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Date: Sun, 23 Mar 2025 07:28:37 +0100
From: Christoph Hellwig <hch@lst.de>
To: Benjamin Marzinski <bmarzins@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>, snitzer@kernel.org, mpatocka@redhat.com,
	dm-devel@lists.linux.dev, Damien Le Moal <dlemoal@kernel.org>
Subject: Re: [PATCH] dm-delay: support zoned devices
Message-ID: <20250323062837.GA30617@lst.de>
References: <20250321071816.1674943-1-hch@lst.de> <Z92naQRO2DrpMnXE@redhat.com>
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On Fri, Mar 21, 2025 at 01:52:41PM -0400, Benjamin Marzinski wrote:
> On Fri, Mar 21, 2025 at 08:18:16AM +0100, Christoph Hellwig wrote:
> > Add support for zoned device by passing through report_zoned to the
> > underlying read device.
> > 
> > This is required to make enable xfstests xfs/311 on zoned devices.
> 
> On suspend, delay_presuspend() stops delaying and it doesn't guarantee
> that new bios coming in will always be submitted after the delayed bios
> it is flushing. That can mess things up for zoned devices. I didn't
> check if that matters for the specific test. Setting
> 
> ti->emulate_zone_append = true;
> 
> would enforce write ordering, at the expense of adding a whole other
> layer of delays to zoned dm-delay devices. Since this isn't really
> useful outside of testing, I think that could be acceptable if necessary
> (it would require us to support table reloads of zoned devices with
> emulated zone append, since tests often want to change the delay).
> However it would probably be better to see if we can just make dm-delay
> preserve write ordering during a suspend.

My use case is all about using zone append, so emulating it would be
a bit counter productive, but I'll give it a spin.  I doubt that this
test is very timing critical.