linux-kernel - Re: [PATCH v6v3 02/12] mm: migrate: support non-lru movable page migration

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Date:	Mon, 13 Jun 2016 15:08:19 +0530
From:	Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:	Minchan Kim <minchan@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
CC:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Rik van Riel <riel@...hat.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Mel Gorman <mgorman@...e.de>, Hugh Dickins <hughd@...gle.com>,
	Rafael Aquini <aquini@...hat.com>,
	virtualization@...ts.linux-foundation.org,
	Jonathan Corbet <corbet@....net>,
	John Einar Reitan <john.reitan@...s.arm.com>,
	dri-devel@...ts.freedesktop.org,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Gioh Kim <gi-oh.kim@...fitbricks.com>
Subject: Re: [PATCH v6v3 02/12] mm: migrate: support non-lru movable page
 migration

On 05/31/2016 05:31 AM, Minchan Kim wrote:
> @@ -791,6 +921,7 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
>  	int rc = -EAGAIN;
>  	int page_was_mapped = 0;
>  	struct anon_vma *anon_vma = NULL;
> +	bool is_lru = !__PageMovable(page);
>  
>  	if (!trylock_page(page)) {
>  		if (!force || mode == MIGRATE_ASYNC)
> @@ -871,6 +1002,11 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
>  		goto out_unlock_both;
>  	}
>  
> +	if (unlikely(!is_lru)) {
> +		rc = move_to_new_page(newpage, page, mode);
> +		goto out_unlock_both;
> +	}
> +

Hello Minchan,

I might be missing something here but does this implementation support the
scenario where these non LRU pages owned by the driver mapped as PTE into
process page table ? Because the "goto out_unlock_both" statement above
skips all the PTE unmap, putting a migration PTE and removing the migration
PTE steps.

Regards
Anshuman