Argh. Did not see this soon enougn. Maybe this one is better since it 
avoids the additional unlocks?

On Fri, 1 Feb 2008, Robin Holt wrote:

quoted text
> do_wp_page can reach the _end callout without passing the _begin
> callout.  This prevents making the _end unles the _begin has also
> been made.
> 
> Index: mmu_notifiers-cl-v5/mm/memory.c
> ===================================================================
> --- mmu_notifiers-cl-v5.orig/mm/memory.c	2008-02-01 04:44:03.000000000 -0600
> +++ mmu_notifiers-cl-v5/mm/memory.c	2008-02-01 04:46:18.000000000 -0600
> @@ -1564,7 +1564,7 @@ static int do_wp_page(struct mm_struct *
>  {
>  	struct page *old_page, *new_page;
>  	pte_t entry;
> -	int reuse = 0, ret = 0;
> +	int reuse = 0, ret = 0, invalidate_started = 0;
>  	int page_mkwrite = 0;
>  	struct page *dirty_page = NULL;
>  
> @@ -1649,6 +1649,8 @@ gotten:
>  
>  	mmu_notifier(invalidate_range_begin, mm, address,
>  				address + PAGE_SIZE, 0);
> +	invalidate_started = 1;
> +
>  	/*
>  	 * Re-check the pte - we dropped the lock
>  	 */
> @@ -1687,7 +1689,8 @@ gotten:
>  		page_cache_release(old_page);
>  unlock:
>  	pte_unmap_unlock(page_table, ptl);
> -	mmu_notifier(invalidate_range_end, mm,
> +	if (invalidate_started)
> +		mmu_notifier(invalidate_range_end, mm,
>  				address, address + PAGE_SIZE, 0);
>  	if (dirty_page) {
>  		if (vma->vm_file)
> 
--
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