arch/powerpc/platforms/pseries/cmm.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Collaborative memory management interface.
   4  *
   5  * Copyright (C) 2008 IBM Corporation
   6  * Author(s): Brian King (brking@linux.vnet.ibm.com),
   7  */
   8
   9 #include <linux/ctype.h>
  10 #include <linux/delay.h>
  11 #include <linux/errno.h>
  12 #include <linux/fs.h>
  13 #include <linux/gfp.h>
  14 #include <linux/kthread.h>
  15 #include <linux/module.h>
  16 #include <linux/oom.h>
  17 #include <linux/reboot.h>
  18 #include <linux/sched.h>
  19 #include <linux/stringify.h>
  20 #include <linux/swap.h>
  21 #include <linux/device.h>
  22 #include <linux/mount.h>
  23 #include <linux/pseudo_fs.h>
  24 #include <linux/magic.h>
  25 #include <linux/balloon_compaction.h>
  26 #include <asm/firmware.h>
  27 #include <asm/hvcall.h>
  28 #include <asm/mmu.h>
  29 #include <asm/pgalloc.h>
  30 #include <linux/uaccess.h>
  31 #include <linux/memory.h>
  32 #include <asm/plpar_wrappers.h>
  33
  34 #include "pseries.h"
  35
  36 #define CMM_DRIVER_VERSION      "1.0.0"
  37 #define CMM_DEFAULT_DELAY       1
  38 #define CMM_HOTPLUG_DELAY       5
  39 #define CMM_DEBUG                       0
  40 #define CMM_DISABLE             0
  41 #define CMM_OOM_KB              1024
  42 #define CMM_MIN_MEM_MB          256
  43 #define KB2PAGES(_p)            ((_p)>>(PAGE_SHIFT-10))
  44 #define PAGES2KB(_p)            ((_p)<<(PAGE_SHIFT-10))
  45
  46 #define CMM_MEM_HOTPLUG_PRI     1
  47
  48 static unsigned int delay = CMM_DEFAULT_DELAY;
  49 static unsigned int hotplug_delay = CMM_HOTPLUG_DELAY;
  50 static unsigned int oom_kb = CMM_OOM_KB;
  51 static unsigned int cmm_debug = CMM_DEBUG;
  52 static unsigned int cmm_disabled = CMM_DISABLE;
  53 static unsigned long min_mem_mb = CMM_MIN_MEM_MB;
  54 static struct device cmm_dev;
  55
  56 MODULE_AUTHOR("Brian King <brking@linux.vnet.ibm.com>");
  57 MODULE_DESCRIPTION("IBM System p Collaborative Memory Manager");
  58 MODULE_LICENSE("GPL");
  59 MODULE_VERSION(CMM_DRIVER_VERSION);
  60
  61 module_param_named(delay, delay, uint, 0644);
  62 MODULE_PARM_DESC(delay, "Delay (in seconds) between polls to query hypervisor paging requests. "
  63                  "[Default=" __stringify(CMM_DEFAULT_DELAY) "]");
  64 module_param_named(hotplug_delay, hotplug_delay, uint, 0644);
  65 MODULE_PARM_DESC(hotplug_delay, "Delay (in seconds) after memory hotplug remove "
  66                  "before loaning resumes. "
  67                  "[Default=" __stringify(CMM_HOTPLUG_DELAY) "]");
  68 module_param_named(oom_kb, oom_kb, uint, 0644);
  69 MODULE_PARM_DESC(oom_kb, "Amount of memory in kb to free on OOM. "
  70                  "[Default=" __stringify(CMM_OOM_KB) "]");
  71 module_param_named(min_mem_mb, min_mem_mb, ulong, 0644);
  72 MODULE_PARM_DESC(min_mem_mb, "Minimum amount of memory (in MB) to not balloon. "
  73                  "[Default=" __stringify(CMM_MIN_MEM_MB) "]");
  74 module_param_named(debug, cmm_debug, uint, 0644);
  75 MODULE_PARM_DESC(debug, "Enable module debugging logging. Set to 1 to enable. "
  76                  "[Default=" __stringify(CMM_DEBUG) "]");
  77
  78 #define cmm_dbg(...) if (cmm_debug) { printk(KERN_INFO "cmm: "__VA_ARGS__); }
  79
  80 static atomic_long_t loaned_pages;
  81 static unsigned long loaned_pages_target;
  82 static unsigned long oom_freed_pages;
  83
  84 static DEFINE_MUTEX(hotplug_mutex);
  85 static int hotplug_occurred; /* protected by the hotplug mutex */
  86
  87 static struct task_struct *cmm_thread_ptr;
  88 static struct balloon_dev_info b_dev_info;
  89
  90 static long plpar_page_set_loaned(struct page *page)
  91 {
  92         const unsigned long vpa = page_to_phys(page);
  93         unsigned long cmo_page_sz = cmo_get_page_size();
  94         long rc = 0;
  95         int i;
  96
  97         for (i = 0; !rc && i < PAGE_SIZE; i += cmo_page_sz)
  98                 rc = plpar_hcall_norets(H_PAGE_INIT, H_PAGE_SET_LOANED, vpa + i, 0);
  99
 100         for (i -= cmo_page_sz; rc && i != 0; i -= cmo_page_sz)
 101                 plpar_hcall_norets(H_PAGE_INIT, H_PAGE_SET_ACTIVE,
 102                                    vpa + i - cmo_page_sz, 0);
 103
 104         return rc;
 105 }
 106
 107 static long plpar_page_set_active(struct page *page)
 108 {
 109         const unsigned long vpa = page_to_phys(page);
 110         unsigned long cmo_page_sz = cmo_get_page_size();
 111         long rc = 0;
 112         int i;
 113
 114         for (i = 0; !rc && i < PAGE_SIZE; i += cmo_page_sz)
 115                 rc = plpar_hcall_norets(H_PAGE_INIT, H_PAGE_SET_ACTIVE, vpa + i, 0);
 116
 117         for (i -= cmo_page_sz; rc && i != 0; i -= cmo_page_sz)
 118                 plpar_hcall_norets(H_PAGE_INIT, H_PAGE_SET_LOANED,
 119                                    vpa + i - cmo_page_sz, 0);
 120
 121         return rc;
 122 }
 123
 124 /**
 125  * cmm_alloc_pages - Allocate pages and mark them as loaned
 126  * @nr: number of pages to allocate
 127  *
 128  * Return value:
 129  *      number of pages requested to be allocated which were not
 130  **/
 131 static long cmm_alloc_pages(long nr)
 132 {
 133         struct page *page;
 134         long rc;
 135
 136         cmm_dbg("Begin request for %ld pages\n", nr);
 137
 138         while (nr) {
 139                 /* Exit if a hotplug operation is in progress or occurred */
 140                 if (mutex_trylock(&hotplug_mutex)) {
 141                         if (hotplug_occurred) {
 142                                 mutex_unlock(&hotplug_mutex);
 143                                 break;
 144                         }
 145                         mutex_unlock(&hotplug_mutex);
 146                 } else {
 147                         break;
 148                 }
 149
 150                 page = alloc_page(GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY |
 151                                   __GFP_NOMEMALLOC);
 152                 if (!page)
 153                         break;
 154                 rc = plpar_page_set_loaned(page);
 155                 if (rc) {
 156                         pr_err("%s: Can not set page to loaned. rc=%ld\n", __func__, rc);
 157                         __free_page(page);
 158                         break;
 159                 }
 160
 161                 balloon_page_enqueue(&b_dev_info, page);
 162                 atomic_long_inc(&loaned_pages);
 163                 adjust_managed_page_count(page, -1);
 164                 nr--;
 165         }
 166
 167         cmm_dbg("End request with %ld pages unfulfilled\n", nr);
 168         return nr;
 169 }
 170
 171 /**
 172  * cmm_free_pages - Free pages and mark them as active
 173  * @nr: number of pages to free
 174  *
 175  * Return value:
 176  *      number of pages requested to be freed which were not
 177  **/
 178 static long cmm_free_pages(long nr)
 179 {
 180         struct page *page;
 181
 182         cmm_dbg("Begin free of %ld pages.\n", nr);
 183         while (nr) {
 184                 page = balloon_page_dequeue(&b_dev_info);
 185                 if (!page)
 186                         break;
 187                 plpar_page_set_active(page);
 188                 adjust_managed_page_count(page, 1);
 189                 __free_page(page);
 190                 atomic_long_dec(&loaned_pages);
 191                 nr--;
 192         }
 193         cmm_dbg("End request with %ld pages unfulfilled\n", nr);
 194         return nr;
 195 }
 196
 197 /**
 198  * cmm_oom_notify - OOM notifier
 199  * @self:       notifier block struct
 200  * @dummy:      not used
 201  * @parm:       returned - number of pages freed
 202  *
 203  * Return value:
 204  *      NOTIFY_OK
 205  **/
 206 static int cmm_oom_notify(struct notifier_block *self,
 207                           unsigned long dummy, void *parm)
 208 {
 209         unsigned long *freed = parm;
 210         long nr = KB2PAGES(oom_kb);
 211
 212         cmm_dbg("OOM processing started\n");
 213         nr = cmm_free_pages(nr);
 214         loaned_pages_target = atomic_long_read(&loaned_pages);
 215         *freed += KB2PAGES(oom_kb) - nr;
 216         oom_freed_pages += KB2PAGES(oom_kb) - nr;
 217         cmm_dbg("OOM processing complete\n");
 218         return NOTIFY_OK;
 219 }
 220
 221 /**
 222  * cmm_get_mpp - Read memory performance parameters
 223  *
 224  * Makes hcall to query the current page loan request from the hypervisor.
 225  *
 226  * Return value:
 227  *      nothing
 228  **/
 229 static void cmm_get_mpp(void)
 230 {
 231         const long __loaned_pages = atomic_long_read(&loaned_pages);
 232         const long total_pages = totalram_pages() + __loaned_pages;
 233         int rc;
 234         struct hvcall_mpp_data mpp_data;
 235         signed long active_pages_target, page_loan_request, target;
 236         signed long min_mem_pages = (min_mem_mb * 1024 * 1024) / PAGE_SIZE;
 237
 238         rc = h_get_mpp(&mpp_data);
 239
 240         if (rc != H_SUCCESS)
 241                 return;
 242
 243         page_loan_request = div_s64((s64)mpp_data.loan_request, PAGE_SIZE);
 244         target = page_loan_request + __loaned_pages;
 245
 246         if (target < 0 || total_pages < min_mem_pages)
 247                 target = 0;
 248
 249         if (target > oom_freed_pages)
 250                 target -= oom_freed_pages;
 251         else
 252                 target = 0;
 253
 254         active_pages_target = total_pages - target;
 255
 256         if (min_mem_pages > active_pages_target)
 257                 target = total_pages - min_mem_pages;
 258
 259         if (target < 0)
 260                 target = 0;
 261
 262         loaned_pages_target = target;
 263
 264         cmm_dbg("delta = %ld, loaned = %lu, target = %lu, oom = %lu, totalram = %lu\n",
 265                 page_loan_request, __loaned_pages, loaned_pages_target,
 266                 oom_freed_pages, totalram_pages());
 267 }
 268
 269 static struct notifier_block cmm_oom_nb = {
 270         .notifier_call = cmm_oom_notify
 271 };
 272
 273 /**
 274  * cmm_thread - CMM task thread
 275  * @dummy:      not used
 276  *
 277  * Return value:
 278  *      0
 279  **/
 280 static int cmm_thread(void *dummy)
 281 {
 282         unsigned long timeleft;
 283         long __loaned_pages;
 284
 285         while (1) {
 286                 timeleft = msleep_interruptible(delay * 1000);
 287
 288                 if (kthread_should_stop() || timeleft)
 289                         break;
 290
 291                 if (mutex_trylock(&hotplug_mutex)) {
 292                         if (hotplug_occurred) {
 293                                 hotplug_occurred = 0;
 294                                 mutex_unlock(&hotplug_mutex);
 295                                 cmm_dbg("Hotplug operation has occurred, "
 296                                                 "loaning activity suspended "
 297                                                 "for %d seconds.\n",
 298                                                 hotplug_delay);
 299                                 timeleft = msleep_interruptible(hotplug_delay *
 300                                                 1000);
 301                                 if (kthread_should_stop() || timeleft)
 302                                         break;
 303                                 continue;
 304                         }
 305                         mutex_unlock(&hotplug_mutex);
 306                 } else {
 307                         cmm_dbg("Hotplug operation in progress, activity "
 308                                         "suspended\n");
 309                         continue;
 310                 }
 311
 312                 cmm_get_mpp();
 313
 314                 __loaned_pages = atomic_long_read(&loaned_pages);
 315                 if (loaned_pages_target > __loaned_pages) {
 316                         if (cmm_alloc_pages(loaned_pages_target - __loaned_pages))
 317                                 loaned_pages_target = __loaned_pages;
 318                 } else if (loaned_pages_target < __loaned_pages)
 319                         cmm_free_pages(__loaned_pages - loaned_pages_target);
 320         }
 321         return 0;
 322 }
 323
 324 #define CMM_SHOW(name, format, args...)                 \
 325         static ssize_t show_##name(struct device *dev,  \
 326                                    struct device_attribute *attr,       \
 327                                    char *buf)                   \
 328         {                                                       \
 329                 return sprintf(buf, format, ##args);            \
 330         }                                                       \
 331         static DEVICE_ATTR(name, 0444, show_##name, NULL)
 332
 333 CMM_SHOW(loaned_kb, "%lu\n", PAGES2KB(atomic_long_read(&loaned_pages)));
 334 CMM_SHOW(loaned_target_kb, "%lu\n", PAGES2KB(loaned_pages_target));
 335
 336 static ssize_t show_oom_pages(struct device *dev,
 337                               struct device_attribute *attr, char *buf)
 338 {
 339         return sprintf(buf, "%lu\n", PAGES2KB(oom_freed_pages));
 340 }
 341
 342 static ssize_t store_oom_pages(struct device *dev,
 343                                struct device_attribute *attr,
 344                                const char *buf, size_t count)
 345 {
 346         unsigned long val = simple_strtoul (buf, NULL, 10);
 347
 348         if (!capable(CAP_SYS_ADMIN))
 349                 return -EPERM;
 350         if (val != 0)
 351                 return -EBADMSG;
 352
 353         oom_freed_pages = 0;
 354         return count;
 355 }
 356
 357 static DEVICE_ATTR(oom_freed_kb, 0644,
 358                    show_oom_pages, store_oom_pages);
 359
 360 static struct device_attribute *cmm_attrs[] = {
 361         &dev_attr_loaned_kb,
 362         &dev_attr_loaned_target_kb,
 363         &dev_attr_oom_freed_kb,
 364 };
 365
 366 static struct bus_type cmm_subsys = {
 367         .name = "cmm",
 368         .dev_name = "cmm",
 369 };
 370
 371 static void cmm_release_device(struct device *dev)
 372 {
 373 }
 374
 375 /**
 376  * cmm_sysfs_register - Register with sysfs
 377  *
 378  * Return value:
 379  *      0 on success / other on failure
 380  **/
 381 static int cmm_sysfs_register(struct device *dev)
 382 {
 383         int i, rc;
 384
 385         if ((rc = subsys_system_register(&cmm_subsys, NULL)))
 386                 return rc;
 387
 388         dev->id = 0;
 389         dev->bus = &cmm_subsys;
 390         dev->release = cmm_release_device;
 391
 392         if ((rc = device_register(dev)))
 393                 goto subsys_unregister;
 394
 395         for (i = 0; i < ARRAY_SIZE(cmm_attrs); i++) {
 396                 if ((rc = device_create_file(dev, cmm_attrs[i])))
 397                         goto fail;
 398         }
 399
 400         return 0;
 401
 402 fail:
 403         while (--i >= 0)
 404                 device_remove_file(dev, cmm_attrs[i]);
 405         device_unregister(dev);
 406 subsys_unregister:
 407         bus_unregister(&cmm_subsys);
 408         return rc;
 409 }
 410
 411 /**
 412  * cmm_unregister_sysfs - Unregister from sysfs
 413  *
 414  **/
 415 static void cmm_unregister_sysfs(struct device *dev)
 416 {
 417         int i;
 418
 419         for (i = 0; i < ARRAY_SIZE(cmm_attrs); i++)
 420                 device_remove_file(dev, cmm_attrs[i]);
 421         device_unregister(dev);
 422         bus_unregister(&cmm_subsys);
 423 }
 424
 425 /**
 426  * cmm_reboot_notifier - Make sure pages are not still marked as "loaned"
 427  *
 428  **/
 429 static int cmm_reboot_notifier(struct notifier_block *nb,
 430                                unsigned long action, void *unused)
 431 {
 432         if (action == SYS_RESTART) {
 433                 if (cmm_thread_ptr)
 434                         kthread_stop(cmm_thread_ptr);
 435                 cmm_thread_ptr = NULL;
 436                 cmm_free_pages(atomic_long_read(&loaned_pages));
 437         }
 438         return NOTIFY_DONE;
 439 }
 440
 441 static struct notifier_block cmm_reboot_nb = {
 442         .notifier_call = cmm_reboot_notifier,
 443 };
 444
 445 /**
 446  * cmm_memory_cb - Handle memory hotplug notifier calls
 447  * @self:       notifier block struct
 448  * @action:     action to take
 449  * @arg:        struct memory_notify data for handler
 450  *
 451  * Return value:
 452  *      NOTIFY_OK or notifier error based on subfunction return value
 453  *
 454  **/
 455 static int cmm_memory_cb(struct notifier_block *self,
 456                         unsigned long action, void *arg)
 457 {
 458         int ret = 0;
 459
 460         switch (action) {
 461         case MEM_GOING_OFFLINE:
 462                 mutex_lock(&hotplug_mutex);
 463                 hotplug_occurred = 1;
 464                 break;
 465         case MEM_OFFLINE:
 466         case MEM_CANCEL_OFFLINE:
 467                 mutex_unlock(&hotplug_mutex);
 468                 cmm_dbg("Memory offline operation complete.\n");
 469                 break;
 470         case MEM_GOING_ONLINE:
 471         case MEM_ONLINE:
 472         case MEM_CANCEL_ONLINE:
 473                 break;
 474         }
 475
 476         return notifier_from_errno(ret);
 477 }
 478
 479 static struct notifier_block cmm_mem_nb = {
 480         .notifier_call = cmm_memory_cb,
 481         .priority = CMM_MEM_HOTPLUG_PRI
 482 };
 483
 484 #ifdef CONFIG_BALLOON_COMPACTION
 485 static struct vfsmount *balloon_mnt;
 486
 487 static int cmm_init_fs_context(struct fs_context *fc)
 488 {
 489         return init_pseudo(fc, PPC_CMM_MAGIC) ? 0 : -ENOMEM;
 490 }
 491
 492 static struct file_system_type balloon_fs = {
 493         .name = "ppc-cmm",
 494         .init_fs_context = cmm_init_fs_context,
 495         .kill_sb = kill_anon_super,
 496 };
 497
 498 static int cmm_migratepage(struct balloon_dev_info *b_dev_info,
 499                            struct page *newpage, struct page *page,
 500                            enum migrate_mode mode)
 501 {
 502         unsigned long flags;
 503
 504         /*
 505          * loan/"inflate" the newpage first.
 506          *
 507          * We might race against the cmm_thread who might discover after our
 508          * loan request that another page is to be unloaned. However, once
 509          * the cmm_thread runs again later, this error will automatically
 510          * be corrected.
 511          */
 512         if (plpar_page_set_loaned(newpage)) {
 513                 /* Unlikely, but possible. Tell the caller not to retry now. */
 514                 pr_err_ratelimited("%s: Cannot set page to loaned.", __func__);
 515                 return -EBUSY;
 516         }
 517
 518         /* balloon page list reference */
 519         get_page(newpage);
 520
 521         spin_lock_irqsave(&b_dev_info->pages_lock, flags);
 522         balloon_page_insert(b_dev_info, newpage);
 523         balloon_page_delete(page);
 524         b_dev_info->isolated_pages--;
 525         spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
 526
 527         /*
 528          * activate/"deflate" the old page. We ignore any errors just like the
 529          * other callers.
 530          */
 531         plpar_page_set_active(page);
 532
 533         /* balloon page list reference */
 534         put_page(page);
 535
 536         return MIGRATEPAGE_SUCCESS;
 537 }
 538
 539 static int cmm_balloon_compaction_init(void)
 540 {
 541         int rc;
 542
 543         balloon_devinfo_init(&b_dev_info);
 544         b_dev_info.migratepage = cmm_migratepage;
 545
 546         balloon_mnt = kern_mount(&balloon_fs);
 547         if (IS_ERR(balloon_mnt)) {
 548                 rc = PTR_ERR(balloon_mnt);
 549                 balloon_mnt = NULL;
 550                 return rc;
 551         }
 552
 553         b_dev_info.inode = alloc_anon_inode(balloon_mnt->mnt_sb);
 554         if (IS_ERR(b_dev_info.inode)) {
 555                 rc = PTR_ERR(b_dev_info.inode);
 556                 b_dev_info.inode = NULL;
 557                 kern_unmount(balloon_mnt);
 558                 balloon_mnt = NULL;
 559                 return rc;
 560         }
 561
 562         b_dev_info.inode->i_mapping->a_ops = &balloon_aops;
 563         return 0;
 564 }
 565 static void cmm_balloon_compaction_deinit(void)
 566 {
 567         if (b_dev_info.inode)
 568                 iput(b_dev_info.inode);
 569         b_dev_info.inode = NULL;
 570         kern_unmount(balloon_mnt);
 571         balloon_mnt = NULL;
 572 }
 573 #else /* CONFIG_BALLOON_COMPACTION */
 574 static int cmm_balloon_compaction_init(void)
 575 {
 576         return 0;
 577 }
 578
 579 static void cmm_balloon_compaction_deinit(void)
 580 {
 581 }
 582 #endif /* CONFIG_BALLOON_COMPACTION */
 583
 584 /**
 585  * cmm_init - Module initialization
 586  *
 587  * Return value:
 588  *      0 on success / other on failure
 589  **/
 590 static int cmm_init(void)
 591 {
 592         int rc;
 593
 594         if (!firmware_has_feature(FW_FEATURE_CMO))
 595                 return -EOPNOTSUPP;
 596
 597         rc = cmm_balloon_compaction_init();
 598         if (rc)
 599                 return rc;
 600
 601         rc = register_oom_notifier(&cmm_oom_nb);
 602         if (rc < 0)
 603                 goto out_balloon_compaction;
 604
 605         if ((rc = register_reboot_notifier(&cmm_reboot_nb)))
 606                 goto out_oom_notifier;
 607
 608         if ((rc = cmm_sysfs_register(&cmm_dev)))
 609                 goto out_reboot_notifier;
 610
 611         rc = register_memory_notifier(&cmm_mem_nb);
 612         if (rc)
 613                 goto out_unregister_notifier;
 614
 615         if (cmm_disabled)
 616                 return 0;
 617
 618         cmm_thread_ptr = kthread_run(cmm_thread, NULL, "cmmthread");
 619         if (IS_ERR(cmm_thread_ptr)) {
 620                 rc = PTR_ERR(cmm_thread_ptr);
 621                 goto out_unregister_notifier;
 622         }
 623
 624         return 0;
 625 out_unregister_notifier:
 626         unregister_memory_notifier(&cmm_mem_nb);
 627         cmm_unregister_sysfs(&cmm_dev);
 628 out_reboot_notifier:
 629         unregister_reboot_notifier(&cmm_reboot_nb);
 630 out_oom_notifier:
 631         unregister_oom_notifier(&cmm_oom_nb);
 632 out_balloon_compaction:
 633         cmm_balloon_compaction_deinit();
 634         return rc;
 635 }
 636
 637 /**
 638  * cmm_exit - Module exit
 639  *
 640  * Return value:
 641  *      nothing
 642  **/
 643 static void cmm_exit(void)
 644 {
 645         if (cmm_thread_ptr)
 646                 kthread_stop(cmm_thread_ptr);
 647         unregister_oom_notifier(&cmm_oom_nb);
 648         unregister_reboot_notifier(&cmm_reboot_nb);
 649         unregister_memory_notifier(&cmm_mem_nb);
 650         cmm_free_pages(atomic_long_read(&loaned_pages));
 651         cmm_unregister_sysfs(&cmm_dev);
 652         cmm_balloon_compaction_deinit();
 653 }
 654
 655 /**
 656  * cmm_set_disable - Disable/Enable CMM
 657  *
 658  * Return value:
 659  *      0 on success / other on failure
 660  **/
 661 static int cmm_set_disable(const char *val, const struct kernel_param *kp)
 662 {
 663         int disable = simple_strtoul(val, NULL, 10);
 664
 665         if (disable != 0 && disable != 1)
 666                 return -EINVAL;
 667
 668         if (disable && !cmm_disabled) {
 669                 if (cmm_thread_ptr)
 670                         kthread_stop(cmm_thread_ptr);
 671                 cmm_thread_ptr = NULL;
 672                 cmm_free_pages(atomic_long_read(&loaned_pages));
 673         } else if (!disable && cmm_disabled) {
 674                 cmm_thread_ptr = kthread_run(cmm_thread, NULL, "cmmthread");
 675                 if (IS_ERR(cmm_thread_ptr))
 676                         return PTR_ERR(cmm_thread_ptr);
 677         }
 678
 679         cmm_disabled = disable;
 680         return 0;
 681 }
 682
 683 module_param_call(disable, cmm_set_disable, param_get_uint,
 684                   &cmm_disabled, 0644);
 685 MODULE_PARM_DESC(disable, "Disable CMM. Set to 1 to disable. "
 686                  "[Default=" __stringify(CMM_DISABLE) "]");
 687
 688 module_init(cmm_init);
 689 module_exit(cmm_exit);