Re: [PATCH 04/22] mm: don't clear ->mapping in hmm_devmem_free

[Michal Hocko]

On Thu 13-06-19 11:43:07, Christoph Hellwig wrote:
> ->mapping isn't even used by HMM users, and the field at the same offset
> in the zone_device part of the union is declared as pad.  (Which btw is
> rather confusing, as DAX uses ->pgmap and ->mapping from two different
> sides of the union, but DAX doesn't use hmm_devmem_free).
> 
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>

I cannot really judge here but setting mapping here without any comment
is quite confusing. So if this is safe to remove then it is certainly an
improvement.

> ---
>  mm/hmm.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/mm/hmm.c b/mm/hmm.c
> index 0c62426d1257..e1dc98407e7b 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -1347,8 +1347,6 @@ static void hmm_devmem_free(struct page *page, void *data)
>  {
>  	struct hmm_devmem *devmem = data;
>  
> -	page->mapping = NULL;
> -
>  	devmem->ops->free(devmem, page);
>  }
>  
> -- 
> 2.20.1

-- 
Michal Hocko
SUSE Labs