linux-kernel - Re: [PATCH 28/83] mm: Change timing of notification to IOMMUs about a page to be invalidated

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Date:	Fri, 11 Jul 2014 00:22:00 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	Oded Gabbay <oded.gabbay@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	David Airlie <airlied@...ux.ie>,
	Alex Deucher <alexander.deucher@....com>,
	Jerome Glisse <j.glisse@...il.com>,
	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	John Bridgman <John.Bridgman@....com>,
	Andrew Lewycky <Andrew.Lewycky@....com>,
	linux-mm <linux-mm@...ck.org>, Oded Gabbay <oded.gabbay@....com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Hugh Dickins <hughd@...gle.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Jérôme Glisse <jglisse@...hat.com>,
	Jianyu Zhan <nasa4836@...il.com>
Subject: Re: [PATCH 28/83] mm: Change timing of notification to IOMMUs about
 a page to be invalidated

On Fri, Jul 11, 2014 at 12:53:26AM +0300, Oded Gabbay wrote:
>  mm/rmap.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 196cd0c..73d4c3d 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1231,13 +1231,17 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
>  	} else
>  		dec_mm_counter(mm, MM_FILEPAGES);
>  
> +	pte_unmap_unlock(pte, ptl);
> +
> +	mmu_notifier_invalidate_page(vma, address, event);
> +
>  	page_remove_rmap(page);
>  	page_cache_release(page);
>  
> +	return ret;
> +
>  out_unmap:
>  	pte_unmap_unlock(pte, ptl);
> -	if (ret != SWAP_FAIL && !(flags & TTU_MUNLOCK))
> -		mmu_notifier_invalidate_page(vma, address, event);
>  out:
>  	return ret;

I think there is no bug. In that function the page is just unmapped,
removed from the rmap (page_remove_rmap), and the LRU list
(page_cache_release). The page itself is not released in this function,
so the call mmu_notifier_invalidate_page() at the end is fine.


	Joerg


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