From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id AD9F86B0011 for ; Tue, 31 May 2011 10:37:45 -0400 (EDT) Received: by pzk4 with SMTP id 4so2551282pzk.14 for ; Tue, 31 May 2011 07:37:43 -0700 (PDT) Date: Tue, 31 May 2011 23:37:35 +0900 From: Minchan Kim Subject: Re: [PATCH] mm: compaction: Abort compaction if too many pages are isolated and caller is asynchronous Message-ID: <20110531143734.GB13418@barrios-laptop> References: <20110530131300.GQ5044@csn.ul.ie> <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110531141402.GK19505@random.random> Sender: owner-linux-mm@kvack.org List-ID: To: Andrea Arcangeli Cc: Mel Gorman , Mel Gorman , akpm@linux-foundation.org, Ury Stankevich , KOSAKI Motohiro , linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@kernel.org On Tue, May 31, 2011 at 04:14:02PM +0200, Andrea Arcangeli wrote: > On Tue, May 31, 2011 at 10:33:40PM +0900, Minchan Kim wrote: > > I checked them before sending patch but I got failed to find strange things. :( > > My review also doesn't show other bugs in migrate_pages callers like > that one. > > > Now I am checking the page's SwapBacked flag can be changed > > between before and after of migrate_pages so accounting of NR_ISOLATED_XX can > > make mistake. I am approaching the failure, too. Hmm. > > When I checked that, I noticed the ClearPageSwapBacked in swapcache if > radix insertion fails, but that happens before adding the page in the > LRU so it shouldn't have a chance to be isolated. True. > > So far I only noticed an unsafe page_count in > vmscan.c:isolate_lru_pages but that should at worst result in a > invalid pointer dereference as random result from that page_count is > not going to hurt and I think it's only a theoretical issue. Yes. You find a new BUG. It seems to be related to this problem but it should be solved although it's very rare case. -- Kind regards Minchan Kim -- 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