From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta12.messagelabs.com (mail6.bemta12.messagelabs.com [216.82.250.247]) by kanga.kvack.org (Postfix) with ESMTP id CD289900001 for ; Thu, 2 Jun 2011 14:23:31 -0400 (EDT) Date: Thu, 2 Jun 2011 20:23:02 +0200 From: Andrea Arcangeli Subject: Re: [PATCH] mm: compaction: Abort compaction if too many pages are isolated and caller is asynchronous Message-ID: <20110602182302.GA2802@random.random> References: <20110530143109.GH19505@random.random> <20110530153748.GS5044@csn.ul.ie> <20110530165546.GC5118@suse.de> <20110530175334.GI19505@random.random> <20110531121620.GA3490@barrios-laptop> <20110531122437.GJ19505@random.random> <20110531133340.GB3490@barrios-laptop> <20110531141402.GK19505@random.random> <20110531143734.GB13418@barrios-laptop> <20110531143830.GC13418@barrios-laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110531143830.GC13418@barrios-laptop> Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: Mel Gorman , Mel Gorman , akpm@linux-foundation.org, Ury Stankevich , KOSAKI Motohiro , linux-kernel@vger.kernel.org, linux-mm@kvack.org 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 It's unsafe to run page_count during the physical pfn scan. Signed-off-by: Andrea Arcangeli --- 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org