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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>
Hugh Dickins01e00f82009-10-13 15:02:11 +010038#include <linux/ksm.h>
Andi Kleen6a460792009-09-16 11:50:15 +020039#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/*
Andi Kleen588f9ce2009-12-16 12:19:57 +010086 * 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/*
Andi Kleen6a460792009-09-16 11:50:15 +0200108 * 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 /*
André Goddard Rosaaf901ca2009-11-14 13:09:05 -0200199 * In case something went wrong with munmapping
Andi Kleen6a460792009-09-16 11:50:15 +0200200 * 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 * Error hit kernel page.
354 * Do nothing, try to be lucky and not touch this instead. For a few cases we
355 * could be more sophisticated.
356 */
357static int me_kernel(struct page *p, unsigned long pfn)
358{
359 return DELAYED;
360}
361
362/*
363 * Already poisoned page.
364 */
365static int me_ignore(struct page *p, unsigned long pfn)
366{
367 return IGNORED;
368}
369
370/*
371 * Page in unknown state. Do nothing.
372 */
373static int me_unknown(struct page *p, unsigned long pfn)
374{
375 printk(KERN_ERR "MCE %#lx: Unknown page state\n", pfn);
376 return FAILED;
377}
378
379/*
380 * Free memory
381 */
382static int me_free(struct page *p, unsigned long pfn)
383{
384 return DELAYED;
385}
386
387/*
388 * Clean (or cleaned) page cache page.
389 */
390static int me_pagecache_clean(struct page *p, unsigned long pfn)
391{
392 int err;
393 int ret = FAILED;
394 struct address_space *mapping;
395
Andi Kleen6a460792009-09-16 11:50:15 +0200396 /*
397 * For anonymous pages we're done the only reference left
398 * should be the one m_f() holds.
399 */
400 if (PageAnon(p))
401 return RECOVERED;
402
403 /*
404 * Now truncate the page in the page cache. This is really
405 * more like a "temporary hole punch"
406 * Don't do this for block devices when someone else
407 * has a reference, because it could be file system metadata
408 * and that's not safe to truncate.
409 */
410 mapping = page_mapping(p);
411 if (!mapping) {
412 /*
413 * Page has been teared down in the meanwhile
414 */
415 return FAILED;
416 }
417
418 /*
419 * Truncation is a bit tricky. Enable it per file system for now.
420 *
421 * Open: to take i_mutex or not for this? Right now we don't.
422 */
423 if (mapping->a_ops->error_remove_page) {
424 err = mapping->a_ops->error_remove_page(mapping, p);
425 if (err != 0) {
426 printk(KERN_INFO "MCE %#lx: Failed to punch page: %d\n",
427 pfn, err);
428 } else if (page_has_private(p) &&
429 !try_to_release_page(p, GFP_NOIO)) {
430 pr_debug("MCE %#lx: failed to release buffers\n", pfn);
431 } else {
432 ret = RECOVERED;
433 }
434 } else {
435 /*
436 * If the file system doesn't support it just invalidate
437 * This fails on dirty or anything with private pages
438 */
439 if (invalidate_inode_page(p))
440 ret = RECOVERED;
441 else
442 printk(KERN_INFO "MCE %#lx: Failed to invalidate\n",
443 pfn);
444 }
445 return ret;
446}
447
448/*
449 * Dirty cache page page
450 * Issues: when the error hit a hole page the error is not properly
451 * propagated.
452 */
453static int me_pagecache_dirty(struct page *p, unsigned long pfn)
454{
455 struct address_space *mapping = page_mapping(p);
456
457 SetPageError(p);
458 /* TBD: print more information about the file. */
459 if (mapping) {
460 /*
461 * IO error will be reported by write(), fsync(), etc.
462 * who check the mapping.
463 * This way the application knows that something went
464 * wrong with its dirty file data.
465 *
466 * There's one open issue:
467 *
468 * The EIO will be only reported on the next IO
469 * operation and then cleared through the IO map.
470 * Normally Linux has two mechanisms to pass IO error
471 * first through the AS_EIO flag in the address space
472 * and then through the PageError flag in the page.
473 * Since we drop pages on memory failure handling the
474 * only mechanism open to use is through AS_AIO.
475 *
476 * This has the disadvantage that it gets cleared on
477 * the first operation that returns an error, while
478 * the PageError bit is more sticky and only cleared
479 * when the page is reread or dropped. If an
480 * application assumes it will always get error on
481 * fsync, but does other operations on the fd before
482 * and the page is dropped inbetween then the error
483 * will not be properly reported.
484 *
485 * This can already happen even without hwpoisoned
486 * pages: first on metadata IO errors (which only
487 * report through AS_EIO) or when the page is dropped
488 * at the wrong time.
489 *
490 * So right now we assume that the application DTRT on
491 * the first EIO, but we're not worse than other parts
492 * of the kernel.
493 */
494 mapping_set_error(mapping, EIO);
495 }
496
497 return me_pagecache_clean(p, pfn);
498}
499
500/*
501 * Clean and dirty swap cache.
502 *
503 * Dirty swap cache page is tricky to handle. The page could live both in page
504 * cache and swap cache(ie. page is freshly swapped in). So it could be
505 * referenced concurrently by 2 types of PTEs:
506 * normal PTEs and swap PTEs. We try to handle them consistently by calling
507 * try_to_unmap(TTU_IGNORE_HWPOISON) to convert the normal PTEs to swap PTEs,
508 * and then
509 * - clear dirty bit to prevent IO
510 * - remove from LRU
511 * - but keep in the swap cache, so that when we return to it on
512 * a later page fault, we know the application is accessing
513 * corrupted data and shall be killed (we installed simple
514 * interception code in do_swap_page to catch it).
515 *
516 * Clean swap cache pages can be directly isolated. A later page fault will
517 * bring in the known good data from disk.
518 */
519static int me_swapcache_dirty(struct page *p, unsigned long pfn)
520{
Andi Kleen6a460792009-09-16 11:50:15 +0200521 ClearPageDirty(p);
522 /* Trigger EIO in shmem: */
523 ClearPageUptodate(p);
524
Wu Fengguange43c3af2009-09-29 13:16:20 +0800525 return DELAYED;
Andi Kleen6a460792009-09-16 11:50:15 +0200526}
527
528static int me_swapcache_clean(struct page *p, unsigned long pfn)
529{
Andi Kleen6a460792009-09-16 11:50:15 +0200530 delete_from_swap_cache(p);
Wu Fengguange43c3af2009-09-29 13:16:20 +0800531
532 return RECOVERED;
Andi Kleen6a460792009-09-16 11:50:15 +0200533}
534
535/*
536 * Huge pages. Needs work.
537 * Issues:
538 * No rmap support so we cannot find the original mapper. In theory could walk
539 * all MMs and look for the mappings, but that would be non atomic and racy.
540 * Need rmap for hugepages for this. Alternatively we could employ a heuristic,
541 * like just walking the current process and hoping it has it mapped (that
542 * should be usually true for the common "shared database cache" case)
543 * Should handle free huge pages and dequeue them too, but this needs to
544 * handle huge page accounting correctly.
545 */
546static int me_huge_page(struct page *p, unsigned long pfn)
547{
548 return FAILED;
549}
550
551/*
552 * Various page states we can handle.
553 *
554 * A page state is defined by its current page->flags bits.
555 * The table matches them in order and calls the right handler.
556 *
557 * This is quite tricky because we can access page at any time
558 * in its live cycle, so all accesses have to be extremly careful.
559 *
560 * This is not complete. More states could be added.
561 * For any missing state don't attempt recovery.
562 */
563
564#define dirty (1UL << PG_dirty)
565#define sc (1UL << PG_swapcache)
566#define unevict (1UL << PG_unevictable)
567#define mlock (1UL << PG_mlocked)
568#define writeback (1UL << PG_writeback)
569#define lru (1UL << PG_lru)
570#define swapbacked (1UL << PG_swapbacked)
571#define head (1UL << PG_head)
572#define tail (1UL << PG_tail)
573#define compound (1UL << PG_compound)
574#define slab (1UL << PG_slab)
575#define buddy (1UL << PG_buddy)
576#define reserved (1UL << PG_reserved)
577
578static struct page_state {
579 unsigned long mask;
580 unsigned long res;
581 char *msg;
582 int (*action)(struct page *p, unsigned long pfn);
583} error_states[] = {
584 { reserved, reserved, "reserved kernel", me_ignore },
585 { buddy, buddy, "free kernel", me_free },
586
587 /*
588 * Could in theory check if slab page is free or if we can drop
589 * currently unused objects without touching them. But just
590 * treat it as standard kernel for now.
591 */
592 { slab, slab, "kernel slab", me_kernel },
593
594#ifdef CONFIG_PAGEFLAGS_EXTENDED
595 { head, head, "huge", me_huge_page },
596 { tail, tail, "huge", me_huge_page },
597#else
598 { compound, compound, "huge", me_huge_page },
599#endif
600
601 { sc|dirty, sc|dirty, "swapcache", me_swapcache_dirty },
602 { sc|dirty, sc, "swapcache", me_swapcache_clean },
603
604 { unevict|dirty, unevict|dirty, "unevictable LRU", me_pagecache_dirty},
605 { unevict, unevict, "unevictable LRU", me_pagecache_clean},
606
Andi Kleen6a460792009-09-16 11:50:15 +0200607 { mlock|dirty, mlock|dirty, "mlocked LRU", me_pagecache_dirty },
608 { mlock, mlock, "mlocked LRU", me_pagecache_clean },
Andi Kleen6a460792009-09-16 11:50:15 +0200609
610 { lru|dirty, lru|dirty, "LRU", me_pagecache_dirty },
611 { lru|dirty, lru, "clean LRU", me_pagecache_clean },
Andi Kleen6a460792009-09-16 11:50:15 +0200612
613 /*
614 * Catchall entry: must be at end.
615 */
616 { 0, 0, "unknown page state", me_unknown },
617};
618
Andi Kleen6a460792009-09-16 11:50:15 +0200619static void action_result(unsigned long pfn, char *msg, int result)
620{
Wu Fengguanga7560fc2009-12-16 12:19:57 +0100621 struct page *page = pfn_to_page(pfn);
Andi Kleen6a460792009-09-16 11:50:15 +0200622
623 printk(KERN_ERR "MCE %#lx: %s%s page recovery: %s\n",
624 pfn,
Wu Fengguanga7560fc2009-12-16 12:19:57 +0100625 PageDirty(page) ? "dirty " : "",
Andi Kleen6a460792009-09-16 11:50:15 +0200626 msg, action_name[result]);
627}
628
629static int page_action(struct page_state *ps, struct page *p,
Wu Fengguangbd1ce5f2009-12-16 12:19:57 +0100630 unsigned long pfn)
Andi Kleen6a460792009-09-16 11:50:15 +0200631{
632 int result;
Wu Fengguang7456b042009-10-19 08:15:01 +0200633 int count;
Andi Kleen6a460792009-09-16 11:50:15 +0200634
635 result = ps->action(p, pfn);
636 action_result(pfn, ps->msg, result);
Wu Fengguang7456b042009-10-19 08:15:01 +0200637
Wu Fengguangbd1ce5f2009-12-16 12:19:57 +0100638 count = page_count(p) - 1;
Wu Fengguang7456b042009-10-19 08:15:01 +0200639 if (count != 0)
Andi Kleen6a460792009-09-16 11:50:15 +0200640 printk(KERN_ERR
641 "MCE %#lx: %s page still referenced by %d users\n",
Wu Fengguang7456b042009-10-19 08:15:01 +0200642 pfn, ps->msg, count);
Andi Kleen6a460792009-09-16 11:50:15 +0200643
644 /* Could do more checks here if page looks ok */
645 /*
646 * Could adjust zone counters here to correct for the missing page.
647 */
648
649 return result == RECOVERED ? 0 : -EBUSY;
650}
651
652#define N_UNMAP_TRIES 5
653
654/*
655 * Do all that is necessary to remove user space mappings. Unmap
656 * the pages and send SIGBUS to the processes if the data was dirty.
657 */
658static void hwpoison_user_mappings(struct page *p, unsigned long pfn,
659 int trapno)
660{
661 enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
662 struct address_space *mapping;
663 LIST_HEAD(tokill);
664 int ret;
665 int i;
666 int kill = 1;
667
Hugh Dickins01e00f82009-10-13 15:02:11 +0100668 if (PageReserved(p) || PageCompound(p) || PageSlab(p) || PageKsm(p))
Andi Kleen6a460792009-09-16 11:50:15 +0200669 return;
670
Andi Kleen6a460792009-09-16 11:50:15 +0200671 /*
672 * This check implies we don't kill processes if their pages
673 * are in the swap cache early. Those are always late kills.
674 */
675 if (!page_mapped(p))
676 return;
677
678 if (PageSwapCache(p)) {
679 printk(KERN_ERR
680 "MCE %#lx: keeping poisoned page in swap cache\n", pfn);
681 ttu |= TTU_IGNORE_HWPOISON;
682 }
683
684 /*
685 * Propagate the dirty bit from PTEs to struct page first, because we
686 * need this to decide if we should kill or just drop the page.
687 */
688 mapping = page_mapping(p);
689 if (!PageDirty(p) && mapping && mapping_cap_writeback_dirty(mapping)) {
690 if (page_mkclean(p)) {
691 SetPageDirty(p);
692 } else {
693 kill = 0;
694 ttu |= TTU_IGNORE_HWPOISON;
695 printk(KERN_INFO
696 "MCE %#lx: corrupted page was clean: dropped without side effects\n",
697 pfn);
698 }
699 }
700
701 /*
702 * First collect all the processes that have the page
703 * mapped in dirty form. This has to be done before try_to_unmap,
704 * because ttu takes the rmap data structures down.
705 *
706 * Error handling: We ignore errors here because
707 * there's nothing that can be done.
708 */
709 if (kill)
710 collect_procs(p, &tokill);
711
712 /*
713 * try_to_unmap can fail temporarily due to races.
714 * Try a few times (RED-PEN better strategy?)
715 */
716 for (i = 0; i < N_UNMAP_TRIES; i++) {
717 ret = try_to_unmap(p, ttu);
718 if (ret == SWAP_SUCCESS)
719 break;
720 pr_debug("MCE %#lx: try_to_unmap retry needed %d\n", pfn, ret);
721 }
722
723 if (ret != SWAP_SUCCESS)
724 printk(KERN_ERR "MCE %#lx: failed to unmap page (mapcount=%d)\n",
725 pfn, page_mapcount(p));
726
727 /*
728 * Now that the dirty bit has been propagated to the
729 * struct page and all unmaps done we can decide if
730 * killing is needed or not. Only kill when the page
731 * was dirty, otherwise the tokill list is merely
732 * freed. When there was a problem unmapping earlier
733 * use a more force-full uncatchable kill to prevent
734 * any accesses to the poisoned memory.
735 */
736 kill_procs_ao(&tokill, !!PageDirty(p), trapno,
737 ret != SWAP_SUCCESS, pfn);
738}
739
740int __memory_failure(unsigned long pfn, int trapno, int ref)
741{
Wu Fengguange43c3af2009-09-29 13:16:20 +0800742 unsigned long lru_flag;
Andi Kleen6a460792009-09-16 11:50:15 +0200743 struct page_state *ps;
744 struct page *p;
745 int res;
746
747 if (!sysctl_memory_failure_recovery)
748 panic("Memory failure from trap %d on page %lx", trapno, pfn);
749
750 if (!pfn_valid(pfn)) {
Wu Fengguanga7560fc2009-12-16 12:19:57 +0100751 printk(KERN_ERR
752 "MCE %#lx: memory outside kernel control\n",
753 pfn);
754 return -ENXIO;
Andi Kleen6a460792009-09-16 11:50:15 +0200755 }
756
757 p = pfn_to_page(pfn);
758 if (TestSetPageHWPoison(p)) {
759 action_result(pfn, "already hardware poisoned", IGNORED);
760 return 0;
761 }
762
763 atomic_long_add(1, &mce_bad_pages);
764
765 /*
766 * We need/can do nothing about count=0 pages.
767 * 1) it's a free page, and therefore in safe hand:
768 * prep_new_page() will be the gate keeper.
769 * 2) it's part of a non-compound high order page.
770 * Implies some kernel user: cannot stop them from
771 * R/W the page; let's pray that the page has been
772 * used and will be freed some time later.
773 * In fact it's dangerous to directly bump up page count from 0,
774 * that may make page_freeze_refs()/page_unfreeze_refs() mismatch.
775 */
Wu Fengguangbd1ce5f2009-12-16 12:19:57 +0100776 if (!ref && !get_page_unless_zero(compound_head(p))) {
Andi Kleen6a460792009-09-16 11:50:15 +0200777 action_result(pfn, "free or high order kernel", IGNORED);
778 return PageBuddy(compound_head(p)) ? 0 : -EBUSY;
779 }
780
781 /*
Wu Fengguange43c3af2009-09-29 13:16:20 +0800782 * We ignore non-LRU pages for good reasons.
783 * - PG_locked is only well defined for LRU pages and a few others
784 * - to avoid races with __set_page_locked()
785 * - to avoid races with __SetPageSlab*() (and more non-atomic ops)
786 * The check (unnecessarily) ignores LRU pages being isolated and
787 * walked by the page reclaim code, however that's not a big loss.
788 */
789 if (!PageLRU(p))
790 lru_add_drain_all();
791 lru_flag = p->flags & lru;
792 if (isolate_lru_page(p)) {
793 action_result(pfn, "non LRU", IGNORED);
794 put_page(p);
795 return -EBUSY;
796 }
797 page_cache_release(p);
798
799 /*
Andi Kleen6a460792009-09-16 11:50:15 +0200800 * Lock the page and wait for writeback to finish.
801 * It's very difficult to mess with pages currently under IO
802 * and in many cases impossible, so we just avoid it here.
803 */
804 lock_page_nosync(p);
805 wait_on_page_writeback(p);
806
807 /*
808 * Now take care of user space mappings.
809 */
810 hwpoison_user_mappings(p, pfn, trapno);
811
812 /*
813 * Torn down by someone else?
814 */
Wu Fengguange43c3af2009-09-29 13:16:20 +0800815 if ((lru_flag & lru) && !PageSwapCache(p) && p->mapping == NULL) {
Andi Kleen6a460792009-09-16 11:50:15 +0200816 action_result(pfn, "already truncated LRU", IGNORED);
817 res = 0;
818 goto out;
819 }
820
821 res = -EBUSY;
822 for (ps = error_states;; ps++) {
Wu Fengguange43c3af2009-09-29 13:16:20 +0800823 if (((p->flags | lru_flag)& ps->mask) == ps->res) {
Wu Fengguangbd1ce5f2009-12-16 12:19:57 +0100824 res = page_action(ps, p, pfn);
Andi Kleen6a460792009-09-16 11:50:15 +0200825 break;
826 }
827 }
828out:
829 unlock_page(p);
830 return res;
831}
832EXPORT_SYMBOL_GPL(__memory_failure);
833
834/**
835 * memory_failure - Handle memory failure of a page.
836 * @pfn: Page Number of the corrupted page
837 * @trapno: Trap number reported in the signal to user space.
838 *
839 * This function is called by the low level machine check code
840 * of an architecture when it detects hardware memory corruption
841 * of a page. It tries its best to recover, which includes
842 * dropping pages, killing processes etc.
843 *
844 * The function is primarily of use for corruptions that
845 * happen outside the current execution context (e.g. when
846 * detected by a background scrubber)
847 *
848 * Must run in process context (e.g. a work queue) with interrupts
849 * enabled and no spinlocks hold.
850 */
851void memory_failure(unsigned long pfn, int trapno)
852{
853 __memory_failure(pfn, trapno, 0);
854}