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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> | |
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 | ||
44 | int sysctl_memory_failure_early_kill __read_mostly = 0; | |
45 | ||
46 | int sysctl_memory_failure_recovery __read_mostly = 1; | |
47 | ||
48 | atomic_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 | */ | |
54 | static 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 | ||
106 | struct 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 | */ | |
123 | static 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 | */ | |
168 | static 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 | ||
205 | static 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 | */ | |
217 | static 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); | |
239 | out: | |
240 | read_unlock(&tasklist_lock); | |
241 | } | |
242 | ||
243 | /* | |
244 | * Collect processes when the error hit a file mapped page. | |
245 | */ | |
246 | static 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 | */ | |
294 | static 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 | ||
315 | enum outcome { | |
316 | FAILED, /* Error handling failed */ | |
317 | DELAYED, /* Will be handled later */ | |
318 | IGNORED, /* Error safely ignored */ | |
319 | RECOVERED, /* Successfully recovered */ | |
320 | }; | |
321 | ||
322 | static 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 | */ | |
334 | static int me_kernel(struct page *p, unsigned long pfn) | |
335 | { | |
336 | return DELAYED; | |
337 | } | |
338 | ||
339 | /* | |
340 | * Already poisoned page. | |
341 | */ | |
342 | static int me_ignore(struct page *p, unsigned long pfn) | |
343 | { | |
344 | return IGNORED; | |
345 | } | |
346 | ||
347 | /* | |
348 | * Page in unknown state. Do nothing. | |
349 | */ | |
350 | static 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 | */ | |
359 | static int me_free(struct page *p, unsigned long pfn) | |
360 | { | |
361 | return DELAYED; | |
362 | } | |
363 | ||
364 | /* | |
365 | * Clean (or cleaned) page cache page. | |
366 | */ | |
367 | static 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 | */ | |
433 | static 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 | */ | |
499 | static 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 | ||
515 | static 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 | */ | |
538 | static 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 | ||
570 | static 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 | ||
616 | static 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 | ||
628 | static 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 | */ | |
654 | static 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 | ||
739 | int __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 | } | |
806 | out: | |
807 | unlock_page(p); | |
808 | return res; | |
809 | } | |
810 | EXPORT_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 | */ | |
829 | void memory_failure(unsigned long pfn, int trapno) | |
830 | { | |
831 | __memory_failure(pfn, trapno, 0); | |
832 | } |