On Sun, Jun 8, 2025 at 9:32 PM Byungchul Park <byungchul@xxxxxx> wrote:
>
> To simplify struct page, the effort to separate its own descriptor from
> struct page is required and the work for page pool is on going.
>
> To achieve that, all the code should avoid directly accessing page pool
> members of struct page.
>
> Access ->pp_magic through struct netmem_desc instead of directly
> accessing it through struct page in page_pool_page_is_pp(). Plus, move
> page_pool_page_is_pp() from mm.h to netmem.h to use struct netmem_desc
> without header dependency issue.
>
> Signed-off-by: Byungchul Park <byungchul@xxxxxx>
> Reviewed-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
> ---
> include/linux/mm.h | 12 ------------
> include/net/netmem.h | 14 ++++++++++++++
> mm/page_alloc.c | 1 +
> 3 files changed, 15 insertions(+), 12 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index e51dba8398f7..f23560853447 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -4311,16 +4311,4 @@ int arch_lock_shadow_stack_status(struct task_struct *t, unsigned long status);
> */
> #define PP_MAGIC_MASK ~(PP_DMA_INDEX_MASK | 0x3UL)
>
> -#ifdef CONFIG_PAGE_POOL
> -static inline bool page_pool_page_is_pp(struct page *page)
> -{
> - return (page->pp_magic & PP_MAGIC_MASK) == PP_SIGNATURE;
> -}
> -#else
> -static inline bool page_pool_page_is_pp(struct page *page)
> -{
> - return false;
> -}
> -#endif
> -
> #endif /* _LINUX_MM_H */
> diff --git a/include/net/netmem.h b/include/net/netmem.h
> index d84ab624b489..8f354ae7d5c3 100644
> --- a/include/net/netmem.h
> +++ b/include/net/netmem.h
> @@ -56,6 +56,20 @@ NETMEM_DESC_ASSERT_OFFSET(pp_ref_count, pp_ref_count);
> */
> static_assert(sizeof(struct netmem_desc) <= offsetof(struct page, _refcount));
>
> +#ifdef CONFIG_PAGE_POOL
> +static inline bool page_pool_page_is_pp(struct page *page)
> +{
> + struct netmem_desc *desc = (struct netmem_desc *)page;
> +
> + return (desc->pp_magic & PP_MAGIC_MASK) == PP_SIGNATURE;
> +}
> +#else
> +static inline bool page_pool_page_is_pp(struct page *page)
> +{
> + return false;
> +}
> +#endif
> +
> /* net_iov */
>
> DECLARE_STATIC_KEY_FALSE(page_pool_mem_providers);
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 4f29e393f6af..be0752c0ac92 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -55,6 +55,7 @@
> #include <linux/delayacct.h>
> #include <linux/cacheinfo.h>
> #include <linux/pgalloc_tag.h>
> +#include <net/netmem.h>
mm files starting to include netmem.h is a bit interesting. I did not
expect/want dependencies outside of net. If anything the netmem stuff
include linux/mm.h
But I don't have a butter suggestion here and I don't see any huge
problems with this off the top of my head, so
Reviewed-by: Mina Almasry <almasrymina@xxxxxxxxxx>
Lets see if Jakub objects though. To be fair, we did put the netmem
private stuff in net/core/netmem_priv.h, so technically
include/net/netmem.h should be exportable indeed.
--
Thanks,
Mina
