Re: [PATCH 3/3] mm: Remove page->order

[Vlastimil Babka <vbabka@suse.cz>]

On 9/10/25 16:29, Matthew Wilcox (Oracle) wrote:
> We already use page->private for storing the order of a page while it's
> in the buddy allocator system; extend that to also storing the order
> while it's in the pcp_llist.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Cc: Alexei Starovoitov <ast@kernel.org>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

Nit below:

> ---
>  include/linux/mm_types.h | 8 +++-----
>  mm/page_alloc.c          | 4 ++--
>  2 files changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 4a441f78340d..569265d159a5 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -97,10 +97,7 @@ struct page {
>  				/* Or, free page */
>  				struct list_head buddy_list;
>  				struct list_head pcp_list;
> -				struct {
> -					struct llist_node pcp_llist;
> -					unsigned int order;
> -				};
> +				struct llist_node pcp_llist;
>  			};
>  			struct address_space *mapping;
>  			union {
> @@ -111,7 +108,8 @@ struct page {
>  			 * @private: Mapping-private opaque data.
>  			 * Usually used for buffer_heads if PagePrivate.
>  			 * Used for swp_entry_t if swapcache flag set.
> -			 * Indicates order in the buddy system if PageBuddy.
> +			 * Indicates order in the buddy system if PageBuddy
> +			 * or on pcp_llist.

In fact pcp_list too, so "or on pcp_list or pcp_llist" ?

>  			 */
>  			unsigned long private;
>  		};
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index d21a411e807e..e71e23d1a747 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1520,7 +1520,7 @@ static void add_page_to_zone_llist(struct zone *zone, struct page *page,
>  				   unsigned int order)
>  {
>  	/* Remember the order */
> -	page->order = order;
> +	page->private = order;
>  	/* Add the page to the free list */
>  	llist_add(&page->pcp_llist, &zone->trylock_free_pages);
>  }
> @@ -1549,7 +1549,7 @@ static void free_one_page(struct zone *zone, struct page *page,
>  
>  		llnode = llist_del_all(llhead);
>  		llist_for_each_entry_safe(p, tmp, llnode, pcp_llist) {
> -			unsigned int p_order = p->order;
> +			unsigned int p_order = p->private;
>  
>  			split_large_buddy(zone, p, page_to_pfn(p), p_order, fpi_flags);
>  			__count_vm_events(PGFREE, 1 << p_order);