linux-kernel - Re: [PATCH 15/25] memremap: provide an optional internal refcount in struct dev

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Message-ID: <20190627085135.GB11420@lst.de>
Date:   Thu, 27 Jun 2019 10:51:35 +0200
From:   Christoph Hellwig <hch@....de>
To:     Ira Weiny <ira.weiny@...el.com>
Cc:     Christoph Hellwig <hch@....de>,
        Dan Williams <dan.j.williams@...el.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Ben Skeggs <bskeggs@...hat.com>, linux-nvdimm@...ts.01.org,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-mm@...ck.org,
        nouveau@...ts.freedesktop.org
Subject: Re: [PATCH 15/25] memremap: provide an optional internal refcount
 in struct dev_pagemap

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.