1 /*
2 * Copyright (C) 2008, 2009 Intel Corporation
3 * Authors: Andi Kleen, Fengguang Wu
4 *
5 * This software may be redistributed and/or modified under the terms of
6 * the GNU General Public License ("GPL") version 2 only as published by the
7 * Free Software Foundation.
8 *
9 * High level machine check handler. Handles pages reported by the
10 * hardware as being corrupted usually due to a multi-bit ECC memory or cache
11 * failure.
12 *
13 * In addition there is a "soft offline" entry point that allows stop using
14 * not-yet-corrupted-by-suspicious pages without killing anything.
15 *
16 * Handles page cache pages in various states. The tricky part
17 * here is that we can access any page asynchronously in respect to
18 * other VM users, because memory failures could happen anytime and
19 * anywhere. This could violate some of their assumptions. This is why
20 * this code has to be extremely careful. Generally it tries to use
21 * normal locking rules, as in get the standard locks, even if that means
22 * the error handling takes potentially a long time.
23 *
24 * There are several operations here with exponential complexity because
25 * of unsuitable VM data structures. For example the operation to map back
26 * from RMAP chains to processes has to walk the complete process list and
27 * has non linear complexity with the number. But since memory corruptions
28 * are rare we hope to get away with this. This avoids impacting the core
29 * VM.
30 */
32 /*
33 * Notebook:
34 * - hugetlb needs more code
35 * - kcore/oldmem/vmcore/mem/kmem check for hwpoison pages
36 * - pass bad pages to kdump next kernel
37 */
38 #include <linux/kernel.h>
39 #include <linux/mm.h>
40 #include <linux/page-flags.h>
41 #include <linux/kernel-page-flags.h>
42 #include <linux/sched.h>
43 #include <linux/ksm.h>
44 #include <linux/rmap.h>
45 #include <linux/export.h>
46 #include <linux/pagemap.h>
47 #include <linux/swap.h>
48 #include <linux/backing-dev.h>
49 #include <linux/migrate.h>
50 #include <linux/page-isolation.h>
51 #include <linux/suspend.h>
52 #include <linux/slab.h>
53 #include <linux/swapops.h>
54 #include <linux/hugetlb.h>
55 #include <linux/memory_hotplug.h>
56 #include <linux/mm_inline.h>
57 #include <linux/kfifo.h>
58 #include "internal.h"
60 int sysctl_memory_failure_early_kill __read_mostly = 0;
62 int sysctl_memory_failure_recovery __read_mostly = 1;
64 atomic_long_t mce_bad_pages __read_mostly = ATOMIC_LONG_INIT(0);
66 #if defined(CONFIG_HWPOISON_INJECT) || defined(CONFIG_HWPOISON_INJECT_MODULE)
68 u32 hwpoison_filter_enable = 0;
69 u32 hwpoison_filter_dev_major = ~0U;
70 u32 hwpoison_filter_dev_minor = ~0U;
71 u64 hwpoison_filter_flags_mask;
72 u64 hwpoison_filter_flags_value;
73 EXPORT_SYMBOL_GPL(hwpoison_filter_enable);
74 EXPORT_SYMBOL_GPL(hwpoison_filter_dev_major);
75 EXPORT_SYMBOL_GPL(hwpoison_filter_dev_minor);
76 EXPORT_SYMBOL_GPL(hwpoison_filter_flags_mask);
77 EXPORT_SYMBOL_GPL(hwpoison_filter_flags_value);
79 static int hwpoison_filter_dev(struct page *p)
80 {
81 struct address_space *mapping;
82 dev_t dev;
84 if (hwpoison_filter_dev_major == ~0U &&
85 hwpoison_filter_dev_minor == ~0U)
86 return 0;
88 /*
89 * page_mapping() does not accept slab pages.
90 */
91 if (PageSlab(p))
92 return -EINVAL;
94 mapping = page_mapping(p);
95 if (mapping == NULL || mapping->host == NULL)
96 return -EINVAL;
98 dev = mapping->host->i_sb->s_dev;
99 if (hwpoison_filter_dev_major != ~0U &&
100 hwpoison_filter_dev_major != MAJOR(dev))
101 return -EINVAL;
102 if (hwpoison_filter_dev_minor != ~0U &&
103 hwpoison_filter_dev_minor != MINOR(dev))
104 return -EINVAL;
106 return 0;
107 }
109 static int hwpoison_filter_flags(struct page *p)
110 {
111 if (!hwpoison_filter_flags_mask)
112 return 0;
114 if ((stable_page_flags(p) & hwpoison_filter_flags_mask) ==
115 hwpoison_filter_flags_value)
116 return 0;
117 else
118 return -EINVAL;
119 }
121 /*
122 * This allows stress tests to limit test scope to a collection of tasks
123 * by putting them under some memcg. This prevents killing unrelated/important
124 * processes such as /sbin/init. Note that the target task may share clean
125 * pages with init (eg. libc text), which is harmless. If the target task
126 * share _dirty_ pages with another task B, the test scheme must make sure B
127 * is also included in the memcg. At last, due to race conditions this filter
128 * can only guarantee that the page either belongs to the memcg tasks, or is
129 * a freed page.
130 */
131 #ifdef CONFIG_MEMCG_SWAP
132 u64 hwpoison_filter_memcg;
133 EXPORT_SYMBOL_GPL(hwpoison_filter_memcg);
134 static int hwpoison_filter_task(struct page *p)
135 {
136 struct mem_cgroup *mem;
137 struct cgroup_subsys_state *css;
138 unsigned long ino;
140 if (!hwpoison_filter_memcg)
141 return 0;
143 mem = try_get_mem_cgroup_from_page(p);
144 if (!mem)
145 return -EINVAL;
147 css = mem_cgroup_css(mem);
148 /* root_mem_cgroup has NULL dentries */
149 if (!css->cgroup->dentry)
150 return -EINVAL;
152 ino = css->cgroup->dentry->d_inode->i_ino;
153 css_put(css);
155 if (ino != hwpoison_filter_memcg)
156 return -EINVAL;
158 return 0;
159 }
160 #else
161 static int hwpoison_filter_task(struct page *p) { return 0; }
162 #endif
164 int hwpoison_filter(struct page *p)
165 {
166 if (!hwpoison_filter_enable)
167 return 0;
169 if (hwpoison_filter_dev(p))
170 return -EINVAL;
172 if (hwpoison_filter_flags(p))
173 return -EINVAL;
175 if (hwpoison_filter_task(p))
176 return -EINVAL;
178 return 0;
179 }
180 #else
181 int hwpoison_filter(struct page *p)
182 {
183 return 0;
184 }
185 #endif
187 EXPORT_SYMBOL_GPL(hwpoison_filter);
189 /*
190 * Send all the processes who have the page mapped a signal.
191 * ``action optional'' if they are not immediately affected by the error
192 * ``action required'' if error happened in current execution context
193 */
194 static int kill_proc(struct task_struct *t, unsigned long addr, int trapno,
195 unsigned long pfn, struct page *page, int flags)
196 {
197 struct siginfo si;
198 int ret;
200 printk(KERN_ERR
201 "MCE %#lx: Killing %s:%d due to hardware memory corruption\n",
202 pfn, t->comm, t->pid);
203 si.si_signo = SIGBUS;
204 si.si_errno = 0;
205 si.si_addr = (void *)addr;
206 #ifdef __ARCH_SI_TRAPNO
207 si.si_trapno = trapno;
208 #endif
209 si.si_addr_lsb = compound_trans_order(compound_head(page)) + PAGE_SHIFT;
211 if ((flags & MF_ACTION_REQUIRED) && t == current) {
212 si.si_code = BUS_MCEERR_AR;
213 ret = force_sig_info(SIGBUS, &si, t);
214 } else {
215 /*
216 * Don't use force here, it's convenient if the signal
217 * can be temporarily blocked.
218 * This could cause a loop when the user sets SIGBUS
219 * to SIG_IGN, but hopefully no one will do that?
220 */
221 si.si_code = BUS_MCEERR_AO;
222 ret = send_sig_info(SIGBUS, &si, t); /* synchronous? */
223 }
224 if (ret < 0)
225 printk(KERN_INFO "MCE: Error sending signal to %s:%d: %d\n",
226 t->comm, t->pid, ret);
227 return ret;
228 }
230 /*
231 * When a unknown page type is encountered drain as many buffers as possible
232 * in the hope to turn the page into a LRU or free page, which we can handle.
233 */
234 void shake_page(struct page *p, int access)
235 {
236 if (!PageSlab(p)) {
237 lru_add_drain_all();
238 if (PageLRU(p))
239 return;
240 drain_all_pages();
241 if (PageLRU(p) || is_free_buddy_page(p))
242 return;
243 }
245 /*
246 * Only call shrink_slab here (which would also shrink other caches) if
247 * access is not potentially fatal.
248 */
249 if (access) {
250 int nr;
251 do {
252 struct shrink_control shrink = {
253 .gfp_mask = GFP_KERNEL,
254 };
256 nr = shrink_slab(&shrink, 1000, 1000);
257 if (page_count(p) == 1)
258 break;
259 } while (nr > 10);
260 }
261 }
262 EXPORT_SYMBOL_GPL(shake_page);
264 /*
265 * Kill all processes that have a poisoned page mapped and then isolate
266 * the page.
267 *
268 * General strategy:
269 * Find all processes having the page mapped and kill them.
270 * But we keep a page reference around so that the page is not
271 * actually freed yet.
272 * Then stash the page away
273 *
274 * There's no convenient way to get back to mapped processes
275 * from the VMAs. So do a brute-force search over all
276 * running processes.
277 *
278 * Remember that machine checks are not common (or rather
279 * if they are common you have other problems), so this shouldn't
280 * be a performance issue.
281 *
282 * Also there are some races possible while we get from the
283 * error detection to actually handle it.
284 */
286 struct to_kill {
287 struct list_head nd;
288 struct task_struct *tsk;
289 unsigned long addr;
290 char addr_valid;
291 };
293 /*
294 * Failure handling: if we can't find or can't kill a process there's
295 * not much we can do. We just print a message and ignore otherwise.
296 */
298 /*
299 * Schedule a process for later kill.
300 * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
301 * TBD would GFP_NOIO be enough?
302 */
303 static void add_to_kill(struct task_struct *tsk, struct page *p,
304 struct vm_area_struct *vma,
305 struct list_head *to_kill,
306 struct to_kill **tkc)
307 {
308 struct to_kill *tk;
310 if (*tkc) {
311 tk = *tkc;
312 *tkc = NULL;
313 } else {
314 tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
315 if (!tk) {
316 printk(KERN_ERR
317 "MCE: Out of memory while machine check handling\n");
318 return;
319 }
320 }
321 tk->addr = page_address_in_vma(p, vma);
322 tk->addr_valid = 1;
324 /*
325 * In theory we don't have to kill when the page was
326 * munmaped. But it could be also a mremap. Since that's
327 * likely very rare kill anyways just out of paranoia, but use
328 * a SIGKILL because the error is not contained anymore.
329 */
330 if (tk->addr == -EFAULT) {
331 pr_info("MCE: Unable to find user space address %lx in %s\n",
332 page_to_pfn(p), tsk->comm);
333 tk->addr_valid = 0;
334 }
335 get_task_struct(tsk);
336 tk->tsk = tsk;
337 list_add_tail(&tk->nd, to_kill);
338 }
340 /*
341 * Kill the processes that have been collected earlier.
342 *
343 * Only do anything when DOIT is set, otherwise just free the list
344 * (this is used for clean pages which do not need killing)
345 * Also when FAIL is set do a force kill because something went
346 * wrong earlier.
347 */
348 static void kill_procs(struct list_head *to_kill, int forcekill, int trapno,
349 int fail, struct page *page, unsigned long pfn,
350 int flags)
351 {
352 struct to_kill *tk, *next;
354 list_for_each_entry_safe (tk, next, to_kill, nd) {
355 if (forcekill) {
356 /*
357 * In case something went wrong with munmapping
358 * make sure the process doesn't catch the
359 * signal and then access the memory. Just kill it.
360 */
361 if (fail || tk->addr_valid == 0) {
362 printk(KERN_ERR
363 "MCE %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n",
364 pfn, tk->tsk->comm, tk->tsk->pid);
365 force_sig(SIGKILL, tk->tsk);
366 }
368 /*
369 * In theory the process could have mapped
370 * something else on the address in-between. We could
371 * check for that, but we need to tell the
372 * process anyways.
373 */
374 else if (kill_proc(tk->tsk, tk->addr, trapno,
375 pfn, page, flags) < 0)
376 printk(KERN_ERR
377 "MCE %#lx: Cannot send advisory machine check signal to %s:%d\n",
378 pfn, tk->tsk->comm, tk->tsk->pid);
379 }
380 put_task_struct(tk->tsk);
381 kfree(tk);
382 }
383 }
385 static int task_early_kill(struct task_struct *tsk)
386 {
387 if (!tsk->mm)
388 return 0;
389 if (tsk->flags & PF_MCE_PROCESS)
390 return !!(tsk->flags & PF_MCE_EARLY);
391 return sysctl_memory_failure_early_kill;
392 }
394 /*
395 * Collect processes when the error hit an anonymous page.
396 */
397 static void collect_procs_anon(struct page *page, struct list_head *to_kill,
398 struct to_kill **tkc)
399 {
400 struct vm_area_struct *vma;
401 struct task_struct *tsk;
402 struct anon_vma *av;
403 pgoff_t pgoff;
405 av = page_lock_anon_vma_read(page);
406 if (av == NULL) /* Not actually mapped anymore */
407 return;
409 pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
410 read_lock(&tasklist_lock);
411 for_each_process (tsk) {
412 struct anon_vma_chain *vmac;
414 if (!task_early_kill(tsk))
415 continue;
416 anon_vma_interval_tree_foreach(vmac, &av->rb_root,
417 pgoff, pgoff) {
418 vma = vmac->vma;
419 if (!page_mapped_in_vma(page, vma))
420 continue;
421 if (vma->vm_mm == tsk->mm)
422 add_to_kill(tsk, page, vma, to_kill, tkc);
423 }
424 }
425 read_unlock(&tasklist_lock);
426 page_unlock_anon_vma_read(av);
427 }
429 /*
430 * Collect processes when the error hit a file mapped page.
431 */
432 static void collect_procs_file(struct page *page, struct list_head *to_kill,
433 struct to_kill **tkc)
434 {
435 struct vm_area_struct *vma;
436 struct task_struct *tsk;
437 struct address_space *mapping = page->mapping;
439 mutex_lock(&mapping->i_mmap_mutex);
440 read_lock(&tasklist_lock);
441 for_each_process(tsk) {
442 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
444 if (!task_early_kill(tsk))
445 continue;
447 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff,
448 pgoff) {
449 /*
450 * Send early kill signal to tasks where a vma covers
451 * the page but the corrupted page is not necessarily
452 * mapped it in its pte.
453 * Assume applications who requested early kill want
454 * to be informed of all such data corruptions.
455 */
456 if (vma->vm_mm == tsk->mm)
457 add_to_kill(tsk, page, vma, to_kill, tkc);
458 }
459 }
460 read_unlock(&tasklist_lock);
461 mutex_unlock(&mapping->i_mmap_mutex);
462 }
464 /*
465 * Collect the processes who have the corrupted page mapped to kill.
466 * This is done in two steps for locking reasons.
467 * First preallocate one tokill structure outside the spin locks,
468 * so that we can kill at least one process reasonably reliable.
469 */
470 static void collect_procs(struct page *page, struct list_head *tokill)
471 {
472 struct to_kill *tk;
474 if (!page->mapping)
475 return;
477 tk = kmalloc(sizeof(struct to_kill), GFP_NOIO);
478 if (!tk)
479 return;
480 if (PageAnon(page))
481 collect_procs_anon(page, tokill, &tk);
482 else
483 collect_procs_file(page, tokill, &tk);
484 kfree(tk);
485 }
487 /*
488 * Error handlers for various types of pages.
489 */
491 enum outcome {
492 IGNORED, /* Error: cannot be handled */
493 FAILED, /* Error: handling failed */
494 DELAYED, /* Will be handled later */
495 RECOVERED, /* Successfully recovered */
496 };
498 static const char *action_name[] = {
499 [IGNORED] = "Ignored",
500 [FAILED] = "Failed",
501 [DELAYED] = "Delayed",
502 [RECOVERED] = "Recovered",
503 };
505 /*
506 * XXX: It is possible that a page is isolated from LRU cache,
507 * and then kept in swap cache or failed to remove from page cache.
508 * The page count will stop it from being freed by unpoison.
509 * Stress tests should be aware of this memory leak problem.
510 */
511 static int delete_from_lru_cache(struct page *p)
512 {
513 if (!isolate_lru_page(p)) {
514 /*
515 * Clear sensible page flags, so that the buddy system won't
516 * complain when the page is unpoison-and-freed.
517 */
518 ClearPageActive(p);
519 ClearPageUnevictable(p);
520 /*
521 * drop the page count elevated by isolate_lru_page()
522 */
523 page_cache_release(p);
524 return 0;
525 }
526 return -EIO;
527 }
529 /*
530 * Error hit kernel page.
531 * Do nothing, try to be lucky and not touch this instead. For a few cases we
532 * could be more sophisticated.
533 */
534 static int me_kernel(struct page *p, unsigned long pfn)
535 {
536 return IGNORED;
537 }
539 /*
540 * Page in unknown state. Do nothing.
541 */
542 static int me_unknown(struct page *p, unsigned long pfn)
543 {
544 printk(KERN_ERR "MCE %#lx: Unknown page state\n", pfn);
545 return FAILED;
546 }
548 /*
549 * Clean (or cleaned) page cache page.
550 */
551 static int me_pagecache_clean(struct page *p, unsigned long pfn)
552 {
553 int err;
554 int ret = FAILED;
555 struct address_space *mapping;
557 delete_from_lru_cache(p);
559 /*
560 * For anonymous pages we're done the only reference left
561 * should be the one m_f() holds.
562 */
563 if (PageAnon(p))
564 return RECOVERED;
566 /*
567 * Now truncate the page in the page cache. This is really
568 * more like a "temporary hole punch"
569 * Don't do this for block devices when someone else
570 * has a reference, because it could be file system metadata
571 * and that's not safe to truncate.
572 */
573 mapping = page_mapping(p);
574 if (!mapping) {
575 /*
576 * Page has been teared down in the meanwhile
577 */
578 return FAILED;
579 }
581 /*
582 * Truncation is a bit tricky. Enable it per file system for now.
583 *
584 * Open: to take i_mutex or not for this? Right now we don't.
585 */
586 if (mapping->a_ops->error_remove_page) {
587 err = mapping->a_ops->error_remove_page(mapping, p);
588 if (err != 0) {
589 printk(KERN_INFO "MCE %#lx: Failed to punch page: %d\n",
590 pfn, err);
591 } else if (page_has_private(p) &&
592 !try_to_release_page(p, GFP_NOIO)) {
593 pr_info("MCE %#lx: failed to release buffers\n", pfn);
594 } else {
595 ret = RECOVERED;
596 }
597 } else {
598 /*
599 * If the file system doesn't support it just invalidate
600 * This fails on dirty or anything with private pages
601 */
602 if (invalidate_inode_page(p))
603 ret = RECOVERED;
604 else
605 printk(KERN_INFO "MCE %#lx: Failed to invalidate\n",
606 pfn);
607 }
608 return ret;
609 }
611 /*
612 * Dirty cache page page
613 * Issues: when the error hit a hole page the error is not properly
614 * propagated.
615 */
616 static int me_pagecache_dirty(struct page *p, unsigned long pfn)
617 {
618 struct address_space *mapping = page_mapping(p);
620 SetPageError(p);
621 /* TBD: print more information about the file. */
622 if (mapping) {
623 /*
624 * IO error will be reported by write(), fsync(), etc.
625 * who check the mapping.
626 * This way the application knows that something went
627 * wrong with its dirty file data.
628 *
629 * There's one open issue:
630 *
631 * The EIO will be only reported on the next IO
632 * operation and then cleared through the IO map.
633 * Normally Linux has two mechanisms to pass IO error
634 * first through the AS_EIO flag in the address space
635 * and then through the PageError flag in the page.
636 * Since we drop pages on memory failure handling the
637 * only mechanism open to use is through AS_AIO.
638 *
639 * This has the disadvantage that it gets cleared on
640 * the first operation that returns an error, while
641 * the PageError bit is more sticky and only cleared
642 * when the page is reread or dropped. If an
643 * application assumes it will always get error on
644 * fsync, but does other operations on the fd before
645 * and the page is dropped between then the error
646 * will not be properly reported.
647 *
648 * This can already happen even without hwpoisoned
649 * pages: first on metadata IO errors (which only
650 * report through AS_EIO) or when the page is dropped
651 * at the wrong time.
652 *
653 * So right now we assume that the application DTRT on
654 * the first EIO, but we're not worse than other parts
655 * of the kernel.
656 */
657 mapping_set_error(mapping, EIO);
658 }
660 return me_pagecache_clean(p, pfn);
661 }
663 /*
664 * Clean and dirty swap cache.
665 *
666 * Dirty swap cache page is tricky to handle. The page could live both in page
667 * cache and swap cache(ie. page is freshly swapped in). So it could be
668 * referenced concurrently by 2 types of PTEs:
669 * normal PTEs and swap PTEs. We try to handle them consistently by calling
670 * try_to_unmap(TTU_IGNORE_HWPOISON) to convert the normal PTEs to swap PTEs,
671 * and then
672 * - clear dirty bit to prevent IO
673 * - remove from LRU
674 * - but keep in the swap cache, so that when we return to it on
675 * a later page fault, we know the application is accessing
676 * corrupted data and shall be killed (we installed simple
677 * interception code in do_swap_page to catch it).
678 *
679 * Clean swap cache pages can be directly isolated. A later page fault will
680 * bring in the known good data from disk.
681 */
682 static int me_swapcache_dirty(struct page *p, unsigned long pfn)
683 {
684 ClearPageDirty(p);
685 /* Trigger EIO in shmem: */
686 ClearPageUptodate(p);
688 if (!delete_from_lru_cache(p))
689 return DELAYED;
690 else
691 return FAILED;
692 }
694 static int me_swapcache_clean(struct page *p, unsigned long pfn)
695 {
696 delete_from_swap_cache(p);
698 if (!delete_from_lru_cache(p))
699 return RECOVERED;
700 else
701 return FAILED;
702 }
704 /*
705 * Huge pages. Needs work.
706 * Issues:
707 * - Error on hugepage is contained in hugepage unit (not in raw page unit.)
708 * To narrow down kill region to one page, we need to break up pmd.
709 */
710 static int me_huge_page(struct page *p, unsigned long pfn)
711 {
712 int res = 0;
713 struct page *hpage = compound_head(p);
714 /*
715 * We can safely recover from error on free or reserved (i.e.
716 * not in-use) hugepage by dequeuing it from freelist.
717 * To check whether a hugepage is in-use or not, we can't use
718 * page->lru because it can be used in other hugepage operations,
719 * such as __unmap_hugepage_range() and gather_surplus_pages().
720 * So instead we use page_mapping() and PageAnon().
721 * We assume that this function is called with page lock held,
722 * so there is no race between isolation and mapping/unmapping.
723 */
724 if (!(page_mapping(hpage) || PageAnon(hpage))) {
725 res = dequeue_hwpoisoned_huge_page(hpage);
726 if (!res)
727 return RECOVERED;
728 }
729 return DELAYED;
730 }
732 /*
733 * Various page states we can handle.
734 *
735 * A page state is defined by its current page->flags bits.
736 * The table matches them in order and calls the right handler.
737 *
738 * This is quite tricky because we can access page at any time
739 * in its live cycle, so all accesses have to be extremely careful.
740 *
741 * This is not complete. More states could be added.
742 * For any missing state don't attempt recovery.
743 */
745 #define dirty (1UL << PG_dirty)
746 #define sc (1UL << PG_swapcache)
747 #define unevict (1UL << PG_unevictable)
748 #define mlock (1UL << PG_mlocked)
749 #define writeback (1UL << PG_writeback)
750 #define lru (1UL << PG_lru)
751 #define swapbacked (1UL << PG_swapbacked)
752 #define head (1UL << PG_head)
753 #define tail (1UL << PG_tail)
754 #define compound (1UL << PG_compound)
755 #define slab (1UL << PG_slab)
756 #define reserved (1UL << PG_reserved)
758 static struct page_state {
759 unsigned long mask;
760 unsigned long res;
761 char *msg;
762 int (*action)(struct page *p, unsigned long pfn);
763 } error_states[] = {
764 { reserved, reserved, "reserved kernel", me_kernel },
765 /*
766 * free pages are specially detected outside this table:
767 * PG_buddy pages only make a small fraction of all free pages.
768 */
770 /*
771 * Could in theory check if slab page is free or if we can drop
772 * currently unused objects without touching them. But just
773 * treat it as standard kernel for now.
774 */
775 { slab, slab, "kernel slab", me_kernel },
777 #ifdef CONFIG_PAGEFLAGS_EXTENDED
778 { head, head, "huge", me_huge_page },
779 { tail, tail, "huge", me_huge_page },
780 #else
781 { compound, compound, "huge", me_huge_page },
782 #endif
784 { sc|dirty, sc|dirty, "dirty swapcache", me_swapcache_dirty },
785 { sc|dirty, sc, "clean swapcache", me_swapcache_clean },
787 { unevict|dirty, unevict|dirty, "dirty unevictable LRU", me_pagecache_dirty },
788 { unevict, unevict, "clean unevictable LRU", me_pagecache_clean },
790 { mlock|dirty, mlock|dirty, "dirty mlocked LRU", me_pagecache_dirty },
791 { mlock, mlock, "clean mlocked LRU", me_pagecache_clean },
793 { lru|dirty, lru|dirty, "dirty LRU", me_pagecache_dirty },
794 { lru|dirty, lru, "clean LRU", me_pagecache_clean },
796 /*
797 * Catchall entry: must be at end.
798 */
799 { 0, 0, "unknown page state", me_unknown },
800 };
802 #undef dirty
803 #undef sc
804 #undef unevict
805 #undef mlock
806 #undef writeback
807 #undef lru
808 #undef swapbacked
809 #undef head
810 #undef tail
811 #undef compound
812 #undef slab
813 #undef reserved
815 /*
816 * "Dirty/Clean" indication is not 100% accurate due to the possibility of
817 * setting PG_dirty outside page lock. See also comment above set_page_dirty().
818 */
819 static void action_result(unsigned long pfn, char *msg, int result)
820 {
821 pr_err("MCE %#lx: %s page recovery: %s\n",
822 pfn, msg, action_name[result]);
823 }
825 static int page_action(struct page_state *ps, struct page *p,
826 unsigned long pfn)
827 {
828 int result;
829 int count;
831 result = ps->action(p, pfn);
832 action_result(pfn, ps->msg, result);
834 count = page_count(p) - 1;
835 if (ps->action == me_swapcache_dirty && result == DELAYED)
836 count--;
837 if (count != 0) {
838 printk(KERN_ERR
839 "MCE %#lx: %s page still referenced by %d users\n",
840 pfn, ps->msg, count);
841 result = FAILED;
842 }
844 /* Could do more checks here if page looks ok */
845 /*
846 * Could adjust zone counters here to correct for the missing page.
847 */
849 return (result == RECOVERED || result == DELAYED) ? 0 : -EBUSY;
850 }
852 /*
853 * Do all that is necessary to remove user space mappings. Unmap
854 * the pages and send SIGBUS to the processes if the data was dirty.
855 */
856 static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
857 int trapno, int flags)
858 {
859 enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
860 struct address_space *mapping;
861 LIST_HEAD(tokill);
862 int ret;
863 int kill = 1, forcekill;
864 struct page *hpage = compound_head(p);
865 struct page *ppage;
867 if (PageReserved(p) || PageSlab(p))
868 return SWAP_SUCCESS;
870 /*
871 * This check implies we don't kill processes if their pages
872 * are in the swap cache early. Those are always late kills.
873 */
874 if (!page_mapped(hpage))
875 return SWAP_SUCCESS;
877 if (PageKsm(p))
878 return SWAP_FAIL;
880 if (PageSwapCache(p)) {
881 printk(KERN_ERR
882 "MCE %#lx: keeping poisoned page in swap cache\n", pfn);
883 ttu |= TTU_IGNORE_HWPOISON;
884 }
886 /*
887 * Propagate the dirty bit from PTEs to struct page first, because we
888 * need this to decide if we should kill or just drop the page.
889 * XXX: the dirty test could be racy: set_page_dirty() may not always
890 * be called inside page lock (it's recommended but not enforced).
891 */
892 mapping = page_mapping(hpage);
893 if (!(flags & MF_MUST_KILL) && !PageDirty(hpage) && mapping &&
894 mapping_cap_writeback_dirty(mapping)) {
895 if (page_mkclean(hpage)) {
896 SetPageDirty(hpage);
897 } else {
898 kill = 0;
899 ttu |= TTU_IGNORE_HWPOISON;
900 printk(KERN_INFO
901 "MCE %#lx: corrupted page was clean: dropped without side effects\n",
902 pfn);
903 }
904 }
906 /*
907 * ppage: poisoned page
908 * if p is regular page(4k page)
909 * ppage == real poisoned page;
910 * else p is hugetlb or THP, ppage == head page.
911 */
912 ppage = hpage;
914 if (PageTransHuge(hpage)) {
915 /*
916 * Verify that this isn't a hugetlbfs head page, the check for
917 * PageAnon is just for avoid tripping a split_huge_page
918 * internal debug check, as split_huge_page refuses to deal with
919 * anything that isn't an anon page. PageAnon can't go away fro
920 * under us because we hold a refcount on the hpage, without a
921 * refcount on the hpage. split_huge_page can't be safely called
922 * in the first place, having a refcount on the tail isn't
923 * enough * to be safe.
924 */
925 if (!PageHuge(hpage) && PageAnon(hpage)) {
926 if (unlikely(split_huge_page(hpage))) {
927 /*
928 * FIXME: if splitting THP is failed, it is
929 * better to stop the following operation rather
930 * than causing panic by unmapping. System might
931 * survive if the page is freed later.
932 */
933 printk(KERN_INFO
934 "MCE %#lx: failed to split THP\n", pfn);
936 BUG_ON(!PageHWPoison(p));
937 return SWAP_FAIL;
938 }
939 /* THP is split, so ppage should be the real poisoned page. */
940 ppage = p;
941 }
942 }
944 /*
945 * First collect all the processes that have the page
946 * mapped in dirty form. This has to be done before try_to_unmap,
947 * because ttu takes the rmap data structures down.
948 *
949 * Error handling: We ignore errors here because
950 * there's nothing that can be done.
951 */
952 if (kill)
953 collect_procs(ppage, &tokill);
955 if (hpage != ppage)
956 lock_page(ppage);
958 ret = try_to_unmap(ppage, ttu);
959 if (ret != SWAP_SUCCESS)
960 printk(KERN_ERR "MCE %#lx: failed to unmap page (mapcount=%d)\n",
961 pfn, page_mapcount(ppage));
963 if (hpage != ppage)
964 unlock_page(ppage);
966 /*
967 * Now that the dirty bit has been propagated to the
968 * struct page and all unmaps done we can decide if
969 * killing is needed or not. Only kill when the page
970 * was dirty or the process is not restartable,
971 * otherwise the tokill list is merely
972 * freed. When there was a problem unmapping earlier
973 * use a more force-full uncatchable kill to prevent
974 * any accesses to the poisoned memory.
975 */
976 forcekill = PageDirty(ppage) || (flags & MF_MUST_KILL);
977 kill_procs(&tokill, forcekill, trapno,
978 ret != SWAP_SUCCESS, p, pfn, flags);
980 return ret;
981 }
983 static void set_page_hwpoison_huge_page(struct page *hpage)
984 {
985 int i;
986 int nr_pages = 1 << compound_trans_order(hpage);
987 for (i = 0; i < nr_pages; i++)
988 SetPageHWPoison(hpage + i);
989 }
991 static void clear_page_hwpoison_huge_page(struct page *hpage)
992 {
993 int i;
994 int nr_pages = 1 << compound_trans_order(hpage);
995 for (i = 0; i < nr_pages; i++)
996 ClearPageHWPoison(hpage + i);
997 }
999 /**
1000 * memory_failure - Handle memory failure of a page.
1001 * @pfn: Page Number of the corrupted page
1002 * @trapno: Trap number reported in the signal to user space.
1003 * @flags: fine tune action taken
1004 *
1005 * This function is called by the low level machine check code
1006 * of an architecture when it detects hardware memory corruption
1007 * of a page. It tries its best to recover, which includes
1008 * dropping pages, killing processes etc.
1009 *
1010 * The function is primarily of use for corruptions that
1011 * happen outside the current execution context (e.g. when
1012 * detected by a background scrubber)
1013 *
1014 * Must run in process context (e.g. a work queue) with interrupts
1015 * enabled and no spinlocks hold.
1016 */
1017 int memory_failure(unsigned long pfn, int trapno, int flags)
1018 {
1019 struct page_state *ps;
1020 struct page *p;
1021 struct page *hpage;
1022 int res;
1023 unsigned int nr_pages;
1025 if (!sysctl_memory_failure_recovery)
1026 panic("Memory failure from trap %d on page %lx", trapno, pfn);
1028 if (!pfn_valid(pfn)) {
1029 printk(KERN_ERR
1030 "MCE %#lx: memory outside kernel control\n",
1031 pfn);
1032 return -ENXIO;
1033 }
1035 p = pfn_to_page(pfn);
1036 hpage = compound_head(p);
1037 if (TestSetPageHWPoison(p)) {
1038 printk(KERN_ERR "MCE %#lx: already hardware poisoned\n", pfn);
1039 return 0;
1040 }
1042 nr_pages = 1 << compound_trans_order(hpage);
1043 atomic_long_add(nr_pages, &mce_bad_pages);
1045 /*
1046 * We need/can do nothing about count=0 pages.
1047 * 1) it's a free page, and therefore in safe hand:
1048 * prep_new_page() will be the gate keeper.
1049 * 2) it's a free hugepage, which is also safe:
1050 * an affected hugepage will be dequeued from hugepage freelist,
1051 * so there's no concern about reusing it ever after.
1052 * 3) it's part of a non-compound high order page.
1053 * Implies some kernel user: cannot stop them from
1054 * R/W the page; let's pray that the page has been
1055 * used and will be freed some time later.
1056 * In fact it's dangerous to directly bump up page count from 0,
1057 * that may make page_freeze_refs()/page_unfreeze_refs() mismatch.
1058 */
1059 if (!(flags & MF_COUNT_INCREASED) &&
1060 !get_page_unless_zero(hpage)) {
1061 if (is_free_buddy_page(p)) {
1062 action_result(pfn, "free buddy", DELAYED);
1063 return 0;
1064 } else if (PageHuge(hpage)) {
1065 /*
1066 * Check "just unpoisoned", "filter hit", and
1067 * "race with other subpage."
1068 */
1069 lock_page(hpage);
1070 if (!PageHWPoison(hpage)
1071 || (hwpoison_filter(p) && TestClearPageHWPoison(p))
1072 || (p != hpage && TestSetPageHWPoison(hpage))) {
1073 atomic_long_sub(nr_pages, &mce_bad_pages);
1074 return 0;
1075 }
1076 set_page_hwpoison_huge_page(hpage);
1077 res = dequeue_hwpoisoned_huge_page(hpage);
1078 action_result(pfn, "free huge",
1079 res ? IGNORED : DELAYED);
1080 unlock_page(hpage);
1081 return res;
1082 } else {
1083 action_result(pfn, "high order kernel", IGNORED);
1084 return -EBUSY;
1085 }
1086 }
1088 /*
1089 * We ignore non-LRU pages for good reasons.
1090 * - PG_locked is only well defined for LRU pages and a few others
1091 * - to avoid races with __set_page_locked()
1092 * - to avoid races with __SetPageSlab*() (and more non-atomic ops)
1093 * The check (unnecessarily) ignores LRU pages being isolated and
1094 * walked by the page reclaim code, however that's not a big loss.
1095 */
1096 if (!PageHuge(p) && !PageTransTail(p)) {
1097 if (!PageLRU(p))
1098 shake_page(p, 0);
1099 if (!PageLRU(p)) {
1100 /*
1101 * shake_page could have turned it free.
1102 */
1103 if (is_free_buddy_page(p)) {
1104 action_result(pfn, "free buddy, 2nd try",
1105 DELAYED);
1106 return 0;
1107 }
1108 action_result(pfn, "non LRU", IGNORED);
1109 put_page(p);
1110 return -EBUSY;
1111 }
1112 }
1114 /*
1115 * Lock the page and wait for writeback to finish.
1116 * It's very difficult to mess with pages currently under IO
1117 * and in many cases impossible, so we just avoid it here.
1118 */
1119 lock_page(hpage);
1121 /*
1122 * unpoison always clear PG_hwpoison inside page lock
1123 */
1124 if (!PageHWPoison(p)) {
1125 printk(KERN_ERR "MCE %#lx: just unpoisoned\n", pfn);
1126 res = 0;
1127 goto out;
1128 }
1129 if (hwpoison_filter(p)) {
1130 if (TestClearPageHWPoison(p))
1131 atomic_long_sub(nr_pages, &mce_bad_pages);
1132 unlock_page(hpage);
1133 put_page(hpage);
1134 return 0;
1135 }
1137 /*
1138 * For error on the tail page, we should set PG_hwpoison
1139 * on the head page to show that the hugepage is hwpoisoned
1140 */
1141 if (PageHuge(p) && PageTail(p) && TestSetPageHWPoison(hpage)) {
1142 action_result(pfn, "hugepage already hardware poisoned",
1143 IGNORED);
1144 unlock_page(hpage);
1145 put_page(hpage);
1146 return 0;
1147 }
1148 /*
1149 * Set PG_hwpoison on all pages in an error hugepage,
1150 * because containment is done in hugepage unit for now.
1151 * Since we have done TestSetPageHWPoison() for the head page with
1152 * page lock held, we can safely set PG_hwpoison bits on tail pages.
1153 */
1154 if (PageHuge(p))
1155 set_page_hwpoison_huge_page(hpage);
1157 wait_on_page_writeback(p);
1159 /*
1160 * Now take care of user space mappings.
1161 * Abort on fail: __delete_from_page_cache() assumes unmapped page.
1162 */
1163 if (hwpoison_user_mappings(p, pfn, trapno, flags) != SWAP_SUCCESS) {
1164 printk(KERN_ERR "MCE %#lx: cannot unmap page, give up\n", pfn);
1165 res = -EBUSY;
1166 goto out;
1167 }
1169 /*
1170 * Torn down by someone else?
1171 */
1172 if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) {
1173 action_result(pfn, "already truncated LRU", IGNORED);
1174 res = -EBUSY;
1175 goto out;
1176 }
1178 res = -EBUSY;
1179 for (ps = error_states;; ps++) {
1180 if ((p->flags & ps->mask) == ps->res) {
1181 res = page_action(ps, p, pfn);
1182 break;
1183 }
1184 }
1185 out:
1186 unlock_page(hpage);
1187 return res;
1188 }
1189 EXPORT_SYMBOL_GPL(memory_failure);
1191 #define MEMORY_FAILURE_FIFO_ORDER 4
1192 #define MEMORY_FAILURE_FIFO_SIZE (1 << MEMORY_FAILURE_FIFO_ORDER)
1194 struct memory_failure_entry {
1195 unsigned long pfn;
1196 int trapno;
1197 int flags;
1198 };
1200 struct memory_failure_cpu {
1201 DECLARE_KFIFO(fifo, struct memory_failure_entry,
1202 MEMORY_FAILURE_FIFO_SIZE);
1203 spinlock_t lock;
1204 struct work_struct work;
1205 };
1207 static DEFINE_PER_CPU(struct memory_failure_cpu, memory_failure_cpu);
1209 /**
1210 * memory_failure_queue - Schedule handling memory failure of a page.
1211 * @pfn: Page Number of the corrupted page
1212 * @trapno: Trap number reported in the signal to user space.
1213 * @flags: Flags for memory failure handling
1214 *
1215 * This function is called by the low level hardware error handler
1216 * when it detects hardware memory corruption of a page. It schedules
1217 * the recovering of error page, including dropping pages, killing
1218 * processes etc.
1219 *
1220 * The function is primarily of use for corruptions that
1221 * happen outside the current execution context (e.g. when
1222 * detected by a background scrubber)
1223 *
1224 * Can run in IRQ context.
1225 */
1226 void memory_failure_queue(unsigned long pfn, int trapno, int flags)
1227 {
1228 struct memory_failure_cpu *mf_cpu;
1229 unsigned long proc_flags;
1230 struct memory_failure_entry entry = {
1231 .pfn = pfn,
1232 .trapno = trapno,
1233 .flags = flags,
1234 };
1236 mf_cpu = &get_cpu_var(memory_failure_cpu);
1237 spin_lock_irqsave(&mf_cpu->lock, proc_flags);
1238 if (kfifo_put(&mf_cpu->fifo, &entry))
1239 schedule_work_on(smp_processor_id(), &mf_cpu->work);
1240 else
1241 pr_err("Memory failure: buffer overflow when queuing memory failure at 0x%#lx\n",
1242 pfn);
1243 spin_unlock_irqrestore(&mf_cpu->lock, proc_flags);
1244 put_cpu_var(memory_failure_cpu);
1245 }
1246 EXPORT_SYMBOL_GPL(memory_failure_queue);
1248 static void memory_failure_work_func(struct work_struct *work)
1249 {
1250 struct memory_failure_cpu *mf_cpu;
1251 struct memory_failure_entry entry = { 0, };
1252 unsigned long proc_flags;
1253 int gotten;
1255 mf_cpu = &__get_cpu_var(memory_failure_cpu);
1256 for (;;) {
1257 spin_lock_irqsave(&mf_cpu->lock, proc_flags);
1258 gotten = kfifo_get(&mf_cpu->fifo, &entry);
1259 spin_unlock_irqrestore(&mf_cpu->lock, proc_flags);
1260 if (!gotten)
1261 break;
1262 memory_failure(entry.pfn, entry.trapno, entry.flags);
1263 }
1264 }
1266 static int __init memory_failure_init(void)
1267 {
1268 struct memory_failure_cpu *mf_cpu;
1269 int cpu;
1271 for_each_possible_cpu(cpu) {
1272 mf_cpu = &per_cpu(memory_failure_cpu, cpu);
1273 spin_lock_init(&mf_cpu->lock);
1274 INIT_KFIFO(mf_cpu->fifo);
1275 INIT_WORK(&mf_cpu->work, memory_failure_work_func);
1276 }
1278 return 0;
1279 }
1280 core_initcall(memory_failure_init);
1282 /**
1283 * unpoison_memory - Unpoison a previously poisoned page
1284 * @pfn: Page number of the to be unpoisoned page
1285 *
1286 * Software-unpoison a page that has been poisoned by
1287 * memory_failure() earlier.
1288 *
1289 * This is only done on the software-level, so it only works
1290 * for linux injected failures, not real hardware failures
1291 *
1292 * Returns 0 for success, otherwise -errno.
1293 */
1294 int unpoison_memory(unsigned long pfn)
1295 {
1296 struct page *page;
1297 struct page *p;
1298 int freeit = 0;
1299 unsigned int nr_pages;
1301 if (!pfn_valid(pfn))
1302 return -ENXIO;
1304 p = pfn_to_page(pfn);
1305 page = compound_head(p);
1307 if (!PageHWPoison(p)) {
1308 pr_info("MCE: Page was already unpoisoned %#lx\n", pfn);
1309 return 0;
1310 }
1312 nr_pages = 1 << compound_trans_order(page);
1314 if (!get_page_unless_zero(page)) {
1315 /*
1316 * Since HWPoisoned hugepage should have non-zero refcount,
1317 * race between memory failure and unpoison seems to happen.
1318 * In such case unpoison fails and memory failure runs
1319 * to the end.
1320 */
1321 if (PageHuge(page)) {
1322 pr_info("MCE: Memory failure is now running on free hugepage %#lx\n", pfn);
1323 return 0;
1324 }
1325 if (TestClearPageHWPoison(p))
1326 atomic_long_sub(nr_pages, &mce_bad_pages);
1327 pr_info("MCE: Software-unpoisoned free page %#lx\n", pfn);
1328 return 0;
1329 }
1331 lock_page(page);
1332 /*
1333 * This test is racy because PG_hwpoison is set outside of page lock.
1334 * That's acceptable because that won't trigger kernel panic. Instead,
1335 * the PG_hwpoison page will be caught and isolated on the entrance to
1336 * the free buddy page pool.
1337 */
1338 if (TestClearPageHWPoison(page)) {
1339 pr_info("MCE: Software-unpoisoned page %#lx\n", pfn);
1340 atomic_long_sub(nr_pages, &mce_bad_pages);
1341 freeit = 1;
1342 if (PageHuge(page))
1343 clear_page_hwpoison_huge_page(page);
1344 }
1345 unlock_page(page);
1347 put_page(page);
1348 if (freeit)
1349 put_page(page);
1351 return 0;
1352 }
1353 EXPORT_SYMBOL(unpoison_memory);
1355 static struct page *new_page(struct page *p, unsigned long private, int **x)
1356 {
1357 int nid = page_to_nid(p);
1358 if (PageHuge(p))
1359 return alloc_huge_page_node(page_hstate(compound_head(p)),
1360 nid);
1361 else
1362 return alloc_pages_exact_node(nid, GFP_HIGHUSER_MOVABLE, 0);
1363 }
1365 /*
1366 * Safely get reference count of an arbitrary page.
1367 * Returns 0 for a free page, -EIO for a zero refcount page
1368 * that is not free, and 1 for any other page type.
1369 * For 1 the page is returned with increased page count, otherwise not.
1370 */
1371 static int get_any_page(struct page *p, unsigned long pfn, int flags)
1372 {
1373 int ret;
1375 if (flags & MF_COUNT_INCREASED)
1376 return 1;
1378 /*
1379 * The lock_memory_hotplug prevents a race with memory hotplug.
1380 * This is a big hammer, a better would be nicer.
1381 */
1382 lock_memory_hotplug();
1384 /*
1385 * Isolate the page, so that it doesn't get reallocated if it
1386 * was free.
1387 */
1388 set_migratetype_isolate(p, true);
1389 /*
1390 * When the target page is a free hugepage, just remove it
1391 * from free hugepage list.
1392 */
1393 if (!get_page_unless_zero(compound_head(p))) {
1394 if (PageHuge(p)) {
1395 pr_info("%s: %#lx free huge page\n", __func__, pfn);
1396 ret = dequeue_hwpoisoned_huge_page(compound_head(p));
1397 } else if (is_free_buddy_page(p)) {
1398 pr_info("%s: %#lx free buddy page\n", __func__, pfn);
1399 /* Set hwpoison bit while page is still isolated */
1400 SetPageHWPoison(p);
1401 ret = 0;
1402 } else {
1403 pr_info("%s: %#lx: unknown zero refcount page type %lx\n",
1404 __func__, pfn, p->flags);
1405 ret = -EIO;
1406 }
1407 } else {
1408 /* Not a free page */
1409 ret = 1;
1410 }
1411 unset_migratetype_isolate(p, MIGRATE_MOVABLE);
1412 unlock_memory_hotplug();
1413 return ret;
1414 }
1416 static int soft_offline_huge_page(struct page *page, int flags)
1417 {
1418 int ret;
1419 unsigned long pfn = page_to_pfn(page);
1420 struct page *hpage = compound_head(page);
1422 ret = get_any_page(page, pfn, flags);
1423 if (ret < 0)
1424 return ret;
1425 if (ret == 0)
1426 goto done;
1428 if (PageHWPoison(hpage)) {
1429 put_page(hpage);
1430 pr_info("soft offline: %#lx hugepage already poisoned\n", pfn);
1431 return -EBUSY;
1432 }
1434 /* Keep page count to indicate a given hugepage is isolated. */
1435 ret = migrate_huge_page(hpage, new_page, MPOL_MF_MOVE_ALL, false,
1436 MIGRATE_SYNC);
1437 put_page(hpage);
1438 if (ret) {
1439 pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
1440 pfn, ret, page->flags);
1441 return ret;
1442 }
1443 done:
1444 if (!PageHWPoison(hpage))
1445 atomic_long_add(1 << compound_trans_order(hpage),
1446 &mce_bad_pages);
1447 set_page_hwpoison_huge_page(hpage);
1448 dequeue_hwpoisoned_huge_page(hpage);
1449 /* keep elevated page count for bad page */
1450 return ret;
1451 }
1453 /**
1454 * soft_offline_page - Soft offline a page.
1455 * @page: page to offline
1456 * @flags: flags. Same as memory_failure().
1457 *
1458 * Returns 0 on success, otherwise negated errno.
1459 *
1460 * Soft offline a page, by migration or invalidation,
1461 * without killing anything. This is for the case when
1462 * a page is not corrupted yet (so it's still valid to access),
1463 * but has had a number of corrected errors and is better taken
1464 * out.
1465 *
1466 * The actual policy on when to do that is maintained by
1467 * user space.
1468 *
1469 * This should never impact any application or cause data loss,
1470 * however it might take some time.
1471 *
1472 * This is not a 100% solution for all memory, but tries to be
1473 * ``good enough'' for the majority of memory.
1474 */
1475 int soft_offline_page(struct page *page, int flags)
1476 {
1477 int ret;
1478 unsigned long pfn = page_to_pfn(page);
1479 struct page *hpage = compound_trans_head(page);
1481 if (PageHuge(page))
1482 return soft_offline_huge_page(page, flags);
1483 if (PageTransHuge(hpage)) {
1484 if (PageAnon(hpage) && unlikely(split_huge_page(hpage))) {
1485 pr_info("soft offline: %#lx: failed to split THP\n",
1486 pfn);
1487 return -EBUSY;
1488 }
1489 }
1491 ret = get_any_page(page, pfn, flags);
1492 if (ret < 0)
1493 return ret;
1494 if (ret == 0)
1495 goto done;
1497 /*
1498 * Page cache page we can handle?
1499 */
1500 if (!PageLRU(page)) {
1501 /*
1502 * Try to free it.
1503 */
1504 put_page(page);
1505 shake_page(page, 1);
1507 /*
1508 * Did it turn free?
1509 */
1510 ret = get_any_page(page, pfn, 0);
1511 if (ret < 0)
1512 return ret;
1513 if (ret == 0)
1514 goto done;
1515 }
1516 if (!PageLRU(page)) {
1517 pr_info("soft_offline: %#lx: unknown non LRU page type %lx\n",
1518 pfn, page->flags);
1519 return -EIO;
1520 }
1522 lock_page(page);
1523 wait_on_page_writeback(page);
1525 /*
1526 * Synchronized using the page lock with memory_failure()
1527 */
1528 if (PageHWPoison(page)) {
1529 unlock_page(page);
1530 put_page(page);
1531 pr_info("soft offline: %#lx page already poisoned\n", pfn);
1532 return -EBUSY;
1533 }
1535 /*
1536 * Try to invalidate first. This should work for
1537 * non dirty unmapped page cache pages.
1538 */
1539 ret = invalidate_inode_page(page);
1540 unlock_page(page);
1541 /*
1542 * RED-PEN would be better to keep it isolated here, but we
1543 * would need to fix isolation locking first.
1544 */
1545 if (ret == 1) {
1546 put_page(page);
1547 ret = 0;
1548 pr_info("soft_offline: %#lx: invalidated\n", pfn);
1549 goto done;
1550 }
1552 /*
1553 * Simple invalidation didn't work.
1554 * Try to migrate to a new page instead. migrate.c
1555 * handles a large number of cases for us.
1556 */
1557 ret = isolate_lru_page(page);
1558 /*
1559 * Drop page reference which is came from get_any_page()
1560 * successful isolate_lru_page() already took another one.
1561 */
1562 put_page(page);
1563 if (!ret) {
1564 LIST_HEAD(pagelist);
1565 inc_zone_page_state(page, NR_ISOLATED_ANON +
1566 page_is_file_cache(page));
1567 list_add(&page->lru, &pagelist);
1568 ret = migrate_pages(&pagelist, new_page, MPOL_MF_MOVE_ALL,
1569 false, MIGRATE_SYNC,
1570 MR_MEMORY_FAILURE);
1571 if (ret) {
1572 putback_lru_pages(&pagelist);
1573 pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
1574 pfn, ret, page->flags);
1575 if (ret > 0)
1576 ret = -EIO;
1577 }
1578 } else {
1579 pr_info("soft offline: %#lx: isolation failed: %d, page count %d, type %lx\n",
1580 pfn, ret, page_count(page), page->flags);
1581 }
1582 if (ret)
1583 return ret;
1585 done:
1586 atomic_long_add(1, &mce_bad_pages);
1587 SetPageHWPoison(page);
1588 /* keep elevated page count for bad page */
1589 return ret;
1590 }