On 05/04/2018 08:33 PM, Matthew Wilcox wrote:
> From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
>
> Make hmm_data an explicit member of the struct page union.
>
> Signed-off-by: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
> ---
> include/linux/hmm.h | 8 ++------
> include/linux/mm_types.h | 14 +++++++++-----
> 2 files changed, 11 insertions(+), 11 deletions(-)
>
> diff --git a/include/linux/hmm.h b/include/linux/hmm.h
> index 39988924de3a..91c1b2dccbbb 100644
> --- a/include/linux/hmm.h
> +++ b/include/linux/hmm.h
> @@ -522,9 +522,7 @@ void hmm_devmem_remove(struct hmm_devmem *devmem);
> static inline void hmm_devmem_page_set_drvdata(struct page *page,
> unsigned long data)
> {
> - unsigned long *drvdata = (unsigned long *)&page->pgmap;
> -
> - drvdata[1] = data;
Well, that was ugly :)
> + page->hmm_data = data;
> }
>
> /*
> @@ -535,9 +533,7 @@ static inline void hmm_devmem_page_set_drvdata(struct page *page,
> */
> static inline unsigned long hmm_devmem_page_get_drvdata(const struct page *page)
> {
> - const unsigned long *drvdata = (const unsigned long *)&page->pgmap;
> -
> - return drvdata[1];
> + return page->hmm_data;
> }
>
>
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 5a519279dcd5..fa05e6ca31ed 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -150,11 +150,15 @@ struct page {
> /** @rcu_head: You can use this to free a page by RCU. */
> struct rcu_head rcu_head;
>
> - /**
> - * @pgmap: For ZONE_DEVICE pages, this points to the hosting
> - * device page map.
> - */
> - struct dev_pagemap *pgmap;
> + struct {
> + /**
> + * @pgmap: For ZONE_DEVICE pages, this points to the
> + * hosting device page map.
> + */
> + struct dev_pagemap *pgmap;
> + unsigned long hmm_data;
> + unsigned long _zd_pad_1; /* uses mapping */
> + };
Maybe move this above rcu_head and make the comments look more like for
the other union variants?
> };
>
> union { /* This union is 4 bytes in size. */
>
