Root/mm/memory-failure.c

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 2bit ECC memory or cache
11 * failure.
12 *
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.
20 *
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.
25 */
26
27/*
28 * Notebook:
29 * - hugetlb needs more code
30 * - kcore/oldmem/vmcore/mem/kmem check for hwpoison pages
31 * - pass bad pages to kdump next kernel
32 */
33#define DEBUG 1 /* remove me in 2.6.34 */
34#include <linux/kernel.h>
35#include <linux/mm.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>
44#include <linux/migrate.h>
45#include <linux/page-isolation.h>
46#include <linux/suspend.h>
47#include <linux/slab.h>
48#include <linux/swapops.h>
49#include <linux/hugetlb.h>
50#include "internal.h"
51
52int sysctl_memory_failure_early_kill __read_mostly = 0;
53
54int sysctl_memory_failure_recovery __read_mostly = 1;
55
56atomic_long_t mce_bad_pages __read_mostly = ATOMIC_LONG_INIT(0);
57
58#if defined(CONFIG_HWPOISON_INJECT) || defined(CONFIG_HWPOISON_INJECT_MODULE)
59
60u32 hwpoison_filter_enable = 0;
61u32 hwpoison_filter_dev_major = ~0U;
62u32 hwpoison_filter_dev_minor = ~0U;
63u64 hwpoison_filter_flags_mask;
64u64 hwpoison_filter_flags_value;
65EXPORT_SYMBOL_GPL(hwpoison_filter_enable);
66EXPORT_SYMBOL_GPL(hwpoison_filter_dev_major);
67EXPORT_SYMBOL_GPL(hwpoison_filter_dev_minor);
68EXPORT_SYMBOL_GPL(hwpoison_filter_flags_mask);
69EXPORT_SYMBOL_GPL(hwpoison_filter_flags_value);
70
71static int hwpoison_filter_dev(struct page *p)
72{
73    struct address_space *mapping;
74    dev_t dev;
75
76    if (hwpoison_filter_dev_major == ~0U &&
77        hwpoison_filter_dev_minor == ~0U)
78        return 0;
79
80    /*
81     * page_mapping() does not accept slab page
82     */
83    if (PageSlab(p))
84        return -EINVAL;
85
86    mapping = page_mapping(p);
87    if (mapping == NULL || mapping->host == NULL)
88        return -EINVAL;
89
90    dev = mapping->host->i_sb->s_dev;
91    if (hwpoison_filter_dev_major != ~0U &&
92        hwpoison_filter_dev_major != MAJOR(dev))
93        return -EINVAL;
94    if (hwpoison_filter_dev_minor != ~0U &&
95        hwpoison_filter_dev_minor != MINOR(dev))
96        return -EINVAL;
97
98    return 0;
99}
100
101static int hwpoison_filter_flags(struct page *p)
102{
103    if (!hwpoison_filter_flags_mask)
104        return 0;
105
106    if ((stable_page_flags(p) & hwpoison_filter_flags_mask) ==
107                    hwpoison_filter_flags_value)
108        return 0;
109    else
110        return -EINVAL;
111}
112
113/*
114 * This allows stress tests to limit test scope to a collection of tasks
115 * by putting them under some memcg. This prevents killing unrelated/important
116 * processes such as /sbin/init. Note that the target task may share clean
117 * pages with init (eg. libc text), which is harmless. If the target task
118 * share _dirty_ pages with another task B, the test scheme must make sure B
119 * is also included in the memcg. At last, due to race conditions this filter
120 * can only guarantee that the page either belongs to the memcg tasks, or is
121 * a freed page.
122 */
123#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
124u64 hwpoison_filter_memcg;
125EXPORT_SYMBOL_GPL(hwpoison_filter_memcg);
126static int hwpoison_filter_task(struct page *p)
127{
128    struct mem_cgroup *mem;
129    struct cgroup_subsys_state *css;
130    unsigned long ino;
131
132    if (!hwpoison_filter_memcg)
133        return 0;
134
135    mem = try_get_mem_cgroup_from_page(p);
136    if (!mem)
137        return -EINVAL;
138
139    css = mem_cgroup_css(mem);
140    /* root_mem_cgroup has NULL dentries */
141    if (!css->cgroup->dentry)
142        return -EINVAL;
143
144    ino = css->cgroup->dentry->d_inode->i_ino;
145    css_put(css);
146
147    if (ino != hwpoison_filter_memcg)
148        return -EINVAL;
149
150    return 0;
151}
152#else
153static int hwpoison_filter_task(struct page *p) { return 0; }
154#endif
155
156int hwpoison_filter(struct page *p)
157{
158    if (!hwpoison_filter_enable)
159        return 0;
160
161    if (hwpoison_filter_dev(p))
162        return -EINVAL;
163
164    if (hwpoison_filter_flags(p))
165        return -EINVAL;
166
167    if (hwpoison_filter_task(p))
168        return -EINVAL;
169
170    return 0;
171}
172#else
173int hwpoison_filter(struct page *p)
174{
175    return 0;
176}
177#endif
178
179EXPORT_SYMBOL_GPL(hwpoison_filter);
180
181/*
182 * Send all the processes who have the page mapped an ``action optional''
183 * signal.
184 */
185static int kill_proc_ao(struct task_struct *t, unsigned long addr, int trapno,
186            unsigned long pfn, struct page *page)
187{
188    struct siginfo si;
189    int ret;
190
191    printk(KERN_ERR
192        "MCE %#lx: Killing %s:%d early due to hardware memory corruption\n",
193        pfn, t->comm, t->pid);
194    si.si_signo = SIGBUS;
195    si.si_errno = 0;
196    si.si_code = BUS_MCEERR_AO;
197    si.si_addr = (void *)addr;
198#ifdef __ARCH_SI_TRAPNO
199    si.si_trapno = trapno;
200#endif
201    si.si_addr_lsb = compound_order(compound_head(page)) + PAGE_SHIFT;
202    /*
203     * Don't use force here, it's convenient if the signal
204     * can be temporarily blocked.
205     * This could cause a loop when the user sets SIGBUS
206     * to SIG_IGN, but hopefully noone will do that?
207     */
208    ret = send_sig_info(SIGBUS, &si, t); /* synchronous? */
209    if (ret < 0)
210        printk(KERN_INFO "MCE: Error sending signal to %s:%d: %d\n",
211               t->comm, t->pid, ret);
212    return ret;
213}
214
215/*
216 * When a unknown page type is encountered drain as many buffers as possible
217 * in the hope to turn the page into a LRU or free page, which we can handle.
218 */
219void shake_page(struct page *p, int access)
220{
221    if (!PageSlab(p)) {
222        lru_add_drain_all();
223        if (PageLRU(p))
224            return;
225        drain_all_pages();
226        if (PageLRU(p) || is_free_buddy_page(p))
227            return;
228    }
229
230    /*
231     * Only all shrink_slab here (which would also
232     * shrink other caches) if access is not potentially fatal.
233     */
234    if (access) {
235        int nr;
236        do {
237            nr = shrink_slab(1000, GFP_KERNEL, 1000);
238            if (page_count(p) == 1)
239                break;
240        } while (nr > 10);
241    }
242}
243EXPORT_SYMBOL_GPL(shake_page);
244
245/*
246 * Kill all processes that have a poisoned page mapped and then isolate
247 * the page.
248 *
249 * General strategy:
250 * Find all processes having the page mapped and kill them.
251 * But we keep a page reference around so that the page is not
252 * actually freed yet.
253 * Then stash the page away
254 *
255 * There's no convenient way to get back to mapped processes
256 * from the VMAs. So do a brute-force search over all
257 * running processes.
258 *
259 * Remember that machine checks are not common (or rather
260 * if they are common you have other problems), so this shouldn't
261 * be a performance issue.
262 *
263 * Also there are some races possible while we get from the
264 * error detection to actually handle it.
265 */
266
267struct to_kill {
268    struct list_head nd;
269    struct task_struct *tsk;
270    unsigned long addr;
271    unsigned addr_valid:1;
272};
273
274/*
275 * Failure handling: if we can't find or can't kill a process there's
276 * not much we can do. We just print a message and ignore otherwise.
277 */
278
279/*
280 * Schedule a process for later kill.
281 * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
282 * TBD would GFP_NOIO be enough?
283 */
284static void add_to_kill(struct task_struct *tsk, struct page *p,
285               struct vm_area_struct *vma,
286               struct list_head *to_kill,
287               struct to_kill **tkc)
288{
289    struct to_kill *tk;
290
291    if (*tkc) {
292        tk = *tkc;
293        *tkc = NULL;
294    } else {
295        tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
296        if (!tk) {
297            printk(KERN_ERR
298        "MCE: Out of memory while machine check handling\n");
299            return;
300        }
301    }
302    tk->addr = page_address_in_vma(p, vma);
303    tk->addr_valid = 1;
304
305    /*
306     * In theory we don't have to kill when the page was
307     * munmaped. But it could be also a mremap. Since that's
308     * likely very rare kill anyways just out of paranoia, but use
309     * a SIGKILL because the error is not contained anymore.
310     */
311    if (tk->addr == -EFAULT) {
312        pr_debug("MCE: Unable to find user space address %lx in %s\n",
313            page_to_pfn(p), tsk->comm);
314        tk->addr_valid = 0;
315    }
316    get_task_struct(tsk);
317    tk->tsk = tsk;
318    list_add_tail(&tk->nd, to_kill);
319}
320
321/*
322 * Kill the processes that have been collected earlier.
323 *
324 * Only do anything when DOIT is set, otherwise just free the list
325 * (this is used for clean pages which do not need killing)
326 * Also when FAIL is set do a force kill because something went
327 * wrong earlier.
328 */
329static void kill_procs_ao(struct list_head *to_kill, int doit, int trapno,
330              int fail, struct page *page, unsigned long pfn)
331{
332    struct to_kill *tk, *next;
333
334    list_for_each_entry_safe (tk, next, to_kill, nd) {
335        if (doit) {
336            /*
337             * In case something went wrong with munmapping
338             * make sure the process doesn't catch the
339             * signal and then access the memory. Just kill it.
340             */
341            if (fail || tk->addr_valid == 0) {
342                printk(KERN_ERR
343        "MCE %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n",
344                    pfn, tk->tsk->comm, tk->tsk->pid);
345                force_sig(SIGKILL, tk->tsk);
346            }
347
348            /*
349             * In theory the process could have mapped
350             * something else on the address in-between. We could
351             * check for that, but we need to tell the
352             * process anyways.
353             */
354            else if (kill_proc_ao(tk->tsk, tk->addr, trapno,
355                          pfn, page) < 0)
356                printk(KERN_ERR
357        "MCE %#lx: Cannot send advisory machine check signal to %s:%d\n",
358                    pfn, tk->tsk->comm, tk->tsk->pid);
359        }
360        put_task_struct(tk->tsk);
361        kfree(tk);
362    }
363}
364
365static int task_early_kill(struct task_struct *tsk)
366{
367    if (!tsk->mm)
368        return 0;
369    if (tsk->flags & PF_MCE_PROCESS)
370        return !!(tsk->flags & PF_MCE_EARLY);
371    return sysctl_memory_failure_early_kill;
372}
373
374/*
375 * Collect processes when the error hit an anonymous page.
376 */
377static void collect_procs_anon(struct page *page, struct list_head *to_kill,
378                  struct to_kill **tkc)
379{
380    struct vm_area_struct *vma;
381    struct task_struct *tsk;
382    struct anon_vma *av;
383
384    read_lock(&tasklist_lock);
385    av = page_lock_anon_vma(page);
386    if (av == NULL) /* Not actually mapped anymore */
387        goto out;
388    for_each_process (tsk) {
389        struct anon_vma_chain *vmac;
390
391        if (!task_early_kill(tsk))
392            continue;
393        list_for_each_entry(vmac, &av->head, same_anon_vma) {
394            vma = vmac->vma;
395            if (!page_mapped_in_vma(page, vma))
396                continue;
397            if (vma->vm_mm == tsk->mm)
398                add_to_kill(tsk, page, vma, to_kill, tkc);
399        }
400    }
401    page_unlock_anon_vma(av);
402out:
403    read_unlock(&tasklist_lock);
404}
405
406/*
407 * Collect processes when the error hit a file mapped page.
408 */
409static void collect_procs_file(struct page *page, struct list_head *to_kill,
410                  struct to_kill **tkc)
411{
412    struct vm_area_struct *vma;
413    struct task_struct *tsk;
414    struct prio_tree_iter iter;
415    struct address_space *mapping = page->mapping;
416
417    /*
418     * A note on the locking order between the two locks.
419     * We don't rely on this particular order.
420     * If you have some other code that needs a different order
421     * feel free to switch them around. Or add a reverse link
422     * from mm_struct to task_struct, then this could be all
423     * done without taking tasklist_lock and looping over all tasks.
424     */
425
426    read_lock(&tasklist_lock);
427    spin_lock(&mapping->i_mmap_lock);
428    for_each_process(tsk) {
429        pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
430
431        if (!task_early_kill(tsk))
432            continue;
433
434        vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff,
435                      pgoff) {
436            /*
437             * Send early kill signal to tasks where a vma covers
438             * the page but the corrupted page is not necessarily
439             * mapped it in its pte.
440             * Assume applications who requested early kill want
441             * to be informed of all such data corruptions.
442             */
443            if (vma->vm_mm == tsk->mm)
444                add_to_kill(tsk, page, vma, to_kill, tkc);
445        }
446    }
447    spin_unlock(&mapping->i_mmap_lock);
448    read_unlock(&tasklist_lock);
449}
450
451/*
452 * Collect the processes who have the corrupted page mapped to kill.
453 * This is done in two steps for locking reasons.
454 * First preallocate one tokill structure outside the spin locks,
455 * so that we can kill at least one process reasonably reliable.
456 */
457static void collect_procs(struct page *page, struct list_head *tokill)
458{
459    struct to_kill *tk;
460
461    if (!page->mapping)
462        return;
463
464    tk = kmalloc(sizeof(struct to_kill), GFP_NOIO);
465    if (!tk)
466        return;
467    if (PageAnon(page))
468        collect_procs_anon(page, tokill, &tk);
469    else
470        collect_procs_file(page, tokill, &tk);
471    kfree(tk);
472}
473
474/*
475 * Error handlers for various types of pages.
476 */
477
478enum outcome {
479    IGNORED, /* Error: cannot be handled */
480    FAILED, /* Error: handling failed */
481    DELAYED, /* Will be handled later */
482    RECOVERED, /* Successfully recovered */
483};
484
485static const char *action_name[] = {
486    [IGNORED] = "Ignored",
487    [FAILED] = "Failed",
488    [DELAYED] = "Delayed",
489    [RECOVERED] = "Recovered",
490};
491
492/*
493 * XXX: It is possible that a page is isolated from LRU cache,
494 * and then kept in swap cache or failed to remove from page cache.
495 * The page count will stop it from being freed by unpoison.
496 * Stress tests should be aware of this memory leak problem.
497 */
498static int delete_from_lru_cache(struct page *p)
499{
500    if (!isolate_lru_page(p)) {
501        /*
502         * Clear sensible page flags, so that the buddy system won't
503         * complain when the page is unpoison-and-freed.
504         */
505        ClearPageActive(p);
506        ClearPageUnevictable(p);
507        /*
508         * drop the page count elevated by isolate_lru_page()
509         */
510        page_cache_release(p);
511        return 0;
512    }
513    return -EIO;
514}
515
516/*
517 * Error hit kernel page.
518 * Do nothing, try to be lucky and not touch this instead. For a few cases we
519 * could be more sophisticated.
520 */
521static int me_kernel(struct page *p, unsigned long pfn)
522{
523    return IGNORED;
524}
525
526/*
527 * Page in unknown state. Do nothing.
528 */
529static int me_unknown(struct page *p, unsigned long pfn)
530{
531    printk(KERN_ERR "MCE %#lx: Unknown page state\n", pfn);
532    return FAILED;
533}
534
535/*
536 * Clean (or cleaned) page cache page.
537 */
538static int me_pagecache_clean(struct page *p, unsigned long pfn)
539{
540    int err;
541    int ret = FAILED;
542    struct address_space *mapping;
543
544    delete_from_lru_cache(p);
545
546    /*
547     * For anonymous pages we're done the only reference left
548     * should be the one m_f() holds.
549     */
550    if (PageAnon(p))
551        return RECOVERED;
552
553    /*
554     * Now truncate the page in the page cache. This is really
555     * more like a "temporary hole punch"
556     * Don't do this for block devices when someone else
557     * has a reference, because it could be file system metadata
558     * and that's not safe to truncate.
559     */
560    mapping = page_mapping(p);
561    if (!mapping) {
562        /*
563         * Page has been teared down in the meanwhile
564         */
565        return FAILED;
566    }
567
568    /*
569     * Truncation is a bit tricky. Enable it per file system for now.
570     *
571     * Open: to take i_mutex or not for this? Right now we don't.
572     */
573    if (mapping->a_ops->error_remove_page) {
574        err = mapping->a_ops->error_remove_page(mapping, p);
575        if (err != 0) {
576            printk(KERN_INFO "MCE %#lx: Failed to punch page: %d\n",
577                    pfn, err);
578        } else if (page_has_private(p) &&
579                !try_to_release_page(p, GFP_NOIO)) {
580            pr_debug("MCE %#lx: failed to release buffers\n", pfn);
581        } else {
582            ret = RECOVERED;
583        }
584    } else {
585        /*
586         * If the file system doesn't support it just invalidate
587         * This fails on dirty or anything with private pages
588         */
589        if (invalidate_inode_page(p))
590            ret = RECOVERED;
591        else
592            printk(KERN_INFO "MCE %#lx: Failed to invalidate\n",
593                pfn);
594    }
595    return ret;
596}
597
598/*
599 * Dirty cache page page
600 * Issues: when the error hit a hole page the error is not properly
601 * propagated.
602 */
603static int me_pagecache_dirty(struct page *p, unsigned long pfn)
604{
605    struct address_space *mapping = page_mapping(p);
606
607    SetPageError(p);
608    /* TBD: print more information about the file. */
609    if (mapping) {
610        /*
611         * IO error will be reported by write(), fsync(), etc.
612         * who check the mapping.
613         * This way the application knows that something went
614         * wrong with its dirty file data.
615         *
616         * There's one open issue:
617         *
618         * The EIO will be only reported on the next IO
619         * operation and then cleared through the IO map.
620         * Normally Linux has two mechanisms to pass IO error
621         * first through the AS_EIO flag in the address space
622         * and then through the PageError flag in the page.
623         * Since we drop pages on memory failure handling the
624         * only mechanism open to use is through AS_AIO.
625         *
626         * This has the disadvantage that it gets cleared on
627         * the first operation that returns an error, while
628         * the PageError bit is more sticky and only cleared
629         * when the page is reread or dropped. If an
630         * application assumes it will always get error on
631         * fsync, but does other operations on the fd before
632         * and the page is dropped inbetween then the error
633         * will not be properly reported.
634         *
635         * This can already happen even without hwpoisoned
636         * pages: first on metadata IO errors (which only
637         * report through AS_EIO) or when the page is dropped
638         * at the wrong time.
639         *
640         * So right now we assume that the application DTRT on
641         * the first EIO, but we're not worse than other parts
642         * of the kernel.
643         */
644        mapping_set_error(mapping, EIO);
645    }
646
647    return me_pagecache_clean(p, pfn);
648}
649
650/*
651 * Clean and dirty swap cache.
652 *
653 * Dirty swap cache page is tricky to handle. The page could live both in page
654 * cache and swap cache(ie. page is freshly swapped in). So it could be
655 * referenced concurrently by 2 types of PTEs:
656 * normal PTEs and swap PTEs. We try to handle them consistently by calling
657 * try_to_unmap(TTU_IGNORE_HWPOISON) to convert the normal PTEs to swap PTEs,
658 * and then
659 * - clear dirty bit to prevent IO
660 * - remove from LRU
661 * - but keep in the swap cache, so that when we return to it on
662 * a later page fault, we know the application is accessing
663 * corrupted data and shall be killed (we installed simple
664 * interception code in do_swap_page to catch it).
665 *
666 * Clean swap cache pages can be directly isolated. A later page fault will
667 * bring in the known good data from disk.
668 */
669static int me_swapcache_dirty(struct page *p, unsigned long pfn)
670{
671    ClearPageDirty(p);
672    /* Trigger EIO in shmem: */
673    ClearPageUptodate(p);
674
675    if (!delete_from_lru_cache(p))
676        return DELAYED;
677    else
678        return FAILED;
679}
680
681static int me_swapcache_clean(struct page *p, unsigned long pfn)
682{
683    delete_from_swap_cache(p);
684
685    if (!delete_from_lru_cache(p))
686        return RECOVERED;
687    else
688        return FAILED;
689}
690
691/*
692 * Huge pages. Needs work.
693 * Issues:
694 * - Error on hugepage is contained in hugepage unit (not in raw page unit.)
695 * To narrow down kill region to one page, we need to break up pmd.
696 * - To support soft-offlining for hugepage, we need to support hugepage
697 * migration.
698 */
699static int me_huge_page(struct page *p, unsigned long pfn)
700{
701    struct page *hpage = compound_head(p);
702    /*
703     * We can safely recover from error on free or reserved (i.e.
704     * not in-use) hugepage by dequeuing it from freelist.
705     * To check whether a hugepage is in-use or not, we can't use
706     * page->lru because it can be used in other hugepage operations,
707     * such as __unmap_hugepage_range() and gather_surplus_pages().
708     * So instead we use page_mapping() and PageAnon().
709     * We assume that this function is called with page lock held,
710     * so there is no race between isolation and mapping/unmapping.
711     */
712    if (!(page_mapping(hpage) || PageAnon(hpage))) {
713        __isolate_hwpoisoned_huge_page(hpage);
714        return RECOVERED;
715    }
716    return DELAYED;
717}
718
719/*
720 * Various page states we can handle.
721 *
722 * A page state is defined by its current page->flags bits.
723 * The table matches them in order and calls the right handler.
724 *
725 * This is quite tricky because we can access page at any time
726 * in its live cycle, so all accesses have to be extremly careful.
727 *
728 * This is not complete. More states could be added.
729 * For any missing state don't attempt recovery.
730 */
731
732#define dirty (1UL << PG_dirty)
733#define sc (1UL << PG_swapcache)
734#define unevict (1UL << PG_unevictable)
735#define mlock (1UL << PG_mlocked)
736#define writeback (1UL << PG_writeback)
737#define lru (1UL << PG_lru)
738#define swapbacked (1UL << PG_swapbacked)
739#define head (1UL << PG_head)
740#define tail (1UL << PG_tail)
741#define compound (1UL << PG_compound)
742#define slab (1UL << PG_slab)
743#define reserved (1UL << PG_reserved)
744
745static struct page_state {
746    unsigned long mask;
747    unsigned long res;
748    char *msg;
749    int (*action)(struct page *p, unsigned long pfn);
750} error_states[] = {
751    { reserved, reserved, "reserved kernel", me_kernel },
752    /*
753     * free pages are specially detected outside this table:
754     * PG_buddy pages only make a small fraction of all free pages.
755     */
756
757    /*
758     * Could in theory check if slab page is free or if we can drop
759     * currently unused objects without touching them. But just
760     * treat it as standard kernel for now.
761     */
762    { slab, slab, "kernel slab", me_kernel },
763
764#ifdef CONFIG_PAGEFLAGS_EXTENDED
765    { head, head, "huge", me_huge_page },
766    { tail, tail, "huge", me_huge_page },
767#else
768    { compound, compound, "huge", me_huge_page },
769#endif
770
771    { sc|dirty, sc|dirty, "swapcache", me_swapcache_dirty },
772    { sc|dirty, sc, "swapcache", me_swapcache_clean },
773
774    { unevict|dirty, unevict|dirty, "unevictable LRU", me_pagecache_dirty},
775    { unevict, unevict, "unevictable LRU", me_pagecache_clean},
776
777    { mlock|dirty, mlock|dirty, "mlocked LRU", me_pagecache_dirty },
778    { mlock, mlock, "mlocked LRU", me_pagecache_clean },
779
780    { lru|dirty, lru|dirty, "LRU", me_pagecache_dirty },
781    { lru|dirty, lru, "clean LRU", me_pagecache_clean },
782
783    /*
784     * Catchall entry: must be at end.
785     */
786    { 0, 0, "unknown page state", me_unknown },
787};
788
789#undef dirty
790#undef sc
791#undef unevict
792#undef mlock
793#undef writeback
794#undef lru
795#undef swapbacked
796#undef head
797#undef tail
798#undef compound
799#undef slab
800#undef reserved
801
802static void action_result(unsigned long pfn, char *msg, int result)
803{
804    struct page *page = pfn_to_page(pfn);
805
806    printk(KERN_ERR "MCE %#lx: %s%s page recovery: %s\n",
807        pfn,
808        PageDirty(page) ? "dirty " : "",
809        msg, action_name[result]);
810}
811
812static int page_action(struct page_state *ps, struct page *p,
813            unsigned long pfn)
814{
815    int result;
816    int count;
817
818    result = ps->action(p, pfn);
819    action_result(pfn, ps->msg, result);
820
821    count = page_count(p) - 1;
822    if (ps->action == me_swapcache_dirty && result == DELAYED)
823        count--;
824    if (count != 0) {
825        printk(KERN_ERR
826               "MCE %#lx: %s page still referenced by %d users\n",
827               pfn, ps->msg, count);
828        result = FAILED;
829    }
830
831    /* Could do more checks here if page looks ok */
832    /*
833     * Could adjust zone counters here to correct for the missing page.
834     */
835
836    return (result == RECOVERED || result == DELAYED) ? 0 : -EBUSY;
837}
838
839#define N_UNMAP_TRIES 5
840
841/*
842 * Do all that is necessary to remove user space mappings. Unmap
843 * the pages and send SIGBUS to the processes if the data was dirty.
844 */
845static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
846                  int trapno)
847{
848    enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
849    struct address_space *mapping;
850    LIST_HEAD(tokill);
851    int ret;
852    int i;
853    int kill = 1;
854    struct page *hpage = compound_head(p);
855
856    if (PageReserved(p) || PageSlab(p))
857        return SWAP_SUCCESS;
858
859    /*
860     * This check implies we don't kill processes if their pages
861     * are in the swap cache early. Those are always late kills.
862     */
863    if (!page_mapped(hpage))
864        return SWAP_SUCCESS;
865
866    if (PageKsm(p))
867        return SWAP_FAIL;
868
869    if (PageSwapCache(p)) {
870        printk(KERN_ERR
871               "MCE %#lx: keeping poisoned page in swap cache\n", pfn);
872        ttu |= TTU_IGNORE_HWPOISON;
873    }
874
875    /*
876     * Propagate the dirty bit from PTEs to struct page first, because we
877     * need this to decide if we should kill or just drop the page.
878     * XXX: the dirty test could be racy: set_page_dirty() may not always
879     * be called inside page lock (it's recommended but not enforced).
880     */
881    mapping = page_mapping(hpage);
882    if (!PageDirty(hpage) && mapping &&
883        mapping_cap_writeback_dirty(mapping)) {
884        if (page_mkclean(hpage)) {
885            SetPageDirty(hpage);
886        } else {
887            kill = 0;
888            ttu |= TTU_IGNORE_HWPOISON;
889            printk(KERN_INFO
890    "MCE %#lx: corrupted page was clean: dropped without side effects\n",
891                pfn);
892        }
893    }
894
895    /*
896     * First collect all the processes that have the page
897     * mapped in dirty form. This has to be done before try_to_unmap,
898     * because ttu takes the rmap data structures down.
899     *
900     * Error handling: We ignore errors here because
901     * there's nothing that can be done.
902     */
903    if (kill)
904        collect_procs(hpage, &tokill);
905
906    /*
907     * try_to_unmap can fail temporarily due to races.
908     * Try a few times (RED-PEN better strategy?)
909     */
910    for (i = 0; i < N_UNMAP_TRIES; i++) {
911        ret = try_to_unmap(hpage, ttu);
912        if (ret == SWAP_SUCCESS)
913            break;
914        pr_debug("MCE %#lx: try_to_unmap retry needed %d\n", pfn, ret);
915    }
916
917    if (ret != SWAP_SUCCESS)
918        printk(KERN_ERR "MCE %#lx: failed to unmap page (mapcount=%d)\n",
919                pfn, page_mapcount(hpage));
920
921    /*
922     * Now that the dirty bit has been propagated to the
923     * struct page and all unmaps done we can decide if
924     * killing is needed or not. Only kill when the page
925     * was dirty, otherwise the tokill list is merely
926     * freed. When there was a problem unmapping earlier
927     * use a more force-full uncatchable kill to prevent
928     * any accesses to the poisoned memory.
929     */
930    kill_procs_ao(&tokill, !!PageDirty(hpage), trapno,
931              ret != SWAP_SUCCESS, p, pfn);
932
933    return ret;
934}
935
936static void set_page_hwpoison_huge_page(struct page *hpage)
937{
938    int i;
939    int nr_pages = 1 << compound_order(hpage);
940    for (i = 0; i < nr_pages; i++)
941        SetPageHWPoison(hpage + i);
942}
943
944static void clear_page_hwpoison_huge_page(struct page *hpage)
945{
946    int i;
947    int nr_pages = 1 << compound_order(hpage);
948    for (i = 0; i < nr_pages; i++)
949        ClearPageHWPoison(hpage + i);
950}
951
952int __memory_failure(unsigned long pfn, int trapno, int flags)
953{
954    struct page_state *ps;
955    struct page *p;
956    struct page *hpage;
957    int res;
958    unsigned int nr_pages;
959
960    if (!sysctl_memory_failure_recovery)
961        panic("Memory failure from trap %d on page %lx", trapno, pfn);
962
963    if (!pfn_valid(pfn)) {
964        printk(KERN_ERR
965               "MCE %#lx: memory outside kernel control\n",
966               pfn);
967        return -ENXIO;
968    }
969
970    p = pfn_to_page(pfn);
971    hpage = compound_head(p);
972    if (TestSetPageHWPoison(p)) {
973        printk(KERN_ERR "MCE %#lx: already hardware poisoned\n", pfn);
974        return 0;
975    }
976
977    nr_pages = 1 << compound_order(hpage);
978    atomic_long_add(nr_pages, &mce_bad_pages);
979
980    /*
981     * We need/can do nothing about count=0 pages.
982     * 1) it's a free page, and therefore in safe hand:
983     * prep_new_page() will be the gate keeper.
984     * 2) it's part of a non-compound high order page.
985     * Implies some kernel user: cannot stop them from
986     * R/W the page; let's pray that the page has been
987     * used and will be freed some time later.
988     * In fact it's dangerous to directly bump up page count from 0,
989     * that may make page_freeze_refs()/page_unfreeze_refs() mismatch.
990     */
991    if (!(flags & MF_COUNT_INCREASED) &&
992        !get_page_unless_zero(hpage)) {
993        if (is_free_buddy_page(p)) {
994            action_result(pfn, "free buddy", DELAYED);
995            return 0;
996        } else {
997            action_result(pfn, "high order kernel", IGNORED);
998            return -EBUSY;
999        }
1000    }
1001
1002    /*
1003     * We ignore non-LRU pages for good reasons.
1004     * - PG_locked is only well defined for LRU pages and a few others
1005     * - to avoid races with __set_page_locked()
1006     * - to avoid races with __SetPageSlab*() (and more non-atomic ops)
1007     * The check (unnecessarily) ignores LRU pages being isolated and
1008     * walked by the page reclaim code, however that's not a big loss.
1009     */
1010    if (!PageLRU(p) && !PageHuge(p))
1011        shake_page(p, 0);
1012    if (!PageLRU(p) && !PageHuge(p)) {
1013        /*
1014         * shake_page could have turned it free.
1015         */
1016        if (is_free_buddy_page(p)) {
1017            action_result(pfn, "free buddy, 2nd try", DELAYED);
1018            return 0;
1019        }
1020        action_result(pfn, "non LRU", IGNORED);
1021        put_page(p);
1022        return -EBUSY;
1023    }
1024
1025    /*
1026     * Lock the page and wait for writeback to finish.
1027     * It's very difficult to mess with pages currently under IO
1028     * and in many cases impossible, so we just avoid it here.
1029     */
1030    lock_page_nosync(hpage);
1031
1032    /*
1033     * unpoison always clear PG_hwpoison inside page lock
1034     */
1035    if (!PageHWPoison(p)) {
1036        printk(KERN_ERR "MCE %#lx: just unpoisoned\n", pfn);
1037        res = 0;
1038        goto out;
1039    }
1040    if (hwpoison_filter(p)) {
1041        if (TestClearPageHWPoison(p))
1042            atomic_long_sub(nr_pages, &mce_bad_pages);
1043        unlock_page(hpage);
1044        put_page(hpage);
1045        return 0;
1046    }
1047
1048    /*
1049     * For error on the tail page, we should set PG_hwpoison
1050     * on the head page to show that the hugepage is hwpoisoned
1051     */
1052    if (PageTail(p) && TestSetPageHWPoison(hpage)) {
1053        action_result(pfn, "hugepage already hardware poisoned",
1054                IGNORED);
1055        unlock_page(hpage);
1056        put_page(hpage);
1057        return 0;
1058    }
1059    /*
1060     * Set PG_hwpoison on all pages in an error hugepage,
1061     * because containment is done in hugepage unit for now.
1062     * Since we have done TestSetPageHWPoison() for the head page with
1063     * page lock held, we can safely set PG_hwpoison bits on tail pages.
1064     */
1065    if (PageHuge(p))
1066        set_page_hwpoison_huge_page(hpage);
1067
1068    wait_on_page_writeback(p);
1069
1070    /*
1071     * Now take care of user space mappings.
1072     * Abort on fail: __remove_from_page_cache() assumes unmapped page.
1073     */
1074    if (hwpoison_user_mappings(p, pfn, trapno) != SWAP_SUCCESS) {
1075        printk(KERN_ERR "MCE %#lx: cannot unmap page, give up\n", pfn);
1076        res = -EBUSY;
1077        goto out;
1078    }
1079
1080    /*
1081     * Torn down by someone else?
1082     */
1083    if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) {
1084        action_result(pfn, "already truncated LRU", IGNORED);
1085        res = -EBUSY;
1086        goto out;
1087    }
1088
1089    res = -EBUSY;
1090    for (ps = error_states;; ps++) {
1091        if ((p->flags & ps->mask) == ps->res) {
1092            res = page_action(ps, p, pfn);
1093            break;
1094        }
1095    }
1096out:
1097    unlock_page(hpage);
1098    return res;
1099}
1100EXPORT_SYMBOL_GPL(__memory_failure);
1101
1102/**
1103 * memory_failure - Handle memory failure of a page.
1104 * @pfn: Page Number of the corrupted page
1105 * @trapno: Trap number reported in the signal to user space.
1106 *
1107 * This function is called by the low level machine check code
1108 * of an architecture when it detects hardware memory corruption
1109 * of a page. It tries its best to recover, which includes
1110 * dropping pages, killing processes etc.
1111 *
1112 * The function is primarily of use for corruptions that
1113 * happen outside the current execution context (e.g. when
1114 * detected by a background scrubber)
1115 *
1116 * Must run in process context (e.g. a work queue) with interrupts
1117 * enabled and no spinlocks hold.
1118 */
1119void memory_failure(unsigned long pfn, int trapno)
1120{
1121    __memory_failure(pfn, trapno, 0);
1122}
1123
1124/**
1125 * unpoison_memory - Unpoison a previously poisoned page
1126 * @pfn: Page number of the to be unpoisoned page
1127 *
1128 * Software-unpoison a page that has been poisoned by
1129 * memory_failure() earlier.
1130 *
1131 * This is only done on the software-level, so it only works
1132 * for linux injected failures, not real hardware failures
1133 *
1134 * Returns 0 for success, otherwise -errno.
1135 */
1136int unpoison_memory(unsigned long pfn)
1137{
1138    struct page *page;
1139    struct page *p;
1140    int freeit = 0;
1141    unsigned int nr_pages;
1142
1143    if (!pfn_valid(pfn))
1144        return -ENXIO;
1145
1146    p = pfn_to_page(pfn);
1147    page = compound_head(p);
1148
1149    if (!PageHWPoison(p)) {
1150        pr_debug("MCE: Page was already unpoisoned %#lx\n", pfn);
1151        return 0;
1152    }
1153
1154    nr_pages = 1 << compound_order(page);
1155
1156    if (!get_page_unless_zero(page)) {
1157        if (TestClearPageHWPoison(p))
1158            atomic_long_sub(nr_pages, &mce_bad_pages);
1159        pr_debug("MCE: Software-unpoisoned free page %#lx\n", pfn);
1160        return 0;
1161    }
1162
1163    lock_page_nosync(page);
1164    /*
1165     * This test is racy because PG_hwpoison is set outside of page lock.
1166     * That's acceptable because that won't trigger kernel panic. Instead,
1167     * the PG_hwpoison page will be caught and isolated on the entrance to
1168     * the free buddy page pool.
1169     */
1170    if (TestClearPageHWPoison(page)) {
1171        pr_debug("MCE: Software-unpoisoned page %#lx\n", pfn);
1172        atomic_long_sub(nr_pages, &mce_bad_pages);
1173        freeit = 1;
1174    }
1175    if (PageHuge(p))
1176        clear_page_hwpoison_huge_page(page);
1177    unlock_page(page);
1178
1179    put_page(page);
1180    if (freeit)
1181        put_page(page);
1182
1183    return 0;
1184}
1185EXPORT_SYMBOL(unpoison_memory);
1186
1187static struct page *new_page(struct page *p, unsigned long private, int **x)
1188{
1189    int nid = page_to_nid(p);
1190    return alloc_pages_exact_node(nid, GFP_HIGHUSER_MOVABLE, 0);
1191}
1192
1193/*
1194 * Safely get reference count of an arbitrary page.
1195 * Returns 0 for a free page, -EIO for a zero refcount page
1196 * that is not free, and 1 for any other page type.
1197 * For 1 the page is returned with increased page count, otherwise not.
1198 */
1199static int get_any_page(struct page *p, unsigned long pfn, int flags)
1200{
1201    int ret;
1202
1203    if (flags & MF_COUNT_INCREASED)
1204        return 1;
1205
1206    /*
1207     * The lock_system_sleep prevents a race with memory hotplug,
1208     * because the isolation assumes there's only a single user.
1209     * This is a big hammer, a better would be nicer.
1210     */
1211    lock_system_sleep();
1212
1213    /*
1214     * Isolate the page, so that it doesn't get reallocated if it
1215     * was free.
1216     */
1217    set_migratetype_isolate(p);
1218    if (!get_page_unless_zero(compound_head(p))) {
1219        if (is_free_buddy_page(p)) {
1220            pr_debug("get_any_page: %#lx free buddy page\n", pfn);
1221            /* Set hwpoison bit while page is still isolated */
1222            SetPageHWPoison(p);
1223            ret = 0;
1224        } else {
1225            pr_debug("get_any_page: %#lx: unknown zero refcount page type %lx\n",
1226                pfn, p->flags);
1227            ret = -EIO;
1228        }
1229    } else {
1230        /* Not a free page */
1231        ret = 1;
1232    }
1233    unset_migratetype_isolate(p);
1234    unlock_system_sleep();
1235    return ret;
1236}
1237
1238/**
1239 * soft_offline_page - Soft offline a page.
1240 * @page: page to offline
1241 * @flags: flags. Same as memory_failure().
1242 *
1243 * Returns 0 on success, otherwise negated errno.
1244 *
1245 * Soft offline a page, by migration or invalidation,
1246 * without killing anything. This is for the case when
1247 * a page is not corrupted yet (so it's still valid to access),
1248 * but has had a number of corrected errors and is better taken
1249 * out.
1250 *
1251 * The actual policy on when to do that is maintained by
1252 * user space.
1253 *
1254 * This should never impact any application or cause data loss,
1255 * however it might take some time.
1256 *
1257 * This is not a 100% solution for all memory, but tries to be
1258 * ``good enough'' for the majority of memory.
1259 */
1260int soft_offline_page(struct page *page, int flags)
1261{
1262    int ret;
1263    unsigned long pfn = page_to_pfn(page);
1264
1265    ret = get_any_page(page, pfn, flags);
1266    if (ret < 0)
1267        return ret;
1268    if (ret == 0)
1269        goto done;
1270
1271    /*
1272     * Page cache page we can handle?
1273     */
1274    if (!PageLRU(page)) {
1275        /*
1276         * Try to free it.
1277         */
1278        put_page(page);
1279        shake_page(page, 1);
1280
1281        /*
1282         * Did it turn free?
1283         */
1284        ret = get_any_page(page, pfn, 0);
1285        if (ret < 0)
1286            return ret;
1287        if (ret == 0)
1288            goto done;
1289    }
1290    if (!PageLRU(page)) {
1291        pr_debug("soft_offline: %#lx: unknown non LRU page type %lx\n",
1292                pfn, page->flags);
1293        return -EIO;
1294    }
1295
1296    lock_page(page);
1297    wait_on_page_writeback(page);
1298
1299    /*
1300     * Synchronized using the page lock with memory_failure()
1301     */
1302    if (PageHWPoison(page)) {
1303        unlock_page(page);
1304        put_page(page);
1305        pr_debug("soft offline: %#lx page already poisoned\n", pfn);
1306        return -EBUSY;
1307    }
1308
1309    /*
1310     * Try to invalidate first. This should work for
1311     * non dirty unmapped page cache pages.
1312     */
1313    ret = invalidate_inode_page(page);
1314    unlock_page(page);
1315
1316    /*
1317     * Drop count because page migration doesn't like raised
1318     * counts. The page could get re-allocated, but if it becomes
1319     * LRU the isolation will just fail.
1320     * RED-PEN would be better to keep it isolated here, but we
1321     * would need to fix isolation locking first.
1322     */
1323    put_page(page);
1324    if (ret == 1) {
1325        ret = 0;
1326        pr_debug("soft_offline: %#lx: invalidated\n", pfn);
1327        goto done;
1328    }
1329
1330    /*
1331     * Simple invalidation didn't work.
1332     * Try to migrate to a new page instead. migrate.c
1333     * handles a large number of cases for us.
1334     */
1335    ret = isolate_lru_page(page);
1336    if (!ret) {
1337        LIST_HEAD(pagelist);
1338
1339        list_add(&page->lru, &pagelist);
1340        ret = migrate_pages(&pagelist, new_page, MPOL_MF_MOVE_ALL, 0);
1341        if (ret) {
1342            pr_debug("soft offline: %#lx: migration failed %d, type %lx\n",
1343                pfn, ret, page->flags);
1344            if (ret > 0)
1345                ret = -EIO;
1346        }
1347    } else {
1348        pr_debug("soft offline: %#lx: isolation failed: %d, page count %d, type %lx\n",
1349                pfn, ret, page_count(page), page->flags);
1350    }
1351    if (ret)
1352        return ret;
1353
1354done:
1355    atomic_long_add(1, &mce_bad_pages);
1356    SetPageHWPoison(page);
1357    /* keep elevated page count for bad page */
1358    return ret;
1359}
1360
1361/*
1362 * The caller must hold current->mm->mmap_sem in read mode.
1363 */
1364int is_hwpoison_address(unsigned long addr)
1365{
1366    pgd_t *pgdp;
1367    pud_t pud, *pudp;
1368    pmd_t pmd, *pmdp;
1369    pte_t pte, *ptep;
1370    swp_entry_t entry;
1371
1372    pgdp = pgd_offset(current->mm, addr);
1373    if (!pgd_present(*pgdp))
1374        return 0;
1375    pudp = pud_offset(pgdp, addr);
1376    pud = *pudp;
1377    if (!pud_present(pud) || pud_large(pud))
1378        return 0;
1379    pmdp = pmd_offset(pudp, addr);
1380    pmd = *pmdp;
1381    if (!pmd_present(pmd) || pmd_large(pmd))
1382        return 0;
1383    ptep = pte_offset_map(pmdp, addr);
1384    pte = *ptep;
1385    pte_unmap(ptep);
1386    if (!is_swap_pte(pte))
1387        return 0;
1388    entry = pte_to_swp_entry(pte);
1389    return is_hwpoison_entry(entry);
1390}
1391EXPORT_SYMBOL_GPL(is_hwpoison_address);
1392

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