1 /* 2 * Copyright (C) 2008, 2009 Intel Corporation 3 * Authors: Andi Kleen, Fengguang Wu 4 * 5 * This software may be redistributed and/or modified under the terms of 6 * the GNU General Public License ("GPL") version 2 only as published by the 7 * Free Software Foundation. 8 * 9 * High level machine check handler. Handles pages reported by the 10 * hardware as being corrupted usually due to a multi-bit ECC memory or cache 11 * failure. 12 * 13 * In addition there is a "soft offline" entry point that allows stop using 14 * not-yet-corrupted-by-suspicious pages without killing anything. 15 * 16 * Handles page cache pages in various states. The tricky part 17 * here is that we can access any page asynchronously in respect to 18 * other VM users, because memory failures could happen anytime and 19 * anywhere. This could violate some of their assumptions. This is why 20 * this code has to be extremely careful. Generally it tries to use 21 * normal locking rules, as in get the standard locks, even if that means 22 * the error handling takes potentially a long time. 23 * 24 * It can be very tempting to add handling for obscure cases here. 25 * In general any code for handling new cases should only be added iff: 26 * - You know how to test it. 27 * - You have a test that can be added to mce-test 28 * https://git.kernel.org/cgit/utils/cpu/mce/mce-test.git/ 29 * - The case actually shows up as a frequent (top 10) page state in 30 * tools/vm/page-types when running a real workload. 31 * 32 * There are several operations here with exponential complexity because 33 * of unsuitable VM data structures. For example the operation to map back 34 * from RMAP chains to processes has to walk the complete process list and 35 * has non linear complexity with the number. But since memory corruptions 36 * are rare we hope to get away with this. This avoids impacting the core 37 * VM. 38 */ 39 #include <linux/kernel.h> 40 #include <linux/mm.h> 41 #include <linux/page-flags.h> 42 #include <linux/kernel-page-flags.h> 43 #include <linux/sched.h> 44 #include <linux/ksm.h> 45 #include <linux/rmap.h> 46 #include <linux/export.h> 47 #include <linux/pagemap.h> 48 #include <linux/swap.h> 49 #include <linux/backing-dev.h> 50 #include <linux/migrate.h> 51 #include <linux/page-isolation.h> 52 #include <linux/suspend.h> 53 #include <linux/slab.h> 54 #include <linux/swapops.h> 55 #include <linux/hugetlb.h> 56 #include <linux/memory_hotplug.h> 57 #include <linux/mm_inline.h> 58 #include <linux/kfifo.h> 59 #include <linux/ratelimit.h> 60 #include "internal.h" 61 #include "ras/ras_event.h" 62 63 int sysctl_memory_failure_early_kill __read_mostly = 0; 64 65 int sysctl_memory_failure_recovery __read_mostly = 1; 66 67 atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0); 68 69 #if defined(CONFIG_HWPOISON_INJECT) || defined(CONFIG_HWPOISON_INJECT_MODULE) 70 71 u32 hwpoison_filter_enable = 0; 72 u32 hwpoison_filter_dev_major = ~0U; 73 u32 hwpoison_filter_dev_minor = ~0U; 74 u64 hwpoison_filter_flags_mask; 75 u64 hwpoison_filter_flags_value; 76 EXPORT_SYMBOL_GPL(hwpoison_filter_enable); 77 EXPORT_SYMBOL_GPL(hwpoison_filter_dev_major); 78 EXPORT_SYMBOL_GPL(hwpoison_filter_dev_minor); 79 EXPORT_SYMBOL_GPL(hwpoison_filter_flags_mask); 80 EXPORT_SYMBOL_GPL(hwpoison_filter_flags_value); 81 82 static int hwpoison_filter_dev(struct page *p) 83 { 84 struct address_space *mapping; 85 dev_t dev; 86 87 if (hwpoison_filter_dev_major == ~0U && 88 hwpoison_filter_dev_minor == ~0U) 89 return 0; 90 91 /* 92 * page_mapping() does not accept slab pages. 93 */ 94 if (PageSlab(p)) 95 return -EINVAL; 96 97 mapping = page_mapping(p); 98 if (mapping == NULL || mapping->host == NULL) 99 return -EINVAL; 100 101 dev = mapping->host->i_sb->s_dev; 102 if (hwpoison_filter_dev_major != ~0U && 103 hwpoison_filter_dev_major != MAJOR(dev)) 104 return -EINVAL; 105 if (hwpoison_filter_dev_minor != ~0U && 106 hwpoison_filter_dev_minor != MINOR(dev)) 107 return -EINVAL; 108 109 return 0; 110 } 111 112 static int hwpoison_filter_flags(struct page *p) 113 { 114 if (!hwpoison_filter_flags_mask) 115 return 0; 116 117 if ((stable_page_flags(p) & hwpoison_filter_flags_mask) == 118 hwpoison_filter_flags_value) 119 return 0; 120 else 121 return -EINVAL; 122 } 123 124 /* 125 * This allows stress tests to limit test scope to a collection of tasks 126 * by putting them under some memcg. This prevents killing unrelated/important 127 * processes such as /sbin/init. Note that the target task may share clean 128 * pages with init (eg. libc text), which is harmless. If the target task 129 * share _dirty_ pages with another task B, the test scheme must make sure B 130 * is also included in the memcg. At last, due to race conditions this filter 131 * can only guarantee that the page either belongs to the memcg tasks, or is 132 * a freed page. 133 */ 134 #ifdef CONFIG_MEMCG 135 u64 hwpoison_filter_memcg; 136 EXPORT_SYMBOL_GPL(hwpoison_filter_memcg); 137 static int hwpoison_filter_task(struct page *p) 138 { 139 if (!hwpoison_filter_memcg) 140 return 0; 141 142 if (page_cgroup_ino(p) != hwpoison_filter_memcg) 143 return -EINVAL; 144 145 return 0; 146 } 147 #else 148 static int hwpoison_filter_task(struct page *p) { return 0; } 149 #endif 150 151 int hwpoison_filter(struct page *p) 152 { 153 if (!hwpoison_filter_enable) 154 return 0; 155 156 if (hwpoison_filter_dev(p)) 157 return -EINVAL; 158 159 if (hwpoison_filter_flags(p)) 160 return -EINVAL; 161 162 if (hwpoison_filter_task(p)) 163 return -EINVAL; 164 165 return 0; 166 } 167 #else 168 int hwpoison_filter(struct page *p) 169 { 170 return 0; 171 } 172 #endif 173 174 EXPORT_SYMBOL_GPL(hwpoison_filter); 175 176 /* 177 * Send all the processes who have the page mapped a signal. 178 * ``action optional'' if they are not immediately affected by the error 179 * ``action required'' if error happened in current execution context 180 */ 181 static int kill_proc(struct task_struct *t, unsigned long addr, int trapno, 182 unsigned long pfn, struct page *page, int flags) 183 { 184 struct siginfo si; 185 int ret; 186 187 pr_err("MCE %#lx: Killing %s:%d due to hardware memory corruption\n", 188 pfn, t->comm, t->pid); 189 si.si_signo = SIGBUS; 190 si.si_errno = 0; 191 si.si_addr = (void *)addr; 192 #ifdef __ARCH_SI_TRAPNO 193 si.si_trapno = trapno; 194 #endif 195 si.si_addr_lsb = compound_order(compound_head(page)) + PAGE_SHIFT; 196 197 if ((flags & MF_ACTION_REQUIRED) && t->mm == current->mm) { 198 si.si_code = BUS_MCEERR_AR; 199 ret = force_sig_info(SIGBUS, &si, current); 200 } else { 201 /* 202 * Don't use force here, it's convenient if the signal 203 * can be temporarily blocked. 204 * This could cause a loop when the user sets SIGBUS 205 * to SIG_IGN, but hopefully no one will do that? 206 */ 207 si.si_code = BUS_MCEERR_AO; 208 ret = send_sig_info(SIGBUS, &si, t); /* synchronous? */ 209 } 210 if (ret < 0) 211 pr_info("MCE: Error sending signal to %s:%d: %d\n", 212 t->comm, t->pid, ret); 213 return ret; 214 } 215 216 /* 217 * When a unknown page type is encountered drain as many buffers as possible 218 * in the hope to turn the page into a LRU or free page, which we can handle. 219 */ 220 void shake_page(struct page *p, int access) 221 { 222 if (!PageSlab(p)) { 223 lru_add_drain_all(); 224 if (PageLRU(p)) 225 return; 226 drain_all_pages(page_zone(p)); 227 if (PageLRU(p) || is_free_buddy_page(p)) 228 return; 229 } 230 231 /* 232 * Only call shrink_node_slabs here (which would also shrink 233 * other caches) if access is not potentially fatal. 234 */ 235 if (access) 236 drop_slab_node(page_to_nid(p)); 237 } 238 EXPORT_SYMBOL_GPL(shake_page); 239 240 /* 241 * Kill all processes that have a poisoned page mapped and then isolate 242 * the page. 243 * 244 * General strategy: 245 * Find all processes having the page mapped and kill them. 246 * But we keep a page reference around so that the page is not 247 * actually freed yet. 248 * Then stash the page away 249 * 250 * There's no convenient way to get back to mapped processes 251 * from the VMAs. So do a brute-force search over all 252 * running processes. 253 * 254 * Remember that machine checks are not common (or rather 255 * if they are common you have other problems), so this shouldn't 256 * be a performance issue. 257 * 258 * Also there are some races possible while we get from the 259 * error detection to actually handle it. 260 */ 261 262 struct to_kill { 263 struct list_head nd; 264 struct task_struct *tsk; 265 unsigned long addr; 266 char addr_valid; 267 }; 268 269 /* 270 * Failure handling: if we can't find or can't kill a process there's 271 * not much we can do. We just print a message and ignore otherwise. 272 */ 273 274 /* 275 * Schedule a process for later kill. 276 * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM. 277 * TBD would GFP_NOIO be enough? 278 */ 279 static void add_to_kill(struct task_struct *tsk, struct page *p, 280 struct vm_area_struct *vma, 281 struct list_head *to_kill, 282 struct to_kill **tkc) 283 { 284 struct to_kill *tk; 285 286 if (*tkc) { 287 tk = *tkc; 288 *tkc = NULL; 289 } else { 290 tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC); 291 if (!tk) { 292 pr_err("MCE: Out of memory while machine check handling\n"); 293 return; 294 } 295 } 296 tk->addr = page_address_in_vma(p, vma); 297 tk->addr_valid = 1; 298 299 /* 300 * In theory we don't have to kill when the page was 301 * munmaped. But it could be also a mremap. Since that's 302 * likely very rare kill anyways just out of paranoia, but use 303 * a SIGKILL because the error is not contained anymore. 304 */ 305 if (tk->addr == -EFAULT) { 306 pr_info("MCE: Unable to find user space address %lx in %s\n", 307 page_to_pfn(p), tsk->comm); 308 tk->addr_valid = 0; 309 } 310 get_task_struct(tsk); 311 tk->tsk = tsk; 312 list_add_tail(&tk->nd, to_kill); 313 } 314 315 /* 316 * Kill the processes that have been collected earlier. 317 * 318 * Only do anything when DOIT is set, otherwise just free the list 319 * (this is used for clean pages which do not need killing) 320 * Also when FAIL is set do a force kill because something went 321 * wrong earlier. 322 */ 323 static void kill_procs(struct list_head *to_kill, int forcekill, int trapno, 324 int fail, struct page *page, unsigned long pfn, 325 int flags) 326 { 327 struct to_kill *tk, *next; 328 329 list_for_each_entry_safe (tk, next, to_kill, nd) { 330 if (forcekill) { 331 /* 332 * In case something went wrong with munmapping 333 * make sure the process doesn't catch the 334 * signal and then access the memory. Just kill it. 335 */ 336 if (fail || tk->addr_valid == 0) { 337 pr_err("MCE %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n", 338 pfn, tk->tsk->comm, tk->tsk->pid); 339 force_sig(SIGKILL, tk->tsk); 340 } 341 342 /* 343 * In theory the process could have mapped 344 * something else on the address in-between. We could 345 * check for that, but we need to tell the 346 * process anyways. 347 */ 348 else if (kill_proc(tk->tsk, tk->addr, trapno, 349 pfn, page, flags) < 0) 350 pr_err("MCE %#lx: Cannot send advisory machine check signal to %s:%d\n", 351 pfn, tk->tsk->comm, tk->tsk->pid); 352 } 353 put_task_struct(tk->tsk); 354 kfree(tk); 355 } 356 } 357 358 /* 359 * Find a dedicated thread which is supposed to handle SIGBUS(BUS_MCEERR_AO) 360 * on behalf of the thread group. Return task_struct of the (first found) 361 * dedicated thread if found, and return NULL otherwise. 362 * 363 * We already hold read_lock(&tasklist_lock) in the caller, so we don't 364 * have to call rcu_read_lock/unlock() in this function. 365 */ 366 static struct task_struct *find_early_kill_thread(struct task_struct *tsk) 367 { 368 struct task_struct *t; 369 370 for_each_thread(tsk, t) 371 if ((t->flags & PF_MCE_PROCESS) && (t->flags & PF_MCE_EARLY)) 372 return t; 373 return NULL; 374 } 375 376 /* 377 * Determine whether a given process is "early kill" process which expects 378 * to be signaled when some page under the process is hwpoisoned. 379 * Return task_struct of the dedicated thread (main thread unless explicitly 380 * specified) if the process is "early kill," and otherwise returns NULL. 381 */ 382 static struct task_struct *task_early_kill(struct task_struct *tsk, 383 int force_early) 384 { 385 struct task_struct *t; 386 if (!tsk->mm) 387 return NULL; 388 if (force_early) 389 return tsk; 390 t = find_early_kill_thread(tsk); 391 if (t) 392 return t; 393 if (sysctl_memory_failure_early_kill) 394 return tsk; 395 return NULL; 396 } 397 398 /* 399 * Collect processes when the error hit an anonymous page. 400 */ 401 static void collect_procs_anon(struct page *page, struct list_head *to_kill, 402 struct to_kill **tkc, int force_early) 403 { 404 struct vm_area_struct *vma; 405 struct task_struct *tsk; 406 struct anon_vma *av; 407 pgoff_t pgoff; 408 409 av = page_lock_anon_vma_read(page); 410 if (av == NULL) /* Not actually mapped anymore */ 411 return; 412 413 pgoff = page_to_pgoff(page); 414 read_lock(&tasklist_lock); 415 for_each_process (tsk) { 416 struct anon_vma_chain *vmac; 417 struct task_struct *t = task_early_kill(tsk, force_early); 418 419 if (!t) 420 continue; 421 anon_vma_interval_tree_foreach(vmac, &av->rb_root, 422 pgoff, pgoff) { 423 vma = vmac->vma; 424 if (!page_mapped_in_vma(page, vma)) 425 continue; 426 if (vma->vm_mm == t->mm) 427 add_to_kill(t, page, vma, to_kill, tkc); 428 } 429 } 430 read_unlock(&tasklist_lock); 431 page_unlock_anon_vma_read(av); 432 } 433 434 /* 435 * Collect processes when the error hit a file mapped page. 436 */ 437 static void collect_procs_file(struct page *page, struct list_head *to_kill, 438 struct to_kill **tkc, int force_early) 439 { 440 struct vm_area_struct *vma; 441 struct task_struct *tsk; 442 struct address_space *mapping = page->mapping; 443 444 i_mmap_lock_read(mapping); 445 read_lock(&tasklist_lock); 446 for_each_process(tsk) { 447 pgoff_t pgoff = page_to_pgoff(page); 448 struct task_struct *t = task_early_kill(tsk, force_early); 449 450 if (!t) 451 continue; 452 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, 453 pgoff) { 454 /* 455 * Send early kill signal to tasks where a vma covers 456 * the page but the corrupted page is not necessarily 457 * mapped it in its pte. 458 * Assume applications who requested early kill want 459 * to be informed of all such data corruptions. 460 */ 461 if (vma->vm_mm == t->mm) 462 add_to_kill(t, page, vma, to_kill, tkc); 463 } 464 } 465 read_unlock(&tasklist_lock); 466 i_mmap_unlock_read(mapping); 467 } 468 469 /* 470 * Collect the processes who have the corrupted page mapped to kill. 471 * This is done in two steps for locking reasons. 472 * First preallocate one tokill structure outside the spin locks, 473 * so that we can kill at least one process reasonably reliable. 474 */ 475 static void collect_procs(struct page *page, struct list_head *tokill, 476 int force_early) 477 { 478 struct to_kill *tk; 479 480 if (!page->mapping) 481 return; 482 483 tk = kmalloc(sizeof(struct to_kill), GFP_NOIO); 484 if (!tk) 485 return; 486 if (PageAnon(page)) 487 collect_procs_anon(page, tokill, &tk, force_early); 488 else 489 collect_procs_file(page, tokill, &tk, force_early); 490 kfree(tk); 491 } 492 493 static const char *action_name[] = { 494 [MF_IGNORED] = "Ignored", 495 [MF_FAILED] = "Failed", 496 [MF_DELAYED] = "Delayed", 497 [MF_RECOVERED] = "Recovered", 498 }; 499 500 static const char * const action_page_types[] = { 501 [MF_MSG_KERNEL] = "reserved kernel page", 502 [MF_MSG_KERNEL_HIGH_ORDER] = "high-order kernel page", 503 [MF_MSG_SLAB] = "kernel slab page", 504 [MF_MSG_DIFFERENT_COMPOUND] = "different compound page after locking", 505 [MF_MSG_POISONED_HUGE] = "huge page already hardware poisoned", 506 [MF_MSG_HUGE] = "huge page", 507 [MF_MSG_FREE_HUGE] = "free huge page", 508 [MF_MSG_UNMAP_FAILED] = "unmapping failed page", 509 [MF_MSG_DIRTY_SWAPCACHE] = "dirty swapcache page", 510 [MF_MSG_CLEAN_SWAPCACHE] = "clean swapcache page", 511 [MF_MSG_DIRTY_MLOCKED_LRU] = "dirty mlocked LRU page", 512 [MF_MSG_CLEAN_MLOCKED_LRU] = "clean mlocked LRU page", 513 [MF_MSG_DIRTY_UNEVICTABLE_LRU] = "dirty unevictable LRU page", 514 [MF_MSG_CLEAN_UNEVICTABLE_LRU] = "clean unevictable LRU page", 515 [MF_MSG_DIRTY_LRU] = "dirty LRU page", 516 [MF_MSG_CLEAN_LRU] = "clean LRU page", 517 [MF_MSG_TRUNCATED_LRU] = "already truncated LRU page", 518 [MF_MSG_BUDDY] = "free buddy page", 519 [MF_MSG_BUDDY_2ND] = "free buddy page (2nd try)", 520 [MF_MSG_UNKNOWN] = "unknown page", 521 }; 522 523 /* 524 * XXX: It is possible that a page is isolated from LRU cache, 525 * and then kept in swap cache or failed to remove from page cache. 526 * The page count will stop it from being freed by unpoison. 527 * Stress tests should be aware of this memory leak problem. 528 */ 529 static int delete_from_lru_cache(struct page *p) 530 { 531 if (!isolate_lru_page(p)) { 532 /* 533 * Clear sensible page flags, so that the buddy system won't 534 * complain when the page is unpoison-and-freed. 535 */ 536 ClearPageActive(p); 537 ClearPageUnevictable(p); 538 /* 539 * drop the page count elevated by isolate_lru_page() 540 */ 541 put_page(p); 542 return 0; 543 } 544 return -EIO; 545 } 546 547 /* 548 * Error hit kernel page. 549 * Do nothing, try to be lucky and not touch this instead. For a few cases we 550 * could be more sophisticated. 551 */ 552 static int me_kernel(struct page *p, unsigned long pfn) 553 { 554 return MF_IGNORED; 555 } 556 557 /* 558 * Page in unknown state. Do nothing. 559 */ 560 static int me_unknown(struct page *p, unsigned long pfn) 561 { 562 pr_err("MCE %#lx: Unknown page state\n", pfn); 563 return MF_FAILED; 564 } 565 566 /* 567 * Clean (or cleaned) page cache page. 568 */ 569 static int me_pagecache_clean(struct page *p, unsigned long pfn) 570 { 571 int err; 572 int ret = MF_FAILED; 573 struct address_space *mapping; 574 575 delete_from_lru_cache(p); 576 577 /* 578 * For anonymous pages we're done the only reference left 579 * should be the one m_f() holds. 580 */ 581 if (PageAnon(p)) 582 return MF_RECOVERED; 583 584 /* 585 * Now truncate the page in the page cache. This is really 586 * more like a "temporary hole punch" 587 * Don't do this for block devices when someone else 588 * has a reference, because it could be file system metadata 589 * and that's not safe to truncate. 590 */ 591 mapping = page_mapping(p); 592 if (!mapping) { 593 /* 594 * Page has been teared down in the meanwhile 595 */ 596 return MF_FAILED; 597 } 598 599 /* 600 * Truncation is a bit tricky. Enable it per file system for now. 601 * 602 * Open: to take i_mutex or not for this? Right now we don't. 603 */ 604 if (mapping->a_ops->error_remove_page) { 605 err = mapping->a_ops->error_remove_page(mapping, p); 606 if (err != 0) { 607 pr_info("MCE %#lx: Failed to punch page: %d\n", 608 pfn, err); 609 } else if (page_has_private(p) && 610 !try_to_release_page(p, GFP_NOIO)) { 611 pr_info("MCE %#lx: failed to release buffers\n", pfn); 612 } else { 613 ret = MF_RECOVERED; 614 } 615 } else { 616 /* 617 * If the file system doesn't support it just invalidate 618 * This fails on dirty or anything with private pages 619 */ 620 if (invalidate_inode_page(p)) 621 ret = MF_RECOVERED; 622 else 623 pr_info("MCE %#lx: Failed to invalidate\n", pfn); 624 } 625 return ret; 626 } 627 628 /* 629 * Dirty pagecache page 630 * Issues: when the error hit a hole page the error is not properly 631 * propagated. 632 */ 633 static int me_pagecache_dirty(struct page *p, unsigned long pfn) 634 { 635 struct address_space *mapping = page_mapping(p); 636 637 SetPageError(p); 638 /* TBD: print more information about the file. */ 639 if (mapping) { 640 /* 641 * IO error will be reported by write(), fsync(), etc. 642 * who check the mapping. 643 * This way the application knows that something went 644 * wrong with its dirty file data. 645 * 646 * There's one open issue: 647 * 648 * The EIO will be only reported on the next IO 649 * operation and then cleared through the IO map. 650 * Normally Linux has two mechanisms to pass IO error 651 * first through the AS_EIO flag in the address space 652 * and then through the PageError flag in the page. 653 * Since we drop pages on memory failure handling the 654 * only mechanism open to use is through AS_AIO. 655 * 656 * This has the disadvantage that it gets cleared on 657 * the first operation that returns an error, while 658 * the PageError bit is more sticky and only cleared 659 * when the page is reread or dropped. If an 660 * application assumes it will always get error on 661 * fsync, but does other operations on the fd before 662 * and the page is dropped between then the error 663 * will not be properly reported. 664 * 665 * This can already happen even without hwpoisoned 666 * pages: first on metadata IO errors (which only 667 * report through AS_EIO) or when the page is dropped 668 * at the wrong time. 669 * 670 * So right now we assume that the application DTRT on 671 * the first EIO, but we're not worse than other parts 672 * of the kernel. 673 */ 674 mapping_set_error(mapping, EIO); 675 } 676 677 return me_pagecache_clean(p, pfn); 678 } 679 680 /* 681 * Clean and dirty swap cache. 682 * 683 * Dirty swap cache page is tricky to handle. The page could live both in page 684 * cache and swap cache(ie. page is freshly swapped in). So it could be 685 * referenced concurrently by 2 types of PTEs: 686 * normal PTEs and swap PTEs. We try to handle them consistently by calling 687 * try_to_unmap(TTU_IGNORE_HWPOISON) to convert the normal PTEs to swap PTEs, 688 * and then 689 * - clear dirty bit to prevent IO 690 * - remove from LRU 691 * - but keep in the swap cache, so that when we return to it on 692 * a later page fault, we know the application is accessing 693 * corrupted data and shall be killed (we installed simple 694 * interception code in do_swap_page to catch it). 695 * 696 * Clean swap cache pages can be directly isolated. A later page fault will 697 * bring in the known good data from disk. 698 */ 699 static int me_swapcache_dirty(struct page *p, unsigned long pfn) 700 { 701 ClearPageDirty(p); 702 /* Trigger EIO in shmem: */ 703 ClearPageUptodate(p); 704 705 if (!delete_from_lru_cache(p)) 706 return MF_DELAYED; 707 else 708 return MF_FAILED; 709 } 710 711 static int me_swapcache_clean(struct page *p, unsigned long pfn) 712 { 713 delete_from_swap_cache(p); 714 715 if (!delete_from_lru_cache(p)) 716 return MF_RECOVERED; 717 else 718 return MF_FAILED; 719 } 720 721 /* 722 * Huge pages. Needs work. 723 * Issues: 724 * - Error on hugepage is contained in hugepage unit (not in raw page unit.) 725 * To narrow down kill region to one page, we need to break up pmd. 726 */ 727 static int me_huge_page(struct page *p, unsigned long pfn) 728 { 729 int res = 0; 730 struct page *hpage = compound_head(p); 731 732 if (!PageHuge(hpage)) 733 return MF_DELAYED; 734 735 /* 736 * We can safely recover from error on free or reserved (i.e. 737 * not in-use) hugepage by dequeuing it from freelist. 738 * To check whether a hugepage is in-use or not, we can't use 739 * page->lru because it can be used in other hugepage operations, 740 * such as __unmap_hugepage_range() and gather_surplus_pages(). 741 * So instead we use page_mapping() and PageAnon(). 742 * We assume that this function is called with page lock held, 743 * so there is no race between isolation and mapping/unmapping. 744 */ 745 if (!(page_mapping(hpage) || PageAnon(hpage))) { 746 res = dequeue_hwpoisoned_huge_page(hpage); 747 if (!res) 748 return MF_RECOVERED; 749 } 750 return MF_DELAYED; 751 } 752 753 /* 754 * Various page states we can handle. 755 * 756 * A page state is defined by its current page->flags bits. 757 * The table matches them in order and calls the right handler. 758 * 759 * This is quite tricky because we can access page at any time 760 * in its live cycle, so all accesses have to be extremely careful. 761 * 762 * This is not complete. More states could be added. 763 * For any missing state don't attempt recovery. 764 */ 765 766 #define dirty (1UL << PG_dirty) 767 #define sc (1UL << PG_swapcache) 768 #define unevict (1UL << PG_unevictable) 769 #define mlock (1UL << PG_mlocked) 770 #define writeback (1UL << PG_writeback) 771 #define lru (1UL << PG_lru) 772 #define swapbacked (1UL << PG_swapbacked) 773 #define head (1UL << PG_head) 774 #define slab (1UL << PG_slab) 775 #define reserved (1UL << PG_reserved) 776 777 static struct page_state { 778 unsigned long mask; 779 unsigned long res; 780 enum mf_action_page_type type; 781 int (*action)(struct page *p, unsigned long pfn); 782 } error_states[] = { 783 { reserved, reserved, MF_MSG_KERNEL, me_kernel }, 784 /* 785 * free pages are specially detected outside this table: 786 * PG_buddy pages only make a small fraction of all free pages. 787 */ 788 789 /* 790 * Could in theory check if slab page is free or if we can drop 791 * currently unused objects without touching them. But just 792 * treat it as standard kernel for now. 793 */ 794 { slab, slab, MF_MSG_SLAB, me_kernel }, 795 796 { head, head, MF_MSG_HUGE, me_huge_page }, 797 798 { sc|dirty, sc|dirty, MF_MSG_DIRTY_SWAPCACHE, me_swapcache_dirty }, 799 { sc|dirty, sc, MF_MSG_CLEAN_SWAPCACHE, me_swapcache_clean }, 800 801 { mlock|dirty, mlock|dirty, MF_MSG_DIRTY_MLOCKED_LRU, me_pagecache_dirty }, 802 { mlock|dirty, mlock, MF_MSG_CLEAN_MLOCKED_LRU, me_pagecache_clean }, 803 804 { unevict|dirty, unevict|dirty, MF_MSG_DIRTY_UNEVICTABLE_LRU, me_pagecache_dirty }, 805 { unevict|dirty, unevict, MF_MSG_CLEAN_UNEVICTABLE_LRU, me_pagecache_clean }, 806 807 { lru|dirty, lru|dirty, MF_MSG_DIRTY_LRU, me_pagecache_dirty }, 808 { lru|dirty, lru, MF_MSG_CLEAN_LRU, me_pagecache_clean }, 809 810 /* 811 * Catchall entry: must be at end. 812 */ 813 { 0, 0, MF_MSG_UNKNOWN, me_unknown }, 814 }; 815 816 #undef dirty 817 #undef sc 818 #undef unevict 819 #undef mlock 820 #undef writeback 821 #undef lru 822 #undef swapbacked 823 #undef head 824 #undef slab 825 #undef reserved 826 827 /* 828 * "Dirty/Clean" indication is not 100% accurate due to the possibility of 829 * setting PG_dirty outside page lock. See also comment above set_page_dirty(). 830 */ 831 static void action_result(unsigned long pfn, enum mf_action_page_type type, 832 enum mf_result result) 833 { 834 trace_memory_failure_event(pfn, type, result); 835 836 pr_err("MCE %#lx: recovery action for %s: %s\n", 837 pfn, action_page_types[type], action_name[result]); 838 } 839 840 static int page_action(struct page_state *ps, struct page *p, 841 unsigned long pfn) 842 { 843 int result; 844 int count; 845 846 result = ps->action(p, pfn); 847 848 count = page_count(p) - 1; 849 if (ps->action == me_swapcache_dirty && result == MF_DELAYED) 850 count--; 851 if (count != 0) { 852 pr_err("MCE %#lx: %s still referenced by %d users\n", 853 pfn, action_page_types[ps->type], count); 854 result = MF_FAILED; 855 } 856 action_result(pfn, ps->type, result); 857 858 /* Could do more checks here if page looks ok */ 859 /* 860 * Could adjust zone counters here to correct for the missing page. 861 */ 862 863 return (result == MF_RECOVERED || result == MF_DELAYED) ? 0 : -EBUSY; 864 } 865 866 /** 867 * get_hwpoison_page() - Get refcount for memory error handling: 868 * @page: raw error page (hit by memory error) 869 * 870 * Return: return 0 if failed to grab the refcount, otherwise true (some 871 * non-zero value.) 872 */ 873 int get_hwpoison_page(struct page *page) 874 { 875 struct page *head = compound_head(page); 876 877 if (!PageHuge(head) && PageTransHuge(head)) { 878 /* 879 * Non anonymous thp exists only in allocation/free time. We 880 * can't handle such a case correctly, so let's give it up. 881 * This should be better than triggering BUG_ON when kernel 882 * tries to touch the "partially handled" page. 883 */ 884 if (!PageAnon(head)) { 885 pr_err("MCE: %#lx: non anonymous thp\n", 886 page_to_pfn(page)); 887 return 0; 888 } 889 } 890 891 if (get_page_unless_zero(head)) { 892 if (head == compound_head(page)) 893 return 1; 894 895 pr_info("MCE: %#lx cannot catch tail\n", page_to_pfn(page)); 896 put_page(head); 897 } 898 899 return 0; 900 } 901 EXPORT_SYMBOL_GPL(get_hwpoison_page); 902 903 /* 904 * Do all that is necessary to remove user space mappings. Unmap 905 * the pages and send SIGBUS to the processes if the data was dirty. 906 */ 907 static int hwpoison_user_mappings(struct page *p, unsigned long pfn, 908 int trapno, int flags, struct page **hpagep) 909 { 910 enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS; 911 struct address_space *mapping; 912 LIST_HEAD(tokill); 913 int ret; 914 int kill = 1, forcekill; 915 struct page *hpage = *hpagep; 916 917 /* 918 * Here we are interested only in user-mapped pages, so skip any 919 * other types of pages. 920 */ 921 if (PageReserved(p) || PageSlab(p)) 922 return SWAP_SUCCESS; 923 if (!(PageLRU(hpage) || PageHuge(p))) 924 return SWAP_SUCCESS; 925 926 /* 927 * This check implies we don't kill processes if their pages 928 * are in the swap cache early. Those are always late kills. 929 */ 930 if (!page_mapped(hpage)) 931 return SWAP_SUCCESS; 932 933 if (PageKsm(p)) { 934 pr_err("MCE %#lx: can't handle KSM pages.\n", pfn); 935 return SWAP_FAIL; 936 } 937 938 if (PageSwapCache(p)) { 939 pr_err("MCE %#lx: keeping poisoned page in swap cache\n", pfn); 940 ttu |= TTU_IGNORE_HWPOISON; 941 } 942 943 /* 944 * Propagate the dirty bit from PTEs to struct page first, because we 945 * need this to decide if we should kill or just drop the page. 946 * XXX: the dirty test could be racy: set_page_dirty() may not always 947 * be called inside page lock (it's recommended but not enforced). 948 */ 949 mapping = page_mapping(hpage); 950 if (!(flags & MF_MUST_KILL) && !PageDirty(hpage) && mapping && 951 mapping_cap_writeback_dirty(mapping)) { 952 if (page_mkclean(hpage)) { 953 SetPageDirty(hpage); 954 } else { 955 kill = 0; 956 ttu |= TTU_IGNORE_HWPOISON; 957 pr_info("MCE %#lx: corrupted page was clean: dropped without side effects\n", 958 pfn); 959 } 960 } 961 962 /* 963 * First collect all the processes that have the page 964 * mapped in dirty form. This has to be done before try_to_unmap, 965 * because ttu takes the rmap data structures down. 966 * 967 * Error handling: We ignore errors here because 968 * there's nothing that can be done. 969 */ 970 if (kill) 971 collect_procs(hpage, &tokill, flags & MF_ACTION_REQUIRED); 972 973 ret = try_to_unmap(hpage, ttu); 974 if (ret != SWAP_SUCCESS) 975 pr_err("MCE %#lx: failed to unmap page (mapcount=%d)\n", 976 pfn, page_mapcount(hpage)); 977 978 /* 979 * Now that the dirty bit has been propagated to the 980 * struct page and all unmaps done we can decide if 981 * killing is needed or not. Only kill when the page 982 * was dirty or the process is not restartable, 983 * otherwise the tokill list is merely 984 * freed. When there was a problem unmapping earlier 985 * use a more force-full uncatchable kill to prevent 986 * any accesses to the poisoned memory. 987 */ 988 forcekill = PageDirty(hpage) || (flags & MF_MUST_KILL); 989 kill_procs(&tokill, forcekill, trapno, 990 ret != SWAP_SUCCESS, p, pfn, flags); 991 992 return ret; 993 } 994 995 static void set_page_hwpoison_huge_page(struct page *hpage) 996 { 997 int i; 998 int nr_pages = 1 << compound_order(hpage); 999 for (i = 0; i < nr_pages; i++) 1000 SetPageHWPoison(hpage + i); 1001 } 1002 1003 static void clear_page_hwpoison_huge_page(struct page *hpage) 1004 { 1005 int i; 1006 int nr_pages = 1 << compound_order(hpage); 1007 for (i = 0; i < nr_pages; i++) 1008 ClearPageHWPoison(hpage + i); 1009 } 1010 1011 /** 1012 * memory_failure - Handle memory failure of a page. 1013 * @pfn: Page Number of the corrupted page 1014 * @trapno: Trap number reported in the signal to user space. 1015 * @flags: fine tune action taken 1016 * 1017 * This function is called by the low level machine check code 1018 * of an architecture when it detects hardware memory corruption 1019 * of a page. It tries its best to recover, which includes 1020 * dropping pages, killing processes etc. 1021 * 1022 * The function is primarily of use for corruptions that 1023 * happen outside the current execution context (e.g. when 1024 * detected by a background scrubber) 1025 * 1026 * Must run in process context (e.g. a work queue) with interrupts 1027 * enabled and no spinlocks hold. 1028 */ 1029 int memory_failure(unsigned long pfn, int trapno, int flags) 1030 { 1031 struct page_state *ps; 1032 struct page *p; 1033 struct page *hpage; 1034 struct page *orig_head; 1035 int res; 1036 unsigned int nr_pages; 1037 unsigned long page_flags; 1038 1039 if (!sysctl_memory_failure_recovery) 1040 panic("Memory failure from trap %d on page %lx", trapno, pfn); 1041 1042 if (!pfn_valid(pfn)) { 1043 pr_err("MCE %#lx: memory outside kernel control\n", pfn); 1044 return -ENXIO; 1045 } 1046 1047 p = pfn_to_page(pfn); 1048 orig_head = hpage = compound_head(p); 1049 if (TestSetPageHWPoison(p)) { 1050 pr_err("MCE %#lx: already hardware poisoned\n", pfn); 1051 return 0; 1052 } 1053 1054 /* 1055 * Currently errors on hugetlbfs pages are measured in hugepage units, 1056 * so nr_pages should be 1 << compound_order. OTOH when errors are on 1057 * transparent hugepages, they are supposed to be split and error 1058 * measurement is done in normal page units. So nr_pages should be one 1059 * in this case. 1060 */ 1061 if (PageHuge(p)) 1062 nr_pages = 1 << compound_order(hpage); 1063 else /* normal page or thp */ 1064 nr_pages = 1; 1065 num_poisoned_pages_add(nr_pages); 1066 1067 /* 1068 * We need/can do nothing about count=0 pages. 1069 * 1) it's a free page, and therefore in safe hand: 1070 * prep_new_page() will be the gate keeper. 1071 * 2) it's a free hugepage, which is also safe: 1072 * an affected hugepage will be dequeued from hugepage freelist, 1073 * so there's no concern about reusing it ever after. 1074 * 3) it's part of a non-compound high order page. 1075 * Implies some kernel user: cannot stop them from 1076 * R/W the page; let's pray that the page has been 1077 * used and will be freed some time later. 1078 * In fact it's dangerous to directly bump up page count from 0, 1079 * that may make page_freeze_refs()/page_unfreeze_refs() mismatch. 1080 */ 1081 if (!(flags & MF_COUNT_INCREASED) && !get_hwpoison_page(p)) { 1082 if (is_free_buddy_page(p)) { 1083 action_result(pfn, MF_MSG_BUDDY, MF_DELAYED); 1084 return 0; 1085 } else if (PageHuge(hpage)) { 1086 /* 1087 * Check "filter hit" and "race with other subpage." 1088 */ 1089 lock_page(hpage); 1090 if (PageHWPoison(hpage)) { 1091 if ((hwpoison_filter(p) && TestClearPageHWPoison(p)) 1092 || (p != hpage && TestSetPageHWPoison(hpage))) { 1093 num_poisoned_pages_sub(nr_pages); 1094 unlock_page(hpage); 1095 return 0; 1096 } 1097 } 1098 set_page_hwpoison_huge_page(hpage); 1099 res = dequeue_hwpoisoned_huge_page(hpage); 1100 action_result(pfn, MF_MSG_FREE_HUGE, 1101 res ? MF_IGNORED : MF_DELAYED); 1102 unlock_page(hpage); 1103 return res; 1104 } else { 1105 action_result(pfn, MF_MSG_KERNEL_HIGH_ORDER, MF_IGNORED); 1106 return -EBUSY; 1107 } 1108 } 1109 1110 if (!PageHuge(p) && PageTransHuge(hpage)) { 1111 lock_page(hpage); 1112 if (!PageAnon(hpage) || unlikely(split_huge_page(hpage))) { 1113 unlock_page(hpage); 1114 if (!PageAnon(hpage)) 1115 pr_err("MCE: %#lx: non anonymous thp\n", pfn); 1116 else 1117 pr_err("MCE: %#lx: thp split failed\n", pfn); 1118 if (TestClearPageHWPoison(p)) 1119 num_poisoned_pages_sub(nr_pages); 1120 put_hwpoison_page(p); 1121 return -EBUSY; 1122 } 1123 unlock_page(hpage); 1124 get_hwpoison_page(p); 1125 put_hwpoison_page(hpage); 1126 VM_BUG_ON_PAGE(!page_count(p), p); 1127 hpage = compound_head(p); 1128 } 1129 1130 /* 1131 * We ignore non-LRU pages for good reasons. 1132 * - PG_locked is only well defined for LRU pages and a few others 1133 * - to avoid races with __SetPageLocked() 1134 * - to avoid races with __SetPageSlab*() (and more non-atomic ops) 1135 * The check (unnecessarily) ignores LRU pages being isolated and 1136 * walked by the page reclaim code, however that's not a big loss. 1137 */ 1138 if (!PageHuge(p)) { 1139 if (!PageLRU(p)) 1140 shake_page(p, 0); 1141 if (!PageLRU(p)) { 1142 /* 1143 * shake_page could have turned it free. 1144 */ 1145 if (is_free_buddy_page(p)) { 1146 if (flags & MF_COUNT_INCREASED) 1147 action_result(pfn, MF_MSG_BUDDY, MF_DELAYED); 1148 else 1149 action_result(pfn, MF_MSG_BUDDY_2ND, 1150 MF_DELAYED); 1151 return 0; 1152 } 1153 } 1154 } 1155 1156 lock_page(hpage); 1157 1158 /* 1159 * The page could have changed compound pages during the locking. 1160 * If this happens just bail out. 1161 */ 1162 if (PageCompound(p) && compound_head(p) != orig_head) { 1163 action_result(pfn, MF_MSG_DIFFERENT_COMPOUND, MF_IGNORED); 1164 res = -EBUSY; 1165 goto out; 1166 } 1167 1168 /* 1169 * We use page flags to determine what action should be taken, but 1170 * the flags can be modified by the error containment action. One 1171 * example is an mlocked page, where PG_mlocked is cleared by 1172 * page_remove_rmap() in try_to_unmap_one(). So to determine page status 1173 * correctly, we save a copy of the page flags at this time. 1174 */ 1175 page_flags = p->flags; 1176 1177 /* 1178 * unpoison always clear PG_hwpoison inside page lock 1179 */ 1180 if (!PageHWPoison(p)) { 1181 pr_err("MCE %#lx: just unpoisoned\n", pfn); 1182 num_poisoned_pages_sub(nr_pages); 1183 unlock_page(hpage); 1184 put_hwpoison_page(hpage); 1185 return 0; 1186 } 1187 if (hwpoison_filter(p)) { 1188 if (TestClearPageHWPoison(p)) 1189 num_poisoned_pages_sub(nr_pages); 1190 unlock_page(hpage); 1191 put_hwpoison_page(hpage); 1192 return 0; 1193 } 1194 1195 if (!PageHuge(p) && !PageTransTail(p) && !PageLRU(p)) 1196 goto identify_page_state; 1197 1198 /* 1199 * For error on the tail page, we should set PG_hwpoison 1200 * on the head page to show that the hugepage is hwpoisoned 1201 */ 1202 if (PageHuge(p) && PageTail(p) && TestSetPageHWPoison(hpage)) { 1203 action_result(pfn, MF_MSG_POISONED_HUGE, MF_IGNORED); 1204 unlock_page(hpage); 1205 put_hwpoison_page(hpage); 1206 return 0; 1207 } 1208 /* 1209 * Set PG_hwpoison on all pages in an error hugepage, 1210 * because containment is done in hugepage unit for now. 1211 * Since we have done TestSetPageHWPoison() for the head page with 1212 * page lock held, we can safely set PG_hwpoison bits on tail pages. 1213 */ 1214 if (PageHuge(p)) 1215 set_page_hwpoison_huge_page(hpage); 1216 1217 /* 1218 * It's very difficult to mess with pages currently under IO 1219 * and in many cases impossible, so we just avoid it here. 1220 */ 1221 wait_on_page_writeback(p); 1222 1223 /* 1224 * Now take care of user space mappings. 1225 * Abort on fail: __delete_from_page_cache() assumes unmapped page. 1226 * 1227 * When the raw error page is thp tail page, hpage points to the raw 1228 * page after thp split. 1229 */ 1230 if (hwpoison_user_mappings(p, pfn, trapno, flags, &hpage) 1231 != SWAP_SUCCESS) { 1232 action_result(pfn, MF_MSG_UNMAP_FAILED, MF_IGNORED); 1233 res = -EBUSY; 1234 goto out; 1235 } 1236 1237 /* 1238 * Torn down by someone else? 1239 */ 1240 if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) { 1241 action_result(pfn, MF_MSG_TRUNCATED_LRU, MF_IGNORED); 1242 res = -EBUSY; 1243 goto out; 1244 } 1245 1246 identify_page_state: 1247 res = -EBUSY; 1248 /* 1249 * The first check uses the current page flags which may not have any 1250 * relevant information. The second check with the saved page flagss is 1251 * carried out only if the first check can't determine the page status. 1252 */ 1253 for (ps = error_states;; ps++) 1254 if ((p->flags & ps->mask) == ps->res) 1255 break; 1256 1257 page_flags |= (p->flags & (1UL << PG_dirty)); 1258 1259 if (!ps->mask) 1260 for (ps = error_states;; ps++) 1261 if ((page_flags & ps->mask) == ps->res) 1262 break; 1263 res = page_action(ps, p, pfn); 1264 out: 1265 unlock_page(hpage); 1266 return res; 1267 } 1268 EXPORT_SYMBOL_GPL(memory_failure); 1269 1270 #define MEMORY_FAILURE_FIFO_ORDER 4 1271 #define MEMORY_FAILURE_FIFO_SIZE (1 << MEMORY_FAILURE_FIFO_ORDER) 1272 1273 struct memory_failure_entry { 1274 unsigned long pfn; 1275 int trapno; 1276 int flags; 1277 }; 1278 1279 struct memory_failure_cpu { 1280 DECLARE_KFIFO(fifo, struct memory_failure_entry, 1281 MEMORY_FAILURE_FIFO_SIZE); 1282 spinlock_t lock; 1283 struct work_struct work; 1284 }; 1285 1286 static DEFINE_PER_CPU(struct memory_failure_cpu, memory_failure_cpu); 1287 1288 /** 1289 * memory_failure_queue - Schedule handling memory failure of a page. 1290 * @pfn: Page Number of the corrupted page 1291 * @trapno: Trap number reported in the signal to user space. 1292 * @flags: Flags for memory failure handling 1293 * 1294 * This function is called by the low level hardware error handler 1295 * when it detects hardware memory corruption of a page. It schedules 1296 * the recovering of error page, including dropping pages, killing 1297 * processes etc. 1298 * 1299 * The function is primarily of use for corruptions that 1300 * happen outside the current execution context (e.g. when 1301 * detected by a background scrubber) 1302 * 1303 * Can run in IRQ context. 1304 */ 1305 void memory_failure_queue(unsigned long pfn, int trapno, int flags) 1306 { 1307 struct memory_failure_cpu *mf_cpu; 1308 unsigned long proc_flags; 1309 struct memory_failure_entry entry = { 1310 .pfn = pfn, 1311 .trapno = trapno, 1312 .flags = flags, 1313 }; 1314 1315 mf_cpu = &get_cpu_var(memory_failure_cpu); 1316 spin_lock_irqsave(&mf_cpu->lock, proc_flags); 1317 if (kfifo_put(&mf_cpu->fifo, entry)) 1318 schedule_work_on(smp_processor_id(), &mf_cpu->work); 1319 else 1320 pr_err("Memory failure: buffer overflow when queuing memory failure at %#lx\n", 1321 pfn); 1322 spin_unlock_irqrestore(&mf_cpu->lock, proc_flags); 1323 put_cpu_var(memory_failure_cpu); 1324 } 1325 EXPORT_SYMBOL_GPL(memory_failure_queue); 1326 1327 static void memory_failure_work_func(struct work_struct *work) 1328 { 1329 struct memory_failure_cpu *mf_cpu; 1330 struct memory_failure_entry entry = { 0, }; 1331 unsigned long proc_flags; 1332 int gotten; 1333 1334 mf_cpu = this_cpu_ptr(&memory_failure_cpu); 1335 for (;;) { 1336 spin_lock_irqsave(&mf_cpu->lock, proc_flags); 1337 gotten = kfifo_get(&mf_cpu->fifo, &entry); 1338 spin_unlock_irqrestore(&mf_cpu->lock, proc_flags); 1339 if (!gotten) 1340 break; 1341 if (entry.flags & MF_SOFT_OFFLINE) 1342 soft_offline_page(pfn_to_page(entry.pfn), entry.flags); 1343 else 1344 memory_failure(entry.pfn, entry.trapno, entry.flags); 1345 } 1346 } 1347 1348 static int __init memory_failure_init(void) 1349 { 1350 struct memory_failure_cpu *mf_cpu; 1351 int cpu; 1352 1353 for_each_possible_cpu(cpu) { 1354 mf_cpu = &per_cpu(memory_failure_cpu, cpu); 1355 spin_lock_init(&mf_cpu->lock); 1356 INIT_KFIFO(mf_cpu->fifo); 1357 INIT_WORK(&mf_cpu->work, memory_failure_work_func); 1358 } 1359 1360 return 0; 1361 } 1362 core_initcall(memory_failure_init); 1363 1364 #define unpoison_pr_info(fmt, pfn, rs) \ 1365 ({ \ 1366 if (__ratelimit(rs)) \ 1367 pr_info(fmt, pfn); \ 1368 }) 1369 1370 /** 1371 * unpoison_memory - Unpoison a previously poisoned page 1372 * @pfn: Page number of the to be unpoisoned page 1373 * 1374 * Software-unpoison a page that has been poisoned by 1375 * memory_failure() earlier. 1376 * 1377 * This is only done on the software-level, so it only works 1378 * for linux injected failures, not real hardware failures 1379 * 1380 * Returns 0 for success, otherwise -errno. 1381 */ 1382 int unpoison_memory(unsigned long pfn) 1383 { 1384 struct page *page; 1385 struct page *p; 1386 int freeit = 0; 1387 unsigned int nr_pages; 1388 static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL, 1389 DEFAULT_RATELIMIT_BURST); 1390 1391 if (!pfn_valid(pfn)) 1392 return -ENXIO; 1393 1394 p = pfn_to_page(pfn); 1395 page = compound_head(p); 1396 1397 if (!PageHWPoison(p)) { 1398 unpoison_pr_info("MCE: Page was already unpoisoned %#lx\n", 1399 pfn, &unpoison_rs); 1400 return 0; 1401 } 1402 1403 if (page_count(page) > 1) { 1404 unpoison_pr_info("MCE: Someone grabs the hwpoison page %#lx\n", 1405 pfn, &unpoison_rs); 1406 return 0; 1407 } 1408 1409 if (page_mapped(page)) { 1410 unpoison_pr_info("MCE: Someone maps the hwpoison page %#lx\n", 1411 pfn, &unpoison_rs); 1412 return 0; 1413 } 1414 1415 if (page_mapping(page)) { 1416 unpoison_pr_info("MCE: the hwpoison page has non-NULL mapping %#lx\n", 1417 pfn, &unpoison_rs); 1418 return 0; 1419 } 1420 1421 /* 1422 * unpoison_memory() can encounter thp only when the thp is being 1423 * worked by memory_failure() and the page lock is not held yet. 1424 * In such case, we yield to memory_failure() and make unpoison fail. 1425 */ 1426 if (!PageHuge(page) && PageTransHuge(page)) { 1427 unpoison_pr_info("MCE: Memory failure is now running on %#lx\n", 1428 pfn, &unpoison_rs); 1429 return 0; 1430 } 1431 1432 nr_pages = 1 << compound_order(page); 1433 1434 if (!get_hwpoison_page(p)) { 1435 /* 1436 * Since HWPoisoned hugepage should have non-zero refcount, 1437 * race between memory failure and unpoison seems to happen. 1438 * In such case unpoison fails and memory failure runs 1439 * to the end. 1440 */ 1441 if (PageHuge(page)) { 1442 unpoison_pr_info("MCE: Memory failure is now running on free hugepage %#lx\n", 1443 pfn, &unpoison_rs); 1444 return 0; 1445 } 1446 if (TestClearPageHWPoison(p)) 1447 num_poisoned_pages_dec(); 1448 unpoison_pr_info("MCE: Software-unpoisoned free page %#lx\n", 1449 pfn, &unpoison_rs); 1450 return 0; 1451 } 1452 1453 lock_page(page); 1454 /* 1455 * This test is racy because PG_hwpoison is set outside of page lock. 1456 * That's acceptable because that won't trigger kernel panic. Instead, 1457 * the PG_hwpoison page will be caught and isolated on the entrance to 1458 * the free buddy page pool. 1459 */ 1460 if (TestClearPageHWPoison(page)) { 1461 unpoison_pr_info("MCE: Software-unpoisoned page %#lx\n", 1462 pfn, &unpoison_rs); 1463 num_poisoned_pages_sub(nr_pages); 1464 freeit = 1; 1465 if (PageHuge(page)) 1466 clear_page_hwpoison_huge_page(page); 1467 } 1468 unlock_page(page); 1469 1470 put_hwpoison_page(page); 1471 if (freeit && !(pfn == my_zero_pfn(0) && page_count(p) == 1)) 1472 put_hwpoison_page(page); 1473 1474 return 0; 1475 } 1476 EXPORT_SYMBOL(unpoison_memory); 1477 1478 static struct page *new_page(struct page *p, unsigned long private, int **x) 1479 { 1480 int nid = page_to_nid(p); 1481 if (PageHuge(p)) 1482 return alloc_huge_page_node(page_hstate(compound_head(p)), 1483 nid); 1484 else 1485 return __alloc_pages_node(nid, GFP_HIGHUSER_MOVABLE, 0); 1486 } 1487 1488 /* 1489 * Safely get reference count of an arbitrary page. 1490 * Returns 0 for a free page, -EIO for a zero refcount page 1491 * that is not free, and 1 for any other page type. 1492 * For 1 the page is returned with increased page count, otherwise not. 1493 */ 1494 static int __get_any_page(struct page *p, unsigned long pfn, int flags) 1495 { 1496 int ret; 1497 1498 if (flags & MF_COUNT_INCREASED) 1499 return 1; 1500 1501 /* 1502 * When the target page is a free hugepage, just remove it 1503 * from free hugepage list. 1504 */ 1505 if (!get_hwpoison_page(p)) { 1506 if (PageHuge(p)) { 1507 pr_info("%s: %#lx free huge page\n", __func__, pfn); 1508 ret = 0; 1509 } else if (is_free_buddy_page(p)) { 1510 pr_info("%s: %#lx free buddy page\n", __func__, pfn); 1511 ret = 0; 1512 } else { 1513 pr_info("%s: %#lx: unknown zero refcount page type %lx\n", 1514 __func__, pfn, p->flags); 1515 ret = -EIO; 1516 } 1517 } else { 1518 /* Not a free page */ 1519 ret = 1; 1520 } 1521 return ret; 1522 } 1523 1524 static int get_any_page(struct page *page, unsigned long pfn, int flags) 1525 { 1526 int ret = __get_any_page(page, pfn, flags); 1527 1528 if (ret == 1 && !PageHuge(page) && !PageLRU(page)) { 1529 /* 1530 * Try to free it. 1531 */ 1532 put_hwpoison_page(page); 1533 shake_page(page, 1); 1534 1535 /* 1536 * Did it turn free? 1537 */ 1538 ret = __get_any_page(page, pfn, 0); 1539 if (ret == 1 && !PageLRU(page)) { 1540 /* Drop page reference which is from __get_any_page() */ 1541 put_hwpoison_page(page); 1542 pr_info("soft_offline: %#lx: unknown non LRU page type %lx\n", 1543 pfn, page->flags); 1544 return -EIO; 1545 } 1546 } 1547 return ret; 1548 } 1549 1550 static int soft_offline_huge_page(struct page *page, int flags) 1551 { 1552 int ret; 1553 unsigned long pfn = page_to_pfn(page); 1554 struct page *hpage = compound_head(page); 1555 LIST_HEAD(pagelist); 1556 1557 /* 1558 * This double-check of PageHWPoison is to avoid the race with 1559 * memory_failure(). See also comment in __soft_offline_page(). 1560 */ 1561 lock_page(hpage); 1562 if (PageHWPoison(hpage)) { 1563 unlock_page(hpage); 1564 put_hwpoison_page(hpage); 1565 pr_info("soft offline: %#lx hugepage already poisoned\n", pfn); 1566 return -EBUSY; 1567 } 1568 unlock_page(hpage); 1569 1570 ret = isolate_huge_page(hpage, &pagelist); 1571 /* 1572 * get_any_page() and isolate_huge_page() takes a refcount each, 1573 * so need to drop one here. 1574 */ 1575 put_hwpoison_page(hpage); 1576 if (!ret) { 1577 pr_info("soft offline: %#lx hugepage failed to isolate\n", pfn); 1578 return -EBUSY; 1579 } 1580 1581 ret = migrate_pages(&pagelist, new_page, NULL, MPOL_MF_MOVE_ALL, 1582 MIGRATE_SYNC, MR_MEMORY_FAILURE); 1583 if (ret) { 1584 pr_info("soft offline: %#lx: migration failed %d, type %lx\n", 1585 pfn, ret, page->flags); 1586 /* 1587 * We know that soft_offline_huge_page() tries to migrate 1588 * only one hugepage pointed to by hpage, so we need not 1589 * run through the pagelist here. 1590 */ 1591 putback_active_hugepage(hpage); 1592 if (ret > 0) 1593 ret = -EIO; 1594 } else { 1595 /* overcommit hugetlb page will be freed to buddy */ 1596 if (PageHuge(page)) { 1597 set_page_hwpoison_huge_page(hpage); 1598 dequeue_hwpoisoned_huge_page(hpage); 1599 num_poisoned_pages_add(1 << compound_order(hpage)); 1600 } else { 1601 SetPageHWPoison(page); 1602 num_poisoned_pages_inc(); 1603 } 1604 } 1605 return ret; 1606 } 1607 1608 static int __soft_offline_page(struct page *page, int flags) 1609 { 1610 int ret; 1611 unsigned long pfn = page_to_pfn(page); 1612 1613 /* 1614 * Check PageHWPoison again inside page lock because PageHWPoison 1615 * is set by memory_failure() outside page lock. Note that 1616 * memory_failure() also double-checks PageHWPoison inside page lock, 1617 * so there's no race between soft_offline_page() and memory_failure(). 1618 */ 1619 lock_page(page); 1620 wait_on_page_writeback(page); 1621 if (PageHWPoison(page)) { 1622 unlock_page(page); 1623 put_hwpoison_page(page); 1624 pr_info("soft offline: %#lx page already poisoned\n", pfn); 1625 return -EBUSY; 1626 } 1627 /* 1628 * Try to invalidate first. This should work for 1629 * non dirty unmapped page cache pages. 1630 */ 1631 ret = invalidate_inode_page(page); 1632 unlock_page(page); 1633 /* 1634 * RED-PEN would be better to keep it isolated here, but we 1635 * would need to fix isolation locking first. 1636 */ 1637 if (ret == 1) { 1638 put_hwpoison_page(page); 1639 pr_info("soft_offline: %#lx: invalidated\n", pfn); 1640 SetPageHWPoison(page); 1641 num_poisoned_pages_inc(); 1642 return 0; 1643 } 1644 1645 /* 1646 * Simple invalidation didn't work. 1647 * Try to migrate to a new page instead. migrate.c 1648 * handles a large number of cases for us. 1649 */ 1650 ret = isolate_lru_page(page); 1651 /* 1652 * Drop page reference which is came from get_any_page() 1653 * successful isolate_lru_page() already took another one. 1654 */ 1655 put_hwpoison_page(page); 1656 if (!ret) { 1657 LIST_HEAD(pagelist); 1658 inc_zone_page_state(page, NR_ISOLATED_ANON + 1659 page_is_file_cache(page)); 1660 list_add(&page->lru, &pagelist); 1661 ret = migrate_pages(&pagelist, new_page, NULL, MPOL_MF_MOVE_ALL, 1662 MIGRATE_SYNC, MR_MEMORY_FAILURE); 1663 if (ret) { 1664 if (!list_empty(&pagelist)) { 1665 list_del(&page->lru); 1666 dec_zone_page_state(page, NR_ISOLATED_ANON + 1667 page_is_file_cache(page)); 1668 putback_lru_page(page); 1669 } 1670 1671 pr_info("soft offline: %#lx: migration failed %d, type %lx\n", 1672 pfn, ret, page->flags); 1673 if (ret > 0) 1674 ret = -EIO; 1675 } 1676 } else { 1677 pr_info("soft offline: %#lx: isolation failed: %d, page count %d, type %lx\n", 1678 pfn, ret, page_count(page), page->flags); 1679 } 1680 return ret; 1681 } 1682 1683 static int soft_offline_in_use_page(struct page *page, int flags) 1684 { 1685 int ret; 1686 struct page *hpage = compound_head(page); 1687 1688 if (!PageHuge(page) && PageTransHuge(hpage)) { 1689 lock_page(hpage); 1690 if (!PageAnon(hpage) || unlikely(split_huge_page(hpage))) { 1691 unlock_page(hpage); 1692 if (!PageAnon(hpage)) 1693 pr_info("soft offline: %#lx: non anonymous thp\n", page_to_pfn(page)); 1694 else 1695 pr_info("soft offline: %#lx: thp split failed\n", page_to_pfn(page)); 1696 put_hwpoison_page(hpage); 1697 return -EBUSY; 1698 } 1699 unlock_page(hpage); 1700 get_hwpoison_page(page); 1701 put_hwpoison_page(hpage); 1702 } 1703 1704 if (PageHuge(page)) 1705 ret = soft_offline_huge_page(page, flags); 1706 else 1707 ret = __soft_offline_page(page, flags); 1708 1709 return ret; 1710 } 1711 1712 static void soft_offline_free_page(struct page *page) 1713 { 1714 if (PageHuge(page)) { 1715 struct page *hpage = compound_head(page); 1716 1717 set_page_hwpoison_huge_page(hpage); 1718 if (!dequeue_hwpoisoned_huge_page(hpage)) 1719 num_poisoned_pages_add(1 << compound_order(hpage)); 1720 } else { 1721 if (!TestSetPageHWPoison(page)) 1722 num_poisoned_pages_inc(); 1723 } 1724 } 1725 1726 /** 1727 * soft_offline_page - Soft offline a page. 1728 * @page: page to offline 1729 * @flags: flags. Same as memory_failure(). 1730 * 1731 * Returns 0 on success, otherwise negated errno. 1732 * 1733 * Soft offline a page, by migration or invalidation, 1734 * without killing anything. This is for the case when 1735 * a page is not corrupted yet (so it's still valid to access), 1736 * but has had a number of corrected errors and is better taken 1737 * out. 1738 * 1739 * The actual policy on when to do that is maintained by 1740 * user space. 1741 * 1742 * This should never impact any application or cause data loss, 1743 * however it might take some time. 1744 * 1745 * This is not a 100% solution for all memory, but tries to be 1746 * ``good enough'' for the majority of memory. 1747 */ 1748 int soft_offline_page(struct page *page, int flags) 1749 { 1750 int ret; 1751 unsigned long pfn = page_to_pfn(page); 1752 1753 if (PageHWPoison(page)) { 1754 pr_info("soft offline: %#lx page already poisoned\n", pfn); 1755 if (flags & MF_COUNT_INCREASED) 1756 put_hwpoison_page(page); 1757 return -EBUSY; 1758 } 1759 1760 get_online_mems(); 1761 ret = get_any_page(page, pfn, flags); 1762 put_online_mems(); 1763 1764 if (ret > 0) 1765 ret = soft_offline_in_use_page(page, flags); 1766 else if (ret == 0) 1767 soft_offline_free_page(page); 1768 1769 return ret; 1770 } 1771