From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx152.postini.com [74.125.245.152]) by kanga.kvack.org (Postfix) with SMTP id DB44F6B004D for ; Sat, 2 Jun 2012 00:59:17 -0400 (EDT) Received: by wefh52 with SMTP id h52so2365370wef.14 for ; Fri, 01 Jun 2012 21:59:16 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: <20120530163317.GA13189@redhat.com> <20120531005739.GA4532@redhat.com> <20120601023107.GA19445@redhat.com> <20120601161205.GA1918@redhat.com> <20120601171606.GA3794@redhat.com> From: Linus Torvalds Date: Fri, 1 Jun 2012 21:58:50 -0700 Message-ID: Subject: Re: WARNING: at mm/page-writeback.c:1990 __set_page_dirty_nobuffers+0x13a/0x170() Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Hugh Dickins Cc: Bartlomiej Zolnierkiewicz , Kyungmin Park , Marek Szyprowski , Mel Gorman , Minchan Kim , Rik van Riel , Dave Jones , Andrew Morton , Cong Wang , Markus Trippelsdorf , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Fri, Jun 1, 2012 at 9:40 PM, Hugh Dickins wrote: > > Move the lock after the loop, I think you meant. Well, I wasn't sure if anything inside the loop might need it. I don't *think* so, but at the same time, what protects "page_order(page)" (or, indeed PageBuddy()) from being stable while that loop content uses them? I don't understand that code at all. It does that crazy iteration over page, and changes "page" in random ways, and then finishes up with a totally new "page" value that is some random thing that is *after* the end_page thing. WHAT? The code makes no sense. It tests all those pages within the page-block, but then after it has done all those tests, it does the final set_pageblock_migratetype(..) move_freepages_block(..) using a page that is *beyond* the pageblock (and with the whole page_order() thing, who knows just how far beyond it?) It looks entirely too much like random-monkey code to me. Linus -- 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