linux-kernel - RE: [Linux-nvdimm] [PATCH v2 07/20] libnd, nd_dimm: dimm driver and base libnd device-driver infrastructure

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Date:	Wed, 20 May 2015 16:59:04 +0000
From:	"Elliott, Robert (Server Storage)" <Elliott@...com>
To:	Dan Williams <dan.j.williams@...el.com>,
	"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>
CC:	Neil Brown <neilb@...e.de>, Greg KH <gregkh@...uxfoundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [Linux-nvdimm] [PATCH v2 07/20] libnd, nd_dimm: dimm driver and
 base libnd device-driver infrastructure



> -----Original Message-----
> From: Linux-nvdimm [mailto:linux-nvdimm-bounces@...ts.01.org] On Behalf
> Of Dan Williams
> Sent: Tuesday, April 28, 2015 1:25 PM
> To: linux-nvdimm@...ts.01.org
> Cc: Neil Brown; Greg KH; linux-kernel@...r.kernel.org
> Subject: [Linux-nvdimm] [PATCH v2 07/20] libnd, nd_dimm: dimm driver and
> base libnd device-driver infrastructure
> 
...
> diff --git a/drivers/block/nd/dimm.c b/drivers/block/nd/dimm.c
> new file mode 100644
> index 000000000000..a4c8e3ffe97c
> --- /dev/null
> +++ b/drivers/block/nd/dimm.c
> @@ -0,0 +1,93 @@
> +/*
> + * Copyright(c) 2013-2015 Intel Corporation. All rights reserved.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of version 2 of the GNU General Public License as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful, but
> + * WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * General Public License for more details.
> + */
> +#include <linux/vmalloc.h>
> +#include <linux/module.h>
> +#include <linux/device.h>
> +#include <linux/sizes.h>
> +#include <linux/ndctl.h>
> +#include <linux/slab.h>
> +#include <linux/mm.h>
> +#include <linux/nd.h>
> +#include "nd.h"
> +
> +static void free_data(struct nd_dimm_drvdata *ndd)
> +{
> +	if (!ndd)
> +		return;
> +
> +	if (ndd->data && is_vmalloc_addr(ndd->data))
> +		vfree(ndd->data);
> +	else
> +		kfree(ndd->data);
> +	kfree(ndd);
> +}
> +
> +static int nd_dimm_probe(struct device *dev)
> +{
> +	struct nd_dimm_drvdata *ndd;
> +	int rc;
> +
> +	ndd = kzalloc(sizeof(*ndd), GFP_KERNEL);
> +	if (!ndd)
> +		return -ENOMEM;
> +
> +	dev_set_drvdata(dev, ndd);
> +        ndd->dev = dev;
> +
> +	rc = nd_dimm_init_nsarea(ndd);
> +	if (rc)
> +		goto err;
> +
> +	rc = nd_dimm_init_config_data(ndd);
> +	if (rc)
> +		goto err;
> +
> +	dev_dbg(dev, "config data size: %d\n", ndd->nsarea.config_size);
> +
> +	return 0;
> +
> + err:
> +	free_data(ndd);
> +	return rc;
> +
> +}
> +
> +static int nd_dimm_remove(struct device *dev)
> +{
> +	struct nd_dimm_drvdata *ndd = dev_get_drvdata(dev);
> +
> +	free_data(ndd);
> +
> +	return 0;
> +}

It would reduce the slight window for stale pointer usage if you add:
	dev_set_drvdata(dev, NULL);

before
	free_data(ndd);

in both nd_dimm_remove and the err exit for nd_dimm_probe.

The same comment applies to all the drivers that store pointers
with dev_set_drvdata - btt, pmem, etc.


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