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/vm/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#include <linux/kernel.h>
  37#include <linux/mm.h>
  38#include <linux/page-flags.h>
  39#include <linux/kernel-page-flags.h>
  40#include <linux/sched/signal.h>
  41#include <linux/sched/task.h>
  42#include <linux/ksm.h>
  43#include <linux/rmap.h>
  44#include <linux/export.h>
  45#include <linux/pagemap.h>
  46#include <linux/swap.h>
  47#include <linux/backing-dev.h>
  48#include <linux/migrate.h>
 
  49#include <linux/suspend.h>
  50#include <linux/slab.h>
  51#include <linux/swapops.h>
  52#include <linux/hugetlb.h>
  53#include <linux/memory_hotplug.h>
  54#include <linux/mm_inline.h>
  55#include <linux/memremap.h>
  56#include <linux/kfifo.h>
  57#include <linux/ratelimit.h>
  58#include <linux/page-isolation.h>
  59#include "internal.h"
  60#include "ras/ras_event.h"
  61
  62int sysctl_memory_failure_early_kill __read_mostly = 0;
  63
  64int sysctl_memory_failure_recovery __read_mostly = 1;
  65
  66atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0);
  67
  68#if defined(CONFIG_HWPOISON_INJECT) || defined(CONFIG_HWPOISON_INJECT_MODULE)
  69
  70u32 hwpoison_filter_enable = 0;
  71u32 hwpoison_filter_dev_major = ~0U;
  72u32 hwpoison_filter_dev_minor = ~0U;
  73u64 hwpoison_filter_flags_mask;
  74u64 hwpoison_filter_flags_value;
  75EXPORT_SYMBOL_GPL(hwpoison_filter_enable);
  76EXPORT_SYMBOL_GPL(hwpoison_filter_dev_major);
  77EXPORT_SYMBOL_GPL(hwpoison_filter_dev_minor);
  78EXPORT_SYMBOL_GPL(hwpoison_filter_flags_mask);
  79EXPORT_SYMBOL_GPL(hwpoison_filter_flags_value);
  80
  81static int hwpoison_filter_dev(struct page *p)
  82{
  83	struct address_space *mapping;
  84	dev_t dev;
  85
  86	if (hwpoison_filter_dev_major == ~0U &&
  87	    hwpoison_filter_dev_minor == ~0U)
  88		return 0;
  89
  90	/*
  91	 * page_mapping() does not accept slab pages.
  92	 */
  93	if (PageSlab(p))
  94		return -EINVAL;
  95
  96	mapping = page_mapping(p);
  97	if (mapping == NULL || mapping->host == NULL)
  98		return -EINVAL;
  99
 100	dev = mapping->host->i_sb->s_dev;
 101	if (hwpoison_filter_dev_major != ~0U &&
 102	    hwpoison_filter_dev_major != MAJOR(dev))
 103		return -EINVAL;
 104	if (hwpoison_filter_dev_minor != ~0U &&
 105	    hwpoison_filter_dev_minor != MINOR(dev))
 106		return -EINVAL;
 107
 108	return 0;
 109}
 110
 111static int hwpoison_filter_flags(struct page *p)
 112{
 113	if (!hwpoison_filter_flags_mask)
 114		return 0;
 115
 116	if ((stable_page_flags(p) & hwpoison_filter_flags_mask) ==
 117				    hwpoison_filter_flags_value)
 118		return 0;
 119	else
 120		return -EINVAL;
 121}
 122
 123/*
 124 * This allows stress tests to limit test scope to a collection of tasks
 125 * by putting them under some memcg. This prevents killing unrelated/important
 126 * processes such as /sbin/init. Note that the target task may share clean
 127 * pages with init (eg. libc text), which is harmless. If the target task
 128 * share _dirty_ pages with another task B, the test scheme must make sure B
 129 * is also included in the memcg. At last, due to race conditions this filter
 130 * can only guarantee that the page either belongs to the memcg tasks, or is
 131 * a freed page.
 132 */
 133#ifdef CONFIG_MEMCG
 134u64 hwpoison_filter_memcg;
 135EXPORT_SYMBOL_GPL(hwpoison_filter_memcg);
 136static int hwpoison_filter_task(struct page *p)
 137{
 
 
 
 
 138	if (!hwpoison_filter_memcg)
 139		return 0;
 140
 141	if (page_cgroup_ino(p) != hwpoison_filter_memcg)
 
 
 
 
 
 
 
 
 
 
 
 
 142		return -EINVAL;
 143
 144	return 0;
 145}
 146#else
 147static int hwpoison_filter_task(struct page *p) { return 0; }
 148#endif
 149
 150int hwpoison_filter(struct page *p)
 151{
 152	if (!hwpoison_filter_enable)
 153		return 0;
 154
 155	if (hwpoison_filter_dev(p))
 156		return -EINVAL;
 157
 158	if (hwpoison_filter_flags(p))
 159		return -EINVAL;
 160
 161	if (hwpoison_filter_task(p))
 162		return -EINVAL;
 163
 164	return 0;
 165}
 166#else
 167int hwpoison_filter(struct page *p)
 168{
 169	return 0;
 170}
 171#endif
 172
 173EXPORT_SYMBOL_GPL(hwpoison_filter);
 174
 175/*
 176 * Kill all processes that have a poisoned page mapped and then isolate
 177 * the page.
 178 *
 179 * General strategy:
 180 * Find all processes having the page mapped and kill them.
 181 * But we keep a page reference around so that the page is not
 182 * actually freed yet.
 183 * Then stash the page away
 184 *
 185 * There's no convenient way to get back to mapped processes
 186 * from the VMAs. So do a brute-force search over all
 187 * running processes.
 188 *
 189 * Remember that machine checks are not common (or rather
 190 * if they are common you have other problems), so this shouldn't
 191 * be a performance issue.
 192 *
 193 * Also there are some races possible while we get from the
 194 * error detection to actually handle it.
 195 */
 196
 197struct to_kill {
 198	struct list_head nd;
 199	struct task_struct *tsk;
 200	unsigned long addr;
 201	short size_shift;
 202};
 203
 204/*
 205 * Send all the processes who have the page mapped a signal.
 206 * ``action optional'' if they are not immediately affected by the error
 207 * ``action required'' if error happened in current execution context
 208 */
 209static int kill_proc(struct to_kill *tk, unsigned long pfn, int flags)
 
 210{
 211	struct task_struct *t = tk->tsk;
 212	short addr_lsb = tk->size_shift;
 213	int ret;
 214
 215	pr_err("Memory failure: %#lx: Sending SIGBUS to %s:%d due to hardware memory corruption\n",
 
 216		pfn, t->comm, t->pid);
 217
 218	if ((flags & MF_ACTION_REQUIRED) && t->mm == current->mm) {
 219		ret = force_sig_mceerr(BUS_MCEERR_AR, (void __user *)tk->addr,
 220				       addr_lsb);
 221	} else {
 222		/*
 223		 * Don't use force here, it's convenient if the signal
 224		 * can be temporarily blocked.
 225		 * This could cause a loop when the user sets SIGBUS
 226		 * to SIG_IGN, but hopefully no one will do that?
 227		 */
 228		ret = send_sig_mceerr(BUS_MCEERR_AO, (void __user *)tk->addr,
 229				      addr_lsb, t);  /* synchronous? */
 230	}
 
 231	if (ret < 0)
 232		pr_info("Memory failure: Error sending signal to %s:%d: %d\n",
 233			t->comm, t->pid, ret);
 234	return ret;
 235}
 236
 237/*
 238 * When a unknown page type is encountered drain as many buffers as possible
 239 * in the hope to turn the page into a LRU or free page, which we can handle.
 240 */
 241void shake_page(struct page *p, int access)
 242{
 243	if (PageHuge(p))
 244		return;
 245
 246	if (!PageSlab(p)) {
 247		lru_add_drain_all();
 248		if (PageLRU(p))
 249			return;
 250		drain_all_pages(page_zone(p));
 251		if (PageLRU(p) || is_free_buddy_page(p))
 252			return;
 253	}
 254
 255	/*
 256	 * Only call shrink_node_slabs here (which would also shrink
 257	 * other caches) if access is not potentially fatal.
 258	 */
 259	if (access)
 260		drop_slab_node(page_to_nid(p));
 
 
 
 
 
 
 
 
 
 
 261}
 262EXPORT_SYMBOL_GPL(shake_page);
 263
 264static unsigned long dev_pagemap_mapping_shift(struct page *page,
 265		struct vm_area_struct *vma)
 266{
 267	unsigned long address = vma_address(page, vma);
 268	pgd_t *pgd;
 269	p4d_t *p4d;
 270	pud_t *pud;
 271	pmd_t *pmd;
 272	pte_t *pte;
 
 
 
 
 
 
 
 
 
 
 
 
 273
 274	pgd = pgd_offset(vma->vm_mm, address);
 275	if (!pgd_present(*pgd))
 276		return 0;
 277	p4d = p4d_offset(pgd, address);
 278	if (!p4d_present(*p4d))
 279		return 0;
 280	pud = pud_offset(p4d, address);
 281	if (!pud_present(*pud))
 282		return 0;
 283	if (pud_devmap(*pud))
 284		return PUD_SHIFT;
 285	pmd = pmd_offset(pud, address);
 286	if (!pmd_present(*pmd))
 287		return 0;
 288	if (pmd_devmap(*pmd))
 289		return PMD_SHIFT;
 290	pte = pte_offset_map(pmd, address);
 291	if (!pte_present(*pte))
 292		return 0;
 293	if (pte_devmap(*pte))
 294		return PAGE_SHIFT;
 295	return 0;
 296}
 297
 298/*
 299 * Failure handling: if we can't find or can't kill a process there's
 300 * not much we can do.	We just print a message and ignore otherwise.
 301 */
 302
 303/*
 304 * Schedule a process for later kill.
 305 * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
 306 * TBD would GFP_NOIO be enough?
 307 */
 308static void add_to_kill(struct task_struct *tsk, struct page *p,
 309		       struct vm_area_struct *vma,
 310		       struct list_head *to_kill,
 311		       struct to_kill **tkc)
 312{
 313	struct to_kill *tk;
 314
 315	if (*tkc) {
 316		tk = *tkc;
 317		*tkc = NULL;
 318	} else {
 319		tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
 320		if (!tk) {
 321			pr_err("Memory failure: Out of memory while machine check handling\n");
 
 322			return;
 323		}
 324	}
 325	tk->addr = page_address_in_vma(p, vma);
 326	if (is_zone_device_page(p))
 327		tk->size_shift = dev_pagemap_mapping_shift(p, vma);
 328	else
 329		tk->size_shift = compound_order(compound_head(p)) + PAGE_SHIFT;
 330
 331	/*
 332	 * Send SIGKILL if "tk->addr == -EFAULT". Also, as
 333	 * "tk->size_shift" is always non-zero for !is_zone_device_page(),
 334	 * so "tk->size_shift == 0" effectively checks no mapping on
 335	 * ZONE_DEVICE. Indeed, when a devdax page is mmapped N times
 336	 * to a process' address space, it's possible not all N VMAs
 337	 * contain mappings for the page, but at least one VMA does.
 338	 * Only deliver SIGBUS with payload derived from the VMA that
 339	 * has a mapping for the page.
 340	 */
 341	if (tk->addr == -EFAULT) {
 342		pr_info("Memory failure: Unable to find user space address %lx in %s\n",
 343			page_to_pfn(p), tsk->comm);
 344	} else if (tk->size_shift == 0) {
 345		kfree(tk);
 346		return;
 347	}
 348	get_task_struct(tsk);
 349	tk->tsk = tsk;
 350	list_add_tail(&tk->nd, to_kill);
 351}
 352
 353/*
 354 * Kill the processes that have been collected earlier.
 355 *
 356 * Only do anything when DOIT is set, otherwise just free the list
 357 * (this is used for clean pages which do not need killing)
 358 * Also when FAIL is set do a force kill because something went
 359 * wrong earlier.
 360 */
 361static void kill_procs(struct list_head *to_kill, int forcekill, bool fail,
 362		unsigned long pfn, int flags)
 363{
 364	struct to_kill *tk, *next;
 365
 366	list_for_each_entry_safe (tk, next, to_kill, nd) {
 367		if (forcekill) {
 368			/*
 369			 * In case something went wrong with munmapping
 370			 * make sure the process doesn't catch the
 371			 * signal and then access the memory. Just kill it.
 372			 */
 373			if (fail || tk->addr == -EFAULT) {
 374				pr_err("Memory failure: %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n",
 375				       pfn, tk->tsk->comm, tk->tsk->pid);
 376				do_send_sig_info(SIGKILL, SEND_SIG_PRIV,
 377						 tk->tsk, PIDTYPE_PID);
 378			}
 379
 380			/*
 381			 * In theory the process could have mapped
 382			 * something else on the address in-between. We could
 383			 * check for that, but we need to tell the
 384			 * process anyways.
 385			 */
 386			else if (kill_proc(tk, pfn, flags) < 0)
 387				pr_err("Memory failure: %#lx: Cannot send advisory machine check signal to %s:%d\n",
 388				       pfn, tk->tsk->comm, tk->tsk->pid);
 
 
 389		}
 390		put_task_struct(tk->tsk);
 391		kfree(tk);
 392	}
 393}
 394
 395/*
 396 * Find a dedicated thread which is supposed to handle SIGBUS(BUS_MCEERR_AO)
 397 * on behalf of the thread group. Return task_struct of the (first found)
 398 * dedicated thread if found, and return NULL otherwise.
 399 *
 400 * We already hold read_lock(&tasklist_lock) in the caller, so we don't
 401 * have to call rcu_read_lock/unlock() in this function.
 402 */
 403static struct task_struct *find_early_kill_thread(struct task_struct *tsk)
 404{
 405	struct task_struct *t;
 406
 407	for_each_thread(tsk, t)
 408		if ((t->flags & PF_MCE_PROCESS) && (t->flags & PF_MCE_EARLY))
 409			return t;
 410	return NULL;
 411}
 412
 413/*
 414 * Determine whether a given process is "early kill" process which expects
 415 * to be signaled when some page under the process is hwpoisoned.
 416 * Return task_struct of the dedicated thread (main thread unless explicitly
 417 * specified) if the process is "early kill," and otherwise returns NULL.
 418 */
 419static struct task_struct *task_early_kill(struct task_struct *tsk,
 420					   int force_early)
 421{
 422	struct task_struct *t;
 423	if (!tsk->mm)
 424		return NULL;
 425	if (force_early)
 426		return tsk;
 427	t = find_early_kill_thread(tsk);
 428	if (t)
 429		return t;
 430	if (sysctl_memory_failure_early_kill)
 431		return tsk;
 432	return NULL;
 433}
 434
 435/*
 436 * Collect processes when the error hit an anonymous page.
 437 */
 438static void collect_procs_anon(struct page *page, struct list_head *to_kill,
 439			      struct to_kill **tkc, int force_early)
 440{
 441	struct vm_area_struct *vma;
 442	struct task_struct *tsk;
 443	struct anon_vma *av;
 444	pgoff_t pgoff;
 445
 446	av = page_lock_anon_vma_read(page);
 447	if (av == NULL)	/* Not actually mapped anymore */
 448		return;
 449
 450	pgoff = page_to_pgoff(page);
 451	read_lock(&tasklist_lock);
 452	for_each_process (tsk) {
 453		struct anon_vma_chain *vmac;
 454		struct task_struct *t = task_early_kill(tsk, force_early);
 455
 456		if (!t)
 457			continue;
 458		anon_vma_interval_tree_foreach(vmac, &av->rb_root,
 459					       pgoff, pgoff) {
 460			vma = vmac->vma;
 461			if (!page_mapped_in_vma(page, vma))
 462				continue;
 463			if (vma->vm_mm == t->mm)
 464				add_to_kill(t, page, vma, to_kill, tkc);
 465		}
 466	}
 467	read_unlock(&tasklist_lock);
 468	page_unlock_anon_vma_read(av);
 469}
 470
 471/*
 472 * Collect processes when the error hit a file mapped page.
 473 */
 474static void collect_procs_file(struct page *page, struct list_head *to_kill,
 475			      struct to_kill **tkc, int force_early)
 476{
 477	struct vm_area_struct *vma;
 478	struct task_struct *tsk;
 
 479	struct address_space *mapping = page->mapping;
 480
 481	i_mmap_lock_read(mapping);
 482	read_lock(&tasklist_lock);
 483	for_each_process(tsk) {
 484		pgoff_t pgoff = page_to_pgoff(page);
 485		struct task_struct *t = task_early_kill(tsk, force_early);
 486
 487		if (!t)
 488			continue;
 489		vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff,
 
 490				      pgoff) {
 491			/*
 492			 * Send early kill signal to tasks where a vma covers
 493			 * the page but the corrupted page is not necessarily
 494			 * mapped it in its pte.
 495			 * Assume applications who requested early kill want
 496			 * to be informed of all such data corruptions.
 497			 */
 498			if (vma->vm_mm == t->mm)
 499				add_to_kill(t, page, vma, to_kill, tkc);
 500		}
 501	}
 502	read_unlock(&tasklist_lock);
 503	i_mmap_unlock_read(mapping);
 504}
 505
 506/*
 507 * Collect the processes who have the corrupted page mapped to kill.
 508 * This is done in two steps for locking reasons.
 509 * First preallocate one tokill structure outside the spin locks,
 510 * so that we can kill at least one process reasonably reliable.
 511 */
 512static void collect_procs(struct page *page, struct list_head *tokill,
 513				int force_early)
 514{
 515	struct to_kill *tk;
 516
 517	if (!page->mapping)
 518		return;
 519
 520	tk = kmalloc(sizeof(struct to_kill), GFP_NOIO);
 521	if (!tk)
 522		return;
 523	if (PageAnon(page))
 524		collect_procs_anon(page, tokill, &tk, force_early);
 525	else
 526		collect_procs_file(page, tokill, &tk, force_early);
 527	kfree(tk);
 528}
 529
 530static const char *action_name[] = {
 531	[MF_IGNORED] = "Ignored",
 532	[MF_FAILED] = "Failed",
 533	[MF_DELAYED] = "Delayed",
 534	[MF_RECOVERED] = "Recovered",
 
 
 
 
 535};
 536
 537static const char * const action_page_types[] = {
 538	[MF_MSG_KERNEL]			= "reserved kernel page",
 539	[MF_MSG_KERNEL_HIGH_ORDER]	= "high-order kernel page",
 540	[MF_MSG_SLAB]			= "kernel slab page",
 541	[MF_MSG_DIFFERENT_COMPOUND]	= "different compound page after locking",
 542	[MF_MSG_POISONED_HUGE]		= "huge page already hardware poisoned",
 543	[MF_MSG_HUGE]			= "huge page",
 544	[MF_MSG_FREE_HUGE]		= "free huge page",
 545	[MF_MSG_NON_PMD_HUGE]		= "non-pmd-sized huge page",
 546	[MF_MSG_UNMAP_FAILED]		= "unmapping failed page",
 547	[MF_MSG_DIRTY_SWAPCACHE]	= "dirty swapcache page",
 548	[MF_MSG_CLEAN_SWAPCACHE]	= "clean swapcache page",
 549	[MF_MSG_DIRTY_MLOCKED_LRU]	= "dirty mlocked LRU page",
 550	[MF_MSG_CLEAN_MLOCKED_LRU]	= "clean mlocked LRU page",
 551	[MF_MSG_DIRTY_UNEVICTABLE_LRU]	= "dirty unevictable LRU page",
 552	[MF_MSG_CLEAN_UNEVICTABLE_LRU]	= "clean unevictable LRU page",
 553	[MF_MSG_DIRTY_LRU]		= "dirty LRU page",
 554	[MF_MSG_CLEAN_LRU]		= "clean LRU page",
 555	[MF_MSG_TRUNCATED_LRU]		= "already truncated LRU page",
 556	[MF_MSG_BUDDY]			= "free buddy page",
 557	[MF_MSG_BUDDY_2ND]		= "free buddy page (2nd try)",
 558	[MF_MSG_DAX]			= "dax page",
 559	[MF_MSG_UNKNOWN]		= "unknown page",
 560};
 561
 562/*
 563 * XXX: It is possible that a page is isolated from LRU cache,
 564 * and then kept in swap cache or failed to remove from page cache.
 565 * The page count will stop it from being freed by unpoison.
 566 * Stress tests should be aware of this memory leak problem.
 567 */
 568static int delete_from_lru_cache(struct page *p)
 569{
 570	if (!isolate_lru_page(p)) {
 571		/*
 572		 * Clear sensible page flags, so that the buddy system won't
 573		 * complain when the page is unpoison-and-freed.
 574		 */
 575		ClearPageActive(p);
 576		ClearPageUnevictable(p);
 577
 578		/*
 579		 * Poisoned page might never drop its ref count to 0 so we have
 580		 * to uncharge it manually from its memcg.
 581		 */
 582		mem_cgroup_uncharge(p);
 583
 584		/*
 585		 * drop the page count elevated by isolate_lru_page()
 586		 */
 587		put_page(p);
 588		return 0;
 589	}
 590	return -EIO;
 591}
 592
 593static int truncate_error_page(struct page *p, unsigned long pfn,
 594				struct address_space *mapping)
 595{
 596	int ret = MF_FAILED;
 597
 598	if (mapping->a_ops->error_remove_page) {
 599		int err = mapping->a_ops->error_remove_page(mapping, p);
 600
 601		if (err != 0) {
 602			pr_info("Memory failure: %#lx: Failed to punch page: %d\n",
 603				pfn, err);
 604		} else if (page_has_private(p) &&
 605			   !try_to_release_page(p, GFP_NOIO)) {
 606			pr_info("Memory failure: %#lx: failed to release buffers\n",
 607				pfn);
 608		} else {
 609			ret = MF_RECOVERED;
 610		}
 611	} else {
 612		/*
 613		 * If the file system doesn't support it just invalidate
 614		 * This fails on dirty or anything with private pages
 615		 */
 616		if (invalidate_inode_page(p))
 617			ret = MF_RECOVERED;
 618		else
 619			pr_info("Memory failure: %#lx: Failed to invalidate\n",
 620				pfn);
 621	}
 622
 623	return ret;
 624}
 625
 626/*
 627 * Error hit kernel page.
 628 * Do nothing, try to be lucky and not touch this instead. For a few cases we
 629 * could be more sophisticated.
 630 */
 631static int me_kernel(struct page *p, unsigned long pfn)
 632{
 633	return MF_IGNORED;
 634}
 635
 636/*
 637 * Page in unknown state. Do nothing.
 638 */
 639static int me_unknown(struct page *p, unsigned long pfn)
 640{
 641	pr_err("Memory failure: %#lx: Unknown page state\n", pfn);
 642	return MF_FAILED;
 643}
 644
 645/*
 646 * Clean (or cleaned) page cache page.
 647 */
 648static int me_pagecache_clean(struct page *p, unsigned long pfn)
 649{
 
 
 650	struct address_space *mapping;
 651
 652	delete_from_lru_cache(p);
 653
 654	/*
 655	 * For anonymous pages we're done the only reference left
 656	 * should be the one m_f() holds.
 657	 */
 658	if (PageAnon(p))
 659		return MF_RECOVERED;
 660
 661	/*
 662	 * Now truncate the page in the page cache. This is really
 663	 * more like a "temporary hole punch"
 664	 * Don't do this for block devices when someone else
 665	 * has a reference, because it could be file system metadata
 666	 * and that's not safe to truncate.
 667	 */
 668	mapping = page_mapping(p);
 669	if (!mapping) {
 670		/*
 671		 * Page has been teared down in the meanwhile
 672		 */
 673		return MF_FAILED;
 674	}
 675
 676	/*
 677	 * Truncation is a bit tricky. Enable it per file system for now.
 678	 *
 679	 * Open: to take i_mutex or not for this? Right now we don't.
 680	 */
 681	return truncate_error_page(p, pfn, mapping);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 682}
 683
 684/*
 685 * Dirty pagecache page
 686 * Issues: when the error hit a hole page the error is not properly
 687 * propagated.
 688 */
 689static int me_pagecache_dirty(struct page *p, unsigned long pfn)
 690{
 691	struct address_space *mapping = page_mapping(p);
 692
 693	SetPageError(p);
 694	/* TBD: print more information about the file. */
 695	if (mapping) {
 696		/*
 697		 * IO error will be reported by write(), fsync(), etc.
 698		 * who check the mapping.
 699		 * This way the application knows that something went
 700		 * wrong with its dirty file data.
 701		 *
 702		 * There's one open issue:
 703		 *
 704		 * The EIO will be only reported on the next IO
 705		 * operation and then cleared through the IO map.
 706		 * Normally Linux has two mechanisms to pass IO error
 707		 * first through the AS_EIO flag in the address space
 708		 * and then through the PageError flag in the page.
 709		 * Since we drop pages on memory failure handling the
 710		 * only mechanism open to use is through AS_AIO.
 711		 *
 712		 * This has the disadvantage that it gets cleared on
 713		 * the first operation that returns an error, while
 714		 * the PageError bit is more sticky and only cleared
 715		 * when the page is reread or dropped.  If an
 716		 * application assumes it will always get error on
 717		 * fsync, but does other operations on the fd before
 718		 * and the page is dropped between then the error
 719		 * will not be properly reported.
 720		 *
 721		 * This can already happen even without hwpoisoned
 722		 * pages: first on metadata IO errors (which only
 723		 * report through AS_EIO) or when the page is dropped
 724		 * at the wrong time.
 725		 *
 726		 * So right now we assume that the application DTRT on
 727		 * the first EIO, but we're not worse than other parts
 728		 * of the kernel.
 729		 */
 730		mapping_set_error(mapping, -EIO);
 731	}
 732
 733	return me_pagecache_clean(p, pfn);
 734}
 735
 736/*
 737 * Clean and dirty swap cache.
 738 *
 739 * Dirty swap cache page is tricky to handle. The page could live both in page
 740 * cache and swap cache(ie. page is freshly swapped in). So it could be
 741 * referenced concurrently by 2 types of PTEs:
 742 * normal PTEs and swap PTEs. We try to handle them consistently by calling
 743 * try_to_unmap(TTU_IGNORE_HWPOISON) to convert the normal PTEs to swap PTEs,
 744 * and then
 745 *      - clear dirty bit to prevent IO
 746 *      - remove from LRU
 747 *      - but keep in the swap cache, so that when we return to it on
 748 *        a later page fault, we know the application is accessing
 749 *        corrupted data and shall be killed (we installed simple
 750 *        interception code in do_swap_page to catch it).
 751 *
 752 * Clean swap cache pages can be directly isolated. A later page fault will
 753 * bring in the known good data from disk.
 754 */
 755static int me_swapcache_dirty(struct page *p, unsigned long pfn)
 756{
 757	ClearPageDirty(p);
 758	/* Trigger EIO in shmem: */
 759	ClearPageUptodate(p);
 760
 761	if (!delete_from_lru_cache(p))
 762		return MF_DELAYED;
 763	else
 764		return MF_FAILED;
 765}
 766
 767static int me_swapcache_clean(struct page *p, unsigned long pfn)
 768{
 769	delete_from_swap_cache(p);
 770
 771	if (!delete_from_lru_cache(p))
 772		return MF_RECOVERED;
 773	else
 774		return MF_FAILED;
 775}
 776
 777/*
 778 * Huge pages. Needs work.
 779 * Issues:
 780 * - Error on hugepage is contained in hugepage unit (not in raw page unit.)
 781 *   To narrow down kill region to one page, we need to break up pmd.
 782 */
 783static int me_huge_page(struct page *p, unsigned long pfn)
 784{
 785	int res = 0;
 786	struct page *hpage = compound_head(p);
 787	struct address_space *mapping;
 788
 789	if (!PageHuge(hpage))
 790		return MF_DELAYED;
 791
 792	mapping = page_mapping(hpage);
 793	if (mapping) {
 794		res = truncate_error_page(hpage, pfn, mapping);
 795	} else {
 796		unlock_page(hpage);
 797		/*
 798		 * migration entry prevents later access on error anonymous
 799		 * hugepage, so we can free and dissolve it into buddy to
 800		 * save healthy subpages.
 801		 */
 802		if (PageAnon(hpage))
 803			put_page(hpage);
 804		dissolve_free_huge_page(p);
 805		res = MF_RECOVERED;
 806		lock_page(hpage);
 807	}
 808
 809	return res;
 810}
 811
 812/*
 813 * Various page states we can handle.
 814 *
 815 * A page state is defined by its current page->flags bits.
 816 * The table matches them in order and calls the right handler.
 817 *
 818 * This is quite tricky because we can access page at any time
 819 * in its live cycle, so all accesses have to be extremely careful.
 820 *
 821 * This is not complete. More states could be added.
 822 * For any missing state don't attempt recovery.
 823 */
 824
 825#define dirty		(1UL << PG_dirty)
 826#define sc		((1UL << PG_swapcache) | (1UL << PG_swapbacked))
 827#define unevict		(1UL << PG_unevictable)
 828#define mlock		(1UL << PG_mlocked)
 829#define writeback	(1UL << PG_writeback)
 830#define lru		(1UL << PG_lru)
 
 831#define head		(1UL << PG_head)
 
 
 832#define slab		(1UL << PG_slab)
 833#define reserved	(1UL << PG_reserved)
 834
 835static struct page_state {
 836	unsigned long mask;
 837	unsigned long res;
 838	enum mf_action_page_type type;
 839	int (*action)(struct page *p, unsigned long pfn);
 840} error_states[] = {
 841	{ reserved,	reserved,	MF_MSG_KERNEL,	me_kernel },
 842	/*
 843	 * free pages are specially detected outside this table:
 844	 * PG_buddy pages only make a small fraction of all free pages.
 845	 */
 846
 847	/*
 848	 * Could in theory check if slab page is free or if we can drop
 849	 * currently unused objects without touching them. But just
 850	 * treat it as standard kernel for now.
 851	 */
 852	{ slab,		slab,		MF_MSG_SLAB,	me_kernel },
 853
 854	{ head,		head,		MF_MSG_HUGE,		me_huge_page },
 
 
 
 
 
 855
 856	{ sc|dirty,	sc|dirty,	MF_MSG_DIRTY_SWAPCACHE,	me_swapcache_dirty },
 857	{ sc|dirty,	sc,		MF_MSG_CLEAN_SWAPCACHE,	me_swapcache_clean },
 858
 859	{ mlock|dirty,	mlock|dirty,	MF_MSG_DIRTY_MLOCKED_LRU,	me_pagecache_dirty },
 860	{ mlock|dirty,	mlock,		MF_MSG_CLEAN_MLOCKED_LRU,	me_pagecache_clean },
 861
 862	{ unevict|dirty, unevict|dirty,	MF_MSG_DIRTY_UNEVICTABLE_LRU,	me_pagecache_dirty },
 863	{ unevict|dirty, unevict,	MF_MSG_CLEAN_UNEVICTABLE_LRU,	me_pagecache_clean },
 864
 865	{ lru|dirty,	lru|dirty,	MF_MSG_DIRTY_LRU,	me_pagecache_dirty },
 866	{ lru|dirty,	lru,		MF_MSG_CLEAN_LRU,	me_pagecache_clean },
 867
 868	/*
 869	 * Catchall entry: must be at end.
 870	 */
 871	{ 0,		0,		MF_MSG_UNKNOWN,	me_unknown },
 872};
 873
 874#undef dirty
 875#undef sc
 876#undef unevict
 877#undef mlock
 878#undef writeback
 879#undef lru
 
 880#undef head
 
 
 881#undef slab
 882#undef reserved
 883
 884/*
 885 * "Dirty/Clean" indication is not 100% accurate due to the possibility of
 886 * setting PG_dirty outside page lock. See also comment above set_page_dirty().
 887 */
 888static void action_result(unsigned long pfn, enum mf_action_page_type type,
 889			  enum mf_result result)
 890{
 891	trace_memory_failure_event(pfn, type, result);
 892
 893	pr_err("Memory failure: %#lx: recovery action for %s: %s\n",
 894		pfn, action_page_types[type], action_name[result]);
 
 
 895}
 896
 897static int page_action(struct page_state *ps, struct page *p,
 898			unsigned long pfn)
 899{
 900	int result;
 901	int count;
 902
 903	result = ps->action(p, pfn);
 
 904
 905	count = page_count(p) - 1;
 906	if (ps->action == me_swapcache_dirty && result == MF_DELAYED)
 907		count--;
 908	if (count > 0) {
 909		pr_err("Memory failure: %#lx: %s still referenced by %d users\n",
 910		       pfn, action_page_types[ps->type], count);
 911		result = MF_FAILED;
 
 912	}
 913	action_result(pfn, ps->type, result);
 914
 915	/* Could do more checks here if page looks ok */
 916	/*
 917	 * Could adjust zone counters here to correct for the missing page.
 918	 */
 919
 920	return (result == MF_RECOVERED || result == MF_DELAYED) ? 0 : -EBUSY;
 921}
 922
 923/**
 924 * get_hwpoison_page() - Get refcount for memory error handling:
 925 * @page:	raw error page (hit by memory error)
 926 *
 927 * Return: return 0 if failed to grab the refcount, otherwise true (some
 928 * non-zero value.)
 929 */
 930int get_hwpoison_page(struct page *page)
 931{
 932	struct page *head = compound_head(page);
 933
 934	if (!PageHuge(head) && PageTransHuge(head)) {
 935		/*
 936		 * Non anonymous thp exists only in allocation/free time. We
 937		 * can't handle such a case correctly, so let's give it up.
 938		 * This should be better than triggering BUG_ON when kernel
 939		 * tries to touch the "partially handled" page.
 940		 */
 941		if (!PageAnon(head)) {
 942			pr_err("Memory failure: %#lx: non anonymous thp\n",
 943				page_to_pfn(page));
 944			return 0;
 945		}
 946	}
 947
 948	if (get_page_unless_zero(head)) {
 949		if (head == compound_head(page))
 950			return 1;
 951
 952		pr_info("Memory failure: %#lx cannot catch tail\n",
 953			page_to_pfn(page));
 954		put_page(head);
 955	}
 956
 957	return 0;
 958}
 959EXPORT_SYMBOL_GPL(get_hwpoison_page);
 960
 961/*
 962 * Do all that is necessary to remove user space mappings. Unmap
 963 * the pages and send SIGBUS to the processes if the data was dirty.
 964 */
 965static bool hwpoison_user_mappings(struct page *p, unsigned long pfn,
 966				  int flags, struct page **hpagep)
 967{
 968	enum ttu_flags ttu = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
 969	struct address_space *mapping;
 970	LIST_HEAD(tokill);
 971	bool unmap_success;
 972	int kill = 1, forcekill;
 973	struct page *hpage = *hpagep;
 974	bool mlocked = PageMlocked(hpage);
 975
 976	/*
 977	 * Here we are interested only in user-mapped pages, so skip any
 978	 * other types of pages.
 979	 */
 980	if (PageReserved(p) || PageSlab(p))
 981		return true;
 982	if (!(PageLRU(hpage) || PageHuge(p)))
 983		return true;
 984
 985	/*
 986	 * This check implies we don't kill processes if their pages
 987	 * are in the swap cache early. Those are always late kills.
 988	 */
 989	if (!page_mapped(hpage))
 990		return true;
 991
 992	if (PageKsm(p)) {
 993		pr_err("Memory failure: %#lx: can't handle KSM pages.\n", pfn);
 994		return false;
 995	}
 996
 997	if (PageSwapCache(p)) {
 998		pr_err("Memory failure: %#lx: keeping poisoned page in swap cache\n",
 999			pfn);
1000		ttu |= TTU_IGNORE_HWPOISON;
1001	}
1002
1003	/*
1004	 * Propagate the dirty bit from PTEs to struct page first, because we
1005	 * need this to decide if we should kill or just drop the page.
1006	 * XXX: the dirty test could be racy: set_page_dirty() may not always
1007	 * be called inside page lock (it's recommended but not enforced).
1008	 */
1009	mapping = page_mapping(hpage);
1010	if (!(flags & MF_MUST_KILL) && !PageDirty(hpage) && mapping &&
1011	    mapping_cap_writeback_dirty(mapping)) {
1012		if (page_mkclean(hpage)) {
1013			SetPageDirty(hpage);
1014		} else {
1015			kill = 0;
1016			ttu |= TTU_IGNORE_HWPOISON;
1017			pr_info("Memory failure: %#lx: corrupted page was clean: dropped without side effects\n",
 
1018				pfn);
1019		}
1020	}
1021
1022	/*
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1023	 * First collect all the processes that have the page
1024	 * mapped in dirty form.  This has to be done before try_to_unmap,
1025	 * because ttu takes the rmap data structures down.
1026	 *
1027	 * Error handling: We ignore errors here because
1028	 * there's nothing that can be done.
1029	 */
1030	if (kill)
1031		collect_procs(hpage, &tokill, flags & MF_ACTION_REQUIRED);
1032
1033	unmap_success = try_to_unmap(hpage, ttu);
1034	if (!unmap_success)
1035		pr_err("Memory failure: %#lx: failed to unmap page (mapcount=%d)\n",
1036		       pfn, page_mapcount(hpage));
1037
1038	/*
1039	 * try_to_unmap() might put mlocked page in lru cache, so call
1040	 * shake_page() again to ensure that it's flushed.
1041	 */
1042	if (mlocked)
1043		shake_page(hpage, 0);
 
1044
1045	/*
1046	 * Now that the dirty bit has been propagated to the
1047	 * struct page and all unmaps done we can decide if
1048	 * killing is needed or not.  Only kill when the page
1049	 * was dirty or the process is not restartable,
1050	 * otherwise the tokill list is merely
1051	 * freed.  When there was a problem unmapping earlier
1052	 * use a more force-full uncatchable kill to prevent
1053	 * any accesses to the poisoned memory.
1054	 */
1055	forcekill = PageDirty(hpage) || (flags & MF_MUST_KILL);
1056	kill_procs(&tokill, forcekill, !unmap_success, pfn, flags);
1057
1058	return unmap_success;
1059}
1060
1061static int identify_page_state(unsigned long pfn, struct page *p,
1062				unsigned long page_flags)
1063{
1064	struct page_state *ps;
1065
1066	/*
1067	 * The first check uses the current page flags which may not have any
1068	 * relevant information. The second check with the saved page flags is
1069	 * carried out only if the first check can't determine the page status.
1070	 */
1071	for (ps = error_states;; ps++)
1072		if ((p->flags & ps->mask) == ps->res)
1073			break;
1074
1075	page_flags |= (p->flags & (1UL << PG_dirty));
1076
1077	if (!ps->mask)
1078		for (ps = error_states;; ps++)
1079			if ((page_flags & ps->mask) == ps->res)
1080				break;
1081	return page_action(ps, p, pfn);
1082}
1083
1084static int memory_failure_hugetlb(unsigned long pfn, int flags)
1085{
1086	struct page *p = pfn_to_page(pfn);
1087	struct page *head = compound_head(p);
1088	int res;
1089	unsigned long page_flags;
1090
1091	if (TestSetPageHWPoison(head)) {
1092		pr_err("Memory failure: %#lx: already hardware poisoned\n",
1093		       pfn);
1094		return 0;
1095	}
1096
1097	num_poisoned_pages_inc();
1098
1099	if (!(flags & MF_COUNT_INCREASED) && !get_hwpoison_page(p)) {
1100		/*
1101		 * Check "filter hit" and "race with other subpage."
1102		 */
1103		lock_page(head);
1104		if (PageHWPoison(head)) {
1105			if ((hwpoison_filter(p) && TestClearPageHWPoison(p))
1106			    || (p != head && TestSetPageHWPoison(head))) {
1107				num_poisoned_pages_dec();
1108				unlock_page(head);
1109				return 0;
1110			}
1111		}
1112		unlock_page(head);
1113		dissolve_free_huge_page(p);
1114		action_result(pfn, MF_MSG_FREE_HUGE, MF_DELAYED);
1115		return 0;
1116	}
1117
1118	lock_page(head);
1119	page_flags = head->flags;
1120
1121	if (!PageHWPoison(head)) {
1122		pr_err("Memory failure: %#lx: just unpoisoned\n", pfn);
1123		num_poisoned_pages_dec();
1124		unlock_page(head);
1125		put_hwpoison_page(head);
1126		return 0;
1127	}
1128
1129	/*
1130	 * TODO: hwpoison for pud-sized hugetlb doesn't work right now, so
1131	 * simply disable it. In order to make it work properly, we need
1132	 * make sure that:
1133	 *  - conversion of a pud that maps an error hugetlb into hwpoison
1134	 *    entry properly works, and
1135	 *  - other mm code walking over page table is aware of pud-aligned
1136	 *    hwpoison entries.
1137	 */
1138	if (huge_page_size(page_hstate(head)) > PMD_SIZE) {
1139		action_result(pfn, MF_MSG_NON_PMD_HUGE, MF_IGNORED);
1140		res = -EBUSY;
1141		goto out;
1142	}
1143
1144	if (!hwpoison_user_mappings(p, pfn, flags, &head)) {
1145		action_result(pfn, MF_MSG_UNMAP_FAILED, MF_IGNORED);
1146		res = -EBUSY;
1147		goto out;
1148	}
1149
1150	res = identify_page_state(pfn, p, page_flags);
1151out:
1152	unlock_page(head);
1153	return res;
1154}
1155
1156static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
1157		struct dev_pagemap *pgmap)
1158{
1159	struct page *page = pfn_to_page(pfn);
1160	const bool unmap_success = true;
1161	unsigned long size = 0;
1162	struct to_kill *tk;
1163	LIST_HEAD(tokill);
1164	int rc = -EBUSY;
1165	loff_t start;
1166	dax_entry_t cookie;
1167
1168	/*
1169	 * Prevent the inode from being freed while we are interrogating
1170	 * the address_space, typically this would be handled by
1171	 * lock_page(), but dax pages do not use the page lock. This
1172	 * also prevents changes to the mapping of this pfn until
1173	 * poison signaling is complete.
1174	 */
1175	cookie = dax_lock_page(page);
1176	if (!cookie)
1177		goto out;
1178
1179	if (hwpoison_filter(page)) {
1180		rc = 0;
1181		goto unlock;
1182	}
1183
1184	if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
1185		/*
1186		 * TODO: Handle HMM pages which may need coordination
1187		 * with device-side memory.
1188		 */
1189		goto unlock;
1190	}
1191
1192	/*
1193	 * Use this flag as an indication that the dax page has been
1194	 * remapped UC to prevent speculative consumption of poison.
1195	 */
1196	SetPageHWPoison(page);
1197
1198	/*
1199	 * Unlike System-RAM there is no possibility to swap in a
1200	 * different physical page at a given virtual address, so all
1201	 * userspace consumption of ZONE_DEVICE memory necessitates
1202	 * SIGBUS (i.e. MF_MUST_KILL)
1203	 */
1204	flags |= MF_ACTION_REQUIRED | MF_MUST_KILL;
1205	collect_procs(page, &tokill, flags & MF_ACTION_REQUIRED);
1206
1207	list_for_each_entry(tk, &tokill, nd)
1208		if (tk->size_shift)
1209			size = max(size, 1UL << tk->size_shift);
1210	if (size) {
1211		/*
1212		 * Unmap the largest mapping to avoid breaking up
1213		 * device-dax mappings which are constant size. The
1214		 * actual size of the mapping being torn down is
1215		 * communicated in siginfo, see kill_proc()
1216		 */
1217		start = (page->index << PAGE_SHIFT) & ~(size - 1);
1218		unmap_mapping_range(page->mapping, start, start + size, 0);
1219	}
1220	kill_procs(&tokill, flags & MF_MUST_KILL, !unmap_success, pfn, flags);
1221	rc = 0;
1222unlock:
1223	dax_unlock_page(page, cookie);
1224out:
1225	/* drop pgmap ref acquired in caller */
1226	put_dev_pagemap(pgmap);
1227	action_result(pfn, MF_MSG_DAX, rc ? MF_FAILED : MF_RECOVERED);
1228	return rc;
1229}
1230
1231/**
1232 * memory_failure - Handle memory failure of a page.
1233 * @pfn: Page Number of the corrupted page
1234 * @flags: fine tune action taken
1235 *
1236 * This function is called by the low level machine check code
1237 * of an architecture when it detects hardware memory corruption
1238 * of a page. It tries its best to recover, which includes
1239 * dropping pages, killing processes etc.
1240 *
1241 * The function is primarily of use for corruptions that
1242 * happen outside the current execution context (e.g. when
1243 * detected by a background scrubber)
1244 *
1245 * Must run in process context (e.g. a work queue) with interrupts
1246 * enabled and no spinlocks hold.
1247 */
1248int memory_failure(unsigned long pfn, int flags)
1249{
 
1250	struct page *p;
1251	struct page *hpage;
1252	struct page *orig_head;
1253	struct dev_pagemap *pgmap;
1254	int res;
1255	unsigned long page_flags;
1256
1257	if (!sysctl_memory_failure_recovery)
1258		panic("Memory failure on page %lx", pfn);
1259
1260	p = pfn_to_online_page(pfn);
1261	if (!p) {
1262		if (pfn_valid(pfn)) {
1263			pgmap = get_dev_pagemap(pfn, NULL);
1264			if (pgmap)
1265				return memory_failure_dev_pagemap(pfn, flags,
1266								  pgmap);
1267		}
1268		pr_err("Memory failure: %#lx: memory outside kernel control\n",
1269			pfn);
1270		return -ENXIO;
1271	}
1272
1273	if (PageHuge(p))
1274		return memory_failure_hugetlb(pfn, flags);
1275	if (TestSetPageHWPoison(p)) {
1276		pr_err("Memory failure: %#lx: already hardware poisoned\n",
1277			pfn);
1278		return 0;
1279	}
1280
1281	orig_head = hpage = compound_head(p);
1282	num_poisoned_pages_inc();
1283
1284	/*
1285	 * We need/can do nothing about count=0 pages.
1286	 * 1) it's a free page, and therefore in safe hand:
1287	 *    prep_new_page() will be the gate keeper.
1288	 * 2) it's part of a non-compound high order page.
 
 
 
1289	 *    Implies some kernel user: cannot stop them from
1290	 *    R/W the page; let's pray that the page has been
1291	 *    used and will be freed some time later.
1292	 * In fact it's dangerous to directly bump up page count from 0,
1293	 * that may make page_ref_freeze()/page_ref_unfreeze() mismatch.
1294	 */
1295	if (!(flags & MF_COUNT_INCREASED) && !get_hwpoison_page(p)) {
 
1296		if (is_free_buddy_page(p)) {
1297			action_result(pfn, MF_MSG_BUDDY, MF_DELAYED);
1298			return 0;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1299		} else {
1300			action_result(pfn, MF_MSG_KERNEL_HIGH_ORDER, MF_IGNORED);
1301			return -EBUSY;
1302		}
1303	}
1304
1305	if (PageTransHuge(hpage)) {
1306		lock_page(p);
1307		if (!PageAnon(p) || unlikely(split_huge_page(p))) {
1308			unlock_page(p);
1309			if (!PageAnon(p))
1310				pr_err("Memory failure: %#lx: non anonymous thp\n",
1311					pfn);
1312			else
1313				pr_err("Memory failure: %#lx: thp split failed\n",
1314					pfn);
1315			if (TestClearPageHWPoison(p))
1316				num_poisoned_pages_dec();
1317			put_hwpoison_page(p);
1318			return -EBUSY;
1319		}
1320		unlock_page(p);
1321		VM_BUG_ON_PAGE(!page_count(p), p);
1322		hpage = compound_head(p);
1323	}
1324
1325	/*
1326	 * We ignore non-LRU pages for good reasons.
1327	 * - PG_locked is only well defined for LRU pages and a few others
1328	 * - to avoid races with __SetPageLocked()
1329	 * - to avoid races with __SetPageSlab*() (and more non-atomic ops)
1330	 * The check (unnecessarily) ignores LRU pages being isolated and
1331	 * walked by the page reclaim code, however that's not a big loss.
1332	 */
1333	shake_page(p, 0);
1334	/* shake_page could have turned it free. */
1335	if (!PageLRU(p) && is_free_buddy_page(p)) {
1336		if (flags & MF_COUNT_INCREASED)
1337			action_result(pfn, MF_MSG_BUDDY, MF_DELAYED);
1338		else
1339			action_result(pfn, MF_MSG_BUDDY_2ND, MF_DELAYED);
1340		return 0;
1341	}
1342
1343	lock_page(p);
1344
1345	/*
1346	 * The page could have changed compound pages during the locking.
1347	 * If this happens just bail out.
1348	 */
1349	if (PageCompound(p) && compound_head(p) != orig_head) {
1350		action_result(pfn, MF_MSG_DIFFERENT_COMPOUND, MF_IGNORED);
1351		res = -EBUSY;
1352		goto out;
1353	}
1354
1355	/*
1356	 * We use page flags to determine what action should be taken, but
1357	 * the flags can be modified by the error containment action.  One
1358	 * example is an mlocked page, where PG_mlocked is cleared by
1359	 * page_remove_rmap() in try_to_unmap_one(). So to determine page status
1360	 * correctly, we save a copy of the page flags at this time.
1361	 */
1362	if (PageHuge(p))
1363		page_flags = hpage->flags;
1364	else
1365		page_flags = p->flags;
1366
1367	/*
1368	 * unpoison always clear PG_hwpoison inside page lock
1369	 */
1370	if (!PageHWPoison(p)) {
1371		pr_err("Memory failure: %#lx: just unpoisoned\n", pfn);
1372		num_poisoned_pages_dec();
1373		unlock_page(p);
1374		put_hwpoison_page(p);
1375		return 0;
1376	}
1377	if (hwpoison_filter(p)) {
1378		if (TestClearPageHWPoison(p))
1379			num_poisoned_pages_dec();
1380		unlock_page(p);
1381		put_hwpoison_page(p);
1382		return 0;
1383	}
1384
1385	if (!PageTransTail(p) && !PageLRU(p))
1386		goto identify_page_state;
1387
1388	/*
1389	 * It's very difficult to mess with pages currently under IO
1390	 * and in many cases impossible, so we just avoid it here.
 
 
 
 
 
 
 
 
 
 
 
 
 
1391	 */
 
 
 
1392	wait_on_page_writeback(p);
1393
1394	/*
1395	 * Now take care of user space mappings.
1396	 * Abort on fail: __delete_from_page_cache() assumes unmapped page.
1397	 *
1398	 * When the raw error page is thp tail page, hpage points to the raw
1399	 * page after thp split.
1400	 */
1401	if (!hwpoison_user_mappings(p, pfn, flags, &hpage)) {
1402		action_result(pfn, MF_MSG_UNMAP_FAILED, MF_IGNORED);
1403		res = -EBUSY;
1404		goto out;
1405	}
1406
1407	/*
1408	 * Torn down by someone else?
1409	 */
1410	if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) {
1411		action_result(pfn, MF_MSG_TRUNCATED_LRU, MF_IGNORED);
1412		res = -EBUSY;
1413		goto out;
1414	}
1415
1416identify_page_state:
1417	res = identify_page_state(pfn, p, page_flags);
 
 
 
 
 
1418out:
1419	unlock_page(p);
1420	return res;
1421}
1422EXPORT_SYMBOL_GPL(memory_failure);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1423
1424#define MEMORY_FAILURE_FIFO_ORDER	4
1425#define MEMORY_FAILURE_FIFO_SIZE	(1 << MEMORY_FAILURE_FIFO_ORDER)
1426
1427struct memory_failure_entry {
1428	unsigned long pfn;
 
1429	int flags;
1430};
1431
1432struct memory_failure_cpu {
1433	DECLARE_KFIFO(fifo, struct memory_failure_entry,
1434		      MEMORY_FAILURE_FIFO_SIZE);
1435	spinlock_t lock;
1436	struct work_struct work;
1437};
1438
1439static DEFINE_PER_CPU(struct memory_failure_cpu, memory_failure_cpu);
1440
1441/**
1442 * memory_failure_queue - Schedule handling memory failure of a page.
1443 * @pfn: Page Number of the corrupted page
 
1444 * @flags: Flags for memory failure handling
1445 *
1446 * This function is called by the low level hardware error handler
1447 * when it detects hardware memory corruption of a page. It schedules
1448 * the recovering of error page, including dropping pages, killing
1449 * processes etc.
1450 *
1451 * The function is primarily of use for corruptions that
1452 * happen outside the current execution context (e.g. when
1453 * detected by a background scrubber)
1454 *
1455 * Can run in IRQ context.
1456 */
1457void memory_failure_queue(unsigned long pfn, int flags)
1458{
1459	struct memory_failure_cpu *mf_cpu;
1460	unsigned long proc_flags;
1461	struct memory_failure_entry entry = {
1462		.pfn =		pfn,
 
1463		.flags =	flags,
1464	};
1465
1466	mf_cpu = &get_cpu_var(memory_failure_cpu);
1467	spin_lock_irqsave(&mf_cpu->lock, proc_flags);
1468	if (kfifo_put(&mf_cpu->fifo, entry))
1469		schedule_work_on(smp_processor_id(), &mf_cpu->work);
1470	else
1471		pr_err("Memory failure: buffer overflow when queuing memory failure at %#lx\n",
1472		       pfn);
1473	spin_unlock_irqrestore(&mf_cpu->lock, proc_flags);
1474	put_cpu_var(memory_failure_cpu);
1475}
1476EXPORT_SYMBOL_GPL(memory_failure_queue);
1477
1478static void memory_failure_work_func(struct work_struct *work)
1479{
1480	struct memory_failure_cpu *mf_cpu;
1481	struct memory_failure_entry entry = { 0, };
1482	unsigned long proc_flags;
1483	int gotten;
1484
1485	mf_cpu = this_cpu_ptr(&memory_failure_cpu);
1486	for (;;) {
1487		spin_lock_irqsave(&mf_cpu->lock, proc_flags);
1488		gotten = kfifo_get(&mf_cpu->fifo, &entry);
1489		spin_unlock_irqrestore(&mf_cpu->lock, proc_flags);
1490		if (!gotten)
1491			break;
1492		if (entry.flags & MF_SOFT_OFFLINE)
1493			soft_offline_page(pfn_to_page(entry.pfn), entry.flags);
1494		else
1495			memory_failure(entry.pfn, entry.flags);
1496	}
1497}
1498
1499static int __init memory_failure_init(void)
1500{
1501	struct memory_failure_cpu *mf_cpu;
1502	int cpu;
1503
1504	for_each_possible_cpu(cpu) {
1505		mf_cpu = &per_cpu(memory_failure_cpu, cpu);
1506		spin_lock_init(&mf_cpu->lock);
1507		INIT_KFIFO(mf_cpu->fifo);
1508		INIT_WORK(&mf_cpu->work, memory_failure_work_func);
1509	}
1510
1511	return 0;
1512}
1513core_initcall(memory_failure_init);
1514
1515#define unpoison_pr_info(fmt, pfn, rs)			\
1516({							\
1517	if (__ratelimit(rs))				\
1518		pr_info(fmt, pfn);			\
1519})
1520
1521/**
1522 * unpoison_memory - Unpoison a previously poisoned page
1523 * @pfn: Page number of the to be unpoisoned page
1524 *
1525 * Software-unpoison a page that has been poisoned by
1526 * memory_failure() earlier.
1527 *
1528 * This is only done on the software-level, so it only works
1529 * for linux injected failures, not real hardware failures
1530 *
1531 * Returns 0 for success, otherwise -errno.
1532 */
1533int unpoison_memory(unsigned long pfn)
1534{
1535	struct page *page;
1536	struct page *p;
1537	int freeit = 0;
1538	static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL,
1539					DEFAULT_RATELIMIT_BURST);
1540
1541	if (!pfn_valid(pfn))
1542		return -ENXIO;
1543
1544	p = pfn_to_page(pfn);
1545	page = compound_head(p);
1546
1547	if (!PageHWPoison(p)) {
1548		unpoison_pr_info("Unpoison: Page was already unpoisoned %#lx\n",
1549				 pfn, &unpoison_rs);
1550		return 0;
1551	}
1552
1553	if (page_count(page) > 1) {
1554		unpoison_pr_info("Unpoison: Someone grabs the hwpoison page %#lx\n",
1555				 pfn, &unpoison_rs);
1556		return 0;
1557	}
1558
1559	if (page_mapped(page)) {
1560		unpoison_pr_info("Unpoison: Someone maps the hwpoison page %#lx\n",
1561				 pfn, &unpoison_rs);
1562		return 0;
1563	}
1564
1565	if (page_mapping(page)) {
1566		unpoison_pr_info("Unpoison: the hwpoison page has non-NULL mapping %#lx\n",
1567				 pfn, &unpoison_rs);
1568		return 0;
1569	}
1570
1571	/*
1572	 * unpoison_memory() can encounter thp only when the thp is being
1573	 * worked by memory_failure() and the page lock is not held yet.
1574	 * In such case, we yield to memory_failure() and make unpoison fail.
1575	 */
1576	if (!PageHuge(page) && PageTransHuge(page)) {
1577		unpoison_pr_info("Unpoison: Memory failure is now running on %#lx\n",
1578				 pfn, &unpoison_rs);
1579		return 0;
1580	}
1581
1582	if (!get_hwpoison_page(p)) {
1583		if (TestClearPageHWPoison(p))
1584			num_poisoned_pages_dec();
1585		unpoison_pr_info("Unpoison: Software-unpoisoned free page %#lx\n",
1586				 pfn, &unpoison_rs);
1587		return 0;
1588	}
1589
1590	lock_page(page);
1591	/*
1592	 * This test is racy because PG_hwpoison is set outside of page lock.
1593	 * That's acceptable because that won't trigger kernel panic. Instead,
1594	 * the PG_hwpoison page will be caught and isolated on the entrance to
1595	 * the free buddy page pool.
1596	 */
1597	if (TestClearPageHWPoison(page)) {
1598		unpoison_pr_info("Unpoison: Software-unpoisoned page %#lx\n",
1599				 pfn, &unpoison_rs);
1600		num_poisoned_pages_dec();
1601		freeit = 1;
 
 
1602	}
1603	unlock_page(page);
1604
1605	put_hwpoison_page(page);
1606	if (freeit && !(pfn == my_zero_pfn(0) && page_count(p) == 1))
1607		put_hwpoison_page(page);
1608
1609	return 0;
1610}
1611EXPORT_SYMBOL(unpoison_memory);
1612
1613static struct page *new_page(struct page *p, unsigned long private)
1614{
1615	int nid = page_to_nid(p);
1616
1617	return new_page_nodemask(p, nid, &node_states[N_MEMORY]);
 
 
 
1618}
1619
1620/*
1621 * Safely get reference count of an arbitrary page.
1622 * Returns 0 for a free page, -EIO for a zero refcount page
1623 * that is not free, and 1 for any other page type.
1624 * For 1 the page is returned with increased page count, otherwise not.
1625 */
1626static int __get_any_page(struct page *p, unsigned long pfn, int flags)
1627{
1628	int ret;
1629
1630	if (flags & MF_COUNT_INCREASED)
1631		return 1;
1632
1633	/*
 
 
 
 
 
 
 
 
 
 
 
1634	 * When the target page is a free hugepage, just remove it
1635	 * from free hugepage list.
1636	 */
1637	if (!get_hwpoison_page(p)) {
1638		if (PageHuge(p)) {
1639			pr_info("%s: %#lx free huge page\n", __func__, pfn);
1640			ret = 0;
1641		} else if (is_free_buddy_page(p)) {
1642			pr_info("%s: %#lx free buddy page\n", __func__, pfn);
 
 
1643			ret = 0;
1644		} else {
1645			pr_info("%s: %#lx: unknown zero refcount page type %lx\n",
1646				__func__, pfn, p->flags);
1647			ret = -EIO;
1648		}
1649	} else {
1650		/* Not a free page */
1651		ret = 1;
1652	}
1653	return ret;
1654}
1655
1656static int get_any_page(struct page *page, unsigned long pfn, int flags)
1657{
1658	int ret = __get_any_page(page, pfn, flags);
1659
1660	if (ret == 1 && !PageHuge(page) &&
1661	    !PageLRU(page) && !__PageMovable(page)) {
1662		/*
1663		 * Try to free it.
1664		 */
1665		put_hwpoison_page(page);
1666		shake_page(page, 1);
1667
1668		/*
1669		 * Did it turn free?
1670		 */
1671		ret = __get_any_page(page, pfn, 0);
1672		if (ret == 1 && !PageLRU(page)) {
1673			/* Drop page reference which is from __get_any_page() */
1674			put_hwpoison_page(page);
1675			pr_info("soft_offline: %#lx: unknown non LRU page type %lx (%pGp)\n",
1676				pfn, page->flags, &page->flags);
1677			return -EIO;
1678		}
1679	}
1680	return ret;
1681}
1682
1683static int soft_offline_huge_page(struct page *page, int flags)
1684{
1685	int ret;
1686	unsigned long pfn = page_to_pfn(page);
1687	struct page *hpage = compound_head(page);
1688	LIST_HEAD(pagelist);
1689
1690	/*
1691	 * This double-check of PageHWPoison is to avoid the race with
1692	 * memory_failure(). See also comment in __soft_offline_page().
1693	 */
1694	lock_page(hpage);
 
1695	if (PageHWPoison(hpage)) {
1696		unlock_page(hpage);
1697		put_hwpoison_page(hpage);
1698		pr_info("soft offline: %#lx hugepage already poisoned\n", pfn);
1699		return -EBUSY;
1700	}
1701	unlock_page(hpage);
1702
1703	ret = isolate_huge_page(hpage, &pagelist);
1704	/*
1705	 * get_any_page() and isolate_huge_page() takes a refcount each,
1706	 * so need to drop one here.
1707	 */
1708	put_hwpoison_page(hpage);
1709	if (!ret) {
1710		pr_info("soft offline: %#lx hugepage failed to isolate\n", pfn);
1711		return -EBUSY;
1712	}
1713
1714	ret = migrate_pages(&pagelist, new_page, NULL, MPOL_MF_MOVE_ALL,
1715				MIGRATE_SYNC, MR_MEMORY_FAILURE);
 
1716	if (ret) {
1717		pr_info("soft offline: %#lx: hugepage migration failed %d, type %lx (%pGp)\n",
1718			pfn, ret, page->flags, &page->flags);
1719		if (!list_empty(&pagelist))
1720			putback_movable_pages(&pagelist);
 
 
1721		if (ret > 0)
1722			ret = -EIO;
1723	} else {
1724		/*
1725		 * We set PG_hwpoison only when the migration source hugepage
1726		 * was successfully dissolved, because otherwise hwpoisoned
1727		 * hugepage remains on free hugepage list, then userspace will
1728		 * find it as SIGBUS by allocation failure. That's not expected
1729		 * in soft-offlining.
1730		 */
1731		ret = dissolve_free_huge_page(page);
1732		if (!ret) {
1733			if (set_hwpoison_free_buddy_page(page))
1734				num_poisoned_pages_inc();
1735			else
1736				ret = -EBUSY;
1737		}
1738	}
 
 
 
 
 
 
1739	return ret;
1740}
1741
1742static int __soft_offline_page(struct page *page, int flags)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1743{
1744	int ret;
1745	unsigned long pfn = page_to_pfn(page);
1746
 
 
 
 
 
 
 
 
 
1747	/*
1748	 * Check PageHWPoison again inside page lock because PageHWPoison
1749	 * is set by memory_failure() outside page lock. Note that
1750	 * memory_failure() also double-checks PageHWPoison inside page lock,
1751	 * so there's no race between soft_offline_page() and memory_failure().
1752	 */
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1753	lock_page(page);
1754	wait_on_page_writeback(page);
 
 
 
 
1755	if (PageHWPoison(page)) {
1756		unlock_page(page);
1757		put_hwpoison_page(page);
1758		pr_info("soft offline: %#lx page already poisoned\n", pfn);
1759		return -EBUSY;
1760	}
 
1761	/*
1762	 * Try to invalidate first. This should work for
1763	 * non dirty unmapped page cache pages.
1764	 */
1765	ret = invalidate_inode_page(page);
1766	unlock_page(page);
1767	/*
1768	 * RED-PEN would be better to keep it isolated here, but we
1769	 * would need to fix isolation locking first.
1770	 */
1771	if (ret == 1) {
1772		put_hwpoison_page(page);
 
1773		pr_info("soft_offline: %#lx: invalidated\n", pfn);
1774		SetPageHWPoison(page);
1775		num_poisoned_pages_inc();
1776		return 0;
1777	}
1778
1779	/*
1780	 * Simple invalidation didn't work.
1781	 * Try to migrate to a new page instead. migrate.c
1782	 * handles a large number of cases for us.
1783	 */
1784	if (PageLRU(page))
1785		ret = isolate_lru_page(page);
1786	else
1787		ret = isolate_movable_page(page, ISOLATE_UNEVICTABLE);
1788	/*
1789	 * Drop page reference which is came from get_any_page()
1790	 * successful isolate_lru_page() already took another one.
1791	 */
1792	put_hwpoison_page(page);
1793	if (!ret) {
1794		LIST_HEAD(pagelist);
1795		/*
1796		 * After isolated lru page, the PageLRU will be cleared,
1797		 * so use !__PageMovable instead for LRU page's mapping
1798		 * cannot have PAGE_MAPPING_MOVABLE.
1799		 */
1800		if (!__PageMovable(page))
1801			inc_node_page_state(page, NR_ISOLATED_ANON +
1802						page_is_file_cache(page));
1803		list_add(&page->lru, &pagelist);
1804		ret = migrate_pages(&pagelist, new_page, NULL, MPOL_MF_MOVE_ALL,
1805					MIGRATE_SYNC, MR_MEMORY_FAILURE);
1806		if (ret) {
1807			if (!list_empty(&pagelist))
1808				putback_movable_pages(&pagelist);
1809
1810			pr_info("soft offline: %#lx: migration failed %d, type %lx (%pGp)\n",
1811				pfn, ret, page->flags, &page->flags);
1812			if (ret > 0)
1813				ret = -EIO;
1814		}
1815	} else {
1816		pr_info("soft offline: %#lx: isolation failed: %d, page count %d, type %lx (%pGp)\n",
1817			pfn, ret, page_count(page), page->flags, &page->flags);
1818	}
1819	return ret;
1820}
1821
1822static int soft_offline_in_use_page(struct page *page, int flags)
1823{
1824	int ret;
1825	int mt;
1826	struct page *hpage = compound_head(page);
1827
1828	if (!PageHuge(page) && PageTransHuge(hpage)) {
1829		lock_page(page);
1830		if (!PageAnon(page) || unlikely(split_huge_page(page))) {
1831			unlock_page(page);
1832			if (!PageAnon(page))
1833				pr_info("soft offline: %#lx: non anonymous thp\n", page_to_pfn(page));
1834			else
1835				pr_info("soft offline: %#lx: thp split failed\n", page_to_pfn(page));
1836			put_hwpoison_page(page);
1837			return -EBUSY;
1838		}
1839		unlock_page(page);
1840	}
1841
1842	/*
1843	 * Setting MIGRATE_ISOLATE here ensures that the page will be linked
1844	 * to free list immediately (not via pcplist) when released after
1845	 * successful page migration. Otherwise we can't guarantee that the
1846	 * page is really free after put_page() returns, so
1847	 * set_hwpoison_free_buddy_page() highly likely fails.
1848	 */
1849	mt = get_pageblock_migratetype(page);
1850	set_pageblock_migratetype(page, MIGRATE_ISOLATE);
1851	if (PageHuge(page))
1852		ret = soft_offline_huge_page(page, flags);
1853	else
1854		ret = __soft_offline_page(page, flags);
1855	set_pageblock_migratetype(page, mt);
1856	return ret;
1857}
1858
1859static int soft_offline_free_page(struct page *page)
1860{
1861	int rc = dissolve_free_huge_page(page);
1862
1863	if (!rc) {
1864		if (set_hwpoison_free_buddy_page(page))
1865			num_poisoned_pages_inc();
1866		else
1867			rc = -EBUSY;
1868	}
1869	return rc;
1870}
1871
1872/**
1873 * soft_offline_page - Soft offline a page.
1874 * @page: page to offline
1875 * @flags: flags. Same as memory_failure().
1876 *
1877 * Returns 0 on success, otherwise negated errno.
1878 *
1879 * Soft offline a page, by migration or invalidation,
1880 * without killing anything. This is for the case when
1881 * a page is not corrupted yet (so it's still valid to access),
1882 * but has had a number of corrected errors and is better taken
1883 * out.
1884 *
1885 * The actual policy on when to do that is maintained by
1886 * user space.
1887 *
1888 * This should never impact any application or cause data loss,
1889 * however it might take some time.
1890 *
1891 * This is not a 100% solution for all memory, but tries to be
1892 * ``good enough'' for the majority of memory.
1893 */
1894int soft_offline_page(struct page *page, int flags)
1895{
1896	int ret;
1897	unsigned long pfn = page_to_pfn(page);
1898
1899	if (is_zone_device_page(page)) {
1900		pr_debug_ratelimited("soft_offline: %#lx page is device page\n",
1901				pfn);
1902		if (flags & MF_COUNT_INCREASED)
1903			put_page(page);
1904		return -EIO;
1905	}
1906
1907	if (PageHWPoison(page)) {
1908		pr_info("soft offline: %#lx page already poisoned\n", pfn);
1909		if (flags & MF_COUNT_INCREASED)
1910			put_hwpoison_page(page);
1911		return -EBUSY;
1912	}
1913
1914	get_online_mems();
1915	ret = get_any_page(page, pfn, flags);
1916	put_online_mems();
1917
1918	if (ret > 0)
1919		ret = soft_offline_in_use_page(page, flags);
1920	else if (ret == 0)
1921		ret = soft_offline_free_page(page);
1922
 
 
 
 
1923	return ret;
1924}