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Date:   Fri, 6 Jan 2023 16:54:37 -0800
From:   Mike Kravetz <mike.kravetz@oracle.com>
To:     Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        akpm@linux-foundation.org, songmuchun@bytedance.com,
        willy@infradead.org, tsahu@linux.ibm.com, jhubbard@nvidia.com
Subject: Re: [PATCH mm-unstable 6/8] mm/hugetlb: convert
 alloc_migrate_huge_page to folios
Message-ID: <Y7jCzW6oqlHpxusA@monkey>
References: <20230103191340.116536-1-sidhartha.kumar@oracle.com>
 <20230103191340.116536-7-sidhartha.kumar@oracle.com>
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On 01/03/23 13:13, Sidhartha Kumar wrote:
> Change alloc_huge_page_nodemask() to alloc_hugetlb_folio_nodemask() and
> alloc_migrate_huge_page() to alloc_migrate_hugetlb_folio(). Both functions
> now return a folio rather than a page.

>  /* mempolicy aware migration callback */
> @@ -2357,16 +2357,16 @@ struct page *alloc_huge_page_vma(struct hstate *h, struct vm_area_struct *vma,
>  {
>  	struct mempolicy *mpol;
>  	nodemask_t *nodemask;
> -	struct page *page;
> +	struct folio *folio;
>  	gfp_t gfp_mask;
>  	int node;
>  
>  	gfp_mask = htlb_alloc_mask(h);
>  	node = huge_node(vma, address, gfp_mask, &mpol, &nodemask);
> -	page = alloc_huge_page_nodemask(h, node, nodemask, gfp_mask);
> +	folio = alloc_hugetlb_folio_nodemask(h, node, nodemask, gfp_mask);
>  	mpol_cond_put(mpol);
>  
> -	return page;
> +	return &folio->page;

Is it possible that folio could be NULL here and cause addressing exception?

> diff --git a/mm/migrate.c b/mm/migrate.c
> index 6932b3d5a9dd..fab706b78be1 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1622,6 +1622,7 @@ struct page *alloc_migration_target(struct page *page, unsigned long private)
>  	struct migration_target_control *mtc;
>  	gfp_t gfp_mask;
>  	unsigned int order = 0;
> +	struct folio *hugetlb_folio = NULL;
>  	struct folio *new_folio = NULL;
>  	int nid;
>  	int zidx;
> @@ -1636,7 +1637,9 @@ struct page *alloc_migration_target(struct page *page, unsigned long private)
>  		struct hstate *h = folio_hstate(folio);
>  
>  		gfp_mask = htlb_modify_alloc_mask(h, gfp_mask);
> -		return alloc_huge_page_nodemask(h, nid, mtc->nmask, gfp_mask);
> +		hugetlb_folio = alloc_hugetlb_folio_nodemask(h, nid,
> +						mtc->nmask, gfp_mask);
> +		return &hugetlb_folio->page;

and, here as well?
-- 
Mike Kravetz

>  	}
>  
>  	if (folio_test_large(folio)) {
> -- 
> 2.39.0
>