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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>
01e00f88 38#include <linux/ksm.h>
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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 * Kill all processes that have a poisoned page mapped and then isolate
87 * the page.
88 *
89 * General strategy:
90 * Find all processes having the page mapped and kill them.
91 * But we keep a page reference around so that the page is not
92 * actually freed yet.
93 * Then stash the page away
94 *
95 * There's no convenient way to get back to mapped processes
96 * from the VMAs. So do a brute-force search over all
97 * running processes.
98 *
99 * Remember that machine checks are not common (or rather
100 * if they are common you have other problems), so this shouldn't
101 * be a performance issue.
102 *
103 * Also there are some races possible while we get from the
104 * error detection to actually handle it.
105 */
106
107struct to_kill {
108 struct list_head nd;
109 struct task_struct *tsk;
110 unsigned long addr;
111 unsigned addr_valid:1;
112};
113
114/*
115 * Failure handling: if we can't find or can't kill a process there's
116 * not much we can do. We just print a message and ignore otherwise.
117 */
118
119/*
120 * Schedule a process for later kill.
121 * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
122 * TBD would GFP_NOIO be enough?
123 */
124static void add_to_kill(struct task_struct *tsk, struct page *p,
125 struct vm_area_struct *vma,
126 struct list_head *to_kill,
127 struct to_kill **tkc)
128{
129 struct to_kill *tk;
130
131 if (*tkc) {
132 tk = *tkc;
133 *tkc = NULL;
134 } else {
135 tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
136 if (!tk) {
137 printk(KERN_ERR
138 "MCE: Out of memory while machine check handling\n");
139 return;
140 }
141 }
142 tk->addr = page_address_in_vma(p, vma);
143 tk->addr_valid = 1;
144
145 /*
146 * In theory we don't have to kill when the page was
147 * munmaped. But it could be also a mremap. Since that's
148 * likely very rare kill anyways just out of paranoia, but use
149 * a SIGKILL because the error is not contained anymore.
150 */
151 if (tk->addr == -EFAULT) {
152 pr_debug("MCE: Unable to find user space address %lx in %s\n",
153 page_to_pfn(p), tsk->comm);
154 tk->addr_valid = 0;
155 }
156 get_task_struct(tsk);
157 tk->tsk = tsk;
158 list_add_tail(&tk->nd, to_kill);
159}
160
161/*
162 * Kill the processes that have been collected earlier.
163 *
164 * Only do anything when DOIT is set, otherwise just free the list
165 * (this is used for clean pages which do not need killing)
166 * Also when FAIL is set do a force kill because something went
167 * wrong earlier.
168 */
169static void kill_procs_ao(struct list_head *to_kill, int doit, int trapno,
170 int fail, unsigned long pfn)
171{
172 struct to_kill *tk, *next;
173
174 list_for_each_entry_safe (tk, next, to_kill, nd) {
175 if (doit) {
176 /*
af901ca1 177 * In case something went wrong with munmapping
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178 * make sure the process doesn't catch the
179 * signal and then access the memory. Just kill it.
180 * the signal handlers
181 */
182 if (fail || tk->addr_valid == 0) {
183 printk(KERN_ERR
184 "MCE %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n",
185 pfn, tk->tsk->comm, tk->tsk->pid);
186 force_sig(SIGKILL, tk->tsk);
187 }
188
189 /*
190 * In theory the process could have mapped
191 * something else on the address in-between. We could
192 * check for that, but we need to tell the
193 * process anyways.
194 */
195 else if (kill_proc_ao(tk->tsk, tk->addr, trapno,
196 pfn) < 0)
197 printk(KERN_ERR
198 "MCE %#lx: Cannot send advisory machine check signal to %s:%d\n",
199 pfn, tk->tsk->comm, tk->tsk->pid);
200 }
201 put_task_struct(tk->tsk);
202 kfree(tk);
203 }
204}
205
206static int task_early_kill(struct task_struct *tsk)
207{
208 if (!tsk->mm)
209 return 0;
210 if (tsk->flags & PF_MCE_PROCESS)
211 return !!(tsk->flags & PF_MCE_EARLY);
212 return sysctl_memory_failure_early_kill;
213}
214
215/*
216 * Collect processes when the error hit an anonymous page.
217 */
218static void collect_procs_anon(struct page *page, struct list_head *to_kill,
219 struct to_kill **tkc)
220{
221 struct vm_area_struct *vma;
222 struct task_struct *tsk;
223 struct anon_vma *av;
224
225 read_lock(&tasklist_lock);
226 av = page_lock_anon_vma(page);
227 if (av == NULL) /* Not actually mapped anymore */
228 goto out;
229 for_each_process (tsk) {
230 if (!task_early_kill(tsk))
231 continue;
232 list_for_each_entry (vma, &av->head, anon_vma_node) {
233 if (!page_mapped_in_vma(page, vma))
234 continue;
235 if (vma->vm_mm == tsk->mm)
236 add_to_kill(tsk, page, vma, to_kill, tkc);
237 }
238 }
239 page_unlock_anon_vma(av);
240out:
241 read_unlock(&tasklist_lock);
242}
243
244/*
245 * Collect processes when the error hit a file mapped page.
246 */
247static void collect_procs_file(struct page *page, struct list_head *to_kill,
248 struct to_kill **tkc)
249{
250 struct vm_area_struct *vma;
251 struct task_struct *tsk;
252 struct prio_tree_iter iter;
253 struct address_space *mapping = page->mapping;
254
255 /*
256 * A note on the locking order between the two locks.
257 * We don't rely on this particular order.
258 * If you have some other code that needs a different order
259 * feel free to switch them around. Or add a reverse link
260 * from mm_struct to task_struct, then this could be all
261 * done without taking tasklist_lock and looping over all tasks.
262 */
263
264 read_lock(&tasklist_lock);
265 spin_lock(&mapping->i_mmap_lock);
266 for_each_process(tsk) {
267 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
268
269 if (!task_early_kill(tsk))
270 continue;
271
272 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff,
273 pgoff) {
274 /*
275 * Send early kill signal to tasks where a vma covers
276 * the page but the corrupted page is not necessarily
277 * mapped it in its pte.
278 * Assume applications who requested early kill want
279 * to be informed of all such data corruptions.
280 */
281 if (vma->vm_mm == tsk->mm)
282 add_to_kill(tsk, page, vma, to_kill, tkc);
283 }
284 }
285 spin_unlock(&mapping->i_mmap_lock);
286 read_unlock(&tasklist_lock);
287}
288
289/*
290 * Collect the processes who have the corrupted page mapped to kill.
291 * This is done in two steps for locking reasons.
292 * First preallocate one tokill structure outside the spin locks,
293 * so that we can kill at least one process reasonably reliable.
294 */
295static void collect_procs(struct page *page, struct list_head *tokill)
296{
297 struct to_kill *tk;
298
299 if (!page->mapping)
300 return;
301
302 tk = kmalloc(sizeof(struct to_kill), GFP_NOIO);
303 if (!tk)
304 return;
305 if (PageAnon(page))
306 collect_procs_anon(page, tokill, &tk);
307 else
308 collect_procs_file(page, tokill, &tk);
309 kfree(tk);
310}
311
312/*
313 * Error handlers for various types of pages.
314 */
315
316enum outcome {
317 FAILED, /* Error handling failed */
318 DELAYED, /* Will be handled later */
319 IGNORED, /* Error safely ignored */
320 RECOVERED, /* Successfully recovered */
321};
322
323static const char *action_name[] = {
324 [FAILED] = "Failed",
325 [DELAYED] = "Delayed",
326 [IGNORED] = "Ignored",
327 [RECOVERED] = "Recovered",
328};
329
330/*
331 * Error hit kernel page.
332 * Do nothing, try to be lucky and not touch this instead. For a few cases we
333 * could be more sophisticated.
334 */
335static int me_kernel(struct page *p, unsigned long pfn)
336{
337 return DELAYED;
338}
339
340/*
341 * Already poisoned page.
342 */
343static int me_ignore(struct page *p, unsigned long pfn)
344{
345 return IGNORED;
346}
347
348/*
349 * Page in unknown state. Do nothing.
350 */
351static int me_unknown(struct page *p, unsigned long pfn)
352{
353 printk(KERN_ERR "MCE %#lx: Unknown page state\n", pfn);
354 return FAILED;
355}
356
357/*
358 * Free memory
359 */
360static int me_free(struct page *p, unsigned long pfn)
361{
362 return DELAYED;
363}
364
365/*
366 * Clean (or cleaned) page cache page.
367 */
368static int me_pagecache_clean(struct page *p, unsigned long pfn)
369{
370 int err;
371 int ret = FAILED;
372 struct address_space *mapping;
373
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374 /*
375 * For anonymous pages we're done the only reference left
376 * should be the one m_f() holds.
377 */
378 if (PageAnon(p))
379 return RECOVERED;
380
381 /*
382 * Now truncate the page in the page cache. This is really
383 * more like a "temporary hole punch"
384 * Don't do this for block devices when someone else
385 * has a reference, because it could be file system metadata
386 * and that's not safe to truncate.
387 */
388 mapping = page_mapping(p);
389 if (!mapping) {
390 /*
391 * Page has been teared down in the meanwhile
392 */
393 return FAILED;
394 }
395
396 /*
397 * Truncation is a bit tricky. Enable it per file system for now.
398 *
399 * Open: to take i_mutex or not for this? Right now we don't.
400 */
401 if (mapping->a_ops->error_remove_page) {
402 err = mapping->a_ops->error_remove_page(mapping, p);
403 if (err != 0) {
404 printk(KERN_INFO "MCE %#lx: Failed to punch page: %d\n",
405 pfn, err);
406 } else if (page_has_private(p) &&
407 !try_to_release_page(p, GFP_NOIO)) {
408 pr_debug("MCE %#lx: failed to release buffers\n", pfn);
409 } else {
410 ret = RECOVERED;
411 }
412 } else {
413 /*
414 * If the file system doesn't support it just invalidate
415 * This fails on dirty or anything with private pages
416 */
417 if (invalidate_inode_page(p))
418 ret = RECOVERED;
419 else
420 printk(KERN_INFO "MCE %#lx: Failed to invalidate\n",
421 pfn);
422 }
423 return ret;
424}
425
426/*
427 * Dirty cache page page
428 * Issues: when the error hit a hole page the error is not properly
429 * propagated.
430 */
431static int me_pagecache_dirty(struct page *p, unsigned long pfn)
432{
433 struct address_space *mapping = page_mapping(p);
434
435 SetPageError(p);
436 /* TBD: print more information about the file. */
437 if (mapping) {
438 /*
439 * IO error will be reported by write(), fsync(), etc.
440 * who check the mapping.
441 * This way the application knows that something went
442 * wrong with its dirty file data.
443 *
444 * There's one open issue:
445 *
446 * The EIO will be only reported on the next IO
447 * operation and then cleared through the IO map.
448 * Normally Linux has two mechanisms to pass IO error
449 * first through the AS_EIO flag in the address space
450 * and then through the PageError flag in the page.
451 * Since we drop pages on memory failure handling the
452 * only mechanism open to use is through AS_AIO.
453 *
454 * This has the disadvantage that it gets cleared on
455 * the first operation that returns an error, while
456 * the PageError bit is more sticky and only cleared
457 * when the page is reread or dropped. If an
458 * application assumes it will always get error on
459 * fsync, but does other operations on the fd before
460 * and the page is dropped inbetween then the error
461 * will not be properly reported.
462 *
463 * This can already happen even without hwpoisoned
464 * pages: first on metadata IO errors (which only
465 * report through AS_EIO) or when the page is dropped
466 * at the wrong time.
467 *
468 * So right now we assume that the application DTRT on
469 * the first EIO, but we're not worse than other parts
470 * of the kernel.
471 */
472 mapping_set_error(mapping, EIO);
473 }
474
475 return me_pagecache_clean(p, pfn);
476}
477
478/*
479 * Clean and dirty swap cache.
480 *
481 * Dirty swap cache page is tricky to handle. The page could live both in page
482 * cache and swap cache(ie. page is freshly swapped in). So it could be
483 * referenced concurrently by 2 types of PTEs:
484 * normal PTEs and swap PTEs. We try to handle them consistently by calling
485 * try_to_unmap(TTU_IGNORE_HWPOISON) to convert the normal PTEs to swap PTEs,
486 * and then
487 * - clear dirty bit to prevent IO
488 * - remove from LRU
489 * - but keep in the swap cache, so that when we return to it on
490 * a later page fault, we know the application is accessing
491 * corrupted data and shall be killed (we installed simple
492 * interception code in do_swap_page to catch it).
493 *
494 * Clean swap cache pages can be directly isolated. A later page fault will
495 * bring in the known good data from disk.
496 */
497static int me_swapcache_dirty(struct page *p, unsigned long pfn)
498{
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499 ClearPageDirty(p);
500 /* Trigger EIO in shmem: */
501 ClearPageUptodate(p);
502
e43c3afb 503 return DELAYED;
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504}
505
506static int me_swapcache_clean(struct page *p, unsigned long pfn)
507{
6a46079c 508 delete_from_swap_cache(p);
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509
510 return RECOVERED;
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511}
512
513/*
514 * Huge pages. Needs work.
515 * Issues:
516 * No rmap support so we cannot find the original mapper. In theory could walk
517 * all MMs and look for the mappings, but that would be non atomic and racy.
518 * Need rmap for hugepages for this. Alternatively we could employ a heuristic,
519 * like just walking the current process and hoping it has it mapped (that
520 * should be usually true for the common "shared database cache" case)
521 * Should handle free huge pages and dequeue them too, but this needs to
522 * handle huge page accounting correctly.
523 */
524static int me_huge_page(struct page *p, unsigned long pfn)
525{
526 return FAILED;
527}
528
529/*
530 * Various page states we can handle.
531 *
532 * A page state is defined by its current page->flags bits.
533 * The table matches them in order and calls the right handler.
534 *
535 * This is quite tricky because we can access page at any time
536 * in its live cycle, so all accesses have to be extremly careful.
537 *
538 * This is not complete. More states could be added.
539 * For any missing state don't attempt recovery.
540 */
541
542#define dirty (1UL << PG_dirty)
543#define sc (1UL << PG_swapcache)
544#define unevict (1UL << PG_unevictable)
545#define mlock (1UL << PG_mlocked)
546#define writeback (1UL << PG_writeback)
547#define lru (1UL << PG_lru)
548#define swapbacked (1UL << PG_swapbacked)
549#define head (1UL << PG_head)
550#define tail (1UL << PG_tail)
551#define compound (1UL << PG_compound)
552#define slab (1UL << PG_slab)
553#define buddy (1UL << PG_buddy)
554#define reserved (1UL << PG_reserved)
555
556static struct page_state {
557 unsigned long mask;
558 unsigned long res;
559 char *msg;
560 int (*action)(struct page *p, unsigned long pfn);
561} error_states[] = {
562 { reserved, reserved, "reserved kernel", me_ignore },
563 { buddy, buddy, "free kernel", me_free },
564
565 /*
566 * Could in theory check if slab page is free or if we can drop
567 * currently unused objects without touching them. But just
568 * treat it as standard kernel for now.
569 */
570 { slab, slab, "kernel slab", me_kernel },
571
572#ifdef CONFIG_PAGEFLAGS_EXTENDED
573 { head, head, "huge", me_huge_page },
574 { tail, tail, "huge", me_huge_page },
575#else
576 { compound, compound, "huge", me_huge_page },
577#endif
578
579 { sc|dirty, sc|dirty, "swapcache", me_swapcache_dirty },
580 { sc|dirty, sc, "swapcache", me_swapcache_clean },
581
582 { unevict|dirty, unevict|dirty, "unevictable LRU", me_pagecache_dirty},
583 { unevict, unevict, "unevictable LRU", me_pagecache_clean},
584
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585 { mlock|dirty, mlock|dirty, "mlocked LRU", me_pagecache_dirty },
586 { mlock, mlock, "mlocked LRU", me_pagecache_clean },
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587
588 { lru|dirty, lru|dirty, "LRU", me_pagecache_dirty },
589 { lru|dirty, lru, "clean LRU", me_pagecache_clean },
590 { swapbacked, swapbacked, "anonymous", me_pagecache_clean },
591
592 /*
593 * Catchall entry: must be at end.
594 */
595 { 0, 0, "unknown page state", me_unknown },
596};
597
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598static void action_result(unsigned long pfn, char *msg, int result)
599{
600 struct page *page = NULL;
601 if (pfn_valid(pfn))
602 page = pfn_to_page(pfn);
603
604 printk(KERN_ERR "MCE %#lx: %s%s page recovery: %s\n",
605 pfn,
606 page && PageDirty(page) ? "dirty " : "",
607 msg, action_name[result]);
608}
609
610static int page_action(struct page_state *ps, struct page *p,
611 unsigned long pfn, int ref)
612{
613 int result;
7456b040 614 int count;
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615
616 result = ps->action(p, pfn);
617 action_result(pfn, ps->msg, result);
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618
619 count = page_count(p) - 1 - ref;
620 if (count != 0)
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621 printk(KERN_ERR
622 "MCE %#lx: %s page still referenced by %d users\n",
7456b040 623 pfn, ps->msg, count);
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624
625 /* Could do more checks here if page looks ok */
626 /*
627 * Could adjust zone counters here to correct for the missing page.
628 */
629
630 return result == RECOVERED ? 0 : -EBUSY;
631}
632
633#define N_UNMAP_TRIES 5
634
635/*
636 * Do all that is necessary to remove user space mappings. Unmap
637 * the pages and send SIGBUS to the processes if the data was dirty.
638 */
639static void hwpoison_user_mappings(struct page *p, unsigned long pfn,
640 int trapno)
641{
642 enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
643 struct address_space *mapping;
644 LIST_HEAD(tokill);
645 int ret;
646 int i;
647 int kill = 1;
648
01e00f88 649 if (PageReserved(p) || PageCompound(p) || PageSlab(p) || PageKsm(p))
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650 return;
651
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652 /*
653 * This check implies we don't kill processes if their pages
654 * are in the swap cache early. Those are always late kills.
655 */
656 if (!page_mapped(p))
657 return;
658
659 if (PageSwapCache(p)) {
660 printk(KERN_ERR
661 "MCE %#lx: keeping poisoned page in swap cache\n", pfn);
662 ttu |= TTU_IGNORE_HWPOISON;
663 }
664
665 /*
666 * Propagate the dirty bit from PTEs to struct page first, because we
667 * need this to decide if we should kill or just drop the page.
668 */
669 mapping = page_mapping(p);
670 if (!PageDirty(p) && mapping && mapping_cap_writeback_dirty(mapping)) {
671 if (page_mkclean(p)) {
672 SetPageDirty(p);
673 } else {
674 kill = 0;
675 ttu |= TTU_IGNORE_HWPOISON;
676 printk(KERN_INFO
677 "MCE %#lx: corrupted page was clean: dropped without side effects\n",
678 pfn);
679 }
680 }
681
682 /*
683 * First collect all the processes that have the page
684 * mapped in dirty form. This has to be done before try_to_unmap,
685 * because ttu takes the rmap data structures down.
686 *
687 * Error handling: We ignore errors here because
688 * there's nothing that can be done.
689 */
690 if (kill)
691 collect_procs(p, &tokill);
692
693 /*
694 * try_to_unmap can fail temporarily due to races.
695 * Try a few times (RED-PEN better strategy?)
696 */
697 for (i = 0; i < N_UNMAP_TRIES; i++) {
698 ret = try_to_unmap(p, ttu);
699 if (ret == SWAP_SUCCESS)
700 break;
701 pr_debug("MCE %#lx: try_to_unmap retry needed %d\n", pfn, ret);
702 }
703
704 if (ret != SWAP_SUCCESS)
705 printk(KERN_ERR "MCE %#lx: failed to unmap page (mapcount=%d)\n",
706 pfn, page_mapcount(p));
707
708 /*
709 * Now that the dirty bit has been propagated to the
710 * struct page and all unmaps done we can decide if
711 * killing is needed or not. Only kill when the page
712 * was dirty, otherwise the tokill list is merely
713 * freed. When there was a problem unmapping earlier
714 * use a more force-full uncatchable kill to prevent
715 * any accesses to the poisoned memory.
716 */
717 kill_procs_ao(&tokill, !!PageDirty(p), trapno,
718 ret != SWAP_SUCCESS, pfn);
719}
720
721int __memory_failure(unsigned long pfn, int trapno, int ref)
722{
e43c3afb 723 unsigned long lru_flag;
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724 struct page_state *ps;
725 struct page *p;
726 int res;
727
728 if (!sysctl_memory_failure_recovery)
729 panic("Memory failure from trap %d on page %lx", trapno, pfn);
730
731 if (!pfn_valid(pfn)) {
732 action_result(pfn, "memory outside kernel control", IGNORED);
733 return -EIO;
734 }
735
736 p = pfn_to_page(pfn);
737 if (TestSetPageHWPoison(p)) {
738 action_result(pfn, "already hardware poisoned", IGNORED);
739 return 0;
740 }
741
742 atomic_long_add(1, &mce_bad_pages);
743
744 /*
745 * We need/can do nothing about count=0 pages.
746 * 1) it's a free page, and therefore in safe hand:
747 * prep_new_page() will be the gate keeper.
748 * 2) it's part of a non-compound high order page.
749 * Implies some kernel user: cannot stop them from
750 * R/W the page; let's pray that the page has been
751 * used and will be freed some time later.
752 * In fact it's dangerous to directly bump up page count from 0,
753 * that may make page_freeze_refs()/page_unfreeze_refs() mismatch.
754 */
755 if (!get_page_unless_zero(compound_head(p))) {
756 action_result(pfn, "free or high order kernel", IGNORED);
757 return PageBuddy(compound_head(p)) ? 0 : -EBUSY;
758 }
759
e43c3afb
WF
760 /*
761 * We ignore non-LRU pages for good reasons.
762 * - PG_locked is only well defined for LRU pages and a few others
763 * - to avoid races with __set_page_locked()
764 * - to avoid races with __SetPageSlab*() (and more non-atomic ops)
765 * The check (unnecessarily) ignores LRU pages being isolated and
766 * walked by the page reclaim code, however that's not a big loss.
767 */
768 if (!PageLRU(p))
769 lru_add_drain_all();
770 lru_flag = p->flags & lru;
771 if (isolate_lru_page(p)) {
772 action_result(pfn, "non LRU", IGNORED);
773 put_page(p);
774 return -EBUSY;
775 }
776 page_cache_release(p);
777
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778 /*
779 * Lock the page and wait for writeback to finish.
780 * It's very difficult to mess with pages currently under IO
781 * and in many cases impossible, so we just avoid it here.
782 */
783 lock_page_nosync(p);
784 wait_on_page_writeback(p);
785
786 /*
787 * Now take care of user space mappings.
788 */
789 hwpoison_user_mappings(p, pfn, trapno);
790
791 /*
792 * Torn down by someone else?
793 */
e43c3afb 794 if ((lru_flag & lru) && !PageSwapCache(p) && p->mapping == NULL) {
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795 action_result(pfn, "already truncated LRU", IGNORED);
796 res = 0;
797 goto out;
798 }
799
800 res = -EBUSY;
801 for (ps = error_states;; ps++) {
e43c3afb 802 if (((p->flags | lru_flag)& ps->mask) == ps->res) {
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803 res = page_action(ps, p, pfn, ref);
804 break;
805 }
806 }
807out:
808 unlock_page(p);
809 return res;
810}
811EXPORT_SYMBOL_GPL(__memory_failure);
812
813/**
814 * memory_failure - Handle memory failure of a page.
815 * @pfn: Page Number of the corrupted page
816 * @trapno: Trap number reported in the signal to user space.
817 *
818 * This function is called by the low level machine check code
819 * of an architecture when it detects hardware memory corruption
820 * of a page. It tries its best to recover, which includes
821 * dropping pages, killing processes etc.
822 *
823 * The function is primarily of use for corruptions that
824 * happen outside the current execution context (e.g. when
825 * detected by a background scrubber)
826 *
827 * Must run in process context (e.g. a work queue) with interrupts
828 * enabled and no spinlocks hold.
829 */
830void memory_failure(unsigned long pfn, int trapno)
831{
832 __memory_failure(pfn, trapno, 0);
833}