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Date: Thu, 2 Jun 2011 20:23:02 +0200 From: Andrea Arcangeli <aarcange@...hat.com> To: Minchan Kim <minchan.kim@...il.com> Cc: Mel Gorman <mgorman@...e.de>, Mel Gorman <mel@....ul.ie>, akpm@...ux-foundation.org, Ury Stankevich <urykhy@...il.com>, KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>, linux-kernel@...r.kernel.org, linux-mm@...ck.org Subject: Re: [PATCH] mm: compaction: Abort compaction if too many pages are isolated and caller is asynchronous On Tue, May 31, 2011 at 11:38:30PM +0900, Minchan Kim wrote: > > Yes. You find a new BUG. > > It seems to be related to this problem but it should be solved although > > typo : It doesn't seem to be. This should fix it, but I doubt it matters for this problem. === Subject: mm: no page_count without a page pin From: Andrea Arcangeli <aarcange@...hat.com> It's unsafe to run page_count during the physical pfn scan. Signed-off-by: Andrea Arcangeli <aarcange@...hat.com> --- diff --git a/mm/vmscan.c b/mm/vmscan.c index faa0a08..e41e78a 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1124,8 +1124,18 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, nr_lumpy_dirty++; scan++; } else { - /* the page is freed already. */ - if (!page_count(cursor_page)) + /* + * We can't use page_count() as that + * requires compound_head and we don't + * have a pin on the page here. If a + * page is tail, we may or may not + * have isolated the head, so assume + * it's not free, it'd be tricky to + * track the head status without a + * page pin. + */ + if (!PageTail(cursor_page) && + !atomic_read(&cursor_page->_count)) continue; break; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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