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/sched.h>
38 #include <linux/ksm.h>
39 #include <linux/rmap.h>
40 #include <linux/pagemap.h>
41 #include <linux/swap.h>
42 #include <linux/backing-dev.h>
45 int sysctl_memory_failure_early_kill __read_mostly = 0;
47 int sysctl_memory_failure_recovery __read_mostly = 1;
49 atomic_long_t mce_bad_pages __read_mostly = ATOMIC_LONG_INIT(0);
51 u32 hwpoison_filter_dev_major = ~0U;
52 u32 hwpoison_filter_dev_minor = ~0U;
53 EXPORT_SYMBOL_GPL(hwpoison_filter_dev_major);
54 EXPORT_SYMBOL_GPL(hwpoison_filter_dev_minor);
56 static int hwpoison_filter_dev(struct page *p)
58 struct address_space *mapping;
61 if (hwpoison_filter_dev_major == ~0U &&
62 hwpoison_filter_dev_minor == ~0U)
66 * page_mapping() does not accept slab page
71 mapping = page_mapping(p);
72 if (mapping == NULL || mapping->host == NULL)
75 dev = mapping->host->i_sb->s_dev;
76 if (hwpoison_filter_dev_major != ~0U &&
77 hwpoison_filter_dev_major != MAJOR(dev))
79 if (hwpoison_filter_dev_minor != ~0U &&
80 hwpoison_filter_dev_minor != MINOR(dev))
86 int hwpoison_filter(struct page *p)
88 if (hwpoison_filter_dev(p))
93 EXPORT_SYMBOL_GPL(hwpoison_filter);
96 * Send all the processes who have the page mapped an ``action optional''
99 static int kill_proc_ao(struct task_struct *t, unsigned long addr, int trapno,
106 "MCE %#lx: Killing %s:%d early due to hardware memory corruption\n",
107 pfn, t->comm, t->pid);
108 si.si_signo = SIGBUS;
110 si.si_code = BUS_MCEERR_AO;
111 si.si_addr = (void *)addr;
112 #ifdef __ARCH_SI_TRAPNO
113 si.si_trapno = trapno;
115 si.si_addr_lsb = PAGE_SHIFT;
117 * Don't use force here, it's convenient if the signal
118 * can be temporarily blocked.
119 * This could cause a loop when the user sets SIGBUS
120 * to SIG_IGN, but hopefully noone will do that?
122 ret = send_sig_info(SIGBUS, &si, t); /* synchronous? */
124 printk(KERN_INFO "MCE: Error sending signal to %s:%d: %d\n",
125 t->comm, t->pid, ret);
130 * When a unknown page type is encountered drain as many buffers as possible
131 * in the hope to turn the page into a LRU or free page, which we can handle.
133 void shake_page(struct page *p)
140 if (PageLRU(p) || is_free_buddy_page(p))
144 * Could call shrink_slab here (which would also
145 * shrink other caches). Unfortunately that might
146 * also access the corrupted page, which could be fatal.
149 EXPORT_SYMBOL_GPL(shake_page);
152 * Kill all processes that have a poisoned page mapped and then isolate
156 * Find all processes having the page mapped and kill them.
157 * But we keep a page reference around so that the page is not
158 * actually freed yet.
159 * Then stash the page away
161 * There's no convenient way to get back to mapped processes
162 * from the VMAs. So do a brute-force search over all
165 * Remember that machine checks are not common (or rather
166 * if they are common you have other problems), so this shouldn't
167 * be a performance issue.
169 * Also there are some races possible while we get from the
170 * error detection to actually handle it.
175 struct task_struct *tsk;
177 unsigned addr_valid:1;
181 * Failure handling: if we can't find or can't kill a process there's
182 * not much we can do. We just print a message and ignore otherwise.
186 * Schedule a process for later kill.
187 * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
188 * TBD would GFP_NOIO be enough?
190 static void add_to_kill(struct task_struct *tsk, struct page *p,
191 struct vm_area_struct *vma,
192 struct list_head *to_kill,
193 struct to_kill **tkc)
201 tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
204 "MCE: Out of memory while machine check handling\n");
208 tk->addr = page_address_in_vma(p, vma);
212 * In theory we don't have to kill when the page was
213 * munmaped. But it could be also a mremap. Since that's
214 * likely very rare kill anyways just out of paranoia, but use
215 * a SIGKILL because the error is not contained anymore.
217 if (tk->addr == -EFAULT) {
218 pr_debug("MCE: Unable to find user space address %lx in %s\n",
219 page_to_pfn(p), tsk->comm);
222 get_task_struct(tsk);
224 list_add_tail(&tk->nd, to_kill);
228 * Kill the processes that have been collected earlier.
230 * Only do anything when DOIT is set, otherwise just free the list
231 * (this is used for clean pages which do not need killing)
232 * Also when FAIL is set do a force kill because something went
235 static void kill_procs_ao(struct list_head *to_kill, int doit, int trapno,
236 int fail, unsigned long pfn)
238 struct to_kill *tk, *next;
240 list_for_each_entry_safe (tk, next, to_kill, nd) {
243 * In case something went wrong with munmapping
244 * make sure the process doesn't catch the
245 * signal and then access the memory. Just kill it.
246 * the signal handlers
248 if (fail || tk->addr_valid == 0) {
250 "MCE %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n",
251 pfn, tk->tsk->comm, tk->tsk->pid);
252 force_sig(SIGKILL, tk->tsk);
256 * In theory the process could have mapped
257 * something else on the address in-between. We could
258 * check for that, but we need to tell the
261 else if (kill_proc_ao(tk->tsk, tk->addr, trapno,
264 "MCE %#lx: Cannot send advisory machine check signal to %s:%d\n",
265 pfn, tk->tsk->comm, tk->tsk->pid);
267 put_task_struct(tk->tsk);
272 static int task_early_kill(struct task_struct *tsk)
276 if (tsk->flags & PF_MCE_PROCESS)
277 return !!(tsk->flags & PF_MCE_EARLY);
278 return sysctl_memory_failure_early_kill;
282 * Collect processes when the error hit an anonymous page.
284 static void collect_procs_anon(struct page *page, struct list_head *to_kill,
285 struct to_kill **tkc)
287 struct vm_area_struct *vma;
288 struct task_struct *tsk;
291 read_lock(&tasklist_lock);
292 av = page_lock_anon_vma(page);
293 if (av == NULL) /* Not actually mapped anymore */
295 for_each_process (tsk) {
296 if (!task_early_kill(tsk))
298 list_for_each_entry (vma, &av->head, anon_vma_node) {
299 if (!page_mapped_in_vma(page, vma))
301 if (vma->vm_mm == tsk->mm)
302 add_to_kill(tsk, page, vma, to_kill, tkc);
305 page_unlock_anon_vma(av);
307 read_unlock(&tasklist_lock);
311 * Collect processes when the error hit a file mapped page.
313 static void collect_procs_file(struct page *page, struct list_head *to_kill,
314 struct to_kill **tkc)
316 struct vm_area_struct *vma;
317 struct task_struct *tsk;
318 struct prio_tree_iter iter;
319 struct address_space *mapping = page->mapping;
322 * A note on the locking order between the two locks.
323 * We don't rely on this particular order.
324 * If you have some other code that needs a different order
325 * feel free to switch them around. Or add a reverse link
326 * from mm_struct to task_struct, then this could be all
327 * done without taking tasklist_lock and looping over all tasks.
330 read_lock(&tasklist_lock);
331 spin_lock(&mapping->i_mmap_lock);
332 for_each_process(tsk) {
333 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
335 if (!task_early_kill(tsk))
338 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff,
341 * Send early kill signal to tasks where a vma covers
342 * the page but the corrupted page is not necessarily
343 * mapped it in its pte.
344 * Assume applications who requested early kill want
345 * to be informed of all such data corruptions.
347 if (vma->vm_mm == tsk->mm)
348 add_to_kill(tsk, page, vma, to_kill, tkc);
351 spin_unlock(&mapping->i_mmap_lock);
352 read_unlock(&tasklist_lock);
356 * Collect the processes who have the corrupted page mapped to kill.
357 * This is done in two steps for locking reasons.
358 * First preallocate one tokill structure outside the spin locks,
359 * so that we can kill at least one process reasonably reliable.
361 static void collect_procs(struct page *page, struct list_head *tokill)
368 tk = kmalloc(sizeof(struct to_kill), GFP_NOIO);
372 collect_procs_anon(page, tokill, &tk);
374 collect_procs_file(page, tokill, &tk);
379 * Error handlers for various types of pages.
383 IGNORED, /* Error: cannot be handled */
384 FAILED, /* Error: handling failed */
385 DELAYED, /* Will be handled later */
386 RECOVERED, /* Successfully recovered */
389 static const char *action_name[] = {
390 [IGNORED] = "Ignored",
392 [DELAYED] = "Delayed",
393 [RECOVERED] = "Recovered",
397 * XXX: It is possible that a page is isolated from LRU cache,
398 * and then kept in swap cache or failed to remove from page cache.
399 * The page count will stop it from being freed by unpoison.
400 * Stress tests should be aware of this memory leak problem.
402 static int delete_from_lru_cache(struct page *p)
404 if (!isolate_lru_page(p)) {
406 * Clear sensible page flags, so that the buddy system won't
407 * complain when the page is unpoison-and-freed.
410 ClearPageUnevictable(p);
412 * drop the page count elevated by isolate_lru_page()
414 page_cache_release(p);
421 * Error hit kernel page.
422 * Do nothing, try to be lucky and not touch this instead. For a few cases we
423 * could be more sophisticated.
425 static int me_kernel(struct page *p, unsigned long pfn)
431 * Page in unknown state. Do nothing.
433 static int me_unknown(struct page *p, unsigned long pfn)
435 printk(KERN_ERR "MCE %#lx: Unknown page state\n", pfn);
440 * Clean (or cleaned) page cache page.
442 static int me_pagecache_clean(struct page *p, unsigned long pfn)
446 struct address_space *mapping;
448 delete_from_lru_cache(p);
451 * For anonymous pages we're done the only reference left
452 * should be the one m_f() holds.
458 * Now truncate the page in the page cache. This is really
459 * more like a "temporary hole punch"
460 * Don't do this for block devices when someone else
461 * has a reference, because it could be file system metadata
462 * and that's not safe to truncate.
464 mapping = page_mapping(p);
467 * Page has been teared down in the meanwhile
473 * Truncation is a bit tricky. Enable it per file system for now.
475 * Open: to take i_mutex or not for this? Right now we don't.
477 if (mapping->a_ops->error_remove_page) {
478 err = mapping->a_ops->error_remove_page(mapping, p);
480 printk(KERN_INFO "MCE %#lx: Failed to punch page: %d\n",
482 } else if (page_has_private(p) &&
483 !try_to_release_page(p, GFP_NOIO)) {
484 pr_debug("MCE %#lx: failed to release buffers\n", pfn);
490 * If the file system doesn't support it just invalidate
491 * This fails on dirty or anything with private pages
493 if (invalidate_inode_page(p))
496 printk(KERN_INFO "MCE %#lx: Failed to invalidate\n",
503 * Dirty cache page page
504 * Issues: when the error hit a hole page the error is not properly
507 static int me_pagecache_dirty(struct page *p, unsigned long pfn)
509 struct address_space *mapping = page_mapping(p);
512 /* TBD: print more information about the file. */
515 * IO error will be reported by write(), fsync(), etc.
516 * who check the mapping.
517 * This way the application knows that something went
518 * wrong with its dirty file data.
520 * There's one open issue:
522 * The EIO will be only reported on the next IO
523 * operation and then cleared through the IO map.
524 * Normally Linux has two mechanisms to pass IO error
525 * first through the AS_EIO flag in the address space
526 * and then through the PageError flag in the page.
527 * Since we drop pages on memory failure handling the
528 * only mechanism open to use is through AS_AIO.
530 * This has the disadvantage that it gets cleared on
531 * the first operation that returns an error, while
532 * the PageError bit is more sticky and only cleared
533 * when the page is reread or dropped. If an
534 * application assumes it will always get error on
535 * fsync, but does other operations on the fd before
536 * and the page is dropped inbetween then the error
537 * will not be properly reported.
539 * This can already happen even without hwpoisoned
540 * pages: first on metadata IO errors (which only
541 * report through AS_EIO) or when the page is dropped
544 * So right now we assume that the application DTRT on
545 * the first EIO, but we're not worse than other parts
548 mapping_set_error(mapping, EIO);
551 return me_pagecache_clean(p, pfn);
555 * Clean and dirty swap cache.
557 * Dirty swap cache page is tricky to handle. The page could live both in page
558 * cache and swap cache(ie. page is freshly swapped in). So it could be
559 * referenced concurrently by 2 types of PTEs:
560 * normal PTEs and swap PTEs. We try to handle them consistently by calling
561 * try_to_unmap(TTU_IGNORE_HWPOISON) to convert the normal PTEs to swap PTEs,
563 * - clear dirty bit to prevent IO
565 * - but keep in the swap cache, so that when we return to it on
566 * a later page fault, we know the application is accessing
567 * corrupted data and shall be killed (we installed simple
568 * interception code in do_swap_page to catch it).
570 * Clean swap cache pages can be directly isolated. A later page fault will
571 * bring in the known good data from disk.
573 static int me_swapcache_dirty(struct page *p, unsigned long pfn)
576 /* Trigger EIO in shmem: */
577 ClearPageUptodate(p);
579 if (!delete_from_lru_cache(p))
585 static int me_swapcache_clean(struct page *p, unsigned long pfn)
587 delete_from_swap_cache(p);
589 if (!delete_from_lru_cache(p))
596 * Huge pages. Needs work.
598 * No rmap support so we cannot find the original mapper. In theory could walk
599 * all MMs and look for the mappings, but that would be non atomic and racy.
600 * Need rmap for hugepages for this. Alternatively we could employ a heuristic,
601 * like just walking the current process and hoping it has it mapped (that
602 * should be usually true for the common "shared database cache" case)
603 * Should handle free huge pages and dequeue them too, but this needs to
604 * handle huge page accounting correctly.
606 static int me_huge_page(struct page *p, unsigned long pfn)
612 * Various page states we can handle.
614 * A page state is defined by its current page->flags bits.
615 * The table matches them in order and calls the right handler.
617 * This is quite tricky because we can access page at any time
618 * in its live cycle, so all accesses have to be extremly careful.
620 * This is not complete. More states could be added.
621 * For any missing state don't attempt recovery.
624 #define dirty (1UL << PG_dirty)
625 #define sc (1UL << PG_swapcache)
626 #define unevict (1UL << PG_unevictable)
627 #define mlock (1UL << PG_mlocked)
628 #define writeback (1UL << PG_writeback)
629 #define lru (1UL << PG_lru)
630 #define swapbacked (1UL << PG_swapbacked)
631 #define head (1UL << PG_head)
632 #define tail (1UL << PG_tail)
633 #define compound (1UL << PG_compound)
634 #define slab (1UL << PG_slab)
635 #define reserved (1UL << PG_reserved)
637 static struct page_state {
641 int (*action)(struct page *p, unsigned long pfn);
643 { reserved, reserved, "reserved kernel", me_kernel },
645 * free pages are specially detected outside this table:
646 * PG_buddy pages only make a small fraction of all free pages.
650 * Could in theory check if slab page is free or if we can drop
651 * currently unused objects without touching them. But just
652 * treat it as standard kernel for now.
654 { slab, slab, "kernel slab", me_kernel },
656 #ifdef CONFIG_PAGEFLAGS_EXTENDED
657 { head, head, "huge", me_huge_page },
658 { tail, tail, "huge", me_huge_page },
660 { compound, compound, "huge", me_huge_page },
663 { sc|dirty, sc|dirty, "swapcache", me_swapcache_dirty },
664 { sc|dirty, sc, "swapcache", me_swapcache_clean },
666 { unevict|dirty, unevict|dirty, "unevictable LRU", me_pagecache_dirty},
667 { unevict, unevict, "unevictable LRU", me_pagecache_clean},
669 { mlock|dirty, mlock|dirty, "mlocked LRU", me_pagecache_dirty },
670 { mlock, mlock, "mlocked LRU", me_pagecache_clean },
672 { lru|dirty, lru|dirty, "LRU", me_pagecache_dirty },
673 { lru|dirty, lru, "clean LRU", me_pagecache_clean },
676 * Catchall entry: must be at end.
678 { 0, 0, "unknown page state", me_unknown },
681 static void action_result(unsigned long pfn, char *msg, int result)
683 struct page *page = pfn_to_page(pfn);
685 printk(KERN_ERR "MCE %#lx: %s%s page recovery: %s\n",
687 PageDirty(page) ? "dirty " : "",
688 msg, action_name[result]);
691 static int page_action(struct page_state *ps, struct page *p,
697 result = ps->action(p, pfn);
698 action_result(pfn, ps->msg, result);
700 count = page_count(p) - 1;
701 if (ps->action == me_swapcache_dirty && result == DELAYED)
705 "MCE %#lx: %s page still referenced by %d users\n",
706 pfn, ps->msg, count);
710 /* Could do more checks here if page looks ok */
712 * Could adjust zone counters here to correct for the missing page.
715 return (result == RECOVERED || result == DELAYED) ? 0 : -EBUSY;
718 #define N_UNMAP_TRIES 5
721 * Do all that is necessary to remove user space mappings. Unmap
722 * the pages and send SIGBUS to the processes if the data was dirty.
724 static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
727 enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
728 struct address_space *mapping;
734 if (PageReserved(p) || PageSlab(p))
738 * This check implies we don't kill processes if their pages
739 * are in the swap cache early. Those are always late kills.
744 if (PageCompound(p) || PageKsm(p))
747 if (PageSwapCache(p)) {
749 "MCE %#lx: keeping poisoned page in swap cache\n", pfn);
750 ttu |= TTU_IGNORE_HWPOISON;
754 * Propagate the dirty bit from PTEs to struct page first, because we
755 * need this to decide if we should kill or just drop the page.
756 * XXX: the dirty test could be racy: set_page_dirty() may not always
757 * be called inside page lock (it's recommended but not enforced).
759 mapping = page_mapping(p);
760 if (!PageDirty(p) && mapping && mapping_cap_writeback_dirty(mapping)) {
761 if (page_mkclean(p)) {
765 ttu |= TTU_IGNORE_HWPOISON;
767 "MCE %#lx: corrupted page was clean: dropped without side effects\n",
773 * First collect all the processes that have the page
774 * mapped in dirty form. This has to be done before try_to_unmap,
775 * because ttu takes the rmap data structures down.
777 * Error handling: We ignore errors here because
778 * there's nothing that can be done.
781 collect_procs(p, &tokill);
784 * try_to_unmap can fail temporarily due to races.
785 * Try a few times (RED-PEN better strategy?)
787 for (i = 0; i < N_UNMAP_TRIES; i++) {
788 ret = try_to_unmap(p, ttu);
789 if (ret == SWAP_SUCCESS)
791 pr_debug("MCE %#lx: try_to_unmap retry needed %d\n", pfn, ret);
794 if (ret != SWAP_SUCCESS)
795 printk(KERN_ERR "MCE %#lx: failed to unmap page (mapcount=%d)\n",
796 pfn, page_mapcount(p));
799 * Now that the dirty bit has been propagated to the
800 * struct page and all unmaps done we can decide if
801 * killing is needed or not. Only kill when the page
802 * was dirty, otherwise the tokill list is merely
803 * freed. When there was a problem unmapping earlier
804 * use a more force-full uncatchable kill to prevent
805 * any accesses to the poisoned memory.
807 kill_procs_ao(&tokill, !!PageDirty(p), trapno,
808 ret != SWAP_SUCCESS, pfn);
813 int __memory_failure(unsigned long pfn, int trapno, int flags)
815 struct page_state *ps;
819 if (!sysctl_memory_failure_recovery)
820 panic("Memory failure from trap %d on page %lx", trapno, pfn);
822 if (!pfn_valid(pfn)) {
824 "MCE %#lx: memory outside kernel control\n",
829 p = pfn_to_page(pfn);
830 if (TestSetPageHWPoison(p)) {
831 printk(KERN_ERR "MCE %#lx: already hardware poisoned\n", pfn);
835 atomic_long_add(1, &mce_bad_pages);
838 * We need/can do nothing about count=0 pages.
839 * 1) it's a free page, and therefore in safe hand:
840 * prep_new_page() will be the gate keeper.
841 * 2) it's part of a non-compound high order page.
842 * Implies some kernel user: cannot stop them from
843 * R/W the page; let's pray that the page has been
844 * used and will be freed some time later.
845 * In fact it's dangerous to directly bump up page count from 0,
846 * that may make page_freeze_refs()/page_unfreeze_refs() mismatch.
848 if (!(flags & MF_COUNT_INCREASED) &&
849 !get_page_unless_zero(compound_head(p))) {
850 if (is_free_buddy_page(p)) {
851 action_result(pfn, "free buddy", DELAYED);
854 action_result(pfn, "high order kernel", IGNORED);
860 * We ignore non-LRU pages for good reasons.
861 * - PG_locked is only well defined for LRU pages and a few others
862 * - to avoid races with __set_page_locked()
863 * - to avoid races with __SetPageSlab*() (and more non-atomic ops)
864 * The check (unnecessarily) ignores LRU pages being isolated and
865 * walked by the page reclaim code, however that's not a big loss.
870 action_result(pfn, "non LRU", IGNORED);
876 * Lock the page and wait for writeback to finish.
877 * It's very difficult to mess with pages currently under IO
878 * and in many cases impossible, so we just avoid it here.
883 * unpoison always clear PG_hwpoison inside page lock
885 if (!PageHWPoison(p)) {
886 printk(KERN_ERR "MCE %#lx: just unpoisoned\n", pfn);
890 if (hwpoison_filter(p)) {
891 if (TestClearPageHWPoison(p))
892 atomic_long_dec(&mce_bad_pages);
898 wait_on_page_writeback(p);
901 * Now take care of user space mappings.
902 * Abort on fail: __remove_from_page_cache() assumes unmapped page.
904 if (hwpoison_user_mappings(p, pfn, trapno) != SWAP_SUCCESS) {
905 printk(KERN_ERR "MCE %#lx: cannot unmap page, give up\n", pfn);
911 * Torn down by someone else?
913 if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) {
914 action_result(pfn, "already truncated LRU", IGNORED);
920 for (ps = error_states;; ps++) {
921 if ((p->flags & ps->mask) == ps->res) {
922 res = page_action(ps, p, pfn);
930 EXPORT_SYMBOL_GPL(__memory_failure);
933 * memory_failure - Handle memory failure of a page.
934 * @pfn: Page Number of the corrupted page
935 * @trapno: Trap number reported in the signal to user space.
937 * This function is called by the low level machine check code
938 * of an architecture when it detects hardware memory corruption
939 * of a page. It tries its best to recover, which includes
940 * dropping pages, killing processes etc.
942 * The function is primarily of use for corruptions that
943 * happen outside the current execution context (e.g. when
944 * detected by a background scrubber)
946 * Must run in process context (e.g. a work queue) with interrupts
947 * enabled and no spinlocks hold.
949 void memory_failure(unsigned long pfn, int trapno)
951 __memory_failure(pfn, trapno, 0);
955 * unpoison_memory - Unpoison a previously poisoned page
956 * @pfn: Page number of the to be unpoisoned page
958 * Software-unpoison a page that has been poisoned by
959 * memory_failure() earlier.
961 * This is only done on the software-level, so it only works
962 * for linux injected failures, not real hardware failures
964 * Returns 0 for success, otherwise -errno.
966 int unpoison_memory(unsigned long pfn)
975 p = pfn_to_page(pfn);
976 page = compound_head(p);
978 if (!PageHWPoison(p)) {
979 pr_debug("MCE: Page was already unpoisoned %#lx\n", pfn);
983 if (!get_page_unless_zero(page)) {
984 if (TestClearPageHWPoison(p))
985 atomic_long_dec(&mce_bad_pages);
986 pr_debug("MCE: Software-unpoisoned free page %#lx\n", pfn);
990 lock_page_nosync(page);
992 * This test is racy because PG_hwpoison is set outside of page lock.
993 * That's acceptable because that won't trigger kernel panic. Instead,
994 * the PG_hwpoison page will be caught and isolated on the entrance to
995 * the free buddy page pool.
997 if (TestClearPageHWPoison(p)) {
998 pr_debug("MCE: Software-unpoisoned page %#lx\n", pfn);
999 atomic_long_dec(&mce_bad_pages);
1010 EXPORT_SYMBOL(unpoison_memory);