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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/mm/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
37#define pr_fmt(fmt) "Memory failure: " fmt
38
39#include <linux/kernel.h>
40#include <linux/mm.h>
41#include <linux/page-flags.h>
42#include <linux/sched/signal.h>
43#include <linux/sched/task.h>
44#include <linux/dax.h>
45#include <linux/ksm.h>
46#include <linux/rmap.h>
47#include <linux/export.h>
48#include <linux/pagemap.h>
49#include <linux/swap.h>
50#include <linux/backing-dev.h>
51#include <linux/migrate.h>
52#include <linux/slab.h>
53#include <linux/swapops.h>
54#include <linux/hugetlb.h>
55#include <linux/memory_hotplug.h>
56#include <linux/mm_inline.h>
57#include <linux/memremap.h>
58#include <linux/kfifo.h>
59#include <linux/ratelimit.h>
60#include <linux/pagewalk.h>
61#include <linux/shmem_fs.h>
62#include <linux/sysctl.h>
63#include "swap.h"
64#include "internal.h"
65#include "ras/ras_event.h"
66
67static int sysctl_memory_failure_early_kill __read_mostly;
68
69static int sysctl_memory_failure_recovery __read_mostly = 1;
70
71static int sysctl_enable_soft_offline __read_mostly = 1;
72
73atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0);
74
75static bool hw_memory_failure __read_mostly = false;
76
77static DEFINE_MUTEX(mf_mutex);
78
79void num_poisoned_pages_inc(unsigned long pfn)
80{
81 atomic_long_inc(&num_poisoned_pages);
82 memblk_nr_poison_inc(pfn);
83}
84
85void num_poisoned_pages_sub(unsigned long pfn, long i)
86{
87 atomic_long_sub(i, &num_poisoned_pages);
88 if (pfn != -1UL)
89 memblk_nr_poison_sub(pfn, i);
90}
91
92/**
93 * MF_ATTR_RO - Create sysfs entry for each memory failure statistics.
94 * @_name: name of the file in the per NUMA sysfs directory.
95 */
96#define MF_ATTR_RO(_name) \
97static ssize_t _name##_show(struct device *dev, \
98 struct device_attribute *attr, \
99 char *buf) \
100{ \
101 struct memory_failure_stats *mf_stats = \
102 &NODE_DATA(dev->id)->mf_stats; \
103 return sysfs_emit(buf, "%lu\n", mf_stats->_name); \
104} \
105static DEVICE_ATTR_RO(_name)
106
107MF_ATTR_RO(total);
108MF_ATTR_RO(ignored);
109MF_ATTR_RO(failed);
110MF_ATTR_RO(delayed);
111MF_ATTR_RO(recovered);
112
113static struct attribute *memory_failure_attr[] = {
114 &dev_attr_total.attr,
115 &dev_attr_ignored.attr,
116 &dev_attr_failed.attr,
117 &dev_attr_delayed.attr,
118 &dev_attr_recovered.attr,
119 NULL,
120};
121
122const struct attribute_group memory_failure_attr_group = {
123 .name = "memory_failure",
124 .attrs = memory_failure_attr,
125};
126
127static struct ctl_table memory_failure_table[] = {
128 {
129 .procname = "memory_failure_early_kill",
130 .data = &sysctl_memory_failure_early_kill,
131 .maxlen = sizeof(sysctl_memory_failure_early_kill),
132 .mode = 0644,
133 .proc_handler = proc_dointvec_minmax,
134 .extra1 = SYSCTL_ZERO,
135 .extra2 = SYSCTL_ONE,
136 },
137 {
138 .procname = "memory_failure_recovery",
139 .data = &sysctl_memory_failure_recovery,
140 .maxlen = sizeof(sysctl_memory_failure_recovery),
141 .mode = 0644,
142 .proc_handler = proc_dointvec_minmax,
143 .extra1 = SYSCTL_ZERO,
144 .extra2 = SYSCTL_ONE,
145 },
146 {
147 .procname = "enable_soft_offline",
148 .data = &sysctl_enable_soft_offline,
149 .maxlen = sizeof(sysctl_enable_soft_offline),
150 .mode = 0644,
151 .proc_handler = proc_dointvec_minmax,
152 .extra1 = SYSCTL_ZERO,
153 .extra2 = SYSCTL_ONE,
154 }
155};
156
157/*
158 * Return values:
159 * 1: the page is dissolved (if needed) and taken off from buddy,
160 * 0: the page is dissolved (if needed) and not taken off from buddy,
161 * < 0: failed to dissolve.
162 */
163static int __page_handle_poison(struct page *page)
164{
165 int ret;
166
167 /*
168 * zone_pcp_disable() can't be used here. It will
169 * hold pcp_batch_high_lock and dissolve_free_hugetlb_folio() might hold
170 * cpu_hotplug_lock via static_key_slow_dec() when hugetlb vmemmap
171 * optimization is enabled. This will break current lock dependency
172 * chain and leads to deadlock.
173 * Disabling pcp before dissolving the page was a deterministic
174 * approach because we made sure that those pages cannot end up in any
175 * PCP list. Draining PCP lists expels those pages to the buddy system,
176 * but nothing guarantees that those pages do not get back to a PCP
177 * queue if we need to refill those.
178 */
179 ret = dissolve_free_hugetlb_folio(page_folio(page));
180 if (!ret) {
181 drain_all_pages(page_zone(page));
182 ret = take_page_off_buddy(page);
183 }
184
185 return ret;
186}
187
188static bool page_handle_poison(struct page *page, bool hugepage_or_freepage, bool release)
189{
190 if (hugepage_or_freepage) {
191 /*
192 * Doing this check for free pages is also fine since
193 * dissolve_free_hugetlb_folio() returns 0 for non-hugetlb folios as well.
194 */
195 if (__page_handle_poison(page) <= 0)
196 /*
197 * We could fail to take off the target page from buddy
198 * for example due to racy page allocation, but that's
199 * acceptable because soft-offlined page is not broken
200 * and if someone really want to use it, they should
201 * take it.
202 */
203 return false;
204 }
205
206 SetPageHWPoison(page);
207 if (release)
208 put_page(page);
209 page_ref_inc(page);
210 num_poisoned_pages_inc(page_to_pfn(page));
211
212 return true;
213}
214
215#if IS_ENABLED(CONFIG_HWPOISON_INJECT)
216
217u32 hwpoison_filter_enable = 0;
218u32 hwpoison_filter_dev_major = ~0U;
219u32 hwpoison_filter_dev_minor = ~0U;
220u64 hwpoison_filter_flags_mask;
221u64 hwpoison_filter_flags_value;
222EXPORT_SYMBOL_GPL(hwpoison_filter_enable);
223EXPORT_SYMBOL_GPL(hwpoison_filter_dev_major);
224EXPORT_SYMBOL_GPL(hwpoison_filter_dev_minor);
225EXPORT_SYMBOL_GPL(hwpoison_filter_flags_mask);
226EXPORT_SYMBOL_GPL(hwpoison_filter_flags_value);
227
228static int hwpoison_filter_dev(struct page *p)
229{
230 struct folio *folio = page_folio(p);
231 struct address_space *mapping;
232 dev_t dev;
233
234 if (hwpoison_filter_dev_major == ~0U &&
235 hwpoison_filter_dev_minor == ~0U)
236 return 0;
237
238 mapping = folio_mapping(folio);
239 if (mapping == NULL || mapping->host == NULL)
240 return -EINVAL;
241
242 dev = mapping->host->i_sb->s_dev;
243 if (hwpoison_filter_dev_major != ~0U &&
244 hwpoison_filter_dev_major != MAJOR(dev))
245 return -EINVAL;
246 if (hwpoison_filter_dev_minor != ~0U &&
247 hwpoison_filter_dev_minor != MINOR(dev))
248 return -EINVAL;
249
250 return 0;
251}
252
253static int hwpoison_filter_flags(struct page *p)
254{
255 if (!hwpoison_filter_flags_mask)
256 return 0;
257
258 if ((stable_page_flags(p) & hwpoison_filter_flags_mask) ==
259 hwpoison_filter_flags_value)
260 return 0;
261 else
262 return -EINVAL;
263}
264
265/*
266 * This allows stress tests to limit test scope to a collection of tasks
267 * by putting them under some memcg. This prevents killing unrelated/important
268 * processes such as /sbin/init. Note that the target task may share clean
269 * pages with init (eg. libc text), which is harmless. If the target task
270 * share _dirty_ pages with another task B, the test scheme must make sure B
271 * is also included in the memcg. At last, due to race conditions this filter
272 * can only guarantee that the page either belongs to the memcg tasks, or is
273 * a freed page.
274 */
275#ifdef CONFIG_MEMCG
276u64 hwpoison_filter_memcg;
277EXPORT_SYMBOL_GPL(hwpoison_filter_memcg);
278static int hwpoison_filter_task(struct page *p)
279{
280 if (!hwpoison_filter_memcg)
281 return 0;
282
283 if (page_cgroup_ino(p) != hwpoison_filter_memcg)
284 return -EINVAL;
285
286 return 0;
287}
288#else
289static int hwpoison_filter_task(struct page *p) { return 0; }
290#endif
291
292int hwpoison_filter(struct page *p)
293{
294 if (!hwpoison_filter_enable)
295 return 0;
296
297 if (hwpoison_filter_dev(p))
298 return -EINVAL;
299
300 if (hwpoison_filter_flags(p))
301 return -EINVAL;
302
303 if (hwpoison_filter_task(p))
304 return -EINVAL;
305
306 return 0;
307}
308EXPORT_SYMBOL_GPL(hwpoison_filter);
309#else
310int hwpoison_filter(struct page *p)
311{
312 return 0;
313}
314#endif
315
316/*
317 * Kill all processes that have a poisoned page mapped and then isolate
318 * the page.
319 *
320 * General strategy:
321 * Find all processes having the page mapped and kill them.
322 * But we keep a page reference around so that the page is not
323 * actually freed yet.
324 * Then stash the page away
325 *
326 * There's no convenient way to get back to mapped processes
327 * from the VMAs. So do a brute-force search over all
328 * running processes.
329 *
330 * Remember that machine checks are not common (or rather
331 * if they are common you have other problems), so this shouldn't
332 * be a performance issue.
333 *
334 * Also there are some races possible while we get from the
335 * error detection to actually handle it.
336 */
337
338struct to_kill {
339 struct list_head nd;
340 struct task_struct *tsk;
341 unsigned long addr;
342 short size_shift;
343};
344
345/*
346 * Send all the processes who have the page mapped a signal.
347 * ``action optional'' if they are not immediately affected by the error
348 * ``action required'' if error happened in current execution context
349 */
350static int kill_proc(struct to_kill *tk, unsigned long pfn, int flags)
351{
352 struct task_struct *t = tk->tsk;
353 short addr_lsb = tk->size_shift;
354 int ret = 0;
355
356 pr_err("%#lx: Sending SIGBUS to %s:%d due to hardware memory corruption\n",
357 pfn, t->comm, task_pid_nr(t));
358
359 if ((flags & MF_ACTION_REQUIRED) && (t == current))
360 ret = force_sig_mceerr(BUS_MCEERR_AR,
361 (void __user *)tk->addr, addr_lsb);
362 else
363 /*
364 * Signal other processes sharing the page if they have
365 * PF_MCE_EARLY set.
366 * Don't use force here, it's convenient if the signal
367 * can be temporarily blocked.
368 */
369 ret = send_sig_mceerr(BUS_MCEERR_AO, (void __user *)tk->addr,
370 addr_lsb, t);
371 if (ret < 0)
372 pr_info("Error sending signal to %s:%d: %d\n",
373 t->comm, task_pid_nr(t), ret);
374 return ret;
375}
376
377/*
378 * Unknown page type encountered. Try to check whether it can turn PageLRU by
379 * lru_add_drain_all.
380 */
381void shake_folio(struct folio *folio)
382{
383 if (folio_test_hugetlb(folio))
384 return;
385 /*
386 * TODO: Could shrink slab caches here if a lightweight range-based
387 * shrinker will be available.
388 */
389 if (folio_test_slab(folio))
390 return;
391
392 lru_add_drain_all();
393}
394EXPORT_SYMBOL_GPL(shake_folio);
395
396static void shake_page(struct page *page)
397{
398 shake_folio(page_folio(page));
399}
400
401static unsigned long dev_pagemap_mapping_shift(struct vm_area_struct *vma,
402 unsigned long address)
403{
404 unsigned long ret = 0;
405 pgd_t *pgd;
406 p4d_t *p4d;
407 pud_t *pud;
408 pmd_t *pmd;
409 pte_t *pte;
410 pte_t ptent;
411
412 VM_BUG_ON_VMA(address == -EFAULT, vma);
413 pgd = pgd_offset(vma->vm_mm, address);
414 if (!pgd_present(*pgd))
415 return 0;
416 p4d = p4d_offset(pgd, address);
417 if (!p4d_present(*p4d))
418 return 0;
419 pud = pud_offset(p4d, address);
420 if (!pud_present(*pud))
421 return 0;
422 if (pud_devmap(*pud))
423 return PUD_SHIFT;
424 pmd = pmd_offset(pud, address);
425 if (!pmd_present(*pmd))
426 return 0;
427 if (pmd_devmap(*pmd))
428 return PMD_SHIFT;
429 pte = pte_offset_map(pmd, address);
430 if (!pte)
431 return 0;
432 ptent = ptep_get(pte);
433 if (pte_present(ptent) && pte_devmap(ptent))
434 ret = PAGE_SHIFT;
435 pte_unmap(pte);
436 return ret;
437}
438
439/*
440 * Failure handling: if we can't find or can't kill a process there's
441 * not much we can do. We just print a message and ignore otherwise.
442 */
443
444/*
445 * Schedule a process for later kill.
446 * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
447 */
448static void __add_to_kill(struct task_struct *tsk, const struct page *p,
449 struct vm_area_struct *vma, struct list_head *to_kill,
450 unsigned long addr)
451{
452 struct to_kill *tk;
453
454 tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
455 if (!tk) {
456 pr_err("Out of memory while machine check handling\n");
457 return;
458 }
459
460 tk->addr = addr;
461 if (is_zone_device_page(p))
462 tk->size_shift = dev_pagemap_mapping_shift(vma, tk->addr);
463 else
464 tk->size_shift = folio_shift(page_folio(p));
465
466 /*
467 * Send SIGKILL if "tk->addr == -EFAULT". Also, as
468 * "tk->size_shift" is always non-zero for !is_zone_device_page(),
469 * so "tk->size_shift == 0" effectively checks no mapping on
470 * ZONE_DEVICE. Indeed, when a devdax page is mmapped N times
471 * to a process' address space, it's possible not all N VMAs
472 * contain mappings for the page, but at least one VMA does.
473 * Only deliver SIGBUS with payload derived from the VMA that
474 * has a mapping for the page.
475 */
476 if (tk->addr == -EFAULT) {
477 pr_info("Unable to find user space address %lx in %s\n",
478 page_to_pfn(p), tsk->comm);
479 } else if (tk->size_shift == 0) {
480 kfree(tk);
481 return;
482 }
483
484 get_task_struct(tsk);
485 tk->tsk = tsk;
486 list_add_tail(&tk->nd, to_kill);
487}
488
489static void add_to_kill_anon_file(struct task_struct *tsk, const struct page *p,
490 struct vm_area_struct *vma, struct list_head *to_kill,
491 unsigned long addr)
492{
493 if (addr == -EFAULT)
494 return;
495 __add_to_kill(tsk, p, vma, to_kill, addr);
496}
497
498#ifdef CONFIG_KSM
499static bool task_in_to_kill_list(struct list_head *to_kill,
500 struct task_struct *tsk)
501{
502 struct to_kill *tk, *next;
503
504 list_for_each_entry_safe(tk, next, to_kill, nd) {
505 if (tk->tsk == tsk)
506 return true;
507 }
508
509 return false;
510}
511
512void add_to_kill_ksm(struct task_struct *tsk, const struct page *p,
513 struct vm_area_struct *vma, struct list_head *to_kill,
514 unsigned long addr)
515{
516 if (!task_in_to_kill_list(to_kill, tsk))
517 __add_to_kill(tsk, p, vma, to_kill, addr);
518}
519#endif
520/*
521 * Kill the processes that have been collected earlier.
522 *
523 * Only do anything when FORCEKILL is set, otherwise just free the
524 * list (this is used for clean pages which do not need killing)
525 */
526static void kill_procs(struct list_head *to_kill, int forcekill,
527 unsigned long pfn, int flags)
528{
529 struct to_kill *tk, *next;
530
531 list_for_each_entry_safe(tk, next, to_kill, nd) {
532 if (forcekill) {
533 if (tk->addr == -EFAULT) {
534 pr_err("%#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n",
535 pfn, tk->tsk->comm, task_pid_nr(tk->tsk));
536 do_send_sig_info(SIGKILL, SEND_SIG_PRIV,
537 tk->tsk, PIDTYPE_PID);
538 }
539
540 /*
541 * In theory the process could have mapped
542 * something else on the address in-between. We could
543 * check for that, but we need to tell the
544 * process anyways.
545 */
546 else if (kill_proc(tk, pfn, flags) < 0)
547 pr_err("%#lx: Cannot send advisory machine check signal to %s:%d\n",
548 pfn, tk->tsk->comm, task_pid_nr(tk->tsk));
549 }
550 list_del(&tk->nd);
551 put_task_struct(tk->tsk);
552 kfree(tk);
553 }
554}
555
556/*
557 * Find a dedicated thread which is supposed to handle SIGBUS(BUS_MCEERR_AO)
558 * on behalf of the thread group. Return task_struct of the (first found)
559 * dedicated thread if found, and return NULL otherwise.
560 *
561 * We already hold rcu lock in the caller, so we don't have to call
562 * rcu_read_lock/unlock() in this function.
563 */
564static struct task_struct *find_early_kill_thread(struct task_struct *tsk)
565{
566 struct task_struct *t;
567
568 for_each_thread(tsk, t) {
569 if (t->flags & PF_MCE_PROCESS) {
570 if (t->flags & PF_MCE_EARLY)
571 return t;
572 } else {
573 if (sysctl_memory_failure_early_kill)
574 return t;
575 }
576 }
577 return NULL;
578}
579
580/*
581 * Determine whether a given process is "early kill" process which expects
582 * to be signaled when some page under the process is hwpoisoned.
583 * Return task_struct of the dedicated thread (main thread unless explicitly
584 * specified) if the process is "early kill" and otherwise returns NULL.
585 *
586 * Note that the above is true for Action Optional case. For Action Required
587 * case, it's only meaningful to the current thread which need to be signaled
588 * with SIGBUS, this error is Action Optional for other non current
589 * processes sharing the same error page,if the process is "early kill", the
590 * task_struct of the dedicated thread will also be returned.
591 */
592struct task_struct *task_early_kill(struct task_struct *tsk, int force_early)
593{
594 if (!tsk->mm)
595 return NULL;
596 /*
597 * Comparing ->mm here because current task might represent
598 * a subthread, while tsk always points to the main thread.
599 */
600 if (force_early && tsk->mm == current->mm)
601 return current;
602
603 return find_early_kill_thread(tsk);
604}
605
606/*
607 * Collect processes when the error hit an anonymous page.
608 */
609static void collect_procs_anon(const struct folio *folio,
610 const struct page *page, struct list_head *to_kill,
611 int force_early)
612{
613 struct task_struct *tsk;
614 struct anon_vma *av;
615 pgoff_t pgoff;
616
617 av = folio_lock_anon_vma_read(folio, NULL);
618 if (av == NULL) /* Not actually mapped anymore */
619 return;
620
621 pgoff = page_pgoff(folio, page);
622 rcu_read_lock();
623 for_each_process(tsk) {
624 struct vm_area_struct *vma;
625 struct anon_vma_chain *vmac;
626 struct task_struct *t = task_early_kill(tsk, force_early);
627 unsigned long addr;
628
629 if (!t)
630 continue;
631 anon_vma_interval_tree_foreach(vmac, &av->rb_root,
632 pgoff, pgoff) {
633 vma = vmac->vma;
634 if (vma->vm_mm != t->mm)
635 continue;
636 addr = page_mapped_in_vma(page, vma);
637 add_to_kill_anon_file(t, page, vma, to_kill, addr);
638 }
639 }
640 rcu_read_unlock();
641 anon_vma_unlock_read(av);
642}
643
644/*
645 * Collect processes when the error hit a file mapped page.
646 */
647static void collect_procs_file(const struct folio *folio,
648 const struct page *page, struct list_head *to_kill,
649 int force_early)
650{
651 struct vm_area_struct *vma;
652 struct task_struct *tsk;
653 struct address_space *mapping = folio->mapping;
654 pgoff_t pgoff;
655
656 i_mmap_lock_read(mapping);
657 rcu_read_lock();
658 pgoff = page_pgoff(folio, page);
659 for_each_process(tsk) {
660 struct task_struct *t = task_early_kill(tsk, force_early);
661 unsigned long addr;
662
663 if (!t)
664 continue;
665 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff,
666 pgoff) {
667 /*
668 * Send early kill signal to tasks where a vma covers
669 * the page but the corrupted page is not necessarily
670 * mapped in its pte.
671 * Assume applications who requested early kill want
672 * to be informed of all such data corruptions.
673 */
674 if (vma->vm_mm != t->mm)
675 continue;
676 addr = page_address_in_vma(folio, page, vma);
677 add_to_kill_anon_file(t, page, vma, to_kill, addr);
678 }
679 }
680 rcu_read_unlock();
681 i_mmap_unlock_read(mapping);
682}
683
684#ifdef CONFIG_FS_DAX
685static void add_to_kill_fsdax(struct task_struct *tsk, const struct page *p,
686 struct vm_area_struct *vma,
687 struct list_head *to_kill, pgoff_t pgoff)
688{
689 unsigned long addr = vma_address(vma, pgoff, 1);
690 __add_to_kill(tsk, p, vma, to_kill, addr);
691}
692
693/*
694 * Collect processes when the error hit a fsdax page.
695 */
696static void collect_procs_fsdax(const struct page *page,
697 struct address_space *mapping, pgoff_t pgoff,
698 struct list_head *to_kill, bool pre_remove)
699{
700 struct vm_area_struct *vma;
701 struct task_struct *tsk;
702
703 i_mmap_lock_read(mapping);
704 rcu_read_lock();
705 for_each_process(tsk) {
706 struct task_struct *t = tsk;
707
708 /*
709 * Search for all tasks while MF_MEM_PRE_REMOVE is set, because
710 * the current may not be the one accessing the fsdax page.
711 * Otherwise, search for the current task.
712 */
713 if (!pre_remove)
714 t = task_early_kill(tsk, true);
715 if (!t)
716 continue;
717 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
718 if (vma->vm_mm == t->mm)
719 add_to_kill_fsdax(t, page, vma, to_kill, pgoff);
720 }
721 }
722 rcu_read_unlock();
723 i_mmap_unlock_read(mapping);
724}
725#endif /* CONFIG_FS_DAX */
726
727/*
728 * Collect the processes who have the corrupted page mapped to kill.
729 */
730static void collect_procs(const struct folio *folio, const struct page *page,
731 struct list_head *tokill, int force_early)
732{
733 if (!folio->mapping)
734 return;
735 if (unlikely(folio_test_ksm(folio)))
736 collect_procs_ksm(folio, page, tokill, force_early);
737 else if (folio_test_anon(folio))
738 collect_procs_anon(folio, page, tokill, force_early);
739 else
740 collect_procs_file(folio, page, tokill, force_early);
741}
742
743struct hwpoison_walk {
744 struct to_kill tk;
745 unsigned long pfn;
746 int flags;
747};
748
749static void set_to_kill(struct to_kill *tk, unsigned long addr, short shift)
750{
751 tk->addr = addr;
752 tk->size_shift = shift;
753}
754
755static int check_hwpoisoned_entry(pte_t pte, unsigned long addr, short shift,
756 unsigned long poisoned_pfn, struct to_kill *tk)
757{
758 unsigned long pfn = 0;
759
760 if (pte_present(pte)) {
761 pfn = pte_pfn(pte);
762 } else {
763 swp_entry_t swp = pte_to_swp_entry(pte);
764
765 if (is_hwpoison_entry(swp))
766 pfn = swp_offset_pfn(swp);
767 }
768
769 if (!pfn || pfn != poisoned_pfn)
770 return 0;
771
772 set_to_kill(tk, addr, shift);
773 return 1;
774}
775
776#ifdef CONFIG_TRANSPARENT_HUGEPAGE
777static int check_hwpoisoned_pmd_entry(pmd_t *pmdp, unsigned long addr,
778 struct hwpoison_walk *hwp)
779{
780 pmd_t pmd = *pmdp;
781 unsigned long pfn;
782 unsigned long hwpoison_vaddr;
783
784 if (!pmd_present(pmd))
785 return 0;
786 pfn = pmd_pfn(pmd);
787 if (pfn <= hwp->pfn && hwp->pfn < pfn + HPAGE_PMD_NR) {
788 hwpoison_vaddr = addr + ((hwp->pfn - pfn) << PAGE_SHIFT);
789 set_to_kill(&hwp->tk, hwpoison_vaddr, PAGE_SHIFT);
790 return 1;
791 }
792 return 0;
793}
794#else
795static int check_hwpoisoned_pmd_entry(pmd_t *pmdp, unsigned long addr,
796 struct hwpoison_walk *hwp)
797{
798 return 0;
799}
800#endif
801
802static int hwpoison_pte_range(pmd_t *pmdp, unsigned long addr,
803 unsigned long end, struct mm_walk *walk)
804{
805 struct hwpoison_walk *hwp = walk->private;
806 int ret = 0;
807 pte_t *ptep, *mapped_pte;
808 spinlock_t *ptl;
809
810 ptl = pmd_trans_huge_lock(pmdp, walk->vma);
811 if (ptl) {
812 ret = check_hwpoisoned_pmd_entry(pmdp, addr, hwp);
813 spin_unlock(ptl);
814 goto out;
815 }
816
817 mapped_pte = ptep = pte_offset_map_lock(walk->vma->vm_mm, pmdp,
818 addr, &ptl);
819 if (!ptep)
820 goto out;
821
822 for (; addr != end; ptep++, addr += PAGE_SIZE) {
823 ret = check_hwpoisoned_entry(ptep_get(ptep), addr, PAGE_SHIFT,
824 hwp->pfn, &hwp->tk);
825 if (ret == 1)
826 break;
827 }
828 pte_unmap_unlock(mapped_pte, ptl);
829out:
830 cond_resched();
831 return ret;
832}
833
834#ifdef CONFIG_HUGETLB_PAGE
835static int hwpoison_hugetlb_range(pte_t *ptep, unsigned long hmask,
836 unsigned long addr, unsigned long end,
837 struct mm_walk *walk)
838{
839 struct hwpoison_walk *hwp = walk->private;
840 pte_t pte = huge_ptep_get(walk->mm, addr, ptep);
841 struct hstate *h = hstate_vma(walk->vma);
842
843 return check_hwpoisoned_entry(pte, addr, huge_page_shift(h),
844 hwp->pfn, &hwp->tk);
845}
846#else
847#define hwpoison_hugetlb_range NULL
848#endif
849
850static const struct mm_walk_ops hwpoison_walk_ops = {
851 .pmd_entry = hwpoison_pte_range,
852 .hugetlb_entry = hwpoison_hugetlb_range,
853 .walk_lock = PGWALK_RDLOCK,
854};
855
856/*
857 * Sends SIGBUS to the current process with error info.
858 *
859 * This function is intended to handle "Action Required" MCEs on already
860 * hardware poisoned pages. They could happen, for example, when
861 * memory_failure() failed to unmap the error page at the first call, or
862 * when multiple local machine checks happened on different CPUs.
863 *
864 * MCE handler currently has no easy access to the error virtual address,
865 * so this function walks page table to find it. The returned virtual address
866 * is proper in most cases, but it could be wrong when the application
867 * process has multiple entries mapping the error page.
868 */
869static int kill_accessing_process(struct task_struct *p, unsigned long pfn,
870 int flags)
871{
872 int ret;
873 struct hwpoison_walk priv = {
874 .pfn = pfn,
875 };
876 priv.tk.tsk = p;
877
878 if (!p->mm)
879 return -EFAULT;
880
881 mmap_read_lock(p->mm);
882 ret = walk_page_range(p->mm, 0, TASK_SIZE, &hwpoison_walk_ops,
883 (void *)&priv);
884 if (ret == 1 && priv.tk.addr)
885 kill_proc(&priv.tk, pfn, flags);
886 else
887 ret = 0;
888 mmap_read_unlock(p->mm);
889 return ret > 0 ? -EHWPOISON : -EFAULT;
890}
891
892/*
893 * MF_IGNORED - The m-f() handler marks the page as PG_hwpoisoned'ed.
894 * But it could not do more to isolate the page from being accessed again,
895 * nor does it kill the process. This is extremely rare and one of the
896 * potential causes is that the page state has been changed due to
897 * underlying race condition. This is the most severe outcomes.
898 *
899 * MF_FAILED - The m-f() handler marks the page as PG_hwpoisoned'ed.
900 * It should have killed the process, but it can't isolate the page,
901 * due to conditions such as extra pin, unmap failure, etc. Accessing
902 * the page again may trigger another MCE and the process will be killed
903 * by the m-f() handler immediately.
904 *
905 * MF_DELAYED - The m-f() handler marks the page as PG_hwpoisoned'ed.
906 * The page is unmapped, and is removed from the LRU or file mapping.
907 * An attempt to access the page again will trigger page fault and the
908 * PF handler will kill the process.
909 *
910 * MF_RECOVERED - The m-f() handler marks the page as PG_hwpoisoned'ed.
911 * The page has been completely isolated, that is, unmapped, taken out of
912 * the buddy system, or hole-punnched out of the file mapping.
913 */
914static const char *action_name[] = {
915 [MF_IGNORED] = "Ignored",
916 [MF_FAILED] = "Failed",
917 [MF_DELAYED] = "Delayed",
918 [MF_RECOVERED] = "Recovered",
919};
920
921static const char * const action_page_types[] = {
922 [MF_MSG_KERNEL] = "reserved kernel page",
923 [MF_MSG_KERNEL_HIGH_ORDER] = "high-order kernel page",
924 [MF_MSG_HUGE] = "huge page",
925 [MF_MSG_FREE_HUGE] = "free huge page",
926 [MF_MSG_GET_HWPOISON] = "get hwpoison page",
927 [MF_MSG_UNMAP_FAILED] = "unmapping failed page",
928 [MF_MSG_DIRTY_SWAPCACHE] = "dirty swapcache page",
929 [MF_MSG_CLEAN_SWAPCACHE] = "clean swapcache page",
930 [MF_MSG_DIRTY_MLOCKED_LRU] = "dirty mlocked LRU page",
931 [MF_MSG_CLEAN_MLOCKED_LRU] = "clean mlocked LRU page",
932 [MF_MSG_DIRTY_UNEVICTABLE_LRU] = "dirty unevictable LRU page",
933 [MF_MSG_CLEAN_UNEVICTABLE_LRU] = "clean unevictable LRU page",
934 [MF_MSG_DIRTY_LRU] = "dirty LRU page",
935 [MF_MSG_CLEAN_LRU] = "clean LRU page",
936 [MF_MSG_TRUNCATED_LRU] = "already truncated LRU page",
937 [MF_MSG_BUDDY] = "free buddy page",
938 [MF_MSG_DAX] = "dax page",
939 [MF_MSG_UNSPLIT_THP] = "unsplit thp",
940 [MF_MSG_ALREADY_POISONED] = "already poisoned",
941 [MF_MSG_UNKNOWN] = "unknown page",
942};
943
944/*
945 * XXX: It is possible that a page is isolated from LRU cache,
946 * and then kept in swap cache or failed to remove from page cache.
947 * The page count will stop it from being freed by unpoison.
948 * Stress tests should be aware of this memory leak problem.
949 */
950static int delete_from_lru_cache(struct folio *folio)
951{
952 if (folio_isolate_lru(folio)) {
953 /*
954 * Clear sensible page flags, so that the buddy system won't
955 * complain when the folio is unpoison-and-freed.
956 */
957 folio_clear_active(folio);
958 folio_clear_unevictable(folio);
959
960 /*
961 * Poisoned page might never drop its ref count to 0 so we have
962 * to uncharge it manually from its memcg.
963 */
964 mem_cgroup_uncharge(folio);
965
966 /*
967 * drop the refcount elevated by folio_isolate_lru()
968 */
969 folio_put(folio);
970 return 0;
971 }
972 return -EIO;
973}
974
975static int truncate_error_folio(struct folio *folio, unsigned long pfn,
976 struct address_space *mapping)
977{
978 int ret = MF_FAILED;
979
980 if (mapping->a_ops->error_remove_folio) {
981 int err = mapping->a_ops->error_remove_folio(mapping, folio);
982
983 if (err != 0)
984 pr_info("%#lx: Failed to punch page: %d\n", pfn, err);
985 else if (!filemap_release_folio(folio, GFP_NOIO))
986 pr_info("%#lx: failed to release buffers\n", pfn);
987 else
988 ret = MF_RECOVERED;
989 } else {
990 /*
991 * If the file system doesn't support it just invalidate
992 * This fails on dirty or anything with private pages
993 */
994 if (mapping_evict_folio(mapping, folio))
995 ret = MF_RECOVERED;
996 else
997 pr_info("%#lx: Failed to invalidate\n", pfn);
998 }
999
1000 return ret;
1001}
1002
1003struct page_state {
1004 unsigned long mask;
1005 unsigned long res;
1006 enum mf_action_page_type type;
1007
1008 /* Callback ->action() has to unlock the relevant page inside it. */
1009 int (*action)(struct page_state *ps, struct page *p);
1010};
1011
1012/*
1013 * Return true if page is still referenced by others, otherwise return
1014 * false.
1015 *
1016 * The extra_pins is true when one extra refcount is expected.
1017 */
1018static bool has_extra_refcount(struct page_state *ps, struct page *p,
1019 bool extra_pins)
1020{
1021 int count = page_count(p) - 1;
1022
1023 if (extra_pins)
1024 count -= folio_nr_pages(page_folio(p));
1025
1026 if (count > 0) {
1027 pr_err("%#lx: %s still referenced by %d users\n",
1028 page_to_pfn(p), action_page_types[ps->type], count);
1029 return true;
1030 }
1031
1032 return false;
1033}
1034
1035/*
1036 * Error hit kernel page.
1037 * Do nothing, try to be lucky and not touch this instead. For a few cases we
1038 * could be more sophisticated.
1039 */
1040static int me_kernel(struct page_state *ps, struct page *p)
1041{
1042 unlock_page(p);
1043 return MF_IGNORED;
1044}
1045
1046/*
1047 * Page in unknown state. Do nothing.
1048 * This is a catch-all in case we fail to make sense of the page state.
1049 */
1050static int me_unknown(struct page_state *ps, struct page *p)
1051{
1052 pr_err("%#lx: Unknown page state\n", page_to_pfn(p));
1053 unlock_page(p);
1054 return MF_IGNORED;
1055}
1056
1057/*
1058 * Clean (or cleaned) page cache page.
1059 */
1060static int me_pagecache_clean(struct page_state *ps, struct page *p)
1061{
1062 struct folio *folio = page_folio(p);
1063 int ret;
1064 struct address_space *mapping;
1065 bool extra_pins;
1066
1067 delete_from_lru_cache(folio);
1068
1069 /*
1070 * For anonymous folios the only reference left
1071 * should be the one m_f() holds.
1072 */
1073 if (folio_test_anon(folio)) {
1074 ret = MF_RECOVERED;
1075 goto out;
1076 }
1077
1078 /*
1079 * Now truncate the page in the page cache. This is really
1080 * more like a "temporary hole punch"
1081 * Don't do this for block devices when someone else
1082 * has a reference, because it could be file system metadata
1083 * and that's not safe to truncate.
1084 */
1085 mapping = folio_mapping(folio);
1086 if (!mapping) {
1087 /* Folio has been torn down in the meantime */
1088 ret = MF_FAILED;
1089 goto out;
1090 }
1091
1092 /*
1093 * The shmem page is kept in page cache instead of truncating
1094 * so is expected to have an extra refcount after error-handling.
1095 */
1096 extra_pins = shmem_mapping(mapping);
1097
1098 /*
1099 * Truncation is a bit tricky. Enable it per file system for now.
1100 *
1101 * Open: to take i_rwsem or not for this? Right now we don't.
1102 */
1103 ret = truncate_error_folio(folio, page_to_pfn(p), mapping);
1104 if (has_extra_refcount(ps, p, extra_pins))
1105 ret = MF_FAILED;
1106
1107out:
1108 folio_unlock(folio);
1109
1110 return ret;
1111}
1112
1113/*
1114 * Dirty pagecache page
1115 * Issues: when the error hit a hole page the error is not properly
1116 * propagated.
1117 */
1118static int me_pagecache_dirty(struct page_state *ps, struct page *p)
1119{
1120 struct folio *folio = page_folio(p);
1121 struct address_space *mapping = folio_mapping(folio);
1122
1123 /* TBD: print more information about the file. */
1124 if (mapping) {
1125 /*
1126 * IO error will be reported by write(), fsync(), etc.
1127 * who check the mapping.
1128 * This way the application knows that something went
1129 * wrong with its dirty file data.
1130 */
1131 mapping_set_error(mapping, -EIO);
1132 }
1133
1134 return me_pagecache_clean(ps, p);
1135}
1136
1137/*
1138 * Clean and dirty swap cache.
1139 *
1140 * Dirty swap cache page is tricky to handle. The page could live both in page
1141 * table and swap cache(ie. page is freshly swapped in). So it could be
1142 * referenced concurrently by 2 types of PTEs:
1143 * normal PTEs and swap PTEs. We try to handle them consistently by calling
1144 * try_to_unmap(!TTU_HWPOISON) to convert the normal PTEs to swap PTEs,
1145 * and then
1146 * - clear dirty bit to prevent IO
1147 * - remove from LRU
1148 * - but keep in the swap cache, so that when we return to it on
1149 * a later page fault, we know the application is accessing
1150 * corrupted data and shall be killed (we installed simple
1151 * interception code in do_swap_page to catch it).
1152 *
1153 * Clean swap cache pages can be directly isolated. A later page fault will
1154 * bring in the known good data from disk.
1155 */
1156static int me_swapcache_dirty(struct page_state *ps, struct page *p)
1157{
1158 struct folio *folio = page_folio(p);
1159 int ret;
1160 bool extra_pins = false;
1161
1162 folio_clear_dirty(folio);
1163 /* Trigger EIO in shmem: */
1164 folio_clear_uptodate(folio);
1165
1166 ret = delete_from_lru_cache(folio) ? MF_FAILED : MF_DELAYED;
1167 folio_unlock(folio);
1168
1169 if (ret == MF_DELAYED)
1170 extra_pins = true;
1171
1172 if (has_extra_refcount(ps, p, extra_pins))
1173 ret = MF_FAILED;
1174
1175 return ret;
1176}
1177
1178static int me_swapcache_clean(struct page_state *ps, struct page *p)
1179{
1180 struct folio *folio = page_folio(p);
1181 int ret;
1182
1183 delete_from_swap_cache(folio);
1184
1185 ret = delete_from_lru_cache(folio) ? MF_FAILED : MF_RECOVERED;
1186 folio_unlock(folio);
1187
1188 if (has_extra_refcount(ps, p, false))
1189 ret = MF_FAILED;
1190
1191 return ret;
1192}
1193
1194/*
1195 * Huge pages. Needs work.
1196 * Issues:
1197 * - Error on hugepage is contained in hugepage unit (not in raw page unit.)
1198 * To narrow down kill region to one page, we need to break up pmd.
1199 */
1200static int me_huge_page(struct page_state *ps, struct page *p)
1201{
1202 struct folio *folio = page_folio(p);
1203 int res;
1204 struct address_space *mapping;
1205 bool extra_pins = false;
1206
1207 mapping = folio_mapping(folio);
1208 if (mapping) {
1209 res = truncate_error_folio(folio, page_to_pfn(p), mapping);
1210 /* The page is kept in page cache. */
1211 extra_pins = true;
1212 folio_unlock(folio);
1213 } else {
1214 folio_unlock(folio);
1215 /*
1216 * migration entry prevents later access on error hugepage,
1217 * so we can free and dissolve it into buddy to save healthy
1218 * subpages.
1219 */
1220 folio_put(folio);
1221 if (__page_handle_poison(p) > 0) {
1222 page_ref_inc(p);
1223 res = MF_RECOVERED;
1224 } else {
1225 res = MF_FAILED;
1226 }
1227 }
1228
1229 if (has_extra_refcount(ps, p, extra_pins))
1230 res = MF_FAILED;
1231
1232 return res;
1233}
1234
1235/*
1236 * Various page states we can handle.
1237 *
1238 * A page state is defined by its current page->flags bits.
1239 * The table matches them in order and calls the right handler.
1240 *
1241 * This is quite tricky because we can access page at any time
1242 * in its live cycle, so all accesses have to be extremely careful.
1243 *
1244 * This is not complete. More states could be added.
1245 * For any missing state don't attempt recovery.
1246 */
1247
1248#define dirty (1UL << PG_dirty)
1249#define sc ((1UL << PG_swapcache) | (1UL << PG_swapbacked))
1250#define unevict (1UL << PG_unevictable)
1251#define mlock (1UL << PG_mlocked)
1252#define lru (1UL << PG_lru)
1253#define head (1UL << PG_head)
1254#define reserved (1UL << PG_reserved)
1255
1256static struct page_state error_states[] = {
1257 { reserved, reserved, MF_MSG_KERNEL, me_kernel },
1258 /*
1259 * free pages are specially detected outside this table:
1260 * PG_buddy pages only make a small fraction of all free pages.
1261 */
1262
1263 { head, head, MF_MSG_HUGE, me_huge_page },
1264
1265 { sc|dirty, sc|dirty, MF_MSG_DIRTY_SWAPCACHE, me_swapcache_dirty },
1266 { sc|dirty, sc, MF_MSG_CLEAN_SWAPCACHE, me_swapcache_clean },
1267
1268 { mlock|dirty, mlock|dirty, MF_MSG_DIRTY_MLOCKED_LRU, me_pagecache_dirty },
1269 { mlock|dirty, mlock, MF_MSG_CLEAN_MLOCKED_LRU, me_pagecache_clean },
1270
1271 { unevict|dirty, unevict|dirty, MF_MSG_DIRTY_UNEVICTABLE_LRU, me_pagecache_dirty },
1272 { unevict|dirty, unevict, MF_MSG_CLEAN_UNEVICTABLE_LRU, me_pagecache_clean },
1273
1274 { lru|dirty, lru|dirty, MF_MSG_DIRTY_LRU, me_pagecache_dirty },
1275 { lru|dirty, lru, MF_MSG_CLEAN_LRU, me_pagecache_clean },
1276
1277 /*
1278 * Catchall entry: must be at end.
1279 */
1280 { 0, 0, MF_MSG_UNKNOWN, me_unknown },
1281};
1282
1283#undef dirty
1284#undef sc
1285#undef unevict
1286#undef mlock
1287#undef lru
1288#undef head
1289#undef reserved
1290
1291static void update_per_node_mf_stats(unsigned long pfn,
1292 enum mf_result result)
1293{
1294 int nid = MAX_NUMNODES;
1295 struct memory_failure_stats *mf_stats = NULL;
1296
1297 nid = pfn_to_nid(pfn);
1298 if (unlikely(nid < 0 || nid >= MAX_NUMNODES)) {
1299 WARN_ONCE(1, "Memory failure: pfn=%#lx, invalid nid=%d", pfn, nid);
1300 return;
1301 }
1302
1303 mf_stats = &NODE_DATA(nid)->mf_stats;
1304 switch (result) {
1305 case MF_IGNORED:
1306 ++mf_stats->ignored;
1307 break;
1308 case MF_FAILED:
1309 ++mf_stats->failed;
1310 break;
1311 case MF_DELAYED:
1312 ++mf_stats->delayed;
1313 break;
1314 case MF_RECOVERED:
1315 ++mf_stats->recovered;
1316 break;
1317 default:
1318 WARN_ONCE(1, "Memory failure: mf_result=%d is not properly handled", result);
1319 break;
1320 }
1321 ++mf_stats->total;
1322}
1323
1324/*
1325 * "Dirty/Clean" indication is not 100% accurate due to the possibility of
1326 * setting PG_dirty outside page lock. See also comment above set_page_dirty().
1327 */
1328static int action_result(unsigned long pfn, enum mf_action_page_type type,
1329 enum mf_result result)
1330{
1331 trace_memory_failure_event(pfn, type, result);
1332
1333 num_poisoned_pages_inc(pfn);
1334
1335 update_per_node_mf_stats(pfn, result);
1336
1337 pr_err("%#lx: recovery action for %s: %s\n",
1338 pfn, action_page_types[type], action_name[result]);
1339
1340 return (result == MF_RECOVERED || result == MF_DELAYED) ? 0 : -EBUSY;
1341}
1342
1343static int page_action(struct page_state *ps, struct page *p,
1344 unsigned long pfn)
1345{
1346 int result;
1347
1348 /* page p should be unlocked after returning from ps->action(). */
1349 result = ps->action(ps, p);
1350
1351 /* Could do more checks here if page looks ok */
1352 /*
1353 * Could adjust zone counters here to correct for the missing page.
1354 */
1355
1356 return action_result(pfn, ps->type, result);
1357}
1358
1359static inline bool PageHWPoisonTakenOff(struct page *page)
1360{
1361 return PageHWPoison(page) && page_private(page) == MAGIC_HWPOISON;
1362}
1363
1364void SetPageHWPoisonTakenOff(struct page *page)
1365{
1366 set_page_private(page, MAGIC_HWPOISON);
1367}
1368
1369void ClearPageHWPoisonTakenOff(struct page *page)
1370{
1371 if (PageHWPoison(page))
1372 set_page_private(page, 0);
1373}
1374
1375/*
1376 * Return true if a page type of a given page is supported by hwpoison
1377 * mechanism (while handling could fail), otherwise false. This function
1378 * does not return true for hugetlb or device memory pages, so it's assumed
1379 * to be called only in the context where we never have such pages.
1380 */
1381static inline bool HWPoisonHandlable(struct page *page, unsigned long flags)
1382{
1383 if (PageSlab(page))
1384 return false;
1385
1386 /* Soft offline could migrate non-LRU movable pages */
1387 if ((flags & MF_SOFT_OFFLINE) && __PageMovable(page))
1388 return true;
1389
1390 return PageLRU(page) || is_free_buddy_page(page);
1391}
1392
1393static int __get_hwpoison_page(struct page *page, unsigned long flags)
1394{
1395 struct folio *folio = page_folio(page);
1396 int ret = 0;
1397 bool hugetlb = false;
1398
1399 ret = get_hwpoison_hugetlb_folio(folio, &hugetlb, false);
1400 if (hugetlb) {
1401 /* Make sure hugetlb demotion did not happen from under us. */
1402 if (folio == page_folio(page))
1403 return ret;
1404 if (ret > 0) {
1405 folio_put(folio);
1406 folio = page_folio(page);
1407 }
1408 }
1409
1410 /*
1411 * This check prevents from calling folio_try_get() for any
1412 * unsupported type of folio in order to reduce the risk of unexpected
1413 * races caused by taking a folio refcount.
1414 */
1415 if (!HWPoisonHandlable(&folio->page, flags))
1416 return -EBUSY;
1417
1418 if (folio_try_get(folio)) {
1419 if (folio == page_folio(page))
1420 return 1;
1421
1422 pr_info("%#lx cannot catch tail\n", page_to_pfn(page));
1423 folio_put(folio);
1424 }
1425
1426 return 0;
1427}
1428
1429#define GET_PAGE_MAX_RETRY_NUM 3
1430
1431static int get_any_page(struct page *p, unsigned long flags)
1432{
1433 int ret = 0, pass = 0;
1434 bool count_increased = false;
1435
1436 if (flags & MF_COUNT_INCREASED)
1437 count_increased = true;
1438
1439try_again:
1440 if (!count_increased) {
1441 ret = __get_hwpoison_page(p, flags);
1442 if (!ret) {
1443 if (page_count(p)) {
1444 /* We raced with an allocation, retry. */
1445 if (pass++ < GET_PAGE_MAX_RETRY_NUM)
1446 goto try_again;
1447 ret = -EBUSY;
1448 } else if (!PageHuge(p) && !is_free_buddy_page(p)) {
1449 /* We raced with put_page, retry. */
1450 if (pass++ < GET_PAGE_MAX_RETRY_NUM)
1451 goto try_again;
1452 ret = -EIO;
1453 }
1454 goto out;
1455 } else if (ret == -EBUSY) {
1456 /*
1457 * We raced with (possibly temporary) unhandlable
1458 * page, retry.
1459 */
1460 if (pass++ < 3) {
1461 shake_page(p);
1462 goto try_again;
1463 }
1464 ret = -EIO;
1465 goto out;
1466 }
1467 }
1468
1469 if (PageHuge(p) || HWPoisonHandlable(p, flags)) {
1470 ret = 1;
1471 } else {
1472 /*
1473 * A page we cannot handle. Check whether we can turn
1474 * it into something we can handle.
1475 */
1476 if (pass++ < GET_PAGE_MAX_RETRY_NUM) {
1477 put_page(p);
1478 shake_page(p);
1479 count_increased = false;
1480 goto try_again;
1481 }
1482 put_page(p);
1483 ret = -EIO;
1484 }
1485out:
1486 if (ret == -EIO)
1487 pr_err("%#lx: unhandlable page.\n", page_to_pfn(p));
1488
1489 return ret;
1490}
1491
1492static int __get_unpoison_page(struct page *page)
1493{
1494 struct folio *folio = page_folio(page);
1495 int ret = 0;
1496 bool hugetlb = false;
1497
1498 ret = get_hwpoison_hugetlb_folio(folio, &hugetlb, true);
1499 if (hugetlb) {
1500 /* Make sure hugetlb demotion did not happen from under us. */
1501 if (folio == page_folio(page))
1502 return ret;
1503 if (ret > 0)
1504 folio_put(folio);
1505 }
1506
1507 /*
1508 * PageHWPoisonTakenOff pages are not only marked as PG_hwpoison,
1509 * but also isolated from buddy freelist, so need to identify the
1510 * state and have to cancel both operations to unpoison.
1511 */
1512 if (PageHWPoisonTakenOff(page))
1513 return -EHWPOISON;
1514
1515 return get_page_unless_zero(page) ? 1 : 0;
1516}
1517
1518/**
1519 * get_hwpoison_page() - Get refcount for memory error handling
1520 * @p: Raw error page (hit by memory error)
1521 * @flags: Flags controlling behavior of error handling
1522 *
1523 * get_hwpoison_page() takes a page refcount of an error page to handle memory
1524 * error on it, after checking that the error page is in a well-defined state
1525 * (defined as a page-type we can successfully handle the memory error on it,
1526 * such as LRU page and hugetlb page).
1527 *
1528 * Memory error handling could be triggered at any time on any type of page,
1529 * so it's prone to race with typical memory management lifecycle (like
1530 * allocation and free). So to avoid such races, get_hwpoison_page() takes
1531 * extra care for the error page's state (as done in __get_hwpoison_page()),
1532 * and has some retry logic in get_any_page().
1533 *
1534 * When called from unpoison_memory(), the caller should already ensure that
1535 * the given page has PG_hwpoison. So it's never reused for other page
1536 * allocations, and __get_unpoison_page() never races with them.
1537 *
1538 * Return: 0 on failure or free buddy (hugetlb) page,
1539 * 1 on success for in-use pages in a well-defined state,
1540 * -EIO for pages on which we can not handle memory errors,
1541 * -EBUSY when get_hwpoison_page() has raced with page lifecycle
1542 * operations like allocation and free,
1543 * -EHWPOISON when the page is hwpoisoned and taken off from buddy.
1544 */
1545static int get_hwpoison_page(struct page *p, unsigned long flags)
1546{
1547 int ret;
1548
1549 zone_pcp_disable(page_zone(p));
1550 if (flags & MF_UNPOISON)
1551 ret = __get_unpoison_page(p);
1552 else
1553 ret = get_any_page(p, flags);
1554 zone_pcp_enable(page_zone(p));
1555
1556 return ret;
1557}
1558
1559int unmap_poisoned_folio(struct folio *folio, unsigned long pfn, bool must_kill)
1560{
1561 enum ttu_flags ttu = TTU_IGNORE_MLOCK | TTU_SYNC | TTU_HWPOISON;
1562 struct address_space *mapping;
1563
1564 if (folio_test_swapcache(folio)) {
1565 pr_err("%#lx: keeping poisoned page in swap cache\n", pfn);
1566 ttu &= ~TTU_HWPOISON;
1567 }
1568
1569 /*
1570 * Propagate the dirty bit from PTEs to struct page first, because we
1571 * need this to decide if we should kill or just drop the page.
1572 * XXX: the dirty test could be racy: set_page_dirty() may not always
1573 * be called inside page lock (it's recommended but not enforced).
1574 */
1575 mapping = folio_mapping(folio);
1576 if (!must_kill && !folio_test_dirty(folio) && mapping &&
1577 mapping_can_writeback(mapping)) {
1578 if (folio_mkclean(folio)) {
1579 folio_set_dirty(folio);
1580 } else {
1581 ttu &= ~TTU_HWPOISON;
1582 pr_info("%#lx: corrupted page was clean: dropped without side effects\n",
1583 pfn);
1584 }
1585 }
1586
1587 if (folio_test_hugetlb(folio) && !folio_test_anon(folio)) {
1588 /*
1589 * For hugetlb folios in shared mappings, try_to_unmap
1590 * could potentially call huge_pmd_unshare. Because of
1591 * this, take semaphore in write mode here and set
1592 * TTU_RMAP_LOCKED to indicate we have taken the lock
1593 * at this higher level.
1594 */
1595 mapping = hugetlb_folio_mapping_lock_write(folio);
1596 if (!mapping) {
1597 pr_info("%#lx: could not lock mapping for mapped hugetlb folio\n",
1598 folio_pfn(folio));
1599 return -EBUSY;
1600 }
1601
1602 try_to_unmap(folio, ttu|TTU_RMAP_LOCKED);
1603 i_mmap_unlock_write(mapping);
1604 } else {
1605 try_to_unmap(folio, ttu);
1606 }
1607
1608 return folio_mapped(folio) ? -EBUSY : 0;
1609}
1610
1611/*
1612 * Do all that is necessary to remove user space mappings. Unmap
1613 * the pages and send SIGBUS to the processes if the data was dirty.
1614 */
1615static bool hwpoison_user_mappings(struct folio *folio, struct page *p,
1616 unsigned long pfn, int flags)
1617{
1618 LIST_HEAD(tokill);
1619 bool unmap_success;
1620 int forcekill;
1621 bool mlocked = folio_test_mlocked(folio);
1622
1623 /*
1624 * Here we are interested only in user-mapped pages, so skip any
1625 * other types of pages.
1626 */
1627 if (folio_test_reserved(folio) || folio_test_slab(folio) ||
1628 folio_test_pgtable(folio) || folio_test_offline(folio))
1629 return true;
1630 if (!(folio_test_lru(folio) || folio_test_hugetlb(folio)))
1631 return true;
1632
1633 /*
1634 * This check implies we don't kill processes if their pages
1635 * are in the swap cache early. Those are always late kills.
1636 */
1637 if (!folio_mapped(folio))
1638 return true;
1639
1640 /*
1641 * First collect all the processes that have the page
1642 * mapped in dirty form. This has to be done before try_to_unmap,
1643 * because ttu takes the rmap data structures down.
1644 */
1645 collect_procs(folio, p, &tokill, flags & MF_ACTION_REQUIRED);
1646
1647 unmap_success = !unmap_poisoned_folio(folio, pfn, flags & MF_MUST_KILL);
1648 if (!unmap_success)
1649 pr_err("%#lx: failed to unmap page (folio mapcount=%d)\n",
1650 pfn, folio_mapcount(folio));
1651
1652 /*
1653 * try_to_unmap() might put mlocked page in lru cache, so call
1654 * shake_page() again to ensure that it's flushed.
1655 */
1656 if (mlocked)
1657 shake_folio(folio);
1658
1659 /*
1660 * Now that the dirty bit has been propagated to the
1661 * struct page and all unmaps done we can decide if
1662 * killing is needed or not. Only kill when the page
1663 * was dirty or the process is not restartable,
1664 * otherwise the tokill list is merely
1665 * freed. When there was a problem unmapping earlier
1666 * use a more force-full uncatchable kill to prevent
1667 * any accesses to the poisoned memory.
1668 */
1669 forcekill = folio_test_dirty(folio) || (flags & MF_MUST_KILL) ||
1670 !unmap_success;
1671 kill_procs(&tokill, forcekill, pfn, flags);
1672
1673 return unmap_success;
1674}
1675
1676static int identify_page_state(unsigned long pfn, struct page *p,
1677 unsigned long page_flags)
1678{
1679 struct page_state *ps;
1680
1681 /*
1682 * The first check uses the current page flags which may not have any
1683 * relevant information. The second check with the saved page flags is
1684 * carried out only if the first check can't determine the page status.
1685 */
1686 for (ps = error_states;; ps++)
1687 if ((p->flags & ps->mask) == ps->res)
1688 break;
1689
1690 page_flags |= (p->flags & (1UL << PG_dirty));
1691
1692 if (!ps->mask)
1693 for (ps = error_states;; ps++)
1694 if ((page_flags & ps->mask) == ps->res)
1695 break;
1696 return page_action(ps, p, pfn);
1697}
1698
1699/*
1700 * When 'release' is 'false', it means that if thp split has failed,
1701 * there is still more to do, hence the page refcount we took earlier
1702 * is still needed.
1703 */
1704static int try_to_split_thp_page(struct page *page, bool release)
1705{
1706 int ret;
1707
1708 lock_page(page);
1709 ret = split_huge_page(page);
1710 unlock_page(page);
1711
1712 if (ret && release)
1713 put_page(page);
1714
1715 return ret;
1716}
1717
1718static void unmap_and_kill(struct list_head *to_kill, unsigned long pfn,
1719 struct address_space *mapping, pgoff_t index, int flags)
1720{
1721 struct to_kill *tk;
1722 unsigned long size = 0;
1723
1724 list_for_each_entry(tk, to_kill, nd)
1725 if (tk->size_shift)
1726 size = max(size, 1UL << tk->size_shift);
1727
1728 if (size) {
1729 /*
1730 * Unmap the largest mapping to avoid breaking up device-dax
1731 * mappings which are constant size. The actual size of the
1732 * mapping being torn down is communicated in siginfo, see
1733 * kill_proc()
1734 */
1735 loff_t start = ((loff_t)index << PAGE_SHIFT) & ~(size - 1);
1736
1737 unmap_mapping_range(mapping, start, size, 0);
1738 }
1739
1740 kill_procs(to_kill, flags & MF_MUST_KILL, pfn, flags);
1741}
1742
1743/*
1744 * Only dev_pagemap pages get here, such as fsdax when the filesystem
1745 * either do not claim or fails to claim a hwpoison event, or devdax.
1746 * The fsdax pages are initialized per base page, and the devdax pages
1747 * could be initialized either as base pages, or as compound pages with
1748 * vmemmap optimization enabled. Devdax is simplistic in its dealing with
1749 * hwpoison, such that, if a subpage of a compound page is poisoned,
1750 * simply mark the compound head page is by far sufficient.
1751 */
1752static int mf_generic_kill_procs(unsigned long long pfn, int flags,
1753 struct dev_pagemap *pgmap)
1754{
1755 struct folio *folio = pfn_folio(pfn);
1756 LIST_HEAD(to_kill);
1757 dax_entry_t cookie;
1758 int rc = 0;
1759
1760 /*
1761 * Prevent the inode from being freed while we are interrogating
1762 * the address_space, typically this would be handled by
1763 * lock_page(), but dax pages do not use the page lock. This
1764 * also prevents changes to the mapping of this pfn until
1765 * poison signaling is complete.
1766 */
1767 cookie = dax_lock_folio(folio);
1768 if (!cookie)
1769 return -EBUSY;
1770
1771 if (hwpoison_filter(&folio->page)) {
1772 rc = -EOPNOTSUPP;
1773 goto unlock;
1774 }
1775
1776 switch (pgmap->type) {
1777 case MEMORY_DEVICE_PRIVATE:
1778 case MEMORY_DEVICE_COHERENT:
1779 /*
1780 * TODO: Handle device pages which may need coordination
1781 * with device-side memory.
1782 */
1783 rc = -ENXIO;
1784 goto unlock;
1785 default:
1786 break;
1787 }
1788
1789 /*
1790 * Use this flag as an indication that the dax page has been
1791 * remapped UC to prevent speculative consumption of poison.
1792 */
1793 SetPageHWPoison(&folio->page);
1794
1795 /*
1796 * Unlike System-RAM there is no possibility to swap in a
1797 * different physical page at a given virtual address, so all
1798 * userspace consumption of ZONE_DEVICE memory necessitates
1799 * SIGBUS (i.e. MF_MUST_KILL)
1800 */
1801 flags |= MF_ACTION_REQUIRED | MF_MUST_KILL;
1802 collect_procs(folio, &folio->page, &to_kill, true);
1803
1804 unmap_and_kill(&to_kill, pfn, folio->mapping, folio->index, flags);
1805unlock:
1806 dax_unlock_folio(folio, cookie);
1807 return rc;
1808}
1809
1810#ifdef CONFIG_FS_DAX
1811/**
1812 * mf_dax_kill_procs - Collect and kill processes who are using this file range
1813 * @mapping: address_space of the file in use
1814 * @index: start pgoff of the range within the file
1815 * @count: length of the range, in unit of PAGE_SIZE
1816 * @mf_flags: memory failure flags
1817 */
1818int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index,
1819 unsigned long count, int mf_flags)
1820{
1821 LIST_HEAD(to_kill);
1822 dax_entry_t cookie;
1823 struct page *page;
1824 size_t end = index + count;
1825 bool pre_remove = mf_flags & MF_MEM_PRE_REMOVE;
1826
1827 mf_flags |= MF_ACTION_REQUIRED | MF_MUST_KILL;
1828
1829 for (; index < end; index++) {
1830 page = NULL;
1831 cookie = dax_lock_mapping_entry(mapping, index, &page);
1832 if (!cookie)
1833 return -EBUSY;
1834 if (!page)
1835 goto unlock;
1836
1837 if (!pre_remove)
1838 SetPageHWPoison(page);
1839
1840 /*
1841 * The pre_remove case is revoking access, the memory is still
1842 * good and could theoretically be put back into service.
1843 */
1844 collect_procs_fsdax(page, mapping, index, &to_kill, pre_remove);
1845 unmap_and_kill(&to_kill, page_to_pfn(page), mapping,
1846 index, mf_flags);
1847unlock:
1848 dax_unlock_mapping_entry(mapping, index, cookie);
1849 }
1850 return 0;
1851}
1852EXPORT_SYMBOL_GPL(mf_dax_kill_procs);
1853#endif /* CONFIG_FS_DAX */
1854
1855#ifdef CONFIG_HUGETLB_PAGE
1856
1857/*
1858 * Struct raw_hwp_page represents information about "raw error page",
1859 * constructing singly linked list from ->_hugetlb_hwpoison field of folio.
1860 */
1861struct raw_hwp_page {
1862 struct llist_node node;
1863 struct page *page;
1864};
1865
1866static inline struct llist_head *raw_hwp_list_head(struct folio *folio)
1867{
1868 return (struct llist_head *)&folio->_hugetlb_hwpoison;
1869}
1870
1871bool is_raw_hwpoison_page_in_hugepage(struct page *page)
1872{
1873 struct llist_head *raw_hwp_head;
1874 struct raw_hwp_page *p;
1875 struct folio *folio = page_folio(page);
1876 bool ret = false;
1877
1878 if (!folio_test_hwpoison(folio))
1879 return false;
1880
1881 if (!folio_test_hugetlb(folio))
1882 return PageHWPoison(page);
1883
1884 /*
1885 * When RawHwpUnreliable is set, kernel lost track of which subpages
1886 * are HWPOISON. So return as if ALL subpages are HWPOISONed.
1887 */
1888 if (folio_test_hugetlb_raw_hwp_unreliable(folio))
1889 return true;
1890
1891 mutex_lock(&mf_mutex);
1892
1893 raw_hwp_head = raw_hwp_list_head(folio);
1894 llist_for_each_entry(p, raw_hwp_head->first, node) {
1895 if (page == p->page) {
1896 ret = true;
1897 break;
1898 }
1899 }
1900
1901 mutex_unlock(&mf_mutex);
1902
1903 return ret;
1904}
1905
1906static unsigned long __folio_free_raw_hwp(struct folio *folio, bool move_flag)
1907{
1908 struct llist_node *head;
1909 struct raw_hwp_page *p, *next;
1910 unsigned long count = 0;
1911
1912 head = llist_del_all(raw_hwp_list_head(folio));
1913 llist_for_each_entry_safe(p, next, head, node) {
1914 if (move_flag)
1915 SetPageHWPoison(p->page);
1916 else
1917 num_poisoned_pages_sub(page_to_pfn(p->page), 1);
1918 kfree(p);
1919 count++;
1920 }
1921 return count;
1922}
1923
1924static int folio_set_hugetlb_hwpoison(struct folio *folio, struct page *page)
1925{
1926 struct llist_head *head;
1927 struct raw_hwp_page *raw_hwp;
1928 struct raw_hwp_page *p;
1929 int ret = folio_test_set_hwpoison(folio) ? -EHWPOISON : 0;
1930
1931 /*
1932 * Once the hwpoison hugepage has lost reliable raw error info,
1933 * there is little meaning to keep additional error info precisely,
1934 * so skip to add additional raw error info.
1935 */
1936 if (folio_test_hugetlb_raw_hwp_unreliable(folio))
1937 return -EHWPOISON;
1938 head = raw_hwp_list_head(folio);
1939 llist_for_each_entry(p, head->first, node) {
1940 if (p->page == page)
1941 return -EHWPOISON;
1942 }
1943
1944 raw_hwp = kmalloc(sizeof(struct raw_hwp_page), GFP_ATOMIC);
1945 if (raw_hwp) {
1946 raw_hwp->page = page;
1947 llist_add(&raw_hwp->node, head);
1948 /* the first error event will be counted in action_result(). */
1949 if (ret)
1950 num_poisoned_pages_inc(page_to_pfn(page));
1951 } else {
1952 /*
1953 * Failed to save raw error info. We no longer trace all
1954 * hwpoisoned subpages, and we need refuse to free/dissolve
1955 * this hwpoisoned hugepage.
1956 */
1957 folio_set_hugetlb_raw_hwp_unreliable(folio);
1958 /*
1959 * Once hugetlb_raw_hwp_unreliable is set, raw_hwp_page is not
1960 * used any more, so free it.
1961 */
1962 __folio_free_raw_hwp(folio, false);
1963 }
1964 return ret;
1965}
1966
1967static unsigned long folio_free_raw_hwp(struct folio *folio, bool move_flag)
1968{
1969 /*
1970 * hugetlb_vmemmap_optimized hugepages can't be freed because struct
1971 * pages for tail pages are required but they don't exist.
1972 */
1973 if (move_flag && folio_test_hugetlb_vmemmap_optimized(folio))
1974 return 0;
1975
1976 /*
1977 * hugetlb_raw_hwp_unreliable hugepages shouldn't be unpoisoned by
1978 * definition.
1979 */
1980 if (folio_test_hugetlb_raw_hwp_unreliable(folio))
1981 return 0;
1982
1983 return __folio_free_raw_hwp(folio, move_flag);
1984}
1985
1986void folio_clear_hugetlb_hwpoison(struct folio *folio)
1987{
1988 if (folio_test_hugetlb_raw_hwp_unreliable(folio))
1989 return;
1990 if (folio_test_hugetlb_vmemmap_optimized(folio))
1991 return;
1992 folio_clear_hwpoison(folio);
1993 folio_free_raw_hwp(folio, true);
1994}
1995
1996/*
1997 * Called from hugetlb code with hugetlb_lock held.
1998 *
1999 * Return values:
2000 * 0 - free hugepage
2001 * 1 - in-use hugepage
2002 * 2 - not a hugepage
2003 * -EBUSY - the hugepage is busy (try to retry)
2004 * -EHWPOISON - the hugepage is already hwpoisoned
2005 */
2006int __get_huge_page_for_hwpoison(unsigned long pfn, int flags,
2007 bool *migratable_cleared)
2008{
2009 struct page *page = pfn_to_page(pfn);
2010 struct folio *folio = page_folio(page);
2011 int ret = 2; /* fallback to normal page handling */
2012 bool count_increased = false;
2013
2014 if (!folio_test_hugetlb(folio))
2015 goto out;
2016
2017 if (flags & MF_COUNT_INCREASED) {
2018 ret = 1;
2019 count_increased = true;
2020 } else if (folio_test_hugetlb_freed(folio)) {
2021 ret = 0;
2022 } else if (folio_test_hugetlb_migratable(folio)) {
2023 ret = folio_try_get(folio);
2024 if (ret)
2025 count_increased = true;
2026 } else {
2027 ret = -EBUSY;
2028 if (!(flags & MF_NO_RETRY))
2029 goto out;
2030 }
2031
2032 if (folio_set_hugetlb_hwpoison(folio, page)) {
2033 ret = -EHWPOISON;
2034 goto out;
2035 }
2036
2037 /*
2038 * Clearing hugetlb_migratable for hwpoisoned hugepages to prevent them
2039 * from being migrated by memory hotremove.
2040 */
2041 if (count_increased && folio_test_hugetlb_migratable(folio)) {
2042 folio_clear_hugetlb_migratable(folio);
2043 *migratable_cleared = true;
2044 }
2045
2046 return ret;
2047out:
2048 if (count_increased)
2049 folio_put(folio);
2050 return ret;
2051}
2052
2053/*
2054 * Taking refcount of hugetlb pages needs extra care about race conditions
2055 * with basic operations like hugepage allocation/free/demotion.
2056 * So some of prechecks for hwpoison (pinning, and testing/setting
2057 * PageHWPoison) should be done in single hugetlb_lock range.
2058 */
2059static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb)
2060{
2061 int res;
2062 struct page *p = pfn_to_page(pfn);
2063 struct folio *folio;
2064 unsigned long page_flags;
2065 bool migratable_cleared = false;
2066
2067 *hugetlb = 1;
2068retry:
2069 res = get_huge_page_for_hwpoison(pfn, flags, &migratable_cleared);
2070 if (res == 2) { /* fallback to normal page handling */
2071 *hugetlb = 0;
2072 return 0;
2073 } else if (res == -EHWPOISON) {
2074 pr_err("%#lx: already hardware poisoned\n", pfn);
2075 if (flags & MF_ACTION_REQUIRED) {
2076 folio = page_folio(p);
2077 res = kill_accessing_process(current, folio_pfn(folio), flags);
2078 action_result(pfn, MF_MSG_ALREADY_POISONED, MF_FAILED);
2079 }
2080 return res;
2081 } else if (res == -EBUSY) {
2082 if (!(flags & MF_NO_RETRY)) {
2083 flags |= MF_NO_RETRY;
2084 goto retry;
2085 }
2086 return action_result(pfn, MF_MSG_GET_HWPOISON, MF_IGNORED);
2087 }
2088
2089 folio = page_folio(p);
2090 folio_lock(folio);
2091
2092 if (hwpoison_filter(p)) {
2093 folio_clear_hugetlb_hwpoison(folio);
2094 if (migratable_cleared)
2095 folio_set_hugetlb_migratable(folio);
2096 folio_unlock(folio);
2097 if (res == 1)
2098 folio_put(folio);
2099 return -EOPNOTSUPP;
2100 }
2101
2102 /*
2103 * Handling free hugepage. The possible race with hugepage allocation
2104 * or demotion can be prevented by PageHWPoison flag.
2105 */
2106 if (res == 0) {
2107 folio_unlock(folio);
2108 if (__page_handle_poison(p) > 0) {
2109 page_ref_inc(p);
2110 res = MF_RECOVERED;
2111 } else {
2112 res = MF_FAILED;
2113 }
2114 return action_result(pfn, MF_MSG_FREE_HUGE, res);
2115 }
2116
2117 page_flags = folio->flags;
2118
2119 if (!hwpoison_user_mappings(folio, p, pfn, flags)) {
2120 folio_unlock(folio);
2121 return action_result(pfn, MF_MSG_UNMAP_FAILED, MF_FAILED);
2122 }
2123
2124 return identify_page_state(pfn, p, page_flags);
2125}
2126
2127#else
2128static inline int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb)
2129{
2130 return 0;
2131}
2132
2133static inline unsigned long folio_free_raw_hwp(struct folio *folio, bool flag)
2134{
2135 return 0;
2136}
2137#endif /* CONFIG_HUGETLB_PAGE */
2138
2139/* Drop the extra refcount in case we come from madvise() */
2140static void put_ref_page(unsigned long pfn, int flags)
2141{
2142 if (!(flags & MF_COUNT_INCREASED))
2143 return;
2144
2145 put_page(pfn_to_page(pfn));
2146}
2147
2148static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
2149 struct dev_pagemap *pgmap)
2150{
2151 int rc = -ENXIO;
2152
2153 /* device metadata space is not recoverable */
2154 if (!pgmap_pfn_valid(pgmap, pfn))
2155 goto out;
2156
2157 /*
2158 * Call driver's implementation to handle the memory failure, otherwise
2159 * fall back to generic handler.
2160 */
2161 if (pgmap_has_memory_failure(pgmap)) {
2162 rc = pgmap->ops->memory_failure(pgmap, pfn, 1, flags);
2163 /*
2164 * Fall back to generic handler too if operation is not
2165 * supported inside the driver/device/filesystem.
2166 */
2167 if (rc != -EOPNOTSUPP)
2168 goto out;
2169 }
2170
2171 rc = mf_generic_kill_procs(pfn, flags, pgmap);
2172out:
2173 /* drop pgmap ref acquired in caller */
2174 put_dev_pagemap(pgmap);
2175 if (rc != -EOPNOTSUPP)
2176 action_result(pfn, MF_MSG_DAX, rc ? MF_FAILED : MF_RECOVERED);
2177 return rc;
2178}
2179
2180/*
2181 * The calling condition is as such: thp split failed, page might have
2182 * been RDMA pinned, not much can be done for recovery.
2183 * But a SIGBUS should be delivered with vaddr provided so that the user
2184 * application has a chance to recover. Also, application processes'
2185 * election for MCE early killed will be honored.
2186 */
2187static void kill_procs_now(struct page *p, unsigned long pfn, int flags,
2188 struct folio *folio)
2189{
2190 LIST_HEAD(tokill);
2191
2192 collect_procs(folio, p, &tokill, flags & MF_ACTION_REQUIRED);
2193 kill_procs(&tokill, true, pfn, flags);
2194}
2195
2196/**
2197 * memory_failure - Handle memory failure of a page.
2198 * @pfn: Page Number of the corrupted page
2199 * @flags: fine tune action taken
2200 *
2201 * This function is called by the low level machine check code
2202 * of an architecture when it detects hardware memory corruption
2203 * of a page. It tries its best to recover, which includes
2204 * dropping pages, killing processes etc.
2205 *
2206 * The function is primarily of use for corruptions that
2207 * happen outside the current execution context (e.g. when
2208 * detected by a background scrubber)
2209 *
2210 * Must run in process context (e.g. a work queue) with interrupts
2211 * enabled and no spinlocks held.
2212 *
2213 * Return: 0 for successfully handled the memory error,
2214 * -EOPNOTSUPP for hwpoison_filter() filtered the error event,
2215 * < 0(except -EOPNOTSUPP) on failure.
2216 */
2217int memory_failure(unsigned long pfn, int flags)
2218{
2219 struct page *p;
2220 struct folio *folio;
2221 struct dev_pagemap *pgmap;
2222 int res = 0;
2223 unsigned long page_flags;
2224 bool retry = true;
2225 int hugetlb = 0;
2226
2227 if (!sysctl_memory_failure_recovery)
2228 panic("Memory failure on page %lx", pfn);
2229
2230 mutex_lock(&mf_mutex);
2231
2232 if (!(flags & MF_SW_SIMULATED))
2233 hw_memory_failure = true;
2234
2235 p = pfn_to_online_page(pfn);
2236 if (!p) {
2237 res = arch_memory_failure(pfn, flags);
2238 if (res == 0)
2239 goto unlock_mutex;
2240
2241 if (pfn_valid(pfn)) {
2242 pgmap = get_dev_pagemap(pfn, NULL);
2243 put_ref_page(pfn, flags);
2244 if (pgmap) {
2245 res = memory_failure_dev_pagemap(pfn, flags,
2246 pgmap);
2247 goto unlock_mutex;
2248 }
2249 }
2250 pr_err("%#lx: memory outside kernel control\n", pfn);
2251 res = -ENXIO;
2252 goto unlock_mutex;
2253 }
2254
2255try_again:
2256 res = try_memory_failure_hugetlb(pfn, flags, &hugetlb);
2257 if (hugetlb)
2258 goto unlock_mutex;
2259
2260 if (TestSetPageHWPoison(p)) {
2261 pr_err("%#lx: already hardware poisoned\n", pfn);
2262 res = -EHWPOISON;
2263 if (flags & MF_ACTION_REQUIRED)
2264 res = kill_accessing_process(current, pfn, flags);
2265 if (flags & MF_COUNT_INCREASED)
2266 put_page(p);
2267 action_result(pfn, MF_MSG_ALREADY_POISONED, MF_FAILED);
2268 goto unlock_mutex;
2269 }
2270
2271 /*
2272 * We need/can do nothing about count=0 pages.
2273 * 1) it's a free page, and therefore in safe hand:
2274 * check_new_page() will be the gate keeper.
2275 * 2) it's part of a non-compound high order page.
2276 * Implies some kernel user: cannot stop them from
2277 * R/W the page; let's pray that the page has been
2278 * used and will be freed some time later.
2279 * In fact it's dangerous to directly bump up page count from 0,
2280 * that may make page_ref_freeze()/page_ref_unfreeze() mismatch.
2281 */
2282 if (!(flags & MF_COUNT_INCREASED)) {
2283 res = get_hwpoison_page(p, flags);
2284 if (!res) {
2285 if (is_free_buddy_page(p)) {
2286 if (take_page_off_buddy(p)) {
2287 page_ref_inc(p);
2288 res = MF_RECOVERED;
2289 } else {
2290 /* We lost the race, try again */
2291 if (retry) {
2292 ClearPageHWPoison(p);
2293 retry = false;
2294 goto try_again;
2295 }
2296 res = MF_FAILED;
2297 }
2298 res = action_result(pfn, MF_MSG_BUDDY, res);
2299 } else {
2300 res = action_result(pfn, MF_MSG_KERNEL_HIGH_ORDER, MF_IGNORED);
2301 }
2302 goto unlock_mutex;
2303 } else if (res < 0) {
2304 res = action_result(pfn, MF_MSG_GET_HWPOISON, MF_IGNORED);
2305 goto unlock_mutex;
2306 }
2307 }
2308
2309 folio = page_folio(p);
2310
2311 /* filter pages that are protected from hwpoison test by users */
2312 folio_lock(folio);
2313 if (hwpoison_filter(p)) {
2314 ClearPageHWPoison(p);
2315 folio_unlock(folio);
2316 folio_put(folio);
2317 res = -EOPNOTSUPP;
2318 goto unlock_mutex;
2319 }
2320 folio_unlock(folio);
2321
2322 if (folio_test_large(folio)) {
2323 /*
2324 * The flag must be set after the refcount is bumped
2325 * otherwise it may race with THP split.
2326 * And the flag can't be set in get_hwpoison_page() since
2327 * it is called by soft offline too and it is just called
2328 * for !MF_COUNT_INCREASED. So here seems to be the best
2329 * place.
2330 *
2331 * Don't need care about the above error handling paths for
2332 * get_hwpoison_page() since they handle either free page
2333 * or unhandlable page. The refcount is bumped iff the
2334 * page is a valid handlable page.
2335 */
2336 folio_set_has_hwpoisoned(folio);
2337 if (try_to_split_thp_page(p, false) < 0) {
2338 res = -EHWPOISON;
2339 kill_procs_now(p, pfn, flags, folio);
2340 put_page(p);
2341 action_result(pfn, MF_MSG_UNSPLIT_THP, MF_FAILED);
2342 goto unlock_mutex;
2343 }
2344 VM_BUG_ON_PAGE(!page_count(p), p);
2345 folio = page_folio(p);
2346 }
2347
2348 /*
2349 * We ignore non-LRU pages for good reasons.
2350 * - PG_locked is only well defined for LRU pages and a few others
2351 * - to avoid races with __SetPageLocked()
2352 * - to avoid races with __SetPageSlab*() (and more non-atomic ops)
2353 * The check (unnecessarily) ignores LRU pages being isolated and
2354 * walked by the page reclaim code, however that's not a big loss.
2355 */
2356 shake_folio(folio);
2357
2358 folio_lock(folio);
2359
2360 /*
2361 * We're only intended to deal with the non-Compound page here.
2362 * The page cannot become compound pages again as folio has been
2363 * splited and extra refcnt is held.
2364 */
2365 WARN_ON(folio_test_large(folio));
2366
2367 /*
2368 * We use page flags to determine what action should be taken, but
2369 * the flags can be modified by the error containment action. One
2370 * example is an mlocked page, where PG_mlocked is cleared by
2371 * folio_remove_rmap_*() in try_to_unmap_one(). So to determine page
2372 * status correctly, we save a copy of the page flags at this time.
2373 */
2374 page_flags = folio->flags;
2375
2376 /*
2377 * __munlock_folio() may clear a writeback folio's LRU flag without
2378 * the folio lock. We need to wait for writeback completion for this
2379 * folio or it may trigger a vfs BUG while evicting inode.
2380 */
2381 if (!folio_test_lru(folio) && !folio_test_writeback(folio))
2382 goto identify_page_state;
2383
2384 /*
2385 * It's very difficult to mess with pages currently under IO
2386 * and in many cases impossible, so we just avoid it here.
2387 */
2388 folio_wait_writeback(folio);
2389
2390 /*
2391 * Now take care of user space mappings.
2392 * Abort on fail: __filemap_remove_folio() assumes unmapped page.
2393 */
2394 if (!hwpoison_user_mappings(folio, p, pfn, flags)) {
2395 res = action_result(pfn, MF_MSG_UNMAP_FAILED, MF_FAILED);
2396 goto unlock_page;
2397 }
2398
2399 /*
2400 * Torn down by someone else?
2401 */
2402 if (folio_test_lru(folio) && !folio_test_swapcache(folio) &&
2403 folio->mapping == NULL) {
2404 res = action_result(pfn, MF_MSG_TRUNCATED_LRU, MF_IGNORED);
2405 goto unlock_page;
2406 }
2407
2408identify_page_state:
2409 res = identify_page_state(pfn, p, page_flags);
2410 mutex_unlock(&mf_mutex);
2411 return res;
2412unlock_page:
2413 folio_unlock(folio);
2414unlock_mutex:
2415 mutex_unlock(&mf_mutex);
2416 return res;
2417}
2418EXPORT_SYMBOL_GPL(memory_failure);
2419
2420#define MEMORY_FAILURE_FIFO_ORDER 4
2421#define MEMORY_FAILURE_FIFO_SIZE (1 << MEMORY_FAILURE_FIFO_ORDER)
2422
2423struct memory_failure_entry {
2424 unsigned long pfn;
2425 int flags;
2426};
2427
2428struct memory_failure_cpu {
2429 DECLARE_KFIFO(fifo, struct memory_failure_entry,
2430 MEMORY_FAILURE_FIFO_SIZE);
2431 raw_spinlock_t lock;
2432 struct work_struct work;
2433};
2434
2435static DEFINE_PER_CPU(struct memory_failure_cpu, memory_failure_cpu);
2436
2437/**
2438 * memory_failure_queue - Schedule handling memory failure of a page.
2439 * @pfn: Page Number of the corrupted page
2440 * @flags: Flags for memory failure handling
2441 *
2442 * This function is called by the low level hardware error handler
2443 * when it detects hardware memory corruption of a page. It schedules
2444 * the recovering of error page, including dropping pages, killing
2445 * processes etc.
2446 *
2447 * The function is primarily of use for corruptions that
2448 * happen outside the current execution context (e.g. when
2449 * detected by a background scrubber)
2450 *
2451 * Can run in IRQ context.
2452 */
2453void memory_failure_queue(unsigned long pfn, int flags)
2454{
2455 struct memory_failure_cpu *mf_cpu;
2456 unsigned long proc_flags;
2457 bool buffer_overflow;
2458 struct memory_failure_entry entry = {
2459 .pfn = pfn,
2460 .flags = flags,
2461 };
2462
2463 mf_cpu = &get_cpu_var(memory_failure_cpu);
2464 raw_spin_lock_irqsave(&mf_cpu->lock, proc_flags);
2465 buffer_overflow = !kfifo_put(&mf_cpu->fifo, entry);
2466 if (!buffer_overflow)
2467 schedule_work_on(smp_processor_id(), &mf_cpu->work);
2468 raw_spin_unlock_irqrestore(&mf_cpu->lock, proc_flags);
2469 put_cpu_var(memory_failure_cpu);
2470 if (buffer_overflow)
2471 pr_err("buffer overflow when queuing memory failure at %#lx\n",
2472 pfn);
2473}
2474EXPORT_SYMBOL_GPL(memory_failure_queue);
2475
2476static void memory_failure_work_func(struct work_struct *work)
2477{
2478 struct memory_failure_cpu *mf_cpu;
2479 struct memory_failure_entry entry = { 0, };
2480 unsigned long proc_flags;
2481 int gotten;
2482
2483 mf_cpu = container_of(work, struct memory_failure_cpu, work);
2484 for (;;) {
2485 raw_spin_lock_irqsave(&mf_cpu->lock, proc_flags);
2486 gotten = kfifo_get(&mf_cpu->fifo, &entry);
2487 raw_spin_unlock_irqrestore(&mf_cpu->lock, proc_flags);
2488 if (!gotten)
2489 break;
2490 if (entry.flags & MF_SOFT_OFFLINE)
2491 soft_offline_page(entry.pfn, entry.flags);
2492 else
2493 memory_failure(entry.pfn, entry.flags);
2494 }
2495}
2496
2497/*
2498 * Process memory_failure work queued on the specified CPU.
2499 * Used to avoid return-to-userspace racing with the memory_failure workqueue.
2500 */
2501void memory_failure_queue_kick(int cpu)
2502{
2503 struct memory_failure_cpu *mf_cpu;
2504
2505 mf_cpu = &per_cpu(memory_failure_cpu, cpu);
2506 cancel_work_sync(&mf_cpu->work);
2507 memory_failure_work_func(&mf_cpu->work);
2508}
2509
2510static int __init memory_failure_init(void)
2511{
2512 struct memory_failure_cpu *mf_cpu;
2513 int cpu;
2514
2515 for_each_possible_cpu(cpu) {
2516 mf_cpu = &per_cpu(memory_failure_cpu, cpu);
2517 raw_spin_lock_init(&mf_cpu->lock);
2518 INIT_KFIFO(mf_cpu->fifo);
2519 INIT_WORK(&mf_cpu->work, memory_failure_work_func);
2520 }
2521
2522 register_sysctl_init("vm", memory_failure_table);
2523
2524 return 0;
2525}
2526core_initcall(memory_failure_init);
2527
2528#undef pr_fmt
2529#define pr_fmt(fmt) "Unpoison: " fmt
2530#define unpoison_pr_info(fmt, pfn, rs) \
2531({ \
2532 if (__ratelimit(rs)) \
2533 pr_info(fmt, pfn); \
2534})
2535
2536/**
2537 * unpoison_memory - Unpoison a previously poisoned page
2538 * @pfn: Page number of the to be unpoisoned page
2539 *
2540 * Software-unpoison a page that has been poisoned by
2541 * memory_failure() earlier.
2542 *
2543 * This is only done on the software-level, so it only works
2544 * for linux injected failures, not real hardware failures
2545 *
2546 * Returns 0 for success, otherwise -errno.
2547 */
2548int unpoison_memory(unsigned long pfn)
2549{
2550 struct folio *folio;
2551 struct page *p;
2552 int ret = -EBUSY, ghp;
2553 unsigned long count;
2554 bool huge = false;
2555 static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL,
2556 DEFAULT_RATELIMIT_BURST);
2557
2558 if (!pfn_valid(pfn))
2559 return -ENXIO;
2560
2561 p = pfn_to_page(pfn);
2562 folio = page_folio(p);
2563
2564 mutex_lock(&mf_mutex);
2565
2566 if (hw_memory_failure) {
2567 unpoison_pr_info("%#lx: disabled after HW memory failure\n",
2568 pfn, &unpoison_rs);
2569 ret = -EOPNOTSUPP;
2570 goto unlock_mutex;
2571 }
2572
2573 if (is_huge_zero_folio(folio)) {
2574 unpoison_pr_info("%#lx: huge zero page is not supported\n",
2575 pfn, &unpoison_rs);
2576 ret = -EOPNOTSUPP;
2577 goto unlock_mutex;
2578 }
2579
2580 if (!PageHWPoison(p)) {
2581 unpoison_pr_info("%#lx: page was already unpoisoned\n",
2582 pfn, &unpoison_rs);
2583 goto unlock_mutex;
2584 }
2585
2586 if (folio_ref_count(folio) > 1) {
2587 unpoison_pr_info("%#lx: someone grabs the hwpoison page\n",
2588 pfn, &unpoison_rs);
2589 goto unlock_mutex;
2590 }
2591
2592 if (folio_test_slab(folio) || folio_test_pgtable(folio) ||
2593 folio_test_reserved(folio) || folio_test_offline(folio))
2594 goto unlock_mutex;
2595
2596 if (folio_mapped(folio)) {
2597 unpoison_pr_info("%#lx: someone maps the hwpoison page\n",
2598 pfn, &unpoison_rs);
2599 goto unlock_mutex;
2600 }
2601
2602 if (folio_mapping(folio)) {
2603 unpoison_pr_info("%#lx: the hwpoison page has non-NULL mapping\n",
2604 pfn, &unpoison_rs);
2605 goto unlock_mutex;
2606 }
2607
2608 ghp = get_hwpoison_page(p, MF_UNPOISON);
2609 if (!ghp) {
2610 if (folio_test_hugetlb(folio)) {
2611 huge = true;
2612 count = folio_free_raw_hwp(folio, false);
2613 if (count == 0)
2614 goto unlock_mutex;
2615 }
2616 ret = folio_test_clear_hwpoison(folio) ? 0 : -EBUSY;
2617 } else if (ghp < 0) {
2618 if (ghp == -EHWPOISON) {
2619 ret = put_page_back_buddy(p) ? 0 : -EBUSY;
2620 } else {
2621 ret = ghp;
2622 unpoison_pr_info("%#lx: failed to grab page\n",
2623 pfn, &unpoison_rs);
2624 }
2625 } else {
2626 if (folio_test_hugetlb(folio)) {
2627 huge = true;
2628 count = folio_free_raw_hwp(folio, false);
2629 if (count == 0) {
2630 folio_put(folio);
2631 goto unlock_mutex;
2632 }
2633 }
2634
2635 folio_put(folio);
2636 if (TestClearPageHWPoison(p)) {
2637 folio_put(folio);
2638 ret = 0;
2639 }
2640 }
2641
2642unlock_mutex:
2643 mutex_unlock(&mf_mutex);
2644 if (!ret) {
2645 if (!huge)
2646 num_poisoned_pages_sub(pfn, 1);
2647 unpoison_pr_info("%#lx: software-unpoisoned page\n",
2648 page_to_pfn(p), &unpoison_rs);
2649 }
2650 return ret;
2651}
2652EXPORT_SYMBOL(unpoison_memory);
2653
2654#undef pr_fmt
2655#define pr_fmt(fmt) "Soft offline: " fmt
2656
2657/*
2658 * soft_offline_in_use_page handles hugetlb-pages and non-hugetlb pages.
2659 * If the page is a non-dirty unmapped page-cache page, it simply invalidates.
2660 * If the page is mapped, it migrates the contents over.
2661 */
2662static int soft_offline_in_use_page(struct page *page)
2663{
2664 long ret = 0;
2665 unsigned long pfn = page_to_pfn(page);
2666 struct folio *folio = page_folio(page);
2667 char const *msg_page[] = {"page", "hugepage"};
2668 bool huge = folio_test_hugetlb(folio);
2669 bool isolated;
2670 LIST_HEAD(pagelist);
2671 struct migration_target_control mtc = {
2672 .nid = NUMA_NO_NODE,
2673 .gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL,
2674 .reason = MR_MEMORY_FAILURE,
2675 };
2676
2677 if (!huge && folio_test_large(folio)) {
2678 if (try_to_split_thp_page(page, true)) {
2679 pr_info("%#lx: thp split failed\n", pfn);
2680 return -EBUSY;
2681 }
2682 folio = page_folio(page);
2683 }
2684
2685 folio_lock(folio);
2686 if (!huge)
2687 folio_wait_writeback(folio);
2688 if (PageHWPoison(page)) {
2689 folio_unlock(folio);
2690 folio_put(folio);
2691 pr_info("%#lx: page already poisoned\n", pfn);
2692 return 0;
2693 }
2694
2695 if (!huge && folio_test_lru(folio) && !folio_test_swapcache(folio))
2696 /*
2697 * Try to invalidate first. This should work for
2698 * non dirty unmapped page cache pages.
2699 */
2700 ret = mapping_evict_folio(folio_mapping(folio), folio);
2701 folio_unlock(folio);
2702
2703 if (ret) {
2704 pr_info("%#lx: invalidated\n", pfn);
2705 page_handle_poison(page, false, true);
2706 return 0;
2707 }
2708
2709 isolated = isolate_folio_to_list(folio, &pagelist);
2710
2711 /*
2712 * If we succeed to isolate the folio, we grabbed another refcount on
2713 * the folio, so we can safely drop the one we got from get_any_page().
2714 * If we failed to isolate the folio, it means that we cannot go further
2715 * and we will return an error, so drop the reference we got from
2716 * get_any_page() as well.
2717 */
2718 folio_put(folio);
2719
2720 if (isolated) {
2721 ret = migrate_pages(&pagelist, alloc_migration_target, NULL,
2722 (unsigned long)&mtc, MIGRATE_SYNC, MR_MEMORY_FAILURE, NULL);
2723 if (!ret) {
2724 bool release = !huge;
2725
2726 if (!page_handle_poison(page, huge, release))
2727 ret = -EBUSY;
2728 } else {
2729 if (!list_empty(&pagelist))
2730 putback_movable_pages(&pagelist);
2731
2732 pr_info("%#lx: %s migration failed %ld, type %pGp\n",
2733 pfn, msg_page[huge], ret, &page->flags);
2734 if (ret > 0)
2735 ret = -EBUSY;
2736 }
2737 } else {
2738 pr_info("%#lx: %s isolation failed, page count %d, type %pGp\n",
2739 pfn, msg_page[huge], page_count(page), &page->flags);
2740 ret = -EBUSY;
2741 }
2742 return ret;
2743}
2744
2745/**
2746 * soft_offline_page - Soft offline a page.
2747 * @pfn: pfn to soft-offline
2748 * @flags: flags. Same as memory_failure().
2749 *
2750 * Returns 0 on success,
2751 * -EOPNOTSUPP for hwpoison_filter() filtered the error event, or
2752 * disabled by /proc/sys/vm/enable_soft_offline,
2753 * < 0 otherwise negated errno.
2754 *
2755 * Soft offline a page, by migration or invalidation,
2756 * without killing anything. This is for the case when
2757 * a page is not corrupted yet (so it's still valid to access),
2758 * but has had a number of corrected errors and is better taken
2759 * out.
2760 *
2761 * The actual policy on when to do that is maintained by
2762 * user space.
2763 *
2764 * This should never impact any application or cause data loss,
2765 * however it might take some time.
2766 *
2767 * This is not a 100% solution for all memory, but tries to be
2768 * ``good enough'' for the majority of memory.
2769 */
2770int soft_offline_page(unsigned long pfn, int flags)
2771{
2772 int ret;
2773 bool try_again = true;
2774 struct page *page;
2775
2776 if (!pfn_valid(pfn)) {
2777 WARN_ON_ONCE(flags & MF_COUNT_INCREASED);
2778 return -ENXIO;
2779 }
2780
2781 /* Only online pages can be soft-offlined (esp., not ZONE_DEVICE). */
2782 page = pfn_to_online_page(pfn);
2783 if (!page) {
2784 put_ref_page(pfn, flags);
2785 return -EIO;
2786 }
2787
2788 if (!sysctl_enable_soft_offline) {
2789 pr_info_once("disabled by /proc/sys/vm/enable_soft_offline\n");
2790 put_ref_page(pfn, flags);
2791 return -EOPNOTSUPP;
2792 }
2793
2794 mutex_lock(&mf_mutex);
2795
2796 if (PageHWPoison(page)) {
2797 pr_info("%#lx: page already poisoned\n", pfn);
2798 put_ref_page(pfn, flags);
2799 mutex_unlock(&mf_mutex);
2800 return 0;
2801 }
2802
2803retry:
2804 get_online_mems();
2805 ret = get_hwpoison_page(page, flags | MF_SOFT_OFFLINE);
2806 put_online_mems();
2807
2808 if (hwpoison_filter(page)) {
2809 if (ret > 0)
2810 put_page(page);
2811
2812 mutex_unlock(&mf_mutex);
2813 return -EOPNOTSUPP;
2814 }
2815
2816 if (ret > 0) {
2817 ret = soft_offline_in_use_page(page);
2818 } else if (ret == 0) {
2819 if (!page_handle_poison(page, true, false)) {
2820 if (try_again) {
2821 try_again = false;
2822 flags &= ~MF_COUNT_INCREASED;
2823 goto retry;
2824 }
2825 ret = -EBUSY;
2826 }
2827 }
2828
2829 mutex_unlock(&mf_mutex);
2830
2831 return ret;
2832}