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 2bit ECC memory or cache
13 * Handles page cache pages in various states. The tricky part
14 * here is that we can access any page asynchronous to other VM
15 * users, because memory failures could happen anytime and anywhere,
16 * possibly violating some of their assumptions. This is why this code
17 * has to be extremely careful. Generally it tries to use normal locking
18 * rules, as in get the standard locks, even if that means the
19 * error handling takes potentially a long time.
21 * The operation to map back from RMAP chains to processes has to walk
22 * the complete process list and has non linear complexity with the number
23 * mappings. In short it can be quite slow. But since memory corruptions
24 * are rare we hope to get away with this.
29 * - hugetlb needs more code
30 * - kcore/oldmem/vmcore/mem/kmem check for hwpoison pages
31 * - pass bad pages to kdump next kernel
33 #define DEBUG 1 /* remove me in 2.6.34 */
34 #include <linux/kernel.h>
36 #include <linux/page-flags.h>
37 #include <linux/kernel-page-flags.h>
38 #include <linux/sched.h>
39 #include <linux/ksm.h>
40 #include <linux/rmap.h>
41 #include <linux/pagemap.h>
42 #include <linux/swap.h>
43 #include <linux/backing-dev.h>
46 int sysctl_memory_failure_early_kill __read_mostly = 0;
48 int sysctl_memory_failure_recovery __read_mostly = 1;
50 atomic_long_t mce_bad_pages __read_mostly = ATOMIC_LONG_INIT(0);
52 u32 hwpoison_filter_dev_major = ~0U;
53 u32 hwpoison_filter_dev_minor = ~0U;
54 u64 hwpoison_filter_flags_mask;
55 u64 hwpoison_filter_flags_value;
56 EXPORT_SYMBOL_GPL(hwpoison_filter_dev_major);
57 EXPORT_SYMBOL_GPL(hwpoison_filter_dev_minor);
58 EXPORT_SYMBOL_GPL(hwpoison_filter_flags_mask);
59 EXPORT_SYMBOL_GPL(hwpoison_filter_flags_value);
61 static int hwpoison_filter_dev(struct page *p)
63 struct address_space *mapping;
66 if (hwpoison_filter_dev_major == ~0U &&
67 hwpoison_filter_dev_minor == ~0U)
71 * page_mapping() does not accept slab page
76 mapping = page_mapping(p);
77 if (mapping == NULL || mapping->host == NULL)
80 dev = mapping->host->i_sb->s_dev;
81 if (hwpoison_filter_dev_major != ~0U &&
82 hwpoison_filter_dev_major != MAJOR(dev))
84 if (hwpoison_filter_dev_minor != ~0U &&
85 hwpoison_filter_dev_minor != MINOR(dev))
91 static int hwpoison_filter_flags(struct page *p)
93 if (!hwpoison_filter_flags_mask)
96 if ((stable_page_flags(p) & hwpoison_filter_flags_mask) ==
97 hwpoison_filter_flags_value)
104 * This allows stress tests to limit test scope to a collection of tasks
105 * by putting them under some memcg. This prevents killing unrelated/important
106 * processes such as /sbin/init. Note that the target task may share clean
107 * pages with init (eg. libc text), which is harmless. If the target task
108 * share _dirty_ pages with another task B, the test scheme must make sure B
109 * is also included in the memcg. At last, due to race conditions this filter
110 * can only guarantee that the page either belongs to the memcg tasks, or is
113 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
114 u64 hwpoison_filter_memcg;
115 EXPORT_SYMBOL_GPL(hwpoison_filter_memcg);
116 static int hwpoison_filter_task(struct page *p)
118 struct mem_cgroup *mem;
119 struct cgroup_subsys_state *css;
122 if (!hwpoison_filter_memcg)
125 mem = try_get_mem_cgroup_from_page(p);
129 css = mem_cgroup_css(mem);
130 /* root_mem_cgroup has NULL dentries */
131 if (!css->cgroup->dentry)
134 ino = css->cgroup->dentry->d_inode->i_ino;
137 if (ino != hwpoison_filter_memcg)
143 static int hwpoison_filter_task(struct page *p) { return 0; }
146 int hwpoison_filter(struct page *p)
148 if (hwpoison_filter_dev(p))
151 if (hwpoison_filter_flags(p))
154 if (hwpoison_filter_task(p))
159 EXPORT_SYMBOL_GPL(hwpoison_filter);
162 * Send all the processes who have the page mapped an ``action optional''
165 static int kill_proc_ao(struct task_struct *t, unsigned long addr, int trapno,
172 "MCE %#lx: Killing %s:%d early due to hardware memory corruption\n",
173 pfn, t->comm, t->pid);
174 si.si_signo = SIGBUS;
176 si.si_code = BUS_MCEERR_AO;
177 si.si_addr = (void *)addr;
178 #ifdef __ARCH_SI_TRAPNO
179 si.si_trapno = trapno;
181 si.si_addr_lsb = PAGE_SHIFT;
183 * Don't use force here, it's convenient if the signal
184 * can be temporarily blocked.
185 * This could cause a loop when the user sets SIGBUS
186 * to SIG_IGN, but hopefully noone will do that?
188 ret = send_sig_info(SIGBUS, &si, t); /* synchronous? */
190 printk(KERN_INFO "MCE: Error sending signal to %s:%d: %d\n",
191 t->comm, t->pid, ret);
196 * When a unknown page type is encountered drain as many buffers as possible
197 * in the hope to turn the page into a LRU or free page, which we can handle.
199 void shake_page(struct page *p)
206 if (PageLRU(p) || is_free_buddy_page(p))
210 * Could call shrink_slab here (which would also
211 * shrink other caches). Unfortunately that might
212 * also access the corrupted page, which could be fatal.
215 EXPORT_SYMBOL_GPL(shake_page);
218 * Kill all processes that have a poisoned page mapped and then isolate
222 * Find all processes having the page mapped and kill them.
223 * But we keep a page reference around so that the page is not
224 * actually freed yet.
225 * Then stash the page away
227 * There's no convenient way to get back to mapped processes
228 * from the VMAs. So do a brute-force search over all
231 * Remember that machine checks are not common (or rather
232 * if they are common you have other problems), so this shouldn't
233 * be a performance issue.
235 * Also there are some races possible while we get from the
236 * error detection to actually handle it.
241 struct task_struct *tsk;
243 unsigned addr_valid:1;
247 * Failure handling: if we can't find or can't kill a process there's
248 * not much we can do. We just print a message and ignore otherwise.
252 * Schedule a process for later kill.
253 * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
254 * TBD would GFP_NOIO be enough?
256 static void add_to_kill(struct task_struct *tsk, struct page *p,
257 struct vm_area_struct *vma,
258 struct list_head *to_kill,
259 struct to_kill **tkc)
267 tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
270 "MCE: Out of memory while machine check handling\n");
274 tk->addr = page_address_in_vma(p, vma);
278 * In theory we don't have to kill when the page was
279 * munmaped. But it could be also a mremap. Since that's
280 * likely very rare kill anyways just out of paranoia, but use
281 * a SIGKILL because the error is not contained anymore.
283 if (tk->addr == -EFAULT) {
284 pr_debug("MCE: Unable to find user space address %lx in %s\n",
285 page_to_pfn(p), tsk->comm);
288 get_task_struct(tsk);
290 list_add_tail(&tk->nd, to_kill);
294 * Kill the processes that have been collected earlier.
296 * Only do anything when DOIT is set, otherwise just free the list
297 * (this is used for clean pages which do not need killing)
298 * Also when FAIL is set do a force kill because something went
301 static void kill_procs_ao(struct list_head *to_kill, int doit, int trapno,
302 int fail, unsigned long pfn)
304 struct to_kill *tk, *next;
306 list_for_each_entry_safe (tk, next, to_kill, nd) {
309 * In case something went wrong with munmapping
310 * make sure the process doesn't catch the
311 * signal and then access the memory. Just kill it.
312 * the signal handlers
314 if (fail || tk->addr_valid == 0) {
316 "MCE %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n",
317 pfn, tk->tsk->comm, tk->tsk->pid);
318 force_sig(SIGKILL, tk->tsk);
322 * In theory the process could have mapped
323 * something else on the address in-between. We could
324 * check for that, but we need to tell the
327 else if (kill_proc_ao(tk->tsk, tk->addr, trapno,
330 "MCE %#lx: Cannot send advisory machine check signal to %s:%d\n",
331 pfn, tk->tsk->comm, tk->tsk->pid);
333 put_task_struct(tk->tsk);
338 static int task_early_kill(struct task_struct *tsk)
342 if (tsk->flags & PF_MCE_PROCESS)
343 return !!(tsk->flags & PF_MCE_EARLY);
344 return sysctl_memory_failure_early_kill;
348 * Collect processes when the error hit an anonymous page.
350 static void collect_procs_anon(struct page *page, struct list_head *to_kill,
351 struct to_kill **tkc)
353 struct vm_area_struct *vma;
354 struct task_struct *tsk;
357 read_lock(&tasklist_lock);
358 av = page_lock_anon_vma(page);
359 if (av == NULL) /* Not actually mapped anymore */
361 for_each_process (tsk) {
362 if (!task_early_kill(tsk))
364 list_for_each_entry (vma, &av->head, anon_vma_node) {
365 if (!page_mapped_in_vma(page, vma))
367 if (vma->vm_mm == tsk->mm)
368 add_to_kill(tsk, page, vma, to_kill, tkc);
371 page_unlock_anon_vma(av);
373 read_unlock(&tasklist_lock);
377 * Collect processes when the error hit a file mapped page.
379 static void collect_procs_file(struct page *page, struct list_head *to_kill,
380 struct to_kill **tkc)
382 struct vm_area_struct *vma;
383 struct task_struct *tsk;
384 struct prio_tree_iter iter;
385 struct address_space *mapping = page->mapping;
388 * A note on the locking order between the two locks.
389 * We don't rely on this particular order.
390 * If you have some other code that needs a different order
391 * feel free to switch them around. Or add a reverse link
392 * from mm_struct to task_struct, then this could be all
393 * done without taking tasklist_lock and looping over all tasks.
396 read_lock(&tasklist_lock);
397 spin_lock(&mapping->i_mmap_lock);
398 for_each_process(tsk) {
399 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
401 if (!task_early_kill(tsk))
404 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff,
407 * Send early kill signal to tasks where a vma covers
408 * the page but the corrupted page is not necessarily
409 * mapped it in its pte.
410 * Assume applications who requested early kill want
411 * to be informed of all such data corruptions.
413 if (vma->vm_mm == tsk->mm)
414 add_to_kill(tsk, page, vma, to_kill, tkc);
417 spin_unlock(&mapping->i_mmap_lock);
418 read_unlock(&tasklist_lock);
422 * Collect the processes who have the corrupted page mapped to kill.
423 * This is done in two steps for locking reasons.
424 * First preallocate one tokill structure outside the spin locks,
425 * so that we can kill at least one process reasonably reliable.
427 static void collect_procs(struct page *page, struct list_head *tokill)
434 tk = kmalloc(sizeof(struct to_kill), GFP_NOIO);
438 collect_procs_anon(page, tokill, &tk);
440 collect_procs_file(page, tokill, &tk);
445 * Error handlers for various types of pages.
449 IGNORED, /* Error: cannot be handled */
450 FAILED, /* Error: handling failed */
451 DELAYED, /* Will be handled later */
452 RECOVERED, /* Successfully recovered */
455 static const char *action_name[] = {
456 [IGNORED] = "Ignored",
458 [DELAYED] = "Delayed",
459 [RECOVERED] = "Recovered",
463 * XXX: It is possible that a page is isolated from LRU cache,
464 * and then kept in swap cache or failed to remove from page cache.
465 * The page count will stop it from being freed by unpoison.
466 * Stress tests should be aware of this memory leak problem.
468 static int delete_from_lru_cache(struct page *p)
470 if (!isolate_lru_page(p)) {
472 * Clear sensible page flags, so that the buddy system won't
473 * complain when the page is unpoison-and-freed.
476 ClearPageUnevictable(p);
478 * drop the page count elevated by isolate_lru_page()
480 page_cache_release(p);
487 * Error hit kernel page.
488 * Do nothing, try to be lucky and not touch this instead. For a few cases we
489 * could be more sophisticated.
491 static int me_kernel(struct page *p, unsigned long pfn)
497 * Page in unknown state. Do nothing.
499 static int me_unknown(struct page *p, unsigned long pfn)
501 printk(KERN_ERR "MCE %#lx: Unknown page state\n", pfn);
506 * Clean (or cleaned) page cache page.
508 static int me_pagecache_clean(struct page *p, unsigned long pfn)
512 struct address_space *mapping;
514 delete_from_lru_cache(p);
517 * For anonymous pages we're done the only reference left
518 * should be the one m_f() holds.
524 * Now truncate the page in the page cache. This is really
525 * more like a "temporary hole punch"
526 * Don't do this for block devices when someone else
527 * has a reference, because it could be file system metadata
528 * and that's not safe to truncate.
530 mapping = page_mapping(p);
533 * Page has been teared down in the meanwhile
539 * Truncation is a bit tricky. Enable it per file system for now.
541 * Open: to take i_mutex or not for this? Right now we don't.
543 if (mapping->a_ops->error_remove_page) {
544 err = mapping->a_ops->error_remove_page(mapping, p);
546 printk(KERN_INFO "MCE %#lx: Failed to punch page: %d\n",
548 } else if (page_has_private(p) &&
549 !try_to_release_page(p, GFP_NOIO)) {
550 pr_debug("MCE %#lx: failed to release buffers\n", pfn);
556 * If the file system doesn't support it just invalidate
557 * This fails on dirty or anything with private pages
559 if (invalidate_inode_page(p))
562 printk(KERN_INFO "MCE %#lx: Failed to invalidate\n",
569 * Dirty cache page page
570 * Issues: when the error hit a hole page the error is not properly
573 static int me_pagecache_dirty(struct page *p, unsigned long pfn)
575 struct address_space *mapping = page_mapping(p);
578 /* TBD: print more information about the file. */
581 * IO error will be reported by write(), fsync(), etc.
582 * who check the mapping.
583 * This way the application knows that something went
584 * wrong with its dirty file data.
586 * There's one open issue:
588 * The EIO will be only reported on the next IO
589 * operation and then cleared through the IO map.
590 * Normally Linux has two mechanisms to pass IO error
591 * first through the AS_EIO flag in the address space
592 * and then through the PageError flag in the page.
593 * Since we drop pages on memory failure handling the
594 * only mechanism open to use is through AS_AIO.
596 * This has the disadvantage that it gets cleared on
597 * the first operation that returns an error, while
598 * the PageError bit is more sticky and only cleared
599 * when the page is reread or dropped. If an
600 * application assumes it will always get error on
601 * fsync, but does other operations on the fd before
602 * and the page is dropped inbetween then the error
603 * will not be properly reported.
605 * This can already happen even without hwpoisoned
606 * pages: first on metadata IO errors (which only
607 * report through AS_EIO) or when the page is dropped
610 * So right now we assume that the application DTRT on
611 * the first EIO, but we're not worse than other parts
614 mapping_set_error(mapping, EIO);
617 return me_pagecache_clean(p, pfn);
621 * Clean and dirty swap cache.
623 * Dirty swap cache page is tricky to handle. The page could live both in page
624 * cache and swap cache(ie. page is freshly swapped in). So it could be
625 * referenced concurrently by 2 types of PTEs:
626 * normal PTEs and swap PTEs. We try to handle them consistently by calling
627 * try_to_unmap(TTU_IGNORE_HWPOISON) to convert the normal PTEs to swap PTEs,
629 * - clear dirty bit to prevent IO
631 * - but keep in the swap cache, so that when we return to it on
632 * a later page fault, we know the application is accessing
633 * corrupted data and shall be killed (we installed simple
634 * interception code in do_swap_page to catch it).
636 * Clean swap cache pages can be directly isolated. A later page fault will
637 * bring in the known good data from disk.
639 static int me_swapcache_dirty(struct page *p, unsigned long pfn)
642 /* Trigger EIO in shmem: */
643 ClearPageUptodate(p);
645 if (!delete_from_lru_cache(p))
651 static int me_swapcache_clean(struct page *p, unsigned long pfn)
653 delete_from_swap_cache(p);
655 if (!delete_from_lru_cache(p))
662 * Huge pages. Needs work.
664 * No rmap support so we cannot find the original mapper. In theory could walk
665 * all MMs and look for the mappings, but that would be non atomic and racy.
666 * Need rmap for hugepages for this. Alternatively we could employ a heuristic,
667 * like just walking the current process and hoping it has it mapped (that
668 * should be usually true for the common "shared database cache" case)
669 * Should handle free huge pages and dequeue them too, but this needs to
670 * handle huge page accounting correctly.
672 static int me_huge_page(struct page *p, unsigned long pfn)
678 * Various page states we can handle.
680 * A page state is defined by its current page->flags bits.
681 * The table matches them in order and calls the right handler.
683 * This is quite tricky because we can access page at any time
684 * in its live cycle, so all accesses have to be extremly careful.
686 * This is not complete. More states could be added.
687 * For any missing state don't attempt recovery.
690 #define dirty (1UL << PG_dirty)
691 #define sc (1UL << PG_swapcache)
692 #define unevict (1UL << PG_unevictable)
693 #define mlock (1UL << PG_mlocked)
694 #define writeback (1UL << PG_writeback)
695 #define lru (1UL << PG_lru)
696 #define swapbacked (1UL << PG_swapbacked)
697 #define head (1UL << PG_head)
698 #define tail (1UL << PG_tail)
699 #define compound (1UL << PG_compound)
700 #define slab (1UL << PG_slab)
701 #define reserved (1UL << PG_reserved)
703 static struct page_state {
707 int (*action)(struct page *p, unsigned long pfn);
709 { reserved, reserved, "reserved kernel", me_kernel },
711 * free pages are specially detected outside this table:
712 * PG_buddy pages only make a small fraction of all free pages.
716 * Could in theory check if slab page is free or if we can drop
717 * currently unused objects without touching them. But just
718 * treat it as standard kernel for now.
720 { slab, slab, "kernel slab", me_kernel },
722 #ifdef CONFIG_PAGEFLAGS_EXTENDED
723 { head, head, "huge", me_huge_page },
724 { tail, tail, "huge", me_huge_page },
726 { compound, compound, "huge", me_huge_page },
729 { sc|dirty, sc|dirty, "swapcache", me_swapcache_dirty },
730 { sc|dirty, sc, "swapcache", me_swapcache_clean },
732 { unevict|dirty, unevict|dirty, "unevictable LRU", me_pagecache_dirty},
733 { unevict, unevict, "unevictable LRU", me_pagecache_clean},
735 { mlock|dirty, mlock|dirty, "mlocked LRU", me_pagecache_dirty },
736 { mlock, mlock, "mlocked LRU", me_pagecache_clean },
738 { lru|dirty, lru|dirty, "LRU", me_pagecache_dirty },
739 { lru|dirty, lru, "clean LRU", me_pagecache_clean },
742 * Catchall entry: must be at end.
744 { 0, 0, "unknown page state", me_unknown },
747 static void action_result(unsigned long pfn, char *msg, int result)
749 struct page *page = pfn_to_page(pfn);
751 printk(KERN_ERR "MCE %#lx: %s%s page recovery: %s\n",
753 PageDirty(page) ? "dirty " : "",
754 msg, action_name[result]);
757 static int page_action(struct page_state *ps, struct page *p,
763 result = ps->action(p, pfn);
764 action_result(pfn, ps->msg, result);
766 count = page_count(p) - 1;
767 if (ps->action == me_swapcache_dirty && result == DELAYED)
771 "MCE %#lx: %s page still referenced by %d users\n",
772 pfn, ps->msg, count);
776 /* Could do more checks here if page looks ok */
778 * Could adjust zone counters here to correct for the missing page.
781 return (result == RECOVERED || result == DELAYED) ? 0 : -EBUSY;
784 #define N_UNMAP_TRIES 5
787 * Do all that is necessary to remove user space mappings. Unmap
788 * the pages and send SIGBUS to the processes if the data was dirty.
790 static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
793 enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
794 struct address_space *mapping;
800 if (PageReserved(p) || PageSlab(p))
804 * This check implies we don't kill processes if their pages
805 * are in the swap cache early. Those are always late kills.
810 if (PageCompound(p) || PageKsm(p))
813 if (PageSwapCache(p)) {
815 "MCE %#lx: keeping poisoned page in swap cache\n", pfn);
816 ttu |= TTU_IGNORE_HWPOISON;
820 * Propagate the dirty bit from PTEs to struct page first, because we
821 * need this to decide if we should kill or just drop the page.
822 * XXX: the dirty test could be racy: set_page_dirty() may not always
823 * be called inside page lock (it's recommended but not enforced).
825 mapping = page_mapping(p);
826 if (!PageDirty(p) && mapping && mapping_cap_writeback_dirty(mapping)) {
827 if (page_mkclean(p)) {
831 ttu |= TTU_IGNORE_HWPOISON;
833 "MCE %#lx: corrupted page was clean: dropped without side effects\n",
839 * First collect all the processes that have the page
840 * mapped in dirty form. This has to be done before try_to_unmap,
841 * because ttu takes the rmap data structures down.
843 * Error handling: We ignore errors here because
844 * there's nothing that can be done.
847 collect_procs(p, &tokill);
850 * try_to_unmap can fail temporarily due to races.
851 * Try a few times (RED-PEN better strategy?)
853 for (i = 0; i < N_UNMAP_TRIES; i++) {
854 ret = try_to_unmap(p, ttu);
855 if (ret == SWAP_SUCCESS)
857 pr_debug("MCE %#lx: try_to_unmap retry needed %d\n", pfn, ret);
860 if (ret != SWAP_SUCCESS)
861 printk(KERN_ERR "MCE %#lx: failed to unmap page (mapcount=%d)\n",
862 pfn, page_mapcount(p));
865 * Now that the dirty bit has been propagated to the
866 * struct page and all unmaps done we can decide if
867 * killing is needed or not. Only kill when the page
868 * was dirty, otherwise the tokill list is merely
869 * freed. When there was a problem unmapping earlier
870 * use a more force-full uncatchable kill to prevent
871 * any accesses to the poisoned memory.
873 kill_procs_ao(&tokill, !!PageDirty(p), trapno,
874 ret != SWAP_SUCCESS, pfn);
879 int __memory_failure(unsigned long pfn, int trapno, int flags)
881 struct page_state *ps;
885 if (!sysctl_memory_failure_recovery)
886 panic("Memory failure from trap %d on page %lx", trapno, pfn);
888 if (!pfn_valid(pfn)) {
890 "MCE %#lx: memory outside kernel control\n",
895 p = pfn_to_page(pfn);
896 if (TestSetPageHWPoison(p)) {
897 printk(KERN_ERR "MCE %#lx: already hardware poisoned\n", pfn);
901 atomic_long_add(1, &mce_bad_pages);
904 * We need/can do nothing about count=0 pages.
905 * 1) it's a free page, and therefore in safe hand:
906 * prep_new_page() will be the gate keeper.
907 * 2) it's part of a non-compound high order page.
908 * Implies some kernel user: cannot stop them from
909 * R/W the page; let's pray that the page has been
910 * used and will be freed some time later.
911 * In fact it's dangerous to directly bump up page count from 0,
912 * that may make page_freeze_refs()/page_unfreeze_refs() mismatch.
914 if (!(flags & MF_COUNT_INCREASED) &&
915 !get_page_unless_zero(compound_head(p))) {
916 if (is_free_buddy_page(p)) {
917 action_result(pfn, "free buddy", DELAYED);
920 action_result(pfn, "high order kernel", IGNORED);
926 * We ignore non-LRU pages for good reasons.
927 * - PG_locked is only well defined for LRU pages and a few others
928 * - to avoid races with __set_page_locked()
929 * - to avoid races with __SetPageSlab*() (and more non-atomic ops)
930 * The check (unnecessarily) ignores LRU pages being isolated and
931 * walked by the page reclaim code, however that's not a big loss.
936 action_result(pfn, "non LRU", IGNORED);
942 * Lock the page and wait for writeback to finish.
943 * It's very difficult to mess with pages currently under IO
944 * and in many cases impossible, so we just avoid it here.
949 * unpoison always clear PG_hwpoison inside page lock
951 if (!PageHWPoison(p)) {
952 printk(KERN_ERR "MCE %#lx: just unpoisoned\n", pfn);
956 if (hwpoison_filter(p)) {
957 if (TestClearPageHWPoison(p))
958 atomic_long_dec(&mce_bad_pages);
964 wait_on_page_writeback(p);
967 * Now take care of user space mappings.
968 * Abort on fail: __remove_from_page_cache() assumes unmapped page.
970 if (hwpoison_user_mappings(p, pfn, trapno) != SWAP_SUCCESS) {
971 printk(KERN_ERR "MCE %#lx: cannot unmap page, give up\n", pfn);
977 * Torn down by someone else?
979 if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) {
980 action_result(pfn, "already truncated LRU", IGNORED);
986 for (ps = error_states;; ps++) {
987 if ((p->flags & ps->mask) == ps->res) {
988 res = page_action(ps, p, pfn);
996 EXPORT_SYMBOL_GPL(__memory_failure);
999 * memory_failure - Handle memory failure of a page.
1000 * @pfn: Page Number of the corrupted page
1001 * @trapno: Trap number reported in the signal to user space.
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 void memory_failure(unsigned long pfn, int trapno)
1017 __memory_failure(pfn, trapno, 0);
1021 * unpoison_memory - Unpoison a previously poisoned page
1022 * @pfn: Page number of the to be unpoisoned page
1024 * Software-unpoison a page that has been poisoned by
1025 * memory_failure() earlier.
1027 * This is only done on the software-level, so it only works
1028 * for linux injected failures, not real hardware failures
1030 * Returns 0 for success, otherwise -errno.
1032 int unpoison_memory(unsigned long pfn)
1038 if (!pfn_valid(pfn))
1041 p = pfn_to_page(pfn);
1042 page = compound_head(p);
1044 if (!PageHWPoison(p)) {
1045 pr_debug("MCE: Page was already unpoisoned %#lx\n", pfn);
1049 if (!get_page_unless_zero(page)) {
1050 if (TestClearPageHWPoison(p))
1051 atomic_long_dec(&mce_bad_pages);
1052 pr_debug("MCE: Software-unpoisoned free page %#lx\n", pfn);
1056 lock_page_nosync(page);
1058 * This test is racy because PG_hwpoison is set outside of page lock.
1059 * That's acceptable because that won't trigger kernel panic. Instead,
1060 * the PG_hwpoison page will be caught and isolated on the entrance to
1061 * the free buddy page pool.
1063 if (TestClearPageHWPoison(p)) {
1064 pr_debug("MCE: Software-unpoisoned page %#lx\n", pfn);
1065 atomic_long_dec(&mce_bad_pages);
1076 EXPORT_SYMBOL(unpoison_memory);