2 * Copyright (C) 2008, 2009 Intel Corporation
3 * Authors: Andi Kleen, Fengguang Wu
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.
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
13 * In addition there is a "soft offline" entry point that allows stop using
14 * not-yet-corrupted-by-suspicious pages without killing anything.
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.
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
34 * - hugetlb needs more code
35 * - kcore/oldmem/vmcore/mem/kmem check for hwpoison pages
36 * - pass bad pages to kdump next kernel
38 #include <linux/kernel.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>
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
)
81 struct address_space
*mapping
;
84 if (hwpoison_filter_dev_major
== ~0U &&
85 hwpoison_filter_dev_minor
== ~0U)
89 * page_mapping() does not accept slab pages.
94 mapping
= page_mapping(p
);
95 if (mapping
== NULL
|| mapping
->host
== NULL
)
98 dev
= mapping
->host
->i_sb
->s_dev
;
99 if (hwpoison_filter_dev_major
!= ~0U &&
100 hwpoison_filter_dev_major
!= MAJOR(dev
))
102 if (hwpoison_filter_dev_minor
!= ~0U &&
103 hwpoison_filter_dev_minor
!= MINOR(dev
))
109 static int hwpoison_filter_flags(struct page
*p
)
111 if (!hwpoison_filter_flags_mask
)
114 if ((stable_page_flags(p
) & hwpoison_filter_flags_mask
) ==
115 hwpoison_filter_flags_value
)
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
131 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
132 u64 hwpoison_filter_memcg
;
133 EXPORT_SYMBOL_GPL(hwpoison_filter_memcg
);
134 static int hwpoison_filter_task(struct page
*p
)
136 struct mem_cgroup
*mem
;
137 struct cgroup_subsys_state
*css
;
140 if (!hwpoison_filter_memcg
)
143 mem
= try_get_mem_cgroup_from_page(p
);
147 css
= mem_cgroup_css(mem
);
148 /* root_mem_cgroup has NULL dentries */
149 if (!css
->cgroup
->dentry
)
152 ino
= css
->cgroup
->dentry
->d_inode
->i_ino
;
155 if (ino
!= hwpoison_filter_memcg
)
161 static int hwpoison_filter_task(struct page
*p
) { return 0; }
164 int hwpoison_filter(struct page
*p
)
166 if (!hwpoison_filter_enable
)
169 if (hwpoison_filter_dev(p
))
172 if (hwpoison_filter_flags(p
))
175 if (hwpoison_filter_task(p
))
181 int hwpoison_filter(struct page
*p
)
187 EXPORT_SYMBOL_GPL(hwpoison_filter
);
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
194 static int kill_proc(struct task_struct
*t
, unsigned long addr
, int trapno
,
195 unsigned long pfn
, struct page
*page
, int flags
)
201 "MCE %#lx: Killing %s:%d due to hardware memory corruption\n",
202 pfn
, t
->comm
, t
->pid
);
203 si
.si_signo
= SIGBUS
;
205 si
.si_addr
= (void *)addr
;
206 #ifdef __ARCH_SI_TRAPNO
207 si
.si_trapno
= trapno
;
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
);
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?
221 si
.si_code
= BUS_MCEERR_AO
;
222 ret
= send_sig_info(SIGBUS
, &si
, t
); /* synchronous? */
225 printk(KERN_INFO
"MCE: Error sending signal to %s:%d: %d\n",
226 t
->comm
, t
->pid
, ret
);
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.
234 void shake_page(struct page
*p
, int access
)
241 if (PageLRU(p
) || is_free_buddy_page(p
))
246 * Only call shrink_slab here (which would also shrink other caches) if
247 * access is not potentially fatal.
252 struct shrink_control shrink
= {
253 .gfp_mask
= GFP_KERNEL
,
256 nr
= shrink_slab(&shrink
, 1000, 1000);
257 if (page_count(p
) == 1)
262 EXPORT_SYMBOL_GPL(shake_page
);
265 * Kill all processes that have a poisoned page mapped and then isolate
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
274 * There's no convenient way to get back to mapped processes
275 * from the VMAs. So do a brute-force search over all
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.
282 * Also there are some races possible while we get from the
283 * error detection to actually handle it.
288 struct task_struct
*tsk
;
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.
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?
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
)
314 tk
= kmalloc(sizeof(struct to_kill
), GFP_ATOMIC
);
317 "MCE: Out of memory while machine check handling\n");
321 tk
->addr
= page_address_in_vma(p
, vma
);
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.
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
);
335 get_task_struct(tsk
);
337 list_add_tail(&tk
->nd
, to_kill
);
341 * Kill the processes that have been collected earlier.
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
348 static void kill_procs(struct list_head
*to_kill
, int forcekill
, int trapno
,
349 int fail
, struct page
*page
, unsigned long pfn
,
352 struct to_kill
*tk
, *next
;
354 list_for_each_entry_safe (tk
, next
, to_kill
, nd
) {
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.
361 if (fail
|| tk
->addr_valid
== 0) {
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
);
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
374 else if (kill_proc(tk
->tsk
, tk
->addr
, trapno
,
375 pfn
, page
, flags
) < 0)
377 "MCE %#lx: Cannot send advisory machine check signal to %s:%d\n",
378 pfn
, tk
->tsk
->comm
, tk
->tsk
->pid
);
380 put_task_struct(tk
->tsk
);
385 static int task_early_kill(struct task_struct
*tsk
)
389 if (tsk
->flags
& PF_MCE_PROCESS
)
390 return !!(tsk
->flags
& PF_MCE_EARLY
);
391 return sysctl_memory_failure_early_kill
;
395 * Collect processes when the error hit an anonymous page.
397 static void collect_procs_anon(struct page
*page
, struct list_head
*to_kill
,
398 struct to_kill
**tkc
)
400 struct vm_area_struct
*vma
;
401 struct task_struct
*tsk
;
404 av
= page_lock_anon_vma(page
);
405 if (av
== NULL
) /* Not actually mapped anymore */
408 read_lock(&tasklist_lock
);
409 for_each_process (tsk
) {
410 struct anon_vma_chain
*vmac
;
412 if (!task_early_kill(tsk
))
414 list_for_each_entry(vmac
, &av
->head
, same_anon_vma
) {
416 if (!page_mapped_in_vma(page
, vma
))
418 if (vma
->vm_mm
== tsk
->mm
)
419 add_to_kill(tsk
, page
, vma
, to_kill
, tkc
);
422 read_unlock(&tasklist_lock
);
423 page_unlock_anon_vma(av
);
427 * Collect processes when the error hit a file mapped page.
429 static void collect_procs_file(struct page
*page
, struct list_head
*to_kill
,
430 struct to_kill
**tkc
)
432 struct vm_area_struct
*vma
;
433 struct task_struct
*tsk
;
434 struct prio_tree_iter iter
;
435 struct address_space
*mapping
= page
->mapping
;
437 mutex_lock(&mapping
->i_mmap_mutex
);
438 read_lock(&tasklist_lock
);
439 for_each_process(tsk
) {
440 pgoff_t pgoff
= page
->index
<< (PAGE_CACHE_SHIFT
- PAGE_SHIFT
);
442 if (!task_early_kill(tsk
))
445 vma_prio_tree_foreach(vma
, &iter
, &mapping
->i_mmap
, pgoff
,
448 * Send early kill signal to tasks where a vma covers
449 * the page but the corrupted page is not necessarily
450 * mapped it in its pte.
451 * Assume applications who requested early kill want
452 * to be informed of all such data corruptions.
454 if (vma
->vm_mm
== tsk
->mm
)
455 add_to_kill(tsk
, page
, vma
, to_kill
, tkc
);
458 read_unlock(&tasklist_lock
);
459 mutex_unlock(&mapping
->i_mmap_mutex
);
463 * Collect the processes who have the corrupted page mapped to kill.
464 * This is done in two steps for locking reasons.
465 * First preallocate one tokill structure outside the spin locks,
466 * so that we can kill at least one process reasonably reliable.
468 static void collect_procs(struct page
*page
, struct list_head
*tokill
)
475 tk
= kmalloc(sizeof(struct to_kill
), GFP_NOIO
);
479 collect_procs_anon(page
, tokill
, &tk
);
481 collect_procs_file(page
, tokill
, &tk
);
486 * Error handlers for various types of pages.
490 IGNORED
, /* Error: cannot be handled */
491 FAILED
, /* Error: handling failed */
492 DELAYED
, /* Will be handled later */
493 RECOVERED
, /* Successfully recovered */
496 static const char *action_name
[] = {
497 [IGNORED
] = "Ignored",
499 [DELAYED
] = "Delayed",
500 [RECOVERED
] = "Recovered",
504 * XXX: It is possible that a page is isolated from LRU cache,
505 * and then kept in swap cache or failed to remove from page cache.
506 * The page count will stop it from being freed by unpoison.
507 * Stress tests should be aware of this memory leak problem.
509 static int delete_from_lru_cache(struct page
*p
)
511 if (!isolate_lru_page(p
)) {
513 * Clear sensible page flags, so that the buddy system won't
514 * complain when the page is unpoison-and-freed.
517 ClearPageUnevictable(p
);
519 * drop the page count elevated by isolate_lru_page()
521 page_cache_release(p
);
528 * Error hit kernel page.
529 * Do nothing, try to be lucky and not touch this instead. For a few cases we
530 * could be more sophisticated.
532 static int me_kernel(struct page
*p
, unsigned long pfn
)
538 * Page in unknown state. Do nothing.
540 static int me_unknown(struct page
*p
, unsigned long pfn
)
542 printk(KERN_ERR
"MCE %#lx: Unknown page state\n", pfn
);
547 * Clean (or cleaned) page cache page.
549 static int me_pagecache_clean(struct page
*p
, unsigned long pfn
)
553 struct address_space
*mapping
;
555 delete_from_lru_cache(p
);
558 * For anonymous pages we're done the only reference left
559 * should be the one m_f() holds.
565 * Now truncate the page in the page cache. This is really
566 * more like a "temporary hole punch"
567 * Don't do this for block devices when someone else
568 * has a reference, because it could be file system metadata
569 * and that's not safe to truncate.
571 mapping
= page_mapping(p
);
574 * Page has been teared down in the meanwhile
580 * Truncation is a bit tricky. Enable it per file system for now.
582 * Open: to take i_mutex or not for this? Right now we don't.
584 if (mapping
->a_ops
->error_remove_page
) {
585 err
= mapping
->a_ops
->error_remove_page(mapping
, p
);
587 printk(KERN_INFO
"MCE %#lx: Failed to punch page: %d\n",
589 } else if (page_has_private(p
) &&
590 !try_to_release_page(p
, GFP_NOIO
)) {
591 pr_info("MCE %#lx: failed to release buffers\n", pfn
);
597 * If the file system doesn't support it just invalidate
598 * This fails on dirty or anything with private pages
600 if (invalidate_inode_page(p
))
603 printk(KERN_INFO
"MCE %#lx: Failed to invalidate\n",
610 * Dirty cache page page
611 * Issues: when the error hit a hole page the error is not properly
614 static int me_pagecache_dirty(struct page
*p
, unsigned long pfn
)
616 struct address_space
*mapping
= page_mapping(p
);
619 /* TBD: print more information about the file. */
622 * IO error will be reported by write(), fsync(), etc.
623 * who check the mapping.
624 * This way the application knows that something went
625 * wrong with its dirty file data.
627 * There's one open issue:
629 * The EIO will be only reported on the next IO
630 * operation and then cleared through the IO map.
631 * Normally Linux has two mechanisms to pass IO error
632 * first through the AS_EIO flag in the address space
633 * and then through the PageError flag in the page.
634 * Since we drop pages on memory failure handling the
635 * only mechanism open to use is through AS_AIO.
637 * This has the disadvantage that it gets cleared on
638 * the first operation that returns an error, while
639 * the PageError bit is more sticky and only cleared
640 * when the page is reread or dropped. If an
641 * application assumes it will always get error on
642 * fsync, but does other operations on the fd before
643 * and the page is dropped between then the error
644 * will not be properly reported.
646 * This can already happen even without hwpoisoned
647 * pages: first on metadata IO errors (which only
648 * report through AS_EIO) or when the page is dropped
651 * So right now we assume that the application DTRT on
652 * the first EIO, but we're not worse than other parts
655 mapping_set_error(mapping
, EIO
);
658 return me_pagecache_clean(p
, pfn
);
662 * Clean and dirty swap cache.
664 * Dirty swap cache page is tricky to handle. The page could live both in page
665 * cache and swap cache(ie. page is freshly swapped in). So it could be
666 * referenced concurrently by 2 types of PTEs:
667 * normal PTEs and swap PTEs. We try to handle them consistently by calling
668 * try_to_unmap(TTU_IGNORE_HWPOISON) to convert the normal PTEs to swap PTEs,
670 * - clear dirty bit to prevent IO
672 * - but keep in the swap cache, so that when we return to it on
673 * a later page fault, we know the application is accessing
674 * corrupted data and shall be killed (we installed simple
675 * interception code in do_swap_page to catch it).
677 * Clean swap cache pages can be directly isolated. A later page fault will
678 * bring in the known good data from disk.
680 static int me_swapcache_dirty(struct page
*p
, unsigned long pfn
)
683 /* Trigger EIO in shmem: */
684 ClearPageUptodate(p
);
686 if (!delete_from_lru_cache(p
))
692 static int me_swapcache_clean(struct page
*p
, unsigned long pfn
)
694 delete_from_swap_cache(p
);
696 if (!delete_from_lru_cache(p
))
703 * Huge pages. Needs work.
705 * - Error on hugepage is contained in hugepage unit (not in raw page unit.)
706 * To narrow down kill region to one page, we need to break up pmd.
708 static int me_huge_page(struct page
*p
, unsigned long pfn
)
711 struct page
*hpage
= compound_head(p
);
713 * We can safely recover from error on free or reserved (i.e.
714 * not in-use) hugepage by dequeuing it from freelist.
715 * To check whether a hugepage is in-use or not, we can't use
716 * page->lru because it can be used in other hugepage operations,
717 * such as __unmap_hugepage_range() and gather_surplus_pages().
718 * So instead we use page_mapping() and PageAnon().
719 * We assume that this function is called with page lock held,
720 * so there is no race between isolation and mapping/unmapping.
722 if (!(page_mapping(hpage
) || PageAnon(hpage
))) {
723 res
= dequeue_hwpoisoned_huge_page(hpage
);
731 * Various page states we can handle.
733 * A page state is defined by its current page->flags bits.
734 * The table matches them in order and calls the right handler.
736 * This is quite tricky because we can access page at any time
737 * in its live cycle, so all accesses have to be extremely careful.
739 * This is not complete. More states could be added.
740 * For any missing state don't attempt recovery.
743 #define dirty (1UL << PG_dirty)
744 #define sc (1UL << PG_swapcache)
745 #define unevict (1UL << PG_unevictable)
746 #define mlock (1UL << PG_mlocked)
747 #define writeback (1UL << PG_writeback)
748 #define lru (1UL << PG_lru)
749 #define swapbacked (1UL << PG_swapbacked)
750 #define head (1UL << PG_head)
751 #define tail (1UL << PG_tail)
752 #define compound (1UL << PG_compound)
753 #define slab (1UL << PG_slab)
754 #define reserved (1UL << PG_reserved)
756 static struct page_state
{
760 int (*action
)(struct page
*p
, unsigned long pfn
);
762 { reserved
, reserved
, "reserved kernel", me_kernel
},
764 * free pages are specially detected outside this table:
765 * PG_buddy pages only make a small fraction of all free pages.
769 * Could in theory check if slab page is free or if we can drop
770 * currently unused objects without touching them. But just
771 * treat it as standard kernel for now.
773 { slab
, slab
, "kernel slab", me_kernel
},
775 #ifdef CONFIG_PAGEFLAGS_EXTENDED
776 { head
, head
, "huge", me_huge_page
},
777 { tail
, tail
, "huge", me_huge_page
},
779 { compound
, compound
, "huge", me_huge_page
},
782 { sc
|dirty
, sc
|dirty
, "swapcache", me_swapcache_dirty
},
783 { sc
|dirty
, sc
, "swapcache", me_swapcache_clean
},
785 { unevict
|dirty
, unevict
|dirty
, "unevictable LRU", me_pagecache_dirty
},
786 { unevict
, unevict
, "unevictable LRU", me_pagecache_clean
},
788 { mlock
|dirty
, mlock
|dirty
, "mlocked LRU", me_pagecache_dirty
},
789 { mlock
, mlock
, "mlocked LRU", me_pagecache_clean
},
791 { lru
|dirty
, lru
|dirty
, "LRU", me_pagecache_dirty
},
792 { lru
|dirty
, lru
, "clean LRU", me_pagecache_clean
},
795 * Catchall entry: must be at end.
797 { 0, 0, "unknown page state", me_unknown
},
813 static void action_result(unsigned long pfn
, char *msg
, int result
)
815 struct page
*page
= pfn_to_page(pfn
);
817 printk(KERN_ERR
"MCE %#lx: %s%s page recovery: %s\n",
819 PageDirty(page
) ? "dirty " : "",
820 msg
, action_name
[result
]);
823 static int page_action(struct page_state
*ps
, struct page
*p
,
829 result
= ps
->action(p
, pfn
);
830 action_result(pfn
, ps
->msg
, result
);
832 count
= page_count(p
) - 1;
833 if (ps
->action
== me_swapcache_dirty
&& result
== DELAYED
)
837 "MCE %#lx: %s page still referenced by %d users\n",
838 pfn
, ps
->msg
, count
);
842 /* Could do more checks here if page looks ok */
844 * Could adjust zone counters here to correct for the missing page.
847 return (result
== RECOVERED
|| result
== DELAYED
) ? 0 : -EBUSY
;
851 * Do all that is necessary to remove user space mappings. Unmap
852 * the pages and send SIGBUS to the processes if the data was dirty.
854 static int hwpoison_user_mappings(struct page
*p
, unsigned long pfn
,
855 int trapno
, int flags
)
857 enum ttu_flags ttu
= TTU_UNMAP
| TTU_IGNORE_MLOCK
| TTU_IGNORE_ACCESS
;
858 struct address_space
*mapping
;
861 int kill
= 1, forcekill
;
862 struct page
*hpage
= compound_head(p
);
865 if (PageReserved(p
) || PageSlab(p
))
869 * This check implies we don't kill processes if their pages
870 * are in the swap cache early. Those are always late kills.
872 if (!page_mapped(hpage
))
878 if (PageSwapCache(p
)) {
880 "MCE %#lx: keeping poisoned page in swap cache\n", pfn
);
881 ttu
|= TTU_IGNORE_HWPOISON
;
885 * Propagate the dirty bit from PTEs to struct page first, because we
886 * need this to decide if we should kill or just drop the page.
887 * XXX: the dirty test could be racy: set_page_dirty() may not always
888 * be called inside page lock (it's recommended but not enforced).
890 mapping
= page_mapping(hpage
);
891 if (!(flags
& MF_MUST_KILL
) && !PageDirty(hpage
) && mapping
&&
892 mapping_cap_writeback_dirty(mapping
)) {
893 if (page_mkclean(hpage
)) {
897 ttu
|= TTU_IGNORE_HWPOISON
;
899 "MCE %#lx: corrupted page was clean: dropped without side effects\n",
905 * ppage: poisoned page
906 * if p is regular page(4k page)
907 * ppage == real poisoned page;
908 * else p is hugetlb or THP, ppage == head page.
912 if (PageTransHuge(hpage
)) {
914 * Verify that this isn't a hugetlbfs head page, the check for
915 * PageAnon is just for avoid tripping a split_huge_page
916 * internal debug check, as split_huge_page refuses to deal with
917 * anything that isn't an anon page. PageAnon can't go away fro
918 * under us because we hold a refcount on the hpage, without a
919 * refcount on the hpage. split_huge_page can't be safely called
920 * in the first place, having a refcount on the tail isn't
921 * enough * to be safe.
923 if (!PageHuge(hpage
) && PageAnon(hpage
)) {
924 if (unlikely(split_huge_page(hpage
))) {
926 * FIXME: if splitting THP is failed, it is
927 * better to stop the following operation rather
928 * than causing panic by unmapping. System might
929 * survive if the page is freed later.
932 "MCE %#lx: failed to split THP\n", pfn
);
934 BUG_ON(!PageHWPoison(p
));
937 /* THP is split, so ppage should be the real poisoned page. */
943 * First collect all the processes that have the page
944 * mapped in dirty form. This has to be done before try_to_unmap,
945 * because ttu takes the rmap data structures down.
947 * Error handling: We ignore errors here because
948 * there's nothing that can be done.
951 collect_procs(ppage
, &tokill
);
956 ret
= try_to_unmap(ppage
, ttu
);
957 if (ret
!= SWAP_SUCCESS
)
958 printk(KERN_ERR
"MCE %#lx: failed to unmap page (mapcount=%d)\n",
959 pfn
, page_mapcount(ppage
));
965 * Now that the dirty bit has been propagated to the
966 * struct page and all unmaps done we can decide if
967 * killing is needed or not. Only kill when the page
968 * was dirty or the process is not restartable,
969 * otherwise the tokill list is merely
970 * freed. When there was a problem unmapping earlier
971 * use a more force-full uncatchable kill to prevent
972 * any accesses to the poisoned memory.
974 forcekill
= PageDirty(ppage
) || (flags
& MF_MUST_KILL
);
975 kill_procs(&tokill
, forcekill
, trapno
,
976 ret
!= SWAP_SUCCESS
, p
, pfn
, flags
);
981 static void set_page_hwpoison_huge_page(struct page
*hpage
)
984 int nr_pages
= 1 << compound_trans_order(hpage
);
985 for (i
= 0; i
< nr_pages
; i
++)
986 SetPageHWPoison(hpage
+ i
);
989 static void clear_page_hwpoison_huge_page(struct page
*hpage
)
992 int nr_pages
= 1 << compound_trans_order(hpage
);
993 for (i
= 0; i
< nr_pages
; i
++)
994 ClearPageHWPoison(hpage
+ i
);
998 * memory_failure - Handle memory failure of a page.
999 * @pfn: Page Number of the corrupted page
1000 * @trapno: Trap number reported in the signal to user space.
1001 * @flags: fine tune action taken
1003 * This function is called by the low level machine check code
1004 * of an architecture when it detects hardware memory corruption
1005 * of a page. It tries its best to recover, which includes
1006 * dropping pages, killing processes etc.
1008 * The function is primarily of use for corruptions that
1009 * happen outside the current execution context (e.g. when
1010 * detected by a background scrubber)
1012 * Must run in process context (e.g. a work queue) with interrupts
1013 * enabled and no spinlocks hold.
1015 int memory_failure(unsigned long pfn
, int trapno
, int flags
)
1017 struct page_state
*ps
;
1021 unsigned int nr_pages
;
1023 if (!sysctl_memory_failure_recovery
)
1024 panic("Memory failure from trap %d on page %lx", trapno
, pfn
);
1026 if (!pfn_valid(pfn
)) {
1028 "MCE %#lx: memory outside kernel control\n",
1033 p
= pfn_to_page(pfn
);
1034 hpage
= compound_head(p
);
1035 if (TestSetPageHWPoison(p
)) {
1036 printk(KERN_ERR
"MCE %#lx: already hardware poisoned\n", pfn
);
1040 nr_pages
= 1 << compound_trans_order(hpage
);
1041 atomic_long_add(nr_pages
, &mce_bad_pages
);
1044 * We need/can do nothing about count=0 pages.
1045 * 1) it's a free page, and therefore in safe hand:
1046 * prep_new_page() will be the gate keeper.
1047 * 2) it's a free hugepage, which is also safe:
1048 * an affected hugepage will be dequeued from hugepage freelist,
1049 * so there's no concern about reusing it ever after.
1050 * 3) it's part of a non-compound high order page.
1051 * Implies some kernel user: cannot stop them from
1052 * R/W the page; let's pray that the page has been
1053 * used and will be freed some time later.
1054 * In fact it's dangerous to directly bump up page count from 0,
1055 * that may make page_freeze_refs()/page_unfreeze_refs() mismatch.
1057 if (!(flags
& MF_COUNT_INCREASED
) &&
1058 !get_page_unless_zero(hpage
)) {
1059 if (is_free_buddy_page(p
)) {
1060 action_result(pfn
, "free buddy", DELAYED
);
1062 } else if (PageHuge(hpage
)) {
1064 * Check "just unpoisoned", "filter hit", and
1065 * "race with other subpage."
1068 if (!PageHWPoison(hpage
)
1069 || (hwpoison_filter(p
) && TestClearPageHWPoison(p
))
1070 || (p
!= hpage
&& TestSetPageHWPoison(hpage
))) {
1071 atomic_long_sub(nr_pages
, &mce_bad_pages
);
1074 set_page_hwpoison_huge_page(hpage
);
1075 res
= dequeue_hwpoisoned_huge_page(hpage
);
1076 action_result(pfn
, "free huge",
1077 res
? IGNORED
: DELAYED
);
1081 action_result(pfn
, "high order kernel", IGNORED
);
1087 * We ignore non-LRU pages for good reasons.
1088 * - PG_locked is only well defined for LRU pages and a few others
1089 * - to avoid races with __set_page_locked()
1090 * - to avoid races with __SetPageSlab*() (and more non-atomic ops)
1091 * The check (unnecessarily) ignores LRU pages being isolated and
1092 * walked by the page reclaim code, however that's not a big loss.
1094 if (!PageHuge(p
) && !PageTransTail(p
)) {
1099 * shake_page could have turned it free.
1101 if (is_free_buddy_page(p
)) {
1102 action_result(pfn
, "free buddy, 2nd try",
1106 action_result(pfn
, "non LRU", IGNORED
);
1113 * Lock the page and wait for writeback to finish.
1114 * It's very difficult to mess with pages currently under IO
1115 * and in many cases impossible, so we just avoid it here.
1120 * unpoison always clear PG_hwpoison inside page lock
1122 if (!PageHWPoison(p
)) {
1123 printk(KERN_ERR
"MCE %#lx: just unpoisoned\n", pfn
);
1127 if (hwpoison_filter(p
)) {
1128 if (TestClearPageHWPoison(p
))
1129 atomic_long_sub(nr_pages
, &mce_bad_pages
);
1136 * For error on the tail page, we should set PG_hwpoison
1137 * on the head page to show that the hugepage is hwpoisoned
1139 if (PageHuge(p
) && PageTail(p
) && TestSetPageHWPoison(hpage
)) {
1140 action_result(pfn
, "hugepage already hardware poisoned",
1147 * Set PG_hwpoison on all pages in an error hugepage,
1148 * because containment is done in hugepage unit for now.
1149 * Since we have done TestSetPageHWPoison() for the head page with
1150 * page lock held, we can safely set PG_hwpoison bits on tail pages.
1153 set_page_hwpoison_huge_page(hpage
);
1155 wait_on_page_writeback(p
);
1158 * Now take care of user space mappings.
1159 * Abort on fail: __delete_from_page_cache() assumes unmapped page.
1161 if (hwpoison_user_mappings(p
, pfn
, trapno
, flags
) != SWAP_SUCCESS
) {
1162 printk(KERN_ERR
"MCE %#lx: cannot unmap page, give up\n", pfn
);
1168 * Torn down by someone else?
1170 if (PageLRU(p
) && !PageSwapCache(p
) && p
->mapping
== NULL
) {
1171 action_result(pfn
, "already truncated LRU", IGNORED
);
1177 for (ps
= error_states
;; ps
++) {
1178 if ((p
->flags
& ps
->mask
) == ps
->res
) {
1179 res
= page_action(ps
, p
, pfn
);
1187 EXPORT_SYMBOL_GPL(memory_failure
);
1189 #define MEMORY_FAILURE_FIFO_ORDER 4
1190 #define MEMORY_FAILURE_FIFO_SIZE (1 << MEMORY_FAILURE_FIFO_ORDER)
1192 struct memory_failure_entry
{
1198 struct memory_failure_cpu
{
1199 DECLARE_KFIFO(fifo
, struct memory_failure_entry
,
1200 MEMORY_FAILURE_FIFO_SIZE
);
1202 struct work_struct work
;
1205 static DEFINE_PER_CPU(struct memory_failure_cpu
, memory_failure_cpu
);
1208 * memory_failure_queue - Schedule handling memory failure of a page.
1209 * @pfn: Page Number of the corrupted page
1210 * @trapno: Trap number reported in the signal to user space.
1211 * @flags: Flags for memory failure handling
1213 * This function is called by the low level hardware error handler
1214 * when it detects hardware memory corruption of a page. It schedules
1215 * the recovering of error page, including dropping pages, killing
1218 * The function is primarily of use for corruptions that
1219 * happen outside the current execution context (e.g. when
1220 * detected by a background scrubber)
1222 * Can run in IRQ context.
1224 void memory_failure_queue(unsigned long pfn
, int trapno
, int flags
)
1226 struct memory_failure_cpu
*mf_cpu
;
1227 unsigned long proc_flags
;
1228 struct memory_failure_entry entry
= {
1234 mf_cpu
= &get_cpu_var(memory_failure_cpu
);
1235 spin_lock_irqsave(&mf_cpu
->lock
, proc_flags
);
1236 if (kfifo_put(&mf_cpu
->fifo
, &entry
))
1237 schedule_work_on(smp_processor_id(), &mf_cpu
->work
);
1239 pr_err("Memory failure: buffer overflow when queuing memory failure at 0x%#lx\n",
1241 spin_unlock_irqrestore(&mf_cpu
->lock
, proc_flags
);
1242 put_cpu_var(memory_failure_cpu
);
1244 EXPORT_SYMBOL_GPL(memory_failure_queue
);
1246 static void memory_failure_work_func(struct work_struct
*work
)
1248 struct memory_failure_cpu
*mf_cpu
;
1249 struct memory_failure_entry entry
= { 0, };
1250 unsigned long proc_flags
;
1253 mf_cpu
= &__get_cpu_var(memory_failure_cpu
);
1255 spin_lock_irqsave(&mf_cpu
->lock
, proc_flags
);
1256 gotten
= kfifo_get(&mf_cpu
->fifo
, &entry
);
1257 spin_unlock_irqrestore(&mf_cpu
->lock
, proc_flags
);
1260 memory_failure(entry
.pfn
, entry
.trapno
, entry
.flags
);
1264 static int __init
memory_failure_init(void)
1266 struct memory_failure_cpu
*mf_cpu
;
1269 for_each_possible_cpu(cpu
) {
1270 mf_cpu
= &per_cpu(memory_failure_cpu
, cpu
);
1271 spin_lock_init(&mf_cpu
->lock
);
1272 INIT_KFIFO(mf_cpu
->fifo
);
1273 INIT_WORK(&mf_cpu
->work
, memory_failure_work_func
);
1278 core_initcall(memory_failure_init
);
1281 * unpoison_memory - Unpoison a previously poisoned page
1282 * @pfn: Page number of the to be unpoisoned page
1284 * Software-unpoison a page that has been poisoned by
1285 * memory_failure() earlier.
1287 * This is only done on the software-level, so it only works
1288 * for linux injected failures, not real hardware failures
1290 * Returns 0 for success, otherwise -errno.
1292 int unpoison_memory(unsigned long pfn
)
1297 unsigned int nr_pages
;
1299 if (!pfn_valid(pfn
))
1302 p
= pfn_to_page(pfn
);
1303 page
= compound_head(p
);
1305 if (!PageHWPoison(p
)) {
1306 pr_info("MCE: Page was already unpoisoned %#lx\n", pfn
);
1310 nr_pages
= 1 << compound_trans_order(page
);
1312 if (!get_page_unless_zero(page
)) {
1314 * Since HWPoisoned hugepage should have non-zero refcount,
1315 * race between memory failure and unpoison seems to happen.
1316 * In such case unpoison fails and memory failure runs
1319 if (PageHuge(page
)) {
1320 pr_info("MCE: Memory failure is now running on free hugepage %#lx\n", pfn
);
1323 if (TestClearPageHWPoison(p
))
1324 atomic_long_sub(nr_pages
, &mce_bad_pages
);
1325 pr_info("MCE: Software-unpoisoned free page %#lx\n", pfn
);
1331 * This test is racy because PG_hwpoison is set outside of page lock.
1332 * That's acceptable because that won't trigger kernel panic. Instead,
1333 * the PG_hwpoison page will be caught and isolated on the entrance to
1334 * the free buddy page pool.
1336 if (TestClearPageHWPoison(page
)) {
1337 pr_info("MCE: Software-unpoisoned page %#lx\n", pfn
);
1338 atomic_long_sub(nr_pages
, &mce_bad_pages
);
1341 clear_page_hwpoison_huge_page(page
);
1351 EXPORT_SYMBOL(unpoison_memory
);
1353 static struct page
*new_page(struct page
*p
, unsigned long private, int **x
)
1355 int nid
= page_to_nid(p
);
1357 return alloc_huge_page_node(page_hstate(compound_head(p
)),
1360 return alloc_pages_exact_node(nid
, GFP_HIGHUSER_MOVABLE
, 0);
1364 * Safely get reference count of an arbitrary page.
1365 * Returns 0 for a free page, -EIO for a zero refcount page
1366 * that is not free, and 1 for any other page type.
1367 * For 1 the page is returned with increased page count, otherwise not.
1369 static int get_any_page(struct page
*p
, unsigned long pfn
, int flags
)
1373 if (flags
& MF_COUNT_INCREASED
)
1377 * The lock_memory_hotplug prevents a race with memory hotplug.
1378 * This is a big hammer, a better would be nicer.
1380 lock_memory_hotplug();
1383 * Isolate the page, so that it doesn't get reallocated if it
1386 set_migratetype_isolate(p
);
1388 * When the target page is a free hugepage, just remove it
1389 * from free hugepage list.
1391 if (!get_page_unless_zero(compound_head(p
))) {
1393 pr_info("%s: %#lx free huge page\n", __func__
, pfn
);
1394 ret
= dequeue_hwpoisoned_huge_page(compound_head(p
));
1395 } else if (is_free_buddy_page(p
)) {
1396 pr_info("%s: %#lx free buddy page\n", __func__
, pfn
);
1397 /* Set hwpoison bit while page is still isolated */
1401 pr_info("%s: %#lx: unknown zero refcount page type %lx\n",
1402 __func__
, pfn
, p
->flags
);
1406 /* Not a free page */
1409 unset_migratetype_isolate(p
, MIGRATE_MOVABLE
);
1410 unlock_memory_hotplug();
1414 static int soft_offline_huge_page(struct page
*page
, int flags
)
1417 unsigned long pfn
= page_to_pfn(page
);
1418 struct page
*hpage
= compound_head(page
);
1419 LIST_HEAD(pagelist
);
1421 ret
= get_any_page(page
, pfn
, flags
);
1427 if (PageHWPoison(hpage
)) {
1429 pr_info("soft offline: %#lx hugepage already poisoned\n", pfn
);
1433 /* Keep page count to indicate a given hugepage is isolated. */
1435 list_add(&hpage
->lru
, &pagelist
);
1436 ret
= migrate_huge_pages(&pagelist
, new_page
, MPOL_MF_MOVE_ALL
, false,
1439 struct page
*page1
, *page2
;
1440 list_for_each_entry_safe(page1
, page2
, &pagelist
, lru
)
1443 pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
1444 pfn
, ret
, page
->flags
);
1450 if (!PageHWPoison(hpage
))
1451 atomic_long_add(1 << compound_trans_order(hpage
), &mce_bad_pages
);
1452 set_page_hwpoison_huge_page(hpage
);
1453 dequeue_hwpoisoned_huge_page(hpage
);
1454 /* keep elevated page count for bad page */
1459 * soft_offline_page - Soft offline a page.
1460 * @page: page to offline
1461 * @flags: flags. Same as memory_failure().
1463 * Returns 0 on success, otherwise negated errno.
1465 * Soft offline a page, by migration or invalidation,
1466 * without killing anything. This is for the case when
1467 * a page is not corrupted yet (so it's still valid to access),
1468 * but has had a number of corrected errors and is better taken
1471 * The actual policy on when to do that is maintained by
1474 * This should never impact any application or cause data loss,
1475 * however it might take some time.
1477 * This is not a 100% solution for all memory, but tries to be
1478 * ``good enough'' for the majority of memory.
1480 int soft_offline_page(struct page
*page
, int flags
)
1483 unsigned long pfn
= page_to_pfn(page
);
1486 return soft_offline_huge_page(page
, flags
);
1488 ret
= get_any_page(page
, pfn
, flags
);
1495 * Page cache page we can handle?
1497 if (!PageLRU(page
)) {
1502 shake_page(page
, 1);
1507 ret
= get_any_page(page
, pfn
, 0);
1513 if (!PageLRU(page
)) {
1514 pr_info("soft_offline: %#lx: unknown non LRU page type %lx\n",
1520 wait_on_page_writeback(page
);
1523 * Synchronized using the page lock with memory_failure()
1525 if (PageHWPoison(page
)) {
1528 pr_info("soft offline: %#lx page already poisoned\n", pfn
);
1533 * Try to invalidate first. This should work for
1534 * non dirty unmapped page cache pages.
1536 ret
= invalidate_inode_page(page
);
1539 * RED-PEN would be better to keep it isolated here, but we
1540 * would need to fix isolation locking first.
1545 pr_info("soft_offline: %#lx: invalidated\n", pfn
);
1550 * Simple invalidation didn't work.
1551 * Try to migrate to a new page instead. migrate.c
1552 * handles a large number of cases for us.
1554 ret
= isolate_lru_page(page
);
1556 * Drop page reference which is came from get_any_page()
1557 * successful isolate_lru_page() already took another one.
1561 LIST_HEAD(pagelist
);
1562 inc_zone_page_state(page
, NR_ISOLATED_ANON
+
1563 page_is_file_cache(page
));
1564 list_add(&page
->lru
, &pagelist
);
1565 ret
= migrate_pages(&pagelist
, new_page
, MPOL_MF_MOVE_ALL
,
1566 false, MIGRATE_SYNC
);
1568 putback_lru_pages(&pagelist
);
1569 pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
1570 pfn
, ret
, page
->flags
);
1575 pr_info("soft offline: %#lx: isolation failed: %d, page count %d, type %lx\n",
1576 pfn
, ret
, page_count(page
), page
->flags
);
1582 atomic_long_add(1, &mce_bad_pages
);
1583 SetPageHWPoison(page
);
1584 /* keep elevated page count for bad page */