Re: [PATCH 15/25] memremap: provide an optional internal refcount in struct dev_pagemap

From: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
To: Ira Weiny <ira.weiny-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Cc: linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org,
	linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
	Jason Gunthorpe <jgg-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>,
	Ben Skeggs <bskeggs-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	nouveau-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org,
	Dan Williams
	<dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
	Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
Subject: Re: [PATCH 15/25] memremap: provide an optional internal refcount in struct dev_pagemap
Date: Thu, 27 Jun 2019 10:51:35 +0200	[thread overview]
Message-ID: <20190627085135.GB11420@lst.de> (raw)
In-Reply-To: <20190626214750.GC8399-J5EW/p2F9lUlb2qzJQmr9q2pdiUAq4bhAL8bYrjMMd8@public.gmane.org>

On Wed, Jun 26, 2019 at 02:47:50PM -0700, Ira Weiny wrote:
> > +
> > +		init_completion(&pgmap->done);
> > +		error = percpu_ref_init(&pgmap->internal_ref,
> > +				dev_pagemap_percpu_release, 0, GFP_KERNEL);
> > +		if (error)
> > +			return ERR_PTR(error);
> > +		pgmap->ref = &pgmap->internal_ref;
> > +	} else {
> > +		if (!pgmap->ops || !pgmap->ops->kill || !pgmap->ops->cleanup) {
> > +			WARN(1, "Missing reference count teardown definition\n");
> > +			return ERR_PTR(-EINVAL);
> > +		}
> 
> After this series are there any users who continue to supply their own
> reference object and these callbacks?

Yes, fsdax uses the block layer request_queue reference count.
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