages()

Reviewed-by: Pavel Tatashin <pavel.tatashin@...rosoft.com>

On 8/21/18 6:44 AM, David Hildenbrand wrote:
> Let's perform all checking + offlining + removing under
> device_hotplug_lock, so nobody can mess with these devices via
> sysfs concurrently.
> 
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Rashmica Gupta <rashmica.g@...il.com>
> Cc: Balbir Singh <bsingharora@...il.com>
> Cc: Michael Neuling <mikey@...ling.org>
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
>  arch/powerpc/platforms/powernv/memtrace.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/powernv/memtrace.c b/arch/powerpc/platforms/powernv/memtrace.c
> index ef7181d4fe68..473e59842ec5 100644
> --- a/arch/powerpc/platforms/powernv/memtrace.c
> +++ b/arch/powerpc/platforms/powernv/memtrace.c
> @@ -74,9 +74,13 @@ static bool memtrace_offline_pages(u32 nid, u64 start_pfn, u64 nr_pages)
>  {
>  	u64 end_pfn = start_pfn + nr_pages - 1;
>  
> +	lock_device_hotplug();
> +
>  	if (walk_memory_range(start_pfn, end_pfn, NULL,
> -	    check_memblock_online))
> +	    check_memblock_online)) {
> +		unlock_device_hotplug();
>  		return false;
> +	}
>  
>  	walk_memory_range(start_pfn, end_pfn, (void *)MEM_GOING_OFFLINE,
>  			  change_memblock_state);
> @@ -84,14 +88,16 @@ static bool memtrace_offline_pages(u32 nid, u64 start_pfn, u64 nr_pages)
>  	if (offline_pages(start_pfn, nr_pages)) {
>  		walk_memory_range(start_pfn, end_pfn, (void *)MEM_ONLINE,
>  				  change_memblock_state);
> +		unlock_device_hotplug();
>  		return false;
>  	}
>  
>  	walk_memory_range(start_pfn, end_pfn, (void *)MEM_OFFLINE,
>  			  change_memblock_state);
>  
> -	remove_memory(nid, start_pfn << PAGE_SHIFT, nr_pages << PAGE_SHIFT);
> +	__remove_memory(nid, start_pfn << PAGE_SHIFT, nr_pages << PAGE_SHIFT);
>  
> +	unlock_device_hotplug();
>  	return true;
>  }
>  
>