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 multi-bit ECC memory or cache
11 * failure.
12 *
13 * In addition there is a "soft offline" entry point that allows stop using
14 * not-yet-corrupted-by-suspicious pages without killing anything.
15 *
16 * Handles page cache pages in various states. The tricky part
17 * here is that we can access any page asynchronously in respect to
18 * other VM users, because memory failures could happen anytime and
19 * anywhere. This could violate some of their assumptions. This is why
20 * this code has to be extremely careful. Generally it tries to use
21 * normal locking rules, as in get the standard locks, even if that means
22 * the error handling takes potentially a long time.
23 *
24 * There are several operations here with exponential complexity because
25 * of unsuitable VM data structures. For example the operation to map back
26 * from RMAP chains to processes has to walk the complete process list and
27 * has non linear complexity with the number. But since memory corruptions
28 * are rare we hope to get away with this. This avoids impacting the core
29 * VM.
30 */
31
32/*
33 * Notebook:
34 * - hugetlb needs more code
35 * - kcore/oldmem/vmcore/mem/kmem check for hwpoison pages
36 * - pass bad pages to kdump next kernel
37 */
38#include <linux/kernel.h>
39#include <linux/mm.h>
40#include <linux/page-flags.h>
41#include <linux/kernel-page-flags.h>
42#include <linux/sched.h>
43#include <linux/ksm.h>
44#include <linux/rmap.h>
45#include <linux/export.h>
46#include <linux/pagemap.h>
47#include <linux/swap.h>
48#include <linux/backing-dev.h>
49#include <linux/migrate.h>
50#include <linux/page-isolation.h>
51#include <linux/suspend.h>
52#include <linux/slab.h>
53#include <linux/swapops.h>
54#include <linux/hugetlb.h>
55#include <linux/memory_hotplug.h>
56#include <linux/mm_inline.h>
57#include <linux/kfifo.h>
58#include "internal.h"
59
60int sysctl_memory_failure_early_kill __read_mostly = 0;
61
62int sysctl_memory_failure_recovery __read_mostly = 1;
63
64atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0);
65
66#if defined(CONFIG_HWPOISON_INJECT) || defined(CONFIG_HWPOISON_INJECT_MODULE)
67
68u32 hwpoison_filter_enable = 0;
69u32 hwpoison_filter_dev_major = ~0U;
70u32 hwpoison_filter_dev_minor = ~0U;
71u64 hwpoison_filter_flags_mask;
72u64 hwpoison_filter_flags_value;
73EXPORT_SYMBOL_GPL(hwpoison_filter_enable);
74EXPORT_SYMBOL_GPL(hwpoison_filter_dev_major);
75EXPORT_SYMBOL_GPL(hwpoison_filter_dev_minor);
76EXPORT_SYMBOL_GPL(hwpoison_filter_flags_mask);
77EXPORT_SYMBOL_GPL(hwpoison_filter_flags_value);
78
79static int hwpoison_filter_dev(struct page *p)
80{
81    struct address_space *mapping;
82    dev_t dev;
83
84    if (hwpoison_filter_dev_major == ~0U &&
85        hwpoison_filter_dev_minor == ~0U)
86        return 0;
87
88    /*
89     * page_mapping() does not accept slab pages.
90     */
91    if (PageSlab(p))
92        return -EINVAL;
93
94    mapping = page_mapping(p);
95    if (mapping == NULL || mapping->host == NULL)
96        return -EINVAL;
97
98    dev = mapping->host->i_sb->s_dev;
99    if (hwpoison_filter_dev_major != ~0U &&
100        hwpoison_filter_dev_major != MAJOR(dev))
101        return -EINVAL;
102    if (hwpoison_filter_dev_minor != ~0U &&
103        hwpoison_filter_dev_minor != MINOR(dev))
104        return -EINVAL;
105
106    return 0;
107}
108
109static int hwpoison_filter_flags(struct page *p)
110{
111    if (!hwpoison_filter_flags_mask)
112        return 0;
113
114    if ((stable_page_flags(p) & hwpoison_filter_flags_mask) ==
115                    hwpoison_filter_flags_value)
116        return 0;
117    else
118        return -EINVAL;
119}
120
121/*
122 * This allows stress tests to limit test scope to a collection of tasks
123 * by putting them under some memcg. This prevents killing unrelated/important
124 * processes such as /sbin/init. Note that the target task may share clean
125 * pages with init (eg. libc text), which is harmless. If the target task
126 * share _dirty_ pages with another task B, the test scheme must make sure B
127 * is also included in the memcg. At last, due to race conditions this filter
128 * can only guarantee that the page either belongs to the memcg tasks, or is
129 * a freed page.
130 */
131#ifdef CONFIG_MEMCG_SWAP
132u64 hwpoison_filter_memcg;
133EXPORT_SYMBOL_GPL(hwpoison_filter_memcg);
134static int hwpoison_filter_task(struct page *p)
135{
136    struct mem_cgroup *mem;
137    struct cgroup_subsys_state *css;
138    unsigned long ino;
139
140    if (!hwpoison_filter_memcg)
141        return 0;
142
143    mem = try_get_mem_cgroup_from_page(p);
144    if (!mem)
145        return -EINVAL;
146
147    css = mem_cgroup_css(mem);
148    /* root_mem_cgroup has NULL dentries */
149    if (!css->cgroup->dentry)
150        return -EINVAL;
151
152    ino = css->cgroup->dentry->d_inode->i_ino;
153    css_put(css);
154
155    if (ino != hwpoison_filter_memcg)
156        return -EINVAL;
157
158    return 0;
159}
160#else
161static int hwpoison_filter_task(struct page *p) { return 0; }
162#endif
163
164int hwpoison_filter(struct page *p)
165{
166    if (!hwpoison_filter_enable)
167        return 0;
168
169    if (hwpoison_filter_dev(p))
170        return -EINVAL;
171
172    if (hwpoison_filter_flags(p))
173        return -EINVAL;
174
175    if (hwpoison_filter_task(p))
176        return -EINVAL;
177
178    return 0;
179}
180#else
181int hwpoison_filter(struct page *p)
182{
183    return 0;
184}
185#endif
186
187EXPORT_SYMBOL_GPL(hwpoison_filter);
188
189/*
190 * Send all the processes who have the page mapped a signal.
191 * ``action optional'' if they are not immediately affected by the error
192 * ``action required'' if error happened in current execution context
193 */
194static int kill_proc(struct task_struct *t, unsigned long addr, int trapno,
195            unsigned long pfn, struct page *page, int flags)
196{
197    struct siginfo si;
198    int ret;
199
200    printk(KERN_ERR
201        "MCE %#lx: Killing %s:%d due to hardware memory corruption\n",
202        pfn, t->comm, t->pid);
203    si.si_signo = SIGBUS;
204    si.si_errno = 0;
205    si.si_addr = (void *)addr;
206#ifdef __ARCH_SI_TRAPNO
207    si.si_trapno = trapno;
208#endif
209    si.si_addr_lsb = compound_trans_order(compound_head(page)) + PAGE_SHIFT;
210
211    if ((flags & MF_ACTION_REQUIRED) && t == current) {
212        si.si_code = BUS_MCEERR_AR;
213        ret = force_sig_info(SIGBUS, &si, t);
214    } else {
215        /*
216         * Don't use force here, it's convenient if the signal
217         * can be temporarily blocked.
218         * This could cause a loop when the user sets SIGBUS
219         * to SIG_IGN, but hopefully no one will do that?
220         */
221        si.si_code = BUS_MCEERR_AO;
222        ret = send_sig_info(SIGBUS, &si, t); /* synchronous? */
223    }
224    if (ret < 0)
225        printk(KERN_INFO "MCE: Error sending signal to %s:%d: %d\n",
226               t->comm, t->pid, ret);
227    return ret;
228}
229
230/*
231 * When a unknown page type is encountered drain as many buffers as possible
232 * in the hope to turn the page into a LRU or free page, which we can handle.
233 */
234void shake_page(struct page *p, int access)
235{
236    if (!PageSlab(p)) {
237        lru_add_drain_all();
238        if (PageLRU(p))
239            return;
240        drain_all_pages();
241        if (PageLRU(p) || is_free_buddy_page(p))
242            return;
243    }
244
245    /*
246     * Only call shrink_slab here (which would also shrink other caches) if
247     * access is not potentially fatal.
248     */
249    if (access) {
250        int nr;
251        do {
252            struct shrink_control shrink = {
253                .gfp_mask = GFP_KERNEL,
254            };
255
256            nr = shrink_slab(&shrink, 1000, 1000);
257            if (page_count(p) == 1)
258                break;
259        } while (nr > 10);
260    }
261}
262EXPORT_SYMBOL_GPL(shake_page);
263
264/*
265 * Kill all processes that have a poisoned page mapped and then isolate
266 * the page.
267 *
268 * General strategy:
269 * Find all processes having the page mapped and kill them.
270 * But we keep a page reference around so that the page is not
271 * actually freed yet.
272 * Then stash the page away
273 *
274 * There's no convenient way to get back to mapped processes
275 * from the VMAs. So do a brute-force search over all
276 * running processes.
277 *
278 * Remember that machine checks are not common (or rather
279 * if they are common you have other problems), so this shouldn't
280 * be a performance issue.
281 *
282 * Also there are some races possible while we get from the
283 * error detection to actually handle it.
284 */
285
286struct to_kill {
287    struct list_head nd;
288    struct task_struct *tsk;
289    unsigned long addr;
290    char addr_valid;
291};
292
293/*
294 * Failure handling: if we can't find or can't kill a process there's
295 * not much we can do. We just print a message and ignore otherwise.
296 */
297
298/*
299 * Schedule a process for later kill.
300 * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
301 * TBD would GFP_NOIO be enough?
302 */
303static void add_to_kill(struct task_struct *tsk, struct page *p,
304               struct vm_area_struct *vma,
305               struct list_head *to_kill,
306               struct to_kill **tkc)
307{
308    struct to_kill *tk;
309
310    if (*tkc) {
311        tk = *tkc;
312        *tkc = NULL;
313    } else {
314        tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
315        if (!tk) {
316            printk(KERN_ERR
317        "MCE: Out of memory while machine check handling\n");
318            return;
319        }
320    }
321    tk->addr = page_address_in_vma(p, vma);
322    tk->addr_valid = 1;
323
324    /*
325     * In theory we don't have to kill when the page was
326     * munmaped. But it could be also a mremap. Since that's
327     * likely very rare kill anyways just out of paranoia, but use
328     * a SIGKILL because the error is not contained anymore.
329     */
330    if (tk->addr == -EFAULT) {
331        pr_info("MCE: Unable to find user space address %lx in %s\n",
332            page_to_pfn(p), tsk->comm);
333        tk->addr_valid = 0;
334    }
335    get_task_struct(tsk);
336    tk->tsk = tsk;
337    list_add_tail(&tk->nd, to_kill);
338}
339
340/*
341 * Kill the processes that have been collected earlier.
342 *
343 * Only do anything when DOIT is set, otherwise just free the list
344 * (this is used for clean pages which do not need killing)
345 * Also when FAIL is set do a force kill because something went
346 * wrong earlier.
347 */
348static void kill_procs(struct list_head *to_kill, int forcekill, int trapno,
349              int fail, struct page *page, unsigned long pfn,
350              int flags)
351{
352    struct to_kill *tk, *next;
353
354    list_for_each_entry_safe (tk, next, to_kill, nd) {
355        if (forcekill) {
356            /*
357             * In case something went wrong with munmapping
358             * make sure the process doesn't catch the
359             * signal and then access the memory. Just kill it.
360             */
361            if (fail || tk->addr_valid == 0) {
362                printk(KERN_ERR
363        "MCE %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n",
364                    pfn, tk->tsk->comm, tk->tsk->pid);
365                force_sig(SIGKILL, tk->tsk);
366            }
367
368            /*
369             * In theory the process could have mapped
370             * something else on the address in-between. We could
371             * check for that, but we need to tell the
372             * process anyways.
373             */
374            else if (kill_proc(tk->tsk, tk->addr, trapno,
375                          pfn, page, flags) < 0)
376                printk(KERN_ERR
377        "MCE %#lx: Cannot send advisory machine check signal to %s:%d\n",
378                    pfn, tk->tsk->comm, tk->tsk->pid);
379        }
380        put_task_struct(tk->tsk);
381        kfree(tk);
382    }
383}
384
385static int task_early_kill(struct task_struct *tsk)
386{
387    if (!tsk->mm)
388        return 0;
389    if (tsk->flags & PF_MCE_PROCESS)
390        return !!(tsk->flags & PF_MCE_EARLY);
391    return sysctl_memory_failure_early_kill;
392}
393
394/*
395 * Collect processes when the error hit an anonymous page.
396 */
397static void collect_procs_anon(struct page *page, struct list_head *to_kill,
398                  struct to_kill **tkc)
399{
400    struct vm_area_struct *vma;
401    struct task_struct *tsk;
402    struct anon_vma *av;
403    pgoff_t pgoff;
404
405    av = page_lock_anon_vma_read(page);
406    if (av == NULL) /* Not actually mapped anymore */
407        return;
408
409    pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
410    read_lock(&tasklist_lock);
411    for_each_process (tsk) {
412        struct anon_vma_chain *vmac;
413
414        if (!task_early_kill(tsk))
415            continue;
416        anon_vma_interval_tree_foreach(vmac, &av->rb_root,
417                           pgoff, pgoff) {
418            vma = vmac->vma;
419            if (!page_mapped_in_vma(page, vma))
420                continue;
421            if (vma->vm_mm == tsk->mm)
422                add_to_kill(tsk, page, vma, to_kill, tkc);
423        }
424    }
425    read_unlock(&tasklist_lock);
426    page_unlock_anon_vma_read(av);
427}
428
429/*
430 * Collect processes when the error hit a file mapped page.
431 */
432static void collect_procs_file(struct page *page, struct list_head *to_kill,
433                  struct to_kill **tkc)
434{
435    struct vm_area_struct *vma;
436    struct task_struct *tsk;
437    struct address_space *mapping = page->mapping;
438
439    mutex_lock(&mapping->i_mmap_mutex);
440    read_lock(&tasklist_lock);
441    for_each_process(tsk) {
442        pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
443
444        if (!task_early_kill(tsk))
445            continue;
446
447        vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff,
448                      pgoff) {
449            /*
450             * Send early kill signal to tasks where a vma covers
451             * the page but the corrupted page is not necessarily
452             * mapped it in its pte.
453             * Assume applications who requested early kill want
454             * to be informed of all such data corruptions.
455             */
456            if (vma->vm_mm == tsk->mm)
457                add_to_kill(tsk, page, vma, to_kill, tkc);
458        }
459    }
460    read_unlock(&tasklist_lock);
461    mutex_unlock(&mapping->i_mmap_mutex);
462}
463
464/*
465 * Collect the processes who have the corrupted page mapped to kill.
466 * This is done in two steps for locking reasons.
467 * First preallocate one tokill structure outside the spin locks,
468 * so that we can kill at least one process reasonably reliable.
469 */
470static void collect_procs(struct page *page, struct list_head *tokill)
471{
472    struct to_kill *tk;
473
474    if (!page->mapping)
475        return;
476
477    tk = kmalloc(sizeof(struct to_kill), GFP_NOIO);
478    if (!tk)
479        return;
480    if (PageAnon(page))
481        collect_procs_anon(page, tokill, &tk);
482    else
483        collect_procs_file(page, tokill, &tk);
484    kfree(tk);
485}
486
487/*
488 * Error handlers for various types of pages.
489 */
490
491enum outcome {
492    IGNORED, /* Error: cannot be handled */
493    FAILED, /* Error: handling failed */
494    DELAYED, /* Will be handled later */
495    RECOVERED, /* Successfully recovered */
496};
497
498static const char *action_name[] = {
499    [IGNORED] = "Ignored",
500    [FAILED] = "Failed",
501    [DELAYED] = "Delayed",
502    [RECOVERED] = "Recovered",
503};
504
505/*
506 * XXX: It is possible that a page is isolated from LRU cache,
507 * and then kept in swap cache or failed to remove from page cache.
508 * The page count will stop it from being freed by unpoison.
509 * Stress tests should be aware of this memory leak problem.
510 */
511static int delete_from_lru_cache(struct page *p)
512{
513    if (!isolate_lru_page(p)) {
514        /*
515         * Clear sensible page flags, so that the buddy system won't
516         * complain when the page is unpoison-and-freed.
517         */
518        ClearPageActive(p);
519        ClearPageUnevictable(p);
520        /*
521         * drop the page count elevated by isolate_lru_page()
522         */
523        page_cache_release(p);
524        return 0;
525    }
526    return -EIO;
527}
528
529/*
530 * Error hit kernel page.
531 * Do nothing, try to be lucky and not touch this instead. For a few cases we
532 * could be more sophisticated.
533 */
534static int me_kernel(struct page *p, unsigned long pfn)
535{
536    return IGNORED;
537}
538
539/*
540 * Page in unknown state. Do nothing.
541 */
542static int me_unknown(struct page *p, unsigned long pfn)
543{
544    printk(KERN_ERR "MCE %#lx: Unknown page state\n", pfn);
545    return FAILED;
546}
547
548/*
549 * Clean (or cleaned) page cache page.
550 */
551static int me_pagecache_clean(struct page *p, unsigned long pfn)
552{
553    int err;
554    int ret = FAILED;
555    struct address_space *mapping;
556
557    delete_from_lru_cache(p);
558
559    /*
560     * For anonymous pages we're done the only reference left
561     * should be the one m_f() holds.
562     */
563    if (PageAnon(p))
564        return RECOVERED;
565
566    /*
567     * Now truncate the page in the page cache. This is really
568     * more like a "temporary hole punch"
569     * Don't do this for block devices when someone else
570     * has a reference, because it could be file system metadata
571     * and that's not safe to truncate.
572     */
573    mapping = page_mapping(p);
574    if (!mapping) {
575        /*
576         * Page has been teared down in the meanwhile
577         */
578        return FAILED;
579    }
580
581    /*
582     * Truncation is a bit tricky. Enable it per file system for now.
583     *
584     * Open: to take i_mutex or not for this? Right now we don't.
585     */
586    if (mapping->a_ops->error_remove_page) {
587        err = mapping->a_ops->error_remove_page(mapping, p);
588        if (err != 0) {
589            printk(KERN_INFO "MCE %#lx: Failed to punch page: %d\n",
590                    pfn, err);
591        } else if (page_has_private(p) &&
592                !try_to_release_page(p, GFP_NOIO)) {
593            pr_info("MCE %#lx: failed to release buffers\n", pfn);
594        } else {
595            ret = RECOVERED;
596        }
597    } else {
598        /*
599         * If the file system doesn't support it just invalidate
600         * This fails on dirty or anything with private pages
601         */
602        if (invalidate_inode_page(p))
603            ret = RECOVERED;
604        else
605            printk(KERN_INFO "MCE %#lx: Failed to invalidate\n",
606                pfn);
607    }
608    return ret;
609}
610
611/*
612 * Dirty cache page page
613 * Issues: when the error hit a hole page the error is not properly
614 * propagated.
615 */
616static int me_pagecache_dirty(struct page *p, unsigned long pfn)
617{
618    struct address_space *mapping = page_mapping(p);
619
620    SetPageError(p);
621    /* TBD: print more information about the file. */
622    if (mapping) {
623        /*
624         * IO error will be reported by write(), fsync(), etc.
625         * who check the mapping.
626         * This way the application knows that something went
627         * wrong with its dirty file data.
628         *
629         * There's one open issue:
630         *
631         * The EIO will be only reported on the next IO
632         * operation and then cleared through the IO map.
633         * Normally Linux has two mechanisms to pass IO error
634         * first through the AS_EIO flag in the address space
635         * and then through the PageError flag in the page.
636         * Since we drop pages on memory failure handling the
637         * only mechanism open to use is through AS_AIO.
638         *
639         * This has the disadvantage that it gets cleared on
640         * the first operation that returns an error, while
641         * the PageError bit is more sticky and only cleared
642         * when the page is reread or dropped. If an
643         * application assumes it will always get error on
644         * fsync, but does other operations on the fd before
645         * and the page is dropped between then the error
646         * will not be properly reported.
647         *
648         * This can already happen even without hwpoisoned
649         * pages: first on metadata IO errors (which only
650         * report through AS_EIO) or when the page is dropped
651         * at the wrong time.
652         *
653         * So right now we assume that the application DTRT on
654         * the first EIO, but we're not worse than other parts
655         * of the kernel.
656         */
657        mapping_set_error(mapping, EIO);
658    }
659
660    return me_pagecache_clean(p, pfn);
661}
662
663/*
664 * Clean and dirty swap cache.
665 *
666 * Dirty swap cache page is tricky to handle. The page could live both in page
667 * cache and swap cache(ie. page is freshly swapped in). So it could be
668 * referenced concurrently by 2 types of PTEs:
669 * normal PTEs and swap PTEs. We try to handle them consistently by calling
670 * try_to_unmap(TTU_IGNORE_HWPOISON) to convert the normal PTEs to swap PTEs,
671 * and then
672 * - clear dirty bit to prevent IO
673 * - remove from LRU
674 * - but keep in the swap cache, so that when we return to it on
675 * a later page fault, we know the application is accessing
676 * corrupted data and shall be killed (we installed simple
677 * interception code in do_swap_page to catch it).
678 *
679 * Clean swap cache pages can be directly isolated. A later page fault will
680 * bring in the known good data from disk.
681 */
682static int me_swapcache_dirty(struct page *p, unsigned long pfn)
683{
684    ClearPageDirty(p);
685    /* Trigger EIO in shmem: */
686    ClearPageUptodate(p);
687
688    if (!delete_from_lru_cache(p))
689        return DELAYED;
690    else
691        return FAILED;
692}
693
694static int me_swapcache_clean(struct page *p, unsigned long pfn)
695{
696    delete_from_swap_cache(p);
697
698    if (!delete_from_lru_cache(p))
699        return RECOVERED;
700    else
701        return FAILED;
702}
703
704/*
705 * Huge pages. Needs work.
706 * Issues:
707 * - Error on hugepage is contained in hugepage unit (not in raw page unit.)
708 * To narrow down kill region to one page, we need to break up pmd.
709 */
710static int me_huge_page(struct page *p, unsigned long pfn)
711{
712    int res = 0;
713    struct page *hpage = compound_head(p);
714    /*
715     * We can safely recover from error on free or reserved (i.e.
716     * not in-use) hugepage by dequeuing it from freelist.
717     * To check whether a hugepage is in-use or not, we can't use
718     * page->lru because it can be used in other hugepage operations,
719     * such as __unmap_hugepage_range() and gather_surplus_pages().
720     * So instead we use page_mapping() and PageAnon().
721     * We assume that this function is called with page lock held,
722     * so there is no race between isolation and mapping/unmapping.
723     */
724    if (!(page_mapping(hpage) || PageAnon(hpage))) {
725        res = dequeue_hwpoisoned_huge_page(hpage);
726        if (!res)
727            return RECOVERED;
728    }
729    return DELAYED;
730}
731
732/*
733 * Various page states we can handle.
734 *
735 * A page state is defined by its current page->flags bits.
736 * The table matches them in order and calls the right handler.
737 *
738 * This is quite tricky because we can access page at any time
739 * in its live cycle, so all accesses have to be extremely careful.
740 *
741 * This is not complete. More states could be added.
742 * For any missing state don't attempt recovery.
743 */
744
745#define dirty (1UL << PG_dirty)
746#define sc (1UL << PG_swapcache)
747#define unevict (1UL << PG_unevictable)
748#define mlock (1UL << PG_mlocked)
749#define writeback (1UL << PG_writeback)
750#define lru (1UL << PG_lru)
751#define swapbacked (1UL << PG_swapbacked)
752#define head (1UL << PG_head)
753#define tail (1UL << PG_tail)
754#define compound (1UL << PG_compound)
755#define slab (1UL << PG_slab)
756#define reserved (1UL << PG_reserved)
757
758static struct page_state {
759    unsigned long mask;
760    unsigned long res;
761    char *msg;
762    int (*action)(struct page *p, unsigned long pfn);
763} error_states[] = {
764    { reserved, reserved, "reserved kernel", me_kernel },
765    /*
766     * free pages are specially detected outside this table:
767     * PG_buddy pages only make a small fraction of all free pages.
768     */
769
770    /*
771     * Could in theory check if slab page is free or if we can drop
772     * currently unused objects without touching them. But just
773     * treat it as standard kernel for now.
774     */
775    { slab, slab, "kernel slab", me_kernel },
776
777#ifdef CONFIG_PAGEFLAGS_EXTENDED
778    { head, head, "huge", me_huge_page },
779    { tail, tail, "huge", me_huge_page },
780#else
781    { compound, compound, "huge", me_huge_page },
782#endif
783
784    { sc|dirty, sc|dirty, "dirty swapcache", me_swapcache_dirty },
785    { sc|dirty, sc, "clean swapcache", me_swapcache_clean },
786
787    { mlock|dirty, mlock|dirty, "dirty mlocked LRU", me_pagecache_dirty },
788    { mlock, mlock, "clean mlocked LRU", me_pagecache_clean },
789
790    { unevict|dirty, unevict|dirty, "dirty unevictable LRU", me_pagecache_dirty },
791    { unevict, unevict, "clean unevictable LRU", me_pagecache_clean },
792
793    { lru|dirty, lru|dirty, "dirty LRU", me_pagecache_dirty },
794    { lru|dirty, lru, "clean LRU", me_pagecache_clean },
795
796    /*
797     * Catchall entry: must be at end.
798     */
799    { 0, 0, "unknown page state", me_unknown },
800};
801
802#undef dirty
803#undef sc
804#undef unevict
805#undef mlock
806#undef writeback
807#undef lru
808#undef swapbacked
809#undef head
810#undef tail
811#undef compound
812#undef slab
813#undef reserved
814
815/*
816 * "Dirty/Clean" indication is not 100% accurate due to the possibility of
817 * setting PG_dirty outside page lock. See also comment above set_page_dirty().
818 */
819static void action_result(unsigned long pfn, char *msg, int result)
820{
821    pr_err("MCE %#lx: %s page recovery: %s\n",
822        pfn, msg, action_name[result]);
823}
824
825static int page_action(struct page_state *ps, struct page *p,
826            unsigned long pfn)
827{
828    int result;
829    int count;
830
831    result = ps->action(p, pfn);
832    action_result(pfn, ps->msg, result);
833
834    count = page_count(p) - 1;
835    if (ps->action == me_swapcache_dirty && result == DELAYED)
836        count--;
837    if (count != 0) {
838        printk(KERN_ERR
839               "MCE %#lx: %s page still referenced by %d users\n",
840               pfn, ps->msg, count);
841        result = FAILED;
842    }
843
844    /* Could do more checks here if page looks ok */
845    /*
846     * Could adjust zone counters here to correct for the missing page.
847     */
848
849    return (result == RECOVERED || result == DELAYED) ? 0 : -EBUSY;
850}
851
852/*
853 * Do all that is necessary to remove user space mappings. Unmap
854 * the pages and send SIGBUS to the processes if the data was dirty.
855 */
856static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
857                  int trapno, int flags)
858{
859    enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
860    struct address_space *mapping;
861    LIST_HEAD(tokill);
862    int ret;
863    int kill = 1, forcekill;
864    struct page *hpage = compound_head(p);
865    struct page *ppage;
866
867    if (PageReserved(p) || PageSlab(p))
868        return SWAP_SUCCESS;
869
870    /*
871     * This check implies we don't kill processes if their pages
872     * are in the swap cache early. Those are always late kills.
873     */
874    if (!page_mapped(hpage))
875        return SWAP_SUCCESS;
876
877    if (PageKsm(p))
878        return SWAP_FAIL;
879
880    if (PageSwapCache(p)) {
881        printk(KERN_ERR
882               "MCE %#lx: keeping poisoned page in swap cache\n", pfn);
883        ttu |= TTU_IGNORE_HWPOISON;
884    }
885
886    /*
887     * Propagate the dirty bit from PTEs to struct page first, because we
888     * need this to decide if we should kill or just drop the page.
889     * XXX: the dirty test could be racy: set_page_dirty() may not always
890     * be called inside page lock (it's recommended but not enforced).
891     */
892    mapping = page_mapping(hpage);
893    if (!(flags & MF_MUST_KILL) && !PageDirty(hpage) && mapping &&
894        mapping_cap_writeback_dirty(mapping)) {
895        if (page_mkclean(hpage)) {
896            SetPageDirty(hpage);
897        } else {
898            kill = 0;
899            ttu |= TTU_IGNORE_HWPOISON;
900            printk(KERN_INFO
901    "MCE %#lx: corrupted page was clean: dropped without side effects\n",
902                pfn);
903        }
904    }
905
906    /*
907     * ppage: poisoned page
908     * if p is regular page(4k page)
909     * ppage == real poisoned page;
910     * else p is hugetlb or THP, ppage == head page.
911     */
912    ppage = hpage;
913
914    if (PageTransHuge(hpage)) {
915        /*
916         * Verify that this isn't a hugetlbfs head page, the check for
917         * PageAnon is just for avoid tripping a split_huge_page
918         * internal debug check, as split_huge_page refuses to deal with
919         * anything that isn't an anon page. PageAnon can't go away fro
920         * under us because we hold a refcount on the hpage, without a
921         * refcount on the hpage. split_huge_page can't be safely called
922         * in the first place, having a refcount on the tail isn't
923         * enough * to be safe.
924         */
925        if (!PageHuge(hpage) && PageAnon(hpage)) {
926            if (unlikely(split_huge_page(hpage))) {
927                /*
928                 * FIXME: if splitting THP is failed, it is
929                 * better to stop the following operation rather
930                 * than causing panic by unmapping. System might
931                 * survive if the page is freed later.
932                 */
933                printk(KERN_INFO
934                    "MCE %#lx: failed to split THP\n", pfn);
935
936                BUG_ON(!PageHWPoison(p));
937                return SWAP_FAIL;
938            }
939            /* THP is split, so ppage should be the real poisoned page. */
940            ppage = p;
941        }
942    }
943
944    /*
945     * First collect all the processes that have the page
946     * mapped in dirty form. This has to be done before try_to_unmap,
947     * because ttu takes the rmap data structures down.
948     *
949     * Error handling: We ignore errors here because
950     * there's nothing that can be done.
951     */
952    if (kill)
953        collect_procs(ppage, &tokill);
954
955    if (hpage != ppage)
956        lock_page(ppage);
957
958    ret = try_to_unmap(ppage, ttu);
959    if (ret != SWAP_SUCCESS)
960        printk(KERN_ERR "MCE %#lx: failed to unmap page (mapcount=%d)\n",
961                pfn, page_mapcount(ppage));
962
963    if (hpage != ppage)
964        unlock_page(ppage);
965
966    /*
967     * Now that the dirty bit has been propagated to the
968     * struct page and all unmaps done we can decide if
969     * killing is needed or not. Only kill when the page
970     * was dirty or the process is not restartable,
971     * otherwise the tokill list is merely
972     * freed. When there was a problem unmapping earlier
973     * use a more force-full uncatchable kill to prevent
974     * any accesses to the poisoned memory.
975     */
976    forcekill = PageDirty(ppage) || (flags & MF_MUST_KILL);
977    kill_procs(&tokill, forcekill, trapno,
978              ret != SWAP_SUCCESS, p, pfn, flags);
979
980    return ret;
981}
982
983static void set_page_hwpoison_huge_page(struct page *hpage)
984{
985    int i;
986    int nr_pages = 1 << compound_trans_order(hpage);
987    for (i = 0; i < nr_pages; i++)
988        SetPageHWPoison(hpage + i);
989}
990
991static void clear_page_hwpoison_huge_page(struct page *hpage)
992{
993    int i;
994    int nr_pages = 1 << compound_trans_order(hpage);
995    for (i = 0; i < nr_pages; i++)
996        ClearPageHWPoison(hpage + i);
997}
998
999/**
1000 * memory_failure - Handle memory failure of a page.
1001 * @pfn: Page Number of the corrupted page
1002 * @trapno: Trap number reported in the signal to user space.
1003 * @flags: fine tune action taken
1004 *
1005 * This function is called by the low level machine check code
1006 * of an architecture when it detects hardware memory corruption
1007 * of a page. It tries its best to recover, which includes
1008 * dropping pages, killing processes etc.
1009 *
1010 * The function is primarily of use for corruptions that
1011 * happen outside the current execution context (e.g. when
1012 * detected by a background scrubber)
1013 *
1014 * Must run in process context (e.g. a work queue) with interrupts
1015 * enabled and no spinlocks hold.
1016 */
1017int memory_failure(unsigned long pfn, int trapno, int flags)
1018{
1019    struct page_state *ps;
1020    struct page *p;
1021    struct page *hpage;
1022    int res;
1023    unsigned int nr_pages;
1024    unsigned long page_flags;
1025
1026    if (!sysctl_memory_failure_recovery)
1027        panic("Memory failure from trap %d on page %lx", trapno, pfn);
1028
1029    if (!pfn_valid(pfn)) {
1030        printk(KERN_ERR
1031               "MCE %#lx: memory outside kernel control\n",
1032               pfn);
1033        return -ENXIO;
1034    }
1035
1036    p = pfn_to_page(pfn);
1037    hpage = compound_head(p);
1038    if (TestSetPageHWPoison(p)) {
1039        printk(KERN_ERR "MCE %#lx: already hardware poisoned\n", pfn);
1040        return 0;
1041    }
1042
1043    /*
1044     * Currently errors on hugetlbfs pages are measured in hugepage units,
1045     * so nr_pages should be 1 << compound_order. OTOH when errors are on
1046     * transparent hugepages, they are supposed to be split and error
1047     * measurement is done in normal page units. So nr_pages should be one
1048     * in this case.
1049     */
1050    if (PageHuge(p))
1051        nr_pages = 1 << compound_order(hpage);
1052    else /* normal page or thp */
1053        nr_pages = 1;
1054    atomic_long_add(nr_pages, &num_poisoned_pages);
1055
1056    /*
1057     * We need/can do nothing about count=0 pages.
1058     * 1) it's a free page, and therefore in safe hand:
1059     * prep_new_page() will be the gate keeper.
1060     * 2) it's a free hugepage, which is also safe:
1061     * an affected hugepage will be dequeued from hugepage freelist,
1062     * so there's no concern about reusing it ever after.
1063     * 3) it's part of a non-compound high order page.
1064     * Implies some kernel user: cannot stop them from
1065     * R/W the page; let's pray that the page has been
1066     * used and will be freed some time later.
1067     * In fact it's dangerous to directly bump up page count from 0,
1068     * that may make page_freeze_refs()/page_unfreeze_refs() mismatch.
1069     */
1070    if (!(flags & MF_COUNT_INCREASED) &&
1071        !get_page_unless_zero(hpage)) {
1072        if (is_free_buddy_page(p)) {
1073            action_result(pfn, "free buddy", DELAYED);
1074            return 0;
1075        } else if (PageHuge(hpage)) {
1076            /*
1077             * Check "just unpoisoned", "filter hit", and
1078             * "race with other subpage."
1079             */
1080            lock_page(hpage);
1081            if (!PageHWPoison(hpage)
1082                || (hwpoison_filter(p) && TestClearPageHWPoison(p))
1083                || (p != hpage && TestSetPageHWPoison(hpage))) {
1084                atomic_long_sub(nr_pages, &num_poisoned_pages);
1085                return 0;
1086            }
1087            set_page_hwpoison_huge_page(hpage);
1088            res = dequeue_hwpoisoned_huge_page(hpage);
1089            action_result(pfn, "free huge",
1090                      res ? IGNORED : DELAYED);
1091            unlock_page(hpage);
1092            return res;
1093        } else {
1094            action_result(pfn, "high order kernel", IGNORED);
1095            return -EBUSY;
1096        }
1097    }
1098
1099    /*
1100     * We ignore non-LRU pages for good reasons.
1101     * - PG_locked is only well defined for LRU pages and a few others
1102     * - to avoid races with __set_page_locked()
1103     * - to avoid races with __SetPageSlab*() (and more non-atomic ops)
1104     * The check (unnecessarily) ignores LRU pages being isolated and
1105     * walked by the page reclaim code, however that's not a big loss.
1106     */
1107    if (!PageHuge(p) && !PageTransTail(p)) {
1108        if (!PageLRU(p))
1109            shake_page(p, 0);
1110        if (!PageLRU(p)) {
1111            /*
1112             * shake_page could have turned it free.
1113             */
1114            if (is_free_buddy_page(p)) {
1115                action_result(pfn, "free buddy, 2nd try",
1116                        DELAYED);
1117                return 0;
1118            }
1119            action_result(pfn, "non LRU", IGNORED);
1120            put_page(p);
1121            return -EBUSY;
1122        }
1123    }
1124
1125    /*
1126     * Lock the page and wait for writeback to finish.
1127     * It's very difficult to mess with pages currently under IO
1128     * and in many cases impossible, so we just avoid it here.
1129     */
1130    lock_page(hpage);
1131
1132    /*
1133     * We use page flags to determine what action should be taken, but
1134     * the flags can be modified by the error containment action. One
1135     * example is an mlocked page, where PG_mlocked is cleared by
1136     * page_remove_rmap() in try_to_unmap_one(). So to determine page status
1137     * correctly, we save a copy of the page flags at this time.
1138     */
1139    page_flags = p->flags;
1140
1141    /*
1142     * unpoison always clear PG_hwpoison inside page lock
1143     */
1144    if (!PageHWPoison(p)) {
1145        printk(KERN_ERR "MCE %#lx: just unpoisoned\n", pfn);
1146        res = 0;
1147        goto out;
1148    }
1149    if (hwpoison_filter(p)) {
1150        if (TestClearPageHWPoison(p))
1151            atomic_long_sub(nr_pages, &num_poisoned_pages);
1152        unlock_page(hpage);
1153        put_page(hpage);
1154        return 0;
1155    }
1156
1157    /*
1158     * For error on the tail page, we should set PG_hwpoison
1159     * on the head page to show that the hugepage is hwpoisoned
1160     */
1161    if (PageHuge(p) && PageTail(p) && TestSetPageHWPoison(hpage)) {
1162        action_result(pfn, "hugepage already hardware poisoned",
1163                IGNORED);
1164        unlock_page(hpage);
1165        put_page(hpage);
1166        return 0;
1167    }
1168    /*
1169     * Set PG_hwpoison on all pages in an error hugepage,
1170     * because containment is done in hugepage unit for now.
1171     * Since we have done TestSetPageHWPoison() for the head page with
1172     * page lock held, we can safely set PG_hwpoison bits on tail pages.
1173     */
1174    if (PageHuge(p))
1175        set_page_hwpoison_huge_page(hpage);
1176
1177    wait_on_page_writeback(p);
1178
1179    /*
1180     * Now take care of user space mappings.
1181     * Abort on fail: __delete_from_page_cache() assumes unmapped page.
1182     */
1183    if (hwpoison_user_mappings(p, pfn, trapno, flags) != SWAP_SUCCESS) {
1184        printk(KERN_ERR "MCE %#lx: cannot unmap page, give up\n", pfn);
1185        res = -EBUSY;
1186        goto out;
1187    }
1188
1189    /*
1190     * Torn down by someone else?
1191     */
1192    if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) {
1193        action_result(pfn, "already truncated LRU", IGNORED);
1194        res = -EBUSY;
1195        goto out;
1196    }
1197
1198    res = -EBUSY;
1199    /*
1200     * The first check uses the current page flags which may not have any
1201     * relevant information. The second check with the saved page flagss is
1202     * carried out only if the first check can't determine the page status.
1203     */
1204    for (ps = error_states;; ps++)
1205        if ((p->flags & ps->mask) == ps->res)
1206            break;
1207    if (!ps->mask)
1208        for (ps = error_states;; ps++)
1209            if ((page_flags & ps->mask) == ps->res)
1210                break;
1211    res = page_action(ps, p, pfn);
1212out:
1213    unlock_page(hpage);
1214    return res;
1215}
1216EXPORT_SYMBOL_GPL(memory_failure);
1217
1218#define MEMORY_FAILURE_FIFO_ORDER 4
1219#define MEMORY_FAILURE_FIFO_SIZE (1 << MEMORY_FAILURE_FIFO_ORDER)
1220
1221struct memory_failure_entry {
1222    unsigned long pfn;
1223    int trapno;
1224    int flags;
1225};
1226
1227struct memory_failure_cpu {
1228    DECLARE_KFIFO(fifo, struct memory_failure_entry,
1229              MEMORY_FAILURE_FIFO_SIZE);
1230    spinlock_t lock;
1231    struct work_struct work;
1232};
1233
1234static DEFINE_PER_CPU(struct memory_failure_cpu, memory_failure_cpu);
1235
1236/**
1237 * memory_failure_queue - Schedule handling memory failure of a page.
1238 * @pfn: Page Number of the corrupted page
1239 * @trapno: Trap number reported in the signal to user space.
1240 * @flags: Flags for memory failure handling
1241 *
1242 * This function is called by the low level hardware error handler
1243 * when it detects hardware memory corruption of a page. It schedules
1244 * the recovering of error page, including dropping pages, killing
1245 * processes etc.
1246 *
1247 * The function is primarily of use for corruptions that
1248 * happen outside the current execution context (e.g. when
1249 * detected by a background scrubber)
1250 *
1251 * Can run in IRQ context.
1252 */
1253void memory_failure_queue(unsigned long pfn, int trapno, int flags)
1254{
1255    struct memory_failure_cpu *mf_cpu;
1256    unsigned long proc_flags;
1257    struct memory_failure_entry entry = {
1258        .pfn = pfn,
1259        .trapno = trapno,
1260        .flags = flags,
1261    };
1262
1263    mf_cpu = &get_cpu_var(memory_failure_cpu);
1264    spin_lock_irqsave(&mf_cpu->lock, proc_flags);
1265    if (kfifo_put(&mf_cpu->fifo, &entry))
1266        schedule_work_on(smp_processor_id(), &mf_cpu->work);
1267    else
1268        pr_err("Memory failure: buffer overflow when queuing memory failure at 0x%#lx\n",
1269               pfn);
1270    spin_unlock_irqrestore(&mf_cpu->lock, proc_flags);
1271    put_cpu_var(memory_failure_cpu);
1272}
1273EXPORT_SYMBOL_GPL(memory_failure_queue);
1274
1275static void memory_failure_work_func(struct work_struct *work)
1276{
1277    struct memory_failure_cpu *mf_cpu;
1278    struct memory_failure_entry entry = { 0, };
1279    unsigned long proc_flags;
1280    int gotten;
1281
1282    mf_cpu = &__get_cpu_var(memory_failure_cpu);
1283    for (;;) {
1284        spin_lock_irqsave(&mf_cpu->lock, proc_flags);
1285        gotten = kfifo_get(&mf_cpu->fifo, &entry);
1286        spin_unlock_irqrestore(&mf_cpu->lock, proc_flags);
1287        if (!gotten)
1288            break;
1289        memory_failure(entry.pfn, entry.trapno, entry.flags);
1290    }
1291}
1292
1293static int __init memory_failure_init(void)
1294{
1295    struct memory_failure_cpu *mf_cpu;
1296    int cpu;
1297
1298    for_each_possible_cpu(cpu) {
1299        mf_cpu = &per_cpu(memory_failure_cpu, cpu);
1300        spin_lock_init(&mf_cpu->lock);
1301        INIT_KFIFO(mf_cpu->fifo);
1302        INIT_WORK(&mf_cpu->work, memory_failure_work_func);
1303    }
1304
1305    return 0;
1306}
1307core_initcall(memory_failure_init);
1308
1309/**
1310 * unpoison_memory - Unpoison a previously poisoned page
1311 * @pfn: Page number of the to be unpoisoned page
1312 *
1313 * Software-unpoison a page that has been poisoned by
1314 * memory_failure() earlier.
1315 *
1316 * This is only done on the software-level, so it only works
1317 * for linux injected failures, not real hardware failures
1318 *
1319 * Returns 0 for success, otherwise -errno.
1320 */
1321int unpoison_memory(unsigned long pfn)
1322{
1323    struct page *page;
1324    struct page *p;
1325    int freeit = 0;
1326    unsigned int nr_pages;
1327
1328    if (!pfn_valid(pfn))
1329        return -ENXIO;
1330
1331    p = pfn_to_page(pfn);
1332    page = compound_head(p);
1333
1334    if (!PageHWPoison(p)) {
1335        pr_info("MCE: Page was already unpoisoned %#lx\n", pfn);
1336        return 0;
1337    }
1338
1339    nr_pages = 1 << compound_trans_order(page);
1340
1341    if (!get_page_unless_zero(page)) {
1342        /*
1343         * Since HWPoisoned hugepage should have non-zero refcount,
1344         * race between memory failure and unpoison seems to happen.
1345         * In such case unpoison fails and memory failure runs
1346         * to the end.
1347         */
1348        if (PageHuge(page)) {
1349            pr_info("MCE: Memory failure is now running on free hugepage %#lx\n", pfn);
1350            return 0;
1351        }
1352        if (TestClearPageHWPoison(p))
1353            atomic_long_sub(nr_pages, &num_poisoned_pages);
1354        pr_info("MCE: Software-unpoisoned free page %#lx\n", pfn);
1355        return 0;
1356    }
1357
1358    lock_page(page);
1359    /*
1360     * This test is racy because PG_hwpoison is set outside of page lock.
1361     * That's acceptable because that won't trigger kernel panic. Instead,
1362     * the PG_hwpoison page will be caught and isolated on the entrance to
1363     * the free buddy page pool.
1364     */
1365    if (TestClearPageHWPoison(page)) {
1366        pr_info("MCE: Software-unpoisoned page %#lx\n", pfn);
1367        atomic_long_sub(nr_pages, &num_poisoned_pages);
1368        freeit = 1;
1369        if (PageHuge(page))
1370            clear_page_hwpoison_huge_page(page);
1371    }
1372    unlock_page(page);
1373
1374    put_page(page);
1375    if (freeit)
1376        put_page(page);
1377
1378    return 0;
1379}
1380EXPORT_SYMBOL(unpoison_memory);
1381
1382static struct page *new_page(struct page *p, unsigned long private, int **x)
1383{
1384    int nid = page_to_nid(p);
1385    if (PageHuge(p))
1386        return alloc_huge_page_node(page_hstate(compound_head(p)),
1387                           nid);
1388    else
1389        return alloc_pages_exact_node(nid, GFP_HIGHUSER_MOVABLE, 0);
1390}
1391
1392/*
1393 * Safely get reference count of an arbitrary page.
1394 * Returns 0 for a free page, -EIO for a zero refcount page
1395 * that is not free, and 1 for any other page type.
1396 * For 1 the page is returned with increased page count, otherwise not.
1397 */
1398static int __get_any_page(struct page *p, unsigned long pfn, int flags)
1399{
1400    int ret;
1401
1402    if (flags & MF_COUNT_INCREASED)
1403        return 1;
1404
1405    /*
1406     * The lock_memory_hotplug prevents a race with memory hotplug.
1407     * This is a big hammer, a better would be nicer.
1408     */
1409    lock_memory_hotplug();
1410
1411    /*
1412     * Isolate the page, so that it doesn't get reallocated if it
1413     * was free.
1414     */
1415    set_migratetype_isolate(p, true);
1416    /*
1417     * When the target page is a free hugepage, just remove it
1418     * from free hugepage list.
1419     */
1420    if (!get_page_unless_zero(compound_head(p))) {
1421        if (PageHuge(p)) {
1422            pr_info("%s: %#lx free huge page\n", __func__, pfn);
1423            ret = 0;
1424        } else if (is_free_buddy_page(p)) {
1425            pr_info("%s: %#lx free buddy page\n", __func__, pfn);
1426            ret = 0;
1427        } else {
1428            pr_info("%s: %#lx: unknown zero refcount page type %lx\n",
1429                __func__, pfn, p->flags);
1430            ret = -EIO;
1431        }
1432    } else {
1433        /* Not a free page */
1434        ret = 1;
1435    }
1436    unset_migratetype_isolate(p, MIGRATE_MOVABLE);
1437    unlock_memory_hotplug();
1438    return ret;
1439}
1440
1441static int get_any_page(struct page *page, unsigned long pfn, int flags)
1442{
1443    int ret = __get_any_page(page, pfn, flags);
1444
1445    if (ret == 1 && !PageHuge(page) && !PageLRU(page)) {
1446        /*
1447         * Try to free it.
1448         */
1449        put_page(page);
1450        shake_page(page, 1);
1451
1452        /*
1453         * Did it turn free?
1454         */
1455        ret = __get_any_page(page, pfn, 0);
1456        if (!PageLRU(page)) {
1457            pr_info("soft_offline: %#lx: unknown non LRU page type %lx\n",
1458                pfn, page->flags);
1459            return -EIO;
1460        }
1461    }
1462    return ret;
1463}
1464
1465static int soft_offline_huge_page(struct page *page, int flags)
1466{
1467    int ret;
1468    unsigned long pfn = page_to_pfn(page);
1469    struct page *hpage = compound_head(page);
1470
1471    /*
1472     * This double-check of PageHWPoison is to avoid the race with
1473     * memory_failure(). See also comment in __soft_offline_page().
1474     */
1475    lock_page(hpage);
1476    if (PageHWPoison(hpage)) {
1477        unlock_page(hpage);
1478        put_page(hpage);
1479        pr_info("soft offline: %#lx hugepage already poisoned\n", pfn);
1480        return -EBUSY;
1481    }
1482    unlock_page(hpage);
1483
1484    /* Keep page count to indicate a given hugepage is isolated. */
1485    ret = migrate_huge_page(hpage, new_page, MPOL_MF_MOVE_ALL,
1486                MIGRATE_SYNC);
1487    put_page(hpage);
1488    if (ret) {
1489        pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
1490            pfn, ret, page->flags);
1491    } else {
1492        set_page_hwpoison_huge_page(hpage);
1493        dequeue_hwpoisoned_huge_page(hpage);
1494        atomic_long_add(1 << compound_trans_order(hpage),
1495                &num_poisoned_pages);
1496    }
1497    /* keep elevated page count for bad page */
1498    return ret;
1499}
1500
1501static int __soft_offline_page(struct page *page, int flags);
1502
1503/**
1504 * soft_offline_page - Soft offline a page.
1505 * @page: page to offline
1506 * @flags: flags. Same as memory_failure().
1507 *
1508 * Returns 0 on success, otherwise negated errno.
1509 *
1510 * Soft offline a page, by migration or invalidation,
1511 * without killing anything. This is for the case when
1512 * a page is not corrupted yet (so it's still valid to access),
1513 * but has had a number of corrected errors and is better taken
1514 * out.
1515 *
1516 * The actual policy on when to do that is maintained by
1517 * user space.
1518 *
1519 * This should never impact any application or cause data loss,
1520 * however it might take some time.
1521 *
1522 * This is not a 100% solution for all memory, but tries to be
1523 * ``good enough'' for the majority of memory.
1524 */
1525int soft_offline_page(struct page *page, int flags)
1526{
1527    int ret;
1528    unsigned long pfn = page_to_pfn(page);
1529    struct page *hpage = compound_trans_head(page);
1530
1531    if (PageHWPoison(page)) {
1532        pr_info("soft offline: %#lx page already poisoned\n", pfn);
1533        return -EBUSY;
1534    }
1535    if (!PageHuge(page) && PageTransHuge(hpage)) {
1536        if (PageAnon(hpage) && unlikely(split_huge_page(hpage))) {
1537            pr_info("soft offline: %#lx: failed to split THP\n",
1538                pfn);
1539            return -EBUSY;
1540        }
1541    }
1542
1543    ret = get_any_page(page, pfn, flags);
1544    if (ret < 0)
1545        return ret;
1546    if (ret) { /* for in-use pages */
1547        if (PageHuge(page))
1548            ret = soft_offline_huge_page(page, flags);
1549        else
1550            ret = __soft_offline_page(page, flags);
1551    } else { /* for free pages */
1552        if (PageHuge(page)) {
1553            set_page_hwpoison_huge_page(hpage);
1554            dequeue_hwpoisoned_huge_page(hpage);
1555            atomic_long_add(1 << compound_trans_order(hpage),
1556                    &num_poisoned_pages);
1557        } else {
1558            SetPageHWPoison(page);
1559            atomic_long_inc(&num_poisoned_pages);
1560        }
1561    }
1562    /* keep elevated page count for bad page */
1563    return ret;
1564}
1565
1566static int __soft_offline_page(struct page *page, int flags)
1567{
1568    int ret;
1569    unsigned long pfn = page_to_pfn(page);
1570
1571    /*
1572     * Check PageHWPoison again inside page lock because PageHWPoison
1573     * is set by memory_failure() outside page lock. Note that
1574     * memory_failure() also double-checks PageHWPoison inside page lock,
1575     * so there's no race between soft_offline_page() and memory_failure().
1576     */
1577    lock_page(page);
1578    wait_on_page_writeback(page);
1579    if (PageHWPoison(page)) {
1580        unlock_page(page);
1581        put_page(page);
1582        pr_info("soft offline: %#lx page already poisoned\n", pfn);
1583        return -EBUSY;
1584    }
1585    /*
1586     * Try to invalidate first. This should work for
1587     * non dirty unmapped page cache pages.
1588     */
1589    ret = invalidate_inode_page(page);
1590    unlock_page(page);
1591    /*
1592     * RED-PEN would be better to keep it isolated here, but we
1593     * would need to fix isolation locking first.
1594     */
1595    if (ret == 1) {
1596        put_page(page);
1597        pr_info("soft_offline: %#lx: invalidated\n", pfn);
1598        SetPageHWPoison(page);
1599        atomic_long_inc(&num_poisoned_pages);
1600        return 0;
1601    }
1602
1603    /*
1604     * Simple invalidation didn't work.
1605     * Try to migrate to a new page instead. migrate.c
1606     * handles a large number of cases for us.
1607     */
1608    ret = isolate_lru_page(page);
1609    /*
1610     * Drop page reference which is came from get_any_page()
1611     * successful isolate_lru_page() already took another one.
1612     */
1613    put_page(page);
1614    if (!ret) {
1615        LIST_HEAD(pagelist);
1616        inc_zone_page_state(page, NR_ISOLATED_ANON +
1617                    page_is_file_cache(page));
1618        list_add(&page->lru, &pagelist);
1619        ret = migrate_pages(&pagelist, new_page, MPOL_MF_MOVE_ALL,
1620                    MIGRATE_SYNC, MR_MEMORY_FAILURE);
1621        if (ret) {
1622            putback_lru_pages(&pagelist);
1623            pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
1624                pfn, ret, page->flags);
1625            if (ret > 0)
1626                ret = -EIO;
1627        } else {
1628            SetPageHWPoison(page);
1629            atomic_long_inc(&num_poisoned_pages);
1630        }
1631    } else {
1632        pr_info("soft offline: %#lx: isolation failed: %d, page count %d, type %lx\n",
1633            pfn, ret, page_count(page), page->flags);
1634    }
1635    return ret;
1636}
1637

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