Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752213Ab0DZOiJ (ORCPT ); Mon, 26 Apr 2010 10:38:09 -0400 Received: from 0122700014.0.fullrate.dk ([95.166.99.235]:55897 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751004Ab0DZOiH (ORCPT ); Mon, 26 Apr 2010 10:38:07 -0400 Date: Mon, 26 Apr 2010 16:38:03 +0200 From: Jens Axboe To: =?iso-8859-1?Q?J=F6rn?= Engel Cc: Linus Torvalds , David Woodhouse , linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org, Christoph Hellwig , Paolo Minazzi Subject: Re: [Patch] Catch filesystems lacking s_bdi Message-ID: <20100426143803.GM27497@kernel.dk> References: <20100422055448.GA27309@logfs.org> <20100422062631.GC27309@logfs.org> <20100422162709.GJ27497@kernel.dk> <20100422203358.GB30749@logfs.org> <20100423100532.GN27497@kernel.dk> <20100423205518.GB7008@logfs.org> <20100426094810.GE27497@kernel.dk> <20100426143253.GB4364@logfs.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20100426143253.GB4364@logfs.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4383 Lines: 77 On Mon, Apr 26 2010, J?rn Engel wrote: > > Yeah, it's a bad situation to be in. I changed that BUG_ON() to a > > WARN_ON(). I'm not too worried about that part, I'm more worried about > > the file system changed. OTOH, they do lack proper flushing now, so it's > > likely not a huge risk from that perspective. > > It is worse still. Using mtd->backing_dev_info results in > kernel BUG at fs/fs-writeback.c:157 > > which is BUG_ON(!work->seen); in bdi_queue_work(). Logfs is affected > and I bet jffs2 is as well. So much for dwmw2 or me actually testing > the fix. :( > > I did a hexdump to see what sb->s_bdi actually contained and the result > was this: > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 04 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 ........ > > Which should be mtd_bdi_unmappable. And at this point I have to admit > being clueless. What exactly should a struct backing_dev_info contain > and for what purposes? And where is this documented? The important bit is that each bdi must be initialized and registered if it's going to be handling dirty data, it can't just be a static placeholder. See the bdi_setup_and_register() helper I added. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/