Re: [PATCH v2 01/11] hugetlb: set hugetlb page flag before optimizing vmemmap

[Mike Kravetz]

On 10/13/23 21:58, Naoya Horiguchi wrote:
> On Tue, Sep 05, 2023 at 02:44:00PM -0700, Mike Kravetz wrote:
> > 
> > Fixes: f41f2ed43ca5 ("mm: hugetlb: free the vmemmap pages associated with each HugeTLB page")
> > Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> 
> I saw that VM_WARN_ON_ONCE() in hugetlb_vmemmap_restore is triggered when
> memory_failure() is called on a free hugetlb page with vmemmap optimization
> disabled (the warning is not triggered if vmemmap optimization is enabled).
> I think that we need check folio_test_hugetlb() before dissolve_free_huge_page()
> calls hugetlb_vmemmap_restore_folio().
> 
> Could you consider adding some diff like below?
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -2312,15 +2312,16 @@ int dissolve_free_huge_page(struct page *page)
>  		 * Attempt to allocate vmemmmap here so that we can take
>  		 * appropriate action on failure.
>  		 */
> -		rc = hugetlb_vmemmap_restore_folio(h, folio);
> -		if (!rc) {
> -			update_and_free_hugetlb_folio(h, folio, false);
> -		} else {
> -			spin_lock_irq(&hugetlb_lock);
> -			add_hugetlb_folio(h, folio, false);
> -			h->max_huge_pages++;
> -			spin_unlock_irq(&hugetlb_lock);
> +		if (folio_test_hugetlb(folio)) {
> +			rc = hugetlb_vmemmap_restore_folio(h, folio);
> +			if (rc) {
> +				spin_lock_irq(&hugetlb_lock);
> +				add_hugetlb_folio(h, folio, false);
> +				h->max_huge_pages++;
> +				goto out;
> +			}
>  		}
> +		update_and_free_hugetlb_folio(h, folio, false);
>  
>  		return rc;
>  	}
> 

Hi Naoya,

I believe we need to set 'rc = 0' in the !folio_test_hugetlb().  I put
together the following patch based on mm-stable.  Please take a look.