Re: [PATCH v2 01/14] memory-failure: fetch compound_head after pgmap_pfn_valid()

["HORIGUCHI NAOYA(堀口 直也)" <naoya.horiguchi@nec.com>]

On Thu, Jun 17, 2021 at 07:44:54PM +0100, Joao Martins wrote:
> memory_failure_dev_pagemap() at the moment assumes base pages (e.g.
> dax_lock_page()).  For pagemap with compound pages fetch the
> compound_head in case a tail page memory failure is being handled.
> 
> Currently this is a nop, but in the advent of compound pages in
> dev_pagemap it allows memory_failure_dev_pagemap() to keep working.
> 
> Reported-by: Jane Chu <jane.chu@oracle.com>
> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>

Looks good to me.

Reviewed-by: Naoya Horiguchi <naoya.horiguchi@nec.com>

> ---
>  mm/memory-failure.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index e684b3d5c6a6..f1be578e488f 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1519,6 +1519,12 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
>  		goto out;
>  	}
>  
> +	/*
> +	 * Pages instantiated by device-dax (not filesystem-dax)
> +	 * may be compound pages.
> +	 */
> +	page = compound_head(page);
> +
>  	/*
>  	 * Prevent the inode from being freed while we are interrogating
>  	 * the address_space, typically this would be handled by
> -- 
> 2.17.1
>