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Message-Id: <1204668089.14779.92.camel@localhost.localdomain>
Date: Tue, 04 Mar 2008 16:01:29 -0600
From: Adam Litke <agl@...ibm.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org,
apw@...dowen.org, balbir@...ux.vnet.ibm.com
Subject: Re: [BUG] 2.6.25-rc3-mm1 kernel bug while running libhugetlbfs
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@...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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