linux-kernel - Re: [PATCH] 2/4 move all invalidate_page outside of PT lock (#v9 was 1/4)

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Date:	Fri, 7 Mar 2008 11:54:32 -0800 (PST)
From:	Christoph Lameter <clameter@....com>
To:	Andrea Arcangeli <andrea@...ranet.com>
cc:	Jack Steiner <steiner@....com>, Nick Piggin <npiggin@...e.de>,
	akpm@...ux-foundation.org, Robin Holt <holt@....com>,
	Avi Kivity <avi@...ranet.com>, kvm-devel@...ts.sourceforge.net,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	general@...ts.openfabrics.org,
	Steve Wise <swise@...ngridcomputing.com>,
	Roland Dreier <rdreier@...co.com>,
	Kanoj Sarcar <kanojsarcar@...oo.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	daniel.blueman@...drics.com
Subject: Re: [PATCH] 2/4 move all invalidate_page outside of PT lock (#v9
 was 1/4)

On Fri, 7 Mar 2008, Andrea Arcangeli wrote:

> This below simple patch invalidates the "invalidate_page" part, the
> next patch will invalidate the RCU part, and btw in a way that doesn't
> forbid unregistering the mmu notifiers at runtime (like your brand new
> EMM does).

Sounds good.

> The reason I keep this incremental (unlike your EMM that does
> everything all at the same time mixed in a single patch) is to
> decrease the non obviously safe mangling over mm/* during .25. The
> below patch is simple, but not as obviously safe as
> s/ptep_clear_flush/ptep_clear_flush_notify/.

There was never a chance to merge for .25. Lets drop that and focus on 
a solution that is good for all.

>  #endif /* _LINUX_MMU_NOTIFIER_H */
> diff --git a/mm/filemap_xip.c b/mm/filemap_xip.c
> --- a/mm/filemap_xip.c
> +++ b/mm/filemap_xip.c
> @@ -194,11 +194,13 @@ __xip_unmap (struct address_space * mapp
>  		if (pte) {
>  			/* Nuke the page table entry. */
>  			flush_cache_page(vma, address, pte_pfn(*pte));
> -			pteval = ptep_clear_flush_notify(vma, address, pte);
> +			pteval = ptep_clear_flush(vma, address, pte);
>  			page_remove_rmap(page, vma);
>  			dec_mm_counter(mm, file_rss);
>  			BUG_ON(pte_dirty(pteval));
>  			pte_unmap_unlock(pte, ptl);
> +			/* must invalidate_page _before_ freeing the page */
> +			mmu_notifier_invalidate_page(mm, address);
>  			page_cache_release(page);
>  		}
>  	}

Ok but we still hold the i_mmap_lock here.


> @@ -834,6 +846,8 @@ static void try_to_unmap_cluster(unsigne
>  	if (!pmd_present(*pmd))
>  		return;
>  
> +	start = address;
> +	mmu_notifier_invalidate_range_begin(mm, start, end);

Hmmmm.. Okay you going for range invalidate here like EMM but there are 
still some invalidate_pages() left.

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