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Date:   Mon, 18 Jul 2022 12:56:29 +0200
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Subject: Re: [PATCH v9 06/14] mm/gup: migrate device coherent pages when
 pinning instead of failing
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To:     Alex Sierra <alex.sierra@amd.com>, jgg@nvidia.com
Cc:     Felix.Kuehling@amd.com, linux-mm@kvack.org, rcampbell@nvidia.com,
        linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org,
        amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
        hch@lst.de, jglisse@redhat.com, apopple@nvidia.com,
        willy@infradead.org, akpm@linux-foundation.org
References: <20220715150521.18165-1-alex.sierra@amd.com>
 <20220715150521.18165-7-alex.sierra@amd.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
In-Reply-To: <20220715150521.18165-7-alex.sierra@amd.com>
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On 15.07.22 17:05, Alex Sierra wrote:
> From: Alistair Popple <apopple@nvidia.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@nvidia.com>
> Acked-by: Felix Kuehling <Felix.Kuehling@amd.com>
> Signed-off-by: Christoph Hellwig <hch@lst.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@redhat.com>

-- 
Thanks,

David / dhildenb