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SubjectRe: [BUG] 2.6.25-rc3-mm1 kernel bug while running libhugetlbfs
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On Tue, 2008-03-04 at 11:51 -0800, Andrew Morton wrote:
> hugetlb-correct-page-count-for-surplus-huge-pages.patch adds:
>
> if (page) {
> /*
> * This page is now managed by the hugetlb allocator and has
> * no users -- drop the buddy allocator's reference.
> */
> int page_count = put_page_testzero(page);
> BUG_ON(page_count != 0);
>
>

Ugh I got bitten by put_page_testzero(). When it returns 1, the page
count is zero (not the page count).

My initial version had a BUG_ON() with side-effects. When a reviewer
pointed it out, I thought I could fix the patch up on its way out the
door. I have self-administered my punishment. This patch will fix it:

Signed-off-by: Adam Litke <agl@us.ibm.com>

--- mm/hugetlb.c.orig 2008-03-04 13:36:30.000000000 -0800
+++ mm/hugetlb.c 2008-03-04 13:39:30.000000000 -0800
@@ -291,8 +291,8 @@ static struct page *alloc_buddy_huge_pag
* This page is now managed by the hugetlb allocator and has
* no users -- drop the buddy allocator's reference.
*/
- int page_count = put_page_testzero(page);
- BUG_ON(page_count != 0);
+ put_page_testzero(page);
+ VM_BUG_ON(page_count(page));
nid = page_to_nid(page);
set_compound_page_dtor(page, free_huge_page);
/*
--
Adam Litke - (agl at us.ibm.com)
IBM Linux Technology Center



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