Re: [Xen-devel] [PATCH RFCv2 5/6] powerpc/powernv: hold device_hotplug_lock in memtrace_offline_pages()

[Pasha Tatashin <Pavel.Tatashin@xxxxxxxxxxxxx>]

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

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@xxxxxxxxxxxxxxxxxxx>
> Cc: Paul Mackerras <paulus@xxxxxxxxx>
> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> Cc: Rashmica Gupta <rashmica.g@xxxxxxxxx>
> Cc: Balbir Singh <bsingharora@xxxxxxxxx>
> Cc: Michael Neuling <mikey@xxxxxxxxxxx>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
> ---
>  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;
>  }
>  
> 
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