/*
   * Collaborative memory management interface.
   *
   * Copyright (C) 2008 IBM Corporation
   * Author(s): Brian King (brking@linux.vnet.ibm.com),
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * 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.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   *
   */
  
  #include <linux/ctype.h>
  #include <linux/delay.h>
  #include <linux/errno.h>
  #include <linux/fs.h>
  #include <linux/gfp.h>
  #include <linux/kthread.h>
  #include <linux/module.h>
  #include <linux/oom.h>
  #include <linux/reboot.h>
  #include <linux/sched.h>
  #include <linux/stringify.h>
  #include <linux/swap.h>
  #include <linux/device.h>
  #include <asm/firmware.h>
  #include <asm/hvcall.h>
  #include <asm/mmu.h>
  #include <asm/pgalloc.h>
  #include <asm/uaccess.h>
  #include <linux/memory.h>
  #include <asm/plpar_wrappers.h>
  
  #define CMM_DRIVER_VERSION	"1.0.0"
  #define CMM_DEFAULT_DELAY	1
  #define CMM_HOTPLUG_DELAY	5
  #define CMM_DEBUG			0
  #define CMM_DISABLE		0
  #define CMM_OOM_KB		1024
  #define CMM_MIN_MEM_MB		256
  #define KB2PAGES(_p)		((_p)>>(PAGE_SHIFT-10))
  #define PAGES2KB(_p)		((_p)<<(PAGE_SHIFT-10))
  /*
   * The priority level tries to ensure that this notifier is called as
   * late as possible to reduce thrashing in the shared memory pool.
   */
  #define CMM_MEM_HOTPLUG_PRI	1
  #define CMM_MEM_ISOLATE_PRI	15
  
  static unsigned int delay = CMM_DEFAULT_DELAY;
  static unsigned int hotplug_delay = CMM_HOTPLUG_DELAY;
  static unsigned int oom_kb = CMM_OOM_KB;
  static unsigned int cmm_debug = CMM_DEBUG;
  static unsigned int cmm_disabled = CMM_DISABLE;
  static unsigned long min_mem_mb = CMM_MIN_MEM_MB;
  static struct device cmm_dev;
  
  MODULE_AUTHOR("Brian King <brking@linux.vnet.ibm.com>");
  MODULE_DESCRIPTION("IBM System p Collaborative Memory Manager");
  MODULE_LICENSE("GPL");
  MODULE_VERSION(CMM_DRIVER_VERSION);
  
  module_param_named(delay, delay, uint, S_IRUGO | S_IWUSR);
  MODULE_PARM_DESC(delay, "Delay (in seconds) between polls to query hypervisor paging requests. "
  		 "[Default=" __stringify(CMM_DEFAULT_DELAY) "]");
  module_param_named(hotplug_delay, hotplug_delay, uint, S_IRUGO | S_IWUSR);
  MODULE_PARM_DESC(delay, "Delay (in seconds) after memory hotplug remove "
  		 "before loaning resumes. "
  		 "[Default=" __stringify(CMM_HOTPLUG_DELAY) "]");
  module_param_named(oom_kb, oom_kb, uint, S_IRUGO | S_IWUSR);
  MODULE_PARM_DESC(oom_kb, "Amount of memory in kb to free on OOM. "
  		 "[Default=" __stringify(CMM_OOM_KB) "]");
  module_param_named(min_mem_mb, min_mem_mb, ulong, S_IRUGO | S_IWUSR);
  MODULE_PARM_DESC(min_mem_mb, "Minimum amount of memory (in MB) to not balloon. "
  		 "[Default=" __stringify(CMM_MIN_MEM_MB) "]");
  module_param_named(debug, cmm_debug, uint, S_IRUGO | S_IWUSR);
  MODULE_PARM_DESC(debug, "Enable module debugging logging. Set to 1 to enable. "
  		 "[Default=" __stringify(CMM_DEBUG) "]");
  
  #define CMM_NR_PAGES ((PAGE_SIZE - sizeof(void *) - sizeof(unsigned long)) / sizeof(unsigned long))
  
  #define cmm_dbg(...) if (cmm_debug) { printk(KERN_INFO "cmm: "__VA_ARGS__); }
  
  struct cmm_page_array {
  	struct cmm_page_array *next;
  	unsigned long index;
  	unsigned long page[CMM_NR_PAGES];
  };
  
  static unsigned long loaned_pages;
  static unsigned long loaned_pages_target;
  static unsigned long oom_freed_pages;
  
  static struct cmm_page_array *cmm_page_list;
  static DEFINE_SPINLOCK(cmm_lock);
  
  static DEFINE_MUTEX(hotplug_mutex);
  static int hotplug_occurred; /* protected by the hotplug mutex */
  
  static struct task_struct *cmm_thread_ptr;
  
  /**
   * cmm_alloc_pages - Allocate pages and mark them as loaned
   * @nr:	number of pages to allocate
   *
   * Return value:
   * 	number of pages requested to be allocated which were not
   **/
  static long cmm_alloc_pages(long nr)
  {
  	struct cmm_page_array *pa, *npa;
  	unsigned long addr;
  	long rc;
  
  	cmm_dbg("Begin request for %ld pages
  ", nr);
  
  	while (nr) {
  		/* Exit if a hotplug operation is in progress or occurred */
  		if (mutex_trylock(&hotplug_mutex)) {
  			if (hotplug_occurred) {
  				mutex_unlock(&hotplug_mutex);
  				break;
  			}
  			mutex_unlock(&hotplug_mutex);
  		} else {
  			break;
  		}
  
  		addr = __get_free_page(GFP_NOIO | __GFP_NOWARN |
  				       __GFP_NORETRY | __GFP_NOMEMALLOC);
  		if (!addr)
  			break;
  		spin_lock(&cmm_lock);
  		pa = cmm_page_list;
  		if (!pa || pa->index >= CMM_NR_PAGES) {
  			/* Need a new page for the page list. */
  			spin_unlock(&cmm_lock);
  			npa = (struct cmm_page_array *)__get_free_page(
  					GFP_NOIO | __GFP_NOWARN |
  					__GFP_NORETRY | __GFP_NOMEMALLOC);
  			if (!npa) {
  				pr_info("%s: Can not allocate new page list
  ", __func__);
  				free_page(addr);
  				break;
  			}
  			spin_lock(&cmm_lock);
  			pa = cmm_page_list;
  
  			if (!pa || pa->index >= CMM_NR_PAGES) {
  				npa->next = pa;
  				npa->index = 0;
  				pa = npa;
  				cmm_page_list = pa;
  			} else
  				free_page((unsigned long) npa);
  		}
  
  		if ((rc = plpar_page_set_loaned(__pa(addr)))) {
  			pr_err("%s: Can not set page to loaned. rc=%ld
  ", __func__, rc);
  			spin_unlock(&cmm_lock);
  			free_page(addr);
  			break;
  		}
  
  		pa->page[pa->index++] = addr;
  		loaned_pages++;
  		totalram_pages--;
  		spin_unlock(&cmm_lock);
  		nr--;
  	}
  
  	cmm_dbg("End request with %ld pages unfulfilled
  ", nr);
  	return nr;
  }
  
  /**
   * cmm_free_pages - Free pages and mark them as active
   * @nr:	number of pages to free
   *
   * Return value:
   * 	number of pages requested to be freed which were not
   **/
  static long cmm_free_pages(long nr)
  {
  	struct cmm_page_array *pa;
  	unsigned long addr;
  
  	cmm_dbg("Begin free of %ld pages.
  ", nr);
  	spin_lock(&cmm_lock);
  	pa = cmm_page_list;
  	while (nr) {
  		if (!pa || pa->index <= 0)
  			break;
  		addr = pa->page[--pa->index];
  
  		if (pa->index == 0) {
  			pa = pa->next;
  			free_page((unsigned long) cmm_page_list);
  			cmm_page_list = pa;
  		}
  
  		plpar_page_set_active(__pa(addr));
  		free_page(addr);
  		loaned_pages--;
  		nr--;
  		totalram_pages++;
  	}
  	spin_unlock(&cmm_lock);
  	cmm_dbg("End request with %ld pages unfulfilled
  ", nr);
  	return nr;
  }
  
  /**
   * cmm_oom_notify - OOM notifier
   * @self:	notifier block struct
   * @dummy:	not used
   * @parm:	returned - number of pages freed
   *
   * Return value:
   * 	NOTIFY_OK
   **/
  static int cmm_oom_notify(struct notifier_block *self,
  			  unsigned long dummy, void *parm)
  {
  	unsigned long *freed = parm;
  	long nr = KB2PAGES(oom_kb);
  
  	cmm_dbg("OOM processing started
  ");
  	nr = cmm_free_pages(nr);
  	loaned_pages_target = loaned_pages;
  	*freed += KB2PAGES(oom_kb) - nr;
  	oom_freed_pages += KB2PAGES(oom_kb) - nr;
  	cmm_dbg("OOM processing complete
  ");
  	return NOTIFY_OK;
  }
  
  /**
   * cmm_get_mpp - Read memory performance parameters
   *
   * Makes hcall to query the current page loan request from the hypervisor.
   *
   * Return value:
   * 	nothing
   **/
  static void cmm_get_mpp(void)
  {
  	int rc;
  	struct hvcall_mpp_data mpp_data;
  	signed long active_pages_target, page_loan_request, target;
  	signed long total_pages = totalram_pages + loaned_pages;
  	signed long min_mem_pages = (min_mem_mb * 1024 * 1024) / PAGE_SIZE;
  
  	rc = h_get_mpp(&mpp_data);
  
  	if (rc != H_SUCCESS)
  		return;
  
  	page_loan_request = div_s64((s64)mpp_data.loan_request, PAGE_SIZE);
  	target = page_loan_request + (signed long)loaned_pages;
  
  	if (target < 0 || total_pages < min_mem_pages)
  		target = 0;
  
  	if (target > oom_freed_pages)
  		target -= oom_freed_pages;
  	else
  		target = 0;
  
  	active_pages_target = total_pages - target;
  
  	if (min_mem_pages > active_pages_target)
  		target = total_pages - min_mem_pages;
  
  	if (target < 0)
  		target = 0;
  
  	loaned_pages_target = target;
  
  	cmm_dbg("delta = %ld, loaned = %lu, target = %lu, oom = %lu, totalram = %lu
  ",
  		page_loan_request, loaned_pages, loaned_pages_target,
  		oom_freed_pages, totalram_pages);
  }
  
  static struct notifier_block cmm_oom_nb = {
  	.notifier_call = cmm_oom_notify
  };
  
  /**
   * cmm_thread - CMM task thread
   * @dummy:	not used
   *
   * Return value:
   * 	0
   **/
  static int cmm_thread(void *dummy)
  {
  	unsigned long timeleft;
  
  	while (1) {
  		timeleft = msleep_interruptible(delay * 1000);
  
  		if (kthread_should_stop() || timeleft)
  			break;
  
  		if (mutex_trylock(&hotplug_mutex)) {
  			if (hotplug_occurred) {
  				hotplug_occurred = 0;
  				mutex_unlock(&hotplug_mutex);
  				cmm_dbg("Hotplug operation has occurred, "
  						"loaning activity suspended "
  						"for %d seconds.
  ",
  						hotplug_delay);
  				timeleft = msleep_interruptible(hotplug_delay *
  						1000);
  				if (kthread_should_stop() || timeleft)
  					break;
  				continue;
  			}
  			mutex_unlock(&hotplug_mutex);
  		} else {
  			cmm_dbg("Hotplug operation in progress, activity "
  					"suspended
  ");
  			continue;
  		}
  
  		cmm_get_mpp();
  
  		if (loaned_pages_target > loaned_pages) {
  			if (cmm_alloc_pages(loaned_pages_target - loaned_pages))
  				loaned_pages_target = loaned_pages;
  		} else if (loaned_pages_target < loaned_pages)
  			cmm_free_pages(loaned_pages - loaned_pages_target);
  	}
  	return 0;
  }
  
  #define CMM_SHOW(name, format, args...)			\
  	static ssize_t show_##name(struct device *dev,	\
  				   struct device_attribute *attr,	\
  				   char *buf)			\
  	{							\
  		return sprintf(buf, format, ##args);		\
  	}							\
  	static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
  
  CMM_SHOW(loaned_kb, "%lu
  ", PAGES2KB(loaned_pages));
  CMM_SHOW(loaned_target_kb, "%lu
  ", PAGES2KB(loaned_pages_target));
  
  static ssize_t show_oom_pages(struct device *dev,
  			      struct device_attribute *attr, char *buf)
  {
  	return sprintf(buf, "%lu
  ", PAGES2KB(oom_freed_pages));
  }
  
  static ssize_t store_oom_pages(struct device *dev,
  			       struct device_attribute *attr,
  			       const char *buf, size_t count)
  {
  	unsigned long val = simple_strtoul (buf, NULL, 10);
  
  	if (!capable(CAP_SYS_ADMIN))
  		return -EPERM;
  	if (val != 0)
  		return -EBADMSG;
  
  	oom_freed_pages = 0;
  	return count;
  }
  
  static DEVICE_ATTR(oom_freed_kb, S_IWUSR | S_IRUGO,
  		   show_oom_pages, store_oom_pages);
  
  static struct device_attribute *cmm_attrs[] = {
  	&dev_attr_loaned_kb,
  	&dev_attr_loaned_target_kb,
  	&dev_attr_oom_freed_kb,
  };
  
  static struct bus_type cmm_subsys = {
  	.name = "cmm",
  	.dev_name = "cmm",
  };
  
  /**
   * cmm_sysfs_register - Register with sysfs
   *
   * Return value:
   * 	0 on success / other on failure
   **/
  static int cmm_sysfs_register(struct device *dev)
  {
  	int i, rc;
  
  	if ((rc = subsys_system_register(&cmm_subsys, NULL)))
  		return rc;
  
  	dev->id = 0;
  	dev->bus = &cmm_subsys;
  
  	if ((rc = device_register(dev)))
  		goto subsys_unregister;
  
  	for (i = 0; i < ARRAY_SIZE(cmm_attrs); i++) {
  		if ((rc = device_create_file(dev, cmm_attrs[i])))
  			goto fail;
  	}
  
  	return 0;
  
  fail:
  	while (--i >= 0)
  		device_remove_file(dev, cmm_attrs[i]);
  	device_unregister(dev);
  subsys_unregister:
  	bus_unregister(&cmm_subsys);
  	return rc;
  }
  
  /**
   * cmm_unregister_sysfs - Unregister from sysfs
   *
   **/
  static void cmm_unregister_sysfs(struct device *dev)
  {
  	int i;
  
  	for (i = 0; i < ARRAY_SIZE(cmm_attrs); i++)
  		device_remove_file(dev, cmm_attrs[i]);
  	device_unregister(dev);
  	bus_unregister(&cmm_subsys);
  }
  
  /**
   * cmm_reboot_notifier - Make sure pages are not still marked as "loaned"
   *
   **/
  static int cmm_reboot_notifier(struct notifier_block *nb,
  			       unsigned long action, void *unused)
  {
  	if (action == SYS_RESTART) {
  		if (cmm_thread_ptr)
  			kthread_stop(cmm_thread_ptr);
  		cmm_thread_ptr = NULL;
  		cmm_free_pages(loaned_pages);
  	}
  	return NOTIFY_DONE;
  }
  
  static struct notifier_block cmm_reboot_nb = {
  	.notifier_call = cmm_reboot_notifier,
  };
  
  /**
   * cmm_count_pages - Count the number of pages loaned in a particular range.
   *
   * @arg: memory_isolate_notify structure with address range and count
   *
   * Return value:
   *      0 on success
   **/
  static unsigned long cmm_count_pages(void *arg)
  {
  	struct memory_isolate_notify *marg = arg;
  	struct cmm_page_array *pa;
  	unsigned long start = (unsigned long)pfn_to_kaddr(marg->start_pfn);
  	unsigned long end = start + (marg->nr_pages << PAGE_SHIFT);
  	unsigned long idx;
  
  	spin_lock(&cmm_lock);
  	pa = cmm_page_list;
  	while (pa) {
  		if ((unsigned long)pa >= start && (unsigned long)pa < end)
  			marg->pages_found++;
  		for (idx = 0; idx < pa->index; idx++)
  			if (pa->page[idx] >= start && pa->page[idx] < end)
  				marg->pages_found++;
  		pa = pa->next;
  	}
  	spin_unlock(&cmm_lock);
  	return 0;
  }
  
  /**
   * cmm_memory_isolate_cb - Handle memory isolation notifier calls
   * @self:	notifier block struct
   * @action:	action to take
   * @arg:	struct memory_isolate_notify data for handler
   *
   * Return value:
   *	NOTIFY_OK or notifier error based on subfunction return value
   **/
  static int cmm_memory_isolate_cb(struct notifier_block *self,
  				 unsigned long action, void *arg)
  {
  	int ret = 0;
  
  	if (action == MEM_ISOLATE_COUNT)
  		ret = cmm_count_pages(arg);
  
  	return notifier_from_errno(ret);
  }
  
  static struct notifier_block cmm_mem_isolate_nb = {
  	.notifier_call = cmm_memory_isolate_cb,
  	.priority = CMM_MEM_ISOLATE_PRI
  };
  
  /**
   * cmm_mem_going_offline - Unloan pages where memory is to be removed
   * @arg: memory_notify structure with page range to be offlined
   *
   * Return value:
   *	0 on success
   **/
  static int cmm_mem_going_offline(void *arg)
  {
  	struct memory_notify *marg = arg;
  	unsigned long start_page = (unsigned long)pfn_to_kaddr(marg->start_pfn);
  	unsigned long end_page = start_page + (marg->nr_pages << PAGE_SHIFT);
  	struct cmm_page_array *pa_curr, *pa_last, *npa;
  	unsigned long idx;
  	unsigned long freed = 0;
  
  	cmm_dbg("Memory going offline, searching 0x%lx (%ld pages).
  ",
  			start_page, marg->nr_pages);
  	spin_lock(&cmm_lock);
  
  	/* Search the page list for pages in the range to be offlined */
  	pa_last = pa_curr = cmm_page_list;
  	while (pa_curr) {
  		for (idx = (pa_curr->index - 1); (idx + 1) > 0; idx--) {
  			if ((pa_curr->page[idx] < start_page) ||
  			    (pa_curr->page[idx] >= end_page))
  				continue;
  
  			plpar_page_set_active(__pa(pa_curr->page[idx]));
  			free_page(pa_curr->page[idx]);
  			freed++;
  			loaned_pages--;
  			totalram_pages++;
  			pa_curr->page[idx] = pa_last->page[--pa_last->index];
  			if (pa_last->index == 0) {
  				if (pa_curr == pa_last)
  					pa_curr = pa_last->next;
  				pa_last = pa_last->next;
  				free_page((unsigned long)cmm_page_list);
  				cmm_page_list = pa_last;
  			}
  		}
  		pa_curr = pa_curr->next;
  	}
  
  	/* Search for page list structures in the range to be offlined */
  	pa_last = NULL;
  	pa_curr = cmm_page_list;
  	while (pa_curr) {
  		if (((unsigned long)pa_curr >= start_page) &&
  				((unsigned long)pa_curr < end_page)) {
  			npa = (struct cmm_page_array *)__get_free_page(
  					GFP_NOIO | __GFP_NOWARN |
  					__GFP_NORETRY | __GFP_NOMEMALLOC);
  			if (!npa) {
  				spin_unlock(&cmm_lock);
  				cmm_dbg("Failed to allocate memory for list "
  						"management. Memory hotplug "
  						"failed.
  ");
  				return ENOMEM;
  			}
  			memcpy(npa, pa_curr, PAGE_SIZE);
  			if (pa_curr == cmm_page_list)
  				cmm_page_list = npa;
  			if (pa_last)
  				pa_last->next = npa;
  			free_page((unsigned long) pa_curr);
  			freed++;
  			pa_curr = npa;
  		}
  
  		pa_last = pa_curr;
  		pa_curr = pa_curr->next;
  	}
  
  	spin_unlock(&cmm_lock);
  	cmm_dbg("Released %ld pages in the search range.
  ", freed);
  
  	return 0;
  }
  
  /**
   * cmm_memory_cb - Handle memory hotplug notifier calls
   * @self:	notifier block struct
   * @action:	action to take
   * @arg:	struct memory_notify data for handler
   *
   * Return value:
   *	NOTIFY_OK or notifier error based on subfunction return value
   *
   **/
  static int cmm_memory_cb(struct notifier_block *self,
  			unsigned long action, void *arg)
  {
  	int ret = 0;
  
  	switch (action) {
  	case MEM_GOING_OFFLINE:
  		mutex_lock(&hotplug_mutex);
  		hotplug_occurred = 1;
  		ret = cmm_mem_going_offline(arg);
  		break;
  	case MEM_OFFLINE:
  	case MEM_CANCEL_OFFLINE:
  		mutex_unlock(&hotplug_mutex);
  		cmm_dbg("Memory offline operation complete.
  ");
  		break;
  	case MEM_GOING_ONLINE:
  	case MEM_ONLINE:
  	case MEM_CANCEL_ONLINE:
  		break;
  	}
  
  	return notifier_from_errno(ret);
  }
  
  static struct notifier_block cmm_mem_nb = {
  	.notifier_call = cmm_memory_cb,
  	.priority = CMM_MEM_HOTPLUG_PRI
  };
  
  /**
   * cmm_init - Module initialization
   *
   * Return value:
   * 	0 on success / other on failure
   **/
  static int cmm_init(void)
  {
  	int rc = -ENOMEM;
  
  	if (!firmware_has_feature(FW_FEATURE_CMO))
  		return -EOPNOTSUPP;
  
  	if ((rc = register_oom_notifier(&cmm_oom_nb)) < 0)
  		return rc;
  
  	if ((rc = register_reboot_notifier(&cmm_reboot_nb)))
  		goto out_oom_notifier;
  
  	if ((rc = cmm_sysfs_register(&cmm_dev)))
  		goto out_reboot_notifier;
  
  	if (register_memory_notifier(&cmm_mem_nb) ||
  	    register_memory_isolate_notifier(&cmm_mem_isolate_nb))
  		goto out_unregister_notifier;
  
  	if (cmm_disabled)
  		return rc;
  
  	cmm_thread_ptr = kthread_run(cmm_thread, NULL, "cmmthread");
  	if (IS_ERR(cmm_thread_ptr)) {
  		rc = PTR_ERR(cmm_thread_ptr);
  		goto out_unregister_notifier;
  	}
  
  	return rc;
  
  out_unregister_notifier:
  	unregister_memory_notifier(&cmm_mem_nb);
  	unregister_memory_isolate_notifier(&cmm_mem_isolate_nb);
  	cmm_unregister_sysfs(&cmm_dev);
  out_reboot_notifier:
  	unregister_reboot_notifier(&cmm_reboot_nb);
  out_oom_notifier:
  	unregister_oom_notifier(&cmm_oom_nb);
  	return rc;
  }
  
  /**
   * cmm_exit - Module exit
   *
   * Return value:
   * 	nothing
   **/
  static void cmm_exit(void)
  {
  	if (cmm_thread_ptr)
  		kthread_stop(cmm_thread_ptr);
  	unregister_oom_notifier(&cmm_oom_nb);
  	unregister_reboot_notifier(&cmm_reboot_nb);
  	unregister_memory_notifier(&cmm_mem_nb);
  	unregister_memory_isolate_notifier(&cmm_mem_isolate_nb);
  	cmm_free_pages(loaned_pages);
  	cmm_unregister_sysfs(&cmm_dev);
  }
  
  /**
   * cmm_set_disable - Disable/Enable CMM
   *
   * Return value:
   * 	0 on success / other on failure
   **/
  static int cmm_set_disable(const char *val, struct kernel_param *kp)
  {
  	int disable = simple_strtoul(val, NULL, 10);
  
  	if (disable != 0 && disable != 1)
  		return -EINVAL;
  
  	if (disable && !cmm_disabled) {
  		if (cmm_thread_ptr)
  			kthread_stop(cmm_thread_ptr);
  		cmm_thread_ptr = NULL;
  		cmm_free_pages(loaned_pages);
  	} else if (!disable && cmm_disabled) {
  		cmm_thread_ptr = kthread_run(cmm_thread, NULL, "cmmthread");
  		if (IS_ERR(cmm_thread_ptr))
  			return PTR_ERR(cmm_thread_ptr);
  	}
  
  	cmm_disabled = disable;
  	return 0;
  }
  
  module_param_call(disable, cmm_set_disable, param_get_uint,
  		  &cmm_disabled, S_IRUGO | S_IWUSR);
  MODULE_PARM_DESC(disable, "Disable CMM. Set to 1 to disable. "
  		 "[Default=" __stringify(CMM_DISABLE) "]");
  
  module_init(cmm_init);
  module_exit(cmm_exit);