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6a46079c AK |
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> | |
478c5ffc | 37 | #include <linux/kernel-page-flags.h> |
6a46079c | 38 | #include <linux/sched.h> |
01e00f88 | 39 | #include <linux/ksm.h> |
6a46079c AK |
40 | #include <linux/rmap.h> |
41 | #include <linux/pagemap.h> | |
42 | #include <linux/swap.h> | |
43 | #include <linux/backing-dev.h> | |
facb6011 AK |
44 | #include <linux/migrate.h> |
45 | #include <linux/page-isolation.h> | |
46 | #include <linux/suspend.h> | |
6a46079c AK |
47 | #include "internal.h" |
48 | ||
49 | int sysctl_memory_failure_early_kill __read_mostly = 0; | |
50 | ||
51 | int sysctl_memory_failure_recovery __read_mostly = 1; | |
52 | ||
53 | atomic_long_t mce_bad_pages __read_mostly = ATOMIC_LONG_INIT(0); | |
54 | ||
27df5068 AK |
55 | #if defined(CONFIG_HWPOISON_INJECT) || defined(CONFIG_HWPOISON_INJECT_MODULE) |
56 | ||
1bfe5feb | 57 | u32 hwpoison_filter_enable = 0; |
7c116f2b WF |
58 | u32 hwpoison_filter_dev_major = ~0U; |
59 | u32 hwpoison_filter_dev_minor = ~0U; | |
478c5ffc WF |
60 | u64 hwpoison_filter_flags_mask; |
61 | u64 hwpoison_filter_flags_value; | |
1bfe5feb | 62 | EXPORT_SYMBOL_GPL(hwpoison_filter_enable); |
7c116f2b WF |
63 | EXPORT_SYMBOL_GPL(hwpoison_filter_dev_major); |
64 | EXPORT_SYMBOL_GPL(hwpoison_filter_dev_minor); | |
478c5ffc WF |
65 | EXPORT_SYMBOL_GPL(hwpoison_filter_flags_mask); |
66 | EXPORT_SYMBOL_GPL(hwpoison_filter_flags_value); | |
7c116f2b WF |
67 | |
68 | static int hwpoison_filter_dev(struct page *p) | |
69 | { | |
70 | struct address_space *mapping; | |
71 | dev_t dev; | |
72 | ||
73 | if (hwpoison_filter_dev_major == ~0U && | |
74 | hwpoison_filter_dev_minor == ~0U) | |
75 | return 0; | |
76 | ||
77 | /* | |
78 | * page_mapping() does not accept slab page | |
79 | */ | |
80 | if (PageSlab(p)) | |
81 | return -EINVAL; | |
82 | ||
83 | mapping = page_mapping(p); | |
84 | if (mapping == NULL || mapping->host == NULL) | |
85 | return -EINVAL; | |
86 | ||
87 | dev = mapping->host->i_sb->s_dev; | |
88 | if (hwpoison_filter_dev_major != ~0U && | |
89 | hwpoison_filter_dev_major != MAJOR(dev)) | |
90 | return -EINVAL; | |
91 | if (hwpoison_filter_dev_minor != ~0U && | |
92 | hwpoison_filter_dev_minor != MINOR(dev)) | |
93 | return -EINVAL; | |
94 | ||
95 | return 0; | |
96 | } | |
97 | ||
478c5ffc WF |
98 | static int hwpoison_filter_flags(struct page *p) |
99 | { | |
100 | if (!hwpoison_filter_flags_mask) | |
101 | return 0; | |
102 | ||
103 | if ((stable_page_flags(p) & hwpoison_filter_flags_mask) == | |
104 | hwpoison_filter_flags_value) | |
105 | return 0; | |
106 | else | |
107 | return -EINVAL; | |
108 | } | |
109 | ||
4fd466eb AK |
110 | /* |
111 | * This allows stress tests to limit test scope to a collection of tasks | |
112 | * by putting them under some memcg. This prevents killing unrelated/important | |
113 | * processes such as /sbin/init. Note that the target task may share clean | |
114 | * pages with init (eg. libc text), which is harmless. If the target task | |
115 | * share _dirty_ pages with another task B, the test scheme must make sure B | |
116 | * is also included in the memcg. At last, due to race conditions this filter | |
117 | * can only guarantee that the page either belongs to the memcg tasks, or is | |
118 | * a freed page. | |
119 | */ | |
120 | #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP | |
121 | u64 hwpoison_filter_memcg; | |
122 | EXPORT_SYMBOL_GPL(hwpoison_filter_memcg); | |
123 | static int hwpoison_filter_task(struct page *p) | |
124 | { | |
125 | struct mem_cgroup *mem; | |
126 | struct cgroup_subsys_state *css; | |
127 | unsigned long ino; | |
128 | ||
129 | if (!hwpoison_filter_memcg) | |
130 | return 0; | |
131 | ||
132 | mem = try_get_mem_cgroup_from_page(p); | |
133 | if (!mem) | |
134 | return -EINVAL; | |
135 | ||
136 | css = mem_cgroup_css(mem); | |
137 | /* root_mem_cgroup has NULL dentries */ | |
138 | if (!css->cgroup->dentry) | |
139 | return -EINVAL; | |
140 | ||
141 | ino = css->cgroup->dentry->d_inode->i_ino; | |
142 | css_put(css); | |
143 | ||
144 | if (ino != hwpoison_filter_memcg) | |
145 | return -EINVAL; | |
146 | ||
147 | return 0; | |
148 | } | |
149 | #else | |
150 | static int hwpoison_filter_task(struct page *p) { return 0; } | |
151 | #endif | |
152 | ||
7c116f2b WF |
153 | int hwpoison_filter(struct page *p) |
154 | { | |
1bfe5feb HL |
155 | if (!hwpoison_filter_enable) |
156 | return 0; | |
157 | ||
7c116f2b WF |
158 | if (hwpoison_filter_dev(p)) |
159 | return -EINVAL; | |
160 | ||
478c5ffc WF |
161 | if (hwpoison_filter_flags(p)) |
162 | return -EINVAL; | |
163 | ||
4fd466eb AK |
164 | if (hwpoison_filter_task(p)) |
165 | return -EINVAL; | |
166 | ||
7c116f2b WF |
167 | return 0; |
168 | } | |
27df5068 AK |
169 | #else |
170 | int hwpoison_filter(struct page *p) | |
171 | { | |
172 | return 0; | |
173 | } | |
174 | #endif | |
175 | ||
7c116f2b WF |
176 | EXPORT_SYMBOL_GPL(hwpoison_filter); |
177 | ||
6a46079c AK |
178 | /* |
179 | * Send all the processes who have the page mapped an ``action optional'' | |
180 | * signal. | |
181 | */ | |
182 | static int kill_proc_ao(struct task_struct *t, unsigned long addr, int trapno, | |
183 | unsigned long pfn) | |
184 | { | |
185 | struct siginfo si; | |
186 | int ret; | |
187 | ||
188 | printk(KERN_ERR | |
189 | "MCE %#lx: Killing %s:%d early due to hardware memory corruption\n", | |
190 | pfn, t->comm, t->pid); | |
191 | si.si_signo = SIGBUS; | |
192 | si.si_errno = 0; | |
193 | si.si_code = BUS_MCEERR_AO; | |
194 | si.si_addr = (void *)addr; | |
195 | #ifdef __ARCH_SI_TRAPNO | |
196 | si.si_trapno = trapno; | |
197 | #endif | |
198 | si.si_addr_lsb = PAGE_SHIFT; | |
199 | /* | |
200 | * Don't use force here, it's convenient if the signal | |
201 | * can be temporarily blocked. | |
202 | * This could cause a loop when the user sets SIGBUS | |
203 | * to SIG_IGN, but hopefully noone will do that? | |
204 | */ | |
205 | ret = send_sig_info(SIGBUS, &si, t); /* synchronous? */ | |
206 | if (ret < 0) | |
207 | printk(KERN_INFO "MCE: Error sending signal to %s:%d: %d\n", | |
208 | t->comm, t->pid, ret); | |
209 | return ret; | |
210 | } | |
211 | ||
588f9ce6 AK |
212 | /* |
213 | * When a unknown page type is encountered drain as many buffers as possible | |
214 | * in the hope to turn the page into a LRU or free page, which we can handle. | |
215 | */ | |
facb6011 | 216 | void shake_page(struct page *p, int access) |
588f9ce6 AK |
217 | { |
218 | if (!PageSlab(p)) { | |
219 | lru_add_drain_all(); | |
220 | if (PageLRU(p)) | |
221 | return; | |
222 | drain_all_pages(); | |
223 | if (PageLRU(p) || is_free_buddy_page(p)) | |
224 | return; | |
225 | } | |
facb6011 | 226 | |
588f9ce6 | 227 | /* |
facb6011 AK |
228 | * Only all shrink_slab here (which would also |
229 | * shrink other caches) if access is not potentially fatal. | |
588f9ce6 | 230 | */ |
facb6011 AK |
231 | if (access) { |
232 | int nr; | |
233 | do { | |
234 | nr = shrink_slab(1000, GFP_KERNEL, 1000); | |
235 | if (page_count(p) == 0) | |
236 | break; | |
237 | } while (nr > 10); | |
238 | } | |
588f9ce6 AK |
239 | } |
240 | EXPORT_SYMBOL_GPL(shake_page); | |
241 | ||
6a46079c AK |
242 | /* |
243 | * Kill all processes that have a poisoned page mapped and then isolate | |
244 | * the page. | |
245 | * | |
246 | * General strategy: | |
247 | * Find all processes having the page mapped and kill them. | |
248 | * But we keep a page reference around so that the page is not | |
249 | * actually freed yet. | |
250 | * Then stash the page away | |
251 | * | |
252 | * There's no convenient way to get back to mapped processes | |
253 | * from the VMAs. So do a brute-force search over all | |
254 | * running processes. | |
255 | * | |
256 | * Remember that machine checks are not common (or rather | |
257 | * if they are common you have other problems), so this shouldn't | |
258 | * be a performance issue. | |
259 | * | |
260 | * Also there are some races possible while we get from the | |
261 | * error detection to actually handle it. | |
262 | */ | |
263 | ||
264 | struct to_kill { | |
265 | struct list_head nd; | |
266 | struct task_struct *tsk; | |
267 | unsigned long addr; | |
268 | unsigned addr_valid:1; | |
269 | }; | |
270 | ||
271 | /* | |
272 | * Failure handling: if we can't find or can't kill a process there's | |
273 | * not much we can do. We just print a message and ignore otherwise. | |
274 | */ | |
275 | ||
276 | /* | |
277 | * Schedule a process for later kill. | |
278 | * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM. | |
279 | * TBD would GFP_NOIO be enough? | |
280 | */ | |
281 | static void add_to_kill(struct task_struct *tsk, struct page *p, | |
282 | struct vm_area_struct *vma, | |
283 | struct list_head *to_kill, | |
284 | struct to_kill **tkc) | |
285 | { | |
286 | struct to_kill *tk; | |
287 | ||
288 | if (*tkc) { | |
289 | tk = *tkc; | |
290 | *tkc = NULL; | |
291 | } else { | |
292 | tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC); | |
293 | if (!tk) { | |
294 | printk(KERN_ERR | |
295 | "MCE: Out of memory while machine check handling\n"); | |
296 | return; | |
297 | } | |
298 | } | |
299 | tk->addr = page_address_in_vma(p, vma); | |
300 | tk->addr_valid = 1; | |
301 | ||
302 | /* | |
303 | * In theory we don't have to kill when the page was | |
304 | * munmaped. But it could be also a mremap. Since that's | |
305 | * likely very rare kill anyways just out of paranoia, but use | |
306 | * a SIGKILL because the error is not contained anymore. | |
307 | */ | |
308 | if (tk->addr == -EFAULT) { | |
309 | pr_debug("MCE: Unable to find user space address %lx in %s\n", | |
310 | page_to_pfn(p), tsk->comm); | |
311 | tk->addr_valid = 0; | |
312 | } | |
313 | get_task_struct(tsk); | |
314 | tk->tsk = tsk; | |
315 | list_add_tail(&tk->nd, to_kill); | |
316 | } | |
317 | ||
318 | /* | |
319 | * Kill the processes that have been collected earlier. | |
320 | * | |
321 | * Only do anything when DOIT is set, otherwise just free the list | |
322 | * (this is used for clean pages which do not need killing) | |
323 | * Also when FAIL is set do a force kill because something went | |
324 | * wrong earlier. | |
325 | */ | |
326 | static void kill_procs_ao(struct list_head *to_kill, int doit, int trapno, | |
327 | int fail, unsigned long pfn) | |
328 | { | |
329 | struct to_kill *tk, *next; | |
330 | ||
331 | list_for_each_entry_safe (tk, next, to_kill, nd) { | |
332 | if (doit) { | |
333 | /* | |
af901ca1 | 334 | * In case something went wrong with munmapping |
6a46079c AK |
335 | * make sure the process doesn't catch the |
336 | * signal and then access the memory. Just kill it. | |
6a46079c AK |
337 | */ |
338 | if (fail || tk->addr_valid == 0) { | |
339 | printk(KERN_ERR | |
340 | "MCE %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n", | |
341 | pfn, tk->tsk->comm, tk->tsk->pid); | |
342 | force_sig(SIGKILL, tk->tsk); | |
343 | } | |
344 | ||
345 | /* | |
346 | * In theory the process could have mapped | |
347 | * something else on the address in-between. We could | |
348 | * check for that, but we need to tell the | |
349 | * process anyways. | |
350 | */ | |
351 | else if (kill_proc_ao(tk->tsk, tk->addr, trapno, | |
352 | pfn) < 0) | |
353 | printk(KERN_ERR | |
354 | "MCE %#lx: Cannot send advisory machine check signal to %s:%d\n", | |
355 | pfn, tk->tsk->comm, tk->tsk->pid); | |
356 | } | |
357 | put_task_struct(tk->tsk); | |
358 | kfree(tk); | |
359 | } | |
360 | } | |
361 | ||
362 | static int task_early_kill(struct task_struct *tsk) | |
363 | { | |
364 | if (!tsk->mm) | |
365 | return 0; | |
366 | if (tsk->flags & PF_MCE_PROCESS) | |
367 | return !!(tsk->flags & PF_MCE_EARLY); | |
368 | return sysctl_memory_failure_early_kill; | |
369 | } | |
370 | ||
371 | /* | |
372 | * Collect processes when the error hit an anonymous page. | |
373 | */ | |
374 | static void collect_procs_anon(struct page *page, struct list_head *to_kill, | |
375 | struct to_kill **tkc) | |
376 | { | |
377 | struct vm_area_struct *vma; | |
378 | struct task_struct *tsk; | |
379 | struct anon_vma *av; | |
380 | ||
381 | read_lock(&tasklist_lock); | |
382 | av = page_lock_anon_vma(page); | |
383 | if (av == NULL) /* Not actually mapped anymore */ | |
384 | goto out; | |
385 | for_each_process (tsk) { | |
386 | if (!task_early_kill(tsk)) | |
387 | continue; | |
388 | list_for_each_entry (vma, &av->head, anon_vma_node) { | |
389 | if (!page_mapped_in_vma(page, vma)) | |
390 | continue; | |
391 | if (vma->vm_mm == tsk->mm) | |
392 | add_to_kill(tsk, page, vma, to_kill, tkc); | |
393 | } | |
394 | } | |
395 | page_unlock_anon_vma(av); | |
396 | out: | |
397 | read_unlock(&tasklist_lock); | |
398 | } | |
399 | ||
400 | /* | |
401 | * Collect processes when the error hit a file mapped page. | |
402 | */ | |
403 | static void collect_procs_file(struct page *page, struct list_head *to_kill, | |
404 | struct to_kill **tkc) | |
405 | { | |
406 | struct vm_area_struct *vma; | |
407 | struct task_struct *tsk; | |
408 | struct prio_tree_iter iter; | |
409 | struct address_space *mapping = page->mapping; | |
410 | ||
411 | /* | |
412 | * A note on the locking order between the two locks. | |
413 | * We don't rely on this particular order. | |
414 | * If you have some other code that needs a different order | |
415 | * feel free to switch them around. Or add a reverse link | |
416 | * from mm_struct to task_struct, then this could be all | |
417 | * done without taking tasklist_lock and looping over all tasks. | |
418 | */ | |
419 | ||
420 | read_lock(&tasklist_lock); | |
421 | spin_lock(&mapping->i_mmap_lock); | |
422 | for_each_process(tsk) { | |
423 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); | |
424 | ||
425 | if (!task_early_kill(tsk)) | |
426 | continue; | |
427 | ||
428 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, | |
429 | pgoff) { | |
430 | /* | |
431 | * Send early kill signal to tasks where a vma covers | |
432 | * the page but the corrupted page is not necessarily | |
433 | * mapped it in its pte. | |
434 | * Assume applications who requested early kill want | |
435 | * to be informed of all such data corruptions. | |
436 | */ | |
437 | if (vma->vm_mm == tsk->mm) | |
438 | add_to_kill(tsk, page, vma, to_kill, tkc); | |
439 | } | |
440 | } | |
441 | spin_unlock(&mapping->i_mmap_lock); | |
442 | read_unlock(&tasklist_lock); | |
443 | } | |
444 | ||
445 | /* | |
446 | * Collect the processes who have the corrupted page mapped to kill. | |
447 | * This is done in two steps for locking reasons. | |
448 | * First preallocate one tokill structure outside the spin locks, | |
449 | * so that we can kill at least one process reasonably reliable. | |
450 | */ | |
451 | static void collect_procs(struct page *page, struct list_head *tokill) | |
452 | { | |
453 | struct to_kill *tk; | |
454 | ||
455 | if (!page->mapping) | |
456 | return; | |
457 | ||
458 | tk = kmalloc(sizeof(struct to_kill), GFP_NOIO); | |
459 | if (!tk) | |
460 | return; | |
461 | if (PageAnon(page)) | |
462 | collect_procs_anon(page, tokill, &tk); | |
463 | else | |
464 | collect_procs_file(page, tokill, &tk); | |
465 | kfree(tk); | |
466 | } | |
467 | ||
468 | /* | |
469 | * Error handlers for various types of pages. | |
470 | */ | |
471 | ||
472 | enum outcome { | |
d95ea51e WF |
473 | IGNORED, /* Error: cannot be handled */ |
474 | FAILED, /* Error: handling failed */ | |
6a46079c | 475 | DELAYED, /* Will be handled later */ |
6a46079c AK |
476 | RECOVERED, /* Successfully recovered */ |
477 | }; | |
478 | ||
479 | static const char *action_name[] = { | |
d95ea51e | 480 | [IGNORED] = "Ignored", |
6a46079c AK |
481 | [FAILED] = "Failed", |
482 | [DELAYED] = "Delayed", | |
6a46079c AK |
483 | [RECOVERED] = "Recovered", |
484 | }; | |
485 | ||
dc2a1cbf WF |
486 | /* |
487 | * XXX: It is possible that a page is isolated from LRU cache, | |
488 | * and then kept in swap cache or failed to remove from page cache. | |
489 | * The page count will stop it from being freed by unpoison. | |
490 | * Stress tests should be aware of this memory leak problem. | |
491 | */ | |
492 | static int delete_from_lru_cache(struct page *p) | |
493 | { | |
494 | if (!isolate_lru_page(p)) { | |
495 | /* | |
496 | * Clear sensible page flags, so that the buddy system won't | |
497 | * complain when the page is unpoison-and-freed. | |
498 | */ | |
499 | ClearPageActive(p); | |
500 | ClearPageUnevictable(p); | |
501 | /* | |
502 | * drop the page count elevated by isolate_lru_page() | |
503 | */ | |
504 | page_cache_release(p); | |
505 | return 0; | |
506 | } | |
507 | return -EIO; | |
508 | } | |
509 | ||
6a46079c AK |
510 | /* |
511 | * Error hit kernel page. | |
512 | * Do nothing, try to be lucky and not touch this instead. For a few cases we | |
513 | * could be more sophisticated. | |
514 | */ | |
515 | static int me_kernel(struct page *p, unsigned long pfn) | |
6a46079c AK |
516 | { |
517 | return IGNORED; | |
518 | } | |
519 | ||
520 | /* | |
521 | * Page in unknown state. Do nothing. | |
522 | */ | |
523 | static int me_unknown(struct page *p, unsigned long pfn) | |
524 | { | |
525 | printk(KERN_ERR "MCE %#lx: Unknown page state\n", pfn); | |
526 | return FAILED; | |
527 | } | |
528 | ||
6a46079c AK |
529 | /* |
530 | * Clean (or cleaned) page cache page. | |
531 | */ | |
532 | static int me_pagecache_clean(struct page *p, unsigned long pfn) | |
533 | { | |
534 | int err; | |
535 | int ret = FAILED; | |
536 | struct address_space *mapping; | |
537 | ||
dc2a1cbf WF |
538 | delete_from_lru_cache(p); |
539 | ||
6a46079c AK |
540 | /* |
541 | * For anonymous pages we're done the only reference left | |
542 | * should be the one m_f() holds. | |
543 | */ | |
544 | if (PageAnon(p)) | |
545 | return RECOVERED; | |
546 | ||
547 | /* | |
548 | * Now truncate the page in the page cache. This is really | |
549 | * more like a "temporary hole punch" | |
550 | * Don't do this for block devices when someone else | |
551 | * has a reference, because it could be file system metadata | |
552 | * and that's not safe to truncate. | |
553 | */ | |
554 | mapping = page_mapping(p); | |
555 | if (!mapping) { | |
556 | /* | |
557 | * Page has been teared down in the meanwhile | |
558 | */ | |
559 | return FAILED; | |
560 | } | |
561 | ||
562 | /* | |
563 | * Truncation is a bit tricky. Enable it per file system for now. | |
564 | * | |
565 | * Open: to take i_mutex or not for this? Right now we don't. | |
566 | */ | |
567 | if (mapping->a_ops->error_remove_page) { | |
568 | err = mapping->a_ops->error_remove_page(mapping, p); | |
569 | if (err != 0) { | |
570 | printk(KERN_INFO "MCE %#lx: Failed to punch page: %d\n", | |
571 | pfn, err); | |
572 | } else if (page_has_private(p) && | |
573 | !try_to_release_page(p, GFP_NOIO)) { | |
574 | pr_debug("MCE %#lx: failed to release buffers\n", pfn); | |
575 | } else { | |
576 | ret = RECOVERED; | |
577 | } | |
578 | } else { | |
579 | /* | |
580 | * If the file system doesn't support it just invalidate | |
581 | * This fails on dirty or anything with private pages | |
582 | */ | |
583 | if (invalidate_inode_page(p)) | |
584 | ret = RECOVERED; | |
585 | else | |
586 | printk(KERN_INFO "MCE %#lx: Failed to invalidate\n", | |
587 | pfn); | |
588 | } | |
589 | return ret; | |
590 | } | |
591 | ||
592 | /* | |
593 | * Dirty cache page page | |
594 | * Issues: when the error hit a hole page the error is not properly | |
595 | * propagated. | |
596 | */ | |
597 | static int me_pagecache_dirty(struct page *p, unsigned long pfn) | |
598 | { | |
599 | struct address_space *mapping = page_mapping(p); | |
600 | ||
601 | SetPageError(p); | |
602 | /* TBD: print more information about the file. */ | |
603 | if (mapping) { | |
604 | /* | |
605 | * IO error will be reported by write(), fsync(), etc. | |
606 | * who check the mapping. | |
607 | * This way the application knows that something went | |
608 | * wrong with its dirty file data. | |
609 | * | |
610 | * There's one open issue: | |
611 | * | |
612 | * The EIO will be only reported on the next IO | |
613 | * operation and then cleared through the IO map. | |
614 | * Normally Linux has two mechanisms to pass IO error | |
615 | * first through the AS_EIO flag in the address space | |
616 | * and then through the PageError flag in the page. | |
617 | * Since we drop pages on memory failure handling the | |
618 | * only mechanism open to use is through AS_AIO. | |
619 | * | |
620 | * This has the disadvantage that it gets cleared on | |
621 | * the first operation that returns an error, while | |
622 | * the PageError bit is more sticky and only cleared | |
623 | * when the page is reread or dropped. If an | |
624 | * application assumes it will always get error on | |
625 | * fsync, but does other operations on the fd before | |
626 | * and the page is dropped inbetween then the error | |
627 | * will not be properly reported. | |
628 | * | |
629 | * This can already happen even without hwpoisoned | |
630 | * pages: first on metadata IO errors (which only | |
631 | * report through AS_EIO) or when the page is dropped | |
632 | * at the wrong time. | |
633 | * | |
634 | * So right now we assume that the application DTRT on | |
635 | * the first EIO, but we're not worse than other parts | |
636 | * of the kernel. | |
637 | */ | |
638 | mapping_set_error(mapping, EIO); | |
639 | } | |
640 | ||
641 | return me_pagecache_clean(p, pfn); | |
642 | } | |
643 | ||
644 | /* | |
645 | * Clean and dirty swap cache. | |
646 | * | |
647 | * Dirty swap cache page is tricky to handle. The page could live both in page | |
648 | * cache and swap cache(ie. page is freshly swapped in). So it could be | |
649 | * referenced concurrently by 2 types of PTEs: | |
650 | * normal PTEs and swap PTEs. We try to handle them consistently by calling | |
651 | * try_to_unmap(TTU_IGNORE_HWPOISON) to convert the normal PTEs to swap PTEs, | |
652 | * and then | |
653 | * - clear dirty bit to prevent IO | |
654 | * - remove from LRU | |
655 | * - but keep in the swap cache, so that when we return to it on | |
656 | * a later page fault, we know the application is accessing | |
657 | * corrupted data and shall be killed (we installed simple | |
658 | * interception code in do_swap_page to catch it). | |
659 | * | |
660 | * Clean swap cache pages can be directly isolated. A later page fault will | |
661 | * bring in the known good data from disk. | |
662 | */ | |
663 | static int me_swapcache_dirty(struct page *p, unsigned long pfn) | |
664 | { | |
6a46079c AK |
665 | ClearPageDirty(p); |
666 | /* Trigger EIO in shmem: */ | |
667 | ClearPageUptodate(p); | |
668 | ||
dc2a1cbf WF |
669 | if (!delete_from_lru_cache(p)) |
670 | return DELAYED; | |
671 | else | |
672 | return FAILED; | |
6a46079c AK |
673 | } |
674 | ||
675 | static int me_swapcache_clean(struct page *p, unsigned long pfn) | |
676 | { | |
6a46079c | 677 | delete_from_swap_cache(p); |
e43c3afb | 678 | |
dc2a1cbf WF |
679 | if (!delete_from_lru_cache(p)) |
680 | return RECOVERED; | |
681 | else | |
682 | return FAILED; | |
6a46079c AK |
683 | } |
684 | ||
685 | /* | |
686 | * Huge pages. Needs work. | |
687 | * Issues: | |
688 | * No rmap support so we cannot find the original mapper. In theory could walk | |
689 | * all MMs and look for the mappings, but that would be non atomic and racy. | |
690 | * Need rmap for hugepages for this. Alternatively we could employ a heuristic, | |
691 | * like just walking the current process and hoping it has it mapped (that | |
692 | * should be usually true for the common "shared database cache" case) | |
693 | * Should handle free huge pages and dequeue them too, but this needs to | |
694 | * handle huge page accounting correctly. | |
695 | */ | |
696 | static int me_huge_page(struct page *p, unsigned long pfn) | |
697 | { | |
698 | return FAILED; | |
699 | } | |
700 | ||
701 | /* | |
702 | * Various page states we can handle. | |
703 | * | |
704 | * A page state is defined by its current page->flags bits. | |
705 | * The table matches them in order and calls the right handler. | |
706 | * | |
707 | * This is quite tricky because we can access page at any time | |
708 | * in its live cycle, so all accesses have to be extremly careful. | |
709 | * | |
710 | * This is not complete. More states could be added. | |
711 | * For any missing state don't attempt recovery. | |
712 | */ | |
713 | ||
714 | #define dirty (1UL << PG_dirty) | |
715 | #define sc (1UL << PG_swapcache) | |
716 | #define unevict (1UL << PG_unevictable) | |
717 | #define mlock (1UL << PG_mlocked) | |
718 | #define writeback (1UL << PG_writeback) | |
719 | #define lru (1UL << PG_lru) | |
720 | #define swapbacked (1UL << PG_swapbacked) | |
721 | #define head (1UL << PG_head) | |
722 | #define tail (1UL << PG_tail) | |
723 | #define compound (1UL << PG_compound) | |
724 | #define slab (1UL << PG_slab) | |
6a46079c AK |
725 | #define reserved (1UL << PG_reserved) |
726 | ||
727 | static struct page_state { | |
728 | unsigned long mask; | |
729 | unsigned long res; | |
730 | char *msg; | |
731 | int (*action)(struct page *p, unsigned long pfn); | |
732 | } error_states[] = { | |
d95ea51e | 733 | { reserved, reserved, "reserved kernel", me_kernel }, |
95d01fc6 WF |
734 | /* |
735 | * free pages are specially detected outside this table: | |
736 | * PG_buddy pages only make a small fraction of all free pages. | |
737 | */ | |
6a46079c AK |
738 | |
739 | /* | |
740 | * Could in theory check if slab page is free or if we can drop | |
741 | * currently unused objects without touching them. But just | |
742 | * treat it as standard kernel for now. | |
743 | */ | |
744 | { slab, slab, "kernel slab", me_kernel }, | |
745 | ||
746 | #ifdef CONFIG_PAGEFLAGS_EXTENDED | |
747 | { head, head, "huge", me_huge_page }, | |
748 | { tail, tail, "huge", me_huge_page }, | |
749 | #else | |
750 | { compound, compound, "huge", me_huge_page }, | |
751 | #endif | |
752 | ||
753 | { sc|dirty, sc|dirty, "swapcache", me_swapcache_dirty }, | |
754 | { sc|dirty, sc, "swapcache", me_swapcache_clean }, | |
755 | ||
756 | { unevict|dirty, unevict|dirty, "unevictable LRU", me_pagecache_dirty}, | |
757 | { unevict, unevict, "unevictable LRU", me_pagecache_clean}, | |
758 | ||
6a46079c AK |
759 | { mlock|dirty, mlock|dirty, "mlocked LRU", me_pagecache_dirty }, |
760 | { mlock, mlock, "mlocked LRU", me_pagecache_clean }, | |
6a46079c AK |
761 | |
762 | { lru|dirty, lru|dirty, "LRU", me_pagecache_dirty }, | |
763 | { lru|dirty, lru, "clean LRU", me_pagecache_clean }, | |
6a46079c AK |
764 | |
765 | /* | |
766 | * Catchall entry: must be at end. | |
767 | */ | |
768 | { 0, 0, "unknown page state", me_unknown }, | |
769 | }; | |
770 | ||
2326c467 AK |
771 | #undef dirty |
772 | #undef sc | |
773 | #undef unevict | |
774 | #undef mlock | |
775 | #undef writeback | |
776 | #undef lru | |
777 | #undef swapbacked | |
778 | #undef head | |
779 | #undef tail | |
780 | #undef compound | |
781 | #undef slab | |
782 | #undef reserved | |
783 | ||
6a46079c AK |
784 | static void action_result(unsigned long pfn, char *msg, int result) |
785 | { | |
a7560fc8 | 786 | struct page *page = pfn_to_page(pfn); |
6a46079c AK |
787 | |
788 | printk(KERN_ERR "MCE %#lx: %s%s page recovery: %s\n", | |
789 | pfn, | |
a7560fc8 | 790 | PageDirty(page) ? "dirty " : "", |
6a46079c AK |
791 | msg, action_name[result]); |
792 | } | |
793 | ||
794 | static int page_action(struct page_state *ps, struct page *p, | |
bd1ce5f9 | 795 | unsigned long pfn) |
6a46079c AK |
796 | { |
797 | int result; | |
7456b040 | 798 | int count; |
6a46079c AK |
799 | |
800 | result = ps->action(p, pfn); | |
801 | action_result(pfn, ps->msg, result); | |
7456b040 | 802 | |
bd1ce5f9 | 803 | count = page_count(p) - 1; |
138ce286 WF |
804 | if (ps->action == me_swapcache_dirty && result == DELAYED) |
805 | count--; | |
806 | if (count != 0) { | |
6a46079c AK |
807 | printk(KERN_ERR |
808 | "MCE %#lx: %s page still referenced by %d users\n", | |
7456b040 | 809 | pfn, ps->msg, count); |
138ce286 WF |
810 | result = FAILED; |
811 | } | |
6a46079c AK |
812 | |
813 | /* Could do more checks here if page looks ok */ | |
814 | /* | |
815 | * Could adjust zone counters here to correct for the missing page. | |
816 | */ | |
817 | ||
138ce286 | 818 | return (result == RECOVERED || result == DELAYED) ? 0 : -EBUSY; |
6a46079c AK |
819 | } |
820 | ||
821 | #define N_UNMAP_TRIES 5 | |
822 | ||
823 | /* | |
824 | * Do all that is necessary to remove user space mappings. Unmap | |
825 | * the pages and send SIGBUS to the processes if the data was dirty. | |
826 | */ | |
1668bfd5 | 827 | static int hwpoison_user_mappings(struct page *p, unsigned long pfn, |
6a46079c AK |
828 | int trapno) |
829 | { | |
830 | enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS; | |
831 | struct address_space *mapping; | |
832 | LIST_HEAD(tokill); | |
833 | int ret; | |
834 | int i; | |
835 | int kill = 1; | |
836 | ||
1668bfd5 WF |
837 | if (PageReserved(p) || PageSlab(p)) |
838 | return SWAP_SUCCESS; | |
6a46079c | 839 | |
6a46079c AK |
840 | /* |
841 | * This check implies we don't kill processes if their pages | |
842 | * are in the swap cache early. Those are always late kills. | |
843 | */ | |
844 | if (!page_mapped(p)) | |
1668bfd5 WF |
845 | return SWAP_SUCCESS; |
846 | ||
847 | if (PageCompound(p) || PageKsm(p)) | |
848 | return SWAP_FAIL; | |
6a46079c AK |
849 | |
850 | if (PageSwapCache(p)) { | |
851 | printk(KERN_ERR | |
852 | "MCE %#lx: keeping poisoned page in swap cache\n", pfn); | |
853 | ttu |= TTU_IGNORE_HWPOISON; | |
854 | } | |
855 | ||
856 | /* | |
857 | * Propagate the dirty bit from PTEs to struct page first, because we | |
858 | * need this to decide if we should kill or just drop the page. | |
db0480b3 WF |
859 | * XXX: the dirty test could be racy: set_page_dirty() may not always |
860 | * be called inside page lock (it's recommended but not enforced). | |
6a46079c AK |
861 | */ |
862 | mapping = page_mapping(p); | |
863 | if (!PageDirty(p) && mapping && mapping_cap_writeback_dirty(mapping)) { | |
864 | if (page_mkclean(p)) { | |
865 | SetPageDirty(p); | |
866 | } else { | |
867 | kill = 0; | |
868 | ttu |= TTU_IGNORE_HWPOISON; | |
869 | printk(KERN_INFO | |
870 | "MCE %#lx: corrupted page was clean: dropped without side effects\n", | |
871 | pfn); | |
872 | } | |
873 | } | |
874 | ||
875 | /* | |
876 | * First collect all the processes that have the page | |
877 | * mapped in dirty form. This has to be done before try_to_unmap, | |
878 | * because ttu takes the rmap data structures down. | |
879 | * | |
880 | * Error handling: We ignore errors here because | |
881 | * there's nothing that can be done. | |
882 | */ | |
883 | if (kill) | |
884 | collect_procs(p, &tokill); | |
885 | ||
886 | /* | |
887 | * try_to_unmap can fail temporarily due to races. | |
888 | * Try a few times (RED-PEN better strategy?) | |
889 | */ | |
890 | for (i = 0; i < N_UNMAP_TRIES; i++) { | |
891 | ret = try_to_unmap(p, ttu); | |
892 | if (ret == SWAP_SUCCESS) | |
893 | break; | |
894 | pr_debug("MCE %#lx: try_to_unmap retry needed %d\n", pfn, ret); | |
895 | } | |
896 | ||
897 | if (ret != SWAP_SUCCESS) | |
898 | printk(KERN_ERR "MCE %#lx: failed to unmap page (mapcount=%d)\n", | |
899 | pfn, page_mapcount(p)); | |
900 | ||
901 | /* | |
902 | * Now that the dirty bit has been propagated to the | |
903 | * struct page and all unmaps done we can decide if | |
904 | * killing is needed or not. Only kill when the page | |
905 | * was dirty, otherwise the tokill list is merely | |
906 | * freed. When there was a problem unmapping earlier | |
907 | * use a more force-full uncatchable kill to prevent | |
908 | * any accesses to the poisoned memory. | |
909 | */ | |
910 | kill_procs_ao(&tokill, !!PageDirty(p), trapno, | |
911 | ret != SWAP_SUCCESS, pfn); | |
1668bfd5 WF |
912 | |
913 | return ret; | |
6a46079c AK |
914 | } |
915 | ||
82ba011b | 916 | int __memory_failure(unsigned long pfn, int trapno, int flags) |
6a46079c AK |
917 | { |
918 | struct page_state *ps; | |
919 | struct page *p; | |
920 | int res; | |
921 | ||
922 | if (!sysctl_memory_failure_recovery) | |
923 | panic("Memory failure from trap %d on page %lx", trapno, pfn); | |
924 | ||
925 | if (!pfn_valid(pfn)) { | |
a7560fc8 WF |
926 | printk(KERN_ERR |
927 | "MCE %#lx: memory outside kernel control\n", | |
928 | pfn); | |
929 | return -ENXIO; | |
6a46079c AK |
930 | } |
931 | ||
932 | p = pfn_to_page(pfn); | |
933 | if (TestSetPageHWPoison(p)) { | |
d95ea51e | 934 | printk(KERN_ERR "MCE %#lx: already hardware poisoned\n", pfn); |
6a46079c AK |
935 | return 0; |
936 | } | |
937 | ||
938 | atomic_long_add(1, &mce_bad_pages); | |
939 | ||
940 | /* | |
941 | * We need/can do nothing about count=0 pages. | |
942 | * 1) it's a free page, and therefore in safe hand: | |
943 | * prep_new_page() will be the gate keeper. | |
944 | * 2) it's part of a non-compound high order page. | |
945 | * Implies some kernel user: cannot stop them from | |
946 | * R/W the page; let's pray that the page has been | |
947 | * used and will be freed some time later. | |
948 | * In fact it's dangerous to directly bump up page count from 0, | |
949 | * that may make page_freeze_refs()/page_unfreeze_refs() mismatch. | |
950 | */ | |
82ba011b AK |
951 | if (!(flags & MF_COUNT_INCREASED) && |
952 | !get_page_unless_zero(compound_head(p))) { | |
8d22ba1b WF |
953 | if (is_free_buddy_page(p)) { |
954 | action_result(pfn, "free buddy", DELAYED); | |
955 | return 0; | |
956 | } else { | |
957 | action_result(pfn, "high order kernel", IGNORED); | |
958 | return -EBUSY; | |
959 | } | |
6a46079c AK |
960 | } |
961 | ||
e43c3afb WF |
962 | /* |
963 | * We ignore non-LRU pages for good reasons. | |
964 | * - PG_locked is only well defined for LRU pages and a few others | |
965 | * - to avoid races with __set_page_locked() | |
966 | * - to avoid races with __SetPageSlab*() (and more non-atomic ops) | |
967 | * The check (unnecessarily) ignores LRU pages being isolated and | |
968 | * walked by the page reclaim code, however that's not a big loss. | |
969 | */ | |
970 | if (!PageLRU(p)) | |
facb6011 | 971 | shake_page(p, 0); |
dc2a1cbf | 972 | if (!PageLRU(p)) { |
0474a60e AK |
973 | /* |
974 | * shake_page could have turned it free. | |
975 | */ | |
976 | if (is_free_buddy_page(p)) { | |
977 | action_result(pfn, "free buddy, 2nd try", DELAYED); | |
978 | return 0; | |
979 | } | |
e43c3afb WF |
980 | action_result(pfn, "non LRU", IGNORED); |
981 | put_page(p); | |
982 | return -EBUSY; | |
983 | } | |
e43c3afb | 984 | |
6a46079c AK |
985 | /* |
986 | * Lock the page and wait for writeback to finish. | |
987 | * It's very difficult to mess with pages currently under IO | |
988 | * and in many cases impossible, so we just avoid it here. | |
989 | */ | |
990 | lock_page_nosync(p); | |
847ce401 WF |
991 | |
992 | /* | |
993 | * unpoison always clear PG_hwpoison inside page lock | |
994 | */ | |
995 | if (!PageHWPoison(p)) { | |
d95ea51e | 996 | printk(KERN_ERR "MCE %#lx: just unpoisoned\n", pfn); |
847ce401 WF |
997 | res = 0; |
998 | goto out; | |
999 | } | |
7c116f2b WF |
1000 | if (hwpoison_filter(p)) { |
1001 | if (TestClearPageHWPoison(p)) | |
1002 | atomic_long_dec(&mce_bad_pages); | |
1003 | unlock_page(p); | |
1004 | put_page(p); | |
1005 | return 0; | |
1006 | } | |
847ce401 | 1007 | |
6a46079c AK |
1008 | wait_on_page_writeback(p); |
1009 | ||
1010 | /* | |
1011 | * Now take care of user space mappings. | |
1668bfd5 | 1012 | * Abort on fail: __remove_from_page_cache() assumes unmapped page. |
6a46079c | 1013 | */ |
1668bfd5 WF |
1014 | if (hwpoison_user_mappings(p, pfn, trapno) != SWAP_SUCCESS) { |
1015 | printk(KERN_ERR "MCE %#lx: cannot unmap page, give up\n", pfn); | |
1016 | res = -EBUSY; | |
1017 | goto out; | |
1018 | } | |
6a46079c AK |
1019 | |
1020 | /* | |
1021 | * Torn down by someone else? | |
1022 | */ | |
dc2a1cbf | 1023 | if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) { |
6a46079c | 1024 | action_result(pfn, "already truncated LRU", IGNORED); |
d95ea51e | 1025 | res = -EBUSY; |
6a46079c AK |
1026 | goto out; |
1027 | } | |
1028 | ||
1029 | res = -EBUSY; | |
1030 | for (ps = error_states;; ps++) { | |
dc2a1cbf | 1031 | if ((p->flags & ps->mask) == ps->res) { |
bd1ce5f9 | 1032 | res = page_action(ps, p, pfn); |
6a46079c AK |
1033 | break; |
1034 | } | |
1035 | } | |
1036 | out: | |
1037 | unlock_page(p); | |
1038 | return res; | |
1039 | } | |
1040 | EXPORT_SYMBOL_GPL(__memory_failure); | |
1041 | ||
1042 | /** | |
1043 | * memory_failure - Handle memory failure of a page. | |
1044 | * @pfn: Page Number of the corrupted page | |
1045 | * @trapno: Trap number reported in the signal to user space. | |
1046 | * | |
1047 | * This function is called by the low level machine check code | |
1048 | * of an architecture when it detects hardware memory corruption | |
1049 | * of a page. It tries its best to recover, which includes | |
1050 | * dropping pages, killing processes etc. | |
1051 | * | |
1052 | * The function is primarily of use for corruptions that | |
1053 | * happen outside the current execution context (e.g. when | |
1054 | * detected by a background scrubber) | |
1055 | * | |
1056 | * Must run in process context (e.g. a work queue) with interrupts | |
1057 | * enabled and no spinlocks hold. | |
1058 | */ | |
1059 | void memory_failure(unsigned long pfn, int trapno) | |
1060 | { | |
1061 | __memory_failure(pfn, trapno, 0); | |
1062 | } | |
847ce401 WF |
1063 | |
1064 | /** | |
1065 | * unpoison_memory - Unpoison a previously poisoned page | |
1066 | * @pfn: Page number of the to be unpoisoned page | |
1067 | * | |
1068 | * Software-unpoison a page that has been poisoned by | |
1069 | * memory_failure() earlier. | |
1070 | * | |
1071 | * This is only done on the software-level, so it only works | |
1072 | * for linux injected failures, not real hardware failures | |
1073 | * | |
1074 | * Returns 0 for success, otherwise -errno. | |
1075 | */ | |
1076 | int unpoison_memory(unsigned long pfn) | |
1077 | { | |
1078 | struct page *page; | |
1079 | struct page *p; | |
1080 | int freeit = 0; | |
1081 | ||
1082 | if (!pfn_valid(pfn)) | |
1083 | return -ENXIO; | |
1084 | ||
1085 | p = pfn_to_page(pfn); | |
1086 | page = compound_head(p); | |
1087 | ||
1088 | if (!PageHWPoison(p)) { | |
1089 | pr_debug("MCE: Page was already unpoisoned %#lx\n", pfn); | |
1090 | return 0; | |
1091 | } | |
1092 | ||
1093 | if (!get_page_unless_zero(page)) { | |
1094 | if (TestClearPageHWPoison(p)) | |
1095 | atomic_long_dec(&mce_bad_pages); | |
1096 | pr_debug("MCE: Software-unpoisoned free page %#lx\n", pfn); | |
1097 | return 0; | |
1098 | } | |
1099 | ||
1100 | lock_page_nosync(page); | |
1101 | /* | |
1102 | * This test is racy because PG_hwpoison is set outside of page lock. | |
1103 | * That's acceptable because that won't trigger kernel panic. Instead, | |
1104 | * the PG_hwpoison page will be caught and isolated on the entrance to | |
1105 | * the free buddy page pool. | |
1106 | */ | |
1107 | if (TestClearPageHWPoison(p)) { | |
1108 | pr_debug("MCE: Software-unpoisoned page %#lx\n", pfn); | |
1109 | atomic_long_dec(&mce_bad_pages); | |
1110 | freeit = 1; | |
1111 | } | |
1112 | unlock_page(page); | |
1113 | ||
1114 | put_page(page); | |
1115 | if (freeit) | |
1116 | put_page(page); | |
1117 | ||
1118 | return 0; | |
1119 | } | |
1120 | EXPORT_SYMBOL(unpoison_memory); | |
facb6011 AK |
1121 | |
1122 | static struct page *new_page(struct page *p, unsigned long private, int **x) | |
1123 | { | |
12686d15 AK |
1124 | int nid = page_to_nid(p); |
1125 | return alloc_pages_exact_node(nid, GFP_HIGHUSER_MOVABLE, 0); | |
facb6011 AK |
1126 | } |
1127 | ||
1128 | /* | |
1129 | * Safely get reference count of an arbitrary page. | |
1130 | * Returns 0 for a free page, -EIO for a zero refcount page | |
1131 | * that is not free, and 1 for any other page type. | |
1132 | * For 1 the page is returned with increased page count, otherwise not. | |
1133 | */ | |
1134 | static int get_any_page(struct page *p, unsigned long pfn, int flags) | |
1135 | { | |
1136 | int ret; | |
1137 | ||
1138 | if (flags & MF_COUNT_INCREASED) | |
1139 | return 1; | |
1140 | ||
1141 | /* | |
1142 | * The lock_system_sleep prevents a race with memory hotplug, | |
1143 | * because the isolation assumes there's only a single user. | |
1144 | * This is a big hammer, a better would be nicer. | |
1145 | */ | |
1146 | lock_system_sleep(); | |
1147 | ||
1148 | /* | |
1149 | * Isolate the page, so that it doesn't get reallocated if it | |
1150 | * was free. | |
1151 | */ | |
1152 | set_migratetype_isolate(p); | |
1153 | if (!get_page_unless_zero(compound_head(p))) { | |
1154 | if (is_free_buddy_page(p)) { | |
1155 | pr_debug("get_any_page: %#lx free buddy page\n", pfn); | |
1156 | /* Set hwpoison bit while page is still isolated */ | |
1157 | SetPageHWPoison(p); | |
1158 | ret = 0; | |
1159 | } else { | |
1160 | pr_debug("get_any_page: %#lx: unknown zero refcount page type %lx\n", | |
1161 | pfn, p->flags); | |
1162 | ret = -EIO; | |
1163 | } | |
1164 | } else { | |
1165 | /* Not a free page */ | |
1166 | ret = 1; | |
1167 | } | |
1168 | unset_migratetype_isolate(p); | |
1169 | unlock_system_sleep(); | |
1170 | return ret; | |
1171 | } | |
1172 | ||
1173 | /** | |
1174 | * soft_offline_page - Soft offline a page. | |
1175 | * @page: page to offline | |
1176 | * @flags: flags. Same as memory_failure(). | |
1177 | * | |
1178 | * Returns 0 on success, otherwise negated errno. | |
1179 | * | |
1180 | * Soft offline a page, by migration or invalidation, | |
1181 | * without killing anything. This is for the case when | |
1182 | * a page is not corrupted yet (so it's still valid to access), | |
1183 | * but has had a number of corrected errors and is better taken | |
1184 | * out. | |
1185 | * | |
1186 | * The actual policy on when to do that is maintained by | |
1187 | * user space. | |
1188 | * | |
1189 | * This should never impact any application or cause data loss, | |
1190 | * however it might take some time. | |
1191 | * | |
1192 | * This is not a 100% solution for all memory, but tries to be | |
1193 | * ``good enough'' for the majority of memory. | |
1194 | */ | |
1195 | int soft_offline_page(struct page *page, int flags) | |
1196 | { | |
1197 | int ret; | |
1198 | unsigned long pfn = page_to_pfn(page); | |
1199 | ||
1200 | ret = get_any_page(page, pfn, flags); | |
1201 | if (ret < 0) | |
1202 | return ret; | |
1203 | if (ret == 0) | |
1204 | goto done; | |
1205 | ||
1206 | /* | |
1207 | * Page cache page we can handle? | |
1208 | */ | |
1209 | if (!PageLRU(page)) { | |
1210 | /* | |
1211 | * Try to free it. | |
1212 | */ | |
1213 | put_page(page); | |
1214 | shake_page(page, 1); | |
1215 | ||
1216 | /* | |
1217 | * Did it turn free? | |
1218 | */ | |
1219 | ret = get_any_page(page, pfn, 0); | |
1220 | if (ret < 0) | |
1221 | return ret; | |
1222 | if (ret == 0) | |
1223 | goto done; | |
1224 | } | |
1225 | if (!PageLRU(page)) { | |
1226 | pr_debug("soft_offline: %#lx: unknown non LRU page type %lx\n", | |
1227 | pfn, page->flags); | |
1228 | return -EIO; | |
1229 | } | |
1230 | ||
1231 | lock_page(page); | |
1232 | wait_on_page_writeback(page); | |
1233 | ||
1234 | /* | |
1235 | * Synchronized using the page lock with memory_failure() | |
1236 | */ | |
1237 | if (PageHWPoison(page)) { | |
1238 | unlock_page(page); | |
1239 | put_page(page); | |
1240 | pr_debug("soft offline: %#lx page already poisoned\n", pfn); | |
1241 | return -EBUSY; | |
1242 | } | |
1243 | ||
1244 | /* | |
1245 | * Try to invalidate first. This should work for | |
1246 | * non dirty unmapped page cache pages. | |
1247 | */ | |
1248 | ret = invalidate_inode_page(page); | |
1249 | unlock_page(page); | |
1250 | ||
1251 | /* | |
1252 | * Drop count because page migration doesn't like raised | |
1253 | * counts. The page could get re-allocated, but if it becomes | |
1254 | * LRU the isolation will just fail. | |
1255 | * RED-PEN would be better to keep it isolated here, but we | |
1256 | * would need to fix isolation locking first. | |
1257 | */ | |
1258 | put_page(page); | |
1259 | if (ret == 1) { | |
1260 | ret = 0; | |
1261 | pr_debug("soft_offline: %#lx: invalidated\n", pfn); | |
1262 | goto done; | |
1263 | } | |
1264 | ||
1265 | /* | |
1266 | * Simple invalidation didn't work. | |
1267 | * Try to migrate to a new page instead. migrate.c | |
1268 | * handles a large number of cases for us. | |
1269 | */ | |
1270 | ret = isolate_lru_page(page); | |
1271 | if (!ret) { | |
1272 | LIST_HEAD(pagelist); | |
1273 | ||
1274 | list_add(&page->lru, &pagelist); | |
1275 | ret = migrate_pages(&pagelist, new_page, MPOL_MF_MOVE_ALL, 0); | |
1276 | if (ret) { | |
1277 | pr_debug("soft offline: %#lx: migration failed %d, type %lx\n", | |
1278 | pfn, ret, page->flags); | |
1279 | if (ret > 0) | |
1280 | ret = -EIO; | |
1281 | } | |
1282 | } else { | |
1283 | pr_debug("soft offline: %#lx: isolation failed: %d, page count %d, type %lx\n", | |
1284 | pfn, ret, page_count(page), page->flags); | |
1285 | } | |
1286 | if (ret) | |
1287 | return ret; | |
1288 | ||
1289 | done: | |
1290 | atomic_long_add(1, &mce_bad_pages); | |
1291 | SetPageHWPoison(page); | |
1292 | /* keep elevated page count for bad page */ | |
1293 | return ret; | |
1294 | } |