[bug report] device-dax: add dis-contiguous resource support

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Dan Williams,

This is a semi-automatic email about new static checker warnings.

The patch 454c727769f5: "device-dax: add dis-contiguous resource
support" from Aug 26, 2020, leads to the following Smatch complaint:

    drivers/dax/bus.c:788 alloc_dev_dax_range()
    error: we previously assumed 'alloc' could be null (see line 772)

drivers/dax/bus.c
   771		alloc = __request_region(res, start, size, dev_name(dev), 0);
   772		if (!alloc && !dev_dax->nr_range) {
                           ^^
This should probably be a ||?

   773			/*
   774			 * If we adjusted an existing @ranges leave it alone,
   775			 * but if this was an empty set of ranges nothing else
   776			 * will release @ranges, so do it now.
   777			 */
   778			kfree(ranges);
   779			return -ENOMEM;
   780		}
   781	
   782		for (i = 0; i < dev_dax->nr_range; i++)
   783			pgoff += PHYS_PFN(range_len(&ranges[i].range));
   784		dev_dax->ranges = ranges;
   785		ranges[dev_dax->nr_range++] = (struct dev_dax_range) {
   786			.pgoff = pgoff,
   787			.range = {
   788				.start = alloc->start,
                                         ^^^^^^^^^^^^
Dereferences.

   789				.end = alloc->end,
   790			},

regards,
dan carpenter
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