linux-kernel - Re: [PATCH 11/25] memremap: lift the devmap_enable manipulation into devm_memremap

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Date:   Thu, 27 Jun 2019 10:50:47 +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 11/25] memremap: lift the devmap_enable manipulation
 into devm_memremap_pages

On Wed, Jun 26, 2019 at 12:04:46PM -0700, Ira Weiny wrote:
> > +static int devmap_managed_enable_get(struct device *dev, struct dev_pagemap *pgmap)
> > +{
> > +	if (!pgmap->ops->page_free) {
> 
> NIT: later on you add the check for pgmap->ops...  it should probably be here.
> 
> But not sure that bisection will be an issue here.

At this point we do not allow a NULL ops pointer.  That only becomes
a valid option one the internal refcount is added.  Until then a NULL
->ops pointer leads to an error return from devm_memremap_pages.