Re: [RFC PATCH v1 1/7] mm: hugetlb: Consolidate interpretation of gbl_chg within alloc_hugetlb_folio()

[Joshua Hahn]

On Wed, 11 Feb 2026 16:37:12 -0800 Ackerley Tng <ackerleytng@xxxxxxxxxx> wrote:

> Previously, gbl_chg was passed from alloc_hugetlb_folio() into
> dequeue_hugetlb_folio_vma(), leaking the concept of gbl_chg into
> dequeue_hugetlb_folio_vma().
> 
> This patch consolidates the interpretation of gbl_chg into
> alloc_hugetlb_folio(), also renaming dequeue_hugetlb_folio_vma() to
> dequeue_hugetlb_folio() so dequeue_hugetlb_folio() can just focus on
> dequeuing a folio.
> 
> No functional change intended.
> 
> Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
> Reviewed-by: James Houghton <jthoughton@xxxxxxxxxx>

Makes sense to me, this seems like a reasonable semantic change even
without factoring out hugetlb_alloc_folio. Thank you!

Reviewed-by: Joshua Hahn <joshua.hahnjy@xxxxxxxxx>

> ---
>  mm/hugetlb.c | 24 +++++++++---------------
>  1 file changed, 9 insertions(+), 15 deletions(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index a1832da0f6236..fd067bd394ee0 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1380,7 +1380,7 @@ static unsigned long available_huge_pages(struct hstate *h)
>  
>  static struct folio *dequeue_hugetlb_folio_vma(struct hstate *h,
>  				struct vm_area_struct *vma,
> -				unsigned long address, long gbl_chg)
> +				unsigned long address)
>  {
>  	struct folio *folio = NULL;
>  	struct mempolicy *mpol;
> @@ -1388,13 +1388,6 @@ static struct folio *dequeue_hugetlb_folio_vma(struct hstate *h,
>  	nodemask_t *nodemask;
>  	int nid;
>  
> -	/*
> -	 * gbl_chg==1 means the allocation requires a new page that was not
> -	 * reserved before.  Making sure there's at least one free page.
> -	 */
> -	if (gbl_chg && !available_huge_pages(h))
> -		goto err;
> -
>  	gfp_mask = htlb_alloc_mask(h);
>  	nid = huge_node(vma, address, gfp_mask, &mpol, &nodemask);
>  
> @@ -1412,9 +1405,6 @@ static struct folio *dequeue_hugetlb_folio_vma(struct hstate *h,
>  
>  	mpol_cond_put(mpol);
>  	return folio;
> -
> -err:
> -	return NULL;
>  }
>  
>  #ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
> @@ -2962,12 +2952,16 @@ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma,
>  		goto out_uncharge_cgroup_reservation;
>  
>  	spin_lock_irq(&hugetlb_lock);
> +
>  	/*
> -	 * glb_chg is passed to indicate whether or not a page must be taken
> -	 * from the global free pool (global change).  gbl_chg == 0 indicates
> -	 * a reservation exists for the allocation.
> +	 * gbl_chg == 0 indicates a reservation exists for the allocation - so
> +	 * try dequeuing a page. If there are available_huge_pages(), try using
> +	 * them!
>  	 */
> -	folio = dequeue_hugetlb_folio_vma(h, vma, addr, gbl_chg);
> +	folio = NULL;
> +	if (!gbl_chg || available_huge_pages(h))
> +		folio = dequeue_hugetlb_folio_vma(h, vma, addr);
> +
>  	if (!folio) {
>  		spin_unlock_irq(&hugetlb_lock);
>  		folio = alloc_buddy_hugetlb_folio_with_mpol(h, vma, addr);
> -- 
> 2.53.0.310.g728cabbaf7-goog
> 
>