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 44 #include "plpar_wrappers.h" 45 46 #define CMM_DRIVER_VERSION "1.0.0" 47 #define CMM_DEFAULT_DELAY 1 48 #define CMM_HOTPLUG_DELAY 5 49 #define CMM_DEBUG 0 50 #define CMM_DISABLE 0 51 #define CMM_OOM_KB 1024 52 #define CMM_MIN_MEM_MB 256 53 #define KB2PAGES(_p) ((_p)>>(PAGE_SHIFT-10)) 54 #define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10)) 55 /* 56 * The priority level tries to ensure that this notifier is called as 57 * late as possible to reduce thrashing in the shared memory pool. 58 */ 59 #define CMM_MEM_HOTPLUG_PRI 1 60 #define CMM_MEM_ISOLATE_PRI 15 61 62 static unsigned int delay = CMM_DEFAULT_DELAY; 63 static unsigned int hotplug_delay = CMM_HOTPLUG_DELAY; 64 static unsigned int oom_kb = CMM_OOM_KB; 65 static unsigned int cmm_debug = CMM_DEBUG; 66 static unsigned int cmm_disabled = CMM_DISABLE; 67 static unsigned long min_mem_mb = CMM_MIN_MEM_MB; 68 static struct device cmm_dev; 69 70 MODULE_AUTHOR("Brian King <brking@linux.vnet.ibm.com>"); 71 MODULE_DESCRIPTION("IBM System p Collaborative Memory Manager"); 72 MODULE_LICENSE("GPL"); 73 MODULE_VERSION(CMM_DRIVER_VERSION); 74 75 module_param_named(delay, delay, uint, S_IRUGO | S_IWUSR); 76 MODULE_PARM_DESC(delay, "Delay (in seconds) between polls to query hypervisor paging requests. " 77 "[Default=" __stringify(CMM_DEFAULT_DELAY) "]"); 78 module_param_named(hotplug_delay, hotplug_delay, uint, S_IRUGO | S_IWUSR); 79 MODULE_PARM_DESC(delay, "Delay (in seconds) after memory hotplug remove " 80 "before loaning resumes. " 81 "[Default=" __stringify(CMM_HOTPLUG_DELAY) "]"); 82 module_param_named(oom_kb, oom_kb, uint, S_IRUGO | S_IWUSR); 83 MODULE_PARM_DESC(oom_kb, "Amount of memory in kb to free on OOM. " 84 "[Default=" __stringify(CMM_OOM_KB) "]"); 85 module_param_named(min_mem_mb, min_mem_mb, ulong, S_IRUGO | S_IWUSR); 86 MODULE_PARM_DESC(min_mem_mb, "Minimum amount of memory (in MB) to not balloon. " 87 "[Default=" __stringify(CMM_MIN_MEM_MB) "]"); 88 module_param_named(debug, cmm_debug, uint, S_IRUGO | S_IWUSR); 89 MODULE_PARM_DESC(debug, "Enable module debugging logging. Set to 1 to enable. " 90 "[Default=" __stringify(CMM_DEBUG) "]"); 91 92 #define CMM_NR_PAGES ((PAGE_SIZE - sizeof(void *) - sizeof(unsigned long)) / sizeof(unsigned long)) 93 94 #define cmm_dbg(...) if (cmm_debug) { printk(KERN_INFO "cmm: "__VA_ARGS__); } 95 96 struct cmm_page_array { 97 struct cmm_page_array *next; 98 unsigned long index; 99 unsigned long page[CMM_NR_PAGES]; 100 }; 101 102 static unsigned long loaned_pages; 103 static unsigned long loaned_pages_target; 104 static unsigned long oom_freed_pages; 105 106 static struct cmm_page_array *cmm_page_list; 107 static DEFINE_SPINLOCK(cmm_lock); 108 109 static DEFINE_MUTEX(hotplug_mutex); 110 static int hotplug_occurred; /* protected by the hotplug mutex */ 111 112 static struct task_struct *cmm_thread_ptr; 113 114 /** 115 * cmm_alloc_pages - Allocate pages and mark them as loaned 116 * @nr: number of pages to allocate 117 * 118 * Return value: 119 * number of pages requested to be allocated which were not 120 **/ 121 static long cmm_alloc_pages(long nr) 122 { 123 struct cmm_page_array *pa, *npa; 124 unsigned long addr; 125 long rc; 126 127 cmm_dbg("Begin request for %ld pages\n", nr); 128 129 while (nr) { 130 /* Exit if a hotplug operation is in progress or occurred */ 131 if (mutex_trylock(&hotplug_mutex)) { 132 if (hotplug_occurred) { 133 mutex_unlock(&hotplug_mutex); 134 break; 135 } 136 mutex_unlock(&hotplug_mutex); 137 } else { 138 break; 139 } 140 141 addr = __get_free_page(GFP_NOIO | __GFP_NOWARN | 142 __GFP_NORETRY | __GFP_NOMEMALLOC); 143 if (!addr) 144 break; 145 spin_lock(&cmm_lock); 146 pa = cmm_page_list; 147 if (!pa || pa->index >= CMM_NR_PAGES) { 148 /* Need a new page for the page list. */ 149 spin_unlock(&cmm_lock); 150 npa = (struct cmm_page_array *)__get_free_page( 151 GFP_NOIO | __GFP_NOWARN | 152 __GFP_NORETRY | __GFP_NOMEMALLOC); 153 if (!npa) { 154 pr_info("%s: Can not allocate new page list\n", __func__); 155 free_page(addr); 156 break; 157 } 158 spin_lock(&cmm_lock); 159 pa = cmm_page_list; 160 161 if (!pa || pa->index >= CMM_NR_PAGES) { 162 npa->next = pa; 163 npa->index = 0; 164 pa = npa; 165 cmm_page_list = pa; 166 } else 167 free_page((unsigned long) npa); 168 } 169 170 if ((rc = plpar_page_set_loaned(__pa(addr)))) { 171 pr_err("%s: Can not set page to loaned. rc=%ld\n", __func__, rc); 172 spin_unlock(&cmm_lock); 173 free_page(addr); 174 break; 175 } 176 177 pa->page[pa->index++] = addr; 178 loaned_pages++; 179 totalram_pages--; 180 spin_unlock(&cmm_lock); 181 nr--; 182 } 183 184 cmm_dbg("End request with %ld pages unfulfilled\n", nr); 185 return nr; 186 } 187 188 /** 189 * cmm_free_pages - Free pages and mark them as active 190 * @nr: number of pages to free 191 * 192 * Return value: 193 * number of pages requested to be freed which were not 194 **/ 195 static long cmm_free_pages(long nr) 196 { 197 struct cmm_page_array *pa; 198 unsigned long addr; 199 200 cmm_dbg("Begin free of %ld pages.\n", nr); 201 spin_lock(&cmm_lock); 202 pa = cmm_page_list; 203 while (nr) { 204 if (!pa || pa->index <= 0) 205 break; 206 addr = pa->page[--pa->index]; 207 208 if (pa->index == 0) { 209 pa = pa->next; 210 free_page((unsigned long) cmm_page_list); 211 cmm_page_list = pa; 212 } 213 214 plpar_page_set_active(__pa(addr)); 215 free_page(addr); 216 loaned_pages--; 217 nr--; 218 totalram_pages++; 219 } 220 spin_unlock(&cmm_lock); 221 cmm_dbg("End request with %ld pages unfulfilled\n", nr); 222 return nr; 223 } 224 225 /** 226 * cmm_oom_notify - OOM notifier 227 * @self: notifier block struct 228 * @dummy: not used 229 * @parm: returned - number of pages freed 230 * 231 * Return value: 232 * NOTIFY_OK 233 **/ 234 static int cmm_oom_notify(struct notifier_block *self, 235 unsigned long dummy, void *parm) 236 { 237 unsigned long *freed = parm; 238 long nr = KB2PAGES(oom_kb); 239 240 cmm_dbg("OOM processing started\n"); 241 nr = cmm_free_pages(nr); 242 loaned_pages_target = loaned_pages; 243 *freed += KB2PAGES(oom_kb) - nr; 244 oom_freed_pages += KB2PAGES(oom_kb) - nr; 245 cmm_dbg("OOM processing complete\n"); 246 return NOTIFY_OK; 247 } 248 249 /** 250 * cmm_get_mpp - Read memory performance parameters 251 * 252 * Makes hcall to query the current page loan request from the hypervisor. 253 * 254 * Return value: 255 * nothing 256 **/ 257 static void cmm_get_mpp(void) 258 { 259 int rc; 260 struct hvcall_mpp_data mpp_data; 261 signed long active_pages_target, page_loan_request, target; 262 signed long total_pages = totalram_pages + loaned_pages; 263 signed long min_mem_pages = (min_mem_mb * 1024 * 1024) / PAGE_SIZE; 264 265 rc = h_get_mpp(&mpp_data); 266 267 if (rc != H_SUCCESS) 268 return; 269 270 page_loan_request = div_s64((s64)mpp_data.loan_request, PAGE_SIZE); 271 target = page_loan_request + (signed long)loaned_pages; 272 273 if (target < 0 || total_pages < min_mem_pages) 274 target = 0; 275 276 if (target > oom_freed_pages) 277 target -= oom_freed_pages; 278 else 279 target = 0; 280 281 active_pages_target = total_pages - target; 282 283 if (min_mem_pages > active_pages_target) 284 target = total_pages - min_mem_pages; 285 286 if (target < 0) 287 target = 0; 288 289 loaned_pages_target = target; 290 291 cmm_dbg("delta = %ld, loaned = %lu, target = %lu, oom = %lu, totalram = %lu\n", 292 page_loan_request, loaned_pages, loaned_pages_target, 293 oom_freed_pages, totalram_pages); 294 } 295 296 static struct notifier_block cmm_oom_nb = { 297 .notifier_call = cmm_oom_notify 298 }; 299 300 /** 301 * cmm_thread - CMM task thread 302 * @dummy: not used 303 * 304 * Return value: 305 * 0 306 **/ 307 static int cmm_thread(void *dummy) 308 { 309 unsigned long timeleft; 310 311 while (1) { 312 timeleft = msleep_interruptible(delay * 1000); 313 314 if (kthread_should_stop() || timeleft) 315 break; 316 317 if (mutex_trylock(&hotplug_mutex)) { 318 if (hotplug_occurred) { 319 hotplug_occurred = 0; 320 mutex_unlock(&hotplug_mutex); 321 cmm_dbg("Hotplug operation has occurred, " 322 "loaning activity suspended " 323 "for %d seconds.\n", 324 hotplug_delay); 325 timeleft = msleep_interruptible(hotplug_delay * 326 1000); 327 if (kthread_should_stop() || timeleft) 328 break; 329 continue; 330 } 331 mutex_unlock(&hotplug_mutex); 332 } else { 333 cmm_dbg("Hotplug operation in progress, activity " 334 "suspended\n"); 335 continue; 336 } 337 338 cmm_get_mpp(); 339 340 if (loaned_pages_target > loaned_pages) { 341 if (cmm_alloc_pages(loaned_pages_target - loaned_pages)) 342 loaned_pages_target = loaned_pages; 343 } else if (loaned_pages_target < loaned_pages) 344 cmm_free_pages(loaned_pages - loaned_pages_target); 345 } 346 return 0; 347 } 348 349 #define CMM_SHOW(name, format, args...) \ 350 static ssize_t show_##name(struct device *dev, \ 351 struct device_attribute *attr, \ 352 char *buf) \ 353 { \ 354 return sprintf(buf, format, ##args); \ 355 } \ 356 static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL) 357 358 CMM_SHOW(loaned_kb, "%lu\n", PAGES2KB(loaned_pages)); 359 CMM_SHOW(loaned_target_kb, "%lu\n", PAGES2KB(loaned_pages_target)); 360 361 static ssize_t show_oom_pages(struct device *dev, 362 struct device_attribute *attr, char *buf) 363 { 364 return sprintf(buf, "%lu\n", PAGES2KB(oom_freed_pages)); 365 } 366 367 static ssize_t store_oom_pages(struct device *dev, 368 struct device_attribute *attr, 369 const char *buf, size_t count) 370 { 371 unsigned long val = simple_strtoul (buf, NULL, 10); 372 373 if (!capable(CAP_SYS_ADMIN)) 374 return -EPERM; 375 if (val != 0) 376 return -EBADMSG; 377 378 oom_freed_pages = 0; 379 return count; 380 } 381 382 static DEVICE_ATTR(oom_freed_kb, S_IWUSR | S_IRUGO, 383 show_oom_pages, store_oom_pages); 384 385 static struct device_attribute *cmm_attrs[] = { 386 &dev_attr_loaned_kb, 387 &dev_attr_loaned_target_kb, 388 &dev_attr_oom_freed_kb, 389 }; 390 391 static struct bus_type cmm_subsys = { 392 .name = "cmm", 393 .dev_name = "cmm", 394 }; 395 396 /** 397 * cmm_sysfs_register - Register with sysfs 398 * 399 * Return value: 400 * 0 on success / other on failure 401 **/ 402 static int cmm_sysfs_register(struct device *dev) 403 { 404 int i, rc; 405 406 if ((rc = subsys_system_register(&cmm_subsys, NULL))) 407 return rc; 408 409 dev->id = 0; 410 dev->bus = &cmm_subsys; 411 412 if ((rc = device_register(dev))) 413 goto subsys_unregister; 414 415 for (i = 0; i < ARRAY_SIZE(cmm_attrs); i++) { 416 if ((rc = device_create_file(dev, cmm_attrs[i]))) 417 goto fail; 418 } 419 420 return 0; 421 422 fail: 423 while (--i >= 0) 424 device_remove_file(dev, cmm_attrs[i]); 425 device_unregister(dev); 426 subsys_unregister: 427 bus_unregister(&cmm_subsys); 428 return rc; 429 } 430 431 /** 432 * cmm_unregister_sysfs - Unregister from sysfs 433 * 434 **/ 435 static void cmm_unregister_sysfs(struct device *dev) 436 { 437 int i; 438 439 for (i = 0; i < ARRAY_SIZE(cmm_attrs); i++) 440 device_remove_file(dev, cmm_attrs[i]); 441 device_unregister(dev); 442 bus_unregister(&cmm_subsys); 443 } 444 445 /** 446 * cmm_reboot_notifier - Make sure pages are not still marked as "loaned" 447 * 448 **/ 449 static int cmm_reboot_notifier(struct notifier_block *nb, 450 unsigned long action, void *unused) 451 { 452 if (action == SYS_RESTART) { 453 if (cmm_thread_ptr) 454 kthread_stop(cmm_thread_ptr); 455 cmm_thread_ptr = NULL; 456 cmm_free_pages(loaned_pages); 457 } 458 return NOTIFY_DONE; 459 } 460 461 static struct notifier_block cmm_reboot_nb = { 462 .notifier_call = cmm_reboot_notifier, 463 }; 464 465 /** 466 * cmm_count_pages - Count the number of pages loaned in a particular range. 467 * 468 * @arg: memory_isolate_notify structure with address range and count 469 * 470 * Return value: 471 * 0 on success 472 **/ 473 static unsigned long cmm_count_pages(void *arg) 474 { 475 struct memory_isolate_notify *marg = arg; 476 struct cmm_page_array *pa; 477 unsigned long start = (unsigned long)pfn_to_kaddr(marg->start_pfn); 478 unsigned long end = start + (marg->nr_pages << PAGE_SHIFT); 479 unsigned long idx; 480 481 spin_lock(&cmm_lock); 482 pa = cmm_page_list; 483 while (pa) { 484 if ((unsigned long)pa >= start && (unsigned long)pa < end) 485 marg->pages_found++; 486 for (idx = 0; idx < pa->index; idx++) 487 if (pa->page[idx] >= start && pa->page[idx] < end) 488 marg->pages_found++; 489 pa = pa->next; 490 } 491 spin_unlock(&cmm_lock); 492 return 0; 493 } 494 495 /** 496 * cmm_memory_isolate_cb - Handle memory isolation notifier calls 497 * @self: notifier block struct 498 * @action: action to take 499 * @arg: struct memory_isolate_notify data for handler 500 * 501 * Return value: 502 * NOTIFY_OK or notifier error based on subfunction return value 503 **/ 504 static int cmm_memory_isolate_cb(struct notifier_block *self, 505 unsigned long action, void *arg) 506 { 507 int ret = 0; 508 509 if (action == MEM_ISOLATE_COUNT) 510 ret = cmm_count_pages(arg); 511 512 return notifier_from_errno(ret); 513 } 514 515 static struct notifier_block cmm_mem_isolate_nb = { 516 .notifier_call = cmm_memory_isolate_cb, 517 .priority = CMM_MEM_ISOLATE_PRI 518 }; 519 520 /** 521 * cmm_mem_going_offline - Unloan pages where memory is to be removed 522 * @arg: memory_notify structure with page range to be offlined 523 * 524 * Return value: 525 * 0 on success 526 **/ 527 static int cmm_mem_going_offline(void *arg) 528 { 529 struct memory_notify *marg = arg; 530 unsigned long start_page = (unsigned long)pfn_to_kaddr(marg->start_pfn); 531 unsigned long end_page = start_page + (marg->nr_pages << PAGE_SHIFT); 532 struct cmm_page_array *pa_curr, *pa_last, *npa; 533 unsigned long idx; 534 unsigned long freed = 0; 535 536 cmm_dbg("Memory going offline, searching 0x%lx (%ld pages).\n", 537 start_page, marg->nr_pages); 538 spin_lock(&cmm_lock); 539 540 /* Search the page list for pages in the range to be offlined */ 541 pa_last = pa_curr = cmm_page_list; 542 while (pa_curr) { 543 for (idx = (pa_curr->index - 1); (idx + 1) > 0; idx--) { 544 if ((pa_curr->page[idx] < start_page) || 545 (pa_curr->page[idx] >= end_page)) 546 continue; 547 548 plpar_page_set_active(__pa(pa_curr->page[idx])); 549 free_page(pa_curr->page[idx]); 550 freed++; 551 loaned_pages--; 552 totalram_pages++; 553 pa_curr->page[idx] = pa_last->page[--pa_last->index]; 554 if (pa_last->index == 0) { 555 if (pa_curr == pa_last) 556 pa_curr = pa_last->next; 557 pa_last = pa_last->next; 558 free_page((unsigned long)cmm_page_list); 559 cmm_page_list = pa_last; 560 continue; 561 } 562 } 563 pa_curr = pa_curr->next; 564 } 565 566 /* Search for page list structures in the range to be offlined */ 567 pa_last = NULL; 568 pa_curr = cmm_page_list; 569 while (pa_curr) { 570 if (((unsigned long)pa_curr >= start_page) && 571 ((unsigned long)pa_curr < end_page)) { 572 npa = (struct cmm_page_array *)__get_free_page( 573 GFP_NOIO | __GFP_NOWARN | 574 __GFP_NORETRY | __GFP_NOMEMALLOC); 575 if (!npa) { 576 spin_unlock(&cmm_lock); 577 cmm_dbg("Failed to allocate memory for list " 578 "management. Memory hotplug " 579 "failed.\n"); 580 return ENOMEM; 581 } 582 memcpy(npa, pa_curr, PAGE_SIZE); 583 if (pa_curr == cmm_page_list) 584 cmm_page_list = npa; 585 if (pa_last) 586 pa_last->next = npa; 587 free_page((unsigned long) pa_curr); 588 freed++; 589 pa_curr = npa; 590 } 591 592 pa_last = pa_curr; 593 pa_curr = pa_curr->next; 594 } 595 596 spin_unlock(&cmm_lock); 597 cmm_dbg("Released %ld pages in the search range.\n", freed); 598 599 return 0; 600 } 601 602 /** 603 * cmm_memory_cb - Handle memory hotplug notifier calls 604 * @self: notifier block struct 605 * @action: action to take 606 * @arg: struct memory_notify data for handler 607 * 608 * Return value: 609 * NOTIFY_OK or notifier error based on subfunction return value 610 * 611 **/ 612 static int cmm_memory_cb(struct notifier_block *self, 613 unsigned long action, void *arg) 614 { 615 int ret = 0; 616 617 switch (action) { 618 case MEM_GOING_OFFLINE: 619 mutex_lock(&hotplug_mutex); 620 hotplug_occurred = 1; 621 ret = cmm_mem_going_offline(arg); 622 break; 623 case MEM_OFFLINE: 624 case MEM_CANCEL_OFFLINE: 625 mutex_unlock(&hotplug_mutex); 626 cmm_dbg("Memory offline operation complete.\n"); 627 break; 628 case MEM_GOING_ONLINE: 629 case MEM_ONLINE: 630 case MEM_CANCEL_ONLINE: 631 break; 632 } 633 634 return notifier_from_errno(ret); 635 } 636 637 static struct notifier_block cmm_mem_nb = { 638 .notifier_call = cmm_memory_cb, 639 .priority = CMM_MEM_HOTPLUG_PRI 640 }; 641 642 /** 643 * cmm_init - Module initialization 644 * 645 * Return value: 646 * 0 on success / other on failure 647 **/ 648 static int cmm_init(void) 649 { 650 int rc = -ENOMEM; 651 652 if (!firmware_has_feature(FW_FEATURE_CMO)) 653 return -EOPNOTSUPP; 654 655 if ((rc = register_oom_notifier(&cmm_oom_nb)) < 0) 656 return rc; 657 658 if ((rc = register_reboot_notifier(&cmm_reboot_nb))) 659 goto out_oom_notifier; 660 661 if ((rc = cmm_sysfs_register(&cmm_dev))) 662 goto out_reboot_notifier; 663 664 if (register_memory_notifier(&cmm_mem_nb) || 665 register_memory_isolate_notifier(&cmm_mem_isolate_nb)) 666 goto out_unregister_notifier; 667 668 if (cmm_disabled) 669 return rc; 670 671 cmm_thread_ptr = kthread_run(cmm_thread, NULL, "cmmthread"); 672 if (IS_ERR(cmm_thread_ptr)) { 673 rc = PTR_ERR(cmm_thread_ptr); 674 goto out_unregister_notifier; 675 } 676 677 return rc; 678 679 out_unregister_notifier: 680 unregister_memory_notifier(&cmm_mem_nb); 681 unregister_memory_isolate_notifier(&cmm_mem_isolate_nb); 682 cmm_unregister_sysfs(&cmm_dev); 683 out_reboot_notifier: 684 unregister_reboot_notifier(&cmm_reboot_nb); 685 out_oom_notifier: 686 unregister_oom_notifier(&cmm_oom_nb); 687 return rc; 688 } 689 690 /** 691 * cmm_exit - Module exit 692 * 693 * Return value: 694 * nothing 695 **/ 696 static void cmm_exit(void) 697 { 698 if (cmm_thread_ptr) 699 kthread_stop(cmm_thread_ptr); 700 unregister_oom_notifier(&cmm_oom_nb); 701 unregister_reboot_notifier(&cmm_reboot_nb); 702 unregister_memory_notifier(&cmm_mem_nb); 703 unregister_memory_isolate_notifier(&cmm_mem_isolate_nb); 704 cmm_free_pages(loaned_pages); 705 cmm_unregister_sysfs(&cmm_dev); 706 } 707 708 /** 709 * cmm_set_disable - Disable/Enable CMM 710 * 711 * Return value: 712 * 0 on success / other on failure 713 **/ 714 static int cmm_set_disable(const char *val, struct kernel_param *kp) 715 { 716 int disable = simple_strtoul(val, NULL, 10); 717 718 if (disable != 0 && disable != 1) 719 return -EINVAL; 720 721 if (disable && !cmm_disabled) { 722 if (cmm_thread_ptr) 723 kthread_stop(cmm_thread_ptr); 724 cmm_thread_ptr = NULL; 725 cmm_free_pages(loaned_pages); 726 } else if (!disable && cmm_disabled) { 727 cmm_thread_ptr = kthread_run(cmm_thread, NULL, "cmmthread"); 728 if (IS_ERR(cmm_thread_ptr)) 729 return PTR_ERR(cmm_thread_ptr); 730 } 731 732 cmm_disabled = disable; 733 return 0; 734 } 735 736 module_param_call(disable, cmm_set_disable, param_get_uint, 737 &cmm_disabled, S_IRUGO | S_IWUSR); 738 MODULE_PARM_DESC(disable, "Disable CMM. Set to 1 to disable. " 739 "[Default=" __stringify(CMM_DISABLE) "]"); 740 741 module_init(cmm_init); 742 module_exit(cmm_exit); 743