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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// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2008, 2009 Intel Corporation
4 * Authors: Andi Kleen, Fengguang Wu
5 *
6 * High level machine check handler. Handles pages reported by the
7 * hardware as being corrupted usually due to a multi-bit ECC memory or cache
8 * failure.
9 *
10 * In addition there is a "soft offline" entry point that allows stop using
11 * not-yet-corrupted-by-suspicious pages without killing anything.
12 *
13 * Handles page cache pages in various states. The tricky part
14 * here is that we can access any page asynchronously in respect to
15 * other VM users, because memory failures could happen anytime and
16 * anywhere. This could violate some of their assumptions. This is why
17 * this code has to be extremely careful. Generally it tries to use
18 * normal locking rules, as in get the standard locks, even if that means
19 * the error handling takes potentially a long time.
20 *
21 * It can be very tempting to add handling for obscure cases here.
22 * In general any code for handling new cases should only be added iff:
23 * - You know how to test it.
24 * - You have a test that can be added to mce-test
25 * https://git.kernel.org/cgit/utils/cpu/mce/mce-test.git/
26 * - The case actually shows up as a frequent (top 10) page state in
27 * tools/vm/page-types when running a real workload.
28 *
29 * There are several operations here with exponential complexity because
30 * of unsuitable VM data structures. For example the operation to map back
31 * from RMAP chains to processes has to walk the complete process list and
32 * has non linear complexity with the number. But since memory corruptions
33 * are rare we hope to get away with this. This avoids impacting the core
34 * VM.
35 */
36#include <linux/kernel.h>
37#include <linux/mm.h>
38#include <linux/page-flags.h>
39#include <linux/kernel-page-flags.h>
40#include <linux/sched/signal.h>
41#include <linux/sched/task.h>
42#include <linux/ksm.h>
43#include <linux/rmap.h>
44#include <linux/export.h>
45#include <linux/pagemap.h>
46#include <linux/swap.h>
47#include <linux/backing-dev.h>
48#include <linux/migrate.h>
49#include <linux/suspend.h>
50#include <linux/slab.h>
51#include <linux/swapops.h>
52#include <linux/hugetlb.h>
53#include <linux/memory_hotplug.h>
54#include <linux/mm_inline.h>
55#include <linux/memremap.h>
56#include <linux/kfifo.h>
57#include <linux/ratelimit.h>
58#include <linux/page-isolation.h>
59#include <linux/pagewalk.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
69static bool __page_handle_poison(struct page *page)
70{
71 int ret;
72
73 zone_pcp_disable(page_zone(page));
74 ret = dissolve_free_huge_page(page);
75 if (!ret)
76 ret = take_page_off_buddy(page);
77 zone_pcp_enable(page_zone(page));
78
79 return ret > 0;
80}
81
82static bool page_handle_poison(struct page *page, bool hugepage_or_freepage, bool release)
83{
84 if (hugepage_or_freepage) {
85 /*
86 * Doing this check for free pages is also fine since dissolve_free_huge_page
87 * returns 0 for non-hugetlb pages as well.
88 */
89 if (!__page_handle_poison(page))
90 /*
91 * We could fail to take off the target page from buddy
92 * for example due to racy page allocation, but that's
93 * acceptable because soft-offlined page is not broken
94 * and if someone really want to use it, they should
95 * take it.
96 */
97 return false;
98 }
99
100 SetPageHWPoison(page);
101 if (release)
102 put_page(page);
103 page_ref_inc(page);
104 num_poisoned_pages_inc();
105
106 return true;
107}
108
109#if defined(CONFIG_HWPOISON_INJECT) || defined(CONFIG_HWPOISON_INJECT_MODULE)
110
111u32 hwpoison_filter_enable = 0;
112u32 hwpoison_filter_dev_major = ~0U;
113u32 hwpoison_filter_dev_minor = ~0U;
114u64 hwpoison_filter_flags_mask;
115u64 hwpoison_filter_flags_value;
116EXPORT_SYMBOL_GPL(hwpoison_filter_enable);
117EXPORT_SYMBOL_GPL(hwpoison_filter_dev_major);
118EXPORT_SYMBOL_GPL(hwpoison_filter_dev_minor);
119EXPORT_SYMBOL_GPL(hwpoison_filter_flags_mask);
120EXPORT_SYMBOL_GPL(hwpoison_filter_flags_value);
121
122static int hwpoison_filter_dev(struct page *p)
123{
124 struct address_space *mapping;
125 dev_t dev;
126
127 if (hwpoison_filter_dev_major == ~0U &&
128 hwpoison_filter_dev_minor == ~0U)
129 return 0;
130
131 /*
132 * page_mapping() does not accept slab pages.
133 */
134 if (PageSlab(p))
135 return -EINVAL;
136
137 mapping = page_mapping(p);
138 if (mapping == NULL || mapping->host == NULL)
139 return -EINVAL;
140
141 dev = mapping->host->i_sb->s_dev;
142 if (hwpoison_filter_dev_major != ~0U &&
143 hwpoison_filter_dev_major != MAJOR(dev))
144 return -EINVAL;
145 if (hwpoison_filter_dev_minor != ~0U &&
146 hwpoison_filter_dev_minor != MINOR(dev))
147 return -EINVAL;
148
149 return 0;
150}
151
152static int hwpoison_filter_flags(struct page *p)
153{
154 if (!hwpoison_filter_flags_mask)
155 return 0;
156
157 if ((stable_page_flags(p) & hwpoison_filter_flags_mask) ==
158 hwpoison_filter_flags_value)
159 return 0;
160 else
161 return -EINVAL;
162}
163
164/*
165 * This allows stress tests to limit test scope to a collection of tasks
166 * by putting them under some memcg. This prevents killing unrelated/important
167 * processes such as /sbin/init. Note that the target task may share clean
168 * pages with init (eg. libc text), which is harmless. If the target task
169 * share _dirty_ pages with another task B, the test scheme must make sure B
170 * is also included in the memcg. At last, due to race conditions this filter
171 * can only guarantee that the page either belongs to the memcg tasks, or is
172 * a freed page.
173 */
174#ifdef CONFIG_MEMCG
175u64 hwpoison_filter_memcg;
176EXPORT_SYMBOL_GPL(hwpoison_filter_memcg);
177static int hwpoison_filter_task(struct page *p)
178{
179 if (!hwpoison_filter_memcg)
180 return 0;
181
182 if (page_cgroup_ino(p) != hwpoison_filter_memcg)
183 return -EINVAL;
184
185 return 0;
186}
187#else
188static int hwpoison_filter_task(struct page *p) { return 0; }
189#endif
190
191int hwpoison_filter(struct page *p)
192{
193 if (!hwpoison_filter_enable)
194 return 0;
195
196 if (hwpoison_filter_dev(p))
197 return -EINVAL;
198
199 if (hwpoison_filter_flags(p))
200 return -EINVAL;
201
202 if (hwpoison_filter_task(p))
203 return -EINVAL;
204
205 return 0;
206}
207#else
208int hwpoison_filter(struct page *p)
209{
210 return 0;
211}
212#endif
213
214EXPORT_SYMBOL_GPL(hwpoison_filter);
215
216/*
217 * Kill all processes that have a poisoned page mapped and then isolate
218 * the page.
219 *
220 * General strategy:
221 * Find all processes having the page mapped and kill them.
222 * But we keep a page reference around so that the page is not
223 * actually freed yet.
224 * Then stash the page away
225 *
226 * There's no convenient way to get back to mapped processes
227 * from the VMAs. So do a brute-force search over all
228 * running processes.
229 *
230 * Remember that machine checks are not common (or rather
231 * if they are common you have other problems), so this shouldn't
232 * be a performance issue.
233 *
234 * Also there are some races possible while we get from the
235 * error detection to actually handle it.
236 */
237
238struct to_kill {
239 struct list_head nd;
240 struct task_struct *tsk;
241 unsigned long addr;
242 short size_shift;
243};
244
245/*
246 * Send all the processes who have the page mapped a signal.
247 * ``action optional'' if they are not immediately affected by the error
248 * ``action required'' if error happened in current execution context
249 */
250static int kill_proc(struct to_kill *tk, unsigned long pfn, int flags)
251{
252 struct task_struct *t = tk->tsk;
253 short addr_lsb = tk->size_shift;
254 int ret = 0;
255
256 pr_err("Memory failure: %#lx: Sending SIGBUS to %s:%d due to hardware memory corruption\n",
257 pfn, t->comm, t->pid);
258
259 if (flags & MF_ACTION_REQUIRED) {
260 if (t == current)
261 ret = force_sig_mceerr(BUS_MCEERR_AR,
262 (void __user *)tk->addr, addr_lsb);
263 else
264 /* Signal other processes sharing the page if they have PF_MCE_EARLY set. */
265 ret = send_sig_mceerr(BUS_MCEERR_AO, (void __user *)tk->addr,
266 addr_lsb, t);
267 } else {
268 /*
269 * Don't use force here, it's convenient if the signal
270 * can be temporarily blocked.
271 * This could cause a loop when the user sets SIGBUS
272 * to SIG_IGN, but hopefully no one will do that?
273 */
274 ret = send_sig_mceerr(BUS_MCEERR_AO, (void __user *)tk->addr,
275 addr_lsb, t); /* synchronous? */
276 }
277 if (ret < 0)
278 pr_info("Memory failure: Error sending signal to %s:%d: %d\n",
279 t->comm, t->pid, ret);
280 return ret;
281}
282
283/*
284 * Unknown page type encountered. Try to check whether it can turn PageLRU by
285 * lru_add_drain_all, or a free page by reclaiming slabs when possible.
286 */
287void shake_page(struct page *p, int access)
288{
289 if (PageHuge(p))
290 return;
291
292 if (!PageSlab(p)) {
293 lru_add_drain_all();
294 if (PageLRU(p) || is_free_buddy_page(p))
295 return;
296 }
297
298 /*
299 * Only call shrink_node_slabs here (which would also shrink
300 * other caches) if access is not potentially fatal.
301 */
302 if (access)
303 drop_slab_node(page_to_nid(p));
304}
305EXPORT_SYMBOL_GPL(shake_page);
306
307static unsigned long dev_pagemap_mapping_shift(struct page *page,
308 struct vm_area_struct *vma)
309{
310 unsigned long address = vma_address(page, vma);
311 pgd_t *pgd;
312 p4d_t *p4d;
313 pud_t *pud;
314 pmd_t *pmd;
315 pte_t *pte;
316
317 pgd = pgd_offset(vma->vm_mm, address);
318 if (!pgd_present(*pgd))
319 return 0;
320 p4d = p4d_offset(pgd, address);
321 if (!p4d_present(*p4d))
322 return 0;
323 pud = pud_offset(p4d, address);
324 if (!pud_present(*pud))
325 return 0;
326 if (pud_devmap(*pud))
327 return PUD_SHIFT;
328 pmd = pmd_offset(pud, address);
329 if (!pmd_present(*pmd))
330 return 0;
331 if (pmd_devmap(*pmd))
332 return PMD_SHIFT;
333 pte = pte_offset_map(pmd, address);
334 if (!pte_present(*pte))
335 return 0;
336 if (pte_devmap(*pte))
337 return PAGE_SHIFT;
338 return 0;
339}
340
341/*
342 * Failure handling: if we can't find or can't kill a process there's
343 * not much we can do. We just print a message and ignore otherwise.
344 */
345
346/*
347 * Schedule a process for later kill.
348 * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
349 */
350static void add_to_kill(struct task_struct *tsk, struct page *p,
351 struct vm_area_struct *vma,
352 struct list_head *to_kill)
353{
354 struct to_kill *tk;
355
356 tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
357 if (!tk) {
358 pr_err("Memory failure: Out of memory while machine check handling\n");
359 return;
360 }
361
362 tk->addr = page_address_in_vma(p, vma);
363 if (is_zone_device_page(p))
364 tk->size_shift = dev_pagemap_mapping_shift(p, vma);
365 else
366 tk->size_shift = page_shift(compound_head(p));
367
368 /*
369 * Send SIGKILL if "tk->addr == -EFAULT". Also, as
370 * "tk->size_shift" is always non-zero for !is_zone_device_page(),
371 * so "tk->size_shift == 0" effectively checks no mapping on
372 * ZONE_DEVICE. Indeed, when a devdax page is mmapped N times
373 * to a process' address space, it's possible not all N VMAs
374 * contain mappings for the page, but at least one VMA does.
375 * Only deliver SIGBUS with payload derived from the VMA that
376 * has a mapping for the page.
377 */
378 if (tk->addr == -EFAULT) {
379 pr_info("Memory failure: Unable to find user space address %lx in %s\n",
380 page_to_pfn(p), tsk->comm);
381 } else if (tk->size_shift == 0) {
382 kfree(tk);
383 return;
384 }
385
386 get_task_struct(tsk);
387 tk->tsk = tsk;
388 list_add_tail(&tk->nd, to_kill);
389}
390
391/*
392 * Kill the processes that have been collected earlier.
393 *
394 * Only do anything when DOIT is set, otherwise just free the list
395 * (this is used for clean pages which do not need killing)
396 * Also when FAIL is set do a force kill because something went
397 * wrong earlier.
398 */
399static void kill_procs(struct list_head *to_kill, int forcekill, bool fail,
400 unsigned long pfn, int flags)
401{
402 struct to_kill *tk, *next;
403
404 list_for_each_entry_safe (tk, next, to_kill, nd) {
405 if (forcekill) {
406 /*
407 * In case something went wrong with munmapping
408 * make sure the process doesn't catch the
409 * signal and then access the memory. Just kill it.
410 */
411 if (fail || tk->addr == -EFAULT) {
412 pr_err("Memory failure: %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n",
413 pfn, tk->tsk->comm, tk->tsk->pid);
414 do_send_sig_info(SIGKILL, SEND_SIG_PRIV,
415 tk->tsk, PIDTYPE_PID);
416 }
417
418 /*
419 * In theory the process could have mapped
420 * something else on the address in-between. We could
421 * check for that, but we need to tell the
422 * process anyways.
423 */
424 else if (kill_proc(tk, pfn, flags) < 0)
425 pr_err("Memory failure: %#lx: Cannot send advisory machine check signal to %s:%d\n",
426 pfn, tk->tsk->comm, tk->tsk->pid);
427 }
428 put_task_struct(tk->tsk);
429 kfree(tk);
430 }
431}
432
433/*
434 * Find a dedicated thread which is supposed to handle SIGBUS(BUS_MCEERR_AO)
435 * on behalf of the thread group. Return task_struct of the (first found)
436 * dedicated thread if found, and return NULL otherwise.
437 *
438 * We already hold read_lock(&tasklist_lock) in the caller, so we don't
439 * have to call rcu_read_lock/unlock() in this function.
440 */
441static struct task_struct *find_early_kill_thread(struct task_struct *tsk)
442{
443 struct task_struct *t;
444
445 for_each_thread(tsk, t) {
446 if (t->flags & PF_MCE_PROCESS) {
447 if (t->flags & PF_MCE_EARLY)
448 return t;
449 } else {
450 if (sysctl_memory_failure_early_kill)
451 return t;
452 }
453 }
454 return NULL;
455}
456
457/*
458 * Determine whether a given process is "early kill" process which expects
459 * to be signaled when some page under the process is hwpoisoned.
460 * Return task_struct of the dedicated thread (main thread unless explicitly
461 * specified) if the process is "early kill" and otherwise returns NULL.
462 *
463 * Note that the above is true for Action Optional case. For Action Required
464 * case, it's only meaningful to the current thread which need to be signaled
465 * with SIGBUS, this error is Action Optional for other non current
466 * processes sharing the same error page,if the process is "early kill", the
467 * task_struct of the dedicated thread will also be returned.
468 */
469static struct task_struct *task_early_kill(struct task_struct *tsk,
470 int force_early)
471{
472 if (!tsk->mm)
473 return NULL;
474 /*
475 * Comparing ->mm here because current task might represent
476 * a subthread, while tsk always points to the main thread.
477 */
478 if (force_early && tsk->mm == current->mm)
479 return current;
480
481 return find_early_kill_thread(tsk);
482}
483
484/*
485 * Collect processes when the error hit an anonymous page.
486 */
487static void collect_procs_anon(struct page *page, struct list_head *to_kill,
488 int force_early)
489{
490 struct vm_area_struct *vma;
491 struct task_struct *tsk;
492 struct anon_vma *av;
493 pgoff_t pgoff;
494
495 av = page_lock_anon_vma_read(page);
496 if (av == NULL) /* Not actually mapped anymore */
497 return;
498
499 pgoff = page_to_pgoff(page);
500 read_lock(&tasklist_lock);
501 for_each_process (tsk) {
502 struct anon_vma_chain *vmac;
503 struct task_struct *t = task_early_kill(tsk, force_early);
504
505 if (!t)
506 continue;
507 anon_vma_interval_tree_foreach(vmac, &av->rb_root,
508 pgoff, pgoff) {
509 vma = vmac->vma;
510 if (!page_mapped_in_vma(page, vma))
511 continue;
512 if (vma->vm_mm == t->mm)
513 add_to_kill(t, page, vma, to_kill);
514 }
515 }
516 read_unlock(&tasklist_lock);
517 page_unlock_anon_vma_read(av);
518}
519
520/*
521 * Collect processes when the error hit a file mapped page.
522 */
523static void collect_procs_file(struct page *page, struct list_head *to_kill,
524 int force_early)
525{
526 struct vm_area_struct *vma;
527 struct task_struct *tsk;
528 struct address_space *mapping = page->mapping;
529 pgoff_t pgoff;
530
531 i_mmap_lock_read(mapping);
532 read_lock(&tasklist_lock);
533 pgoff = page_to_pgoff(page);
534 for_each_process(tsk) {
535 struct task_struct *t = task_early_kill(tsk, force_early);
536
537 if (!t)
538 continue;
539 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff,
540 pgoff) {
541 /*
542 * Send early kill signal to tasks where a vma covers
543 * the page but the corrupted page is not necessarily
544 * mapped it in its pte.
545 * Assume applications who requested early kill want
546 * to be informed of all such data corruptions.
547 */
548 if (vma->vm_mm == t->mm)
549 add_to_kill(t, page, vma, to_kill);
550 }
551 }
552 read_unlock(&tasklist_lock);
553 i_mmap_unlock_read(mapping);
554}
555
556/*
557 * Collect the processes who have the corrupted page mapped to kill.
558 */
559static void collect_procs(struct page *page, struct list_head *tokill,
560 int force_early)
561{
562 if (!page->mapping)
563 return;
564
565 if (PageAnon(page))
566 collect_procs_anon(page, tokill, force_early);
567 else
568 collect_procs_file(page, tokill, force_early);
569}
570
571struct hwp_walk {
572 struct to_kill tk;
573 unsigned long pfn;
574 int flags;
575};
576
577static void set_to_kill(struct to_kill *tk, unsigned long addr, short shift)
578{
579 tk->addr = addr;
580 tk->size_shift = shift;
581}
582
583static int check_hwpoisoned_entry(pte_t pte, unsigned long addr, short shift,
584 unsigned long poisoned_pfn, struct to_kill *tk)
585{
586 unsigned long pfn = 0;
587
588 if (pte_present(pte)) {
589 pfn = pte_pfn(pte);
590 } else {
591 swp_entry_t swp = pte_to_swp_entry(pte);
592
593 if (is_hwpoison_entry(swp))
594 pfn = hwpoison_entry_to_pfn(swp);
595 }
596
597 if (!pfn || pfn != poisoned_pfn)
598 return 0;
599
600 set_to_kill(tk, addr, shift);
601 return 1;
602}
603
604#ifdef CONFIG_TRANSPARENT_HUGEPAGE
605static int check_hwpoisoned_pmd_entry(pmd_t *pmdp, unsigned long addr,
606 struct hwp_walk *hwp)
607{
608 pmd_t pmd = *pmdp;
609 unsigned long pfn;
610 unsigned long hwpoison_vaddr;
611
612 if (!pmd_present(pmd))
613 return 0;
614 pfn = pmd_pfn(pmd);
615 if (pfn <= hwp->pfn && hwp->pfn < pfn + HPAGE_PMD_NR) {
616 hwpoison_vaddr = addr + ((hwp->pfn - pfn) << PAGE_SHIFT);
617 set_to_kill(&hwp->tk, hwpoison_vaddr, PAGE_SHIFT);
618 return 1;
619 }
620 return 0;
621}
622#else
623static int check_hwpoisoned_pmd_entry(pmd_t *pmdp, unsigned long addr,
624 struct hwp_walk *hwp)
625{
626 return 0;
627}
628#endif
629
630static int hwpoison_pte_range(pmd_t *pmdp, unsigned long addr,
631 unsigned long end, struct mm_walk *walk)
632{
633 struct hwp_walk *hwp = (struct hwp_walk *)walk->private;
634 int ret = 0;
635 pte_t *ptep;
636 spinlock_t *ptl;
637
638 ptl = pmd_trans_huge_lock(pmdp, walk->vma);
639 if (ptl) {
640 ret = check_hwpoisoned_pmd_entry(pmdp, addr, hwp);
641 spin_unlock(ptl);
642 goto out;
643 }
644
645 if (pmd_trans_unstable(pmdp))
646 goto out;
647
648 ptep = pte_offset_map_lock(walk->vma->vm_mm, pmdp, addr, &ptl);
649 for (; addr != end; ptep++, addr += PAGE_SIZE) {
650 ret = check_hwpoisoned_entry(*ptep, addr, PAGE_SHIFT,
651 hwp->pfn, &hwp->tk);
652 if (ret == 1)
653 break;
654 }
655 pte_unmap_unlock(ptep - 1, ptl);
656out:
657 cond_resched();
658 return ret;
659}
660
661#ifdef CONFIG_HUGETLB_PAGE
662static int hwpoison_hugetlb_range(pte_t *ptep, unsigned long hmask,
663 unsigned long addr, unsigned long end,
664 struct mm_walk *walk)
665{
666 struct hwp_walk *hwp = (struct hwp_walk *)walk->private;
667 pte_t pte = huge_ptep_get(ptep);
668 struct hstate *h = hstate_vma(walk->vma);
669
670 return check_hwpoisoned_entry(pte, addr, huge_page_shift(h),
671 hwp->pfn, &hwp->tk);
672}
673#else
674#define hwpoison_hugetlb_range NULL
675#endif
676
677static struct mm_walk_ops hwp_walk_ops = {
678 .pmd_entry = hwpoison_pte_range,
679 .hugetlb_entry = hwpoison_hugetlb_range,
680};
681
682/*
683 * Sends SIGBUS to the current process with error info.
684 *
685 * This function is intended to handle "Action Required" MCEs on already
686 * hardware poisoned pages. They could happen, for example, when
687 * memory_failure() failed to unmap the error page at the first call, or
688 * when multiple local machine checks happened on different CPUs.
689 *
690 * MCE handler currently has no easy access to the error virtual address,
691 * so this function walks page table to find it. The returned virtual address
692 * is proper in most cases, but it could be wrong when the application
693 * process has multiple entries mapping the error page.
694 */
695static int kill_accessing_process(struct task_struct *p, unsigned long pfn,
696 int flags)
697{
698 int ret;
699 struct hwp_walk priv = {
700 .pfn = pfn,
701 };
702 priv.tk.tsk = p;
703
704 mmap_read_lock(p->mm);
705 ret = walk_page_range(p->mm, 0, TASK_SIZE, &hwp_walk_ops,
706 (void *)&priv);
707 if (ret == 1 && priv.tk.addr)
708 kill_proc(&priv.tk, pfn, flags);
709 mmap_read_unlock(p->mm);
710 return ret ? -EFAULT : -EHWPOISON;
711}
712
713static const char *action_name[] = {
714 [MF_IGNORED] = "Ignored",
715 [MF_FAILED] = "Failed",
716 [MF_DELAYED] = "Delayed",
717 [MF_RECOVERED] = "Recovered",
718};
719
720static const char * const action_page_types[] = {
721 [MF_MSG_KERNEL] = "reserved kernel page",
722 [MF_MSG_KERNEL_HIGH_ORDER] = "high-order kernel page",
723 [MF_MSG_SLAB] = "kernel slab page",
724 [MF_MSG_DIFFERENT_COMPOUND] = "different compound page after locking",
725 [MF_MSG_POISONED_HUGE] = "huge page already hardware poisoned",
726 [MF_MSG_HUGE] = "huge page",
727 [MF_MSG_FREE_HUGE] = "free huge page",
728 [MF_MSG_NON_PMD_HUGE] = "non-pmd-sized huge page",
729 [MF_MSG_UNMAP_FAILED] = "unmapping failed page",
730 [MF_MSG_DIRTY_SWAPCACHE] = "dirty swapcache page",
731 [MF_MSG_CLEAN_SWAPCACHE] = "clean swapcache page",
732 [MF_MSG_DIRTY_MLOCKED_LRU] = "dirty mlocked LRU page",
733 [MF_MSG_CLEAN_MLOCKED_LRU] = "clean mlocked LRU page",
734 [MF_MSG_DIRTY_UNEVICTABLE_LRU] = "dirty unevictable LRU page",
735 [MF_MSG_CLEAN_UNEVICTABLE_LRU] = "clean unevictable LRU page",
736 [MF_MSG_DIRTY_LRU] = "dirty LRU page",
737 [MF_MSG_CLEAN_LRU] = "clean LRU page",
738 [MF_MSG_TRUNCATED_LRU] = "already truncated LRU page",
739 [MF_MSG_BUDDY] = "free buddy page",
740 [MF_MSG_BUDDY_2ND] = "free buddy page (2nd try)",
741 [MF_MSG_DAX] = "dax page",
742 [MF_MSG_UNSPLIT_THP] = "unsplit thp",
743 [MF_MSG_UNKNOWN] = "unknown page",
744};
745
746/*
747 * XXX: It is possible that a page is isolated from LRU cache,
748 * and then kept in swap cache or failed to remove from page cache.
749 * The page count will stop it from being freed by unpoison.
750 * Stress tests should be aware of this memory leak problem.
751 */
752static int delete_from_lru_cache(struct page *p)
753{
754 if (!isolate_lru_page(p)) {
755 /*
756 * Clear sensible page flags, so that the buddy system won't
757 * complain when the page is unpoison-and-freed.
758 */
759 ClearPageActive(p);
760 ClearPageUnevictable(p);
761
762 /*
763 * Poisoned page might never drop its ref count to 0 so we have
764 * to uncharge it manually from its memcg.
765 */
766 mem_cgroup_uncharge(p);
767
768 /*
769 * drop the page count elevated by isolate_lru_page()
770 */
771 put_page(p);
772 return 0;
773 }
774 return -EIO;
775}
776
777static int truncate_error_page(struct page *p, unsigned long pfn,
778 struct address_space *mapping)
779{
780 int ret = MF_FAILED;
781
782 if (mapping->a_ops->error_remove_page) {
783 int err = mapping->a_ops->error_remove_page(mapping, p);
784
785 if (err != 0) {
786 pr_info("Memory failure: %#lx: Failed to punch page: %d\n",
787 pfn, err);
788 } else if (page_has_private(p) &&
789 !try_to_release_page(p, GFP_NOIO)) {
790 pr_info("Memory failure: %#lx: failed to release buffers\n",
791 pfn);
792 } else {
793 ret = MF_RECOVERED;
794 }
795 } else {
796 /*
797 * If the file system doesn't support it just invalidate
798 * This fails on dirty or anything with private pages
799 */
800 if (invalidate_inode_page(p))
801 ret = MF_RECOVERED;
802 else
803 pr_info("Memory failure: %#lx: Failed to invalidate\n",
804 pfn);
805 }
806
807 return ret;
808}
809
810/*
811 * Error hit kernel page.
812 * Do nothing, try to be lucky and not touch this instead. For a few cases we
813 * could be more sophisticated.
814 */
815static int me_kernel(struct page *p, unsigned long pfn)
816{
817 unlock_page(p);
818 return MF_IGNORED;
819}
820
821/*
822 * Page in unknown state. Do nothing.
823 */
824static int me_unknown(struct page *p, unsigned long pfn)
825{
826 pr_err("Memory failure: %#lx: Unknown page state\n", pfn);
827 unlock_page(p);
828 return MF_FAILED;
829}
830
831/*
832 * Clean (or cleaned) page cache page.
833 */
834static int me_pagecache_clean(struct page *p, unsigned long pfn)
835{
836 int ret;
837 struct address_space *mapping;
838
839 delete_from_lru_cache(p);
840
841 /*
842 * For anonymous pages we're done the only reference left
843 * should be the one m_f() holds.
844 */
845 if (PageAnon(p)) {
846 ret = MF_RECOVERED;
847 goto out;
848 }
849
850 /*
851 * Now truncate the page in the page cache. This is really
852 * more like a "temporary hole punch"
853 * Don't do this for block devices when someone else
854 * has a reference, because it could be file system metadata
855 * and that's not safe to truncate.
856 */
857 mapping = page_mapping(p);
858 if (!mapping) {
859 /*
860 * Page has been teared down in the meanwhile
861 */
862 ret = MF_FAILED;
863 goto out;
864 }
865
866 /*
867 * Truncation is a bit tricky. Enable it per file system for now.
868 *
869 * Open: to take i_mutex or not for this? Right now we don't.
870 */
871 ret = truncate_error_page(p, pfn, mapping);
872out:
873 unlock_page(p);
874 return ret;
875}
876
877/*
878 * Dirty pagecache page
879 * Issues: when the error hit a hole page the error is not properly
880 * propagated.
881 */
882static int me_pagecache_dirty(struct page *p, unsigned long pfn)
883{
884 struct address_space *mapping = page_mapping(p);
885
886 SetPageError(p);
887 /* TBD: print more information about the file. */
888 if (mapping) {
889 /*
890 * IO error will be reported by write(), fsync(), etc.
891 * who check the mapping.
892 * This way the application knows that something went
893 * wrong with its dirty file data.
894 *
895 * There's one open issue:
896 *
897 * The EIO will be only reported on the next IO
898 * operation and then cleared through the IO map.
899 * Normally Linux has two mechanisms to pass IO error
900 * first through the AS_EIO flag in the address space
901 * and then through the PageError flag in the page.
902 * Since we drop pages on memory failure handling the
903 * only mechanism open to use is through AS_AIO.
904 *
905 * This has the disadvantage that it gets cleared on
906 * the first operation that returns an error, while
907 * the PageError bit is more sticky and only cleared
908 * when the page is reread or dropped. If an
909 * application assumes it will always get error on
910 * fsync, but does other operations on the fd before
911 * and the page is dropped between then the error
912 * will not be properly reported.
913 *
914 * This can already happen even without hwpoisoned
915 * pages: first on metadata IO errors (which only
916 * report through AS_EIO) or when the page is dropped
917 * at the wrong time.
918 *
919 * So right now we assume that the application DTRT on
920 * the first EIO, but we're not worse than other parts
921 * of the kernel.
922 */
923 mapping_set_error(mapping, -EIO);
924 }
925
926 return me_pagecache_clean(p, pfn);
927}
928
929/*
930 * Clean and dirty swap cache.
931 *
932 * Dirty swap cache page is tricky to handle. The page could live both in page
933 * cache and swap cache(ie. page is freshly swapped in). So it could be
934 * referenced concurrently by 2 types of PTEs:
935 * normal PTEs and swap PTEs. We try to handle them consistently by calling
936 * try_to_unmap(TTU_IGNORE_HWPOISON) to convert the normal PTEs to swap PTEs,
937 * and then
938 * - clear dirty bit to prevent IO
939 * - remove from LRU
940 * - but keep in the swap cache, so that when we return to it on
941 * a later page fault, we know the application is accessing
942 * corrupted data and shall be killed (we installed simple
943 * interception code in do_swap_page to catch it).
944 *
945 * Clean swap cache pages can be directly isolated. A later page fault will
946 * bring in the known good data from disk.
947 */
948static int me_swapcache_dirty(struct page *p, unsigned long pfn)
949{
950 int ret;
951
952 ClearPageDirty(p);
953 /* Trigger EIO in shmem: */
954 ClearPageUptodate(p);
955
956 ret = delete_from_lru_cache(p) ? MF_FAILED : MF_DELAYED;
957 unlock_page(p);
958 return ret;
959}
960
961static int me_swapcache_clean(struct page *p, unsigned long pfn)
962{
963 int ret;
964
965 delete_from_swap_cache(p);
966
967 ret = delete_from_lru_cache(p) ? MF_FAILED : MF_RECOVERED;
968 unlock_page(p);
969 return ret;
970}
971
972/*
973 * Huge pages. Needs work.
974 * Issues:
975 * - Error on hugepage is contained in hugepage unit (not in raw page unit.)
976 * To narrow down kill region to one page, we need to break up pmd.
977 */
978static int me_huge_page(struct page *p, unsigned long pfn)
979{
980 int res;
981 struct page *hpage = compound_head(p);
982 struct address_space *mapping;
983
984 if (!PageHuge(hpage))
985 return MF_DELAYED;
986
987 mapping = page_mapping(hpage);
988 if (mapping) {
989 res = truncate_error_page(hpage, pfn, mapping);
990 unlock_page(hpage);
991 } else {
992 res = MF_FAILED;
993 unlock_page(hpage);
994 /*
995 * migration entry prevents later access on error anonymous
996 * hugepage, so we can free and dissolve it into buddy to
997 * save healthy subpages.
998 */
999 if (PageAnon(hpage))
1000 put_page(hpage);
1001 if (__page_handle_poison(p)) {
1002 page_ref_inc(p);
1003 res = MF_RECOVERED;
1004 }
1005 }
1006
1007 return res;
1008}
1009
1010/*
1011 * Various page states we can handle.
1012 *
1013 * A page state is defined by its current page->flags bits.
1014 * The table matches them in order and calls the right handler.
1015 *
1016 * This is quite tricky because we can access page at any time
1017 * in its live cycle, so all accesses have to be extremely careful.
1018 *
1019 * This is not complete. More states could be added.
1020 * For any missing state don't attempt recovery.
1021 */
1022
1023#define dirty (1UL << PG_dirty)
1024#define sc ((1UL << PG_swapcache) | (1UL << PG_swapbacked))
1025#define unevict (1UL << PG_unevictable)
1026#define mlock (1UL << PG_mlocked)
1027#define lru (1UL << PG_lru)
1028#define head (1UL << PG_head)
1029#define slab (1UL << PG_slab)
1030#define reserved (1UL << PG_reserved)
1031
1032static struct page_state {
1033 unsigned long mask;
1034 unsigned long res;
1035 enum mf_action_page_type type;
1036
1037 /* Callback ->action() has to unlock the relevant page inside it. */
1038 int (*action)(struct page *p, unsigned long pfn);
1039} error_states[] = {
1040 { reserved, reserved, MF_MSG_KERNEL, me_kernel },
1041 /*
1042 * free pages are specially detected outside this table:
1043 * PG_buddy pages only make a small fraction of all free pages.
1044 */
1045
1046 /*
1047 * Could in theory check if slab page is free or if we can drop
1048 * currently unused objects without touching them. But just
1049 * treat it as standard kernel for now.
1050 */
1051 { slab, slab, MF_MSG_SLAB, me_kernel },
1052
1053 { head, head, MF_MSG_HUGE, me_huge_page },
1054
1055 { sc|dirty, sc|dirty, MF_MSG_DIRTY_SWAPCACHE, me_swapcache_dirty },
1056 { sc|dirty, sc, MF_MSG_CLEAN_SWAPCACHE, me_swapcache_clean },
1057
1058 { mlock|dirty, mlock|dirty, MF_MSG_DIRTY_MLOCKED_LRU, me_pagecache_dirty },
1059 { mlock|dirty, mlock, MF_MSG_CLEAN_MLOCKED_LRU, me_pagecache_clean },
1060
1061 { unevict|dirty, unevict|dirty, MF_MSG_DIRTY_UNEVICTABLE_LRU, me_pagecache_dirty },
1062 { unevict|dirty, unevict, MF_MSG_CLEAN_UNEVICTABLE_LRU, me_pagecache_clean },
1063
1064 { lru|dirty, lru|dirty, MF_MSG_DIRTY_LRU, me_pagecache_dirty },
1065 { lru|dirty, lru, MF_MSG_CLEAN_LRU, me_pagecache_clean },
1066
1067 /*
1068 * Catchall entry: must be at end.
1069 */
1070 { 0, 0, MF_MSG_UNKNOWN, me_unknown },
1071};
1072
1073#undef dirty
1074#undef sc
1075#undef unevict
1076#undef mlock
1077#undef lru
1078#undef head
1079#undef slab
1080#undef reserved
1081
1082/*
1083 * "Dirty/Clean" indication is not 100% accurate due to the possibility of
1084 * setting PG_dirty outside page lock. See also comment above set_page_dirty().
1085 */
1086static void action_result(unsigned long pfn, enum mf_action_page_type type,
1087 enum mf_result result)
1088{
1089 trace_memory_failure_event(pfn, type, result);
1090
1091 pr_err("Memory failure: %#lx: recovery action for %s: %s\n",
1092 pfn, action_page_types[type], action_name[result]);
1093}
1094
1095static int page_action(struct page_state *ps, struct page *p,
1096 unsigned long pfn)
1097{
1098 int result;
1099 int count;
1100
1101 /* page p should be unlocked after returning from ps->action(). */
1102 result = ps->action(p, pfn);
1103
1104 count = page_count(p) - 1;
1105 if (ps->action == me_swapcache_dirty && result == MF_DELAYED)
1106 count--;
1107 if (count > 0) {
1108 pr_err("Memory failure: %#lx: %s still referenced by %d users\n",
1109 pfn, action_page_types[ps->type], count);
1110 result = MF_FAILED;
1111 }
1112 action_result(pfn, ps->type, result);
1113
1114 /* Could do more checks here if page looks ok */
1115 /*
1116 * Could adjust zone counters here to correct for the missing page.
1117 */
1118
1119 return (result == MF_RECOVERED || result == MF_DELAYED) ? 0 : -EBUSY;
1120}
1121
1122/*
1123 * Return true if a page type of a given page is supported by hwpoison
1124 * mechanism (while handling could fail), otherwise false. This function
1125 * does not return true for hugetlb or device memory pages, so it's assumed
1126 * to be called only in the context where we never have such pages.
1127 */
1128static inline bool HWPoisonHandlable(struct page *page)
1129{
1130 return PageLRU(page) || __PageMovable(page) || is_free_buddy_page(page);
1131}
1132
1133static int __get_hwpoison_page(struct page *page)
1134{
1135 struct page *head = compound_head(page);
1136 int ret = 0;
1137 bool hugetlb = false;
1138
1139 ret = get_hwpoison_huge_page(head, &hugetlb);
1140 if (hugetlb)
1141 return ret;
1142
1143 /*
1144 * This check prevents from calling get_hwpoison_unless_zero()
1145 * for any unsupported type of page in order to reduce the risk of
1146 * unexpected races caused by taking a page refcount.
1147 */
1148 if (!HWPoisonHandlable(head))
1149 return -EBUSY;
1150
1151 if (PageTransHuge(head)) {
1152 /*
1153 * Non anonymous thp exists only in allocation/free time. We
1154 * can't handle such a case correctly, so let's give it up.
1155 * This should be better than triggering BUG_ON when kernel
1156 * tries to touch the "partially handled" page.
1157 */
1158 if (!PageAnon(head)) {
1159 pr_err("Memory failure: %#lx: non anonymous thp\n",
1160 page_to_pfn(page));
1161 return 0;
1162 }
1163 }
1164
1165 if (get_page_unless_zero(head)) {
1166 if (head == compound_head(page))
1167 return 1;
1168
1169 pr_info("Memory failure: %#lx cannot catch tail\n",
1170 page_to_pfn(page));
1171 put_page(head);
1172 }
1173
1174 return 0;
1175}
1176
1177static int get_any_page(struct page *p, unsigned long flags)
1178{
1179 int ret = 0, pass = 0;
1180 bool count_increased = false;
1181
1182 if (flags & MF_COUNT_INCREASED)
1183 count_increased = true;
1184
1185try_again:
1186 if (!count_increased) {
1187 ret = __get_hwpoison_page(p);
1188 if (!ret) {
1189 if (page_count(p)) {
1190 /* We raced with an allocation, retry. */
1191 if (pass++ < 3)
1192 goto try_again;
1193 ret = -EBUSY;
1194 } else if (!PageHuge(p) && !is_free_buddy_page(p)) {
1195 /* We raced with put_page, retry. */
1196 if (pass++ < 3)
1197 goto try_again;
1198 ret = -EIO;
1199 }
1200 goto out;
1201 } else if (ret == -EBUSY) {
1202 /*
1203 * We raced with (possibly temporary) unhandlable
1204 * page, retry.
1205 */
1206 if (pass++ < 3) {
1207 shake_page(p, 1);
1208 goto try_again;
1209 }
1210 ret = -EIO;
1211 goto out;
1212 }
1213 }
1214
1215 if (PageHuge(p) || HWPoisonHandlable(p)) {
1216 ret = 1;
1217 } else {
1218 /*
1219 * A page we cannot handle. Check whether we can turn
1220 * it into something we can handle.
1221 */
1222 if (pass++ < 3) {
1223 put_page(p);
1224 shake_page(p, 1);
1225 count_increased = false;
1226 goto try_again;
1227 }
1228 put_page(p);
1229 ret = -EIO;
1230 }
1231out:
1232 return ret;
1233}
1234
1235/**
1236 * get_hwpoison_page() - Get refcount for memory error handling
1237 * @p: Raw error page (hit by memory error)
1238 * @flags: Flags controlling behavior of error handling
1239 *
1240 * get_hwpoison_page() takes a page refcount of an error page to handle memory
1241 * error on it, after checking that the error page is in a well-defined state
1242 * (defined as a page-type we can successfully handle the memor error on it,
1243 * such as LRU page and hugetlb page).
1244 *
1245 * Memory error handling could be triggered at any time on any type of page,
1246 * so it's prone to race with typical memory management lifecycle (like
1247 * allocation and free). So to avoid such races, get_hwpoison_page() takes
1248 * extra care for the error page's state (as done in __get_hwpoison_page()),
1249 * and has some retry logic in get_any_page().
1250 *
1251 * Return: 0 on failure,
1252 * 1 on success for in-use pages in a well-defined state,
1253 * -EIO for pages on which we can not handle memory errors,
1254 * -EBUSY when get_hwpoison_page() has raced with page lifecycle
1255 * operations like allocation and free.
1256 */
1257static int get_hwpoison_page(struct page *p, unsigned long flags)
1258{
1259 int ret;
1260
1261 zone_pcp_disable(page_zone(p));
1262 ret = get_any_page(p, flags);
1263 zone_pcp_enable(page_zone(p));
1264
1265 return ret;
1266}
1267
1268/*
1269 * Do all that is necessary to remove user space mappings. Unmap
1270 * the pages and send SIGBUS to the processes if the data was dirty.
1271 */
1272static bool hwpoison_user_mappings(struct page *p, unsigned long pfn,
1273 int flags, struct page **hpagep)
1274{
1275 enum ttu_flags ttu = TTU_IGNORE_MLOCK | TTU_SYNC;
1276 struct address_space *mapping;
1277 LIST_HEAD(tokill);
1278 bool unmap_success;
1279 int kill = 1, forcekill;
1280 struct page *hpage = *hpagep;
1281 bool mlocked = PageMlocked(hpage);
1282
1283 /*
1284 * Here we are interested only in user-mapped pages, so skip any
1285 * other types of pages.
1286 */
1287 if (PageReserved(p) || PageSlab(p))
1288 return true;
1289 if (!(PageLRU(hpage) || PageHuge(p)))
1290 return true;
1291
1292 /*
1293 * This check implies we don't kill processes if their pages
1294 * are in the swap cache early. Those are always late kills.
1295 */
1296 if (!page_mapped(hpage))
1297 return true;
1298
1299 if (PageKsm(p)) {
1300 pr_err("Memory failure: %#lx: can't handle KSM pages.\n", pfn);
1301 return false;
1302 }
1303
1304 if (PageSwapCache(p)) {
1305 pr_err("Memory failure: %#lx: keeping poisoned page in swap cache\n",
1306 pfn);
1307 ttu |= TTU_IGNORE_HWPOISON;
1308 }
1309
1310 /*
1311 * Propagate the dirty bit from PTEs to struct page first, because we
1312 * need this to decide if we should kill or just drop the page.
1313 * XXX: the dirty test could be racy: set_page_dirty() may not always
1314 * be called inside page lock (it's recommended but not enforced).
1315 */
1316 mapping = page_mapping(hpage);
1317 if (!(flags & MF_MUST_KILL) && !PageDirty(hpage) && mapping &&
1318 mapping_can_writeback(mapping)) {
1319 if (page_mkclean(hpage)) {
1320 SetPageDirty(hpage);
1321 } else {
1322 kill = 0;
1323 ttu |= TTU_IGNORE_HWPOISON;
1324 pr_info("Memory failure: %#lx: corrupted page was clean: dropped without side effects\n",
1325 pfn);
1326 }
1327 }
1328
1329 /*
1330 * First collect all the processes that have the page
1331 * mapped in dirty form. This has to be done before try_to_unmap,
1332 * because ttu takes the rmap data structures down.
1333 *
1334 * Error handling: We ignore errors here because
1335 * there's nothing that can be done.
1336 */
1337 if (kill)
1338 collect_procs(hpage, &tokill, flags & MF_ACTION_REQUIRED);
1339
1340 if (!PageHuge(hpage)) {
1341 try_to_unmap(hpage, ttu);
1342 } else {
1343 if (!PageAnon(hpage)) {
1344 /*
1345 * For hugetlb pages in shared mappings, try_to_unmap
1346 * could potentially call huge_pmd_unshare. Because of
1347 * this, take semaphore in write mode here and set
1348 * TTU_RMAP_LOCKED to indicate we have taken the lock
1349 * at this higher level.
1350 */
1351 mapping = hugetlb_page_mapping_lock_write(hpage);
1352 if (mapping) {
1353 try_to_unmap(hpage, ttu|TTU_RMAP_LOCKED);
1354 i_mmap_unlock_write(mapping);
1355 } else
1356 pr_info("Memory failure: %#lx: could not lock mapping for mapped huge page\n", pfn);
1357 } else {
1358 try_to_unmap(hpage, ttu);
1359 }
1360 }
1361
1362 unmap_success = !page_mapped(hpage);
1363 if (!unmap_success)
1364 pr_err("Memory failure: %#lx: failed to unmap page (mapcount=%d)\n",
1365 pfn, page_mapcount(hpage));
1366
1367 /*
1368 * try_to_unmap() might put mlocked page in lru cache, so call
1369 * shake_page() again to ensure that it's flushed.
1370 */
1371 if (mlocked)
1372 shake_page(hpage, 0);
1373
1374 /*
1375 * Now that the dirty bit has been propagated to the
1376 * struct page and all unmaps done we can decide if
1377 * killing is needed or not. Only kill when the page
1378 * was dirty or the process is not restartable,
1379 * otherwise the tokill list is merely
1380 * freed. When there was a problem unmapping earlier
1381 * use a more force-full uncatchable kill to prevent
1382 * any accesses to the poisoned memory.
1383 */
1384 forcekill = PageDirty(hpage) || (flags & MF_MUST_KILL);
1385 kill_procs(&tokill, forcekill, !unmap_success, pfn, flags);
1386
1387 return unmap_success;
1388}
1389
1390static int identify_page_state(unsigned long pfn, struct page *p,
1391 unsigned long page_flags)
1392{
1393 struct page_state *ps;
1394
1395 /*
1396 * The first check uses the current page flags which may not have any
1397 * relevant information. The second check with the saved page flags is
1398 * carried out only if the first check can't determine the page status.
1399 */
1400 for (ps = error_states;; ps++)
1401 if ((p->flags & ps->mask) == ps->res)
1402 break;
1403
1404 page_flags |= (p->flags & (1UL << PG_dirty));
1405
1406 if (!ps->mask)
1407 for (ps = error_states;; ps++)
1408 if ((page_flags & ps->mask) == ps->res)
1409 break;
1410 return page_action(ps, p, pfn);
1411}
1412
1413static int try_to_split_thp_page(struct page *page, const char *msg)
1414{
1415 lock_page(page);
1416 if (!PageAnon(page) || unlikely(split_huge_page(page))) {
1417 unsigned long pfn = page_to_pfn(page);
1418
1419 unlock_page(page);
1420 if (!PageAnon(page))
1421 pr_info("%s: %#lx: non anonymous thp\n", msg, pfn);
1422 else
1423 pr_info("%s: %#lx: thp split failed\n", msg, pfn);
1424 put_page(page);
1425 return -EBUSY;
1426 }
1427 unlock_page(page);
1428
1429 return 0;
1430}
1431
1432static int memory_failure_hugetlb(unsigned long pfn, int flags)
1433{
1434 struct page *p = pfn_to_page(pfn);
1435 struct page *head = compound_head(p);
1436 int res;
1437 unsigned long page_flags;
1438
1439 if (TestSetPageHWPoison(head)) {
1440 pr_err("Memory failure: %#lx: already hardware poisoned\n",
1441 pfn);
1442 res = -EHWPOISON;
1443 if (flags & MF_ACTION_REQUIRED)
1444 res = kill_accessing_process(current, page_to_pfn(head), flags);
1445 return res;
1446 }
1447
1448 num_poisoned_pages_inc();
1449
1450 if (!(flags & MF_COUNT_INCREASED)) {
1451 res = get_hwpoison_page(p, flags);
1452 if (!res) {
1453 /*
1454 * Check "filter hit" and "race with other subpage."
1455 */
1456 lock_page(head);
1457 if (PageHWPoison(head)) {
1458 if ((hwpoison_filter(p) && TestClearPageHWPoison(p))
1459 || (p != head && TestSetPageHWPoison(head))) {
1460 num_poisoned_pages_dec();
1461 unlock_page(head);
1462 return 0;
1463 }
1464 }
1465 unlock_page(head);
1466 res = MF_FAILED;
1467 if (__page_handle_poison(p)) {
1468 page_ref_inc(p);
1469 res = MF_RECOVERED;
1470 }
1471 action_result(pfn, MF_MSG_FREE_HUGE, res);
1472 return res == MF_RECOVERED ? 0 : -EBUSY;
1473 } else if (res < 0) {
1474 action_result(pfn, MF_MSG_UNKNOWN, MF_IGNORED);
1475 return -EBUSY;
1476 }
1477 }
1478
1479 lock_page(head);
1480 page_flags = head->flags;
1481
1482 if (!PageHWPoison(head)) {
1483 pr_err("Memory failure: %#lx: just unpoisoned\n", pfn);
1484 num_poisoned_pages_dec();
1485 unlock_page(head);
1486 put_page(head);
1487 return 0;
1488 }
1489
1490 /*
1491 * TODO: hwpoison for pud-sized hugetlb doesn't work right now, so
1492 * simply disable it. In order to make it work properly, we need
1493 * make sure that:
1494 * - conversion of a pud that maps an error hugetlb into hwpoison
1495 * entry properly works, and
1496 * - other mm code walking over page table is aware of pud-aligned
1497 * hwpoison entries.
1498 */
1499 if (huge_page_size(page_hstate(head)) > PMD_SIZE) {
1500 action_result(pfn, MF_MSG_NON_PMD_HUGE, MF_IGNORED);
1501 res = -EBUSY;
1502 goto out;
1503 }
1504
1505 if (!hwpoison_user_mappings(p, pfn, flags, &head)) {
1506 action_result(pfn, MF_MSG_UNMAP_FAILED, MF_IGNORED);
1507 res = -EBUSY;
1508 goto out;
1509 }
1510
1511 return identify_page_state(pfn, p, page_flags);
1512out:
1513 unlock_page(head);
1514 return res;
1515}
1516
1517static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
1518 struct dev_pagemap *pgmap)
1519{
1520 struct page *page = pfn_to_page(pfn);
1521 const bool unmap_success = true;
1522 unsigned long size = 0;
1523 struct to_kill *tk;
1524 LIST_HEAD(tokill);
1525 int rc = -EBUSY;
1526 loff_t start;
1527 dax_entry_t cookie;
1528
1529 if (flags & MF_COUNT_INCREASED)
1530 /*
1531 * Drop the extra refcount in case we come from madvise().
1532 */
1533 put_page(page);
1534
1535 /* device metadata space is not recoverable */
1536 if (!pgmap_pfn_valid(pgmap, pfn)) {
1537 rc = -ENXIO;
1538 goto out;
1539 }
1540
1541 /*
1542 * Prevent the inode from being freed while we are interrogating
1543 * the address_space, typically this would be handled by
1544 * lock_page(), but dax pages do not use the page lock. This
1545 * also prevents changes to the mapping of this pfn until
1546 * poison signaling is complete.
1547 */
1548 cookie = dax_lock_page(page);
1549 if (!cookie)
1550 goto out;
1551
1552 if (hwpoison_filter(page)) {
1553 rc = 0;
1554 goto unlock;
1555 }
1556
1557 if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
1558 /*
1559 * TODO: Handle HMM pages which may need coordination
1560 * with device-side memory.
1561 */
1562 goto unlock;
1563 }
1564
1565 /*
1566 * Use this flag as an indication that the dax page has been
1567 * remapped UC to prevent speculative consumption of poison.
1568 */
1569 SetPageHWPoison(page);
1570
1571 /*
1572 * Unlike System-RAM there is no possibility to swap in a
1573 * different physical page at a given virtual address, so all
1574 * userspace consumption of ZONE_DEVICE memory necessitates
1575 * SIGBUS (i.e. MF_MUST_KILL)
1576 */
1577 flags |= MF_ACTION_REQUIRED | MF_MUST_KILL;
1578 collect_procs(page, &tokill, flags & MF_ACTION_REQUIRED);
1579
1580 list_for_each_entry(tk, &tokill, nd)
1581 if (tk->size_shift)
1582 size = max(size, 1UL << tk->size_shift);
1583 if (size) {
1584 /*
1585 * Unmap the largest mapping to avoid breaking up
1586 * device-dax mappings which are constant size. The
1587 * actual size of the mapping being torn down is
1588 * communicated in siginfo, see kill_proc()
1589 */
1590 start = (page->index << PAGE_SHIFT) & ~(size - 1);
1591 unmap_mapping_range(page->mapping, start, size, 0);
1592 }
1593 kill_procs(&tokill, flags & MF_MUST_KILL, !unmap_success, pfn, flags);
1594 rc = 0;
1595unlock:
1596 dax_unlock_page(page, cookie);
1597out:
1598 /* drop pgmap ref acquired in caller */
1599 put_dev_pagemap(pgmap);
1600 action_result(pfn, MF_MSG_DAX, rc ? MF_FAILED : MF_RECOVERED);
1601 return rc;
1602}
1603
1604/**
1605 * memory_failure - Handle memory failure of a page.
1606 * @pfn: Page Number of the corrupted page
1607 * @flags: fine tune action taken
1608 *
1609 * This function is called by the low level machine check code
1610 * of an architecture when it detects hardware memory corruption
1611 * of a page. It tries its best to recover, which includes
1612 * dropping pages, killing processes etc.
1613 *
1614 * The function is primarily of use for corruptions that
1615 * happen outside the current execution context (e.g. when
1616 * detected by a background scrubber)
1617 *
1618 * Must run in process context (e.g. a work queue) with interrupts
1619 * enabled and no spinlocks hold.
1620 */
1621int memory_failure(unsigned long pfn, int flags)
1622{
1623 struct page *p;
1624 struct page *hpage;
1625 struct page *orig_head;
1626 struct dev_pagemap *pgmap;
1627 int res = 0;
1628 unsigned long page_flags;
1629 bool retry = true;
1630 static DEFINE_MUTEX(mf_mutex);
1631
1632 if (!sysctl_memory_failure_recovery)
1633 panic("Memory failure on page %lx", pfn);
1634
1635 p = pfn_to_online_page(pfn);
1636 if (!p) {
1637 if (pfn_valid(pfn)) {
1638 pgmap = get_dev_pagemap(pfn, NULL);
1639 if (pgmap)
1640 return memory_failure_dev_pagemap(pfn, flags,
1641 pgmap);
1642 }
1643 pr_err("Memory failure: %#lx: memory outside kernel control\n",
1644 pfn);
1645 return -ENXIO;
1646 }
1647
1648 mutex_lock(&mf_mutex);
1649
1650try_again:
1651 if (PageHuge(p)) {
1652 res = memory_failure_hugetlb(pfn, flags);
1653 goto unlock_mutex;
1654 }
1655
1656 if (TestSetPageHWPoison(p)) {
1657 pr_err("Memory failure: %#lx: already hardware poisoned\n",
1658 pfn);
1659 res = -EHWPOISON;
1660 if (flags & MF_ACTION_REQUIRED)
1661 res = kill_accessing_process(current, pfn, flags);
1662 goto unlock_mutex;
1663 }
1664
1665 orig_head = hpage = compound_head(p);
1666 num_poisoned_pages_inc();
1667
1668 /*
1669 * We need/can do nothing about count=0 pages.
1670 * 1) it's a free page, and therefore in safe hand:
1671 * prep_new_page() will be the gate keeper.
1672 * 2) it's part of a non-compound high order page.
1673 * Implies some kernel user: cannot stop them from
1674 * R/W the page; let's pray that the page has been
1675 * used and will be freed some time later.
1676 * In fact it's dangerous to directly bump up page count from 0,
1677 * that may make page_ref_freeze()/page_ref_unfreeze() mismatch.
1678 */
1679 if (!(flags & MF_COUNT_INCREASED)) {
1680 res = get_hwpoison_page(p, flags);
1681 if (!res) {
1682 if (is_free_buddy_page(p)) {
1683 if (take_page_off_buddy(p)) {
1684 page_ref_inc(p);
1685 res = MF_RECOVERED;
1686 } else {
1687 /* We lost the race, try again */
1688 if (retry) {
1689 ClearPageHWPoison(p);
1690 num_poisoned_pages_dec();
1691 retry = false;
1692 goto try_again;
1693 }
1694 res = MF_FAILED;
1695 }
1696 action_result(pfn, MF_MSG_BUDDY, res);
1697 res = res == MF_RECOVERED ? 0 : -EBUSY;
1698 } else {
1699 action_result(pfn, MF_MSG_KERNEL_HIGH_ORDER, MF_IGNORED);
1700 res = -EBUSY;
1701 }
1702 goto unlock_mutex;
1703 } else if (res < 0) {
1704 action_result(pfn, MF_MSG_UNKNOWN, MF_IGNORED);
1705 res = -EBUSY;
1706 goto unlock_mutex;
1707 }
1708 }
1709
1710 if (PageTransHuge(hpage)) {
1711 if (try_to_split_thp_page(p, "Memory Failure") < 0) {
1712 action_result(pfn, MF_MSG_UNSPLIT_THP, MF_IGNORED);
1713 res = -EBUSY;
1714 goto unlock_mutex;
1715 }
1716 VM_BUG_ON_PAGE(!page_count(p), p);
1717 }
1718
1719 /*
1720 * We ignore non-LRU pages for good reasons.
1721 * - PG_locked is only well defined for LRU pages and a few others
1722 * - to avoid races with __SetPageLocked()
1723 * - to avoid races with __SetPageSlab*() (and more non-atomic ops)
1724 * The check (unnecessarily) ignores LRU pages being isolated and
1725 * walked by the page reclaim code, however that's not a big loss.
1726 */
1727 shake_page(p, 0);
1728
1729 lock_page(p);
1730
1731 /*
1732 * The page could have changed compound pages during the locking.
1733 * If this happens just bail out.
1734 */
1735 if (PageCompound(p) && compound_head(p) != orig_head) {
1736 action_result(pfn, MF_MSG_DIFFERENT_COMPOUND, MF_IGNORED);
1737 res = -EBUSY;
1738 goto unlock_page;
1739 }
1740
1741 /*
1742 * We use page flags to determine what action should be taken, but
1743 * the flags can be modified by the error containment action. One
1744 * example is an mlocked page, where PG_mlocked is cleared by
1745 * page_remove_rmap() in try_to_unmap_one(). So to determine page status
1746 * correctly, we save a copy of the page flags at this time.
1747 */
1748 page_flags = p->flags;
1749
1750 /*
1751 * unpoison always clear PG_hwpoison inside page lock
1752 */
1753 if (!PageHWPoison(p)) {
1754 pr_err("Memory failure: %#lx: just unpoisoned\n", pfn);
1755 num_poisoned_pages_dec();
1756 unlock_page(p);
1757 put_page(p);
1758 goto unlock_mutex;
1759 }
1760 if (hwpoison_filter(p)) {
1761 if (TestClearPageHWPoison(p))
1762 num_poisoned_pages_dec();
1763 unlock_page(p);
1764 put_page(p);
1765 goto unlock_mutex;
1766 }
1767
1768 /*
1769 * __munlock_pagevec may clear a writeback page's LRU flag without
1770 * page_lock. We need wait writeback completion for this page or it
1771 * may trigger vfs BUG while evict inode.
1772 */
1773 if (!PageTransTail(p) && !PageLRU(p) && !PageWriteback(p))
1774 goto identify_page_state;
1775
1776 /*
1777 * It's very difficult to mess with pages currently under IO
1778 * and in many cases impossible, so we just avoid it here.
1779 */
1780 wait_on_page_writeback(p);
1781
1782 /*
1783 * Now take care of user space mappings.
1784 * Abort on fail: __delete_from_page_cache() assumes unmapped page.
1785 */
1786 if (!hwpoison_user_mappings(p, pfn, flags, &p)) {
1787 action_result(pfn, MF_MSG_UNMAP_FAILED, MF_IGNORED);
1788 res = -EBUSY;
1789 goto unlock_page;
1790 }
1791
1792 /*
1793 * Torn down by someone else?
1794 */
1795 if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) {
1796 action_result(pfn, MF_MSG_TRUNCATED_LRU, MF_IGNORED);
1797 res = -EBUSY;
1798 goto unlock_page;
1799 }
1800
1801identify_page_state:
1802 res = identify_page_state(pfn, p, page_flags);
1803 mutex_unlock(&mf_mutex);
1804 return res;
1805unlock_page:
1806 unlock_page(p);
1807unlock_mutex:
1808 mutex_unlock(&mf_mutex);
1809 return res;
1810}
1811EXPORT_SYMBOL_GPL(memory_failure);
1812
1813#define MEMORY_FAILURE_FIFO_ORDER 4
1814#define MEMORY_FAILURE_FIFO_SIZE (1 << MEMORY_FAILURE_FIFO_ORDER)
1815
1816struct memory_failure_entry {
1817 unsigned long pfn;
1818 int flags;
1819};
1820
1821struct memory_failure_cpu {
1822 DECLARE_KFIFO(fifo, struct memory_failure_entry,
1823 MEMORY_FAILURE_FIFO_SIZE);
1824 spinlock_t lock;
1825 struct work_struct work;
1826};
1827
1828static DEFINE_PER_CPU(struct memory_failure_cpu, memory_failure_cpu);
1829
1830/**
1831 * memory_failure_queue - Schedule handling memory failure of a page.
1832 * @pfn: Page Number of the corrupted page
1833 * @flags: Flags for memory failure handling
1834 *
1835 * This function is called by the low level hardware error handler
1836 * when it detects hardware memory corruption of a page. It schedules
1837 * the recovering of error page, including dropping pages, killing
1838 * processes etc.
1839 *
1840 * The function is primarily of use for corruptions that
1841 * happen outside the current execution context (e.g. when
1842 * detected by a background scrubber)
1843 *
1844 * Can run in IRQ context.
1845 */
1846void memory_failure_queue(unsigned long pfn, int flags)
1847{
1848 struct memory_failure_cpu *mf_cpu;
1849 unsigned long proc_flags;
1850 struct memory_failure_entry entry = {
1851 .pfn = pfn,
1852 .flags = flags,
1853 };
1854
1855 mf_cpu = &get_cpu_var(memory_failure_cpu);
1856 spin_lock_irqsave(&mf_cpu->lock, proc_flags);
1857 if (kfifo_put(&mf_cpu->fifo, entry))
1858 schedule_work_on(smp_processor_id(), &mf_cpu->work);
1859 else
1860 pr_err("Memory failure: buffer overflow when queuing memory failure at %#lx\n",
1861 pfn);
1862 spin_unlock_irqrestore(&mf_cpu->lock, proc_flags);
1863 put_cpu_var(memory_failure_cpu);
1864}
1865EXPORT_SYMBOL_GPL(memory_failure_queue);
1866
1867static void memory_failure_work_func(struct work_struct *work)
1868{
1869 struct memory_failure_cpu *mf_cpu;
1870 struct memory_failure_entry entry = { 0, };
1871 unsigned long proc_flags;
1872 int gotten;
1873
1874 mf_cpu = container_of(work, struct memory_failure_cpu, work);
1875 for (;;) {
1876 spin_lock_irqsave(&mf_cpu->lock, proc_flags);
1877 gotten = kfifo_get(&mf_cpu->fifo, &entry);
1878 spin_unlock_irqrestore(&mf_cpu->lock, proc_flags);
1879 if (!gotten)
1880 break;
1881 if (entry.flags & MF_SOFT_OFFLINE)
1882 soft_offline_page(entry.pfn, entry.flags);
1883 else
1884 memory_failure(entry.pfn, entry.flags);
1885 }
1886}
1887
1888/*
1889 * Process memory_failure work queued on the specified CPU.
1890 * Used to avoid return-to-userspace racing with the memory_failure workqueue.
1891 */
1892void memory_failure_queue_kick(int cpu)
1893{
1894 struct memory_failure_cpu *mf_cpu;
1895
1896 mf_cpu = &per_cpu(memory_failure_cpu, cpu);
1897 cancel_work_sync(&mf_cpu->work);
1898 memory_failure_work_func(&mf_cpu->work);
1899}
1900
1901static int __init memory_failure_init(void)
1902{
1903 struct memory_failure_cpu *mf_cpu;
1904 int cpu;
1905
1906 for_each_possible_cpu(cpu) {
1907 mf_cpu = &per_cpu(memory_failure_cpu, cpu);
1908 spin_lock_init(&mf_cpu->lock);
1909 INIT_KFIFO(mf_cpu->fifo);
1910 INIT_WORK(&mf_cpu->work, memory_failure_work_func);
1911 }
1912
1913 return 0;
1914}
1915core_initcall(memory_failure_init);
1916
1917#define unpoison_pr_info(fmt, pfn, rs) \
1918({ \
1919 if (__ratelimit(rs)) \
1920 pr_info(fmt, pfn); \
1921})
1922
1923/**
1924 * unpoison_memory - Unpoison a previously poisoned page
1925 * @pfn: Page number of the to be unpoisoned page
1926 *
1927 * Software-unpoison a page that has been poisoned by
1928 * memory_failure() earlier.
1929 *
1930 * This is only done on the software-level, so it only works
1931 * for linux injected failures, not real hardware failures
1932 *
1933 * Returns 0 for success, otherwise -errno.
1934 */
1935int unpoison_memory(unsigned long pfn)
1936{
1937 struct page *page;
1938 struct page *p;
1939 int freeit = 0;
1940 unsigned long flags = 0;
1941 static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL,
1942 DEFAULT_RATELIMIT_BURST);
1943
1944 if (!pfn_valid(pfn))
1945 return -ENXIO;
1946
1947 p = pfn_to_page(pfn);
1948 page = compound_head(p);
1949
1950 if (!PageHWPoison(p)) {
1951 unpoison_pr_info("Unpoison: Page was already unpoisoned %#lx\n",
1952 pfn, &unpoison_rs);
1953 return 0;
1954 }
1955
1956 if (page_count(page) > 1) {
1957 unpoison_pr_info("Unpoison: Someone grabs the hwpoison page %#lx\n",
1958 pfn, &unpoison_rs);
1959 return 0;
1960 }
1961
1962 if (page_mapped(page)) {
1963 unpoison_pr_info("Unpoison: Someone maps the hwpoison page %#lx\n",
1964 pfn, &unpoison_rs);
1965 return 0;
1966 }
1967
1968 if (page_mapping(page)) {
1969 unpoison_pr_info("Unpoison: the hwpoison page has non-NULL mapping %#lx\n",
1970 pfn, &unpoison_rs);
1971 return 0;
1972 }
1973
1974 /*
1975 * unpoison_memory() can encounter thp only when the thp is being
1976 * worked by memory_failure() and the page lock is not held yet.
1977 * In such case, we yield to memory_failure() and make unpoison fail.
1978 */
1979 if (!PageHuge(page) && PageTransHuge(page)) {
1980 unpoison_pr_info("Unpoison: Memory failure is now running on %#lx\n",
1981 pfn, &unpoison_rs);
1982 return 0;
1983 }
1984
1985 if (!get_hwpoison_page(p, flags)) {
1986 if (TestClearPageHWPoison(p))
1987 num_poisoned_pages_dec();
1988 unpoison_pr_info("Unpoison: Software-unpoisoned free page %#lx\n",
1989 pfn, &unpoison_rs);
1990 return 0;
1991 }
1992
1993 lock_page(page);
1994 /*
1995 * This test is racy because PG_hwpoison is set outside of page lock.
1996 * That's acceptable because that won't trigger kernel panic. Instead,
1997 * the PG_hwpoison page will be caught and isolated on the entrance to
1998 * the free buddy page pool.
1999 */
2000 if (TestClearPageHWPoison(page)) {
2001 unpoison_pr_info("Unpoison: Software-unpoisoned page %#lx\n",
2002 pfn, &unpoison_rs);
2003 num_poisoned_pages_dec();
2004 freeit = 1;
2005 }
2006 unlock_page(page);
2007
2008 put_page(page);
2009 if (freeit && !(pfn == my_zero_pfn(0) && page_count(p) == 1))
2010 put_page(page);
2011
2012 return 0;
2013}
2014EXPORT_SYMBOL(unpoison_memory);
2015
2016static bool isolate_page(struct page *page, struct list_head *pagelist)
2017{
2018 bool isolated = false;
2019 bool lru = PageLRU(page);
2020
2021 if (PageHuge(page)) {
2022 isolated = isolate_huge_page(page, pagelist);
2023 } else {
2024 if (lru)
2025 isolated = !isolate_lru_page(page);
2026 else
2027 isolated = !isolate_movable_page(page, ISOLATE_UNEVICTABLE);
2028
2029 if (isolated)
2030 list_add(&page->lru, pagelist);
2031 }
2032
2033 if (isolated && lru)
2034 inc_node_page_state(page, NR_ISOLATED_ANON +
2035 page_is_file_lru(page));
2036
2037 /*
2038 * If we succeed to isolate the page, we grabbed another refcount on
2039 * the page, so we can safely drop the one we got from get_any_pages().
2040 * If we failed to isolate the page, it means that we cannot go further
2041 * and we will return an error, so drop the reference we got from
2042 * get_any_pages() as well.
2043 */
2044 put_page(page);
2045 return isolated;
2046}
2047
2048/*
2049 * __soft_offline_page handles hugetlb-pages and non-hugetlb pages.
2050 * If the page is a non-dirty unmapped page-cache page, it simply invalidates.
2051 * If the page is mapped, it migrates the contents over.
2052 */
2053static int __soft_offline_page(struct page *page)
2054{
2055 int ret = 0;
2056 unsigned long pfn = page_to_pfn(page);
2057 struct page *hpage = compound_head(page);
2058 char const *msg_page[] = {"page", "hugepage"};
2059 bool huge = PageHuge(page);
2060 LIST_HEAD(pagelist);
2061 struct migration_target_control mtc = {
2062 .nid = NUMA_NO_NODE,
2063 .gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL,
2064 };
2065
2066 /*
2067 * Check PageHWPoison again inside page lock because PageHWPoison
2068 * is set by memory_failure() outside page lock. Note that
2069 * memory_failure() also double-checks PageHWPoison inside page lock,
2070 * so there's no race between soft_offline_page() and memory_failure().
2071 */
2072 lock_page(page);
2073 if (!PageHuge(page))
2074 wait_on_page_writeback(page);
2075 if (PageHWPoison(page)) {
2076 unlock_page(page);
2077 put_page(page);
2078 pr_info("soft offline: %#lx page already poisoned\n", pfn);
2079 return 0;
2080 }
2081
2082 if (!PageHuge(page))
2083 /*
2084 * Try to invalidate first. This should work for
2085 * non dirty unmapped page cache pages.
2086 */
2087 ret = invalidate_inode_page(page);
2088 unlock_page(page);
2089
2090 /*
2091 * RED-PEN would be better to keep it isolated here, but we
2092 * would need to fix isolation locking first.
2093 */
2094 if (ret) {
2095 pr_info("soft_offline: %#lx: invalidated\n", pfn);
2096 page_handle_poison(page, false, true);
2097 return 0;
2098 }
2099
2100 if (isolate_page(hpage, &pagelist)) {
2101 ret = migrate_pages(&pagelist, alloc_migration_target, NULL,
2102 (unsigned long)&mtc, MIGRATE_SYNC, MR_MEMORY_FAILURE);
2103 if (!ret) {
2104 bool release = !huge;
2105
2106 if (!page_handle_poison(page, huge, release))
2107 ret = -EBUSY;
2108 } else {
2109 if (!list_empty(&pagelist))
2110 putback_movable_pages(&pagelist);
2111
2112 pr_info("soft offline: %#lx: %s migration failed %d, type %lx (%pGp)\n",
2113 pfn, msg_page[huge], ret, page->flags, &page->flags);
2114 if (ret > 0)
2115 ret = -EBUSY;
2116 }
2117 } else {
2118 pr_info("soft offline: %#lx: %s isolation failed, page count %d, type %lx (%pGp)\n",
2119 pfn, msg_page[huge], page_count(page), page->flags, &page->flags);
2120 ret = -EBUSY;
2121 }
2122 return ret;
2123}
2124
2125static int soft_offline_in_use_page(struct page *page)
2126{
2127 struct page *hpage = compound_head(page);
2128
2129 if (!PageHuge(page) && PageTransHuge(hpage))
2130 if (try_to_split_thp_page(page, "soft offline") < 0)
2131 return -EBUSY;
2132 return __soft_offline_page(page);
2133}
2134
2135static int soft_offline_free_page(struct page *page)
2136{
2137 int rc = 0;
2138
2139 if (!page_handle_poison(page, true, false))
2140 rc = -EBUSY;
2141
2142 return rc;
2143}
2144
2145static void put_ref_page(struct page *page)
2146{
2147 if (page)
2148 put_page(page);
2149}
2150
2151/**
2152 * soft_offline_page - Soft offline a page.
2153 * @pfn: pfn to soft-offline
2154 * @flags: flags. Same as memory_failure().
2155 *
2156 * Returns 0 on success, otherwise negated errno.
2157 *
2158 * Soft offline a page, by migration or invalidation,
2159 * without killing anything. This is for the case when
2160 * a page is not corrupted yet (so it's still valid to access),
2161 * but has had a number of corrected errors and is better taken
2162 * out.
2163 *
2164 * The actual policy on when to do that is maintained by
2165 * user space.
2166 *
2167 * This should never impact any application or cause data loss,
2168 * however it might take some time.
2169 *
2170 * This is not a 100% solution for all memory, but tries to be
2171 * ``good enough'' for the majority of memory.
2172 */
2173int soft_offline_page(unsigned long pfn, int flags)
2174{
2175 int ret;
2176 bool try_again = true;
2177 struct page *page, *ref_page = NULL;
2178
2179 WARN_ON_ONCE(!pfn_valid(pfn) && (flags & MF_COUNT_INCREASED));
2180
2181 if (!pfn_valid(pfn))
2182 return -ENXIO;
2183 if (flags & MF_COUNT_INCREASED)
2184 ref_page = pfn_to_page(pfn);
2185
2186 /* Only online pages can be soft-offlined (esp., not ZONE_DEVICE). */
2187 page = pfn_to_online_page(pfn);
2188 if (!page) {
2189 put_ref_page(ref_page);
2190 return -EIO;
2191 }
2192
2193 if (PageHWPoison(page)) {
2194 pr_info("%s: %#lx page already poisoned\n", __func__, pfn);
2195 put_ref_page(ref_page);
2196 return 0;
2197 }
2198
2199retry:
2200 get_online_mems();
2201 ret = get_hwpoison_page(page, flags);
2202 put_online_mems();
2203
2204 if (ret > 0) {
2205 ret = soft_offline_in_use_page(page);
2206 } else if (ret == 0) {
2207 if (soft_offline_free_page(page) && try_again) {
2208 try_again = false;
2209 goto retry;
2210 }
2211 } else if (ret == -EIO) {
2212 pr_info("%s: %#lx: unknown page type: %lx (%pGp)\n",
2213 __func__, pfn, page->flags, &page->flags);
2214 }
2215
2216 return ret;
2217}