From: Dave Chinner <david@fromorbit.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: majianpeng <majianpeng@gmail.com>, tj <tj@kernel.org>,
axboe <axboe@kernel.dk>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [RESEND PATCH] writeback: Judge bdi->dev when set worker desc in bdi_writeback_workfn.
Date: Fri, 27 Sep 2013 08:59:09 +1000 [thread overview]
Message-ID: <20130926225909.GU26872@dastard> (raw)
In-Reply-To: <20130926174702.GA12274@infradead.org>
On Thu, Sep 26, 2013 at 10:47:02AM -0700, Christoph Hellwig wrote:
> On Thu, Sep 26, 2013 at 08:43:51AM +1000, Dave Chinner wrote:
> > You're just papering over the larger problem, in that the writeback
> > work is running concurrently with the bdi_unregister() function that
> > is tearing the bdi down. You should try to fix the underlying race
> > condition, as documented in bdi_destroy.
>
> The problem is even worse than that, and it's the lack of a proper
> refcounting on the bdi as seen by gems like bdi_prune_sb and the moving
> of writeback requests in bdi_destroy. The right fix is to dynamically
> allocate the bdi (or at least the bdi_writeback), and make sure that we
> keep it around as long as a filesystem and thus the writeback code
> refers to. Then a block device going away can just set a flag to stop
> writeback from trying instead of having the bdi ripped out underneath
> it which is guaranteed to fail and historically has failed in a large
> number of misterious ways.
Yup, be nice to see this rat-hole cleaned up properly, especially
those silly "pull disk, unplug-runs-sync_fs, fs hangs trying to do
IO to the disk that just got unplugged" bugs we get reported every
so often.
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
prev parent reply other threads:[~2013-09-26 22:59 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-10 0:11 [RESEND PATCH] writeback: Judge bdi->dev when set worker desc in bdi_writeback_workfn majianpeng
2013-09-25 8:08 ` majianpeng
2013-09-25 22:43 ` Dave Chinner
2013-09-26 13:35 ` tj
2013-09-26 17:47 ` Christoph Hellwig
2013-09-26 22:59 ` Dave Chinner [this message]
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