memory-failure.c revision 8d22ba1b74aa9420b6032d856446564fb21f8090
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 2bit ECC memory or cache 11 * failure. 12 * 13 * Handles page cache pages in various states. The tricky part 14 * here is that we can access any page asynchronous to other VM 15 * users, because memory failures could happen anytime and anywhere, 16 * possibly violating some of their assumptions. This is why this code 17 * has to be extremely careful. Generally it tries to use normal locking 18 * rules, as in get the standard locks, even if that means the 19 * error handling takes potentially a long time. 20 * 21 * The operation to map back from RMAP chains to processes has to walk 22 * the complete process list and has non linear complexity with the number 23 * mappings. In short it can be quite slow. But since memory corruptions 24 * are rare we hope to get away with this. 25 */ 26 27/* 28 * Notebook: 29 * - hugetlb needs more code 30 * - kcore/oldmem/vmcore/mem/kmem check for hwpoison pages 31 * - pass bad pages to kdump next kernel 32 */ 33#define DEBUG 1 /* remove me in 2.6.34 */ 34#include <linux/kernel.h> 35#include <linux/mm.h> 36#include <linux/page-flags.h> 37#include <linux/sched.h> 38#include <linux/ksm.h> 39#include <linux/rmap.h> 40#include <linux/pagemap.h> 41#include <linux/swap.h> 42#include <linux/backing-dev.h> 43#include "internal.h" 44 45int sysctl_memory_failure_early_kill __read_mostly = 0; 46 47int sysctl_memory_failure_recovery __read_mostly = 1; 48 49atomic_long_t mce_bad_pages __read_mostly = ATOMIC_LONG_INIT(0); 50 51/* 52 * Send all the processes who have the page mapped an ``action optional'' 53 * signal. 54 */ 55static int kill_proc_ao(struct task_struct *t, unsigned long addr, int trapno, 56 unsigned long pfn) 57{ 58 struct siginfo si; 59 int ret; 60 61 printk(KERN_ERR 62 "MCE %#lx: Killing %s:%d early due to hardware memory corruption\n", 63 pfn, t->comm, t->pid); 64 si.si_signo = SIGBUS; 65 si.si_errno = 0; 66 si.si_code = BUS_MCEERR_AO; 67 si.si_addr = (void *)addr; 68#ifdef __ARCH_SI_TRAPNO 69 si.si_trapno = trapno; 70#endif 71 si.si_addr_lsb = PAGE_SHIFT; 72 /* 73 * Don't use force here, it's convenient if the signal 74 * can be temporarily blocked. 75 * This could cause a loop when the user sets SIGBUS 76 * to SIG_IGN, but hopefully noone will do that? 77 */ 78 ret = send_sig_info(SIGBUS, &si, t); /* synchronous? */ 79 if (ret < 0) 80 printk(KERN_INFO "MCE: Error sending signal to %s:%d: %d\n", 81 t->comm, t->pid, ret); 82 return ret; 83} 84 85/* 86 * When a unknown page type is encountered drain as many buffers as possible 87 * in the hope to turn the page into a LRU or free page, which we can handle. 88 */ 89void shake_page(struct page *p) 90{ 91 if (!PageSlab(p)) { 92 lru_add_drain_all(); 93 if (PageLRU(p)) 94 return; 95 drain_all_pages(); 96 if (PageLRU(p) || is_free_buddy_page(p)) 97 return; 98 } 99 /* 100 * Could call shrink_slab here (which would also 101 * shrink other caches). Unfortunately that might 102 * also access the corrupted page, which could be fatal. 103 */ 104} 105EXPORT_SYMBOL_GPL(shake_page); 106 107/* 108 * Kill all processes that have a poisoned page mapped and then isolate 109 * the page. 110 * 111 * General strategy: 112 * Find all processes having the page mapped and kill them. 113 * But we keep a page reference around so that the page is not 114 * actually freed yet. 115 * Then stash the page away 116 * 117 * There's no convenient way to get back to mapped processes 118 * from the VMAs. So do a brute-force search over all 119 * running processes. 120 * 121 * Remember that machine checks are not common (or rather 122 * if they are common you have other problems), so this shouldn't 123 * be a performance issue. 124 * 125 * Also there are some races possible while we get from the 126 * error detection to actually handle it. 127 */ 128 129struct to_kill { 130 struct list_head nd; 131 struct task_struct *tsk; 132 unsigned long addr; 133 unsigned addr_valid:1; 134}; 135 136/* 137 * Failure handling: if we can't find or can't kill a process there's 138 * not much we can do. We just print a message and ignore otherwise. 139 */ 140 141/* 142 * Schedule a process for later kill. 143 * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM. 144 * TBD would GFP_NOIO be enough? 145 */ 146static void add_to_kill(struct task_struct *tsk, struct page *p, 147 struct vm_area_struct *vma, 148 struct list_head *to_kill, 149 struct to_kill **tkc) 150{ 151 struct to_kill *tk; 152 153 if (*tkc) { 154 tk = *tkc; 155 *tkc = NULL; 156 } else { 157 tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC); 158 if (!tk) { 159 printk(KERN_ERR 160 "MCE: Out of memory while machine check handling\n"); 161 return; 162 } 163 } 164 tk->addr = page_address_in_vma(p, vma); 165 tk->addr_valid = 1; 166 167 /* 168 * In theory we don't have to kill when the page was 169 * munmaped. But it could be also a mremap. Since that's 170 * likely very rare kill anyways just out of paranoia, but use 171 * a SIGKILL because the error is not contained anymore. 172 */ 173 if (tk->addr == -EFAULT) { 174 pr_debug("MCE: Unable to find user space address %lx in %s\n", 175 page_to_pfn(p), tsk->comm); 176 tk->addr_valid = 0; 177 } 178 get_task_struct(tsk); 179 tk->tsk = tsk; 180 list_add_tail(&tk->nd, to_kill); 181} 182 183/* 184 * Kill the processes that have been collected earlier. 185 * 186 * Only do anything when DOIT is set, otherwise just free the list 187 * (this is used for clean pages which do not need killing) 188 * Also when FAIL is set do a force kill because something went 189 * wrong earlier. 190 */ 191static void kill_procs_ao(struct list_head *to_kill, int doit, int trapno, 192 int fail, unsigned long pfn) 193{ 194 struct to_kill *tk, *next; 195 196 list_for_each_entry_safe (tk, next, to_kill, nd) { 197 if (doit) { 198 /* 199 * In case something went wrong with munmapping 200 * make sure the process doesn't catch the 201 * signal and then access the memory. Just kill it. 202 * the signal handlers 203 */ 204 if (fail || tk->addr_valid == 0) { 205 printk(KERN_ERR 206 "MCE %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n", 207 pfn, tk->tsk->comm, tk->tsk->pid); 208 force_sig(SIGKILL, tk->tsk); 209 } 210 211 /* 212 * In theory the process could have mapped 213 * something else on the address in-between. We could 214 * check for that, but we need to tell the 215 * process anyways. 216 */ 217 else if (kill_proc_ao(tk->tsk, tk->addr, trapno, 218 pfn) < 0) 219 printk(KERN_ERR 220 "MCE %#lx: Cannot send advisory machine check signal to %s:%d\n", 221 pfn, tk->tsk->comm, tk->tsk->pid); 222 } 223 put_task_struct(tk->tsk); 224 kfree(tk); 225 } 226} 227 228static int task_early_kill(struct task_struct *tsk) 229{ 230 if (!tsk->mm) 231 return 0; 232 if (tsk->flags & PF_MCE_PROCESS) 233 return !!(tsk->flags & PF_MCE_EARLY); 234 return sysctl_memory_failure_early_kill; 235} 236 237/* 238 * Collect processes when the error hit an anonymous page. 239 */ 240static void collect_procs_anon(struct page *page, struct list_head *to_kill, 241 struct to_kill **tkc) 242{ 243 struct vm_area_struct *vma; 244 struct task_struct *tsk; 245 struct anon_vma *av; 246 247 read_lock(&tasklist_lock); 248 av = page_lock_anon_vma(page); 249 if (av == NULL) /* Not actually mapped anymore */ 250 goto out; 251 for_each_process (tsk) { 252 if (!task_early_kill(tsk)) 253 continue; 254 list_for_each_entry (vma, &av->head, anon_vma_node) { 255 if (!page_mapped_in_vma(page, vma)) 256 continue; 257 if (vma->vm_mm == tsk->mm) 258 add_to_kill(tsk, page, vma, to_kill, tkc); 259 } 260 } 261 page_unlock_anon_vma(av); 262out: 263 read_unlock(&tasklist_lock); 264} 265 266/* 267 * Collect processes when the error hit a file mapped page. 268 */ 269static void collect_procs_file(struct page *page, struct list_head *to_kill, 270 struct to_kill **tkc) 271{ 272 struct vm_area_struct *vma; 273 struct task_struct *tsk; 274 struct prio_tree_iter iter; 275 struct address_space *mapping = page->mapping; 276 277 /* 278 * A note on the locking order between the two locks. 279 * We don't rely on this particular order. 280 * If you have some other code that needs a different order 281 * feel free to switch them around. Or add a reverse link 282 * from mm_struct to task_struct, then this could be all 283 * done without taking tasklist_lock and looping over all tasks. 284 */ 285 286 read_lock(&tasklist_lock); 287 spin_lock(&mapping->i_mmap_lock); 288 for_each_process(tsk) { 289 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); 290 291 if (!task_early_kill(tsk)) 292 continue; 293 294 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, 295 pgoff) { 296 /* 297 * Send early kill signal to tasks where a vma covers 298 * the page but the corrupted page is not necessarily 299 * mapped it in its pte. 300 * Assume applications who requested early kill want 301 * to be informed of all such data corruptions. 302 */ 303 if (vma->vm_mm == tsk->mm) 304 add_to_kill(tsk, page, vma, to_kill, tkc); 305 } 306 } 307 spin_unlock(&mapping->i_mmap_lock); 308 read_unlock(&tasklist_lock); 309} 310 311/* 312 * Collect the processes who have the corrupted page mapped to kill. 313 * This is done in two steps for locking reasons. 314 * First preallocate one tokill structure outside the spin locks, 315 * so that we can kill at least one process reasonably reliable. 316 */ 317static void collect_procs(struct page *page, struct list_head *tokill) 318{ 319 struct to_kill *tk; 320 321 if (!page->mapping) 322 return; 323 324 tk = kmalloc(sizeof(struct to_kill), GFP_NOIO); 325 if (!tk) 326 return; 327 if (PageAnon(page)) 328 collect_procs_anon(page, tokill, &tk); 329 else 330 collect_procs_file(page, tokill, &tk); 331 kfree(tk); 332} 333 334/* 335 * Error handlers for various types of pages. 336 */ 337 338enum outcome { 339 FAILED, /* Error handling failed */ 340 DELAYED, /* Will be handled later */ 341 IGNORED, /* Error safely ignored */ 342 RECOVERED, /* Successfully recovered */ 343}; 344 345static const char *action_name[] = { 346 [FAILED] = "Failed", 347 [DELAYED] = "Delayed", 348 [IGNORED] = "Ignored", 349 [RECOVERED] = "Recovered", 350}; 351 352/* 353 * XXX: It is possible that a page is isolated from LRU cache, 354 * and then kept in swap cache or failed to remove from page cache. 355 * The page count will stop it from being freed by unpoison. 356 * Stress tests should be aware of this memory leak problem. 357 */ 358static int delete_from_lru_cache(struct page *p) 359{ 360 if (!isolate_lru_page(p)) { 361 /* 362 * Clear sensible page flags, so that the buddy system won't 363 * complain when the page is unpoison-and-freed. 364 */ 365 ClearPageActive(p); 366 ClearPageUnevictable(p); 367 /* 368 * drop the page count elevated by isolate_lru_page() 369 */ 370 page_cache_release(p); 371 return 0; 372 } 373 return -EIO; 374} 375 376/* 377 * Error hit kernel page. 378 * Do nothing, try to be lucky and not touch this instead. For a few cases we 379 * could be more sophisticated. 380 */ 381static int me_kernel(struct page *p, unsigned long pfn) 382{ 383 return DELAYED; 384} 385 386/* 387 * Already poisoned page. 388 */ 389static int me_ignore(struct page *p, unsigned long pfn) 390{ 391 return IGNORED; 392} 393 394/* 395 * Page in unknown state. Do nothing. 396 */ 397static int me_unknown(struct page *p, unsigned long pfn) 398{ 399 printk(KERN_ERR "MCE %#lx: Unknown page state\n", pfn); 400 return FAILED; 401} 402 403/* 404 * Clean (or cleaned) page cache page. 405 */ 406static int me_pagecache_clean(struct page *p, unsigned long pfn) 407{ 408 int err; 409 int ret = FAILED; 410 struct address_space *mapping; 411 412 delete_from_lru_cache(p); 413 414 /* 415 * For anonymous pages we're done the only reference left 416 * should be the one m_f() holds. 417 */ 418 if (PageAnon(p)) 419 return RECOVERED; 420 421 /* 422 * Now truncate the page in the page cache. This is really 423 * more like a "temporary hole punch" 424 * Don't do this for block devices when someone else 425 * has a reference, because it could be file system metadata 426 * and that's not safe to truncate. 427 */ 428 mapping = page_mapping(p); 429 if (!mapping) { 430 /* 431 * Page has been teared down in the meanwhile 432 */ 433 return FAILED; 434 } 435 436 /* 437 * Truncation is a bit tricky. Enable it per file system for now. 438 * 439 * Open: to take i_mutex or not for this? Right now we don't. 440 */ 441 if (mapping->a_ops->error_remove_page) { 442 err = mapping->a_ops->error_remove_page(mapping, p); 443 if (err != 0) { 444 printk(KERN_INFO "MCE %#lx: Failed to punch page: %d\n", 445 pfn, err); 446 } else if (page_has_private(p) && 447 !try_to_release_page(p, GFP_NOIO)) { 448 pr_debug("MCE %#lx: failed to release buffers\n", pfn); 449 } else { 450 ret = RECOVERED; 451 } 452 } else { 453 /* 454 * If the file system doesn't support it just invalidate 455 * This fails on dirty or anything with private pages 456 */ 457 if (invalidate_inode_page(p)) 458 ret = RECOVERED; 459 else 460 printk(KERN_INFO "MCE %#lx: Failed to invalidate\n", 461 pfn); 462 } 463 return ret; 464} 465 466/* 467 * Dirty cache page page 468 * Issues: when the error hit a hole page the error is not properly 469 * propagated. 470 */ 471static int me_pagecache_dirty(struct page *p, unsigned long pfn) 472{ 473 struct address_space *mapping = page_mapping(p); 474 475 SetPageError(p); 476 /* TBD: print more information about the file. */ 477 if (mapping) { 478 /* 479 * IO error will be reported by write(), fsync(), etc. 480 * who check the mapping. 481 * This way the application knows that something went 482 * wrong with its dirty file data. 483 * 484 * There's one open issue: 485 * 486 * The EIO will be only reported on the next IO 487 * operation and then cleared through the IO map. 488 * Normally Linux has two mechanisms to pass IO error 489 * first through the AS_EIO flag in the address space 490 * and then through the PageError flag in the page. 491 * Since we drop pages on memory failure handling the 492 * only mechanism open to use is through AS_AIO. 493 * 494 * This has the disadvantage that it gets cleared on 495 * the first operation that returns an error, while 496 * the PageError bit is more sticky and only cleared 497 * when the page is reread or dropped. If an 498 * application assumes it will always get error on 499 * fsync, but does other operations on the fd before 500 * and the page is dropped inbetween then the error 501 * will not be properly reported. 502 * 503 * This can already happen even without hwpoisoned 504 * pages: first on metadata IO errors (which only 505 * report through AS_EIO) or when the page is dropped 506 * at the wrong time. 507 * 508 * So right now we assume that the application DTRT on 509 * the first EIO, but we're not worse than other parts 510 * of the kernel. 511 */ 512 mapping_set_error(mapping, EIO); 513 } 514 515 return me_pagecache_clean(p, pfn); 516} 517 518/* 519 * Clean and dirty swap cache. 520 * 521 * Dirty swap cache page is tricky to handle. The page could live both in page 522 * cache and swap cache(ie. page is freshly swapped in). So it could be 523 * referenced concurrently by 2 types of PTEs: 524 * normal PTEs and swap PTEs. We try to handle them consistently by calling 525 * try_to_unmap(TTU_IGNORE_HWPOISON) to convert the normal PTEs to swap PTEs, 526 * and then 527 * - clear dirty bit to prevent IO 528 * - remove from LRU 529 * - but keep in the swap cache, so that when we return to it on 530 * a later page fault, we know the application is accessing 531 * corrupted data and shall be killed (we installed simple 532 * interception code in do_swap_page to catch it). 533 * 534 * Clean swap cache pages can be directly isolated. A later page fault will 535 * bring in the known good data from disk. 536 */ 537static int me_swapcache_dirty(struct page *p, unsigned long pfn) 538{ 539 ClearPageDirty(p); 540 /* Trigger EIO in shmem: */ 541 ClearPageUptodate(p); 542 543 if (!delete_from_lru_cache(p)) 544 return DELAYED; 545 else 546 return FAILED; 547} 548 549static int me_swapcache_clean(struct page *p, unsigned long pfn) 550{ 551 delete_from_swap_cache(p); 552 553 if (!delete_from_lru_cache(p)) 554 return RECOVERED; 555 else 556 return FAILED; 557} 558 559/* 560 * Huge pages. Needs work. 561 * Issues: 562 * No rmap support so we cannot find the original mapper. In theory could walk 563 * all MMs and look for the mappings, but that would be non atomic and racy. 564 * Need rmap for hugepages for this. Alternatively we could employ a heuristic, 565 * like just walking the current process and hoping it has it mapped (that 566 * should be usually true for the common "shared database cache" case) 567 * Should handle free huge pages and dequeue them too, but this needs to 568 * handle huge page accounting correctly. 569 */ 570static int me_huge_page(struct page *p, unsigned long pfn) 571{ 572 return FAILED; 573} 574 575/* 576 * Various page states we can handle. 577 * 578 * A page state is defined by its current page->flags bits. 579 * The table matches them in order and calls the right handler. 580 * 581 * This is quite tricky because we can access page at any time 582 * in its live cycle, so all accesses have to be extremly careful. 583 * 584 * This is not complete. More states could be added. 585 * For any missing state don't attempt recovery. 586 */ 587 588#define dirty (1UL << PG_dirty) 589#define sc (1UL << PG_swapcache) 590#define unevict (1UL << PG_unevictable) 591#define mlock (1UL << PG_mlocked) 592#define writeback (1UL << PG_writeback) 593#define lru (1UL << PG_lru) 594#define swapbacked (1UL << PG_swapbacked) 595#define head (1UL << PG_head) 596#define tail (1UL << PG_tail) 597#define compound (1UL << PG_compound) 598#define slab (1UL << PG_slab) 599#define reserved (1UL << PG_reserved) 600 601static struct page_state { 602 unsigned long mask; 603 unsigned long res; 604 char *msg; 605 int (*action)(struct page *p, unsigned long pfn); 606} error_states[] = { 607 { reserved, reserved, "reserved kernel", me_ignore }, 608 /* 609 * free pages are specially detected outside this table: 610 * PG_buddy pages only make a small fraction of all free pages. 611 */ 612 613 /* 614 * Could in theory check if slab page is free or if we can drop 615 * currently unused objects without touching them. But just 616 * treat it as standard kernel for now. 617 */ 618 { slab, slab, "kernel slab", me_kernel }, 619 620#ifdef CONFIG_PAGEFLAGS_EXTENDED 621 { head, head, "huge", me_huge_page }, 622 { tail, tail, "huge", me_huge_page }, 623#else 624 { compound, compound, "huge", me_huge_page }, 625#endif 626 627 { sc|dirty, sc|dirty, "swapcache", me_swapcache_dirty }, 628 { sc|dirty, sc, "swapcache", me_swapcache_clean }, 629 630 { unevict|dirty, unevict|dirty, "unevictable LRU", me_pagecache_dirty}, 631 { unevict, unevict, "unevictable LRU", me_pagecache_clean}, 632 633 { mlock|dirty, mlock|dirty, "mlocked LRU", me_pagecache_dirty }, 634 { mlock, mlock, "mlocked LRU", me_pagecache_clean }, 635 636 { lru|dirty, lru|dirty, "LRU", me_pagecache_dirty }, 637 { lru|dirty, lru, "clean LRU", me_pagecache_clean }, 638 639 /* 640 * Catchall entry: must be at end. 641 */ 642 { 0, 0, "unknown page state", me_unknown }, 643}; 644 645static void action_result(unsigned long pfn, char *msg, int result) 646{ 647 struct page *page = pfn_to_page(pfn); 648 649 printk(KERN_ERR "MCE %#lx: %s%s page recovery: %s\n", 650 pfn, 651 PageDirty(page) ? "dirty " : "", 652 msg, action_name[result]); 653} 654 655static int page_action(struct page_state *ps, struct page *p, 656 unsigned long pfn) 657{ 658 int result; 659 int count; 660 661 result = ps->action(p, pfn); 662 action_result(pfn, ps->msg, result); 663 664 count = page_count(p) - 1; 665 if (count != 0) 666 printk(KERN_ERR 667 "MCE %#lx: %s page still referenced by %d users\n", 668 pfn, ps->msg, count); 669 670 /* Could do more checks here if page looks ok */ 671 /* 672 * Could adjust zone counters here to correct for the missing page. 673 */ 674 675 return result == RECOVERED ? 0 : -EBUSY; 676} 677 678#define N_UNMAP_TRIES 5 679 680/* 681 * Do all that is necessary to remove user space mappings. Unmap 682 * the pages and send SIGBUS to the processes if the data was dirty. 683 */ 684static int hwpoison_user_mappings(struct page *p, unsigned long pfn, 685 int trapno) 686{ 687 enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS; 688 struct address_space *mapping; 689 LIST_HEAD(tokill); 690 int ret; 691 int i; 692 int kill = 1; 693 694 if (PageReserved(p) || PageSlab(p)) 695 return SWAP_SUCCESS; 696 697 /* 698 * This check implies we don't kill processes if their pages 699 * are in the swap cache early. Those are always late kills. 700 */ 701 if (!page_mapped(p)) 702 return SWAP_SUCCESS; 703 704 if (PageCompound(p) || PageKsm(p)) 705 return SWAP_FAIL; 706 707 if (PageSwapCache(p)) { 708 printk(KERN_ERR 709 "MCE %#lx: keeping poisoned page in swap cache\n", pfn); 710 ttu |= TTU_IGNORE_HWPOISON; 711 } 712 713 /* 714 * Propagate the dirty bit from PTEs to struct page first, because we 715 * need this to decide if we should kill or just drop the page. 716 * XXX: the dirty test could be racy: set_page_dirty() may not always 717 * be called inside page lock (it's recommended but not enforced). 718 */ 719 mapping = page_mapping(p); 720 if (!PageDirty(p) && mapping && mapping_cap_writeback_dirty(mapping)) { 721 if (page_mkclean(p)) { 722 SetPageDirty(p); 723 } else { 724 kill = 0; 725 ttu |= TTU_IGNORE_HWPOISON; 726 printk(KERN_INFO 727 "MCE %#lx: corrupted page was clean: dropped without side effects\n", 728 pfn); 729 } 730 } 731 732 /* 733 * First collect all the processes that have the page 734 * mapped in dirty form. This has to be done before try_to_unmap, 735 * because ttu takes the rmap data structures down. 736 * 737 * Error handling: We ignore errors here because 738 * there's nothing that can be done. 739 */ 740 if (kill) 741 collect_procs(p, &tokill); 742 743 /* 744 * try_to_unmap can fail temporarily due to races. 745 * Try a few times (RED-PEN better strategy?) 746 */ 747 for (i = 0; i < N_UNMAP_TRIES; i++) { 748 ret = try_to_unmap(p, ttu); 749 if (ret == SWAP_SUCCESS) 750 break; 751 pr_debug("MCE %#lx: try_to_unmap retry needed %d\n", pfn, ret); 752 } 753 754 if (ret != SWAP_SUCCESS) 755 printk(KERN_ERR "MCE %#lx: failed to unmap page (mapcount=%d)\n", 756 pfn, page_mapcount(p)); 757 758 /* 759 * Now that the dirty bit has been propagated to the 760 * struct page and all unmaps done we can decide if 761 * killing is needed or not. Only kill when the page 762 * was dirty, otherwise the tokill list is merely 763 * freed. When there was a problem unmapping earlier 764 * use a more force-full uncatchable kill to prevent 765 * any accesses to the poisoned memory. 766 */ 767 kill_procs_ao(&tokill, !!PageDirty(p), trapno, 768 ret != SWAP_SUCCESS, pfn); 769 770 return ret; 771} 772 773int __memory_failure(unsigned long pfn, int trapno, int flags) 774{ 775 struct page_state *ps; 776 struct page *p; 777 int res; 778 779 if (!sysctl_memory_failure_recovery) 780 panic("Memory failure from trap %d on page %lx", trapno, pfn); 781 782 if (!pfn_valid(pfn)) { 783 printk(KERN_ERR 784 "MCE %#lx: memory outside kernel control\n", 785 pfn); 786 return -ENXIO; 787 } 788 789 p = pfn_to_page(pfn); 790 if (TestSetPageHWPoison(p)) { 791 action_result(pfn, "already hardware poisoned", IGNORED); 792 return 0; 793 } 794 795 atomic_long_add(1, &mce_bad_pages); 796 797 /* 798 * We need/can do nothing about count=0 pages. 799 * 1) it's a free page, and therefore in safe hand: 800 * prep_new_page() will be the gate keeper. 801 * 2) it's part of a non-compound high order page. 802 * Implies some kernel user: cannot stop them from 803 * R/W the page; let's pray that the page has been 804 * used and will be freed some time later. 805 * In fact it's dangerous to directly bump up page count from 0, 806 * that may make page_freeze_refs()/page_unfreeze_refs() mismatch. 807 */ 808 if (!(flags & MF_COUNT_INCREASED) && 809 !get_page_unless_zero(compound_head(p))) { 810 if (is_free_buddy_page(p)) { 811 action_result(pfn, "free buddy", DELAYED); 812 return 0; 813 } else { 814 action_result(pfn, "high order kernel", IGNORED); 815 return -EBUSY; 816 } 817 } 818 819 /* 820 * We ignore non-LRU pages for good reasons. 821 * - PG_locked is only well defined for LRU pages and a few others 822 * - to avoid races with __set_page_locked() 823 * - to avoid races with __SetPageSlab*() (and more non-atomic ops) 824 * The check (unnecessarily) ignores LRU pages being isolated and 825 * walked by the page reclaim code, however that's not a big loss. 826 */ 827 if (!PageLRU(p)) 828 lru_add_drain_all(); 829 if (!PageLRU(p)) { 830 action_result(pfn, "non LRU", IGNORED); 831 put_page(p); 832 return -EBUSY; 833 } 834 835 /* 836 * Lock the page and wait for writeback to finish. 837 * It's very difficult to mess with pages currently under IO 838 * and in many cases impossible, so we just avoid it here. 839 */ 840 lock_page_nosync(p); 841 wait_on_page_writeback(p); 842 843 /* 844 * Now take care of user space mappings. 845 * Abort on fail: __remove_from_page_cache() assumes unmapped page. 846 */ 847 if (hwpoison_user_mappings(p, pfn, trapno) != SWAP_SUCCESS) { 848 printk(KERN_ERR "MCE %#lx: cannot unmap page, give up\n", pfn); 849 res = -EBUSY; 850 goto out; 851 } 852 853 /* 854 * Torn down by someone else? 855 */ 856 if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) { 857 action_result(pfn, "already truncated LRU", IGNORED); 858 res = 0; 859 goto out; 860 } 861 862 res = -EBUSY; 863 for (ps = error_states;; ps++) { 864 if ((p->flags & ps->mask) == ps->res) { 865 res = page_action(ps, p, pfn); 866 break; 867 } 868 } 869out: 870 unlock_page(p); 871 return res; 872} 873EXPORT_SYMBOL_GPL(__memory_failure); 874 875/** 876 * memory_failure - Handle memory failure of a page. 877 * @pfn: Page Number of the corrupted page 878 * @trapno: Trap number reported in the signal to user space. 879 * 880 * This function is called by the low level machine check code 881 * of an architecture when it detects hardware memory corruption 882 * of a page. It tries its best to recover, which includes 883 * dropping pages, killing processes etc. 884 * 885 * The function is primarily of use for corruptions that 886 * happen outside the current execution context (e.g. when 887 * detected by a background scrubber) 888 * 889 * Must run in process context (e.g. a work queue) with interrupts 890 * enabled and no spinlocks hold. 891 */ 892void memory_failure(unsigned long pfn, int trapno) 893{ 894 __memory_failure(pfn, trapno, 0); 895} 896