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 <[EMAIL PROTECTED]>

--- 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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