Re: Prezeroing V3 [1/4]: Allow request for zeroed memory

[Hugh Dickins]

On Tue, 4 Jan 2005, Christoph Lameter wrote:
> This patch introduces __GFP_ZERO as an additional gfp_mask element to allow
> to request zeroed pages from the page allocator.
> ...
> --- linux-2.6.10.orig/mm/memory.c	2005-01-04 12:16:41.000000000 -0800
> +++ linux-2.6.10/mm/memory.c	2005-01-04 12:16:49.000000000 -0800
> @@ -1650,10 +1650,9 @@
> 
>  		if (unlikely(anon_vma_prepare(vma)))
>  			goto no_mem;
> -		page = alloc_page_vma(GFP_HIGHUSER, vma, addr);
> +		page = alloc_page_vma(GFP_HIGHZERO, vma, addr);
>  		if (!page)
>  			goto no_mem;
> -		clear_user_highpage(page, addr);
> 
>  		spin_lock(&mm->page_table_lock);
>  		page_table = pte_offset_map(pmd, addr);

Christoph, a late comment: doesn't this effectively replace
do_anonymous_page's clear_user_highpage by clear_highpage, which would
be a bad idea (inefficient? or corrupting?) on those few architectures
which actually do something with that user addr?

Hugh

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