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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 multi-bit ECC memory or cache
11 * failure.
12 *
13 * In addition there is a "soft offline" entry point that allows stop using
14 * not-yet-corrupted-by-suspicious pages without killing anything.
15 *
16 * Handles page cache pages in various states. The tricky part
17 * here is that we can access any page asynchronously in respect to
18 * other VM users, because memory failures could happen anytime and
19 * anywhere. This could violate some of their assumptions. This is why
20 * this code has to be extremely careful. Generally it tries to use
21 * normal locking rules, as in get the standard locks, even if that means
22 * the error handling takes potentially a long time.
23 *
24 * It can be very tempting to add handling for obscure cases here.
25 * In general any code for handling new cases should only be added iff:
26 * - You know how to test it.
27 * - You have a test that can be added to mce-test
28 * https://git.kernel.org/cgit/utils/cpu/mce/mce-test.git/
29 * - The case actually shows up as a frequent (top 10) page state in
30 * tools/vm/page-types when running a real workload.
31 *
32 * There are several operations here with exponential complexity because
33 * of unsuitable VM data structures. For example the operation to map back
34 * from RMAP chains to processes has to walk the complete process list and
35 * has non linear complexity with the number. But since memory corruptions
36 * are rare we hope to get away with this. This avoids impacting the core
37 * VM.
38 */
39#include <linux/kernel.h>
40#include <linux/mm.h>
41#include <linux/page-flags.h>
42#include <linux/kernel-page-flags.h>
43#include <linux/sched.h>
44#include <linux/ksm.h>
45#include <linux/rmap.h>
46#include <linux/export.h>
47#include <linux/pagemap.h>
48#include <linux/swap.h>
49#include <linux/backing-dev.h>
50#include <linux/migrate.h>
51#include <linux/page-isolation.h>
52#include <linux/suspend.h>
53#include <linux/slab.h>
54#include <linux/swapops.h>
55#include <linux/hugetlb.h>
56#include <linux/memory_hotplug.h>
57#include <linux/mm_inline.h>
58#include <linux/kfifo.h>
59#include <linux/ratelimit.h>
60#include "internal.h"
61#include "ras/ras_event.h"
62
63int sysctl_memory_failure_early_kill __read_mostly = 0;
64
65int sysctl_memory_failure_recovery __read_mostly = 1;
66
67atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0);
68
69#if defined(CONFIG_HWPOISON_INJECT) || defined(CONFIG_HWPOISON_INJECT_MODULE)
70
71u32 hwpoison_filter_enable = 0;
72u32 hwpoison_filter_dev_major = ~0U;
73u32 hwpoison_filter_dev_minor = ~0U;
74u64 hwpoison_filter_flags_mask;
75u64 hwpoison_filter_flags_value;
76EXPORT_SYMBOL_GPL(hwpoison_filter_enable);
77EXPORT_SYMBOL_GPL(hwpoison_filter_dev_major);
78EXPORT_SYMBOL_GPL(hwpoison_filter_dev_minor);
79EXPORT_SYMBOL_GPL(hwpoison_filter_flags_mask);
80EXPORT_SYMBOL_GPL(hwpoison_filter_flags_value);
81
82static int hwpoison_filter_dev(struct page *p)
83{
84 struct address_space *mapping;
85 dev_t dev;
86
87 if (hwpoison_filter_dev_major == ~0U &&
88 hwpoison_filter_dev_minor == ~0U)
89 return 0;
90
91 /*
92 * page_mapping() does not accept slab pages.
93 */
94 if (PageSlab(p))
95 return -EINVAL;
96
97 mapping = page_mapping(p);
98 if (mapping == NULL || mapping->host == NULL)
99 return -EINVAL;
100
101 dev = mapping->host->i_sb->s_dev;
102 if (hwpoison_filter_dev_major != ~0U &&
103 hwpoison_filter_dev_major != MAJOR(dev))
104 return -EINVAL;
105 if (hwpoison_filter_dev_minor != ~0U &&
106 hwpoison_filter_dev_minor != MINOR(dev))
107 return -EINVAL;
108
109 return 0;
110}
111
112static int hwpoison_filter_flags(struct page *p)
113{
114 if (!hwpoison_filter_flags_mask)
115 return 0;
116
117 if ((stable_page_flags(p) & hwpoison_filter_flags_mask) ==
118 hwpoison_filter_flags_value)
119 return 0;
120 else
121 return -EINVAL;
122}
123
124/*
125 * This allows stress tests to limit test scope to a collection of tasks
126 * by putting them under some memcg. This prevents killing unrelated/important
127 * processes such as /sbin/init. Note that the target task may share clean
128 * pages with init (eg. libc text), which is harmless. If the target task
129 * share _dirty_ pages with another task B, the test scheme must make sure B
130 * is also included in the memcg. At last, due to race conditions this filter
131 * can only guarantee that the page either belongs to the memcg tasks, or is
132 * a freed page.
133 */
134#ifdef CONFIG_MEMCG
135u64 hwpoison_filter_memcg;
136EXPORT_SYMBOL_GPL(hwpoison_filter_memcg);
137static int hwpoison_filter_task(struct page *p)
138{
139 if (!hwpoison_filter_memcg)
140 return 0;
141
142 if (page_cgroup_ino(p) != hwpoison_filter_memcg)
143 return -EINVAL;
144
145 return 0;
146}
147#else
148static int hwpoison_filter_task(struct page *p) { return 0; }
149#endif
150
151int hwpoison_filter(struct page *p)
152{
153 if (!hwpoison_filter_enable)
154 return 0;
155
156 if (hwpoison_filter_dev(p))
157 return -EINVAL;
158
159 if (hwpoison_filter_flags(p))
160 return -EINVAL;
161
162 if (hwpoison_filter_task(p))
163 return -EINVAL;
164
165 return 0;
166}
167#else
168int hwpoison_filter(struct page *p)
169{
170 return 0;
171}
172#endif
173
174EXPORT_SYMBOL_GPL(hwpoison_filter);
175
176/*
177 * Send all the processes who have the page mapped a signal.
178 * ``action optional'' if they are not immediately affected by the error
179 * ``action required'' if error happened in current execution context
180 */
181static int kill_proc(struct task_struct *t, unsigned long addr, int trapno,
182 unsigned long pfn, struct page *page, int flags)
183{
184 struct siginfo si;
185 int ret;
186
187 pr_err("MCE %#lx: Killing %s:%d due to hardware memory corruption\n",
188 pfn, t->comm, t->pid);
189 si.si_signo = SIGBUS;
190 si.si_errno = 0;
191 si.si_addr = (void *)addr;
192#ifdef __ARCH_SI_TRAPNO
193 si.si_trapno = trapno;
194#endif
195 si.si_addr_lsb = compound_order(compound_head(page)) + PAGE_SHIFT;
196
197 if ((flags & MF_ACTION_REQUIRED) && t->mm == current->mm) {
198 si.si_code = BUS_MCEERR_AR;
199 ret = force_sig_info(SIGBUS, &si, current);
200 } else {
201 /*
202 * Don't use force here, it's convenient if the signal
203 * can be temporarily blocked.
204 * This could cause a loop when the user sets SIGBUS
205 * to SIG_IGN, but hopefully no one will do that?
206 */
207 si.si_code = BUS_MCEERR_AO;
208 ret = send_sig_info(SIGBUS, &si, t); /* synchronous? */
209 }
210 if (ret < 0)
211 pr_info("MCE: Error sending signal to %s:%d: %d\n",
212 t->comm, t->pid, ret);
213 return ret;
214}
215
216/*
217 * When a unknown page type is encountered drain as many buffers as possible
218 * in the hope to turn the page into a LRU or free page, which we can handle.
219 */
220void shake_page(struct page *p, int access)
221{
222 if (!PageSlab(p)) {
223 lru_add_drain_all();
224 if (PageLRU(p))
225 return;
226 drain_all_pages(page_zone(p));
227 if (PageLRU(p) || is_free_buddy_page(p))
228 return;
229 }
230
231 /*
232 * Only call shrink_node_slabs here (which would also shrink
233 * other caches) if access is not potentially fatal.
234 */
235 if (access)
236 drop_slab_node(page_to_nid(p));
237}
238EXPORT_SYMBOL_GPL(shake_page);
239
240/*
241 * Kill all processes that have a poisoned page mapped and then isolate
242 * the page.
243 *
244 * General strategy:
245 * Find all processes having the page mapped and kill them.
246 * But we keep a page reference around so that the page is not
247 * actually freed yet.
248 * Then stash the page away
249 *
250 * There's no convenient way to get back to mapped processes
251 * from the VMAs. So do a brute-force search over all
252 * running processes.
253 *
254 * Remember that machine checks are not common (or rather
255 * if they are common you have other problems), so this shouldn't
256 * be a performance issue.
257 *
258 * Also there are some races possible while we get from the
259 * error detection to actually handle it.
260 */
261
262struct to_kill {
263 struct list_head nd;
264 struct task_struct *tsk;
265 unsigned long addr;
266 char addr_valid;
267};
268
269/*
270 * Failure handling: if we can't find or can't kill a process there's
271 * not much we can do. We just print a message and ignore otherwise.
272 */
273
274/*
275 * Schedule a process for later kill.
276 * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
277 * TBD would GFP_NOIO be enough?
278 */
279static void add_to_kill(struct task_struct *tsk, struct page *p,
280 struct vm_area_struct *vma,
281 struct list_head *to_kill,
282 struct to_kill **tkc)
283{
284 struct to_kill *tk;
285
286 if (*tkc) {
287 tk = *tkc;
288 *tkc = NULL;
289 } else {
290 tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
291 if (!tk) {
292 pr_err("MCE: Out of memory while machine check handling\n");
293 return;
294 }
295 }
296 tk->addr = page_address_in_vma(p, vma);
297 tk->addr_valid = 1;
298
299 /*
300 * In theory we don't have to kill when the page was
301 * munmaped. But it could be also a mremap. Since that's
302 * likely very rare kill anyways just out of paranoia, but use
303 * a SIGKILL because the error is not contained anymore.
304 */
305 if (tk->addr == -EFAULT) {
306 pr_info("MCE: Unable to find user space address %lx in %s\n",
307 page_to_pfn(p), tsk->comm);
308 tk->addr_valid = 0;
309 }
310 get_task_struct(tsk);
311 tk->tsk = tsk;
312 list_add_tail(&tk->nd, to_kill);
313}
314
315/*
316 * Kill the processes that have been collected earlier.
317 *
318 * Only do anything when DOIT is set, otherwise just free the list
319 * (this is used for clean pages which do not need killing)
320 * Also when FAIL is set do a force kill because something went
321 * wrong earlier.
322 */
323static void kill_procs(struct list_head *to_kill, int forcekill, int trapno,
324 int fail, struct page *page, unsigned long pfn,
325 int flags)
326{
327 struct to_kill *tk, *next;
328
329 list_for_each_entry_safe (tk, next, to_kill, nd) {
330 if (forcekill) {
331 /*
332 * In case something went wrong with munmapping
333 * make sure the process doesn't catch the
334 * signal and then access the memory. Just kill it.
335 */
336 if (fail || tk->addr_valid == 0) {
337 pr_err("MCE %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n",
338 pfn, tk->tsk->comm, tk->tsk->pid);
339 force_sig(SIGKILL, tk->tsk);
340 }
341
342 /*
343 * In theory the process could have mapped
344 * something else on the address in-between. We could
345 * check for that, but we need to tell the
346 * process anyways.
347 */
348 else if (kill_proc(tk->tsk, tk->addr, trapno,
349 pfn, page, flags) < 0)
350 pr_err("MCE %#lx: Cannot send advisory machine check signal to %s:%d\n",
351 pfn, tk->tsk->comm, tk->tsk->pid);
352 }
353 put_task_struct(tk->tsk);
354 kfree(tk);
355 }
356}
357
358/*
359 * Find a dedicated thread which is supposed to handle SIGBUS(BUS_MCEERR_AO)
360 * on behalf of the thread group. Return task_struct of the (first found)
361 * dedicated thread if found, and return NULL otherwise.
362 *
363 * We already hold read_lock(&tasklist_lock) in the caller, so we don't
364 * have to call rcu_read_lock/unlock() in this function.
365 */
366static struct task_struct *find_early_kill_thread(struct task_struct *tsk)
367{
368 struct task_struct *t;
369
370 for_each_thread(tsk, t)
371 if ((t->flags & PF_MCE_PROCESS) && (t->flags & PF_MCE_EARLY))
372 return t;
373 return NULL;
374}
375
376/*
377 * Determine whether a given process is "early kill" process which expects
378 * to be signaled when some page under the process is hwpoisoned.
379 * Return task_struct of the dedicated thread (main thread unless explicitly
380 * specified) if the process is "early kill," and otherwise returns NULL.
381 */
382static struct task_struct *task_early_kill(struct task_struct *tsk,
383 int force_early)
384{
385 struct task_struct *t;
386 if (!tsk->mm)
387 return NULL;
388 if (force_early)
389 return tsk;
390 t = find_early_kill_thread(tsk);
391 if (t)
392 return t;
393 if (sysctl_memory_failure_early_kill)
394 return tsk;
395 return NULL;
396}
397
398/*
399 * Collect processes when the error hit an anonymous page.
400 */
401static void collect_procs_anon(struct page *page, struct list_head *to_kill,
402 struct to_kill **tkc, int force_early)
403{
404 struct vm_area_struct *vma;
405 struct task_struct *tsk;
406 struct anon_vma *av;
407 pgoff_t pgoff;
408
409 av = page_lock_anon_vma_read(page);
410 if (av == NULL) /* Not actually mapped anymore */
411 return;
412
413 pgoff = page_to_pgoff(page);
414 read_lock(&tasklist_lock);
415 for_each_process (tsk) {
416 struct anon_vma_chain *vmac;
417 struct task_struct *t = task_early_kill(tsk, force_early);
418
419 if (!t)
420 continue;
421 anon_vma_interval_tree_foreach(vmac, &av->rb_root,
422 pgoff, pgoff) {
423 vma = vmac->vma;
424 if (!page_mapped_in_vma(page, vma))
425 continue;
426 if (vma->vm_mm == t->mm)
427 add_to_kill(t, page, vma, to_kill, tkc);
428 }
429 }
430 read_unlock(&tasklist_lock);
431 page_unlock_anon_vma_read(av);
432}
433
434/*
435 * Collect processes when the error hit a file mapped page.
436 */
437static void collect_procs_file(struct page *page, struct list_head *to_kill,
438 struct to_kill **tkc, int force_early)
439{
440 struct vm_area_struct *vma;
441 struct task_struct *tsk;
442 struct address_space *mapping = page->mapping;
443
444 i_mmap_lock_read(mapping);
445 read_lock(&tasklist_lock);
446 for_each_process(tsk) {
447 pgoff_t pgoff = page_to_pgoff(page);
448 struct task_struct *t = task_early_kill(tsk, force_early);
449
450 if (!t)
451 continue;
452 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff,
453 pgoff) {
454 /*
455 * Send early kill signal to tasks where a vma covers
456 * the page but the corrupted page is not necessarily
457 * mapped it in its pte.
458 * Assume applications who requested early kill want
459 * to be informed of all such data corruptions.
460 */
461 if (vma->vm_mm == t->mm)
462 add_to_kill(t, page, vma, to_kill, tkc);
463 }
464 }
465 read_unlock(&tasklist_lock);
466 i_mmap_unlock_read(mapping);
467}
468
469/*
470 * Collect the processes who have the corrupted page mapped to kill.
471 * This is done in two steps for locking reasons.
472 * First preallocate one tokill structure outside the spin locks,
473 * so that we can kill at least one process reasonably reliable.
474 */
475static void collect_procs(struct page *page, struct list_head *tokill,
476 int force_early)
477{
478 struct to_kill *tk;
479
480 if (!page->mapping)
481 return;
482
483 tk = kmalloc(sizeof(struct to_kill), GFP_NOIO);
484 if (!tk)
485 return;
486 if (PageAnon(page))
487 collect_procs_anon(page, tokill, &tk, force_early);
488 else
489 collect_procs_file(page, tokill, &tk, force_early);
490 kfree(tk);
491}
492
493static const char *action_name[] = {
494 [MF_IGNORED] = "Ignored",
495 [MF_FAILED] = "Failed",
496 [MF_DELAYED] = "Delayed",
497 [MF_RECOVERED] = "Recovered",
498};
499
500static const char * const action_page_types[] = {
501 [MF_MSG_KERNEL] = "reserved kernel page",
502 [MF_MSG_KERNEL_HIGH_ORDER] = "high-order kernel page",
503 [MF_MSG_SLAB] = "kernel slab page",
504 [MF_MSG_DIFFERENT_COMPOUND] = "different compound page after locking",
505 [MF_MSG_POISONED_HUGE] = "huge page already hardware poisoned",
506 [MF_MSG_HUGE] = "huge page",
507 [MF_MSG_FREE_HUGE] = "free huge page",
508 [MF_MSG_UNMAP_FAILED] = "unmapping failed page",
509 [MF_MSG_DIRTY_SWAPCACHE] = "dirty swapcache page",
510 [MF_MSG_CLEAN_SWAPCACHE] = "clean swapcache page",
511 [MF_MSG_DIRTY_MLOCKED_LRU] = "dirty mlocked LRU page",
512 [MF_MSG_CLEAN_MLOCKED_LRU] = "clean mlocked LRU page",
513 [MF_MSG_DIRTY_UNEVICTABLE_LRU] = "dirty unevictable LRU page",
514 [MF_MSG_CLEAN_UNEVICTABLE_LRU] = "clean unevictable LRU page",
515 [MF_MSG_DIRTY_LRU] = "dirty LRU page",
516 [MF_MSG_CLEAN_LRU] = "clean LRU page",
517 [MF_MSG_TRUNCATED_LRU] = "already truncated LRU page",
518 [MF_MSG_BUDDY] = "free buddy page",
519 [MF_MSG_BUDDY_2ND] = "free buddy page (2nd try)",
520 [MF_MSG_UNKNOWN] = "unknown page",
521};
522
523/*
524 * XXX: It is possible that a page is isolated from LRU cache,
525 * and then kept in swap cache or failed to remove from page cache.
526 * The page count will stop it from being freed by unpoison.
527 * Stress tests should be aware of this memory leak problem.
528 */
529static int delete_from_lru_cache(struct page *p)
530{
531 if (!isolate_lru_page(p)) {
532 /*
533 * Clear sensible page flags, so that the buddy system won't
534 * complain when the page is unpoison-and-freed.
535 */
536 ClearPageActive(p);
537 ClearPageUnevictable(p);
538 /*
539 * drop the page count elevated by isolate_lru_page()
540 */
541 put_page(p);
542 return 0;
543 }
544 return -EIO;
545}
546
547/*
548 * Error hit kernel page.
549 * Do nothing, try to be lucky and not touch this instead. For a few cases we
550 * could be more sophisticated.
551 */
552static int me_kernel(struct page *p, unsigned long pfn)
553{
554 return MF_IGNORED;
555}
556
557/*
558 * Page in unknown state. Do nothing.
559 */
560static int me_unknown(struct page *p, unsigned long pfn)
561{
562 pr_err("MCE %#lx: Unknown page state\n", pfn);
563 return MF_FAILED;
564}
565
566/*
567 * Clean (or cleaned) page cache page.
568 */
569static int me_pagecache_clean(struct page *p, unsigned long pfn)
570{
571 int err;
572 int ret = MF_FAILED;
573 struct address_space *mapping;
574
575 delete_from_lru_cache(p);
576
577 /*
578 * For anonymous pages we're done the only reference left
579 * should be the one m_f() holds.
580 */
581 if (PageAnon(p))
582 return MF_RECOVERED;
583
584 /*
585 * Now truncate the page in the page cache. This is really
586 * more like a "temporary hole punch"
587 * Don't do this for block devices when someone else
588 * has a reference, because it could be file system metadata
589 * and that's not safe to truncate.
590 */
591 mapping = page_mapping(p);
592 if (!mapping) {
593 /*
594 * Page has been teared down in the meanwhile
595 */
596 return MF_FAILED;
597 }
598
599 /*
600 * Truncation is a bit tricky. Enable it per file system for now.
601 *
602 * Open: to take i_mutex or not for this? Right now we don't.
603 */
604 if (mapping->a_ops->error_remove_page) {
605 err = mapping->a_ops->error_remove_page(mapping, p);
606 if (err != 0) {
607 pr_info("MCE %#lx: Failed to punch page: %d\n",
608 pfn, err);
609 } else if (page_has_private(p) &&
610 !try_to_release_page(p, GFP_NOIO)) {
611 pr_info("MCE %#lx: failed to release buffers\n", pfn);
612 } else {
613 ret = MF_RECOVERED;
614 }
615 } else {
616 /*
617 * If the file system doesn't support it just invalidate
618 * This fails on dirty or anything with private pages
619 */
620 if (invalidate_inode_page(p))
621 ret = MF_RECOVERED;
622 else
623 pr_info("MCE %#lx: Failed to invalidate\n", pfn);
624 }
625 return ret;
626}
627
628/*
629 * Dirty pagecache page
630 * Issues: when the error hit a hole page the error is not properly
631 * propagated.
632 */
633static int me_pagecache_dirty(struct page *p, unsigned long pfn)
634{
635 struct address_space *mapping = page_mapping(p);
636
637 SetPageError(p);
638 /* TBD: print more information about the file. */
639 if (mapping) {
640 /*
641 * IO error will be reported by write(), fsync(), etc.
642 * who check the mapping.
643 * This way the application knows that something went
644 * wrong with its dirty file data.
645 *
646 * There's one open issue:
647 *
648 * The EIO will be only reported on the next IO
649 * operation and then cleared through the IO map.
650 * Normally Linux has two mechanisms to pass IO error
651 * first through the AS_EIO flag in the address space
652 * and then through the PageError flag in the page.
653 * Since we drop pages on memory failure handling the
654 * only mechanism open to use is through AS_AIO.
655 *
656 * This has the disadvantage that it gets cleared on
657 * the first operation that returns an error, while
658 * the PageError bit is more sticky and only cleared
659 * when the page is reread or dropped. If an
660 * application assumes it will always get error on
661 * fsync, but does other operations on the fd before
662 * and the page is dropped between then the error
663 * will not be properly reported.
664 *
665 * This can already happen even without hwpoisoned
666 * pages: first on metadata IO errors (which only
667 * report through AS_EIO) or when the page is dropped
668 * at the wrong time.
669 *
670 * So right now we assume that the application DTRT on
671 * the first EIO, but we're not worse than other parts
672 * of the kernel.
673 */
674 mapping_set_error(mapping, EIO);
675 }
676
677 return me_pagecache_clean(p, pfn);
678}
679
680/*
681 * Clean and dirty swap cache.
682 *
683 * Dirty swap cache page is tricky to handle. The page could live both in page
684 * cache and swap cache(ie. page is freshly swapped in). So it could be
685 * referenced concurrently by 2 types of PTEs:
686 * normal PTEs and swap PTEs. We try to handle them consistently by calling
687 * try_to_unmap(TTU_IGNORE_HWPOISON) to convert the normal PTEs to swap PTEs,
688 * and then
689 * - clear dirty bit to prevent IO
690 * - remove from LRU
691 * - but keep in the swap cache, so that when we return to it on
692 * a later page fault, we know the application is accessing
693 * corrupted data and shall be killed (we installed simple
694 * interception code in do_swap_page to catch it).
695 *
696 * Clean swap cache pages can be directly isolated. A later page fault will
697 * bring in the known good data from disk.
698 */
699static int me_swapcache_dirty(struct page *p, unsigned long pfn)
700{
701 ClearPageDirty(p);
702 /* Trigger EIO in shmem: */
703 ClearPageUptodate(p);
704
705 if (!delete_from_lru_cache(p))
706 return MF_DELAYED;
707 else
708 return MF_FAILED;
709}
710
711static int me_swapcache_clean(struct page *p, unsigned long pfn)
712{
713 delete_from_swap_cache(p);
714
715 if (!delete_from_lru_cache(p))
716 return MF_RECOVERED;
717 else
718 return MF_FAILED;
719}
720
721/*
722 * Huge pages. Needs work.
723 * Issues:
724 * - Error on hugepage is contained in hugepage unit (not in raw page unit.)
725 * To narrow down kill region to one page, we need to break up pmd.
726 */
727static int me_huge_page(struct page *p, unsigned long pfn)
728{
729 int res = 0;
730 struct page *hpage = compound_head(p);
731
732 if (!PageHuge(hpage))
733 return MF_DELAYED;
734
735 /*
736 * We can safely recover from error on free or reserved (i.e.
737 * not in-use) hugepage by dequeuing it from freelist.
738 * To check whether a hugepage is in-use or not, we can't use
739 * page->lru because it can be used in other hugepage operations,
740 * such as __unmap_hugepage_range() and gather_surplus_pages().
741 * So instead we use page_mapping() and PageAnon().
742 * We assume that this function is called with page lock held,
743 * so there is no race between isolation and mapping/unmapping.
744 */
745 if (!(page_mapping(hpage) || PageAnon(hpage))) {
746 res = dequeue_hwpoisoned_huge_page(hpage);
747 if (!res)
748 return MF_RECOVERED;
749 }
750 return MF_DELAYED;
751}
752
753/*
754 * Various page states we can handle.
755 *
756 * A page state is defined by its current page->flags bits.
757 * The table matches them in order and calls the right handler.
758 *
759 * This is quite tricky because we can access page at any time
760 * in its live cycle, so all accesses have to be extremely careful.
761 *
762 * This is not complete. More states could be added.
763 * For any missing state don't attempt recovery.
764 */
765
766#define dirty (1UL << PG_dirty)
767#define sc (1UL << PG_swapcache)
768#define unevict (1UL << PG_unevictable)
769#define mlock (1UL << PG_mlocked)
770#define writeback (1UL << PG_writeback)
771#define lru (1UL << PG_lru)
772#define swapbacked (1UL << PG_swapbacked)
773#define head (1UL << PG_head)
774#define slab (1UL << PG_slab)
775#define reserved (1UL << PG_reserved)
776
777static struct page_state {
778 unsigned long mask;
779 unsigned long res;
780 enum mf_action_page_type type;
781 int (*action)(struct page *p, unsigned long pfn);
782} error_states[] = {
783 { reserved, reserved, MF_MSG_KERNEL, me_kernel },
784 /*
785 * free pages are specially detected outside this table:
786 * PG_buddy pages only make a small fraction of all free pages.
787 */
788
789 /*
790 * Could in theory check if slab page is free or if we can drop
791 * currently unused objects without touching them. But just
792 * treat it as standard kernel for now.
793 */
794 { slab, slab, MF_MSG_SLAB, me_kernel },
795
796 { head, head, MF_MSG_HUGE, me_huge_page },
797
798 { sc|dirty, sc|dirty, MF_MSG_DIRTY_SWAPCACHE, me_swapcache_dirty },
799 { sc|dirty, sc, MF_MSG_CLEAN_SWAPCACHE, me_swapcache_clean },
800
801 { mlock|dirty, mlock|dirty, MF_MSG_DIRTY_MLOCKED_LRU, me_pagecache_dirty },
802 { mlock|dirty, mlock, MF_MSG_CLEAN_MLOCKED_LRU, me_pagecache_clean },
803
804 { unevict|dirty, unevict|dirty, MF_MSG_DIRTY_UNEVICTABLE_LRU, me_pagecache_dirty },
805 { unevict|dirty, unevict, MF_MSG_CLEAN_UNEVICTABLE_LRU, me_pagecache_clean },
806
807 { lru|dirty, lru|dirty, MF_MSG_DIRTY_LRU, me_pagecache_dirty },
808 { lru|dirty, lru, MF_MSG_CLEAN_LRU, me_pagecache_clean },
809
810 /*
811 * Catchall entry: must be at end.
812 */
813 { 0, 0, MF_MSG_UNKNOWN, me_unknown },
814};
815
816#undef dirty
817#undef sc
818#undef unevict
819#undef mlock
820#undef writeback
821#undef lru
822#undef swapbacked
823#undef head
824#undef slab
825#undef reserved
826
827/*
828 * "Dirty/Clean" indication is not 100% accurate due to the possibility of
829 * setting PG_dirty outside page lock. See also comment above set_page_dirty().
830 */
831static void action_result(unsigned long pfn, enum mf_action_page_type type,
832 enum mf_result result)
833{
834 trace_memory_failure_event(pfn, type, result);
835
836 pr_err("MCE %#lx: recovery action for %s: %s\n",
837 pfn, action_page_types[type], action_name[result]);
838}
839
840static int page_action(struct page_state *ps, struct page *p,
841 unsigned long pfn)
842{
843 int result;
844 int count;
845
846 result = ps->action(p, pfn);
847
848 count = page_count(p) - 1;
849 if (ps->action == me_swapcache_dirty && result == MF_DELAYED)
850 count--;
851 if (count != 0) {
852 pr_err("MCE %#lx: %s still referenced by %d users\n",
853 pfn, action_page_types[ps->type], count);
854 result = MF_FAILED;
855 }
856 action_result(pfn, ps->type, result);
857
858 /* Could do more checks here if page looks ok */
859 /*
860 * Could adjust zone counters here to correct for the missing page.
861 */
862
863 return (result == MF_RECOVERED || result == MF_DELAYED) ? 0 : -EBUSY;
864}
865
866/**
867 * get_hwpoison_page() - Get refcount for memory error handling:
868 * @page: raw error page (hit by memory error)
869 *
870 * Return: return 0 if failed to grab the refcount, otherwise true (some
871 * non-zero value.)
872 */
873int get_hwpoison_page(struct page *page)
874{
875 struct page *head = compound_head(page);
876
877 if (!PageHuge(head) && PageTransHuge(head)) {
878 /*
879 * Non anonymous thp exists only in allocation/free time. We
880 * can't handle such a case correctly, so let's give it up.
881 * This should be better than triggering BUG_ON when kernel
882 * tries to touch the "partially handled" page.
883 */
884 if (!PageAnon(head)) {
885 pr_err("MCE: %#lx: non anonymous thp\n",
886 page_to_pfn(page));
887 return 0;
888 }
889 }
890
891 if (get_page_unless_zero(head)) {
892 if (head == compound_head(page))
893 return 1;
894
895 pr_info("MCE: %#lx cannot catch tail\n", page_to_pfn(page));
896 put_page(head);
897 }
898
899 return 0;
900}
901EXPORT_SYMBOL_GPL(get_hwpoison_page);
902
903/*
904 * Do all that is necessary to remove user space mappings. Unmap
905 * the pages and send SIGBUS to the processes if the data was dirty.
906 */
907static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
908 int trapno, int flags, struct page **hpagep)
909{
910 enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
911 struct address_space *mapping;
912 LIST_HEAD(tokill);
913 int ret;
914 int kill = 1, forcekill;
915 struct page *hpage = *hpagep;
916
917 /*
918 * Here we are interested only in user-mapped pages, so skip any
919 * other types of pages.
920 */
921 if (PageReserved(p) || PageSlab(p))
922 return SWAP_SUCCESS;
923 if (!(PageLRU(hpage) || PageHuge(p)))
924 return SWAP_SUCCESS;
925
926 /*
927 * This check implies we don't kill processes if their pages
928 * are in the swap cache early. Those are always late kills.
929 */
930 if (!page_mapped(hpage))
931 return SWAP_SUCCESS;
932
933 if (PageKsm(p)) {
934 pr_err("MCE %#lx: can't handle KSM pages.\n", pfn);
935 return SWAP_FAIL;
936 }
937
938 if (PageSwapCache(p)) {
939 pr_err("MCE %#lx: keeping poisoned page in swap cache\n", pfn);
940 ttu |= TTU_IGNORE_HWPOISON;
941 }
942
943 /*
944 * Propagate the dirty bit from PTEs to struct page first, because we
945 * need this to decide if we should kill or just drop the page.
946 * XXX: the dirty test could be racy: set_page_dirty() may not always
947 * be called inside page lock (it's recommended but not enforced).
948 */
949 mapping = page_mapping(hpage);
950 if (!(flags & MF_MUST_KILL) && !PageDirty(hpage) && mapping &&
951 mapping_cap_writeback_dirty(mapping)) {
952 if (page_mkclean(hpage)) {
953 SetPageDirty(hpage);
954 } else {
955 kill = 0;
956 ttu |= TTU_IGNORE_HWPOISON;
957 pr_info("MCE %#lx: corrupted page was clean: dropped without side effects\n",
958 pfn);
959 }
960 }
961
962 /*
963 * First collect all the processes that have the page
964 * mapped in dirty form. This has to be done before try_to_unmap,
965 * because ttu takes the rmap data structures down.
966 *
967 * Error handling: We ignore errors here because
968 * there's nothing that can be done.
969 */
970 if (kill)
971 collect_procs(hpage, &tokill, flags & MF_ACTION_REQUIRED);
972
973 ret = try_to_unmap(hpage, ttu);
974 if (ret != SWAP_SUCCESS)
975 pr_err("MCE %#lx: failed to unmap page (mapcount=%d)\n",
976 pfn, page_mapcount(hpage));
977
978 /*
979 * Now that the dirty bit has been propagated to the
980 * struct page and all unmaps done we can decide if
981 * killing is needed or not. Only kill when the page
982 * was dirty or the process is not restartable,
983 * otherwise the tokill list is merely
984 * freed. When there was a problem unmapping earlier
985 * use a more force-full uncatchable kill to prevent
986 * any accesses to the poisoned memory.
987 */
988 forcekill = PageDirty(hpage) || (flags & MF_MUST_KILL);
989 kill_procs(&tokill, forcekill, trapno,
990 ret != SWAP_SUCCESS, p, pfn, flags);
991
992 return ret;
993}
994
995static void set_page_hwpoison_huge_page(struct page *hpage)
996{
997 int i;
998 int nr_pages = 1 << compound_order(hpage);
999 for (i = 0; i < nr_pages; i++)
1000 SetPageHWPoison(hpage + i);
1001}
1002
1003static void clear_page_hwpoison_huge_page(struct page *hpage)
1004{
1005 int i;
1006 int nr_pages = 1 << compound_order(hpage);
1007 for (i = 0; i < nr_pages; i++)
1008 ClearPageHWPoison(hpage + i);
1009}
1010
1011/**
1012 * memory_failure - Handle memory failure of a page.
1013 * @pfn: Page Number of the corrupted page
1014 * @trapno: Trap number reported in the signal to user space.
1015 * @flags: fine tune action taken
1016 *
1017 * This function is called by the low level machine check code
1018 * of an architecture when it detects hardware memory corruption
1019 * of a page. It tries its best to recover, which includes
1020 * dropping pages, killing processes etc.
1021 *
1022 * The function is primarily of use for corruptions that
1023 * happen outside the current execution context (e.g. when
1024 * detected by a background scrubber)
1025 *
1026 * Must run in process context (e.g. a work queue) with interrupts
1027 * enabled and no spinlocks hold.
1028 */
1029int memory_failure(unsigned long pfn, int trapno, int flags)
1030{
1031 struct page_state *ps;
1032 struct page *p;
1033 struct page *hpage;
1034 struct page *orig_head;
1035 int res;
1036 unsigned int nr_pages;
1037 unsigned long page_flags;
1038
1039 if (!sysctl_memory_failure_recovery)
1040 panic("Memory failure from trap %d on page %lx", trapno, pfn);
1041
1042 if (!pfn_valid(pfn)) {
1043 pr_err("MCE %#lx: memory outside kernel control\n", pfn);
1044 return -ENXIO;
1045 }
1046
1047 p = pfn_to_page(pfn);
1048 orig_head = hpage = compound_head(p);
1049 if (TestSetPageHWPoison(p)) {
1050 pr_err("MCE %#lx: already hardware poisoned\n", pfn);
1051 return 0;
1052 }
1053
1054 /*
1055 * Currently errors on hugetlbfs pages are measured in hugepage units,
1056 * so nr_pages should be 1 << compound_order. OTOH when errors are on
1057 * transparent hugepages, they are supposed to be split and error
1058 * measurement is done in normal page units. So nr_pages should be one
1059 * in this case.
1060 */
1061 if (PageHuge(p))
1062 nr_pages = 1 << compound_order(hpage);
1063 else /* normal page or thp */
1064 nr_pages = 1;
1065 num_poisoned_pages_add(nr_pages);
1066
1067 /*
1068 * We need/can do nothing about count=0 pages.
1069 * 1) it's a free page, and therefore in safe hand:
1070 * prep_new_page() will be the gate keeper.
1071 * 2) it's a free hugepage, which is also safe:
1072 * an affected hugepage will be dequeued from hugepage freelist,
1073 * so there's no concern about reusing it ever after.
1074 * 3) it's part of a non-compound high order page.
1075 * Implies some kernel user: cannot stop them from
1076 * R/W the page; let's pray that the page has been
1077 * used and will be freed some time later.
1078 * In fact it's dangerous to directly bump up page count from 0,
1079 * that may make page_freeze_refs()/page_unfreeze_refs() mismatch.
1080 */
1081 if (!(flags & MF_COUNT_INCREASED) && !get_hwpoison_page(p)) {
1082 if (is_free_buddy_page(p)) {
1083 action_result(pfn, MF_MSG_BUDDY, MF_DELAYED);
1084 return 0;
1085 } else if (PageHuge(hpage)) {
1086 /*
1087 * Check "filter hit" and "race with other subpage."
1088 */
1089 lock_page(hpage);
1090 if (PageHWPoison(hpage)) {
1091 if ((hwpoison_filter(p) && TestClearPageHWPoison(p))
1092 || (p != hpage && TestSetPageHWPoison(hpage))) {
1093 num_poisoned_pages_sub(nr_pages);
1094 unlock_page(hpage);
1095 return 0;
1096 }
1097 }
1098 set_page_hwpoison_huge_page(hpage);
1099 res = dequeue_hwpoisoned_huge_page(hpage);
1100 action_result(pfn, MF_MSG_FREE_HUGE,
1101 res ? MF_IGNORED : MF_DELAYED);
1102 unlock_page(hpage);
1103 return res;
1104 } else {
1105 action_result(pfn, MF_MSG_KERNEL_HIGH_ORDER, MF_IGNORED);
1106 return -EBUSY;
1107 }
1108 }
1109
1110 if (!PageHuge(p) && PageTransHuge(hpage)) {
1111 lock_page(hpage);
1112 if (!PageAnon(hpage) || unlikely(split_huge_page(hpage))) {
1113 unlock_page(hpage);
1114 if (!PageAnon(hpage))
1115 pr_err("MCE: %#lx: non anonymous thp\n", pfn);
1116 else
1117 pr_err("MCE: %#lx: thp split failed\n", pfn);
1118 if (TestClearPageHWPoison(p))
1119 num_poisoned_pages_sub(nr_pages);
1120 put_hwpoison_page(p);
1121 return -EBUSY;
1122 }
1123 unlock_page(hpage);
1124 get_hwpoison_page(p);
1125 put_hwpoison_page(hpage);
1126 VM_BUG_ON_PAGE(!page_count(p), p);
1127 hpage = compound_head(p);
1128 }
1129
1130 /*
1131 * We ignore non-LRU pages for good reasons.
1132 * - PG_locked is only well defined for LRU pages and a few others
1133 * - to avoid races with __SetPageLocked()
1134 * - to avoid races with __SetPageSlab*() (and more non-atomic ops)
1135 * The check (unnecessarily) ignores LRU pages being isolated and
1136 * walked by the page reclaim code, however that's not a big loss.
1137 */
1138 if (!PageHuge(p)) {
1139 if (!PageLRU(p))
1140 shake_page(p, 0);
1141 if (!PageLRU(p)) {
1142 /*
1143 * shake_page could have turned it free.
1144 */
1145 if (is_free_buddy_page(p)) {
1146 if (flags & MF_COUNT_INCREASED)
1147 action_result(pfn, MF_MSG_BUDDY, MF_DELAYED);
1148 else
1149 action_result(pfn, MF_MSG_BUDDY_2ND,
1150 MF_DELAYED);
1151 return 0;
1152 }
1153 }
1154 }
1155
1156 lock_page(hpage);
1157
1158 /*
1159 * The page could have changed compound pages during the locking.
1160 * If this happens just bail out.
1161 */
1162 if (PageCompound(p) && compound_head(p) != orig_head) {
1163 action_result(pfn, MF_MSG_DIFFERENT_COMPOUND, MF_IGNORED);
1164 res = -EBUSY;
1165 goto out;
1166 }
1167
1168 /*
1169 * We use page flags to determine what action should be taken, but
1170 * the flags can be modified by the error containment action. One
1171 * example is an mlocked page, where PG_mlocked is cleared by
1172 * page_remove_rmap() in try_to_unmap_one(). So to determine page status
1173 * correctly, we save a copy of the page flags at this time.
1174 */
1175 page_flags = p->flags;
1176
1177 /*
1178 * unpoison always clear PG_hwpoison inside page lock
1179 */
1180 if (!PageHWPoison(p)) {
1181 pr_err("MCE %#lx: just unpoisoned\n", pfn);
1182 num_poisoned_pages_sub(nr_pages);
1183 unlock_page(hpage);
1184 put_hwpoison_page(hpage);
1185 return 0;
1186 }
1187 if (hwpoison_filter(p)) {
1188 if (TestClearPageHWPoison(p))
1189 num_poisoned_pages_sub(nr_pages);
1190 unlock_page(hpage);
1191 put_hwpoison_page(hpage);
1192 return 0;
1193 }
1194
1195 if (!PageHuge(p) && !PageTransTail(p) && !PageLRU(p))
1196 goto identify_page_state;
1197
1198 /*
1199 * For error on the tail page, we should set PG_hwpoison
1200 * on the head page to show that the hugepage is hwpoisoned
1201 */
1202 if (PageHuge(p) && PageTail(p) && TestSetPageHWPoison(hpage)) {
1203 action_result(pfn, MF_MSG_POISONED_HUGE, MF_IGNORED);
1204 unlock_page(hpage);
1205 put_hwpoison_page(hpage);
1206 return 0;
1207 }
1208 /*
1209 * Set PG_hwpoison on all pages in an error hugepage,
1210 * because containment is done in hugepage unit for now.
1211 * Since we have done TestSetPageHWPoison() for the head page with
1212 * page lock held, we can safely set PG_hwpoison bits on tail pages.
1213 */
1214 if (PageHuge(p))
1215 set_page_hwpoison_huge_page(hpage);
1216
1217 /*
1218 * It's very difficult to mess with pages currently under IO
1219 * and in many cases impossible, so we just avoid it here.
1220 */
1221 wait_on_page_writeback(p);
1222
1223 /*
1224 * Now take care of user space mappings.
1225 * Abort on fail: __delete_from_page_cache() assumes unmapped page.
1226 *
1227 * When the raw error page is thp tail page, hpage points to the raw
1228 * page after thp split.
1229 */
1230 if (hwpoison_user_mappings(p, pfn, trapno, flags, &hpage)
1231 != SWAP_SUCCESS) {
1232 action_result(pfn, MF_MSG_UNMAP_FAILED, MF_IGNORED);
1233 res = -EBUSY;
1234 goto out;
1235 }
1236
1237 /*
1238 * Torn down by someone else?
1239 */
1240 if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) {
1241 action_result(pfn, MF_MSG_TRUNCATED_LRU, MF_IGNORED);
1242 res = -EBUSY;
1243 goto out;
1244 }
1245
1246identify_page_state:
1247 res = -EBUSY;
1248 /*
1249 * The first check uses the current page flags which may not have any
1250 * relevant information. The second check with the saved page flagss is
1251 * carried out only if the first check can't determine the page status.
1252 */
1253 for (ps = error_states;; ps++)
1254 if ((p->flags & ps->mask) == ps->res)
1255 break;
1256
1257 page_flags |= (p->flags & (1UL << PG_dirty));
1258
1259 if (!ps->mask)
1260 for (ps = error_states;; ps++)
1261 if ((page_flags & ps->mask) == ps->res)
1262 break;
1263 res = page_action(ps, p, pfn);
1264out:
1265 unlock_page(hpage);
1266 return res;
1267}
1268EXPORT_SYMBOL_GPL(memory_failure);
1269
1270#define MEMORY_FAILURE_FIFO_ORDER 4
1271#define MEMORY_FAILURE_FIFO_SIZE (1 << MEMORY_FAILURE_FIFO_ORDER)
1272
1273struct memory_failure_entry {
1274 unsigned long pfn;
1275 int trapno;
1276 int flags;
1277};
1278
1279struct memory_failure_cpu {
1280 DECLARE_KFIFO(fifo, struct memory_failure_entry,
1281 MEMORY_FAILURE_FIFO_SIZE);
1282 spinlock_t lock;
1283 struct work_struct work;
1284};
1285
1286static DEFINE_PER_CPU(struct memory_failure_cpu, memory_failure_cpu);
1287
1288/**
1289 * memory_failure_queue - Schedule handling memory failure of a page.
1290 * @pfn: Page Number of the corrupted page
1291 * @trapno: Trap number reported in the signal to user space.
1292 * @flags: Flags for memory failure handling
1293 *
1294 * This function is called by the low level hardware error handler
1295 * when it detects hardware memory corruption of a page. It schedules
1296 * the recovering of error page, including dropping pages, killing
1297 * processes etc.
1298 *
1299 * The function is primarily of use for corruptions that
1300 * happen outside the current execution context (e.g. when
1301 * detected by a background scrubber)
1302 *
1303 * Can run in IRQ context.
1304 */
1305void memory_failure_queue(unsigned long pfn, int trapno, int flags)
1306{
1307 struct memory_failure_cpu *mf_cpu;
1308 unsigned long proc_flags;
1309 struct memory_failure_entry entry = {
1310 .pfn = pfn,
1311 .trapno = trapno,
1312 .flags = flags,
1313 };
1314
1315 mf_cpu = &get_cpu_var(memory_failure_cpu);
1316 spin_lock_irqsave(&mf_cpu->lock, proc_flags);
1317 if (kfifo_put(&mf_cpu->fifo, entry))
1318 schedule_work_on(smp_processor_id(), &mf_cpu->work);
1319 else
1320 pr_err("Memory failure: buffer overflow when queuing memory failure at %#lx\n",
1321 pfn);
1322 spin_unlock_irqrestore(&mf_cpu->lock, proc_flags);
1323 put_cpu_var(memory_failure_cpu);
1324}
1325EXPORT_SYMBOL_GPL(memory_failure_queue);
1326
1327static void memory_failure_work_func(struct work_struct *work)
1328{
1329 struct memory_failure_cpu *mf_cpu;
1330 struct memory_failure_entry entry = { 0, };
1331 unsigned long proc_flags;
1332 int gotten;
1333
1334 mf_cpu = this_cpu_ptr(&memory_failure_cpu);
1335 for (;;) {
1336 spin_lock_irqsave(&mf_cpu->lock, proc_flags);
1337 gotten = kfifo_get(&mf_cpu->fifo, &entry);
1338 spin_unlock_irqrestore(&mf_cpu->lock, proc_flags);
1339 if (!gotten)
1340 break;
1341 if (entry.flags & MF_SOFT_OFFLINE)
1342 soft_offline_page(pfn_to_page(entry.pfn), entry.flags);
1343 else
1344 memory_failure(entry.pfn, entry.trapno, entry.flags);
1345 }
1346}
1347
1348static int __init memory_failure_init(void)
1349{
1350 struct memory_failure_cpu *mf_cpu;
1351 int cpu;
1352
1353 for_each_possible_cpu(cpu) {
1354 mf_cpu = &per_cpu(memory_failure_cpu, cpu);
1355 spin_lock_init(&mf_cpu->lock);
1356 INIT_KFIFO(mf_cpu->fifo);
1357 INIT_WORK(&mf_cpu->work, memory_failure_work_func);
1358 }
1359
1360 return 0;
1361}
1362core_initcall(memory_failure_init);
1363
1364#define unpoison_pr_info(fmt, pfn, rs) \
1365({ \
1366 if (__ratelimit(rs)) \
1367 pr_info(fmt, pfn); \
1368})
1369
1370/**
1371 * unpoison_memory - Unpoison a previously poisoned page
1372 * @pfn: Page number of the to be unpoisoned page
1373 *
1374 * Software-unpoison a page that has been poisoned by
1375 * memory_failure() earlier.
1376 *
1377 * This is only done on the software-level, so it only works
1378 * for linux injected failures, not real hardware failures
1379 *
1380 * Returns 0 for success, otherwise -errno.
1381 */
1382int unpoison_memory(unsigned long pfn)
1383{
1384 struct page *page;
1385 struct page *p;
1386 int freeit = 0;
1387 unsigned int nr_pages;
1388 static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL,
1389 DEFAULT_RATELIMIT_BURST);
1390
1391 if (!pfn_valid(pfn))
1392 return -ENXIO;
1393
1394 p = pfn_to_page(pfn);
1395 page = compound_head(p);
1396
1397 if (!PageHWPoison(p)) {
1398 unpoison_pr_info("MCE: Page was already unpoisoned %#lx\n",
1399 pfn, &unpoison_rs);
1400 return 0;
1401 }
1402
1403 if (page_count(page) > 1) {
1404 unpoison_pr_info("MCE: Someone grabs the hwpoison page %#lx\n",
1405 pfn, &unpoison_rs);
1406 return 0;
1407 }
1408
1409 if (page_mapped(page)) {
1410 unpoison_pr_info("MCE: Someone maps the hwpoison page %#lx\n",
1411 pfn, &unpoison_rs);
1412 return 0;
1413 }
1414
1415 if (page_mapping(page)) {
1416 unpoison_pr_info("MCE: the hwpoison page has non-NULL mapping %#lx\n",
1417 pfn, &unpoison_rs);
1418 return 0;
1419 }
1420
1421 /*
1422 * unpoison_memory() can encounter thp only when the thp is being
1423 * worked by memory_failure() and the page lock is not held yet.
1424 * In such case, we yield to memory_failure() and make unpoison fail.
1425 */
1426 if (!PageHuge(page) && PageTransHuge(page)) {
1427 unpoison_pr_info("MCE: Memory failure is now running on %#lx\n",
1428 pfn, &unpoison_rs);
1429 return 0;
1430 }
1431
1432 nr_pages = 1 << compound_order(page);
1433
1434 if (!get_hwpoison_page(p)) {
1435 /*
1436 * Since HWPoisoned hugepage should have non-zero refcount,
1437 * race between memory failure and unpoison seems to happen.
1438 * In such case unpoison fails and memory failure runs
1439 * to the end.
1440 */
1441 if (PageHuge(page)) {
1442 unpoison_pr_info("MCE: Memory failure is now running on free hugepage %#lx\n",
1443 pfn, &unpoison_rs);
1444 return 0;
1445 }
1446 if (TestClearPageHWPoison(p))
1447 num_poisoned_pages_dec();
1448 unpoison_pr_info("MCE: Software-unpoisoned free page %#lx\n",
1449 pfn, &unpoison_rs);
1450 return 0;
1451 }
1452
1453 lock_page(page);
1454 /*
1455 * This test is racy because PG_hwpoison is set outside of page lock.
1456 * That's acceptable because that won't trigger kernel panic. Instead,
1457 * the PG_hwpoison page will be caught and isolated on the entrance to
1458 * the free buddy page pool.
1459 */
1460 if (TestClearPageHWPoison(page)) {
1461 unpoison_pr_info("MCE: Software-unpoisoned page %#lx\n",
1462 pfn, &unpoison_rs);
1463 num_poisoned_pages_sub(nr_pages);
1464 freeit = 1;
1465 if (PageHuge(page))
1466 clear_page_hwpoison_huge_page(page);
1467 }
1468 unlock_page(page);
1469
1470 put_hwpoison_page(page);
1471 if (freeit && !(pfn == my_zero_pfn(0) && page_count(p) == 1))
1472 put_hwpoison_page(page);
1473
1474 return 0;
1475}
1476EXPORT_SYMBOL(unpoison_memory);
1477
1478static struct page *new_page(struct page *p, unsigned long private, int **x)
1479{
1480 int nid = page_to_nid(p);
1481 if (PageHuge(p))
1482 return alloc_huge_page_node(page_hstate(compound_head(p)),
1483 nid);
1484 else
1485 return __alloc_pages_node(nid, GFP_HIGHUSER_MOVABLE, 0);
1486}
1487
1488/*
1489 * Safely get reference count of an arbitrary page.
1490 * Returns 0 for a free page, -EIO for a zero refcount page
1491 * that is not free, and 1 for any other page type.
1492 * For 1 the page is returned with increased page count, otherwise not.
1493 */
1494static int __get_any_page(struct page *p, unsigned long pfn, int flags)
1495{
1496 int ret;
1497
1498 if (flags & MF_COUNT_INCREASED)
1499 return 1;
1500
1501 /*
1502 * When the target page is a free hugepage, just remove it
1503 * from free hugepage list.
1504 */
1505 if (!get_hwpoison_page(p)) {
1506 if (PageHuge(p)) {
1507 pr_info("%s: %#lx free huge page\n", __func__, pfn);
1508 ret = 0;
1509 } else if (is_free_buddy_page(p)) {
1510 pr_info("%s: %#lx free buddy page\n", __func__, pfn);
1511 ret = 0;
1512 } else {
1513 pr_info("%s: %#lx: unknown zero refcount page type %lx\n",
1514 __func__, pfn, p->flags);
1515 ret = -EIO;
1516 }
1517 } else {
1518 /* Not a free page */
1519 ret = 1;
1520 }
1521 return ret;
1522}
1523
1524static int get_any_page(struct page *page, unsigned long pfn, int flags)
1525{
1526 int ret = __get_any_page(page, pfn, flags);
1527
1528 if (ret == 1 && !PageHuge(page) && !PageLRU(page)) {
1529 /*
1530 * Try to free it.
1531 */
1532 put_hwpoison_page(page);
1533 shake_page(page, 1);
1534
1535 /*
1536 * Did it turn free?
1537 */
1538 ret = __get_any_page(page, pfn, 0);
1539 if (ret == 1 && !PageLRU(page)) {
1540 /* Drop page reference which is from __get_any_page() */
1541 put_hwpoison_page(page);
1542 pr_info("soft_offline: %#lx: unknown non LRU page type %lx\n",
1543 pfn, page->flags);
1544 return -EIO;
1545 }
1546 }
1547 return ret;
1548}
1549
1550static int soft_offline_huge_page(struct page *page, int flags)
1551{
1552 int ret;
1553 unsigned long pfn = page_to_pfn(page);
1554 struct page *hpage = compound_head(page);
1555 LIST_HEAD(pagelist);
1556
1557 /*
1558 * This double-check of PageHWPoison is to avoid the race with
1559 * memory_failure(). See also comment in __soft_offline_page().
1560 */
1561 lock_page(hpage);
1562 if (PageHWPoison(hpage)) {
1563 unlock_page(hpage);
1564 put_hwpoison_page(hpage);
1565 pr_info("soft offline: %#lx hugepage already poisoned\n", pfn);
1566 return -EBUSY;
1567 }
1568 unlock_page(hpage);
1569
1570 ret = isolate_huge_page(hpage, &pagelist);
1571 /*
1572 * get_any_page() and isolate_huge_page() takes a refcount each,
1573 * so need to drop one here.
1574 */
1575 put_hwpoison_page(hpage);
1576 if (!ret) {
1577 pr_info("soft offline: %#lx hugepage failed to isolate\n", pfn);
1578 return -EBUSY;
1579 }
1580
1581 ret = migrate_pages(&pagelist, new_page, NULL, MPOL_MF_MOVE_ALL,
1582 MIGRATE_SYNC, MR_MEMORY_FAILURE);
1583 if (ret) {
1584 pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
1585 pfn, ret, page->flags);
1586 /*
1587 * We know that soft_offline_huge_page() tries to migrate
1588 * only one hugepage pointed to by hpage, so we need not
1589 * run through the pagelist here.
1590 */
1591 putback_active_hugepage(hpage);
1592 if (ret > 0)
1593 ret = -EIO;
1594 } else {
1595 /* overcommit hugetlb page will be freed to buddy */
1596 if (PageHuge(page)) {
1597 set_page_hwpoison_huge_page(hpage);
1598 dequeue_hwpoisoned_huge_page(hpage);
1599 num_poisoned_pages_add(1 << compound_order(hpage));
1600 } else {
1601 SetPageHWPoison(page);
1602 num_poisoned_pages_inc();
1603 }
1604 }
1605 return ret;
1606}
1607
1608static int __soft_offline_page(struct page *page, int flags)
1609{
1610 int ret;
1611 unsigned long pfn = page_to_pfn(page);
1612
1613 /*
1614 * Check PageHWPoison again inside page lock because PageHWPoison
1615 * is set by memory_failure() outside page lock. Note that
1616 * memory_failure() also double-checks PageHWPoison inside page lock,
1617 * so there's no race between soft_offline_page() and memory_failure().
1618 */
1619 lock_page(page);
1620 wait_on_page_writeback(page);
1621 if (PageHWPoison(page)) {
1622 unlock_page(page);
1623 put_hwpoison_page(page);
1624 pr_info("soft offline: %#lx page already poisoned\n", pfn);
1625 return -EBUSY;
1626 }
1627 /*
1628 * Try to invalidate first. This should work for
1629 * non dirty unmapped page cache pages.
1630 */
1631 ret = invalidate_inode_page(page);
1632 unlock_page(page);
1633 /*
1634 * RED-PEN would be better to keep it isolated here, but we
1635 * would need to fix isolation locking first.
1636 */
1637 if (ret == 1) {
1638 put_hwpoison_page(page);
1639 pr_info("soft_offline: %#lx: invalidated\n", pfn);
1640 SetPageHWPoison(page);
1641 num_poisoned_pages_inc();
1642 return 0;
1643 }
1644
1645 /*
1646 * Simple invalidation didn't work.
1647 * Try to migrate to a new page instead. migrate.c
1648 * handles a large number of cases for us.
1649 */
1650 ret = isolate_lru_page(page);
1651 /*
1652 * Drop page reference which is came from get_any_page()
1653 * successful isolate_lru_page() already took another one.
1654 */
1655 put_hwpoison_page(page);
1656 if (!ret) {
1657 LIST_HEAD(pagelist);
1658 inc_zone_page_state(page, NR_ISOLATED_ANON +
1659 page_is_file_cache(page));
1660 list_add(&page->lru, &pagelist);
1661 ret = migrate_pages(&pagelist, new_page, NULL, MPOL_MF_MOVE_ALL,
1662 MIGRATE_SYNC, MR_MEMORY_FAILURE);
1663 if (ret) {
1664 if (!list_empty(&pagelist)) {
1665 list_del(&page->lru);
1666 dec_zone_page_state(page, NR_ISOLATED_ANON +
1667 page_is_file_cache(page));
1668 putback_lru_page(page);
1669 }
1670
1671 pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
1672 pfn, ret, page->flags);
1673 if (ret > 0)
1674 ret = -EIO;
1675 }
1676 } else {
1677 pr_info("soft offline: %#lx: isolation failed: %d, page count %d, type %lx\n",
1678 pfn, ret, page_count(page), page->flags);
1679 }
1680 return ret;
1681}
1682
1683static int soft_offline_in_use_page(struct page *page, int flags)
1684{
1685 int ret;
1686 struct page *hpage = compound_head(page);
1687
1688 if (!PageHuge(page) && PageTransHuge(hpage)) {
1689 lock_page(hpage);
1690 if (!PageAnon(hpage) || unlikely(split_huge_page(hpage))) {
1691 unlock_page(hpage);
1692 if (!PageAnon(hpage))
1693 pr_info("soft offline: %#lx: non anonymous thp\n", page_to_pfn(page));
1694 else
1695 pr_info("soft offline: %#lx: thp split failed\n", page_to_pfn(page));
1696 put_hwpoison_page(hpage);
1697 return -EBUSY;
1698 }
1699 unlock_page(hpage);
1700 get_hwpoison_page(page);
1701 put_hwpoison_page(hpage);
1702 }
1703
1704 if (PageHuge(page))
1705 ret = soft_offline_huge_page(page, flags);
1706 else
1707 ret = __soft_offline_page(page, flags);
1708
1709 return ret;
1710}
1711
1712static void soft_offline_free_page(struct page *page)
1713{
1714 if (PageHuge(page)) {
1715 struct page *hpage = compound_head(page);
1716
1717 set_page_hwpoison_huge_page(hpage);
1718 if (!dequeue_hwpoisoned_huge_page(hpage))
1719 num_poisoned_pages_add(1 << compound_order(hpage));
1720 } else {
1721 if (!TestSetPageHWPoison(page))
1722 num_poisoned_pages_inc();
1723 }
1724}
1725
1726/**
1727 * soft_offline_page - Soft offline a page.
1728 * @page: page to offline
1729 * @flags: flags. Same as memory_failure().
1730 *
1731 * Returns 0 on success, otherwise negated errno.
1732 *
1733 * Soft offline a page, by migration or invalidation,
1734 * without killing anything. This is for the case when
1735 * a page is not corrupted yet (so it's still valid to access),
1736 * but has had a number of corrected errors and is better taken
1737 * out.
1738 *
1739 * The actual policy on when to do that is maintained by
1740 * user space.
1741 *
1742 * This should never impact any application or cause data loss,
1743 * however it might take some time.
1744 *
1745 * This is not a 100% solution for all memory, but tries to be
1746 * ``good enough'' for the majority of memory.
1747 */
1748int soft_offline_page(struct page *page, int flags)
1749{
1750 int ret;
1751 unsigned long pfn = page_to_pfn(page);
1752
1753 if (PageHWPoison(page)) {
1754 pr_info("soft offline: %#lx page already poisoned\n", pfn);
1755 if (flags & MF_COUNT_INCREASED)
1756 put_hwpoison_page(page);
1757 return -EBUSY;
1758 }
1759
1760 get_online_mems();
1761 ret = get_any_page(page, pfn, flags);
1762 put_online_mems();
1763
1764 if (ret > 0)
1765 ret = soft_offline_in_use_page(page, flags);
1766 else if (ret == 0)
1767 soft_offline_free_page(page);
1768
1769 return ret;
1770}
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 multi-bit ECC memory or cache
11 * failure.
12 *
13 * In addition there is a "soft offline" entry point that allows stop using
14 * not-yet-corrupted-by-suspicious pages without killing anything.
15 *
16 * Handles page cache pages in various states. The tricky part
17 * here is that we can access any page asynchronously in respect to
18 * other VM users, because memory failures could happen anytime and
19 * anywhere. This could violate some of their assumptions. This is why
20 * this code has to be extremely careful. Generally it tries to use
21 * normal locking rules, as in get the standard locks, even if that means
22 * the error handling takes potentially a long time.
23 *
24 * There are several operations here with exponential complexity because
25 * of unsuitable VM data structures. For example the operation to map back
26 * from RMAP chains to processes has to walk the complete process list and
27 * has non linear complexity with the number. But since memory corruptions
28 * are rare we hope to get away with this. This avoids impacting the core
29 * VM.
30 */
31
32/*
33 * Notebook:
34 * - hugetlb needs more code
35 * - kcore/oldmem/vmcore/mem/kmem check for hwpoison pages
36 * - pass bad pages to kdump next kernel
37 */
38#include <linux/kernel.h>
39#include <linux/mm.h>
40#include <linux/page-flags.h>
41#include <linux/kernel-page-flags.h>
42#include <linux/sched.h>
43#include <linux/ksm.h>
44#include <linux/rmap.h>
45#include <linux/export.h>
46#include <linux/pagemap.h>
47#include <linux/swap.h>
48#include <linux/backing-dev.h>
49#include <linux/migrate.h>
50#include <linux/page-isolation.h>
51#include <linux/suspend.h>
52#include <linux/slab.h>
53#include <linux/swapops.h>
54#include <linux/hugetlb.h>
55#include <linux/memory_hotplug.h>
56#include <linux/mm_inline.h>
57#include <linux/kfifo.h>
58#include "internal.h"
59
60int sysctl_memory_failure_early_kill __read_mostly = 0;
61
62int sysctl_memory_failure_recovery __read_mostly = 1;
63
64atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0);
65
66#if defined(CONFIG_HWPOISON_INJECT) || defined(CONFIG_HWPOISON_INJECT_MODULE)
67
68u32 hwpoison_filter_enable = 0;
69u32 hwpoison_filter_dev_major = ~0U;
70u32 hwpoison_filter_dev_minor = ~0U;
71u64 hwpoison_filter_flags_mask;
72u64 hwpoison_filter_flags_value;
73EXPORT_SYMBOL_GPL(hwpoison_filter_enable);
74EXPORT_SYMBOL_GPL(hwpoison_filter_dev_major);
75EXPORT_SYMBOL_GPL(hwpoison_filter_dev_minor);
76EXPORT_SYMBOL_GPL(hwpoison_filter_flags_mask);
77EXPORT_SYMBOL_GPL(hwpoison_filter_flags_value);
78
79static int hwpoison_filter_dev(struct page *p)
80{
81 struct address_space *mapping;
82 dev_t dev;
83
84 if (hwpoison_filter_dev_major == ~0U &&
85 hwpoison_filter_dev_minor == ~0U)
86 return 0;
87
88 /*
89 * page_mapping() does not accept slab pages.
90 */
91 if (PageSlab(p))
92 return -EINVAL;
93
94 mapping = page_mapping(p);
95 if (mapping == NULL || mapping->host == NULL)
96 return -EINVAL;
97
98 dev = mapping->host->i_sb->s_dev;
99 if (hwpoison_filter_dev_major != ~0U &&
100 hwpoison_filter_dev_major != MAJOR(dev))
101 return -EINVAL;
102 if (hwpoison_filter_dev_minor != ~0U &&
103 hwpoison_filter_dev_minor != MINOR(dev))
104 return -EINVAL;
105
106 return 0;
107}
108
109static int hwpoison_filter_flags(struct page *p)
110{
111 if (!hwpoison_filter_flags_mask)
112 return 0;
113
114 if ((stable_page_flags(p) & hwpoison_filter_flags_mask) ==
115 hwpoison_filter_flags_value)
116 return 0;
117 else
118 return -EINVAL;
119}
120
121/*
122 * This allows stress tests to limit test scope to a collection of tasks
123 * by putting them under some memcg. This prevents killing unrelated/important
124 * processes such as /sbin/init. Note that the target task may share clean
125 * pages with init (eg. libc text), which is harmless. If the target task
126 * share _dirty_ pages with another task B, the test scheme must make sure B
127 * is also included in the memcg. At last, due to race conditions this filter
128 * can only guarantee that the page either belongs to the memcg tasks, or is
129 * a freed page.
130 */
131#ifdef CONFIG_MEMCG_SWAP
132u64 hwpoison_filter_memcg;
133EXPORT_SYMBOL_GPL(hwpoison_filter_memcg);
134static int hwpoison_filter_task(struct page *p)
135{
136 struct mem_cgroup *mem;
137 struct cgroup_subsys_state *css;
138 unsigned long ino;
139
140 if (!hwpoison_filter_memcg)
141 return 0;
142
143 mem = try_get_mem_cgroup_from_page(p);
144 if (!mem)
145 return -EINVAL;
146
147 css = mem_cgroup_css(mem);
148 ino = cgroup_ino(css->cgroup);
149 css_put(css);
150
151 if (!ino || ino != hwpoison_filter_memcg)
152 return -EINVAL;
153
154 return 0;
155}
156#else
157static int hwpoison_filter_task(struct page *p) { return 0; }
158#endif
159
160int hwpoison_filter(struct page *p)
161{
162 if (!hwpoison_filter_enable)
163 return 0;
164
165 if (hwpoison_filter_dev(p))
166 return -EINVAL;
167
168 if (hwpoison_filter_flags(p))
169 return -EINVAL;
170
171 if (hwpoison_filter_task(p))
172 return -EINVAL;
173
174 return 0;
175}
176#else
177int hwpoison_filter(struct page *p)
178{
179 return 0;
180}
181#endif
182
183EXPORT_SYMBOL_GPL(hwpoison_filter);
184
185/*
186 * Send all the processes who have the page mapped a signal.
187 * ``action optional'' if they are not immediately affected by the error
188 * ``action required'' if error happened in current execution context
189 */
190static int kill_proc(struct task_struct *t, unsigned long addr, int trapno,
191 unsigned long pfn, struct page *page, int flags)
192{
193 struct siginfo si;
194 int ret;
195
196 printk(KERN_ERR
197 "MCE %#lx: Killing %s:%d due to hardware memory corruption\n",
198 pfn, t->comm, t->pid);
199 si.si_signo = SIGBUS;
200 si.si_errno = 0;
201 si.si_addr = (void *)addr;
202#ifdef __ARCH_SI_TRAPNO
203 si.si_trapno = trapno;
204#endif
205 si.si_addr_lsb = compound_order(compound_head(page)) + PAGE_SHIFT;
206
207 if ((flags & MF_ACTION_REQUIRED) && t == current) {
208 si.si_code = BUS_MCEERR_AR;
209 ret = force_sig_info(SIGBUS, &si, t);
210 } else {
211 /*
212 * Don't use force here, it's convenient if the signal
213 * can be temporarily blocked.
214 * This could cause a loop when the user sets SIGBUS
215 * to SIG_IGN, but hopefully no one will do that?
216 */
217 si.si_code = BUS_MCEERR_AO;
218 ret = send_sig_info(SIGBUS, &si, t); /* synchronous? */
219 }
220 if (ret < 0)
221 printk(KERN_INFO "MCE: Error sending signal to %s:%d: %d\n",
222 t->comm, t->pid, ret);
223 return ret;
224}
225
226/*
227 * When a unknown page type is encountered drain as many buffers as possible
228 * in the hope to turn the page into a LRU or free page, which we can handle.
229 */
230void shake_page(struct page *p, int access)
231{
232 if (!PageSlab(p)) {
233 lru_add_drain_all();
234 if (PageLRU(p))
235 return;
236 drain_all_pages();
237 if (PageLRU(p) || is_free_buddy_page(p))
238 return;
239 }
240
241 /*
242 * Only call shrink_slab here (which would also shrink other caches) if
243 * access is not potentially fatal.
244 */
245 if (access) {
246 int nr;
247 int nid = page_to_nid(p);
248 do {
249 struct shrink_control shrink = {
250 .gfp_mask = GFP_KERNEL,
251 };
252 node_set(nid, shrink.nodes_to_scan);
253
254 nr = shrink_slab(&shrink, 1000, 1000);
255 if (page_count(p) == 1)
256 break;
257 } while (nr > 10);
258 }
259}
260EXPORT_SYMBOL_GPL(shake_page);
261
262/*
263 * Kill all processes that have a poisoned page mapped and then isolate
264 * the page.
265 *
266 * General strategy:
267 * Find all processes having the page mapped and kill them.
268 * But we keep a page reference around so that the page is not
269 * actually freed yet.
270 * Then stash the page away
271 *
272 * There's no convenient way to get back to mapped processes
273 * from the VMAs. So do a brute-force search over all
274 * running processes.
275 *
276 * Remember that machine checks are not common (or rather
277 * if they are common you have other problems), so this shouldn't
278 * be a performance issue.
279 *
280 * Also there are some races possible while we get from the
281 * error detection to actually handle it.
282 */
283
284struct to_kill {
285 struct list_head nd;
286 struct task_struct *tsk;
287 unsigned long addr;
288 char addr_valid;
289};
290
291/*
292 * Failure handling: if we can't find or can't kill a process there's
293 * not much we can do. We just print a message and ignore otherwise.
294 */
295
296/*
297 * Schedule a process for later kill.
298 * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
299 * TBD would GFP_NOIO be enough?
300 */
301static void add_to_kill(struct task_struct *tsk, struct page *p,
302 struct vm_area_struct *vma,
303 struct list_head *to_kill,
304 struct to_kill **tkc)
305{
306 struct to_kill *tk;
307
308 if (*tkc) {
309 tk = *tkc;
310 *tkc = NULL;
311 } else {
312 tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
313 if (!tk) {
314 printk(KERN_ERR
315 "MCE: Out of memory while machine check handling\n");
316 return;
317 }
318 }
319 tk->addr = page_address_in_vma(p, vma);
320 tk->addr_valid = 1;
321
322 /*
323 * In theory we don't have to kill when the page was
324 * munmaped. But it could be also a mremap. Since that's
325 * likely very rare kill anyways just out of paranoia, but use
326 * a SIGKILL because the error is not contained anymore.
327 */
328 if (tk->addr == -EFAULT) {
329 pr_info("MCE: Unable to find user space address %lx in %s\n",
330 page_to_pfn(p), tsk->comm);
331 tk->addr_valid = 0;
332 }
333 get_task_struct(tsk);
334 tk->tsk = tsk;
335 list_add_tail(&tk->nd, to_kill);
336}
337
338/*
339 * Kill the processes that have been collected earlier.
340 *
341 * Only do anything when DOIT is set, otherwise just free the list
342 * (this is used for clean pages which do not need killing)
343 * Also when FAIL is set do a force kill because something went
344 * wrong earlier.
345 */
346static void kill_procs(struct list_head *to_kill, int forcekill, int trapno,
347 int fail, struct page *page, unsigned long pfn,
348 int flags)
349{
350 struct to_kill *tk, *next;
351
352 list_for_each_entry_safe (tk, next, to_kill, nd) {
353 if (forcekill) {
354 /*
355 * In case something went wrong with munmapping
356 * make sure the process doesn't catch the
357 * signal and then access the memory. Just kill it.
358 */
359 if (fail || tk->addr_valid == 0) {
360 printk(KERN_ERR
361 "MCE %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n",
362 pfn, tk->tsk->comm, tk->tsk->pid);
363 force_sig(SIGKILL, tk->tsk);
364 }
365
366 /*
367 * In theory the process could have mapped
368 * something else on the address in-between. We could
369 * check for that, but we need to tell the
370 * process anyways.
371 */
372 else if (kill_proc(tk->tsk, tk->addr, trapno,
373 pfn, page, flags) < 0)
374 printk(KERN_ERR
375 "MCE %#lx: Cannot send advisory machine check signal to %s:%d\n",
376 pfn, tk->tsk->comm, tk->tsk->pid);
377 }
378 put_task_struct(tk->tsk);
379 kfree(tk);
380 }
381}
382
383static int task_early_kill(struct task_struct *tsk)
384{
385 if (!tsk->mm)
386 return 0;
387 if (tsk->flags & PF_MCE_PROCESS)
388 return !!(tsk->flags & PF_MCE_EARLY);
389 return sysctl_memory_failure_early_kill;
390}
391
392/*
393 * Collect processes when the error hit an anonymous page.
394 */
395static void collect_procs_anon(struct page *page, struct list_head *to_kill,
396 struct to_kill **tkc)
397{
398 struct vm_area_struct *vma;
399 struct task_struct *tsk;
400 struct anon_vma *av;
401 pgoff_t pgoff;
402
403 av = page_lock_anon_vma_read(page);
404 if (av == NULL) /* Not actually mapped anymore */
405 return;
406
407 pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
408 read_lock(&tasklist_lock);
409 for_each_process (tsk) {
410 struct anon_vma_chain *vmac;
411
412 if (!task_early_kill(tsk))
413 continue;
414 anon_vma_interval_tree_foreach(vmac, &av->rb_root,
415 pgoff, pgoff) {
416 vma = vmac->vma;
417 if (!page_mapped_in_vma(page, vma))
418 continue;
419 if (vma->vm_mm == tsk->mm)
420 add_to_kill(tsk, page, vma, to_kill, tkc);
421 }
422 }
423 read_unlock(&tasklist_lock);
424 page_unlock_anon_vma_read(av);
425}
426
427/*
428 * Collect processes when the error hit a file mapped page.
429 */
430static void collect_procs_file(struct page *page, struct list_head *to_kill,
431 struct to_kill **tkc)
432{
433 struct vm_area_struct *vma;
434 struct task_struct *tsk;
435 struct address_space *mapping = page->mapping;
436
437 mutex_lock(&mapping->i_mmap_mutex);
438 read_lock(&tasklist_lock);
439 for_each_process(tsk) {
440 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
441
442 if (!task_early_kill(tsk))
443 continue;
444
445 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff,
446 pgoff) {
447 /*
448 * Send early kill signal to tasks where a vma covers
449 * the page but the corrupted page is not necessarily
450 * mapped it in its pte.
451 * Assume applications who requested early kill want
452 * to be informed of all such data corruptions.
453 */
454 if (vma->vm_mm == tsk->mm)
455 add_to_kill(tsk, page, vma, to_kill, tkc);
456 }
457 }
458 read_unlock(&tasklist_lock);
459 mutex_unlock(&mapping->i_mmap_mutex);
460}
461
462/*
463 * Collect the processes who have the corrupted page mapped to kill.
464 * This is done in two steps for locking reasons.
465 * First preallocate one tokill structure outside the spin locks,
466 * so that we can kill at least one process reasonably reliable.
467 */
468static void collect_procs(struct page *page, struct list_head *tokill)
469{
470 struct to_kill *tk;
471
472 if (!page->mapping)
473 return;
474
475 tk = kmalloc(sizeof(struct to_kill), GFP_NOIO);
476 if (!tk)
477 return;
478 if (PageAnon(page))
479 collect_procs_anon(page, tokill, &tk);
480 else
481 collect_procs_file(page, tokill, &tk);
482 kfree(tk);
483}
484
485/*
486 * Error handlers for various types of pages.
487 */
488
489enum outcome {
490 IGNORED, /* Error: cannot be handled */
491 FAILED, /* Error: handling failed */
492 DELAYED, /* Will be handled later */
493 RECOVERED, /* Successfully recovered */
494};
495
496static const char *action_name[] = {
497 [IGNORED] = "Ignored",
498 [FAILED] = "Failed",
499 [DELAYED] = "Delayed",
500 [RECOVERED] = "Recovered",
501};
502
503/*
504 * XXX: It is possible that a page is isolated from LRU cache,
505 * and then kept in swap cache or failed to remove from page cache.
506 * The page count will stop it from being freed by unpoison.
507 * Stress tests should be aware of this memory leak problem.
508 */
509static int delete_from_lru_cache(struct page *p)
510{
511 if (!isolate_lru_page(p)) {
512 /*
513 * Clear sensible page flags, so that the buddy system won't
514 * complain when the page is unpoison-and-freed.
515 */
516 ClearPageActive(p);
517 ClearPageUnevictable(p);
518 /*
519 * drop the page count elevated by isolate_lru_page()
520 */
521 page_cache_release(p);
522 return 0;
523 }
524 return -EIO;
525}
526
527/*
528 * Error hit kernel page.
529 * Do nothing, try to be lucky and not touch this instead. For a few cases we
530 * could be more sophisticated.
531 */
532static int me_kernel(struct page *p, unsigned long pfn)
533{
534 return IGNORED;
535}
536
537/*
538 * Page in unknown state. Do nothing.
539 */
540static int me_unknown(struct page *p, unsigned long pfn)
541{
542 printk(KERN_ERR "MCE %#lx: Unknown page state\n", pfn);
543 return FAILED;
544}
545
546/*
547 * Clean (or cleaned) page cache page.
548 */
549static int me_pagecache_clean(struct page *p, unsigned long pfn)
550{
551 int err;
552 int ret = FAILED;
553 struct address_space *mapping;
554
555 delete_from_lru_cache(p);
556
557 /*
558 * For anonymous pages we're done the only reference left
559 * should be the one m_f() holds.
560 */
561 if (PageAnon(p))
562 return RECOVERED;
563
564 /*
565 * Now truncate the page in the page cache. This is really
566 * more like a "temporary hole punch"
567 * Don't do this for block devices when someone else
568 * has a reference, because it could be file system metadata
569 * and that's not safe to truncate.
570 */
571 mapping = page_mapping(p);
572 if (!mapping) {
573 /*
574 * Page has been teared down in the meanwhile
575 */
576 return FAILED;
577 }
578
579 /*
580 * Truncation is a bit tricky. Enable it per file system for now.
581 *
582 * Open: to take i_mutex or not for this? Right now we don't.
583 */
584 if (mapping->a_ops->error_remove_page) {
585 err = mapping->a_ops->error_remove_page(mapping, p);
586 if (err != 0) {
587 printk(KERN_INFO "MCE %#lx: Failed to punch page: %d\n",
588 pfn, err);
589 } else if (page_has_private(p) &&
590 !try_to_release_page(p, GFP_NOIO)) {
591 pr_info("MCE %#lx: failed to release buffers\n", pfn);
592 } else {
593 ret = RECOVERED;
594 }
595 } else {
596 /*
597 * If the file system doesn't support it just invalidate
598 * This fails on dirty or anything with private pages
599 */
600 if (invalidate_inode_page(p))
601 ret = RECOVERED;
602 else
603 printk(KERN_INFO "MCE %#lx: Failed to invalidate\n",
604 pfn);
605 }
606 return ret;
607}
608
609/*
610 * Dirty pagecache page
611 * Issues: when the error hit a hole page the error is not properly
612 * propagated.
613 */
614static int me_pagecache_dirty(struct page *p, unsigned long pfn)
615{
616 struct address_space *mapping = page_mapping(p);
617
618 SetPageError(p);
619 /* TBD: print more information about the file. */
620 if (mapping) {
621 /*
622 * IO error will be reported by write(), fsync(), etc.
623 * who check the mapping.
624 * This way the application knows that something went
625 * wrong with its dirty file data.
626 *
627 * There's one open issue:
628 *
629 * The EIO will be only reported on the next IO
630 * operation and then cleared through the IO map.
631 * Normally Linux has two mechanisms to pass IO error
632 * first through the AS_EIO flag in the address space
633 * and then through the PageError flag in the page.
634 * Since we drop pages on memory failure handling the
635 * only mechanism open to use is through AS_AIO.
636 *
637 * This has the disadvantage that it gets cleared on
638 * the first operation that returns an error, while
639 * the PageError bit is more sticky and only cleared
640 * when the page is reread or dropped. If an
641 * application assumes it will always get error on
642 * fsync, but does other operations on the fd before
643 * and the page is dropped between then the error
644 * will not be properly reported.
645 *
646 * This can already happen even without hwpoisoned
647 * pages: first on metadata IO errors (which only
648 * report through AS_EIO) or when the page is dropped
649 * at the wrong time.
650 *
651 * So right now we assume that the application DTRT on
652 * the first EIO, but we're not worse than other parts
653 * of the kernel.
654 */
655 mapping_set_error(mapping, EIO);
656 }
657
658 return me_pagecache_clean(p, pfn);
659}
660
661/*
662 * Clean and dirty swap cache.
663 *
664 * Dirty swap cache page is tricky to handle. The page could live both in page
665 * cache and swap cache(ie. page is freshly swapped in). So it could be
666 * referenced concurrently by 2 types of PTEs:
667 * normal PTEs and swap PTEs. We try to handle them consistently by calling
668 * try_to_unmap(TTU_IGNORE_HWPOISON) to convert the normal PTEs to swap PTEs,
669 * and then
670 * - clear dirty bit to prevent IO
671 * - remove from LRU
672 * - but keep in the swap cache, so that when we return to it on
673 * a later page fault, we know the application is accessing
674 * corrupted data and shall be killed (we installed simple
675 * interception code in do_swap_page to catch it).
676 *
677 * Clean swap cache pages can be directly isolated. A later page fault will
678 * bring in the known good data from disk.
679 */
680static int me_swapcache_dirty(struct page *p, unsigned long pfn)
681{
682 ClearPageDirty(p);
683 /* Trigger EIO in shmem: */
684 ClearPageUptodate(p);
685
686 if (!delete_from_lru_cache(p))
687 return DELAYED;
688 else
689 return FAILED;
690}
691
692static int me_swapcache_clean(struct page *p, unsigned long pfn)
693{
694 delete_from_swap_cache(p);
695
696 if (!delete_from_lru_cache(p))
697 return RECOVERED;
698 else
699 return FAILED;
700}
701
702/*
703 * Huge pages. Needs work.
704 * Issues:
705 * - Error on hugepage is contained in hugepage unit (not in raw page unit.)
706 * To narrow down kill region to one page, we need to break up pmd.
707 */
708static int me_huge_page(struct page *p, unsigned long pfn)
709{
710 int res = 0;
711 struct page *hpage = compound_head(p);
712 /*
713 * We can safely recover from error on free or reserved (i.e.
714 * not in-use) hugepage by dequeuing it from freelist.
715 * To check whether a hugepage is in-use or not, we can't use
716 * page->lru because it can be used in other hugepage operations,
717 * such as __unmap_hugepage_range() and gather_surplus_pages().
718 * So instead we use page_mapping() and PageAnon().
719 * We assume that this function is called with page lock held,
720 * so there is no race between isolation and mapping/unmapping.
721 */
722 if (!(page_mapping(hpage) || PageAnon(hpage))) {
723 res = dequeue_hwpoisoned_huge_page(hpage);
724 if (!res)
725 return RECOVERED;
726 }
727 return DELAYED;
728}
729
730/*
731 * Various page states we can handle.
732 *
733 * A page state is defined by its current page->flags bits.
734 * The table matches them in order and calls the right handler.
735 *
736 * This is quite tricky because we can access page at any time
737 * in its live cycle, so all accesses have to be extremely careful.
738 *
739 * This is not complete. More states could be added.
740 * For any missing state don't attempt recovery.
741 */
742
743#define dirty (1UL << PG_dirty)
744#define sc (1UL << PG_swapcache)
745#define unevict (1UL << PG_unevictable)
746#define mlock (1UL << PG_mlocked)
747#define writeback (1UL << PG_writeback)
748#define lru (1UL << PG_lru)
749#define swapbacked (1UL << PG_swapbacked)
750#define head (1UL << PG_head)
751#define tail (1UL << PG_tail)
752#define compound (1UL << PG_compound)
753#define slab (1UL << PG_slab)
754#define reserved (1UL << PG_reserved)
755
756static struct page_state {
757 unsigned long mask;
758 unsigned long res;
759 char *msg;
760 int (*action)(struct page *p, unsigned long pfn);
761} error_states[] = {
762 { reserved, reserved, "reserved kernel", me_kernel },
763 /*
764 * free pages are specially detected outside this table:
765 * PG_buddy pages only make a small fraction of all free pages.
766 */
767
768 /*
769 * Could in theory check if slab page is free or if we can drop
770 * currently unused objects without touching them. But just
771 * treat it as standard kernel for now.
772 */
773 { slab, slab, "kernel slab", me_kernel },
774
775#ifdef CONFIG_PAGEFLAGS_EXTENDED
776 { head, head, "huge", me_huge_page },
777 { tail, tail, "huge", me_huge_page },
778#else
779 { compound, compound, "huge", me_huge_page },
780#endif
781
782 { sc|dirty, sc|dirty, "dirty swapcache", me_swapcache_dirty },
783 { sc|dirty, sc, "clean swapcache", me_swapcache_clean },
784
785 { mlock|dirty, mlock|dirty, "dirty mlocked LRU", me_pagecache_dirty },
786 { mlock|dirty, mlock, "clean mlocked LRU", me_pagecache_clean },
787
788 { unevict|dirty, unevict|dirty, "dirty unevictable LRU", me_pagecache_dirty },
789 { unevict|dirty, unevict, "clean unevictable LRU", me_pagecache_clean },
790
791 { lru|dirty, lru|dirty, "dirty LRU", me_pagecache_dirty },
792 { lru|dirty, lru, "clean LRU", me_pagecache_clean },
793
794 /*
795 * Catchall entry: must be at end.
796 */
797 { 0, 0, "unknown page state", me_unknown },
798};
799
800#undef dirty
801#undef sc
802#undef unevict
803#undef mlock
804#undef writeback
805#undef lru
806#undef swapbacked
807#undef head
808#undef tail
809#undef compound
810#undef slab
811#undef reserved
812
813/*
814 * "Dirty/Clean" indication is not 100% accurate due to the possibility of
815 * setting PG_dirty outside page lock. See also comment above set_page_dirty().
816 */
817static void action_result(unsigned long pfn, char *msg, int result)
818{
819 pr_err("MCE %#lx: %s page recovery: %s\n",
820 pfn, msg, action_name[result]);
821}
822
823static int page_action(struct page_state *ps, struct page *p,
824 unsigned long pfn)
825{
826 int result;
827 int count;
828
829 result = ps->action(p, pfn);
830 action_result(pfn, ps->msg, result);
831
832 count = page_count(p) - 1;
833 if (ps->action == me_swapcache_dirty && result == DELAYED)
834 count--;
835 if (count != 0) {
836 printk(KERN_ERR
837 "MCE %#lx: %s page still referenced by %d users\n",
838 pfn, ps->msg, count);
839 result = FAILED;
840 }
841
842 /* Could do more checks here if page looks ok */
843 /*
844 * Could adjust zone counters here to correct for the missing page.
845 */
846
847 return (result == RECOVERED || result == DELAYED) ? 0 : -EBUSY;
848}
849
850/*
851 * Do all that is necessary to remove user space mappings. Unmap
852 * the pages and send SIGBUS to the processes if the data was dirty.
853 */
854static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
855 int trapno, int flags, struct page **hpagep)
856{
857 enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
858 struct address_space *mapping;
859 LIST_HEAD(tokill);
860 int ret;
861 int kill = 1, forcekill;
862 struct page *hpage = *hpagep;
863 struct page *ppage;
864
865 if (PageReserved(p) || PageSlab(p))
866 return SWAP_SUCCESS;
867
868 /*
869 * This check implies we don't kill processes if their pages
870 * are in the swap cache early. Those are always late kills.
871 */
872 if (!page_mapped(hpage))
873 return SWAP_SUCCESS;
874
875 if (PageKsm(p))
876 return SWAP_FAIL;
877
878 if (PageSwapCache(p)) {
879 printk(KERN_ERR
880 "MCE %#lx: keeping poisoned page in swap cache\n", pfn);
881 ttu |= TTU_IGNORE_HWPOISON;
882 }
883
884 /*
885 * Propagate the dirty bit from PTEs to struct page first, because we
886 * need this to decide if we should kill or just drop the page.
887 * XXX: the dirty test could be racy: set_page_dirty() may not always
888 * be called inside page lock (it's recommended but not enforced).
889 */
890 mapping = page_mapping(hpage);
891 if (!(flags & MF_MUST_KILL) && !PageDirty(hpage) && mapping &&
892 mapping_cap_writeback_dirty(mapping)) {
893 if (page_mkclean(hpage)) {
894 SetPageDirty(hpage);
895 } else {
896 kill = 0;
897 ttu |= TTU_IGNORE_HWPOISON;
898 printk(KERN_INFO
899 "MCE %#lx: corrupted page was clean: dropped without side effects\n",
900 pfn);
901 }
902 }
903
904 /*
905 * ppage: poisoned page
906 * if p is regular page(4k page)
907 * ppage == real poisoned page;
908 * else p is hugetlb or THP, ppage == head page.
909 */
910 ppage = hpage;
911
912 if (PageTransHuge(hpage)) {
913 /*
914 * Verify that this isn't a hugetlbfs head page, the check for
915 * PageAnon is just for avoid tripping a split_huge_page
916 * internal debug check, as split_huge_page refuses to deal with
917 * anything that isn't an anon page. PageAnon can't go away fro
918 * under us because we hold a refcount on the hpage, without a
919 * refcount on the hpage. split_huge_page can't be safely called
920 * in the first place, having a refcount on the tail isn't
921 * enough * to be safe.
922 */
923 if (!PageHuge(hpage) && PageAnon(hpage)) {
924 if (unlikely(split_huge_page(hpage))) {
925 /*
926 * FIXME: if splitting THP is failed, it is
927 * better to stop the following operation rather
928 * than causing panic by unmapping. System might
929 * survive if the page is freed later.
930 */
931 printk(KERN_INFO
932 "MCE %#lx: failed to split THP\n", pfn);
933
934 BUG_ON(!PageHWPoison(p));
935 return SWAP_FAIL;
936 }
937 /*
938 * We pinned the head page for hwpoison handling,
939 * now we split the thp and we are interested in
940 * the hwpoisoned raw page, so move the refcount
941 * to it. Similarly, page lock is shifted.
942 */
943 if (hpage != p) {
944 if (!(flags & MF_COUNT_INCREASED)) {
945 put_page(hpage);
946 get_page(p);
947 }
948 lock_page(p);
949 unlock_page(hpage);
950 *hpagep = p;
951 }
952 /* THP is split, so ppage should be the real poisoned page. */
953 ppage = p;
954 }
955 }
956
957 /*
958 * First collect all the processes that have the page
959 * mapped in dirty form. This has to be done before try_to_unmap,
960 * because ttu takes the rmap data structures down.
961 *
962 * Error handling: We ignore errors here because
963 * there's nothing that can be done.
964 */
965 if (kill)
966 collect_procs(ppage, &tokill);
967
968 ret = try_to_unmap(ppage, ttu);
969 if (ret != SWAP_SUCCESS)
970 printk(KERN_ERR "MCE %#lx: failed to unmap page (mapcount=%d)\n",
971 pfn, page_mapcount(ppage));
972
973 /*
974 * Now that the dirty bit has been propagated to the
975 * struct page and all unmaps done we can decide if
976 * killing is needed or not. Only kill when the page
977 * was dirty or the process is not restartable,
978 * otherwise the tokill list is merely
979 * freed. When there was a problem unmapping earlier
980 * use a more force-full uncatchable kill to prevent
981 * any accesses to the poisoned memory.
982 */
983 forcekill = PageDirty(ppage) || (flags & MF_MUST_KILL);
984 kill_procs(&tokill, forcekill, trapno,
985 ret != SWAP_SUCCESS, p, pfn, flags);
986
987 return ret;
988}
989
990static void set_page_hwpoison_huge_page(struct page *hpage)
991{
992 int i;
993 int nr_pages = 1 << compound_order(hpage);
994 for (i = 0; i < nr_pages; i++)
995 SetPageHWPoison(hpage + i);
996}
997
998static void clear_page_hwpoison_huge_page(struct page *hpage)
999{
1000 int i;
1001 int nr_pages = 1 << compound_order(hpage);
1002 for (i = 0; i < nr_pages; i++)
1003 ClearPageHWPoison(hpage + i);
1004}
1005
1006/**
1007 * memory_failure - Handle memory failure of a page.
1008 * @pfn: Page Number of the corrupted page
1009 * @trapno: Trap number reported in the signal to user space.
1010 * @flags: fine tune action taken
1011 *
1012 * This function is called by the low level machine check code
1013 * of an architecture when it detects hardware memory corruption
1014 * of a page. It tries its best to recover, which includes
1015 * dropping pages, killing processes etc.
1016 *
1017 * The function is primarily of use for corruptions that
1018 * happen outside the current execution context (e.g. when
1019 * detected by a background scrubber)
1020 *
1021 * Must run in process context (e.g. a work queue) with interrupts
1022 * enabled and no spinlocks hold.
1023 */
1024int memory_failure(unsigned long pfn, int trapno, int flags)
1025{
1026 struct page_state *ps;
1027 struct page *p;
1028 struct page *hpage;
1029 int res;
1030 unsigned int nr_pages;
1031 unsigned long page_flags;
1032
1033 if (!sysctl_memory_failure_recovery)
1034 panic("Memory failure from trap %d on page %lx", trapno, pfn);
1035
1036 if (!pfn_valid(pfn)) {
1037 printk(KERN_ERR
1038 "MCE %#lx: memory outside kernel control\n",
1039 pfn);
1040 return -ENXIO;
1041 }
1042
1043 p = pfn_to_page(pfn);
1044 hpage = compound_head(p);
1045 if (TestSetPageHWPoison(p)) {
1046 printk(KERN_ERR "MCE %#lx: already hardware poisoned\n", pfn);
1047 return 0;
1048 }
1049
1050 /*
1051 * Currently errors on hugetlbfs pages are measured in hugepage units,
1052 * so nr_pages should be 1 << compound_order. OTOH when errors are on
1053 * transparent hugepages, they are supposed to be split and error
1054 * measurement is done in normal page units. So nr_pages should be one
1055 * in this case.
1056 */
1057 if (PageHuge(p))
1058 nr_pages = 1 << compound_order(hpage);
1059 else /* normal page or thp */
1060 nr_pages = 1;
1061 atomic_long_add(nr_pages, &num_poisoned_pages);
1062
1063 /*
1064 * We need/can do nothing about count=0 pages.
1065 * 1) it's a free page, and therefore in safe hand:
1066 * prep_new_page() will be the gate keeper.
1067 * 2) it's a free hugepage, which is also safe:
1068 * an affected hugepage will be dequeued from hugepage freelist,
1069 * so there's no concern about reusing it ever after.
1070 * 3) it's part of a non-compound high order page.
1071 * Implies some kernel user: cannot stop them from
1072 * R/W the page; let's pray that the page has been
1073 * used and will be freed some time later.
1074 * In fact it's dangerous to directly bump up page count from 0,
1075 * that may make page_freeze_refs()/page_unfreeze_refs() mismatch.
1076 */
1077 if (!(flags & MF_COUNT_INCREASED) &&
1078 !get_page_unless_zero(hpage)) {
1079 if (is_free_buddy_page(p)) {
1080 action_result(pfn, "free buddy", DELAYED);
1081 return 0;
1082 } else if (PageHuge(hpage)) {
1083 /*
1084 * Check "filter hit" and "race with other subpage."
1085 */
1086 lock_page(hpage);
1087 if (PageHWPoison(hpage)) {
1088 if ((hwpoison_filter(p) && TestClearPageHWPoison(p))
1089 || (p != hpage && TestSetPageHWPoison(hpage))) {
1090 atomic_long_sub(nr_pages, &num_poisoned_pages);
1091 unlock_page(hpage);
1092 return 0;
1093 }
1094 }
1095 set_page_hwpoison_huge_page(hpage);
1096 res = dequeue_hwpoisoned_huge_page(hpage);
1097 action_result(pfn, "free huge",
1098 res ? IGNORED : DELAYED);
1099 unlock_page(hpage);
1100 return res;
1101 } else {
1102 action_result(pfn, "high order kernel", IGNORED);
1103 return -EBUSY;
1104 }
1105 }
1106
1107 /*
1108 * We ignore non-LRU pages for good reasons.
1109 * - PG_locked is only well defined for LRU pages and a few others
1110 * - to avoid races with __set_page_locked()
1111 * - to avoid races with __SetPageSlab*() (and more non-atomic ops)
1112 * The check (unnecessarily) ignores LRU pages being isolated and
1113 * walked by the page reclaim code, however that's not a big loss.
1114 */
1115 if (!PageHuge(p) && !PageTransTail(p)) {
1116 if (!PageLRU(p))
1117 shake_page(p, 0);
1118 if (!PageLRU(p)) {
1119 /*
1120 * shake_page could have turned it free.
1121 */
1122 if (is_free_buddy_page(p)) {
1123 if (flags & MF_COUNT_INCREASED)
1124 action_result(pfn, "free buddy", DELAYED);
1125 else
1126 action_result(pfn, "free buddy, 2nd try", DELAYED);
1127 return 0;
1128 }
1129 action_result(pfn, "non LRU", IGNORED);
1130 put_page(p);
1131 return -EBUSY;
1132 }
1133 }
1134
1135 /*
1136 * Lock the page and wait for writeback to finish.
1137 * It's very difficult to mess with pages currently under IO
1138 * and in many cases impossible, so we just avoid it here.
1139 */
1140 lock_page(hpage);
1141
1142 /*
1143 * We use page flags to determine what action should be taken, but
1144 * the flags can be modified by the error containment action. One
1145 * example is an mlocked page, where PG_mlocked is cleared by
1146 * page_remove_rmap() in try_to_unmap_one(). So to determine page status
1147 * correctly, we save a copy of the page flags at this time.
1148 */
1149 page_flags = p->flags;
1150
1151 /*
1152 * unpoison always clear PG_hwpoison inside page lock
1153 */
1154 if (!PageHWPoison(p)) {
1155 printk(KERN_ERR "MCE %#lx: just unpoisoned\n", pfn);
1156 atomic_long_sub(nr_pages, &num_poisoned_pages);
1157 put_page(hpage);
1158 res = 0;
1159 goto out;
1160 }
1161 if (hwpoison_filter(p)) {
1162 if (TestClearPageHWPoison(p))
1163 atomic_long_sub(nr_pages, &num_poisoned_pages);
1164 unlock_page(hpage);
1165 put_page(hpage);
1166 return 0;
1167 }
1168
1169 /*
1170 * For error on the tail page, we should set PG_hwpoison
1171 * on the head page to show that the hugepage is hwpoisoned
1172 */
1173 if (PageHuge(p) && PageTail(p) && TestSetPageHWPoison(hpage)) {
1174 action_result(pfn, "hugepage already hardware poisoned",
1175 IGNORED);
1176 unlock_page(hpage);
1177 put_page(hpage);
1178 return 0;
1179 }
1180 /*
1181 * Set PG_hwpoison on all pages in an error hugepage,
1182 * because containment is done in hugepage unit for now.
1183 * Since we have done TestSetPageHWPoison() for the head page with
1184 * page lock held, we can safely set PG_hwpoison bits on tail pages.
1185 */
1186 if (PageHuge(p))
1187 set_page_hwpoison_huge_page(hpage);
1188
1189 wait_on_page_writeback(p);
1190
1191 /*
1192 * Now take care of user space mappings.
1193 * Abort on fail: __delete_from_page_cache() assumes unmapped page.
1194 *
1195 * When the raw error page is thp tail page, hpage points to the raw
1196 * page after thp split.
1197 */
1198 if (hwpoison_user_mappings(p, pfn, trapno, flags, &hpage)
1199 != SWAP_SUCCESS) {
1200 printk(KERN_ERR "MCE %#lx: cannot unmap page, give up\n", pfn);
1201 res = -EBUSY;
1202 goto out;
1203 }
1204
1205 /*
1206 * Torn down by someone else?
1207 */
1208 if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) {
1209 action_result(pfn, "already truncated LRU", IGNORED);
1210 res = -EBUSY;
1211 goto out;
1212 }
1213
1214 res = -EBUSY;
1215 /*
1216 * The first check uses the current page flags which may not have any
1217 * relevant information. The second check with the saved page flagss is
1218 * carried out only if the first check can't determine the page status.
1219 */
1220 for (ps = error_states;; ps++)
1221 if ((p->flags & ps->mask) == ps->res)
1222 break;
1223
1224 page_flags |= (p->flags & (1UL << PG_dirty));
1225
1226 if (!ps->mask)
1227 for (ps = error_states;; ps++)
1228 if ((page_flags & ps->mask) == ps->res)
1229 break;
1230 res = page_action(ps, p, pfn);
1231out:
1232 unlock_page(hpage);
1233 return res;
1234}
1235EXPORT_SYMBOL_GPL(memory_failure);
1236
1237#define MEMORY_FAILURE_FIFO_ORDER 4
1238#define MEMORY_FAILURE_FIFO_SIZE (1 << MEMORY_FAILURE_FIFO_ORDER)
1239
1240struct memory_failure_entry {
1241 unsigned long pfn;
1242 int trapno;
1243 int flags;
1244};
1245
1246struct memory_failure_cpu {
1247 DECLARE_KFIFO(fifo, struct memory_failure_entry,
1248 MEMORY_FAILURE_FIFO_SIZE);
1249 spinlock_t lock;
1250 struct work_struct work;
1251};
1252
1253static DEFINE_PER_CPU(struct memory_failure_cpu, memory_failure_cpu);
1254
1255/**
1256 * memory_failure_queue - Schedule handling memory failure of a page.
1257 * @pfn: Page Number of the corrupted page
1258 * @trapno: Trap number reported in the signal to user space.
1259 * @flags: Flags for memory failure handling
1260 *
1261 * This function is called by the low level hardware error handler
1262 * when it detects hardware memory corruption of a page. It schedules
1263 * the recovering of error page, including dropping pages, killing
1264 * processes etc.
1265 *
1266 * The function is primarily of use for corruptions that
1267 * happen outside the current execution context (e.g. when
1268 * detected by a background scrubber)
1269 *
1270 * Can run in IRQ context.
1271 */
1272void memory_failure_queue(unsigned long pfn, int trapno, int flags)
1273{
1274 struct memory_failure_cpu *mf_cpu;
1275 unsigned long proc_flags;
1276 struct memory_failure_entry entry = {
1277 .pfn = pfn,
1278 .trapno = trapno,
1279 .flags = flags,
1280 };
1281
1282 mf_cpu = &get_cpu_var(memory_failure_cpu);
1283 spin_lock_irqsave(&mf_cpu->lock, proc_flags);
1284 if (kfifo_put(&mf_cpu->fifo, entry))
1285 schedule_work_on(smp_processor_id(), &mf_cpu->work);
1286 else
1287 pr_err("Memory failure: buffer overflow when queuing memory failure at %#lx\n",
1288 pfn);
1289 spin_unlock_irqrestore(&mf_cpu->lock, proc_flags);
1290 put_cpu_var(memory_failure_cpu);
1291}
1292EXPORT_SYMBOL_GPL(memory_failure_queue);
1293
1294static void memory_failure_work_func(struct work_struct *work)
1295{
1296 struct memory_failure_cpu *mf_cpu;
1297 struct memory_failure_entry entry = { 0, };
1298 unsigned long proc_flags;
1299 int gotten;
1300
1301 mf_cpu = &__get_cpu_var(memory_failure_cpu);
1302 for (;;) {
1303 spin_lock_irqsave(&mf_cpu->lock, proc_flags);
1304 gotten = kfifo_get(&mf_cpu->fifo, &entry);
1305 spin_unlock_irqrestore(&mf_cpu->lock, proc_flags);
1306 if (!gotten)
1307 break;
1308 if (entry.flags & MF_SOFT_OFFLINE)
1309 soft_offline_page(pfn_to_page(entry.pfn), entry.flags);
1310 else
1311 memory_failure(entry.pfn, entry.trapno, entry.flags);
1312 }
1313}
1314
1315static int __init memory_failure_init(void)
1316{
1317 struct memory_failure_cpu *mf_cpu;
1318 int cpu;
1319
1320 for_each_possible_cpu(cpu) {
1321 mf_cpu = &per_cpu(memory_failure_cpu, cpu);
1322 spin_lock_init(&mf_cpu->lock);
1323 INIT_KFIFO(mf_cpu->fifo);
1324 INIT_WORK(&mf_cpu->work, memory_failure_work_func);
1325 }
1326
1327 return 0;
1328}
1329core_initcall(memory_failure_init);
1330
1331/**
1332 * unpoison_memory - Unpoison a previously poisoned page
1333 * @pfn: Page number of the to be unpoisoned page
1334 *
1335 * Software-unpoison a page that has been poisoned by
1336 * memory_failure() earlier.
1337 *
1338 * This is only done on the software-level, so it only works
1339 * for linux injected failures, not real hardware failures
1340 *
1341 * Returns 0 for success, otherwise -errno.
1342 */
1343int unpoison_memory(unsigned long pfn)
1344{
1345 struct page *page;
1346 struct page *p;
1347 int freeit = 0;
1348 unsigned int nr_pages;
1349
1350 if (!pfn_valid(pfn))
1351 return -ENXIO;
1352
1353 p = pfn_to_page(pfn);
1354 page = compound_head(p);
1355
1356 if (!PageHWPoison(p)) {
1357 pr_info("MCE: Page was already unpoisoned %#lx\n", pfn);
1358 return 0;
1359 }
1360
1361 /*
1362 * unpoison_memory() can encounter thp only when the thp is being
1363 * worked by memory_failure() and the page lock is not held yet.
1364 * In such case, we yield to memory_failure() and make unpoison fail.
1365 */
1366 if (!PageHuge(page) && PageTransHuge(page)) {
1367 pr_info("MCE: Memory failure is now running on %#lx\n", pfn);
1368 return 0;
1369 }
1370
1371 nr_pages = 1 << compound_order(page);
1372
1373 if (!get_page_unless_zero(page)) {
1374 /*
1375 * Since HWPoisoned hugepage should have non-zero refcount,
1376 * race between memory failure and unpoison seems to happen.
1377 * In such case unpoison fails and memory failure runs
1378 * to the end.
1379 */
1380 if (PageHuge(page)) {
1381 pr_info("MCE: Memory failure is now running on free hugepage %#lx\n", pfn);
1382 return 0;
1383 }
1384 if (TestClearPageHWPoison(p))
1385 atomic_long_dec(&num_poisoned_pages);
1386 pr_info("MCE: Software-unpoisoned free page %#lx\n", pfn);
1387 return 0;
1388 }
1389
1390 lock_page(page);
1391 /*
1392 * This test is racy because PG_hwpoison is set outside of page lock.
1393 * That's acceptable because that won't trigger kernel panic. Instead,
1394 * the PG_hwpoison page will be caught and isolated on the entrance to
1395 * the free buddy page pool.
1396 */
1397 if (TestClearPageHWPoison(page)) {
1398 pr_info("MCE: Software-unpoisoned page %#lx\n", pfn);
1399 atomic_long_sub(nr_pages, &num_poisoned_pages);
1400 freeit = 1;
1401 if (PageHuge(page))
1402 clear_page_hwpoison_huge_page(page);
1403 }
1404 unlock_page(page);
1405
1406 put_page(page);
1407 if (freeit && !(pfn == my_zero_pfn(0) && page_count(p) == 1))
1408 put_page(page);
1409
1410 return 0;
1411}
1412EXPORT_SYMBOL(unpoison_memory);
1413
1414static struct page *new_page(struct page *p, unsigned long private, int **x)
1415{
1416 int nid = page_to_nid(p);
1417 if (PageHuge(p))
1418 return alloc_huge_page_node(page_hstate(compound_head(p)),
1419 nid);
1420 else
1421 return alloc_pages_exact_node(nid, GFP_HIGHUSER_MOVABLE, 0);
1422}
1423
1424/*
1425 * Safely get reference count of an arbitrary page.
1426 * Returns 0 for a free page, -EIO for a zero refcount page
1427 * that is not free, and 1 for any other page type.
1428 * For 1 the page is returned with increased page count, otherwise not.
1429 */
1430static int __get_any_page(struct page *p, unsigned long pfn, int flags)
1431{
1432 int ret;
1433
1434 if (flags & MF_COUNT_INCREASED)
1435 return 1;
1436
1437 /*
1438 * When the target page is a free hugepage, just remove it
1439 * from free hugepage list.
1440 */
1441 if (!get_page_unless_zero(compound_head(p))) {
1442 if (PageHuge(p)) {
1443 pr_info("%s: %#lx free huge page\n", __func__, pfn);
1444 ret = 0;
1445 } else if (is_free_buddy_page(p)) {
1446 pr_info("%s: %#lx free buddy page\n", __func__, pfn);
1447 ret = 0;
1448 } else {
1449 pr_info("%s: %#lx: unknown zero refcount page type %lx\n",
1450 __func__, pfn, p->flags);
1451 ret = -EIO;
1452 }
1453 } else {
1454 /* Not a free page */
1455 ret = 1;
1456 }
1457 return ret;
1458}
1459
1460static int get_any_page(struct page *page, unsigned long pfn, int flags)
1461{
1462 int ret = __get_any_page(page, pfn, flags);
1463
1464 if (ret == 1 && !PageHuge(page) && !PageLRU(page)) {
1465 /*
1466 * Try to free it.
1467 */
1468 put_page(page);
1469 shake_page(page, 1);
1470
1471 /*
1472 * Did it turn free?
1473 */
1474 ret = __get_any_page(page, pfn, 0);
1475 if (!PageLRU(page)) {
1476 pr_info("soft_offline: %#lx: unknown non LRU page type %lx\n",
1477 pfn, page->flags);
1478 return -EIO;
1479 }
1480 }
1481 return ret;
1482}
1483
1484static int soft_offline_huge_page(struct page *page, int flags)
1485{
1486 int ret;
1487 unsigned long pfn = page_to_pfn(page);
1488 struct page *hpage = compound_head(page);
1489 LIST_HEAD(pagelist);
1490
1491 /*
1492 * This double-check of PageHWPoison is to avoid the race with
1493 * memory_failure(). See also comment in __soft_offline_page().
1494 */
1495 lock_page(hpage);
1496 if (PageHWPoison(hpage)) {
1497 unlock_page(hpage);
1498 put_page(hpage);
1499 pr_info("soft offline: %#lx hugepage already poisoned\n", pfn);
1500 return -EBUSY;
1501 }
1502 unlock_page(hpage);
1503
1504 /* Keep page count to indicate a given hugepage is isolated. */
1505 list_move(&hpage->lru, &pagelist);
1506 ret = migrate_pages(&pagelist, new_page, MPOL_MF_MOVE_ALL,
1507 MIGRATE_SYNC, MR_MEMORY_FAILURE);
1508 if (ret) {
1509 pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
1510 pfn, ret, page->flags);
1511 /*
1512 * We know that soft_offline_huge_page() tries to migrate
1513 * only one hugepage pointed to by hpage, so we need not
1514 * run through the pagelist here.
1515 */
1516 putback_active_hugepage(hpage);
1517 if (ret > 0)
1518 ret = -EIO;
1519 } else {
1520 /* overcommit hugetlb page will be freed to buddy */
1521 if (PageHuge(page)) {
1522 set_page_hwpoison_huge_page(hpage);
1523 dequeue_hwpoisoned_huge_page(hpage);
1524 atomic_long_add(1 << compound_order(hpage),
1525 &num_poisoned_pages);
1526 } else {
1527 SetPageHWPoison(page);
1528 atomic_long_inc(&num_poisoned_pages);
1529 }
1530 }
1531 return ret;
1532}
1533
1534static int __soft_offline_page(struct page *page, int flags)
1535{
1536 int ret;
1537 unsigned long pfn = page_to_pfn(page);
1538
1539 /*
1540 * Check PageHWPoison again inside page lock because PageHWPoison
1541 * is set by memory_failure() outside page lock. Note that
1542 * memory_failure() also double-checks PageHWPoison inside page lock,
1543 * so there's no race between soft_offline_page() and memory_failure().
1544 */
1545 lock_page(page);
1546 wait_on_page_writeback(page);
1547 if (PageHWPoison(page)) {
1548 unlock_page(page);
1549 put_page(page);
1550 pr_info("soft offline: %#lx page already poisoned\n", pfn);
1551 return -EBUSY;
1552 }
1553 /*
1554 * Try to invalidate first. This should work for
1555 * non dirty unmapped page cache pages.
1556 */
1557 ret = invalidate_inode_page(page);
1558 unlock_page(page);
1559 /*
1560 * RED-PEN would be better to keep it isolated here, but we
1561 * would need to fix isolation locking first.
1562 */
1563 if (ret == 1) {
1564 put_page(page);
1565 pr_info("soft_offline: %#lx: invalidated\n", pfn);
1566 SetPageHWPoison(page);
1567 atomic_long_inc(&num_poisoned_pages);
1568 return 0;
1569 }
1570
1571 /*
1572 * Simple invalidation didn't work.
1573 * Try to migrate to a new page instead. migrate.c
1574 * handles a large number of cases for us.
1575 */
1576 ret = isolate_lru_page(page);
1577 /*
1578 * Drop page reference which is came from get_any_page()
1579 * successful isolate_lru_page() already took another one.
1580 */
1581 put_page(page);
1582 if (!ret) {
1583 LIST_HEAD(pagelist);
1584 inc_zone_page_state(page, NR_ISOLATED_ANON +
1585 page_is_file_cache(page));
1586 list_add(&page->lru, &pagelist);
1587 ret = migrate_pages(&pagelist, new_page, MPOL_MF_MOVE_ALL,
1588 MIGRATE_SYNC, MR_MEMORY_FAILURE);
1589 if (ret) {
1590 if (!list_empty(&pagelist)) {
1591 list_del(&page->lru);
1592 dec_zone_page_state(page, NR_ISOLATED_ANON +
1593 page_is_file_cache(page));
1594 putback_lru_page(page);
1595 }
1596
1597 pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
1598 pfn, ret, page->flags);
1599 if (ret > 0)
1600 ret = -EIO;
1601 } else {
1602 /*
1603 * After page migration succeeds, the source page can
1604 * be trapped in pagevec and actual freeing is delayed.
1605 * Freeing code works differently based on PG_hwpoison,
1606 * so there's a race. We need to make sure that the
1607 * source page should be freed back to buddy before
1608 * setting PG_hwpoison.
1609 */
1610 if (!is_free_buddy_page(page))
1611 lru_add_drain_all();
1612 if (!is_free_buddy_page(page))
1613 drain_all_pages();
1614 SetPageHWPoison(page);
1615 if (!is_free_buddy_page(page))
1616 pr_info("soft offline: %#lx: page leaked\n",
1617 pfn);
1618 atomic_long_inc(&num_poisoned_pages);
1619 }
1620 } else {
1621 pr_info("soft offline: %#lx: isolation failed: %d, page count %d, type %lx\n",
1622 pfn, ret, page_count(page), page->flags);
1623 }
1624 return ret;
1625}
1626
1627/**
1628 * soft_offline_page - Soft offline a page.
1629 * @page: page to offline
1630 * @flags: flags. Same as memory_failure().
1631 *
1632 * Returns 0 on success, otherwise negated errno.
1633 *
1634 * Soft offline a page, by migration or invalidation,
1635 * without killing anything. This is for the case when
1636 * a page is not corrupted yet (so it's still valid to access),
1637 * but has had a number of corrected errors and is better taken
1638 * out.
1639 *
1640 * The actual policy on when to do that is maintained by
1641 * user space.
1642 *
1643 * This should never impact any application or cause data loss,
1644 * however it might take some time.
1645 *
1646 * This is not a 100% solution for all memory, but tries to be
1647 * ``good enough'' for the majority of memory.
1648 */
1649int soft_offline_page(struct page *page, int flags)
1650{
1651 int ret;
1652 unsigned long pfn = page_to_pfn(page);
1653 struct page *hpage = compound_head(page);
1654
1655 if (PageHWPoison(page)) {
1656 pr_info("soft offline: %#lx page already poisoned\n", pfn);
1657 return -EBUSY;
1658 }
1659 if (!PageHuge(page) && PageTransHuge(hpage)) {
1660 if (PageAnon(hpage) && unlikely(split_huge_page(hpage))) {
1661 pr_info("soft offline: %#lx: failed to split THP\n",
1662 pfn);
1663 return -EBUSY;
1664 }
1665 }
1666
1667 /*
1668 * The lock_memory_hotplug prevents a race with memory hotplug.
1669 * This is a big hammer, a better would be nicer.
1670 */
1671 lock_memory_hotplug();
1672
1673 /*
1674 * Isolate the page, so that it doesn't get reallocated if it
1675 * was free. This flag should be kept set until the source page
1676 * is freed and PG_hwpoison on it is set.
1677 */
1678 if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
1679 set_migratetype_isolate(page, true);
1680
1681 ret = get_any_page(page, pfn, flags);
1682 unlock_memory_hotplug();
1683 if (ret > 0) { /* for in-use pages */
1684 if (PageHuge(page))
1685 ret = soft_offline_huge_page(page, flags);
1686 else
1687 ret = __soft_offline_page(page, flags);
1688 } else if (ret == 0) { /* for free pages */
1689 if (PageHuge(page)) {
1690 set_page_hwpoison_huge_page(hpage);
1691 dequeue_hwpoisoned_huge_page(hpage);
1692 atomic_long_add(1 << compound_order(hpage),
1693 &num_poisoned_pages);
1694 } else {
1695 SetPageHWPoison(page);
1696 atomic_long_inc(&num_poisoned_pages);
1697 }
1698 }
1699 unset_migratetype_isolate(page, MIGRATE_MOVABLE);
1700 return ret;
1701}