Re: [PATCH 2/2] mm/page_alloc: rename FPI_TRYLOCK -> FPI_NOLOCK

["Vlastimil Babka (SUSE)" <vbabka@kernel.org>]

On 7/10/26 12:42, Brendan Jackman wrote:
> As discussed in the linked patch, the there is some inconsistency between
> "trylock" and "nolock" nomenclature, let's align it. Since "nolock" is
> used in the public API it seems to have more mindshare so do that.
> 
> The linked patch did this for the ALLOC_ flag but forgot about FPI_.
> 
> Link: https://lore.kernel.org/all/20260703-alloc-trylock-v5-1-c87b714e19d3@google.com/
> Signed-off-by: Brendan Jackman <jackmanb@google.com>

Naming things is hard. Maybe it should have all been called "nospin". I
don't know anymore :)
_nolock() functions and ALLOC_NOLOCK are part of API, FPI_ is internal so
it's not that urgent. Furthermore:

> ---
>  mm/page_alloc.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 5fe1c11f919d7..ba8d882072de5 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -90,7 +90,7 @@ typedef int __bitwise fpi_t;
>  #define FPI_TO_TAIL		((__force fpi_t)BIT(1))
>  
>  /* Free the page without taking locks. Rely on trylock only. */

here's a "trylock"

> -#define FPI_TRYLOCK		((__force fpi_t)BIT(2))
> +#define FPI_NOLOCK		((__force fpi_t)BIT(2))

And here's not anymore.

>  
>  /* free_pages_prepare() has already been called for page(s) being freed. */
>  #define FPI_PREPARED		((__force fpi_t)BIT(3))
> @@ -1419,7 +1419,7 @@ static __always_inline bool __free_pages_prepare(struct page *page,
>  	page_table_check_free(page, order);
>  	pgalloc_tag_sub(page, 1 << order);
>  
> -	if (!PageHighMem(page) && !(fpi_flags & FPI_TRYLOCK)) {
> +	if (!PageHighMem(page) && !(fpi_flags & FPI_NOLOCK)) {
>  		debug_check_no_locks_freed(page_address(page),
>  					   PAGE_SIZE << order);
>  		debug_check_no_obj_freed(page_address(page),
> @@ -1558,7 +1558,7 @@ static void free_one_page(struct zone *zone, struct page *page,
>  	struct llist_head *llhead;
>  	unsigned long flags;
>  
> -	if (unlikely(fpi_flags & FPI_TRYLOCK)) {
> +	if (unlikely(fpi_flags & FPI_NOLOCK)) {
>  		if (!spin_trylock_irqsave(&zone->lock, flags)) {
>  			add_page_to_zone_llist(zone, page, order);
>  			return;
> @@ -1569,7 +1569,7 @@ static void free_one_page(struct zone *zone, struct page *page,
>  
>  	/* The lock succeeded. Process deferred pages. */
>  	llhead = &zone->trylock_free_pages;
> -	if (unlikely(!llist_empty(llhead) && !(fpi_flags & FPI_TRYLOCK))) {
> +	if (unlikely(!llist_empty(llhead) && !(fpi_flags & FPI_NOLOCK))) {
>  		struct llist_node *llnode;
>  		struct page *p, *tmp;
>  
> @@ -2882,7 +2882,7 @@ static bool free_frozen_page_commit(struct zone *zone,
>  	if (pcp->free_count < (batch << CONFIG_PCP_BATCH_SCALE_MAX))
>  		pcp->free_count += (1 << order);
>  
> -	if (unlikely(fpi_flags & FPI_TRYLOCK)) {
> +	if (unlikely(fpi_flags & FPI_NOLOCK)) {
>  		/*
>  		 * Do not attempt to take a zone lock. Let pcp->count get
>  		 * over high mark temporarily.
> @@ -2979,7 +2979,7 @@ static void __free_frozen_pages(struct page *page, unsigned int order,
>  		migratetype = MIGRATE_MOVABLE;
>  	}
>  
> -	if (unlikely((fpi_flags & FPI_TRYLOCK) && !can_spin_trylock())) {
> +	if (unlikely((fpi_flags & FPI_NOLOCK) && !can_spin_trylock())) {

can_spin_trylock() was matched with FPI_TRYLOCK, now not anymore

>  		add_page_to_zone_llist(zone, page, order);
>  		return;
>  	}
> @@ -3001,7 +3001,7 @@ void free_frozen_pages(struct page *page, unsigned int order)
>  
>  void free_frozen_pages_nolock(struct page *page, unsigned int order)
>  {
> -	__free_frozen_pages(page, order, FPI_TRYLOCK);
> +	__free_frozen_pages(page, order, FPI_NOLOCK);
>  }
>  
>  /*
> @@ -5409,7 +5409,7 @@ struct page *__alloc_frozen_pages_noprof(gfp_t gfp, unsigned int order,
>  	if (memcg_kmem_online() && (gfp & __GFP_ACCOUNT) && page &&
>  	    unlikely(__memcg_kmem_charge_page(page, gfp, order) != 0)) {
>  		__free_frozen_pages(page, order,
> -				    alloc_flags & ALLOC_NOLOCK ? FPI_TRYLOCK : 0);
> +				    alloc_flags & ALLOC_NOLOCK ? FPI_NOLOCK : 0);

Although here it does improve things. Sigh.

>  		page = NULL;
>  	}
>  
> @@ -5532,7 +5532,7 @@ EXPORT_SYMBOL(__free_pages);
>   */
>  void free_pages_nolock(struct page *page, unsigned int order)
>  {
> -	___free_pages(page, order, FPI_TRYLOCK);
> +	___free_pages(page, order, FPI_NOLOCK);
>  }
>  
>  /**
>