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