// SPDX-License-Identifier: GPL-2.0
  /* Copyright(c) 2016-2019 Intel Corporation. All rights reserved. */
  #include <linux/memremap.h>
  #include <linux/pagemap.h>
  #include <linux/memory.h>
  #include <linux/module.h>
  #include <linux/device.h>
  #include <linux/pfn_t.h>
  #include <linux/slab.h>
  #include <linux/dax.h>
  #include <linux/fs.h>
  #include <linux/mm.h>
  #include <linux/mman.h>
  #include "dax-private.h"
  #include "bus.h"

  /* Memory resource name used for add_memory_driver_managed(). */
  static const char *kmem_name;
  /* Set if any memory will remain added when the driver will be unloaded. */
  static bool any_hotremove_failed;

  static int dax_kmem_range(struct dev_dax *dev_dax, int i, struct range *r)

  {

  	struct dev_dax_range *dax_range = &dev_dax->ranges[i];
  	struct range *range = &dax_range->range;

  
  	/* memory-block align the hotplug range */

  	r->start = ALIGN(range->start, memory_block_size_bytes());
  	r->end = ALIGN_DOWN(range->end + 1, memory_block_size_bytes()) - 1;
  	if (r->start >= r->end) {
  		r->start = range->start;
  		r->end = range->end;
  		return -ENOSPC;
  	}
  	return 0;

  }

  struct dax_kmem_data {
  	const char *res_name;
  	struct resource *res[];
  };

  static int dev_dax_kmem_probe(struct dev_dax *dev_dax)

  {

  	struct device *dev = &dev_dax->dev;

  	struct dax_kmem_data *data;
  	int rc = -ENOMEM;

  	int i, mapped = 0;

  	int numa_node;

  
  	/*
  	 * Ensure good NUMA information for the persistent memory.
  	 * Without this check, there is a risk that slow memory
  	 * could be mixed in a node with faster memory, causing
  	 * unavoidable performance issues.
  	 */
  	numa_node = dev_dax->target_node;
  	if (numa_node < 0) {

  		dev_warn(dev, "rejecting DAX region with invalid node: %d
  ",
  				numa_node);

  		return -EINVAL;
  	}

  	data = kzalloc(sizeof(*data) + sizeof(struct resource *) * dev_dax->nr_range, GFP_KERNEL);
  	if (!data)

  		return -ENOMEM;

  	data->res_name = kstrdup(dev_name(dev), GFP_KERNEL);
  	if (!data->res_name)
  		goto err_res_name;

  	for (i = 0; i < dev_dax->nr_range; i++) {
  		struct resource *res;
  		struct range range;

  		rc = dax_kmem_range(dev_dax, i, &range);
  		if (rc) {
  			dev_info(dev, "mapping%d: %#llx-%#llx too small after alignment
  ",
  					i, range.start, range.end);
  			continue;
  		}

  		/* Region is permanently reserved if hotremove fails. */

  		res = request_mem_region(range.start, range_len(&range), data->res_name);

  		if (!res) {
  			dev_warn(dev, "mapping%d: %#llx-%#llx could not reserve region
  ",
  					i, range.start, range.end);
  			/*
  			 * Once some memory has been onlined we can't
  			 * assume that it can be un-onlined safely.
  			 */
  			if (mapped)
  				continue;

  			rc = -EBUSY;
  			goto err_request_mem;

  		}

  		data->res[i] = res;

  
  		/*
  		 * Set flags appropriate for System RAM.  Leave ..._BUSY clear
  		 * so that add_memory() can add a child resource.  Do not
  		 * inherit flags from the parent since it may set new flags
  		 * unknown to us that will break add_memory() below.
  		 */
  		res->flags = IORESOURCE_SYSTEM_RAM;
  
  		/*
  		 * Ensure that future kexec'd kernels will not treat
  		 * this as RAM automatically.
  		 */
  		rc = add_memory_driver_managed(numa_node, range.start,

  				range_len(&range), kmem_name, MHP_NONE);

  
  		if (rc) {
  			dev_warn(dev, "mapping%d: %#llx-%#llx memory add failed
  ",
  					i, range.start, range.end);

  			release_resource(res);
  			kfree(res);
  			data->res[i] = NULL;

  			if (mapped)
  				continue;

  			goto err_request_mem;

  		}
  		mapped++;

  	}

  	dev_set_drvdata(dev, data);

  
  	return 0;

  
  err_request_mem:
  	kfree(data->res_name);
  err_res_name:
  	kfree(data);
  	return rc;

  }

  #ifdef CONFIG_MEMORY_HOTREMOVE

  static int dev_dax_kmem_remove(struct dev_dax *dev_dax)

  {

  	int i, success = 0;

  	struct device *dev = &dev_dax->dev;

  	struct dax_kmem_data *data = dev_get_drvdata(dev);

  
  	/*
  	 * We have one shot for removing memory, if some memory blocks were not
  	 * offline prior to calling this function remove_memory() will fail, and
  	 * there is no way to hotremove this memory until reboot because device
  	 * unbind will succeed even if we return failure.
  	 */

  	for (i = 0; i < dev_dax->nr_range; i++) {
  		struct range range;
  		int rc;
  
  		rc = dax_kmem_range(dev_dax, i, &range);
  		if (rc)
  			continue;
  
  		rc = remove_memory(dev_dax->target_node, range.start,
  				range_len(&range));
  		if (rc == 0) {

  			release_resource(data->res[i]);
  			kfree(data->res[i]);
  			data->res[i] = NULL;

  			success++;
  			continue;
  		}

  		any_hotremove_failed = true;

  		dev_err(dev,
  			"mapping%d: %#llx-%#llx cannot be hotremoved until the next reboot
  ",
  				i, range.start, range.end);

  	}

  	if (success >= dev_dax->nr_range) {

  		kfree(data->res_name);
  		kfree(data);

  		dev_set_drvdata(dev, NULL);
  	}

  
  	return 0;
  }
  #else

  static int dev_dax_kmem_remove(struct dev_dax *dev_dax)

  {
  	/*

  	 * Without hotremove purposely leak the request_mem_region() for the
  	 * device-dax range and return '0' to ->remove() attempts. The removal
  	 * of the device from the driver always succeeds, but the region is
  	 * permanently pinned as reserved by the unreleased

  	 * request_mem_region().
  	 */

  	any_hotremove_failed = true;

  	return 0;
  }

  #endif /* CONFIG_MEMORY_HOTREMOVE */

  
  static struct dax_device_driver device_dax_kmem_driver = {

  	.probe = dev_dax_kmem_probe,
  	.remove = dev_dax_kmem_remove,

  };
  
  static int __init dax_kmem_init(void)
  {

  	int rc;
  
  	/* Resource name is permanently allocated if any hotremove fails. */
  	kmem_name = kstrdup_const("System RAM (kmem)", GFP_KERNEL);
  	if (!kmem_name)
  		return -ENOMEM;
  
  	rc = dax_driver_register(&device_dax_kmem_driver);
  	if (rc)
  		kfree_const(kmem_name);
  	return rc;

  }
  
  static void __exit dax_kmem_exit(void)
  {
  	dax_driver_unregister(&device_dax_kmem_driver);

  	if (!any_hotremove_failed)
  		kfree_const(kmem_name);

  }
  
  MODULE_AUTHOR("Intel Corporation");
  MODULE_LICENSE("GPL v2");
  module_init(dax_kmem_init);
  module_exit(dax_kmem_exit);
  MODULE_ALIAS_DAX_DEVICE(0);