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 16:38:03 +0200 [thread overview]
Message-ID: <20100426143803.GM27497@kernel.dk> (raw)
In-Reply-To: <20100426143253.GB4364@logfs.org>
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.
--
Jens Axboe
next prev parent reply other threads:[~2010-04-26 14:38 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 [this message]
2010-04-26 14:45 ` Jens Axboe
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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