Hugepages need clear_user_highpage() not clear_highpage()

Hugepages need clear_user_highpage() not clear_highpage()

[David Gibson]

When hugepages are newly allocated to a file in mm/hugetlb.c, we clear
them with a call to clear_highpage() on each of the subpages.  We
should be using clear_user_highpage(): on powerpc, at least,
clear_highpage() doesn't correctly mark the page as icache dirty so if
the page is executed shortly after it's possible to get strange
results.

This is a bugfix and should go into 2.6.16.

Signed-off-by: David Gibson <dwg@au1.ibm.com>

Index: working-2.6/mm/hugetlb.c
===================================================================
--- working-2.6.orig/mm/hugetlb.c	2006-02-06 12:58:07.000000000 +1100
+++ working-2.6/mm/hugetlb.c	2006-02-06 12:58:19.000000000 +1100
@@ -107,7 +107,7 @@ struct page *alloc_huge_page(struct vm_a
 	set_page_count(page, 1);
 	page[1].mapping = (void *)free_huge_page;
 	for (i = 0; i < (HPAGE_SIZE/PAGE_SIZE); ++i)
-		clear_highpage(&page[i]);
+		clear_user_highpage(&page[i], addr);
 	return page;
 }
 


-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

Re: Hugepages need clear_user_highpage() not clear_highpage()

[William Lee Irwin III]

On Mon, Feb 06, 2006 at 01:18:53PM +1100, David Gibson wrote:
> When hugepages are newly allocated to a file in mm/hugetlb.c, we clear
> them with a call to clear_highpage() on each of the subpages.  We
> should be using clear_user_highpage(): on powerpc, at least,
> clear_highpage() doesn't correctly mark the page as icache dirty so if
> the page is executed shortly after it's possible to get strange
> results.
> This is a bugfix and should go into 2.6.16.
> Signed-off-by: David Gibson <dwg@au1.ibm.com>

Not sure how this got past the usual crapfilters. Sorry about that.

Acked-by: William Irwin <wli@holomorphy.com>


-- wli