Re: [PATCH 1/3] HWPOISON, hugetlbfs: fix warning on freeing hwpoisoned hugepage

[Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>]

On Thu, Dec 06, 2012 at 06:20:24PM -0800, Andrew Morton wrote:
> On Thu,  6 Dec 2012 21:03:44 -0500 Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> wrote:
> 
> > This patch fixes the warning from __list_del_entry() which is triggered
> > when a process tries to do free_huge_page() for a hwpoisoned hugepage.
> > 
> > ChangeLog v2:
> >  - simply use list_del_init instead of introducing new hugepage list
> > 
> > Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> > ---
> >  mm/hugetlb.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > index 59a0059..9308752 100644
> > --- a/mm/hugetlb.c
> > +++ b/mm/hugetlb.c
> > @@ -3170,7 +3170,7 @@ int dequeue_hwpoisoned_huge_page(struct page *hpage)
> >  
> >  	spin_lock(&hugetlb_lock);
> >  	if (is_hugepage_on_freelist(hpage)) {
> > -		list_del(&hpage->lru);
> > +		list_del_init(&hpage->lru);
> 
> Can we please have a code comment in here explaining why
> list_del_init() is used?

OK, I added it.
---
From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Date: Thu, 6 Dec 2012 20:54:30 -0500
Subject: [PATCH v3] HWPOISON, hugetlbfs: fix warning on freeing hwpoisoned
 hugepage

This patch fixes the warning from __list_del_entry() which is triggered
when a process tries to do free_huge_page() for a hwpoisoned hugepage.

ChangeLog v3:
 - add comment

ChangeLog v2:
 - simply use list_del_init instead of introducing new hugepage list

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
---
 mm/hugetlb.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 59a0059..df03345 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3170,7 +3170,12 @@ int dequeue_hwpoisoned_huge_page(struct page *hpage)
 
 	spin_lock(&hugetlb_lock);
 	if (is_hugepage_on_freelist(hpage)) {
-		list_del(&hpage->lru);
+		/* 
+		 * Hwpoisoned hugepage isn't linked to activelist or freelist,
+		 * but dangling hpage->lru can trigger list-debug warnings,
+		 * so let it point to itself with list_del_init().
+		 */
+		list_del_init(&hpage->lru);
 		set_page_refcounted(hpage);
 		h->free_huge_pages--;
 		h->free_huge_pages_node[nid]--;
-- 
1.7.11.7

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