1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2008, 2009 Intel Corporation
4 * Authors: Andi Kleen, Fengguang Wu
5 *
6 * High level machine check handler. Handles pages reported by the
7 * hardware as being corrupted usually due to a multi-bit ECC memory or cache
8 * failure.
9 *
10 * In addition there is a "soft offline" entry point that allows stop using
11 * not-yet-corrupted-by-suspicious pages without killing anything.
12 *
13 * Handles page cache pages in various states. The tricky part
14 * here is that we can access any page asynchronously in respect to
15 * other VM users, because memory failures could happen anytime and
16 * anywhere. This could violate some of their assumptions. This is why
17 * this code has to be extremely careful. Generally it tries to use
18 * normal locking rules, as in get the standard locks, even if that means
19 * the error handling takes potentially a long time.
20 *
21 * It can be very tempting to add handling for obscure cases here.
22 * In general any code for handling new cases should only be added iff:
23 * - You know how to test it.
24 * - You have a test that can be added to mce-test
25 * https://git.kernel.org/cgit/utils/cpu/mce/mce-test.git/
26 * - The case actually shows up as a frequent (top 10) page state in
27 * tools/mm/page-types when running a real workload.
28 *
29 * There are several operations here with exponential complexity because
30 * of unsuitable VM data structures. For example the operation to map back
31 * from RMAP chains to processes has to walk the complete process list and
32 * has non linear complexity with the number. But since memory corruptions
33 * are rare we hope to get away with this. This avoids impacting the core
34 * VM.
35 */
36
37#define pr_fmt(fmt) "Memory failure: " fmt
38
39#include <linux/kernel.h>
40#include <linux/mm.h>
41#include <linux/page-flags.h>
42#include <linux/sched/signal.h>
43#include <linux/sched/task.h>
44#include <linux/dax.h>
45#include <linux/ksm.h>
46#include <linux/rmap.h>
47#include <linux/export.h>
48#include <linux/pagemap.h>
49#include <linux/swap.h>
50#include <linux/backing-dev.h>
51#include <linux/migrate.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/memremap.h>
58#include <linux/kfifo.h>
59#include <linux/ratelimit.h>
60#include <linux/pagewalk.h>
61#include <linux/shmem_fs.h>
62#include <linux/sysctl.h>
63#include "swap.h"
64#include "internal.h"
65#include "ras/ras_event.h"
66
67static int sysctl_memory_failure_early_kill __read_mostly;
68
69static int sysctl_memory_failure_recovery __read_mostly = 1;
70
71atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0);
72
73static bool hw_memory_failure __read_mostly = false;
74
75static DEFINE_MUTEX(mf_mutex);
76
77void num_poisoned_pages_inc(unsigned long pfn)
78{
79 atomic_long_inc(v: &num_poisoned_pages);
80 memblk_nr_poison_inc(pfn);
81}
82
83void num_poisoned_pages_sub(unsigned long pfn, long i)
84{
85 atomic_long_sub(i, v: &num_poisoned_pages);
86 if (pfn != -1UL)
87 memblk_nr_poison_sub(pfn, i);
88}
89
90/**
91 * MF_ATTR_RO - Create sysfs entry for each memory failure statistics.
92 * @_name: name of the file in the per NUMA sysfs directory.
93 */
94#define MF_ATTR_RO(_name) \
95static ssize_t _name##_show(struct device *dev, \
96 struct device_attribute *attr, \
97 char *buf) \
98{ \
99 struct memory_failure_stats *mf_stats = \
100 &NODE_DATA(dev->id)->mf_stats; \
101 return sprintf(buf, "%lu\n", mf_stats->_name); \
102} \
103static DEVICE_ATTR_RO(_name)
104
105MF_ATTR_RO(total);
106MF_ATTR_RO(ignored);
107MF_ATTR_RO(failed);
108MF_ATTR_RO(delayed);
109MF_ATTR_RO(recovered);
110
111static struct attribute *memory_failure_attr[] = {
112 &dev_attr_total.attr,
113 &dev_attr_ignored.attr,
114 &dev_attr_failed.attr,
115 &dev_attr_delayed.attr,
116 &dev_attr_recovered.attr,
117 NULL,
118};
119
120const struct attribute_group memory_failure_attr_group = {
121 .name = "memory_failure",
122 .attrs = memory_failure_attr,
123};
124
125static struct ctl_table memory_failure_table[] = {
126 {
127 .procname = "memory_failure_early_kill",
128 .data = &sysctl_memory_failure_early_kill,
129 .maxlen = sizeof(sysctl_memory_failure_early_kill),
130 .mode = 0644,
131 .proc_handler = proc_dointvec_minmax,
132 .extra1 = SYSCTL_ZERO,
133 .extra2 = SYSCTL_ONE,
134 },
135 {
136 .procname = "memory_failure_recovery",
137 .data = &sysctl_memory_failure_recovery,
138 .maxlen = sizeof(sysctl_memory_failure_recovery),
139 .mode = 0644,
140 .proc_handler = proc_dointvec_minmax,
141 .extra1 = SYSCTL_ZERO,
142 .extra2 = SYSCTL_ONE,
143 },
144 { }
145};
146
147/*
148 * Return values:
149 * 1: the page is dissolved (if needed) and taken off from buddy,
150 * 0: the page is dissolved (if needed) and not taken off from buddy,
151 * < 0: failed to dissolve.
152 */
153static int __page_handle_poison(struct page *page)
154{
155 int ret;
156
157 zone_pcp_disable(zone: page_zone(page));
158 ret = dissolve_free_huge_page(page);
159 if (!ret)
160 ret = take_page_off_buddy(page);
161 zone_pcp_enable(zone: page_zone(page));
162
163 return ret;
164}
165
166static bool page_handle_poison(struct page *page, bool hugepage_or_freepage, bool release)
167{
168 if (hugepage_or_freepage) {
169 /*
170 * Doing this check for free pages is also fine since dissolve_free_huge_page
171 * returns 0 for non-hugetlb pages as well.
172 */
173 if (__page_handle_poison(page) <= 0)
174 /*
175 * We could fail to take off the target page from buddy
176 * for example due to racy page allocation, but that's
177 * acceptable because soft-offlined page is not broken
178 * and if someone really want to use it, they should
179 * take it.
180 */
181 return false;
182 }
183
184 SetPageHWPoison(page);
185 if (release)
186 put_page(page);
187 page_ref_inc(page);
188 num_poisoned_pages_inc(page_to_pfn(page));
189
190 return true;
191}
192
193#if IS_ENABLED(CONFIG_HWPOISON_INJECT)
194
195u32 hwpoison_filter_enable = 0;
196u32 hwpoison_filter_dev_major = ~0U;
197u32 hwpoison_filter_dev_minor = ~0U;
198u64 hwpoison_filter_flags_mask;
199u64 hwpoison_filter_flags_value;
200EXPORT_SYMBOL_GPL(hwpoison_filter_enable);
201EXPORT_SYMBOL_GPL(hwpoison_filter_dev_major);
202EXPORT_SYMBOL_GPL(hwpoison_filter_dev_minor);
203EXPORT_SYMBOL_GPL(hwpoison_filter_flags_mask);
204EXPORT_SYMBOL_GPL(hwpoison_filter_flags_value);
205
206static int hwpoison_filter_dev(struct page *p)
207{
208 struct address_space *mapping;
209 dev_t dev;
210
211 if (hwpoison_filter_dev_major == ~0U &&
212 hwpoison_filter_dev_minor == ~0U)
213 return 0;
214
215 mapping = page_mapping(p);
216 if (mapping == NULL || mapping->host == NULL)
217 return -EINVAL;
218
219 dev = mapping->host->i_sb->s_dev;
220 if (hwpoison_filter_dev_major != ~0U &&
221 hwpoison_filter_dev_major != MAJOR(dev))
222 return -EINVAL;
223 if (hwpoison_filter_dev_minor != ~0U &&
224 hwpoison_filter_dev_minor != MINOR(dev))
225 return -EINVAL;
226
227 return 0;
228}
229
230static int hwpoison_filter_flags(struct page *p)
231{
232 if (!hwpoison_filter_flags_mask)
233 return 0;
234
235 if ((stable_page_flags(page: p) & hwpoison_filter_flags_mask) ==
236 hwpoison_filter_flags_value)
237 return 0;
238 else
239 return -EINVAL;
240}
241
242/*
243 * This allows stress tests to limit test scope to a collection of tasks
244 * by putting them under some memcg. This prevents killing unrelated/important
245 * processes such as /sbin/init. Note that the target task may share clean
246 * pages with init (eg. libc text), which is harmless. If the target task
247 * share _dirty_ pages with another task B, the test scheme must make sure B
248 * is also included in the memcg. At last, due to race conditions this filter
249 * can only guarantee that the page either belongs to the memcg tasks, or is
250 * a freed page.
251 */
252#ifdef CONFIG_MEMCG
253u64 hwpoison_filter_memcg;
254EXPORT_SYMBOL_GPL(hwpoison_filter_memcg);
255static int hwpoison_filter_task(struct page *p)
256{
257 if (!hwpoison_filter_memcg)
258 return 0;
259
260 if (page_cgroup_ino(page: p) != hwpoison_filter_memcg)
261 return -EINVAL;
262
263 return 0;
264}
265#else
266static int hwpoison_filter_task(struct page *p) { return 0; }
267#endif
268
269int hwpoison_filter(struct page *p)
270{
271 if (!hwpoison_filter_enable)
272 return 0;
273
274 if (hwpoison_filter_dev(p))
275 return -EINVAL;
276
277 if (hwpoison_filter_flags(p))
278 return -EINVAL;
279
280 if (hwpoison_filter_task(p))
281 return -EINVAL;
282
283 return 0;
284}
285#else
286int hwpoison_filter(struct page *p)
287{
288 return 0;
289}
290#endif
291
292EXPORT_SYMBOL_GPL(hwpoison_filter);
293
294/*
295 * Kill all processes that have a poisoned page mapped and then isolate
296 * the page.
297 *
298 * General strategy:
299 * Find all processes having the page mapped and kill them.
300 * But we keep a page reference around so that the page is not
301 * actually freed yet.
302 * Then stash the page away
303 *
304 * There's no convenient way to get back to mapped processes
305 * from the VMAs. So do a brute-force search over all
306 * running processes.
307 *
308 * Remember that machine checks are not common (or rather
309 * if they are common you have other problems), so this shouldn't
310 * be a performance issue.
311 *
312 * Also there are some races possible while we get from the
313 * error detection to actually handle it.
314 */
315
316struct to_kill {
317 struct list_head nd;
318 struct task_struct *tsk;
319 unsigned long addr;
320 short size_shift;
321};
322
323/*
324 * Send all the processes who have the page mapped a signal.
325 * ``action optional'' if they are not immediately affected by the error
326 * ``action required'' if error happened in current execution context
327 */
328static int kill_proc(struct to_kill *tk, unsigned long pfn, int flags)
329{
330 struct task_struct *t = tk->tsk;
331 short addr_lsb = tk->size_shift;
332 int ret = 0;
333
334 pr_err("%#lx: Sending SIGBUS to %s:%d due to hardware memory corruption\n",
335 pfn, t->comm, t->pid);
336
337 if ((flags & MF_ACTION_REQUIRED) && (t == current))
338 ret = force_sig_mceerr(BUS_MCEERR_AR,
339 (void __user *)tk->addr, addr_lsb);
340 else
341 /*
342 * Signal other processes sharing the page if they have
343 * PF_MCE_EARLY set.
344 * Don't use force here, it's convenient if the signal
345 * can be temporarily blocked.
346 * This could cause a loop when the user sets SIGBUS
347 * to SIG_IGN, but hopefully no one will do that?
348 */
349 ret = send_sig_mceerr(BUS_MCEERR_AO, (void __user *)tk->addr,
350 addr_lsb, t);
351 if (ret < 0)
352 pr_info("Error sending signal to %s:%d: %d\n",
353 t->comm, t->pid, ret);
354 return ret;
355}
356
357/*
358 * Unknown page type encountered. Try to check whether it can turn PageLRU by
359 * lru_add_drain_all.
360 */
361void shake_page(struct page *p)
362{
363 if (PageHuge(page: p))
364 return;
365 /*
366 * TODO: Could shrink slab caches here if a lightweight range-based
367 * shrinker will be available.
368 */
369 if (PageSlab(page: p))
370 return;
371
372 lru_add_drain_all();
373}
374EXPORT_SYMBOL_GPL(shake_page);
375
376static unsigned long dev_pagemap_mapping_shift(struct vm_area_struct *vma,
377 unsigned long address)
378{
379 unsigned long ret = 0;
380 pgd_t *pgd;
381 p4d_t *p4d;
382 pud_t *pud;
383 pmd_t *pmd;
384 pte_t *pte;
385 pte_t ptent;
386
387 VM_BUG_ON_VMA(address == -EFAULT, vma);
388 pgd = pgd_offset(vma->vm_mm, address);
389 if (!pgd_present(pgd: *pgd))
390 return 0;
391 p4d = p4d_offset(pgd, address);
392 if (!p4d_present(p4d: *p4d))
393 return 0;
394 pud = pud_offset(p4d, address);
395 if (!pud_present(pud: *pud))
396 return 0;
397 if (pud_devmap(pud: *pud))
398 return PUD_SHIFT;
399 pmd = pmd_offset(pud, address);
400 if (!pmd_present(pmd: *pmd))
401 return 0;
402 if (pmd_devmap(pmd: *pmd))
403 return PMD_SHIFT;
404 pte = pte_offset_map(pmd, addr: address);
405 if (!pte)
406 return 0;
407 ptent = ptep_get(ptep: pte);
408 if (pte_present(a: ptent) && pte_devmap(a: ptent))
409 ret = PAGE_SHIFT;
410 pte_unmap(pte);
411 return ret;
412}
413
414/*
415 * Failure handling: if we can't find or can't kill a process there's
416 * not much we can do. We just print a message and ignore otherwise.
417 */
418
419#define FSDAX_INVALID_PGOFF ULONG_MAX
420
421/*
422 * Schedule a process for later kill.
423 * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
424 *
425 * Note: @fsdax_pgoff is used only when @p is a fsdax page and a
426 * filesystem with a memory failure handler has claimed the
427 * memory_failure event. In all other cases, page->index and
428 * page->mapping are sufficient for mapping the page back to its
429 * corresponding user virtual address.
430 */
431static void __add_to_kill(struct task_struct *tsk, struct page *p,
432 struct vm_area_struct *vma, struct list_head *to_kill,
433 unsigned long ksm_addr, pgoff_t fsdax_pgoff)
434{
435 struct to_kill *tk;
436
437 tk = kmalloc(size: sizeof(struct to_kill), GFP_ATOMIC);
438 if (!tk) {
439 pr_err("Out of memory while machine check handling\n");
440 return;
441 }
442
443 tk->addr = ksm_addr ? ksm_addr : page_address_in_vma(p, vma);
444 if (is_zone_device_page(page: p)) {
445 if (fsdax_pgoff != FSDAX_INVALID_PGOFF)
446 tk->addr = vma_pgoff_address(pgoff: fsdax_pgoff, nr_pages: 1, vma);
447 tk->size_shift = dev_pagemap_mapping_shift(vma, address: tk->addr);
448 } else
449 tk->size_shift = page_shift(compound_head(p));
450
451 /*
452 * Send SIGKILL if "tk->addr == -EFAULT". Also, as
453 * "tk->size_shift" is always non-zero for !is_zone_device_page(),
454 * so "tk->size_shift == 0" effectively checks no mapping on
455 * ZONE_DEVICE. Indeed, when a devdax page is mmapped N times
456 * to a process' address space, it's possible not all N VMAs
457 * contain mappings for the page, but at least one VMA does.
458 * Only deliver SIGBUS with payload derived from the VMA that
459 * has a mapping for the page.
460 */
461 if (tk->addr == -EFAULT) {
462 pr_info("Unable to find user space address %lx in %s\n",
463 page_to_pfn(p), tsk->comm);
464 } else if (tk->size_shift == 0) {
465 kfree(objp: tk);
466 return;
467 }
468
469 get_task_struct(t: tsk);
470 tk->tsk = tsk;
471 list_add_tail(new: &tk->nd, head: to_kill);
472}
473
474static void add_to_kill_anon_file(struct task_struct *tsk, struct page *p,
475 struct vm_area_struct *vma,
476 struct list_head *to_kill)
477{
478 __add_to_kill(tsk, p, vma, to_kill, ksm_addr: 0, FSDAX_INVALID_PGOFF);
479}
480
481#ifdef CONFIG_KSM
482static bool task_in_to_kill_list(struct list_head *to_kill,
483 struct task_struct *tsk)
484{
485 struct to_kill *tk, *next;
486
487 list_for_each_entry_safe(tk, next, to_kill, nd) {
488 if (tk->tsk == tsk)
489 return true;
490 }
491
492 return false;
493}
494void add_to_kill_ksm(struct task_struct *tsk, struct page *p,
495 struct vm_area_struct *vma, struct list_head *to_kill,
496 unsigned long ksm_addr)
497{
498 if (!task_in_to_kill_list(to_kill, tsk))
499 __add_to_kill(tsk, p, vma, to_kill, ksm_addr, FSDAX_INVALID_PGOFF);
500}
501#endif
502/*
503 * Kill the processes that have been collected earlier.
504 *
505 * Only do anything when FORCEKILL is set, otherwise just free the
506 * list (this is used for clean pages which do not need killing)
507 * Also when FAIL is set do a force kill because something went
508 * wrong earlier.
509 */
510static void kill_procs(struct list_head *to_kill, int forcekill, bool fail,
511 unsigned long pfn, int flags)
512{
513 struct to_kill *tk, *next;
514
515 list_for_each_entry_safe(tk, next, to_kill, nd) {
516 if (forcekill) {
517 /*
518 * In case something went wrong with munmapping
519 * make sure the process doesn't catch the
520 * signal and then access the memory. Just kill it.
521 */
522 if (fail || tk->addr == -EFAULT) {
523 pr_err("%#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n",
524 pfn, tk->tsk->comm, tk->tsk->pid);
525 do_send_sig_info(SIGKILL, SEND_SIG_PRIV,
526 p: tk->tsk, type: PIDTYPE_PID);
527 }
528
529 /*
530 * In theory the process could have mapped
531 * something else on the address in-between. We could
532 * check for that, but we need to tell the
533 * process anyways.
534 */
535 else if (kill_proc(tk, pfn, flags) < 0)
536 pr_err("%#lx: Cannot send advisory machine check signal to %s:%d\n",
537 pfn, tk->tsk->comm, tk->tsk->pid);
538 }
539 list_del(entry: &tk->nd);
540 put_task_struct(t: tk->tsk);
541 kfree(objp: tk);
542 }
543}
544
545/*
546 * Find a dedicated thread which is supposed to handle SIGBUS(BUS_MCEERR_AO)
547 * on behalf of the thread group. Return task_struct of the (first found)
548 * dedicated thread if found, and return NULL otherwise.
549 *
550 * We already hold rcu lock in the caller, so we don't have to call
551 * rcu_read_lock/unlock() in this function.
552 */
553static struct task_struct *find_early_kill_thread(struct task_struct *tsk)
554{
555 struct task_struct *t;
556
557 for_each_thread(tsk, t) {
558 if (t->flags & PF_MCE_PROCESS) {
559 if (t->flags & PF_MCE_EARLY)
560 return t;
561 } else {
562 if (sysctl_memory_failure_early_kill)
563 return t;
564 }
565 }
566 return NULL;
567}
568
569/*
570 * Determine whether a given process is "early kill" process which expects
571 * to be signaled when some page under the process is hwpoisoned.
572 * Return task_struct of the dedicated thread (main thread unless explicitly
573 * specified) if the process is "early kill" and otherwise returns NULL.
574 *
575 * Note that the above is true for Action Optional case. For Action Required
576 * case, it's only meaningful to the current thread which need to be signaled
577 * with SIGBUS, this error is Action Optional for other non current
578 * processes sharing the same error page,if the process is "early kill", the
579 * task_struct of the dedicated thread will also be returned.
580 */
581struct task_struct *task_early_kill(struct task_struct *tsk, int force_early)
582{
583 if (!tsk->mm)
584 return NULL;
585 /*
586 * Comparing ->mm here because current task might represent
587 * a subthread, while tsk always points to the main thread.
588 */
589 if (force_early && tsk->mm == current->mm)
590 return current;
591
592 return find_early_kill_thread(tsk);
593}
594
595/*
596 * Collect processes when the error hit an anonymous page.
597 */
598static void collect_procs_anon(struct page *page, struct list_head *to_kill,
599 int force_early)
600{
601 struct folio *folio = page_folio(page);
602 struct vm_area_struct *vma;
603 struct task_struct *tsk;
604 struct anon_vma *av;
605 pgoff_t pgoff;
606
607 av = folio_lock_anon_vma_read(folio, NULL);
608 if (av == NULL) /* Not actually mapped anymore */
609 return;
610
611 pgoff = page_to_pgoff(page);
612 rcu_read_lock();
613 for_each_process(tsk) {
614 struct anon_vma_chain *vmac;
615 struct task_struct *t = task_early_kill(tsk, force_early);
616
617 if (!t)
618 continue;
619 anon_vma_interval_tree_foreach(vmac, &av->rb_root,
620 pgoff, pgoff) {
621 vma = vmac->vma;
622 if (vma->vm_mm != t->mm)
623 continue;
624 if (!page_mapped_in_vma(page, vma))
625 continue;
626 add_to_kill_anon_file(tsk: t, p: page, vma, to_kill);
627 }
628 }
629 rcu_read_unlock();
630 anon_vma_unlock_read(anon_vma: av);
631}
632
633/*
634 * Collect processes when the error hit a file mapped page.
635 */
636static void collect_procs_file(struct page *page, struct list_head *to_kill,
637 int force_early)
638{
639 struct vm_area_struct *vma;
640 struct task_struct *tsk;
641 struct address_space *mapping = page->mapping;
642 pgoff_t pgoff;
643
644 i_mmap_lock_read(mapping);
645 rcu_read_lock();
646 pgoff = page_to_pgoff(page);
647 for_each_process(tsk) {
648 struct task_struct *t = task_early_kill(tsk, force_early);
649
650 if (!t)
651 continue;
652 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff,
653 pgoff) {
654 /*
655 * Send early kill signal to tasks where a vma covers
656 * the page but the corrupted page is not necessarily
657 * mapped in its pte.
658 * Assume applications who requested early kill want
659 * to be informed of all such data corruptions.
660 */
661 if (vma->vm_mm == t->mm)
662 add_to_kill_anon_file(tsk: t, p: page, vma, to_kill);
663 }
664 }
665 rcu_read_unlock();
666 i_mmap_unlock_read(mapping);
667}
668
669#ifdef CONFIG_FS_DAX
670static void add_to_kill_fsdax(struct task_struct *tsk, struct page *p,
671 struct vm_area_struct *vma,
672 struct list_head *to_kill, pgoff_t pgoff)
673{
674 __add_to_kill(tsk, p, vma, to_kill, ksm_addr: 0, fsdax_pgoff: pgoff);
675}
676
677/*
678 * Collect processes when the error hit a fsdax page.
679 */
680static void collect_procs_fsdax(struct page *page,
681 struct address_space *mapping, pgoff_t pgoff,
682 struct list_head *to_kill)
683{
684 struct vm_area_struct *vma;
685 struct task_struct *tsk;
686
687 i_mmap_lock_read(mapping);
688 rcu_read_lock();
689 for_each_process(tsk) {
690 struct task_struct *t = task_early_kill(tsk, force_early: true);
691
692 if (!t)
693 continue;
694 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
695 if (vma->vm_mm == t->mm)
696 add_to_kill_fsdax(tsk: t, p: page, vma, to_kill, pgoff);
697 }
698 }
699 rcu_read_unlock();
700 i_mmap_unlock_read(mapping);
701}
702#endif /* CONFIG_FS_DAX */
703
704/*
705 * Collect the processes who have the corrupted page mapped to kill.
706 */
707static void collect_procs(struct page *page, struct list_head *tokill,
708 int force_early)
709{
710 if (!page->mapping)
711 return;
712 if (unlikely(PageKsm(page)))
713 collect_procs_ksm(page, to_kill: tokill, force_early);
714 else if (PageAnon(page))
715 collect_procs_anon(page, to_kill: tokill, force_early);
716 else
717 collect_procs_file(page, to_kill: tokill, force_early);
718}
719
720struct hwpoison_walk {
721 struct to_kill tk;
722 unsigned long pfn;
723 int flags;
724};
725
726static void set_to_kill(struct to_kill *tk, unsigned long addr, short shift)
727{
728 tk->addr = addr;
729 tk->size_shift = shift;
730}
731
732static int check_hwpoisoned_entry(pte_t pte, unsigned long addr, short shift,
733 unsigned long poisoned_pfn, struct to_kill *tk)
734{
735 unsigned long pfn = 0;
736
737 if (pte_present(a: pte)) {
738 pfn = pte_pfn(pte);
739 } else {
740 swp_entry_t swp = pte_to_swp_entry(pte);
741
742 if (is_hwpoison_entry(entry: swp))
743 pfn = swp_offset_pfn(entry: swp);
744 }
745
746 if (!pfn || pfn != poisoned_pfn)
747 return 0;
748
749 set_to_kill(tk, addr, shift);
750 return 1;
751}
752
753#ifdef CONFIG_TRANSPARENT_HUGEPAGE
754static int check_hwpoisoned_pmd_entry(pmd_t *pmdp, unsigned long addr,
755 struct hwpoison_walk *hwp)
756{
757 pmd_t pmd = *pmdp;
758 unsigned long pfn;
759 unsigned long hwpoison_vaddr;
760
761 if (!pmd_present(pmd))
762 return 0;
763 pfn = pmd_pfn(pmd);
764 if (pfn <= hwp->pfn && hwp->pfn < pfn + HPAGE_PMD_NR) {
765 hwpoison_vaddr = addr + ((hwp->pfn - pfn) << PAGE_SHIFT);
766 set_to_kill(tk: &hwp->tk, addr: hwpoison_vaddr, PAGE_SHIFT);
767 return 1;
768 }
769 return 0;
770}
771#else
772static int check_hwpoisoned_pmd_entry(pmd_t *pmdp, unsigned long addr,
773 struct hwpoison_walk *hwp)
774{
775 return 0;
776}
777#endif
778
779static int hwpoison_pte_range(pmd_t *pmdp, unsigned long addr,
780 unsigned long end, struct mm_walk *walk)
781{
782 struct hwpoison_walk *hwp = walk->private;
783 int ret = 0;
784 pte_t *ptep, *mapped_pte;
785 spinlock_t *ptl;
786
787 ptl = pmd_trans_huge_lock(pmd: pmdp, vma: walk->vma);
788 if (ptl) {
789 ret = check_hwpoisoned_pmd_entry(pmdp, addr, hwp);
790 spin_unlock(lock: ptl);
791 goto out;
792 }
793
794 mapped_pte = ptep = pte_offset_map_lock(mm: walk->vma->vm_mm, pmd: pmdp,
795 addr, ptlp: &ptl);
796 if (!ptep)
797 goto out;
798
799 for (; addr != end; ptep++, addr += PAGE_SIZE) {
800 ret = check_hwpoisoned_entry(pte: ptep_get(ptep), addr, PAGE_SHIFT,
801 poisoned_pfn: hwp->pfn, tk: &hwp->tk);
802 if (ret == 1)
803 break;
804 }
805 pte_unmap_unlock(mapped_pte, ptl);
806out:
807 cond_resched();
808 return ret;
809}
810
811#ifdef CONFIG_HUGETLB_PAGE
812static int hwpoison_hugetlb_range(pte_t *ptep, unsigned long hmask,
813 unsigned long addr, unsigned long end,
814 struct mm_walk *walk)
815{
816 struct hwpoison_walk *hwp = walk->private;
817 pte_t pte = huge_ptep_get(ptep);
818 struct hstate *h = hstate_vma(vma: walk->vma);
819
820 return check_hwpoisoned_entry(pte, addr, shift: huge_page_shift(h),
821 poisoned_pfn: hwp->pfn, tk: &hwp->tk);
822}
823#else
824#define hwpoison_hugetlb_range NULL
825#endif
826
827static const struct mm_walk_ops hwpoison_walk_ops = {
828 .pmd_entry = hwpoison_pte_range,
829 .hugetlb_entry = hwpoison_hugetlb_range,
830 .walk_lock = PGWALK_RDLOCK,
831};
832
833/*
834 * Sends SIGBUS to the current process with error info.
835 *
836 * This function is intended to handle "Action Required" MCEs on already
837 * hardware poisoned pages. They could happen, for example, when
838 * memory_failure() failed to unmap the error page at the first call, or
839 * when multiple local machine checks happened on different CPUs.
840 *
841 * MCE handler currently has no easy access to the error virtual address,
842 * so this function walks page table to find it. The returned virtual address
843 * is proper in most cases, but it could be wrong when the application
844 * process has multiple entries mapping the error page.
845 */
846static int kill_accessing_process(struct task_struct *p, unsigned long pfn,
847 int flags)
848{
849 int ret;
850 struct hwpoison_walk priv = {
851 .pfn = pfn,
852 };
853 priv.tk.tsk = p;
854
855 if (!p->mm)
856 return -EFAULT;
857
858 mmap_read_lock(mm: p->mm);
859 ret = walk_page_range(mm: p->mm, start: 0, TASK_SIZE, ops: &hwpoison_walk_ops,
860 private: (void *)&priv);
861 if (ret == 1 && priv.tk.addr)
862 kill_proc(tk: &priv.tk, pfn, flags);
863 else
864 ret = 0;
865 mmap_read_unlock(mm: p->mm);
866 return ret > 0 ? -EHWPOISON : -EFAULT;
867}
868
869static const char *action_name[] = {
870 [MF_IGNORED] = "Ignored",
871 [MF_FAILED] = "Failed",
872 [MF_DELAYED] = "Delayed",
873 [MF_RECOVERED] = "Recovered",
874};
875
876static const char * const action_page_types[] = {
877 [MF_MSG_KERNEL] = "reserved kernel page",
878 [MF_MSG_KERNEL_HIGH_ORDER] = "high-order kernel page",
879 [MF_MSG_SLAB] = "kernel slab page",
880 [MF_MSG_DIFFERENT_COMPOUND] = "different compound page after locking",
881 [MF_MSG_HUGE] = "huge page",
882 [MF_MSG_FREE_HUGE] = "free huge page",
883 [MF_MSG_UNMAP_FAILED] = "unmapping failed page",
884 [MF_MSG_DIRTY_SWAPCACHE] = "dirty swapcache page",
885 [MF_MSG_CLEAN_SWAPCACHE] = "clean swapcache page",
886 [MF_MSG_DIRTY_MLOCKED_LRU] = "dirty mlocked LRU page",
887 [MF_MSG_CLEAN_MLOCKED_LRU] = "clean mlocked LRU page",
888 [MF_MSG_DIRTY_UNEVICTABLE_LRU] = "dirty unevictable LRU page",
889 [MF_MSG_CLEAN_UNEVICTABLE_LRU] = "clean unevictable LRU page",
890 [MF_MSG_DIRTY_LRU] = "dirty LRU page",
891 [MF_MSG_CLEAN_LRU] = "clean LRU page",
892 [MF_MSG_TRUNCATED_LRU] = "already truncated LRU page",
893 [MF_MSG_BUDDY] = "free buddy page",
894 [MF_MSG_DAX] = "dax page",
895 [MF_MSG_UNSPLIT_THP] = "unsplit thp",
896 [MF_MSG_UNKNOWN] = "unknown page",
897};
898
899/*
900 * XXX: It is possible that a page is isolated from LRU cache,
901 * and then kept in swap cache or failed to remove from page cache.
902 * The page count will stop it from being freed by unpoison.
903 * Stress tests should be aware of this memory leak problem.
904 */
905static int delete_from_lru_cache(struct page *p)
906{
907 if (isolate_lru_page(page: p)) {
908 /*
909 * Clear sensible page flags, so that the buddy system won't
910 * complain when the page is unpoison-and-freed.
911 */
912 ClearPageActive(page: p);
913 ClearPageUnevictable(page: p);
914
915 /*
916 * Poisoned page might never drop its ref count to 0 so we have
917 * to uncharge it manually from its memcg.
918 */
919 mem_cgroup_uncharge(page_folio(p));
920
921 /*
922 * drop the page count elevated by isolate_lru_page()
923 */
924 put_page(page: p);
925 return 0;
926 }
927 return -EIO;
928}
929
930static int truncate_error_page(struct page *p, unsigned long pfn,
931 struct address_space *mapping)
932{
933 int ret = MF_FAILED;
934
935 if (mapping->a_ops->error_remove_page) {
936 struct folio *folio = page_folio(p);
937 int err = mapping->a_ops->error_remove_page(mapping, p);
938
939 if (err != 0)
940 pr_info("%#lx: Failed to punch page: %d\n", pfn, err);
941 else if (!filemap_release_folio(folio, GFP_NOIO))
942 pr_info("%#lx: failed to release buffers\n", pfn);
943 else
944 ret = MF_RECOVERED;
945 } else {
946 /*
947 * If the file system doesn't support it just invalidate
948 * This fails on dirty or anything with private pages
949 */
950 if (invalidate_inode_page(page: p))
951 ret = MF_RECOVERED;
952 else
953 pr_info("%#lx: Failed to invalidate\n", pfn);
954 }
955
956 return ret;
957}
958
959struct page_state {
960 unsigned long mask;
961 unsigned long res;
962 enum mf_action_page_type type;
963
964 /* Callback ->action() has to unlock the relevant page inside it. */
965 int (*action)(struct page_state *ps, struct page *p);
966};
967
968/*
969 * Return true if page is still referenced by others, otherwise return
970 * false.
971 *
972 * The extra_pins is true when one extra refcount is expected.
973 */
974static bool has_extra_refcount(struct page_state *ps, struct page *p,
975 bool extra_pins)
976{
977 int count = page_count(page: p) - 1;
978
979 if (extra_pins)
980 count -= 1;
981
982 if (count > 0) {
983 pr_err("%#lx: %s still referenced by %d users\n",
984 page_to_pfn(p), action_page_types[ps->type], count);
985 return true;
986 }
987
988 return false;
989}
990
991/*
992 * Error hit kernel page.
993 * Do nothing, try to be lucky and not touch this instead. For a few cases we
994 * could be more sophisticated.
995 */
996static int me_kernel(struct page_state *ps, struct page *p)
997{
998 unlock_page(page: p);
999 return MF_IGNORED;
1000}
1001
1002/*
1003 * Page in unknown state. Do nothing.
1004 */
1005static int me_unknown(struct page_state *ps, struct page *p)
1006{
1007 pr_err("%#lx: Unknown page state\n", page_to_pfn(p));
1008 unlock_page(page: p);
1009 return MF_FAILED;
1010}
1011
1012/*
1013 * Clean (or cleaned) page cache page.
1014 */
1015static int me_pagecache_clean(struct page_state *ps, struct page *p)
1016{
1017 int ret;
1018 struct address_space *mapping;
1019 bool extra_pins;
1020
1021 delete_from_lru_cache(p);
1022
1023 /*
1024 * For anonymous pages we're done the only reference left
1025 * should be the one m_f() holds.
1026 */
1027 if (PageAnon(page: p)) {
1028 ret = MF_RECOVERED;
1029 goto out;
1030 }
1031
1032 /*
1033 * Now truncate the page in the page cache. This is really
1034 * more like a "temporary hole punch"
1035 * Don't do this for block devices when someone else
1036 * has a reference, because it could be file system metadata
1037 * and that's not safe to truncate.
1038 */
1039 mapping = page_mapping(p);
1040 if (!mapping) {
1041 /*
1042 * Page has been teared down in the meanwhile
1043 */
1044 ret = MF_FAILED;
1045 goto out;
1046 }
1047
1048 /*
1049 * The shmem page is kept in page cache instead of truncating
1050 * so is expected to have an extra refcount after error-handling.
1051 */
1052 extra_pins = shmem_mapping(mapping);
1053
1054 /*
1055 * Truncation is a bit tricky. Enable it per file system for now.
1056 *
1057 * Open: to take i_rwsem or not for this? Right now we don't.
1058 */
1059 ret = truncate_error_page(p, page_to_pfn(p), mapping);
1060 if (has_extra_refcount(ps, p, extra_pins))
1061 ret = MF_FAILED;
1062
1063out:
1064 unlock_page(page: p);
1065
1066 return ret;
1067}
1068
1069/*
1070 * Dirty pagecache page
1071 * Issues: when the error hit a hole page the error is not properly
1072 * propagated.
1073 */
1074static int me_pagecache_dirty(struct page_state *ps, struct page *p)
1075{
1076 struct address_space *mapping = page_mapping(p);
1077
1078 SetPageError(p);
1079 /* TBD: print more information about the file. */
1080 if (mapping) {
1081 /*
1082 * IO error will be reported by write(), fsync(), etc.
1083 * who check the mapping.
1084 * This way the application knows that something went
1085 * wrong with its dirty file data.
1086 *
1087 * There's one open issue:
1088 *
1089 * The EIO will be only reported on the next IO
1090 * operation and then cleared through the IO map.
1091 * Normally Linux has two mechanisms to pass IO error
1092 * first through the AS_EIO flag in the address space
1093 * and then through the PageError flag in the page.
1094 * Since we drop pages on memory failure handling the
1095 * only mechanism open to use is through AS_AIO.
1096 *
1097 * This has the disadvantage that it gets cleared on
1098 * the first operation that returns an error, while
1099 * the PageError bit is more sticky and only cleared
1100 * when the page is reread or dropped. If an
1101 * application assumes it will always get error on
1102 * fsync, but does other operations on the fd before
1103 * and the page is dropped between then the error
1104 * will not be properly reported.
1105 *
1106 * This can already happen even without hwpoisoned
1107 * pages: first on metadata IO errors (which only
1108 * report through AS_EIO) or when the page is dropped
1109 * at the wrong time.
1110 *
1111 * So right now we assume that the application DTRT on
1112 * the first EIO, but we're not worse than other parts
1113 * of the kernel.
1114 */
1115 mapping_set_error(mapping, error: -EIO);
1116 }
1117
1118 return me_pagecache_clean(ps, p);
1119}
1120
1121/*
1122 * Clean and dirty swap cache.
1123 *
1124 * Dirty swap cache page is tricky to handle. The page could live both in page
1125 * cache and swap cache(ie. page is freshly swapped in). So it could be
1126 * referenced concurrently by 2 types of PTEs:
1127 * normal PTEs and swap PTEs. We try to handle them consistently by calling
1128 * try_to_unmap(!TTU_HWPOISON) to convert the normal PTEs to swap PTEs,
1129 * and then
1130 * - clear dirty bit to prevent IO
1131 * - remove from LRU
1132 * - but keep in the swap cache, so that when we return to it on
1133 * a later page fault, we know the application is accessing
1134 * corrupted data and shall be killed (we installed simple
1135 * interception code in do_swap_page to catch it).
1136 *
1137 * Clean swap cache pages can be directly isolated. A later page fault will
1138 * bring in the known good data from disk.
1139 */
1140static int me_swapcache_dirty(struct page_state *ps, struct page *p)
1141{
1142 int ret;
1143 bool extra_pins = false;
1144
1145 ClearPageDirty(page: p);
1146 /* Trigger EIO in shmem: */
1147 ClearPageUptodate(page: p);
1148
1149 ret = delete_from_lru_cache(p) ? MF_FAILED : MF_DELAYED;
1150 unlock_page(page: p);
1151
1152 if (ret == MF_DELAYED)
1153 extra_pins = true;
1154
1155 if (has_extra_refcount(ps, p, extra_pins))
1156 ret = MF_FAILED;
1157
1158 return ret;
1159}
1160
1161static int me_swapcache_clean(struct page_state *ps, struct page *p)
1162{
1163 struct folio *folio = page_folio(p);
1164 int ret;
1165
1166 delete_from_swap_cache(folio);
1167
1168 ret = delete_from_lru_cache(p) ? MF_FAILED : MF_RECOVERED;
1169 folio_unlock(folio);
1170
1171 if (has_extra_refcount(ps, p, extra_pins: false))
1172 ret = MF_FAILED;
1173
1174 return ret;
1175}
1176
1177/*
1178 * Huge pages. Needs work.
1179 * Issues:
1180 * - Error on hugepage is contained in hugepage unit (not in raw page unit.)
1181 * To narrow down kill region to one page, we need to break up pmd.
1182 */
1183static int me_huge_page(struct page_state *ps, struct page *p)
1184{
1185 int res;
1186 struct page *hpage = compound_head(p);
1187 struct address_space *mapping;
1188 bool extra_pins = false;
1189
1190 mapping = page_mapping(hpage);
1191 if (mapping) {
1192 res = truncate_error_page(p: hpage, page_to_pfn(p), mapping);
1193 /* The page is kept in page cache. */
1194 extra_pins = true;
1195 unlock_page(page: hpage);
1196 } else {
1197 unlock_page(page: hpage);
1198 /*
1199 * migration entry prevents later access on error hugepage,
1200 * so we can free and dissolve it into buddy to save healthy
1201 * subpages.
1202 */
1203 put_page(page: hpage);
1204 if (__page_handle_poison(page: p) >= 0) {
1205 page_ref_inc(page: p);
1206 res = MF_RECOVERED;
1207 } else {
1208 res = MF_FAILED;
1209 }
1210 }
1211
1212 if (has_extra_refcount(ps, p, extra_pins))
1213 res = MF_FAILED;
1214
1215 return res;
1216}
1217
1218/*
1219 * Various page states we can handle.
1220 *
1221 * A page state is defined by its current page->flags bits.
1222 * The table matches them in order and calls the right handler.
1223 *
1224 * This is quite tricky because we can access page at any time
1225 * in its live cycle, so all accesses have to be extremely careful.
1226 *
1227 * This is not complete. More states could be added.
1228 * For any missing state don't attempt recovery.
1229 */
1230
1231#define dirty (1UL << PG_dirty)
1232#define sc ((1UL << PG_swapcache) | (1UL << PG_swapbacked))
1233#define unevict (1UL << PG_unevictable)
1234#define mlock (1UL << PG_mlocked)
1235#define lru (1UL << PG_lru)
1236#define head (1UL << PG_head)
1237#define slab (1UL << PG_slab)
1238#define reserved (1UL << PG_reserved)
1239
1240static struct page_state error_states[] = {
1241 { reserved, reserved, MF_MSG_KERNEL, me_kernel },
1242 /*
1243 * free pages are specially detected outside this table:
1244 * PG_buddy pages only make a small fraction of all free pages.
1245 */
1246
1247 /*
1248 * Could in theory check if slab page is free or if we can drop
1249 * currently unused objects without touching them. But just
1250 * treat it as standard kernel for now.
1251 */
1252 { slab, slab, MF_MSG_SLAB, me_kernel },
1253
1254 { head, head, MF_MSG_HUGE, me_huge_page },
1255
1256 { sc|dirty, sc|dirty, MF_MSG_DIRTY_SWAPCACHE, me_swapcache_dirty },
1257 { sc|dirty, sc, MF_MSG_CLEAN_SWAPCACHE, me_swapcache_clean },
1258
1259 { mlock|dirty, mlock|dirty, MF_MSG_DIRTY_MLOCKED_LRU, me_pagecache_dirty },
1260 { mlock|dirty, mlock, MF_MSG_CLEAN_MLOCKED_LRU, me_pagecache_clean },
1261
1262 { unevict|dirty, unevict|dirty, MF_MSG_DIRTY_UNEVICTABLE_LRU, me_pagecache_dirty },
1263 { unevict|dirty, unevict, MF_MSG_CLEAN_UNEVICTABLE_LRU, me_pagecache_clean },
1264
1265 { lru|dirty, lru|dirty, MF_MSG_DIRTY_LRU, me_pagecache_dirty },
1266 { lru|dirty, lru, MF_MSG_CLEAN_LRU, me_pagecache_clean },
1267
1268 /*
1269 * Catchall entry: must be at end.
1270 */
1271 { 0, 0, MF_MSG_UNKNOWN, me_unknown },
1272};
1273
1274#undef dirty
1275#undef sc
1276#undef unevict
1277#undef mlock
1278#undef lru
1279#undef head
1280#undef slab
1281#undef reserved
1282
1283static void update_per_node_mf_stats(unsigned long pfn,
1284 enum mf_result result)
1285{
1286 int nid = MAX_NUMNODES;
1287 struct memory_failure_stats *mf_stats = NULL;
1288
1289 nid = pfn_to_nid(pfn);
1290 if (unlikely(nid < 0 || nid >= MAX_NUMNODES)) {
1291 WARN_ONCE(1, "Memory failure: pfn=%#lx, invalid nid=%d", pfn, nid);
1292 return;
1293 }
1294
1295 mf_stats = &NODE_DATA(nid)->mf_stats;
1296 switch (result) {
1297 case MF_IGNORED:
1298 ++mf_stats->ignored;
1299 break;
1300 case MF_FAILED:
1301 ++mf_stats->failed;
1302 break;
1303 case MF_DELAYED:
1304 ++mf_stats->delayed;
1305 break;
1306 case MF_RECOVERED:
1307 ++mf_stats->recovered;
1308 break;
1309 default:
1310 WARN_ONCE(1, "Memory failure: mf_result=%d is not properly handled", result);
1311 break;
1312 }
1313 ++mf_stats->total;
1314}
1315
1316/*
1317 * "Dirty/Clean" indication is not 100% accurate due to the possibility of
1318 * setting PG_dirty outside page lock. See also comment above set_page_dirty().
1319 */
1320static int action_result(unsigned long pfn, enum mf_action_page_type type,
1321 enum mf_result result)
1322{
1323 trace_memory_failure_event(pfn, type, result);
1324
1325 num_poisoned_pages_inc(pfn);
1326
1327 update_per_node_mf_stats(pfn, result);
1328
1329 pr_err("%#lx: recovery action for %s: %s\n",
1330 pfn, action_page_types[type], action_name[result]);
1331
1332 return (result == MF_RECOVERED || result == MF_DELAYED) ? 0 : -EBUSY;
1333}
1334
1335static int page_action(struct page_state *ps, struct page *p,
1336 unsigned long pfn)
1337{
1338 int result;
1339
1340 /* page p should be unlocked after returning from ps->action(). */
1341 result = ps->action(ps, p);
1342
1343 /* Could do more checks here if page looks ok */
1344 /*
1345 * Could adjust zone counters here to correct for the missing page.
1346 */
1347
1348 return action_result(pfn, type: ps->type, result);
1349}
1350
1351static inline bool PageHWPoisonTakenOff(struct page *page)
1352{
1353 return PageHWPoison(page) && page_private(page) == MAGIC_HWPOISON;
1354}
1355
1356void SetPageHWPoisonTakenOff(struct page *page)
1357{
1358 set_page_private(page, MAGIC_HWPOISON);
1359}
1360
1361void ClearPageHWPoisonTakenOff(struct page *page)
1362{
1363 if (PageHWPoison(page))
1364 set_page_private(page, private: 0);
1365}
1366
1367/*
1368 * Return true if a page type of a given page is supported by hwpoison
1369 * mechanism (while handling could fail), otherwise false. This function
1370 * does not return true for hugetlb or device memory pages, so it's assumed
1371 * to be called only in the context where we never have such pages.
1372 */
1373static inline bool HWPoisonHandlable(struct page *page, unsigned long flags)
1374{
1375 /* Soft offline could migrate non-LRU movable pages */
1376 if ((flags & MF_SOFT_OFFLINE) && __PageMovable(page))
1377 return true;
1378
1379 return PageLRU(page) || is_free_buddy_page(page);
1380}
1381
1382static int __get_hwpoison_page(struct page *page, unsigned long flags)
1383{
1384 struct folio *folio = page_folio(page);
1385 int ret = 0;
1386 bool hugetlb = false;
1387
1388 ret = get_hwpoison_hugetlb_folio(folio, hugetlb: &hugetlb, unpoison: false);
1389 if (hugetlb) {
1390 /* Make sure hugetlb demotion did not happen from under us. */
1391 if (folio == page_folio(page))
1392 return ret;
1393 if (ret > 0) {
1394 folio_put(folio);
1395 folio = page_folio(page);
1396 }
1397 }
1398
1399 /*
1400 * This check prevents from calling folio_try_get() for any
1401 * unsupported type of folio in order to reduce the risk of unexpected
1402 * races caused by taking a folio refcount.
1403 */
1404 if (!HWPoisonHandlable(page: &folio->page, flags))
1405 return -EBUSY;
1406
1407 if (folio_try_get(folio)) {
1408 if (folio == page_folio(page))
1409 return 1;
1410
1411 pr_info("%#lx cannot catch tail\n", page_to_pfn(page));
1412 folio_put(folio);
1413 }
1414
1415 return 0;
1416}
1417
1418static int get_any_page(struct page *p, unsigned long flags)
1419{
1420 int ret = 0, pass = 0;
1421 bool count_increased = false;
1422
1423 if (flags & MF_COUNT_INCREASED)
1424 count_increased = true;
1425
1426try_again:
1427 if (!count_increased) {
1428 ret = __get_hwpoison_page(page: p, flags);
1429 if (!ret) {
1430 if (page_count(page: p)) {
1431 /* We raced with an allocation, retry. */
1432 if (pass++ < 3)
1433 goto try_again;
1434 ret = -EBUSY;
1435 } else if (!PageHuge(page: p) && !is_free_buddy_page(page: p)) {
1436 /* We raced with put_page, retry. */
1437 if (pass++ < 3)
1438 goto try_again;
1439 ret = -EIO;
1440 }
1441 goto out;
1442 } else if (ret == -EBUSY) {
1443 /*
1444 * We raced with (possibly temporary) unhandlable
1445 * page, retry.
1446 */
1447 if (pass++ < 3) {
1448 shake_page(p);
1449 goto try_again;
1450 }
1451 ret = -EIO;
1452 goto out;
1453 }
1454 }
1455
1456 if (PageHuge(page: p) || HWPoisonHandlable(page: p, flags)) {
1457 ret = 1;
1458 } else {
1459 /*
1460 * A page we cannot handle. Check whether we can turn
1461 * it into something we can handle.
1462 */
1463 if (pass++ < 3) {
1464 put_page(page: p);
1465 shake_page(p);
1466 count_increased = false;
1467 goto try_again;
1468 }
1469 put_page(page: p);
1470 ret = -EIO;
1471 }
1472out:
1473 if (ret == -EIO)
1474 pr_err("%#lx: unhandlable page.\n", page_to_pfn(p));
1475
1476 return ret;
1477}
1478
1479static int __get_unpoison_page(struct page *page)
1480{
1481 struct folio *folio = page_folio(page);
1482 int ret = 0;
1483 bool hugetlb = false;
1484
1485 ret = get_hwpoison_hugetlb_folio(folio, hugetlb: &hugetlb, unpoison: true);
1486 if (hugetlb) {
1487 /* Make sure hugetlb demotion did not happen from under us. */
1488 if (folio == page_folio(page))
1489 return ret;
1490 if (ret > 0)
1491 folio_put(folio);
1492 }
1493
1494 /*
1495 * PageHWPoisonTakenOff pages are not only marked as PG_hwpoison,
1496 * but also isolated from buddy freelist, so need to identify the
1497 * state and have to cancel both operations to unpoison.
1498 */
1499 if (PageHWPoisonTakenOff(page))
1500 return -EHWPOISON;
1501
1502 return get_page_unless_zero(page) ? 1 : 0;
1503}
1504
1505/**
1506 * get_hwpoison_page() - Get refcount for memory error handling
1507 * @p: Raw error page (hit by memory error)
1508 * @flags: Flags controlling behavior of error handling
1509 *
1510 * get_hwpoison_page() takes a page refcount of an error page to handle memory
1511 * error on it, after checking that the error page is in a well-defined state
1512 * (defined as a page-type we can successfully handle the memory error on it,
1513 * such as LRU page and hugetlb page).
1514 *
1515 * Memory error handling could be triggered at any time on any type of page,
1516 * so it's prone to race with typical memory management lifecycle (like
1517 * allocation and free). So to avoid such races, get_hwpoison_page() takes
1518 * extra care for the error page's state (as done in __get_hwpoison_page()),
1519 * and has some retry logic in get_any_page().
1520 *
1521 * When called from unpoison_memory(), the caller should already ensure that
1522 * the given page has PG_hwpoison. So it's never reused for other page
1523 * allocations, and __get_unpoison_page() never races with them.
1524 *
1525 * Return: 0 on failure,
1526 * 1 on success for in-use pages in a well-defined state,
1527 * -EIO for pages on which we can not handle memory errors,
1528 * -EBUSY when get_hwpoison_page() has raced with page lifecycle
1529 * operations like allocation and free,
1530 * -EHWPOISON when the page is hwpoisoned and taken off from buddy.
1531 */
1532static int get_hwpoison_page(struct page *p, unsigned long flags)
1533{
1534 int ret;
1535
1536 zone_pcp_disable(zone: page_zone(page: p));
1537 if (flags & MF_UNPOISON)
1538 ret = __get_unpoison_page(page: p);
1539 else
1540 ret = get_any_page(p, flags);
1541 zone_pcp_enable(zone: page_zone(page: p));
1542
1543 return ret;
1544}
1545
1546/*
1547 * Do all that is necessary to remove user space mappings. Unmap
1548 * the pages and send SIGBUS to the processes if the data was dirty.
1549 */
1550static bool hwpoison_user_mappings(struct page *p, unsigned long pfn,
1551 int flags, struct page *hpage)
1552{
1553 struct folio *folio = page_folio(hpage);
1554 enum ttu_flags ttu = TTU_IGNORE_MLOCK | TTU_SYNC | TTU_HWPOISON;
1555 struct address_space *mapping;
1556 LIST_HEAD(tokill);
1557 bool unmap_success;
1558 int forcekill;
1559 bool mlocked = PageMlocked(page: hpage);
1560
1561 /*
1562 * Here we are interested only in user-mapped pages, so skip any
1563 * other types of pages.
1564 */
1565 if (PageReserved(page: p) || PageSlab(page: p) || PageTable(page: p) || PageOffline(page: p))
1566 return true;
1567 if (!(PageLRU(page: hpage) || PageHuge(page: p)))
1568 return true;
1569
1570 /*
1571 * This check implies we don't kill processes if their pages
1572 * are in the swap cache early. Those are always late kills.
1573 */
1574 if (!page_mapped(page: hpage))
1575 return true;
1576
1577 if (PageSwapCache(page: p)) {
1578 pr_err("%#lx: keeping poisoned page in swap cache\n", pfn);
1579 ttu &= ~TTU_HWPOISON;
1580 }
1581
1582 /*
1583 * Propagate the dirty bit from PTEs to struct page first, because we
1584 * need this to decide if we should kill or just drop the page.
1585 * XXX: the dirty test could be racy: set_page_dirty() may not always
1586 * be called inside page lock (it's recommended but not enforced).
1587 */
1588 mapping = page_mapping(hpage);
1589 if (!(flags & MF_MUST_KILL) && !PageDirty(page: hpage) && mapping &&
1590 mapping_can_writeback(mapping)) {
1591 if (page_mkclean(page: hpage)) {
1592 SetPageDirty(hpage);
1593 } else {
1594 ttu &= ~TTU_HWPOISON;
1595 pr_info("%#lx: corrupted page was clean: dropped without side effects\n",
1596 pfn);
1597 }
1598 }
1599
1600 /*
1601 * First collect all the processes that have the page
1602 * mapped in dirty form. This has to be done before try_to_unmap,
1603 * because ttu takes the rmap data structures down.
1604 */
1605 collect_procs(page: hpage, tokill: &tokill, force_early: flags & MF_ACTION_REQUIRED);
1606
1607 if (PageHuge(page: hpage) && !PageAnon(page: hpage)) {
1608 /*
1609 * For hugetlb pages in shared mappings, try_to_unmap
1610 * could potentially call huge_pmd_unshare. Because of
1611 * this, take semaphore in write mode here and set
1612 * TTU_RMAP_LOCKED to indicate we have taken the lock
1613 * at this higher level.
1614 */
1615 mapping = hugetlb_page_mapping_lock_write(hpage);
1616 if (mapping) {
1617 try_to_unmap(folio, flags: ttu|TTU_RMAP_LOCKED);
1618 i_mmap_unlock_write(mapping);
1619 } else
1620 pr_info("%#lx: could not lock mapping for mapped huge page\n", pfn);
1621 } else {
1622 try_to_unmap(folio, flags: ttu);
1623 }
1624
1625 unmap_success = !page_mapped(page: hpage);
1626 if (!unmap_success)
1627 pr_err("%#lx: failed to unmap page (mapcount=%d)\n",
1628 pfn, page_mapcount(hpage));
1629
1630 /*
1631 * try_to_unmap() might put mlocked page in lru cache, so call
1632 * shake_page() again to ensure that it's flushed.
1633 */
1634 if (mlocked)
1635 shake_page(hpage);
1636
1637 /*
1638 * Now that the dirty bit has been propagated to the
1639 * struct page and all unmaps done we can decide if
1640 * killing is needed or not. Only kill when the page
1641 * was dirty or the process is not restartable,
1642 * otherwise the tokill list is merely
1643 * freed. When there was a problem unmapping earlier
1644 * use a more force-full uncatchable kill to prevent
1645 * any accesses to the poisoned memory.
1646 */
1647 forcekill = PageDirty(page: hpage) || (flags & MF_MUST_KILL) ||
1648 !unmap_success;
1649 kill_procs(to_kill: &tokill, forcekill, fail: !unmap_success, pfn, flags);
1650
1651 return unmap_success;
1652}
1653
1654static int identify_page_state(unsigned long pfn, struct page *p,
1655 unsigned long page_flags)
1656{
1657 struct page_state *ps;
1658
1659 /*
1660 * The first check uses the current page flags which may not have any
1661 * relevant information. The second check with the saved page flags is
1662 * carried out only if the first check can't determine the page status.
1663 */
1664 for (ps = error_states;; ps++)
1665 if ((p->flags & ps->mask) == ps->res)
1666 break;
1667
1668 page_flags |= (p->flags & (1UL << PG_dirty));
1669
1670 if (!ps->mask)
1671 for (ps = error_states;; ps++)
1672 if ((page_flags & ps->mask) == ps->res)
1673 break;
1674 return page_action(ps, p, pfn);
1675}
1676
1677static int try_to_split_thp_page(struct page *page)
1678{
1679 int ret;
1680
1681 lock_page(page);
1682 ret = split_huge_page(page);
1683 unlock_page(page);
1684
1685 if (unlikely(ret))
1686 put_page(page);
1687
1688 return ret;
1689}
1690
1691static void unmap_and_kill(struct list_head *to_kill, unsigned long pfn,
1692 struct address_space *mapping, pgoff_t index, int flags)
1693{
1694 struct to_kill *tk;
1695 unsigned long size = 0;
1696
1697 list_for_each_entry(tk, to_kill, nd)
1698 if (tk->size_shift)
1699 size = max(size, 1UL << tk->size_shift);
1700
1701 if (size) {
1702 /*
1703 * Unmap the largest mapping to avoid breaking up device-dax
1704 * mappings which are constant size. The actual size of the
1705 * mapping being torn down is communicated in siginfo, see
1706 * kill_proc()
1707 */
1708 loff_t start = (index << PAGE_SHIFT) & ~(size - 1);
1709
1710 unmap_mapping_range(mapping, holebegin: start, holelen: size, even_cows: 0);
1711 }
1712
1713 kill_procs(to_kill, forcekill: flags & MF_MUST_KILL, fail: false, pfn, flags);
1714}
1715
1716/*
1717 * Only dev_pagemap pages get here, such as fsdax when the filesystem
1718 * either do not claim or fails to claim a hwpoison event, or devdax.
1719 * The fsdax pages are initialized per base page, and the devdax pages
1720 * could be initialized either as base pages, or as compound pages with
1721 * vmemmap optimization enabled. Devdax is simplistic in its dealing with
1722 * hwpoison, such that, if a subpage of a compound page is poisoned,
1723 * simply mark the compound head page is by far sufficient.
1724 */
1725static int mf_generic_kill_procs(unsigned long long pfn, int flags,
1726 struct dev_pagemap *pgmap)
1727{
1728 struct folio *folio = pfn_folio(pfn);
1729 LIST_HEAD(to_kill);
1730 dax_entry_t cookie;
1731 int rc = 0;
1732
1733 /*
1734 * Prevent the inode from being freed while we are interrogating
1735 * the address_space, typically this would be handled by
1736 * lock_page(), but dax pages do not use the page lock. This
1737 * also prevents changes to the mapping of this pfn until
1738 * poison signaling is complete.
1739 */
1740 cookie = dax_lock_folio(folio);
1741 if (!cookie)
1742 return -EBUSY;
1743
1744 if (hwpoison_filter(&folio->page)) {
1745 rc = -EOPNOTSUPP;
1746 goto unlock;
1747 }
1748
1749 switch (pgmap->type) {
1750 case MEMORY_DEVICE_PRIVATE:
1751 case MEMORY_DEVICE_COHERENT:
1752 /*
1753 * TODO: Handle device pages which may need coordination
1754 * with device-side memory.
1755 */
1756 rc = -ENXIO;
1757 goto unlock;
1758 default:
1759 break;
1760 }
1761
1762 /*
1763 * Use this flag as an indication that the dax page has been
1764 * remapped UC to prevent speculative consumption of poison.
1765 */
1766 SetPageHWPoison(&folio->page);
1767
1768 /*
1769 * Unlike System-RAM there is no possibility to swap in a
1770 * different physical page at a given virtual address, so all
1771 * userspace consumption of ZONE_DEVICE memory necessitates
1772 * SIGBUS (i.e. MF_MUST_KILL)
1773 */
1774 flags |= MF_ACTION_REQUIRED | MF_MUST_KILL;
1775 collect_procs(page: &folio->page, tokill: &to_kill, force_early: true);
1776
1777 unmap_and_kill(to_kill: &to_kill, pfn, mapping: folio->mapping, index: folio->index, flags);
1778unlock:
1779 dax_unlock_folio(folio, cookie);
1780 return rc;
1781}
1782
1783#ifdef CONFIG_FS_DAX
1784/**
1785 * mf_dax_kill_procs - Collect and kill processes who are using this file range
1786 * @mapping: address_space of the file in use
1787 * @index: start pgoff of the range within the file
1788 * @count: length of the range, in unit of PAGE_SIZE
1789 * @mf_flags: memory failure flags
1790 */
1791int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index,
1792 unsigned long count, int mf_flags)
1793{
1794 LIST_HEAD(to_kill);
1795 dax_entry_t cookie;
1796 struct page *page;
1797 size_t end = index + count;
1798
1799 mf_flags |= MF_ACTION_REQUIRED | MF_MUST_KILL;
1800
1801 for (; index < end; index++) {
1802 page = NULL;
1803 cookie = dax_lock_mapping_entry(mapping, index, page: &page);
1804 if (!cookie)
1805 return -EBUSY;
1806 if (!page)
1807 goto unlock;
1808
1809 SetPageHWPoison(page);
1810
1811 collect_procs_fsdax(page, mapping, pgoff: index, to_kill: &to_kill);
1812 unmap_and_kill(to_kill: &to_kill, page_to_pfn(page), mapping,
1813 index, flags: mf_flags);
1814unlock:
1815 dax_unlock_mapping_entry(mapping, index, cookie);
1816 }
1817 return 0;
1818}
1819EXPORT_SYMBOL_GPL(mf_dax_kill_procs);
1820#endif /* CONFIG_FS_DAX */
1821
1822#ifdef CONFIG_HUGETLB_PAGE
1823
1824/*
1825 * Struct raw_hwp_page represents information about "raw error page",
1826 * constructing singly linked list from ->_hugetlb_hwpoison field of folio.
1827 */
1828struct raw_hwp_page {
1829 struct llist_node node;
1830 struct page *page;
1831};
1832
1833static inline struct llist_head *raw_hwp_list_head(struct folio *folio)
1834{
1835 return (struct llist_head *)&folio->_hugetlb_hwpoison;
1836}
1837
1838bool is_raw_hwpoison_page_in_hugepage(struct page *page)
1839{
1840 struct llist_head *raw_hwp_head;
1841 struct raw_hwp_page *p;
1842 struct folio *folio = page_folio(page);
1843 bool ret = false;
1844
1845 if (!folio_test_hwpoison(folio))
1846 return false;
1847
1848 if (!folio_test_hugetlb(folio))
1849 return PageHWPoison(page);
1850
1851 /*
1852 * When RawHwpUnreliable is set, kernel lost track of which subpages
1853 * are HWPOISON. So return as if ALL subpages are HWPOISONed.
1854 */
1855 if (folio_test_hugetlb_raw_hwp_unreliable(folio))
1856 return true;
1857
1858 mutex_lock(&mf_mutex);
1859
1860 raw_hwp_head = raw_hwp_list_head(folio);
1861 llist_for_each_entry(p, raw_hwp_head->first, node) {
1862 if (page == p->page) {
1863 ret = true;
1864 break;
1865 }
1866 }
1867
1868 mutex_unlock(lock: &mf_mutex);
1869
1870 return ret;
1871}
1872
1873static unsigned long __folio_free_raw_hwp(struct folio *folio, bool move_flag)
1874{
1875 struct llist_node *head;
1876 struct raw_hwp_page *p, *next;
1877 unsigned long count = 0;
1878
1879 head = llist_del_all(head: raw_hwp_list_head(folio));
1880 llist_for_each_entry_safe(p, next, head, node) {
1881 if (move_flag)
1882 SetPageHWPoison(p->page);
1883 else
1884 num_poisoned_pages_sub(page_to_pfn(p->page), i: 1);
1885 kfree(objp: p);
1886 count++;
1887 }
1888 return count;
1889}
1890
1891static int folio_set_hugetlb_hwpoison(struct folio *folio, struct page *page)
1892{
1893 struct llist_head *head;
1894 struct raw_hwp_page *raw_hwp;
1895 struct raw_hwp_page *p, *next;
1896 int ret = folio_test_set_hwpoison(folio) ? -EHWPOISON : 0;
1897
1898 /*
1899 * Once the hwpoison hugepage has lost reliable raw error info,
1900 * there is little meaning to keep additional error info precisely,
1901 * so skip to add additional raw error info.
1902 */
1903 if (folio_test_hugetlb_raw_hwp_unreliable(folio))
1904 return -EHWPOISON;
1905 head = raw_hwp_list_head(folio);
1906 llist_for_each_entry_safe(p, next, head->first, node) {
1907 if (p->page == page)
1908 return -EHWPOISON;
1909 }
1910
1911 raw_hwp = kmalloc(size: sizeof(struct raw_hwp_page), GFP_ATOMIC);
1912 if (raw_hwp) {
1913 raw_hwp->page = page;
1914 llist_add(new: &raw_hwp->node, head);
1915 /* the first error event will be counted in action_result(). */
1916 if (ret)
1917 num_poisoned_pages_inc(page_to_pfn(page));
1918 } else {
1919 /*
1920 * Failed to save raw error info. We no longer trace all
1921 * hwpoisoned subpages, and we need refuse to free/dissolve
1922 * this hwpoisoned hugepage.
1923 */
1924 folio_set_hugetlb_raw_hwp_unreliable(folio);
1925 /*
1926 * Once hugetlb_raw_hwp_unreliable is set, raw_hwp_page is not
1927 * used any more, so free it.
1928 */
1929 __folio_free_raw_hwp(folio, move_flag: false);
1930 }
1931 return ret;
1932}
1933
1934static unsigned long folio_free_raw_hwp(struct folio *folio, bool move_flag)
1935{
1936 /*
1937 * hugetlb_vmemmap_optimized hugepages can't be freed because struct
1938 * pages for tail pages are required but they don't exist.
1939 */
1940 if (move_flag && folio_test_hugetlb_vmemmap_optimized(folio))
1941 return 0;
1942
1943 /*
1944 * hugetlb_raw_hwp_unreliable hugepages shouldn't be unpoisoned by
1945 * definition.
1946 */
1947 if (folio_test_hugetlb_raw_hwp_unreliable(folio))
1948 return 0;
1949
1950 return __folio_free_raw_hwp(folio, move_flag);
1951}
1952
1953void folio_clear_hugetlb_hwpoison(struct folio *folio)
1954{
1955 if (folio_test_hugetlb_raw_hwp_unreliable(folio))
1956 return;
1957 if (folio_test_hugetlb_vmemmap_optimized(folio))
1958 return;
1959 folio_clear_hwpoison(folio);
1960 folio_free_raw_hwp(folio, move_flag: true);
1961}
1962
1963/*
1964 * Called from hugetlb code with hugetlb_lock held.
1965 *
1966 * Return values:
1967 * 0 - free hugepage
1968 * 1 - in-use hugepage
1969 * 2 - not a hugepage
1970 * -EBUSY - the hugepage is busy (try to retry)
1971 * -EHWPOISON - the hugepage is already hwpoisoned
1972 */
1973int __get_huge_page_for_hwpoison(unsigned long pfn, int flags,
1974 bool *migratable_cleared)
1975{
1976 struct page *page = pfn_to_page(pfn);
1977 struct folio *folio = page_folio(page);
1978 int ret = 2; /* fallback to normal page handling */
1979 bool count_increased = false;
1980
1981 if (!folio_test_hugetlb(folio))
1982 goto out;
1983
1984 if (flags & MF_COUNT_INCREASED) {
1985 ret = 1;
1986 count_increased = true;
1987 } else if (folio_test_hugetlb_freed(folio)) {
1988 ret = 0;
1989 } else if (folio_test_hugetlb_migratable(folio)) {
1990 ret = folio_try_get(folio);
1991 if (ret)
1992 count_increased = true;
1993 } else {
1994 ret = -EBUSY;
1995 if (!(flags & MF_NO_RETRY))
1996 goto out;
1997 }
1998
1999 if (folio_set_hugetlb_hwpoison(folio, page)) {
2000 ret = -EHWPOISON;
2001 goto out;
2002 }
2003
2004 /*
2005 * Clearing hugetlb_migratable for hwpoisoned hugepages to prevent them
2006 * from being migrated by memory hotremove.
2007 */
2008 if (count_increased && folio_test_hugetlb_migratable(folio)) {
2009 folio_clear_hugetlb_migratable(folio);
2010 *migratable_cleared = true;
2011 }
2012
2013 return ret;
2014out:
2015 if (count_increased)
2016 folio_put(folio);
2017 return ret;
2018}
2019
2020/*
2021 * Taking refcount of hugetlb pages needs extra care about race conditions
2022 * with basic operations like hugepage allocation/free/demotion.
2023 * So some of prechecks for hwpoison (pinning, and testing/setting
2024 * PageHWPoison) should be done in single hugetlb_lock range.
2025 */
2026static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb)
2027{
2028 int res;
2029 struct page *p = pfn_to_page(pfn);
2030 struct folio *folio;
2031 unsigned long page_flags;
2032 bool migratable_cleared = false;
2033
2034 *hugetlb = 1;
2035retry:
2036 res = get_huge_page_for_hwpoison(pfn, flags, migratable_cleared: &migratable_cleared);
2037 if (res == 2) { /* fallback to normal page handling */
2038 *hugetlb = 0;
2039 return 0;
2040 } else if (res == -EHWPOISON) {
2041 pr_err("%#lx: already hardware poisoned\n", pfn);
2042 if (flags & MF_ACTION_REQUIRED) {
2043 folio = page_folio(p);
2044 res = kill_accessing_process(current, pfn: folio_pfn(folio), flags);
2045 }
2046 return res;
2047 } else if (res == -EBUSY) {
2048 if (!(flags & MF_NO_RETRY)) {
2049 flags |= MF_NO_RETRY;
2050 goto retry;
2051 }
2052 return action_result(pfn, type: MF_MSG_UNKNOWN, result: MF_IGNORED);
2053 }
2054
2055 folio = page_folio(p);
2056 folio_lock(folio);
2057
2058 if (hwpoison_filter(p)) {
2059 folio_clear_hugetlb_hwpoison(folio);
2060 if (migratable_cleared)
2061 folio_set_hugetlb_migratable(folio);
2062 folio_unlock(folio);
2063 if (res == 1)
2064 folio_put(folio);
2065 return -EOPNOTSUPP;
2066 }
2067
2068 /*
2069 * Handling free hugepage. The possible race with hugepage allocation
2070 * or demotion can be prevented by PageHWPoison flag.
2071 */
2072 if (res == 0) {
2073 folio_unlock(folio);
2074 if (__page_handle_poison(page: p) >= 0) {
2075 page_ref_inc(page: p);
2076 res = MF_RECOVERED;
2077 } else {
2078 res = MF_FAILED;
2079 }
2080 return action_result(pfn, type: MF_MSG_FREE_HUGE, result: res);
2081 }
2082
2083 page_flags = folio->flags;
2084
2085 if (!hwpoison_user_mappings(p, pfn, flags, hpage: &folio->page)) {
2086 folio_unlock(folio);
2087 return action_result(pfn, type: MF_MSG_UNMAP_FAILED, result: MF_IGNORED);
2088 }
2089
2090 return identify_page_state(pfn, p, page_flags);
2091}
2092
2093#else
2094static inline int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb)
2095{
2096 return 0;
2097}
2098
2099static inline unsigned long folio_free_raw_hwp(struct folio *folio, bool flag)
2100{
2101 return 0;
2102}
2103#endif /* CONFIG_HUGETLB_PAGE */
2104
2105/* Drop the extra refcount in case we come from madvise() */
2106static void put_ref_page(unsigned long pfn, int flags)
2107{
2108 struct page *page;
2109
2110 if (!(flags & MF_COUNT_INCREASED))
2111 return;
2112
2113 page = pfn_to_page(pfn);
2114 if (page)
2115 put_page(page);
2116}
2117
2118static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
2119 struct dev_pagemap *pgmap)
2120{
2121 int rc = -ENXIO;
2122
2123 /* device metadata space is not recoverable */
2124 if (!pgmap_pfn_valid(pgmap, pfn))
2125 goto out;
2126
2127 /*
2128 * Call driver's implementation to handle the memory failure, otherwise
2129 * fall back to generic handler.
2130 */
2131 if (pgmap_has_memory_failure(pgmap)) {
2132 rc = pgmap->ops->memory_failure(pgmap, pfn, 1, flags);
2133 /*
2134 * Fall back to generic handler too if operation is not
2135 * supported inside the driver/device/filesystem.
2136 */
2137 if (rc != -EOPNOTSUPP)
2138 goto out;
2139 }
2140
2141 rc = mf_generic_kill_procs(pfn, flags, pgmap);
2142out:
2143 /* drop pgmap ref acquired in caller */
2144 put_dev_pagemap(pgmap);
2145 if (rc != -EOPNOTSUPP)
2146 action_result(pfn, type: MF_MSG_DAX, result: rc ? MF_FAILED : MF_RECOVERED);
2147 return rc;
2148}
2149
2150/**
2151 * memory_failure - Handle memory failure of a page.
2152 * @pfn: Page Number of the corrupted page
2153 * @flags: fine tune action taken
2154 *
2155 * This function is called by the low level machine check code
2156 * of an architecture when it detects hardware memory corruption
2157 * of a page. It tries its best to recover, which includes
2158 * dropping pages, killing processes etc.
2159 *
2160 * The function is primarily of use for corruptions that
2161 * happen outside the current execution context (e.g. when
2162 * detected by a background scrubber)
2163 *
2164 * Must run in process context (e.g. a work queue) with interrupts
2165 * enabled and no spinlocks held.
2166 *
2167 * Return: 0 for successfully handled the memory error,
2168 * -EOPNOTSUPP for hwpoison_filter() filtered the error event,
2169 * < 0(except -EOPNOTSUPP) on failure.
2170 */
2171int memory_failure(unsigned long pfn, int flags)
2172{
2173 struct page *p;
2174 struct page *hpage;
2175 struct dev_pagemap *pgmap;
2176 int res = 0;
2177 unsigned long page_flags;
2178 bool retry = true;
2179 int hugetlb = 0;
2180
2181 if (!sysctl_memory_failure_recovery)
2182 panic(fmt: "Memory failure on page %lx", pfn);
2183
2184 mutex_lock(&mf_mutex);
2185
2186 if (!(flags & MF_SW_SIMULATED))
2187 hw_memory_failure = true;
2188
2189 p = pfn_to_online_page(pfn);
2190 if (!p) {
2191 res = arch_memory_failure(pfn, flags);
2192 if (res == 0)
2193 goto unlock_mutex;
2194
2195 if (pfn_valid(pfn)) {
2196 pgmap = get_dev_pagemap(pfn, NULL);
2197 put_ref_page(pfn, flags);
2198 if (pgmap) {
2199 res = memory_failure_dev_pagemap(pfn, flags,
2200 pgmap);
2201 goto unlock_mutex;
2202 }
2203 }
2204 pr_err("%#lx: memory outside kernel control\n", pfn);
2205 res = -ENXIO;
2206 goto unlock_mutex;
2207 }
2208
2209try_again:
2210 res = try_memory_failure_hugetlb(pfn, flags, hugetlb: &hugetlb);
2211 if (hugetlb)
2212 goto unlock_mutex;
2213
2214 if (TestSetPageHWPoison(page: p)) {
2215 pr_err("%#lx: already hardware poisoned\n", pfn);
2216 res = -EHWPOISON;
2217 if (flags & MF_ACTION_REQUIRED)
2218 res = kill_accessing_process(current, pfn, flags);
2219 if (flags & MF_COUNT_INCREASED)
2220 put_page(page: p);
2221 goto unlock_mutex;
2222 }
2223
2224 /*
2225 * We need/can do nothing about count=0 pages.
2226 * 1) it's a free page, and therefore in safe hand:
2227 * check_new_page() will be the gate keeper.
2228 * 2) it's part of a non-compound high order page.
2229 * Implies some kernel user: cannot stop them from
2230 * R/W the page; let's pray that the page has been
2231 * used and will be freed some time later.
2232 * In fact it's dangerous to directly bump up page count from 0,
2233 * that may make page_ref_freeze()/page_ref_unfreeze() mismatch.
2234 */
2235 if (!(flags & MF_COUNT_INCREASED)) {
2236 res = get_hwpoison_page(p, flags);
2237 if (!res) {
2238 if (is_free_buddy_page(page: p)) {
2239 if (take_page_off_buddy(page: p)) {
2240 page_ref_inc(page: p);
2241 res = MF_RECOVERED;
2242 } else {
2243 /* We lost the race, try again */
2244 if (retry) {
2245 ClearPageHWPoison(page: p);
2246 retry = false;
2247 goto try_again;
2248 }
2249 res = MF_FAILED;
2250 }
2251 res = action_result(pfn, type: MF_MSG_BUDDY, result: res);
2252 } else {
2253 res = action_result(pfn, type: MF_MSG_KERNEL_HIGH_ORDER, result: MF_IGNORED);
2254 }
2255 goto unlock_mutex;
2256 } else if (res < 0) {
2257 res = action_result(pfn, type: MF_MSG_UNKNOWN, result: MF_IGNORED);
2258 goto unlock_mutex;
2259 }
2260 }
2261
2262 hpage = compound_head(p);
2263 if (PageTransHuge(page: hpage)) {
2264 /*
2265 * The flag must be set after the refcount is bumped
2266 * otherwise it may race with THP split.
2267 * And the flag can't be set in get_hwpoison_page() since
2268 * it is called by soft offline too and it is just called
2269 * for !MF_COUNT_INCREASED. So here seems to be the best
2270 * place.
2271 *
2272 * Don't need care about the above error handling paths for
2273 * get_hwpoison_page() since they handle either free page
2274 * or unhandlable page. The refcount is bumped iff the
2275 * page is a valid handlable page.
2276 */
2277 SetPageHasHWPoisoned(hpage);
2278 if (try_to_split_thp_page(page: p) < 0) {
2279 res = action_result(pfn, type: MF_MSG_UNSPLIT_THP, result: MF_IGNORED);
2280 goto unlock_mutex;
2281 }
2282 VM_BUG_ON_PAGE(!page_count(p), p);
2283 }
2284
2285 /*
2286 * We ignore non-LRU pages for good reasons.
2287 * - PG_locked is only well defined for LRU pages and a few others
2288 * - to avoid races with __SetPageLocked()
2289 * - to avoid races with __SetPageSlab*() (and more non-atomic ops)
2290 * The check (unnecessarily) ignores LRU pages being isolated and
2291 * walked by the page reclaim code, however that's not a big loss.
2292 */
2293 shake_page(p);
2294
2295 lock_page(page: p);
2296
2297 /*
2298 * We're only intended to deal with the non-Compound page here.
2299 * However, the page could have changed compound pages due to
2300 * race window. If this happens, we could try again to hopefully
2301 * handle the page next round.
2302 */
2303 if (PageCompound(page: p)) {
2304 if (retry) {
2305 ClearPageHWPoison(page: p);
2306 unlock_page(page: p);
2307 put_page(page: p);
2308 flags &= ~MF_COUNT_INCREASED;
2309 retry = false;
2310 goto try_again;
2311 }
2312 res = action_result(pfn, type: MF_MSG_DIFFERENT_COMPOUND, result: MF_IGNORED);
2313 goto unlock_page;
2314 }
2315
2316 /*
2317 * We use page flags to determine what action should be taken, but
2318 * the flags can be modified by the error containment action. One
2319 * example is an mlocked page, where PG_mlocked is cleared by
2320 * page_remove_rmap() in try_to_unmap_one(). So to determine page status
2321 * correctly, we save a copy of the page flags at this time.
2322 */
2323 page_flags = p->flags;
2324
2325 if (hwpoison_filter(p)) {
2326 ClearPageHWPoison(page: p);
2327 unlock_page(page: p);
2328 put_page(page: p);
2329 res = -EOPNOTSUPP;
2330 goto unlock_mutex;
2331 }
2332
2333 /*
2334 * __munlock_folio() may clear a writeback page's LRU flag without
2335 * page_lock. We need wait writeback completion for this page or it
2336 * may trigger vfs BUG while evict inode.
2337 */
2338 if (!PageLRU(page: p) && !PageWriteback(page: p))
2339 goto identify_page_state;
2340
2341 /*
2342 * It's very difficult to mess with pages currently under IO
2343 * and in many cases impossible, so we just avoid it here.
2344 */
2345 wait_on_page_writeback(page: p);
2346
2347 /*
2348 * Now take care of user space mappings.
2349 * Abort on fail: __filemap_remove_folio() assumes unmapped page.
2350 */
2351 if (!hwpoison_user_mappings(p, pfn, flags, hpage: p)) {
2352 res = action_result(pfn, type: MF_MSG_UNMAP_FAILED, result: MF_IGNORED);
2353 goto unlock_page;
2354 }
2355
2356 /*
2357 * Torn down by someone else?
2358 */
2359 if (PageLRU(page: p) && !PageSwapCache(page: p) && p->mapping == NULL) {
2360 res = action_result(pfn, type: MF_MSG_TRUNCATED_LRU, result: MF_IGNORED);
2361 goto unlock_page;
2362 }
2363
2364identify_page_state:
2365 res = identify_page_state(pfn, p, page_flags);
2366 mutex_unlock(lock: &mf_mutex);
2367 return res;
2368unlock_page:
2369 unlock_page(page: p);
2370unlock_mutex:
2371 mutex_unlock(lock: &mf_mutex);
2372 return res;
2373}
2374EXPORT_SYMBOL_GPL(memory_failure);
2375
2376#define MEMORY_FAILURE_FIFO_ORDER 4
2377#define MEMORY_FAILURE_FIFO_SIZE (1 << MEMORY_FAILURE_FIFO_ORDER)
2378
2379struct memory_failure_entry {
2380 unsigned long pfn;
2381 int flags;
2382};
2383
2384struct memory_failure_cpu {
2385 DECLARE_KFIFO(fifo, struct memory_failure_entry,
2386 MEMORY_FAILURE_FIFO_SIZE);
2387 spinlock_t lock;
2388 struct work_struct work;
2389};
2390
2391static DEFINE_PER_CPU(struct memory_failure_cpu, memory_failure_cpu);
2392
2393/**
2394 * memory_failure_queue - Schedule handling memory failure of a page.
2395 * @pfn: Page Number of the corrupted page
2396 * @flags: Flags for memory failure handling
2397 *
2398 * This function is called by the low level hardware error handler
2399 * when it detects hardware memory corruption of a page. It schedules
2400 * the recovering of error page, including dropping pages, killing
2401 * processes etc.
2402 *
2403 * The function is primarily of use for corruptions that
2404 * happen outside the current execution context (e.g. when
2405 * detected by a background scrubber)
2406 *
2407 * Can run in IRQ context.
2408 */
2409void memory_failure_queue(unsigned long pfn, int flags)
2410{
2411 struct memory_failure_cpu *mf_cpu;
2412 unsigned long proc_flags;
2413 struct memory_failure_entry entry = {
2414 .pfn = pfn,
2415 .flags = flags,
2416 };
2417
2418 mf_cpu = &get_cpu_var(memory_failure_cpu);
2419 spin_lock_irqsave(&mf_cpu->lock, proc_flags);
2420 if (kfifo_put(&mf_cpu->fifo, entry))
2421 schedule_work_on(smp_processor_id(), work: &mf_cpu->work);
2422 else
2423 pr_err("buffer overflow when queuing memory failure at %#lx\n",
2424 pfn);
2425 spin_unlock_irqrestore(lock: &mf_cpu->lock, flags: proc_flags);
2426 put_cpu_var(memory_failure_cpu);
2427}
2428EXPORT_SYMBOL_GPL(memory_failure_queue);
2429
2430static void memory_failure_work_func(struct work_struct *work)
2431{
2432 struct memory_failure_cpu *mf_cpu;
2433 struct memory_failure_entry entry = { 0, };
2434 unsigned long proc_flags;
2435 int gotten;
2436
2437 mf_cpu = container_of(work, struct memory_failure_cpu, work);
2438 for (;;) {
2439 spin_lock_irqsave(&mf_cpu->lock, proc_flags);
2440 gotten = kfifo_get(&mf_cpu->fifo, &entry);
2441 spin_unlock_irqrestore(lock: &mf_cpu->lock, flags: proc_flags);
2442 if (!gotten)
2443 break;
2444 if (entry.flags & MF_SOFT_OFFLINE)
2445 soft_offline_page(pfn: entry.pfn, flags: entry.flags);
2446 else
2447 memory_failure(entry.pfn, entry.flags);
2448 }
2449}
2450
2451/*
2452 * Process memory_failure work queued on the specified CPU.
2453 * Used to avoid return-to-userspace racing with the memory_failure workqueue.
2454 */
2455void memory_failure_queue_kick(int cpu)
2456{
2457 struct memory_failure_cpu *mf_cpu;
2458
2459 mf_cpu = &per_cpu(memory_failure_cpu, cpu);
2460 cancel_work_sync(work: &mf_cpu->work);
2461 memory_failure_work_func(work: &mf_cpu->work);
2462}
2463
2464static int __init memory_failure_init(void)
2465{
2466 struct memory_failure_cpu *mf_cpu;
2467 int cpu;
2468
2469 for_each_possible_cpu(cpu) {
2470 mf_cpu = &per_cpu(memory_failure_cpu, cpu);
2471 spin_lock_init(&mf_cpu->lock);
2472 INIT_KFIFO(mf_cpu->fifo);
2473 INIT_WORK(&mf_cpu->work, memory_failure_work_func);
2474 }
2475
2476 register_sysctl_init("vm", memory_failure_table);
2477
2478 return 0;
2479}
2480core_initcall(memory_failure_init);
2481
2482#undef pr_fmt
2483#define pr_fmt(fmt) "" fmt
2484#define unpoison_pr_info(fmt, pfn, rs) \
2485({ \
2486 if (__ratelimit(rs)) \
2487 pr_info(fmt, pfn); \
2488})
2489
2490/**
2491 * unpoison_memory - Unpoison a previously poisoned page
2492 * @pfn: Page number of the to be unpoisoned page
2493 *
2494 * Software-unpoison a page that has been poisoned by
2495 * memory_failure() earlier.
2496 *
2497 * This is only done on the software-level, so it only works
2498 * for linux injected failures, not real hardware failures
2499 *
2500 * Returns 0 for success, otherwise -errno.
2501 */
2502int unpoison_memory(unsigned long pfn)
2503{
2504 struct folio *folio;
2505 struct page *p;
2506 int ret = -EBUSY, ghp;
2507 unsigned long count = 1;
2508 bool huge = false;
2509 static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL,
2510 DEFAULT_RATELIMIT_BURST);
2511
2512 if (!pfn_valid(pfn))
2513 return -ENXIO;
2514
2515 p = pfn_to_page(pfn);
2516 folio = page_folio(p);
2517
2518 mutex_lock(&mf_mutex);
2519
2520 if (hw_memory_failure) {
2521 unpoison_pr_info("Unpoison: Disabled after HW memory failure %#lx\n",
2522 pfn, &unpoison_rs);
2523 ret = -EOPNOTSUPP;
2524 goto unlock_mutex;
2525 }
2526
2527 if (!PageHWPoison(page: p)) {
2528 unpoison_pr_info("Unpoison: Page was already unpoisoned %#lx\n",
2529 pfn, &unpoison_rs);
2530 goto unlock_mutex;
2531 }
2532
2533 if (folio_ref_count(folio) > 1) {
2534 unpoison_pr_info("Unpoison: Someone grabs the hwpoison page %#lx\n",
2535 pfn, &unpoison_rs);
2536 goto unlock_mutex;
2537 }
2538
2539 if (folio_test_slab(folio) || PageTable(page: &folio->page) ||
2540 folio_test_reserved(folio) || PageOffline(page: &folio->page))
2541 goto unlock_mutex;
2542
2543 /*
2544 * Note that folio->_mapcount is overloaded in SLAB, so the simple test
2545 * in folio_mapped() has to be done after folio_test_slab() is checked.
2546 */
2547 if (folio_mapped(folio)) {
2548 unpoison_pr_info("Unpoison: Someone maps the hwpoison page %#lx\n",
2549 pfn, &unpoison_rs);
2550 goto unlock_mutex;
2551 }
2552
2553 if (folio_mapping(folio)) {
2554 unpoison_pr_info("Unpoison: the hwpoison page has non-NULL mapping %#lx\n",
2555 pfn, &unpoison_rs);
2556 goto unlock_mutex;
2557 }
2558
2559 ghp = get_hwpoison_page(p, flags: MF_UNPOISON);
2560 if (!ghp) {
2561 if (PageHuge(page: p)) {
2562 huge = true;
2563 count = folio_free_raw_hwp(folio, move_flag: false);
2564 if (count == 0)
2565 goto unlock_mutex;
2566 }
2567 ret = folio_test_clear_hwpoison(folio) ? 0 : -EBUSY;
2568 } else if (ghp < 0) {
2569 if (ghp == -EHWPOISON) {
2570 ret = put_page_back_buddy(page: p) ? 0 : -EBUSY;
2571 } else {
2572 ret = ghp;
2573 unpoison_pr_info("Unpoison: failed to grab page %#lx\n",
2574 pfn, &unpoison_rs);
2575 }
2576 } else {
2577 if (PageHuge(page: p)) {
2578 huge = true;
2579 count = folio_free_raw_hwp(folio, move_flag: false);
2580 if (count == 0) {
2581 folio_put(folio);
2582 goto unlock_mutex;
2583 }
2584 }
2585
2586 folio_put(folio);
2587 if (TestClearPageHWPoison(page: p)) {
2588 folio_put(folio);
2589 ret = 0;
2590 }
2591 }
2592
2593unlock_mutex:
2594 mutex_unlock(lock: &mf_mutex);
2595 if (!ret) {
2596 if (!huge)
2597 num_poisoned_pages_sub(pfn, i: 1);
2598 unpoison_pr_info("Unpoison: Software-unpoisoned page %#lx\n",
2599 page_to_pfn(p), &unpoison_rs);
2600 }
2601 return ret;
2602}
2603EXPORT_SYMBOL(unpoison_memory);
2604
2605static bool isolate_page(struct page *page, struct list_head *pagelist)
2606{
2607 bool isolated = false;
2608
2609 if (PageHuge(page)) {
2610 isolated = isolate_hugetlb(page_folio(page), list: pagelist);
2611 } else {
2612 bool lru = !__PageMovable(page);
2613
2614 if (lru)
2615 isolated = isolate_lru_page(page);
2616 else
2617 isolated = isolate_movable_page(page,
2618 ISOLATE_UNEVICTABLE);
2619
2620 if (isolated) {
2621 list_add(new: &page->lru, head: pagelist);
2622 if (lru)
2623 inc_node_page_state(page, NR_ISOLATED_ANON +
2624 page_is_file_lru(page));
2625 }
2626 }
2627
2628 /*
2629 * If we succeed to isolate the page, we grabbed another refcount on
2630 * the page, so we can safely drop the one we got from get_any_page().
2631 * If we failed to isolate the page, it means that we cannot go further
2632 * and we will return an error, so drop the reference we got from
2633 * get_any_page() as well.
2634 */
2635 put_page(page);
2636 return isolated;
2637}
2638
2639/*
2640 * soft_offline_in_use_page handles hugetlb-pages and non-hugetlb pages.
2641 * If the page is a non-dirty unmapped page-cache page, it simply invalidates.
2642 * If the page is mapped, it migrates the contents over.
2643 */
2644static int soft_offline_in_use_page(struct page *page)
2645{
2646 long ret = 0;
2647 unsigned long pfn = page_to_pfn(page);
2648 struct page *hpage = compound_head(page);
2649 char const *msg_page[] = {"page", "hugepage"};
2650 bool huge = PageHuge(page);
2651 LIST_HEAD(pagelist);
2652 struct migration_target_control mtc = {
2653 .nid = NUMA_NO_NODE,
2654 .gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL,
2655 };
2656
2657 if (!huge && PageTransHuge(page: hpage)) {
2658 if (try_to_split_thp_page(page)) {
2659 pr_info("soft offline: %#lx: thp split failed\n", pfn);
2660 return -EBUSY;
2661 }
2662 hpage = page;
2663 }
2664
2665 lock_page(page);
2666 if (!huge)
2667 wait_on_page_writeback(page);
2668 if (PageHWPoison(page)) {
2669 unlock_page(page);
2670 put_page(page);
2671 pr_info("soft offline: %#lx page already poisoned\n", pfn);
2672 return 0;
2673 }
2674
2675 if (!huge && PageLRU(page) && !PageSwapCache(page))
2676 /*
2677 * Try to invalidate first. This should work for
2678 * non dirty unmapped page cache pages.
2679 */
2680 ret = invalidate_inode_page(page);
2681 unlock_page(page);
2682
2683 if (ret) {
2684 pr_info("soft_offline: %#lx: invalidated\n", pfn);
2685 page_handle_poison(page, hugepage_or_freepage: false, release: true);
2686 return 0;
2687 }
2688
2689 if (isolate_page(page: hpage, pagelist: &pagelist)) {
2690 ret = migrate_pages(l: &pagelist, new: alloc_migration_target, NULL,
2691 private: (unsigned long)&mtc, mode: MIGRATE_SYNC, reason: MR_MEMORY_FAILURE, NULL);
2692 if (!ret) {
2693 bool release = !huge;
2694
2695 if (!page_handle_poison(page, hugepage_or_freepage: huge, release))
2696 ret = -EBUSY;
2697 } else {
2698 if (!list_empty(head: &pagelist))
2699 putback_movable_pages(l: &pagelist);
2700
2701 pr_info("soft offline: %#lx: %s migration failed %ld, type %pGp\n",
2702 pfn, msg_page[huge], ret, &page->flags);
2703 if (ret > 0)
2704 ret = -EBUSY;
2705 }
2706 } else {
2707 pr_info("soft offline: %#lx: %s isolation failed, page count %d, type %pGp\n",
2708 pfn, msg_page[huge], page_count(page), &page->flags);
2709 ret = -EBUSY;
2710 }
2711 return ret;
2712}
2713
2714/**
2715 * soft_offline_page - Soft offline a page.
2716 * @pfn: pfn to soft-offline
2717 * @flags: flags. Same as memory_failure().
2718 *
2719 * Returns 0 on success
2720 * -EOPNOTSUPP for hwpoison_filter() filtered the error event
2721 * < 0 otherwise negated errno.
2722 *
2723 * Soft offline a page, by migration or invalidation,
2724 * without killing anything. This is for the case when
2725 * a page is not corrupted yet (so it's still valid to access),
2726 * but has had a number of corrected errors and is better taken
2727 * out.
2728 *
2729 * The actual policy on when to do that is maintained by
2730 * user space.
2731 *
2732 * This should never impact any application or cause data loss,
2733 * however it might take some time.
2734 *
2735 * This is not a 100% solution for all memory, but tries to be
2736 * ``good enough'' for the majority of memory.
2737 */
2738int soft_offline_page(unsigned long pfn, int flags)
2739{
2740 int ret;
2741 bool try_again = true;
2742 struct page *page;
2743
2744 if (!pfn_valid(pfn)) {
2745 WARN_ON_ONCE(flags & MF_COUNT_INCREASED);
2746 return -ENXIO;
2747 }
2748
2749 /* Only online pages can be soft-offlined (esp., not ZONE_DEVICE). */
2750 page = pfn_to_online_page(pfn);
2751 if (!page) {
2752 put_ref_page(pfn, flags);
2753 return -EIO;
2754 }
2755
2756 mutex_lock(&mf_mutex);
2757
2758 if (PageHWPoison(page)) {
2759 pr_info("%s: %#lx page already poisoned\n", __func__, pfn);
2760 put_ref_page(pfn, flags);
2761 mutex_unlock(lock: &mf_mutex);
2762 return 0;
2763 }
2764
2765retry:
2766 get_online_mems();
2767 ret = get_hwpoison_page(p: page, flags: flags | MF_SOFT_OFFLINE);
2768 put_online_mems();
2769
2770 if (hwpoison_filter(page)) {
2771 if (ret > 0)
2772 put_page(page);
2773
2774 mutex_unlock(lock: &mf_mutex);
2775 return -EOPNOTSUPP;
2776 }
2777
2778 if (ret > 0) {
2779 ret = soft_offline_in_use_page(page);
2780 } else if (ret == 0) {
2781 if (!page_handle_poison(page, hugepage_or_freepage: true, release: false)) {
2782 if (try_again) {
2783 try_again = false;
2784 flags &= ~MF_COUNT_INCREASED;
2785 goto retry;
2786 }
2787 ret = -EBUSY;
2788 }
2789 }
2790
2791 mutex_unlock(lock: &mf_mutex);
2792
2793 return ret;
2794}
2795

source code of linux/mm/memory-failure.c