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Date: Tue, 29 Mar 2022 22:41:04 -0700
From: Christoph Hellwig <hch@infradead.org>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Shiyang Ruan <ruansy.fnst@fujitsu.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-xfs <linux-xfs@vger.kernel.org>,
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	Linux MM <linux-mm@kvack.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	"Darrick J. Wong" <djwong@kernel.org>, david <david@fromorbit.com>,
	Christoph Hellwig <hch@infradead.org>,
	Jane Chu <jane.chu@oracle.com>
Subject: Re: [PATCH v11 1/8] dax: Introduce holder for dax_device
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On Fri, Mar 11, 2022 at 03:35:13PM -0800, Dan Williams wrote:
> > +       if (!dax_dev->holder_ops) {
> > +               rc = -EOPNOTSUPP;
> 
> I think it is ok to return success (0) for this case. All the caller
> of dax_holder_notify_failure() wants to know is if the notification
> was successfully delivered to the holder. If there is no holder
> present then there is nothing to report. This is minor enough for me
> to fix up locally if nothing else needs to be changed.

The caller needs to know there are no holder ops to fall back to
different path.

> Isn't this another failure scenario? If kill_dax() is called while a
> holder is still holding the dax_device that seems to be another
> ->notify_failure scenario to tell the holder that the device is going
> away and the holder has not released the device yet.

Yes.