From: Jens Axboe <jens.axboe@oracle.com>
To: "Jörn Engel" <joern@logfs.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
David Woodhouse <dwmw2@infradead.org>,
linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org,
Christoph Hellwig <hch@infradead.org>,
Paolo Minazzi <paolo.minazzi@gmail.com>
Subject: Re: [Patch] Catch filesystems lacking s_bdi
Date: Mon, 26 Apr 2010 16:45:32 +0200 [thread overview]
Message-ID: <20100426144532.GN27497@kernel.dk> (raw)
In-Reply-To: <20100426143803.GM27497@kernel.dk>
On Mon, Apr 26 2010, Jens Axboe wrote:
> On Mon, Apr 26 2010, Jörn 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.
Took a quick look, and you want bdi_setup_and_register() for the three
bdis listed in mtdbdi.c in mtdcore.c:init_mtd(). Or manual bdi_init()
and bdi_register(). I'll take a look post-dinner. Either is workable,
but since the flags are already setup, the latter may be cleaner.
--
Jens Axboe
next prev parent reply other threads:[~2010-04-26 14:45 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-17 18:40 [PATCH] [MTD] Fix JFFS2 sync silent failure Jörn Engel
2010-04-19 7:38 ` Jens Axboe
2010-04-19 10:15 ` Jörn Engel
2010-04-19 10:20 ` Jens Axboe
2010-04-19 11:39 ` Jörn Engel
2010-04-22 5:54 ` Jörn Engel
2010-04-22 6:26 ` Jörn Engel
2010-04-22 14:25 ` Linus Torvalds
2010-04-22 14:33 ` Linus Torvalds
2010-04-22 16:27 ` Jens Axboe
2010-04-22 20:33 ` [Patch] Catch filesystems lacking s_bdi Jörn Engel
2010-04-23 10:05 ` Jens Axboe
2010-04-23 20:55 ` Jörn Engel
2010-04-26 9:48 ` Jens Axboe
2010-04-26 14:32 ` Jörn Engel
2010-04-26 14:38 ` Jens Axboe
2010-04-26 14:45 ` Jens Axboe [this message]
2010-04-26 16:30 ` [PATCH 1/2] [MTD] Move mtd_bdi_*mappable to mtdcore.c Jörn Engel
2010-04-26 16:31 ` [PATCH 2/2] [MTD] Call bdi_init() and bdi_register() Jörn Engel
2010-04-26 17:02 ` Jens Axboe
2010-04-26 17:12 ` Jörn Engel
2010-04-27 7:52 ` Jens Axboe
2010-04-27 8:11 ` Paolo Minazzi
2010-04-27 8:16 ` Jens Axboe
2010-04-27 11:29 ` Jörn Engel
2010-04-27 11:33 ` Jens Axboe
2010-04-27 9:01 ` Paolo Minazzi
2010-04-27 9:16 ` Jens Axboe
2010-04-27 9:26 ` Paolo Minazzi
2010-04-27 9:29 ` Jens Axboe
2010-04-27 9:36 ` Paolo Minazzi
2010-04-27 11:17 ` Jörn Engel
2010-04-27 11:31 ` Paolo Minazzi
2010-04-27 11:40 ` Jörn Engel
2010-04-27 11:48 ` [PATCH] [LogFS] Return -EINVAL if filesystem image doesn't match Jörn Engel
2010-04-27 12:53 ` Paolo Minazzi
2010-04-27 11:54 ` [PATCH 2/2] [MTD] Call bdi_init() and bdi_register() Paolo Minazzi
2010-04-27 12:05 ` Jörn Engel
2010-04-26 17:01 ` [PATCH 1/2] [MTD] Move mtd_bdi_*mappable to mtdcore.c Jens Axboe
2010-04-26 17:08 ` Jörn Engel
2010-04-26 17:10 ` Jens Axboe
2010-04-22 9:03 ` [PATCH] [MTD] Fix JFFS2 sync silent failure Jens Axboe
2010-04-22 10:39 ` Jens Axboe
2010-04-22 10:58 ` David Woodhouse
2010-04-22 11:05 ` Jens Axboe
2010-04-22 11:55 ` Jörn Engel
2010-04-22 12:08 ` Jens Axboe
2010-04-22 12:17 ` Jörn Engel
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