linux-ext4 - Re: [PATCH v9 06/14] mm/gup: migrate device coherent pages when pinning instead of failing

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Date:   Mon, 18 Jul 2022 12:56:29 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Alex Sierra <alex.sierra@....com>, jgg@...dia.com
Cc:     Felix.Kuehling@....com, linux-mm@...ck.org, rcampbell@...dia.com,
        linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        hch@....de, jglisse@...hat.com, apopple@...dia.com,
        willy@...radead.org, akpm@...ux-foundation.org
Subject: Re: [PATCH v9 06/14] mm/gup: migrate device coherent pages when
 pinning instead of failing

On 15.07.22 17:05, Alex Sierra wrote:
> From: Alistair Popple <apopple@...dia.com>
> 
> Currently any attempts to pin a device coherent page will fail. This is
> because device coherent pages need to be managed by a device driver, and
> pinning them would prevent a driver from migrating them off the device.
> 
> However this is no reason to fail pinning of these pages. These are
> coherent and accessible from the CPU so can be migrated just like
> pinning ZONE_MOVABLE pages. So instead of failing all attempts to pin
> them first try migrating them out of ZONE_DEVICE.
> 
> [hch: rebased to the split device memory checks,
>       moved migrate_device_page to migrate_device.c]
> 
> Signed-off-by: Alistair Popple <apopple@...dia.com>
> Acked-by: Felix Kuehling <Felix.Kuehling@....com>
> Signed-off-by: Christoph Hellwig <hch@....de>

[...]

>  		/*
>  		 * Try to move out any movable page before pinning the range.
>  		 */
> @@ -1919,7 +1948,8 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages,
>  				    folio_nr_pages(folio));
>  	}
>  
> -	if (!list_empty(&movable_page_list) || isolation_error_count)
> +	if (!list_empty(&movable_page_list) || isolation_error_count
> +		|| coherent_pages)

The common style is to

a) add the || to the end of the previous line
b) indent such the we have a nice-to-read alignment

if (!list_empty(&movable_page_list) || isolation_error_count ||
    coherent_pages)


Apart from that lgtm.

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 
Thanks,

David / dhildenb