Re: [patch 1/9] mm: migrate: use thp_order instead of HPAGE_PMD_ORDER for new page allocation.

[Matthew Wilcox <willy@infradead.org>]

On Fri, Apr 08, 2022 at 01:08:52PM -0700, Andrew Morton wrote:
> From: Zi Yan <ziy@nvidia.com>
> Subject: mm: migrate: use thp_order instead of HPAGE_PMD_ORDER for new page allocation.
> 
> Fix a VM_BUG_ON_FOLIO(folio_nr_pages(old) != nr_pages) crash.
> 
> With folios support, it is possible to have other than HPAGE_PMD_ORDER
> THPs, in the form of folios, in the system.  Use thp_order() to correctly
> determine the source page order during migration.

This one's now obsolete after the folio pull request Linus merged
earlier today.

> Link: https://lkml.kernel.org/r/20220404165325.1883267-1-zi.yan@sent.com
> Link: https://lore.kernel.org/linux-mm/20220404132908.GA785673@u2004/
> Fixes: d68eccad3706 ("mm/filemap: Allow large folios to be added to the page cache")
> Reported-by: Naoya Horiguchi <naoya.horiguchi@linux.dev>
> Signed-off-by: Zi Yan <ziy@nvidia.com>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Michal Hocko <mhocko@kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
> 
>  mm/mempolicy.c |    2 +-
>  mm/migrate.c   |    2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> --- a/mm/mempolicy.c~mm-migrate-use-thp_order-instead-of-hpage_pmd_order-for-new-page-allocation
> +++ a/mm/mempolicy.c
> @@ -1209,7 +1209,7 @@ static struct page *new_page(struct page
>  		struct page *thp;
>  
>  		thp = alloc_hugepage_vma(GFP_TRANSHUGE, vma, address,
> -					 HPAGE_PMD_ORDER);
> +					 thp_order(page));
>  		if (!thp)
>  			return NULL;
>  		prep_transhuge_page(thp);
> --- a/mm/migrate.c~mm-migrate-use-thp_order-instead-of-hpage_pmd_order-for-new-page-allocation
> +++ a/mm/migrate.c
> @@ -1547,7 +1547,7 @@ struct page *alloc_migration_target(stru
>  		 */
>  		gfp_mask &= ~__GFP_RECLAIM;
>  		gfp_mask |= GFP_TRANSHUGE;
> -		order = HPAGE_PMD_ORDER;
> +		order = thp_order(page);
>  	}
>  	zidx = zone_idx(page_zone(page));
>  	if (is_highmem_idx(zidx) || zidx == ZONE_MOVABLE)
> _
>