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TOMOYO Linux Cross Reference
Linux/mm/memory-failure.c

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

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