1 /* 2 * Collaborative memory management interface. 3 * 4 * Copyright (C) 2008 IBM Corporation 5 * Author(s): Brian King (brking@linux.vnet.ibm.com), 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License as published by 9 * the Free Software Foundation; either version 2 of the License, or 10 * (at your option) any later version. 11 * 12 * This program is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 * GNU General Public License for more details. 16 * 17 * You should have received a copy of the GNU General Public License 18 * along with this program; if not, write to the Free Software 19 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 20 * 21 */ 22 23 #include <linux/ctype.h> 24 #include <linux/delay.h> 25 #include <linux/errno.h> 26 #include <linux/fs.h> 27 #include <linux/gfp.h> 28 #include <linux/init.h> 29 #include <linux/kthread.h> 30 #include <linux/module.h> 31 #include <linux/oom.h> 32 #include <linux/reboot.h> 33 #include <linux/sched.h> 34 #include <linux/stringify.h> 35 #include <linux/swap.h> 36 #include <linux/device.h> 37 #include <asm/firmware.h> 38 #include <asm/hvcall.h> 39 #include <asm/mmu.h> 40 #include <asm/pgalloc.h> 41 #include <asm/uaccess.h> 42 #include <linux/memory.h> 43 #include <asm/plpar_wrappers.h> 44 45 #define CMM_DRIVER_VERSION "1.0.0" 46 #define CMM_DEFAULT_DELAY 1 47 #define CMM_HOTPLUG_DELAY 5 48 #define CMM_DEBUG 0 49 #define CMM_DISABLE 0 50 #define CMM_OOM_KB 1024 51 #define CMM_MIN_MEM_MB 256 52 #define KB2PAGES(_p) ((_p)>>(PAGE_SHIFT-10)) 53 #define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10)) 54 /* 55 * The priority level tries to ensure that this notifier is called as 56 * late as possible to reduce thrashing in the shared memory pool. 57 */ 58 #define CMM_MEM_HOTPLUG_PRI 1 59 #define CMM_MEM_ISOLATE_PRI 15 60 61 static unsigned int delay = CMM_DEFAULT_DELAY; 62 static unsigned int hotplug_delay = CMM_HOTPLUG_DELAY; 63 static unsigned int oom_kb = CMM_OOM_KB; 64 static unsigned int cmm_debug = CMM_DEBUG; 65 static unsigned int cmm_disabled = CMM_DISABLE; 66 static unsigned long min_mem_mb = CMM_MIN_MEM_MB; 67 static struct device cmm_dev; 68 69 MODULE_AUTHOR("Brian King <brking@linux.vnet.ibm.com>"); 70 MODULE_DESCRIPTION("IBM System p Collaborative Memory Manager"); 71 MODULE_LICENSE("GPL"); 72 MODULE_VERSION(CMM_DRIVER_VERSION); 73 74 module_param_named(delay, delay, uint, S_IRUGO | S_IWUSR); 75 MODULE_PARM_DESC(delay, "Delay (in seconds) between polls to query hypervisor paging requests. " 76 "[Default=" __stringify(CMM_DEFAULT_DELAY) "]"); 77 module_param_named(hotplug_delay, hotplug_delay, uint, S_IRUGO | S_IWUSR); 78 MODULE_PARM_DESC(delay, "Delay (in seconds) after memory hotplug remove " 79 "before loaning resumes. " 80 "[Default=" __stringify(CMM_HOTPLUG_DELAY) "]"); 81 module_param_named(oom_kb, oom_kb, uint, S_IRUGO | S_IWUSR); 82 MODULE_PARM_DESC(oom_kb, "Amount of memory in kb to free on OOM. " 83 "[Default=" __stringify(CMM_OOM_KB) "]"); 84 module_param_named(min_mem_mb, min_mem_mb, ulong, S_IRUGO | S_IWUSR); 85 MODULE_PARM_DESC(min_mem_mb, "Minimum amount of memory (in MB) to not balloon. " 86 "[Default=" __stringify(CMM_MIN_MEM_MB) "]"); 87 module_param_named(debug, cmm_debug, uint, S_IRUGO | S_IWUSR); 88 MODULE_PARM_DESC(debug, "Enable module debugging logging. Set to 1 to enable. " 89 "[Default=" __stringify(CMM_DEBUG) "]"); 90 91 #define CMM_NR_PAGES ((PAGE_SIZE - sizeof(void *) - sizeof(unsigned long)) / sizeof(unsigned long)) 92 93 #define cmm_dbg(...) if (cmm_debug) { printk(KERN_INFO "cmm: "__VA_ARGS__); } 94 95 struct cmm_page_array { 96 struct cmm_page_array *next; 97 unsigned long index; 98 unsigned long page[CMM_NR_PAGES]; 99 }; 100 101 static unsigned long loaned_pages; 102 static unsigned long loaned_pages_target; 103 static unsigned long oom_freed_pages; 104 105 static struct cmm_page_array *cmm_page_list; 106 static DEFINE_SPINLOCK(cmm_lock); 107 108 static DEFINE_MUTEX(hotplug_mutex); 109 static int hotplug_occurred; /* protected by the hotplug mutex */ 110 111 static struct task_struct *cmm_thread_ptr; 112 113 /** 114 * cmm_alloc_pages - Allocate pages and mark them as loaned 115 * @nr: number of pages to allocate 116 * 117 * Return value: 118 * number of pages requested to be allocated which were not 119 **/ 120 static long cmm_alloc_pages(long nr) 121 { 122 struct cmm_page_array *pa, *npa; 123 unsigned long addr; 124 long rc; 125 126 cmm_dbg("Begin request for %ld pages\n", nr); 127 128 while (nr) { 129 /* Exit if a hotplug operation is in progress or occurred */ 130 if (mutex_trylock(&hotplug_mutex)) { 131 if (hotplug_occurred) { 132 mutex_unlock(&hotplug_mutex); 133 break; 134 } 135 mutex_unlock(&hotplug_mutex); 136 } else { 137 break; 138 } 139 140 addr = __get_free_page(GFP_NOIO | __GFP_NOWARN | 141 __GFP_NORETRY | __GFP_NOMEMALLOC); 142 if (!addr) 143 break; 144 spin_lock(&cmm_lock); 145 pa = cmm_page_list; 146 if (!pa || pa->index >= CMM_NR_PAGES) { 147 /* Need a new page for the page list. */ 148 spin_unlock(&cmm_lock); 149 npa = (struct cmm_page_array *)__get_free_page( 150 GFP_NOIO | __GFP_NOWARN | 151 __GFP_NORETRY | __GFP_NOMEMALLOC); 152 if (!npa) { 153 pr_info("%s: Can not allocate new page list\n", __func__); 154 free_page(addr); 155 break; 156 } 157 spin_lock(&cmm_lock); 158 pa = cmm_page_list; 159 160 if (!pa || pa->index >= CMM_NR_PAGES) { 161 npa->next = pa; 162 npa->index = 0; 163 pa = npa; 164 cmm_page_list = pa; 165 } else 166 free_page((unsigned long) npa); 167 } 168 169 if ((rc = plpar_page_set_loaned(__pa(addr)))) { 170 pr_err("%s: Can not set page to loaned. rc=%ld\n", __func__, rc); 171 spin_unlock(&cmm_lock); 172 free_page(addr); 173 break; 174 } 175 176 pa->page[pa->index++] = addr; 177 loaned_pages++; 178 totalram_pages--; 179 spin_unlock(&cmm_lock); 180 nr--; 181 } 182 183 cmm_dbg("End request with %ld pages unfulfilled\n", nr); 184 return nr; 185 } 186 187 /** 188 * cmm_free_pages - Free pages and mark them as active 189 * @nr: number of pages to free 190 * 191 * Return value: 192 * number of pages requested to be freed which were not 193 **/ 194 static long cmm_free_pages(long nr) 195 { 196 struct cmm_page_array *pa; 197 unsigned long addr; 198 199 cmm_dbg("Begin free of %ld pages.\n", nr); 200 spin_lock(&cmm_lock); 201 pa = cmm_page_list; 202 while (nr) { 203 if (!pa || pa->index <= 0) 204 break; 205 addr = pa->page[--pa->index]; 206 207 if (pa->index == 0) { 208 pa = pa->next; 209 free_page((unsigned long) cmm_page_list); 210 cmm_page_list = pa; 211 } 212 213 plpar_page_set_active(__pa(addr)); 214 free_page(addr); 215 loaned_pages--; 216 nr--; 217 totalram_pages++; 218 } 219 spin_unlock(&cmm_lock); 220 cmm_dbg("End request with %ld pages unfulfilled\n", nr); 221 return nr; 222 } 223 224 /** 225 * cmm_oom_notify - OOM notifier 226 * @self: notifier block struct 227 * @dummy: not used 228 * @parm: returned - number of pages freed 229 * 230 * Return value: 231 * NOTIFY_OK 232 **/ 233 static int cmm_oom_notify(struct notifier_block *self, 234 unsigned long dummy, void *parm) 235 { 236 unsigned long *freed = parm; 237 long nr = KB2PAGES(oom_kb); 238 239 cmm_dbg("OOM processing started\n"); 240 nr = cmm_free_pages(nr); 241 loaned_pages_target = loaned_pages; 242 *freed += KB2PAGES(oom_kb) - nr; 243 oom_freed_pages += KB2PAGES(oom_kb) - nr; 244 cmm_dbg("OOM processing complete\n"); 245 return NOTIFY_OK; 246 } 247 248 /** 249 * cmm_get_mpp - Read memory performance parameters 250 * 251 * Makes hcall to query the current page loan request from the hypervisor. 252 * 253 * Return value: 254 * nothing 255 **/ 256 static void cmm_get_mpp(void) 257 { 258 int rc; 259 struct hvcall_mpp_data mpp_data; 260 signed long active_pages_target, page_loan_request, target; 261 signed long total_pages = totalram_pages + loaned_pages; 262 signed long min_mem_pages = (min_mem_mb * 1024 * 1024) / PAGE_SIZE; 263 264 rc = h_get_mpp(&mpp_data); 265 266 if (rc != H_SUCCESS) 267 return; 268 269 page_loan_request = div_s64((s64)mpp_data.loan_request, PAGE_SIZE); 270 target = page_loan_request + (signed long)loaned_pages; 271 272 if (target < 0 || total_pages < min_mem_pages) 273 target = 0; 274 275 if (target > oom_freed_pages) 276 target -= oom_freed_pages; 277 else 278 target = 0; 279 280 active_pages_target = total_pages - target; 281 282 if (min_mem_pages > active_pages_target) 283 target = total_pages - min_mem_pages; 284 285 if (target < 0) 286 target = 0; 287 288 loaned_pages_target = target; 289 290 cmm_dbg("delta = %ld, loaned = %lu, target = %lu, oom = %lu, totalram = %lu\n", 291 page_loan_request, loaned_pages, loaned_pages_target, 292 oom_freed_pages, totalram_pages); 293 } 294 295 static struct notifier_block cmm_oom_nb = { 296 .notifier_call = cmm_oom_notify 297 }; 298 299 /** 300 * cmm_thread - CMM task thread 301 * @dummy: not used 302 * 303 * Return value: 304 * 0 305 **/ 306 static int cmm_thread(void *dummy) 307 { 308 unsigned long timeleft; 309 310 while (1) { 311 timeleft = msleep_interruptible(delay * 1000); 312 313 if (kthread_should_stop() || timeleft) 314 break; 315 316 if (mutex_trylock(&hotplug_mutex)) { 317 if (hotplug_occurred) { 318 hotplug_occurred = 0; 319 mutex_unlock(&hotplug_mutex); 320 cmm_dbg("Hotplug operation has occurred, " 321 "loaning activity suspended " 322 "for %d seconds.\n", 323 hotplug_delay); 324 timeleft = msleep_interruptible(hotplug_delay * 325 1000); 326 if (kthread_should_stop() || timeleft) 327 break; 328 continue; 329 } 330 mutex_unlock(&hotplug_mutex); 331 } else { 332 cmm_dbg("Hotplug operation in progress, activity " 333 "suspended\n"); 334 continue; 335 } 336 337 cmm_get_mpp(); 338 339 if (loaned_pages_target > loaned_pages) { 340 if (cmm_alloc_pages(loaned_pages_target - loaned_pages)) 341 loaned_pages_target = loaned_pages; 342 } else if (loaned_pages_target < loaned_pages) 343 cmm_free_pages(loaned_pages - loaned_pages_target); 344 } 345 return 0; 346 } 347 348 #define CMM_SHOW(name, format, args...) \ 349 static ssize_t show_##name(struct device *dev, \ 350 struct device_attribute *attr, \ 351 char *buf) \ 352 { \ 353 return sprintf(buf, format, ##args); \ 354 } \ 355 static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL) 356 357 CMM_SHOW(loaned_kb, "%lu\n", PAGES2KB(loaned_pages)); 358 CMM_SHOW(loaned_target_kb, "%lu\n", PAGES2KB(loaned_pages_target)); 359 360 static ssize_t show_oom_pages(struct device *dev, 361 struct device_attribute *attr, char *buf) 362 { 363 return sprintf(buf, "%lu\n", PAGES2KB(oom_freed_pages)); 364 } 365 366 static ssize_t store_oom_pages(struct device *dev, 367 struct device_attribute *attr, 368 const char *buf, size_t count) 369 { 370 unsigned long val = simple_strtoul (buf, NULL, 10); 371 372 if (!capable(CAP_SYS_ADMIN)) 373 return -EPERM; 374 if (val != 0) 375 return -EBADMSG; 376 377 oom_freed_pages = 0; 378 return count; 379 } 380 381 static DEVICE_ATTR(oom_freed_kb, S_IWUSR | S_IRUGO, 382 show_oom_pages, store_oom_pages); 383 384 static struct device_attribute *cmm_attrs[] = { 385 &dev_attr_loaned_kb, 386 &dev_attr_loaned_target_kb, 387 &dev_attr_oom_freed_kb, 388 }; 389 390 static struct bus_type cmm_subsys = { 391 .name = "cmm", 392 .dev_name = "cmm", 393 }; 394 395 /** 396 * cmm_sysfs_register - Register with sysfs 397 * 398 * Return value: 399 * 0 on success / other on failure 400 **/ 401 static int cmm_sysfs_register(struct device *dev) 402 { 403 int i, rc; 404 405 if ((rc = subsys_system_register(&cmm_subsys, NULL))) 406 return rc; 407 408 dev->id = 0; 409 dev->bus = &cmm_subsys; 410 411 if ((rc = device_register(dev))) 412 goto subsys_unregister; 413 414 for (i = 0; i < ARRAY_SIZE(cmm_attrs); i++) { 415 if ((rc = device_create_file(dev, cmm_attrs[i]))) 416 goto fail; 417 } 418 419 return 0; 420 421 fail: 422 while (--i >= 0) 423 device_remove_file(dev, cmm_attrs[i]); 424 device_unregister(dev); 425 subsys_unregister: 426 bus_unregister(&cmm_subsys); 427 return rc; 428 } 429 430 /** 431 * cmm_unregister_sysfs - Unregister from sysfs 432 * 433 **/ 434 static void cmm_unregister_sysfs(struct device *dev) 435 { 436 int i; 437 438 for (i = 0; i < ARRAY_SIZE(cmm_attrs); i++) 439 device_remove_file(dev, cmm_attrs[i]); 440 device_unregister(dev); 441 bus_unregister(&cmm_subsys); 442 } 443 444 /** 445 * cmm_reboot_notifier - Make sure pages are not still marked as "loaned" 446 * 447 **/ 448 static int cmm_reboot_notifier(struct notifier_block *nb, 449 unsigned long action, void *unused) 450 { 451 if (action == SYS_RESTART) { 452 if (cmm_thread_ptr) 453 kthread_stop(cmm_thread_ptr); 454 cmm_thread_ptr = NULL; 455 cmm_free_pages(loaned_pages); 456 } 457 return NOTIFY_DONE; 458 } 459 460 static struct notifier_block cmm_reboot_nb = { 461 .notifier_call = cmm_reboot_notifier, 462 }; 463 464 /** 465 * cmm_count_pages - Count the number of pages loaned in a particular range. 466 * 467 * @arg: memory_isolate_notify structure with address range and count 468 * 469 * Return value: 470 * 0 on success 471 **/ 472 static unsigned long cmm_count_pages(void *arg) 473 { 474 struct memory_isolate_notify *marg = arg; 475 struct cmm_page_array *pa; 476 unsigned long start = (unsigned long)pfn_to_kaddr(marg->start_pfn); 477 unsigned long end = start + (marg->nr_pages << PAGE_SHIFT); 478 unsigned long idx; 479 480 spin_lock(&cmm_lock); 481 pa = cmm_page_list; 482 while (pa) { 483 if ((unsigned long)pa >= start && (unsigned long)pa < end) 484 marg->pages_found++; 485 for (idx = 0; idx < pa->index; idx++) 486 if (pa->page[idx] >= start && pa->page[idx] < end) 487 marg->pages_found++; 488 pa = pa->next; 489 } 490 spin_unlock(&cmm_lock); 491 return 0; 492 } 493 494 /** 495 * cmm_memory_isolate_cb - Handle memory isolation notifier calls 496 * @self: notifier block struct 497 * @action: action to take 498 * @arg: struct memory_isolate_notify data for handler 499 * 500 * Return value: 501 * NOTIFY_OK or notifier error based on subfunction return value 502 **/ 503 static int cmm_memory_isolate_cb(struct notifier_block *self, 504 unsigned long action, void *arg) 505 { 506 int ret = 0; 507 508 if (action == MEM_ISOLATE_COUNT) 509 ret = cmm_count_pages(arg); 510 511 return notifier_from_errno(ret); 512 } 513 514 static struct notifier_block cmm_mem_isolate_nb = { 515 .notifier_call = cmm_memory_isolate_cb, 516 .priority = CMM_MEM_ISOLATE_PRI 517 }; 518 519 /** 520 * cmm_mem_going_offline - Unloan pages where memory is to be removed 521 * @arg: memory_notify structure with page range to be offlined 522 * 523 * Return value: 524 * 0 on success 525 **/ 526 static int cmm_mem_going_offline(void *arg) 527 { 528 struct memory_notify *marg = arg; 529 unsigned long start_page = (unsigned long)pfn_to_kaddr(marg->start_pfn); 530 unsigned long end_page = start_page + (marg->nr_pages << PAGE_SHIFT); 531 struct cmm_page_array *pa_curr, *pa_last, *npa; 532 unsigned long idx; 533 unsigned long freed = 0; 534 535 cmm_dbg("Memory going offline, searching 0x%lx (%ld pages).\n", 536 start_page, marg->nr_pages); 537 spin_lock(&cmm_lock); 538 539 /* Search the page list for pages in the range to be offlined */ 540 pa_last = pa_curr = cmm_page_list; 541 while (pa_curr) { 542 for (idx = (pa_curr->index - 1); (idx + 1) > 0; idx--) { 543 if ((pa_curr->page[idx] < start_page) || 544 (pa_curr->page[idx] >= end_page)) 545 continue; 546 547 plpar_page_set_active(__pa(pa_curr->page[idx])); 548 free_page(pa_curr->page[idx]); 549 freed++; 550 loaned_pages--; 551 totalram_pages++; 552 pa_curr->page[idx] = pa_last->page[--pa_last->index]; 553 if (pa_last->index == 0) { 554 if (pa_curr == pa_last) 555 pa_curr = pa_last->next; 556 pa_last = pa_last->next; 557 free_page((unsigned long)cmm_page_list); 558 cmm_page_list = pa_last; 559 continue; 560 } 561 } 562 pa_curr = pa_curr->next; 563 } 564 565 /* Search for page list structures in the range to be offlined */ 566 pa_last = NULL; 567 pa_curr = cmm_page_list; 568 while (pa_curr) { 569 if (((unsigned long)pa_curr >= start_page) && 570 ((unsigned long)pa_curr < end_page)) { 571 npa = (struct cmm_page_array *)__get_free_page( 572 GFP_NOIO | __GFP_NOWARN | 573 __GFP_NORETRY | __GFP_NOMEMALLOC); 574 if (!npa) { 575 spin_unlock(&cmm_lock); 576 cmm_dbg("Failed to allocate memory for list " 577 "management. Memory hotplug " 578 "failed.\n"); 579 return ENOMEM; 580 } 581 memcpy(npa, pa_curr, PAGE_SIZE); 582 if (pa_curr == cmm_page_list) 583 cmm_page_list = npa; 584 if (pa_last) 585 pa_last->next = npa; 586 free_page((unsigned long) pa_curr); 587 freed++; 588 pa_curr = npa; 589 } 590 591 pa_last = pa_curr; 592 pa_curr = pa_curr->next; 593 } 594 595 spin_unlock(&cmm_lock); 596 cmm_dbg("Released %ld pages in the search range.\n", freed); 597 598 return 0; 599 } 600 601 /** 602 * cmm_memory_cb - Handle memory hotplug notifier calls 603 * @self: notifier block struct 604 * @action: action to take 605 * @arg: struct memory_notify data for handler 606 * 607 * Return value: 608 * NOTIFY_OK or notifier error based on subfunction return value 609 * 610 **/ 611 static int cmm_memory_cb(struct notifier_block *self, 612 unsigned long action, void *arg) 613 { 614 int ret = 0; 615 616 switch (action) { 617 case MEM_GOING_OFFLINE: 618 mutex_lock(&hotplug_mutex); 619 hotplug_occurred = 1; 620 ret = cmm_mem_going_offline(arg); 621 break; 622 case MEM_OFFLINE: 623 case MEM_CANCEL_OFFLINE: 624 mutex_unlock(&hotplug_mutex); 625 cmm_dbg("Memory offline operation complete.\n"); 626 break; 627 case MEM_GOING_ONLINE: 628 case MEM_ONLINE: 629 case MEM_CANCEL_ONLINE: 630 break; 631 } 632 633 return notifier_from_errno(ret); 634 } 635 636 static struct notifier_block cmm_mem_nb = { 637 .notifier_call = cmm_memory_cb, 638 .priority = CMM_MEM_HOTPLUG_PRI 639 }; 640 641 /** 642 * cmm_init - Module initialization 643 * 644 * Return value: 645 * 0 on success / other on failure 646 **/ 647 static int cmm_init(void) 648 { 649 int rc = -ENOMEM; 650 651 if (!firmware_has_feature(FW_FEATURE_CMO)) 652 return -EOPNOTSUPP; 653 654 if ((rc = register_oom_notifier(&cmm_oom_nb)) < 0) 655 return rc; 656 657 if ((rc = register_reboot_notifier(&cmm_reboot_nb))) 658 goto out_oom_notifier; 659 660 if ((rc = cmm_sysfs_register(&cmm_dev))) 661 goto out_reboot_notifier; 662 663 if (register_memory_notifier(&cmm_mem_nb) || 664 register_memory_isolate_notifier(&cmm_mem_isolate_nb)) 665 goto out_unregister_notifier; 666 667 if (cmm_disabled) 668 return rc; 669 670 cmm_thread_ptr = kthread_run(cmm_thread, NULL, "cmmthread"); 671 if (IS_ERR(cmm_thread_ptr)) { 672 rc = PTR_ERR(cmm_thread_ptr); 673 goto out_unregister_notifier; 674 } 675 676 return rc; 677 678 out_unregister_notifier: 679 unregister_memory_notifier(&cmm_mem_nb); 680 unregister_memory_isolate_notifier(&cmm_mem_isolate_nb); 681 cmm_unregister_sysfs(&cmm_dev); 682 out_reboot_notifier: 683 unregister_reboot_notifier(&cmm_reboot_nb); 684 out_oom_notifier: 685 unregister_oom_notifier(&cmm_oom_nb); 686 return rc; 687 } 688 689 /** 690 * cmm_exit - Module exit 691 * 692 * Return value: 693 * nothing 694 **/ 695 static void cmm_exit(void) 696 { 697 if (cmm_thread_ptr) 698 kthread_stop(cmm_thread_ptr); 699 unregister_oom_notifier(&cmm_oom_nb); 700 unregister_reboot_notifier(&cmm_reboot_nb); 701 unregister_memory_notifier(&cmm_mem_nb); 702 unregister_memory_isolate_notifier(&cmm_mem_isolate_nb); 703 cmm_free_pages(loaned_pages); 704 cmm_unregister_sysfs(&cmm_dev); 705 } 706 707 /** 708 * cmm_set_disable - Disable/Enable CMM 709 * 710 * Return value: 711 * 0 on success / other on failure 712 **/ 713 static int cmm_set_disable(const char *val, struct kernel_param *kp) 714 { 715 int disable = simple_strtoul(val, NULL, 10); 716 717 if (disable != 0 && disable != 1) 718 return -EINVAL; 719 720 if (disable && !cmm_disabled) { 721 if (cmm_thread_ptr) 722 kthread_stop(cmm_thread_ptr); 723 cmm_thread_ptr = NULL; 724 cmm_free_pages(loaned_pages); 725 } else if (!disable && cmm_disabled) { 726 cmm_thread_ptr = kthread_run(cmm_thread, NULL, "cmmthread"); 727 if (IS_ERR(cmm_thread_ptr)) 728 return PTR_ERR(cmm_thread_ptr); 729 } 730 731 cmm_disabled = disable; 732 return 0; 733 } 734 735 module_param_call(disable, cmm_set_disable, param_get_uint, 736 &cmm_disabled, S_IRUGO | S_IWUSR); 737 MODULE_PARM_DESC(disable, "Disable CMM. Set to 1 to disable. " 738 "[Default=" __stringify(CMM_DISABLE) "]"); 739 740 module_init(cmm_init); 741 module_exit(cmm_exit); 742