blob: 729d4b15b645aa49c6eca2f003ebbd66f371796c [file] [log] [blame]
Andi Kleen6a460792009-09-16 11:50:15 +02001/*
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/rmap.h>
39#include <linux/pagemap.h>
40#include <linux/swap.h>
41#include <linux/backing-dev.h>
42#include "internal.h"
43
44int sysctl_memory_failure_early_kill __read_mostly = 0;
45
46int sysctl_memory_failure_recovery __read_mostly = 1;
47
48atomic_long_t mce_bad_pages __read_mostly = ATOMIC_LONG_INIT(0);
49
50/*
51 * Send all the processes who have the page mapped an ``action optional''
52 * signal.
53 */
54static int kill_proc_ao(struct task_struct *t, unsigned long addr, int trapno,
55 unsigned long pfn)
56{
57 struct siginfo si;
58 int ret;
59
60 printk(KERN_ERR
61 "MCE %#lx: Killing %s:%d early due to hardware memory corruption\n",
62 pfn, t->comm, t->pid);
63 si.si_signo = SIGBUS;
64 si.si_errno = 0;
65 si.si_code = BUS_MCEERR_AO;
66 si.si_addr = (void *)addr;
67#ifdef __ARCH_SI_TRAPNO
68 si.si_trapno = trapno;
69#endif
70 si.si_addr_lsb = PAGE_SHIFT;
71 /*
72 * Don't use force here, it's convenient if the signal
73 * can be temporarily blocked.
74 * This could cause a loop when the user sets SIGBUS
75 * to SIG_IGN, but hopefully noone will do that?
76 */
77 ret = send_sig_info(SIGBUS, &si, t); /* synchronous? */
78 if (ret < 0)
79 printk(KERN_INFO "MCE: Error sending signal to %s:%d: %d\n",
80 t->comm, t->pid, ret);
81 return ret;
82}
83
84/*
85 * Kill all processes that have a poisoned page mapped and then isolate
86 * the page.
87 *
88 * General strategy:
89 * Find all processes having the page mapped and kill them.
90 * But we keep a page reference around so that the page is not
91 * actually freed yet.
92 * Then stash the page away
93 *
94 * There's no convenient way to get back to mapped processes
95 * from the VMAs. So do a brute-force search over all
96 * running processes.
97 *
98 * Remember that machine checks are not common (or rather
99 * if they are common you have other problems), so this shouldn't
100 * be a performance issue.
101 *
102 * Also there are some races possible while we get from the
103 * error detection to actually handle it.
104 */
105
106struct to_kill {
107 struct list_head nd;
108 struct task_struct *tsk;
109 unsigned long addr;
110 unsigned addr_valid:1;
111};
112
113/*
114 * Failure handling: if we can't find or can't kill a process there's
115 * not much we can do. We just print a message and ignore otherwise.
116 */
117
118/*
119 * Schedule a process for later kill.
120 * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
121 * TBD would GFP_NOIO be enough?
122 */
123static void add_to_kill(struct task_struct *tsk, struct page *p,
124 struct vm_area_struct *vma,
125 struct list_head *to_kill,
126 struct to_kill **tkc)
127{
128 struct to_kill *tk;
129
130 if (*tkc) {
131 tk = *tkc;
132 *tkc = NULL;
133 } else {
134 tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
135 if (!tk) {
136 printk(KERN_ERR
137 "MCE: Out of memory while machine check handling\n");
138 return;
139 }
140 }
141 tk->addr = page_address_in_vma(p, vma);
142 tk->addr_valid = 1;
143
144 /*
145 * In theory we don't have to kill when the page was
146 * munmaped. But it could be also a mremap. Since that's
147 * likely very rare kill anyways just out of paranoia, but use
148 * a SIGKILL because the error is not contained anymore.
149 */
150 if (tk->addr == -EFAULT) {
151 pr_debug("MCE: Unable to find user space address %lx in %s\n",
152 page_to_pfn(p), tsk->comm);
153 tk->addr_valid = 0;
154 }
155 get_task_struct(tsk);
156 tk->tsk = tsk;
157 list_add_tail(&tk->nd, to_kill);
158}
159
160/*
161 * Kill the processes that have been collected earlier.
162 *
163 * Only do anything when DOIT is set, otherwise just free the list
164 * (this is used for clean pages which do not need killing)
165 * Also when FAIL is set do a force kill because something went
166 * wrong earlier.
167 */
168static void kill_procs_ao(struct list_head *to_kill, int doit, int trapno,
169 int fail, unsigned long pfn)
170{
171 struct to_kill *tk, *next;
172
173 list_for_each_entry_safe (tk, next, to_kill, nd) {
174 if (doit) {
175 /*
176 * In case something went wrong with munmaping
177 * make sure the process doesn't catch the
178 * signal and then access the memory. Just kill it.
179 * the signal handlers
180 */
181 if (fail || tk->addr_valid == 0) {
182 printk(KERN_ERR
183 "MCE %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n",
184 pfn, tk->tsk->comm, tk->tsk->pid);
185 force_sig(SIGKILL, tk->tsk);
186 }
187
188 /*
189 * In theory the process could have mapped
190 * something else on the address in-between. We could
191 * check for that, but we need to tell the
192 * process anyways.
193 */
194 else if (kill_proc_ao(tk->tsk, tk->addr, trapno,
195 pfn) < 0)
196 printk(KERN_ERR
197 "MCE %#lx: Cannot send advisory machine check signal to %s:%d\n",
198 pfn, tk->tsk->comm, tk->tsk->pid);
199 }
200 put_task_struct(tk->tsk);
201 kfree(tk);
202 }
203}
204
205static int task_early_kill(struct task_struct *tsk)
206{
207 if (!tsk->mm)
208 return 0;
209 if (tsk->flags & PF_MCE_PROCESS)
210 return !!(tsk->flags & PF_MCE_EARLY);
211 return sysctl_memory_failure_early_kill;
212}
213
214/*
215 * Collect processes when the error hit an anonymous page.
216 */
217static void collect_procs_anon(struct page *page, struct list_head *to_kill,
218 struct to_kill **tkc)
219{
220 struct vm_area_struct *vma;
221 struct task_struct *tsk;
222 struct anon_vma *av;
223
224 read_lock(&tasklist_lock);
225 av = page_lock_anon_vma(page);
226 if (av == NULL) /* Not actually mapped anymore */
227 goto out;
228 for_each_process (tsk) {
229 if (!task_early_kill(tsk))
230 continue;
231 list_for_each_entry (vma, &av->head, anon_vma_node) {
232 if (!page_mapped_in_vma(page, vma))
233 continue;
234 if (vma->vm_mm == tsk->mm)
235 add_to_kill(tsk, page, vma, to_kill, tkc);
236 }
237 }
238 page_unlock_anon_vma(av);
239out:
240 read_unlock(&tasklist_lock);
241}
242
243/*
244 * Collect processes when the error hit a file mapped page.
245 */
246static void collect_procs_file(struct page *page, struct list_head *to_kill,
247 struct to_kill **tkc)
248{
249 struct vm_area_struct *vma;
250 struct task_struct *tsk;
251 struct prio_tree_iter iter;
252 struct address_space *mapping = page->mapping;
253
254 /*
255 * A note on the locking order between the two locks.
256 * We don't rely on this particular order.
257 * If you have some other code that needs a different order
258 * feel free to switch them around. Or add a reverse link
259 * from mm_struct to task_struct, then this could be all
260 * done without taking tasklist_lock and looping over all tasks.
261 */
262
263 read_lock(&tasklist_lock);
264 spin_lock(&mapping->i_mmap_lock);
265 for_each_process(tsk) {
266 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
267
268 if (!task_early_kill(tsk))
269 continue;
270
271 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff,
272 pgoff) {
273 /*
274 * Send early kill signal to tasks where a vma covers
275 * the page but the corrupted page is not necessarily
276 * mapped it in its pte.
277 * Assume applications who requested early kill want
278 * to be informed of all such data corruptions.
279 */
280 if (vma->vm_mm == tsk->mm)
281 add_to_kill(tsk, page, vma, to_kill, tkc);
282 }
283 }
284 spin_unlock(&mapping->i_mmap_lock);
285 read_unlock(&tasklist_lock);
286}
287
288/*
289 * Collect the processes who have the corrupted page mapped to kill.
290 * This is done in two steps for locking reasons.
291 * First preallocate one tokill structure outside the spin locks,
292 * so that we can kill at least one process reasonably reliable.
293 */
294static void collect_procs(struct page *page, struct list_head *tokill)
295{
296 struct to_kill *tk;
297
298 if (!page->mapping)
299 return;
300
301 tk = kmalloc(sizeof(struct to_kill), GFP_NOIO);
302 if (!tk)
303 return;
304 if (PageAnon(page))
305 collect_procs_anon(page, tokill, &tk);
306 else
307 collect_procs_file(page, tokill, &tk);
308 kfree(tk);
309}
310
311/*
312 * Error handlers for various types of pages.
313 */
314
315enum outcome {
316 FAILED, /* Error handling failed */
317 DELAYED, /* Will be handled later */
318 IGNORED, /* Error safely ignored */
319 RECOVERED, /* Successfully recovered */
320};
321
322static const char *action_name[] = {
323 [FAILED] = "Failed",
324 [DELAYED] = "Delayed",
325 [IGNORED] = "Ignored",
326 [RECOVERED] = "Recovered",
327};
328
329/*
330 * Error hit kernel page.
331 * Do nothing, try to be lucky and not touch this instead. For a few cases we
332 * could be more sophisticated.
333 */
334static int me_kernel(struct page *p, unsigned long pfn)
335{
336 return DELAYED;
337}
338
339/*
340 * Already poisoned page.
341 */
342static int me_ignore(struct page *p, unsigned long pfn)
343{
344 return IGNORED;
345}
346
347/*
348 * Page in unknown state. Do nothing.
349 */
350static int me_unknown(struct page *p, unsigned long pfn)
351{
352 printk(KERN_ERR "MCE %#lx: Unknown page state\n", pfn);
353 return FAILED;
354}
355
356/*
357 * Free memory
358 */
359static int me_free(struct page *p, unsigned long pfn)
360{
361 return DELAYED;
362}
363
364/*
365 * Clean (or cleaned) page cache page.
366 */
367static int me_pagecache_clean(struct page *p, unsigned long pfn)
368{
369 int err;
370 int ret = FAILED;
371 struct address_space *mapping;
372
373 if (!isolate_lru_page(p))
374 page_cache_release(p);
375
376 /*
377 * For anonymous pages we're done the only reference left
378 * should be the one m_f() holds.
379 */
380 if (PageAnon(p))
381 return RECOVERED;
382
383 /*
384 * Now truncate the page in the page cache. This is really
385 * more like a "temporary hole punch"
386 * Don't do this for block devices when someone else
387 * has a reference, because it could be file system metadata
388 * and that's not safe to truncate.
389 */
390 mapping = page_mapping(p);
391 if (!mapping) {
392 /*
393 * Page has been teared down in the meanwhile
394 */
395 return FAILED;
396 }
397
398 /*
399 * Truncation is a bit tricky. Enable it per file system for now.
400 *
401 * Open: to take i_mutex or not for this? Right now we don't.
402 */
403 if (mapping->a_ops->error_remove_page) {
404 err = mapping->a_ops->error_remove_page(mapping, p);
405 if (err != 0) {
406 printk(KERN_INFO "MCE %#lx: Failed to punch page: %d\n",
407 pfn, err);
408 } else if (page_has_private(p) &&
409 !try_to_release_page(p, GFP_NOIO)) {
410 pr_debug("MCE %#lx: failed to release buffers\n", pfn);
411 } else {
412 ret = RECOVERED;
413 }
414 } else {
415 /*
416 * If the file system doesn't support it just invalidate
417 * This fails on dirty or anything with private pages
418 */
419 if (invalidate_inode_page(p))
420 ret = RECOVERED;
421 else
422 printk(KERN_INFO "MCE %#lx: Failed to invalidate\n",
423 pfn);
424 }
425 return ret;
426}
427
428/*
429 * Dirty cache page page
430 * Issues: when the error hit a hole page the error is not properly
431 * propagated.
432 */
433static int me_pagecache_dirty(struct page *p, unsigned long pfn)
434{
435 struct address_space *mapping = page_mapping(p);
436
437 SetPageError(p);
438 /* TBD: print more information about the file. */
439 if (mapping) {
440 /*
441 * IO error will be reported by write(), fsync(), etc.
442 * who check the mapping.
443 * This way the application knows that something went
444 * wrong with its dirty file data.
445 *
446 * There's one open issue:
447 *
448 * The EIO will be only reported on the next IO
449 * operation and then cleared through the IO map.
450 * Normally Linux has two mechanisms to pass IO error
451 * first through the AS_EIO flag in the address space
452 * and then through the PageError flag in the page.
453 * Since we drop pages on memory failure handling the
454 * only mechanism open to use is through AS_AIO.
455 *
456 * This has the disadvantage that it gets cleared on
457 * the first operation that returns an error, while
458 * the PageError bit is more sticky and only cleared
459 * when the page is reread or dropped. If an
460 * application assumes it will always get error on
461 * fsync, but does other operations on the fd before
462 * and the page is dropped inbetween then the error
463 * will not be properly reported.
464 *
465 * This can already happen even without hwpoisoned
466 * pages: first on metadata IO errors (which only
467 * report through AS_EIO) or when the page is dropped
468 * at the wrong time.
469 *
470 * So right now we assume that the application DTRT on
471 * the first EIO, but we're not worse than other parts
472 * of the kernel.
473 */
474 mapping_set_error(mapping, EIO);
475 }
476
477 return me_pagecache_clean(p, pfn);
478}
479
480/*
481 * Clean and dirty swap cache.
482 *
483 * Dirty swap cache page is tricky to handle. The page could live both in page
484 * cache and swap cache(ie. page is freshly swapped in). So it could be
485 * referenced concurrently by 2 types of PTEs:
486 * normal PTEs and swap PTEs. We try to handle them consistently by calling
487 * try_to_unmap(TTU_IGNORE_HWPOISON) to convert the normal PTEs to swap PTEs,
488 * and then
489 * - clear dirty bit to prevent IO
490 * - remove from LRU
491 * - but keep in the swap cache, so that when we return to it on
492 * a later page fault, we know the application is accessing
493 * corrupted data and shall be killed (we installed simple
494 * interception code in do_swap_page to catch it).
495 *
496 * Clean swap cache pages can be directly isolated. A later page fault will
497 * bring in the known good data from disk.
498 */
499static int me_swapcache_dirty(struct page *p, unsigned long pfn)
500{
501 int ret = FAILED;
502
503 ClearPageDirty(p);
504 /* Trigger EIO in shmem: */
505 ClearPageUptodate(p);
506
507 if (!isolate_lru_page(p)) {
508 page_cache_release(p);
509 ret = DELAYED;
510 }
511
512 return ret;
513}
514
515static int me_swapcache_clean(struct page *p, unsigned long pfn)
516{
517 int ret = FAILED;
518
519 if (!isolate_lru_page(p)) {
520 page_cache_release(p);
521 ret = RECOVERED;
522 }
523 delete_from_swap_cache(p);
524 return ret;
525}
526
527/*
528 * Huge pages. Needs work.
529 * Issues:
530 * No rmap support so we cannot find the original mapper. In theory could walk
531 * all MMs and look for the mappings, but that would be non atomic and racy.
532 * Need rmap for hugepages for this. Alternatively we could employ a heuristic,
533 * like just walking the current process and hoping it has it mapped (that
534 * should be usually true for the common "shared database cache" case)
535 * Should handle free huge pages and dequeue them too, but this needs to
536 * handle huge page accounting correctly.
537 */
538static int me_huge_page(struct page *p, unsigned long pfn)
539{
540 return FAILED;
541}
542
543/*
544 * Various page states we can handle.
545 *
546 * A page state is defined by its current page->flags bits.
547 * The table matches them in order and calls the right handler.
548 *
549 * This is quite tricky because we can access page at any time
550 * in its live cycle, so all accesses have to be extremly careful.
551 *
552 * This is not complete. More states could be added.
553 * For any missing state don't attempt recovery.
554 */
555
556#define dirty (1UL << PG_dirty)
557#define sc (1UL << PG_swapcache)
558#define unevict (1UL << PG_unevictable)
559#define mlock (1UL << PG_mlocked)
560#define writeback (1UL << PG_writeback)
561#define lru (1UL << PG_lru)
562#define swapbacked (1UL << PG_swapbacked)
563#define head (1UL << PG_head)
564#define tail (1UL << PG_tail)
565#define compound (1UL << PG_compound)
566#define slab (1UL << PG_slab)
567#define buddy (1UL << PG_buddy)
568#define reserved (1UL << PG_reserved)
569
570static struct page_state {
571 unsigned long mask;
572 unsigned long res;
573 char *msg;
574 int (*action)(struct page *p, unsigned long pfn);
575} error_states[] = {
576 { reserved, reserved, "reserved kernel", me_ignore },
577 { buddy, buddy, "free kernel", me_free },
578
579 /*
580 * Could in theory check if slab page is free or if we can drop
581 * currently unused objects without touching them. But just
582 * treat it as standard kernel for now.
583 */
584 { slab, slab, "kernel slab", me_kernel },
585
586#ifdef CONFIG_PAGEFLAGS_EXTENDED
587 { head, head, "huge", me_huge_page },
588 { tail, tail, "huge", me_huge_page },
589#else
590 { compound, compound, "huge", me_huge_page },
591#endif
592
593 { sc|dirty, sc|dirty, "swapcache", me_swapcache_dirty },
594 { sc|dirty, sc, "swapcache", me_swapcache_clean },
595
596 { unevict|dirty, unevict|dirty, "unevictable LRU", me_pagecache_dirty},
597 { unevict, unevict, "unevictable LRU", me_pagecache_clean},
598
599#ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
600 { mlock|dirty, mlock|dirty, "mlocked LRU", me_pagecache_dirty },
601 { mlock, mlock, "mlocked LRU", me_pagecache_clean },
602#endif
603
604 { lru|dirty, lru|dirty, "LRU", me_pagecache_dirty },
605 { lru|dirty, lru, "clean LRU", me_pagecache_clean },
606 { swapbacked, swapbacked, "anonymous", me_pagecache_clean },
607
608 /*
609 * Catchall entry: must be at end.
610 */
611 { 0, 0, "unknown page state", me_unknown },
612};
613
614#undef lru
615
616static void action_result(unsigned long pfn, char *msg, int result)
617{
618 struct page *page = NULL;
619 if (pfn_valid(pfn))
620 page = pfn_to_page(pfn);
621
622 printk(KERN_ERR "MCE %#lx: %s%s page recovery: %s\n",
623 pfn,
624 page && PageDirty(page) ? "dirty " : "",
625 msg, action_name[result]);
626}
627
628static int page_action(struct page_state *ps, struct page *p,
629 unsigned long pfn, int ref)
630{
631 int result;
632
633 result = ps->action(p, pfn);
634 action_result(pfn, ps->msg, result);
635 if (page_count(p) != 1 + ref)
636 printk(KERN_ERR
637 "MCE %#lx: %s page still referenced by %d users\n",
638 pfn, ps->msg, page_count(p) - 1);
639
640 /* Could do more checks here if page looks ok */
641 /*
642 * Could adjust zone counters here to correct for the missing page.
643 */
644
645 return result == RECOVERED ? 0 : -EBUSY;
646}
647
648#define N_UNMAP_TRIES 5
649
650/*
651 * Do all that is necessary to remove user space mappings. Unmap
652 * the pages and send SIGBUS to the processes if the data was dirty.
653 */
654static void hwpoison_user_mappings(struct page *p, unsigned long pfn,
655 int trapno)
656{
657 enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
658 struct address_space *mapping;
659 LIST_HEAD(tokill);
660 int ret;
661 int i;
662 int kill = 1;
663
664 if (PageReserved(p) || PageCompound(p) || PageSlab(p))
665 return;
666
667 if (!PageLRU(p))
668 lru_add_drain_all();
669
670 /*
671 * This check implies we don't kill processes if their pages
672 * are in the swap cache early. Those are always late kills.
673 */
674 if (!page_mapped(p))
675 return;
676
677 if (PageSwapCache(p)) {
678 printk(KERN_ERR
679 "MCE %#lx: keeping poisoned page in swap cache\n", pfn);
680 ttu |= TTU_IGNORE_HWPOISON;
681 }
682
683 /*
684 * Propagate the dirty bit from PTEs to struct page first, because we
685 * need this to decide if we should kill or just drop the page.
686 */
687 mapping = page_mapping(p);
688 if (!PageDirty(p) && mapping && mapping_cap_writeback_dirty(mapping)) {
689 if (page_mkclean(p)) {
690 SetPageDirty(p);
691 } else {
692 kill = 0;
693 ttu |= TTU_IGNORE_HWPOISON;
694 printk(KERN_INFO
695 "MCE %#lx: corrupted page was clean: dropped without side effects\n",
696 pfn);
697 }
698 }
699
700 /*
701 * First collect all the processes that have the page
702 * mapped in dirty form. This has to be done before try_to_unmap,
703 * because ttu takes the rmap data structures down.
704 *
705 * Error handling: We ignore errors here because
706 * there's nothing that can be done.
707 */
708 if (kill)
709 collect_procs(p, &tokill);
710
711 /*
712 * try_to_unmap can fail temporarily due to races.
713 * Try a few times (RED-PEN better strategy?)
714 */
715 for (i = 0; i < N_UNMAP_TRIES; i++) {
716 ret = try_to_unmap(p, ttu);
717 if (ret == SWAP_SUCCESS)
718 break;
719 pr_debug("MCE %#lx: try_to_unmap retry needed %d\n", pfn, ret);
720 }
721
722 if (ret != SWAP_SUCCESS)
723 printk(KERN_ERR "MCE %#lx: failed to unmap page (mapcount=%d)\n",
724 pfn, page_mapcount(p));
725
726 /*
727 * Now that the dirty bit has been propagated to the
728 * struct page and all unmaps done we can decide if
729 * killing is needed or not. Only kill when the page
730 * was dirty, otherwise the tokill list is merely
731 * freed. When there was a problem unmapping earlier
732 * use a more force-full uncatchable kill to prevent
733 * any accesses to the poisoned memory.
734 */
735 kill_procs_ao(&tokill, !!PageDirty(p), trapno,
736 ret != SWAP_SUCCESS, pfn);
737}
738
739int __memory_failure(unsigned long pfn, int trapno, int ref)
740{
741 struct page_state *ps;
742 struct page *p;
743 int res;
744
745 if (!sysctl_memory_failure_recovery)
746 panic("Memory failure from trap %d on page %lx", trapno, pfn);
747
748 if (!pfn_valid(pfn)) {
749 action_result(pfn, "memory outside kernel control", IGNORED);
750 return -EIO;
751 }
752
753 p = pfn_to_page(pfn);
754 if (TestSetPageHWPoison(p)) {
755 action_result(pfn, "already hardware poisoned", IGNORED);
756 return 0;
757 }
758
759 atomic_long_add(1, &mce_bad_pages);
760
761 /*
762 * We need/can do nothing about count=0 pages.
763 * 1) it's a free page, and therefore in safe hand:
764 * prep_new_page() will be the gate keeper.
765 * 2) it's part of a non-compound high order page.
766 * Implies some kernel user: cannot stop them from
767 * R/W the page; let's pray that the page has been
768 * used and will be freed some time later.
769 * In fact it's dangerous to directly bump up page count from 0,
770 * that may make page_freeze_refs()/page_unfreeze_refs() mismatch.
771 */
772 if (!get_page_unless_zero(compound_head(p))) {
773 action_result(pfn, "free or high order kernel", IGNORED);
774 return PageBuddy(compound_head(p)) ? 0 : -EBUSY;
775 }
776
777 /*
778 * Lock the page and wait for writeback to finish.
779 * It's very difficult to mess with pages currently under IO
780 * and in many cases impossible, so we just avoid it here.
781 */
782 lock_page_nosync(p);
783 wait_on_page_writeback(p);
784
785 /*
786 * Now take care of user space mappings.
787 */
788 hwpoison_user_mappings(p, pfn, trapno);
789
790 /*
791 * Torn down by someone else?
792 */
793 if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) {
794 action_result(pfn, "already truncated LRU", IGNORED);
795 res = 0;
796 goto out;
797 }
798
799 res = -EBUSY;
800 for (ps = error_states;; ps++) {
801 if ((p->flags & ps->mask) == ps->res) {
802 res = page_action(ps, p, pfn, ref);
803 break;
804 }
805 }
806out:
807 unlock_page(p);
808 return res;
809}
810EXPORT_SYMBOL_GPL(__memory_failure);
811
812/**
813 * memory_failure - Handle memory failure of a page.
814 * @pfn: Page Number of the corrupted page
815 * @trapno: Trap number reported in the signal to user space.
816 *
817 * This function is called by the low level machine check code
818 * of an architecture when it detects hardware memory corruption
819 * of a page. It tries its best to recover, which includes
820 * dropping pages, killing processes etc.
821 *
822 * The function is primarily of use for corruptions that
823 * happen outside the current execution context (e.g. when
824 * detected by a background scrubber)
825 *
826 * Must run in process context (e.g. a work queue) with interrupts
827 * enabled and no spinlocks hold.
828 */
829void memory_failure(unsigned long pfn, int trapno)
830{
831 __memory_failure(pfn, trapno, 0);
832}