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References: <20240214202055.77776-1-sidhartha.kumar@oracle.com>
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From: Alistair Popple <apopple@nvidia.com>
To: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
 akpm@linux-foundation.org, willy@infradead.org
Subject: Re: [PATCH 1/2] mm/migrate_device: further convert
 migrate_device_unmap() to folios
Date: Thu, 15 Feb 2024 09:38:42 +1100
In-reply-to: <20240214202055.77776-1-sidhartha.kumar@oracle.com>
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Sidhartha Kumar <sidhartha.kumar@oracle.com> writes:

> migrate_device_unmap() already has a folio, we can use the folio
> versions of is_zone_device_page() and putback_lru_page.
>
> Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
> ---
>  mm/migrate_device.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/mm/migrate_device.c b/mm/migrate_device.c
> index b6c27c76e1a0b..9152a329b0a68 100644
> --- a/mm/migrate_device.c
> +++ b/mm/migrate_device.c
> @@ -377,33 +377,33 @@ static unsigned long migrate_device_unmap(unsigned long *src_pfns,
>  			continue;
>  		}
>  
> +		folio = page_folio(page);

Instead of open coding the migrate pfn to folio conversion I think we
should define a migrate_pfn_to_folio() and get rid of the intermediate
local variable. This would also allow a minor clean up to the final for
loop in migrate_device_unmap().

>  		/* ZONE_DEVICE pages are not on LRU */
> -		if (!is_zone_device_page(page)) {
> -			if (!PageLRU(page) && allow_drain) {
> +		if (!folio_is_zone_device(folio)) {
> +			if (!folio_test_lru(folio) && allow_drain) {
>  				/* Drain CPU's lru cache */
>  				lru_add_drain_all();
>  				allow_drain = false;
>  			}
>  
> -			if (!isolate_lru_page(page)) {
> +			if (!folio_isolate_lru(folio)) {
>  				src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
>  				restore++;
>  				continue;
>  			}
>  
>  			/* Drop the reference we took in collect */
> -			put_page(page);
> +			folio_put(folio);
>  		}
>  
> -		folio = page_folio(page);
>  		if (folio_mapped(folio))
>  			try_to_migrate(folio, 0);
>  
> -		if (page_mapped(page) ||
> +		if (folio_mapped(folio) ||
>  		    !migrate_vma_check_page(page, fault_page)) {
> -			if (!is_zone_device_page(page)) {
> -				get_page(page);
> -				putback_lru_page(page);
> +			if (!folio_is_zone_device(folio)) {
> +				folio_get(folio);
> +				folio_putback_lru(folio);
>  			}
>  
>  			src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;