From: Christoph Hellwig <hch@lst.de>
To: Brian Foster <bfoster@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>, linux-xfs@vger.kernel.org
Subject: Re: [PATCH 4/4] xfs: don't block the log commit handler for discards
Date: Tue, 7 Feb 2017 10:50:49 +0100 [thread overview]
Message-ID: <20170207095049.GA15588@lst.de> (raw)
In-Reply-To: <20170206164924.GH57865@bfoster.bfoster>
On Mon, Feb 06, 2017 at 11:49:24AM -0500, Brian Foster wrote:
> > Can you explain in which contex you mean this? I'm a bit lost on this
> > comment unfortunately.
>
> Sorry.. what I'm concerned about is waiting on in-flight discards during
> unmount. The current discard code issues the discards synchronously and
> so the log force is sufficient to drain in-flight I/O before we start
> breaking down core data structures in the unmount path that would be
> referenced by end_io handlers and such.
>
> With this change, the log force can return with discards still in
> flight. In fact, a subsequent flush of the workqueue is not sufficient
> since there's no guarantee the work item has been queued by that point
> either. If we don't have unmount serialization against in-flight I/Os,
> this can lead to unmount crashes (see the I/O accounting infrastructure
> added in commit 9c7504aa7 for an example of this problem with async
> buffer I/Os). Am I missing something that protects us from this problem
> here?
No, you're right. We should have a xfs_extent_busy_flush_all call
in the unmount path. I'll resend the series again with that added.
next prev parent reply other threads:[~2017-02-07 9:50 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-29 18:43 improve busy extent handling and add async discard support Christoph Hellwig
2017-01-29 18:43 ` [PATCH 1/4] xfs: don't fail xfs_extent_busy allocation Christoph Hellwig
2017-02-03 15:20 ` Brian Foster
2017-02-04 9:50 ` Christoph Hellwig
2017-02-06 16:43 ` Brian Foster
2017-02-07 9:42 ` Christoph Hellwig
2017-01-29 18:43 ` [PATCH 2/4] xfs: improve handling of busy extents in the low-level allocator Christoph Hellwig
2017-02-03 15:22 ` Brian Foster
2017-02-04 9:54 ` Christoph Hellwig
2017-02-03 16:22 ` Brian Foster
2017-02-04 9:56 ` Christoph Hellwig
2017-02-06 16:47 ` Brian Foster
2017-02-07 9:43 ` Christoph Hellwig
2017-02-07 13:13 ` Brian Foster
2017-02-07 15:45 ` Christoph Hellwig
2017-01-29 18:43 ` [PATCH 3/4] xfs: improve busy extent sorting Christoph Hellwig
2017-02-03 15:22 ` Brian Foster
2017-02-04 9:58 ` Christoph Hellwig
2017-01-29 18:43 ` [PATCH 4/4] xfs: don't block the log commit handler for discards Christoph Hellwig
2017-02-03 16:22 ` Brian Foster
2017-02-04 9:59 ` Christoph Hellwig
2017-02-06 16:49 ` Brian Foster
2017-02-07 9:50 ` Christoph Hellwig [this message]
2017-02-05 17:11 improve busy extent handling and add async discard support V2 Christoph Hellwig
2017-02-05 17:11 ` [PATCH 4/4] xfs: don't block the log commit handler for discards Christoph Hellwig
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