cxl/region: Fix cxl_region leak, cleanup targets at region delete

When a region is deleted any targets that have been previously assigned
to that region hold references to it. Trigger those references to
drop by detaching all targets at unregister_region() time.

Otherwise that region object will leak as userspace has lost the ability
to detach targets once region sysfs is torn down.

Cc: <stable@vger.kernel.org>
Fixes: b9686e8 ("cxl/region: Enable the assignment of endpoint decoders to regions")
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Vishal Verma <vishal.l.verma@intel.com>
Link: https://lore.kernel.org/r/166752183055.947915.17681995648556534844.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Author: djbw

drivers/cxl/core/region.c

@@ -1557,8 +1557,19 @@ static struct cxl_region *to_cxl_region(struct device *dev)
 static void unregister_region(void *dev)
 {
 	struct cxl_region *cxlr = to_cxl_region(dev);
+	struct cxl_region_params *p = &cxlr->params;
+	int i;
 
 	device_del(dev);
+
+	/*
+	 * Now that region sysfs is shutdown, the parameter block is now
+	 * read-only, so no need to hold the region rwsem to access the
+	 * region parameters.
+	 */
+	for (i = 0; i < p->interleave_ways; i++)
+		detach_target(cxlr, i);
+
 	cxl_region_iomem_release(cxlr);
 	put_device(dev);
 }