Re: [PATCH 1/6] mm/gup: perform check_dax_vmas only when FS_DAX is enabled

[John Hubbard]

On 12/1/20 9:23 PM, Pavel Tatashin wrote:
> There is no need to check_dax_vmas() and run through the npage loop of
> pinned pages if FS_DAX is not enabled.
>
> Add a stub check_dax_vmas() function for no-FS_DAX case.
>
> Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
> ---
>   mm/gup.c | 7 +++++++
>   1 file changed, 7 insertions(+)
>
> diff --git a/mm/gup.c b/mm/gup.c
> index 98eb8e6d2609..cdb8b9eeb016 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1568,6 +1568,7 @@ struct page *get_dump_page(unsigned long addr)
>   #endif /* CONFIG_ELF_CORE */
>   
>   #if defined(CONFIG_FS_DAX) || defined (CONFIG_CMA)
> +#ifdef CONFIG_FS_DAX
>   static bool check_dax_vmas(struct vm_area_struct **vmas, long nr_pages)
>   {
>   	long i;
> @@ -1586,6 +1587,12 @@ static bool check_dax_vmas(struct vm_area_struct **vmas, long nr_pages)
>   	}
>   	return false;
>   }
> +#else
> +static bool check_dax_vmas(struct vm_area_struct **vmas, long nr_pages)
> +{
> +	return false;
> +}
> +#endif
>   
>   #ifdef CONFIG_CMA
>   static long check_and_migrate_cma_pages(struct mm_struct *mm,

Looks obviously correct, and the follow-up simplication is very nice.

Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>

thanks,
--
John Hubbard
NVIDIA