linux/mm/memory-failure.c
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   1/*
   2 * Copyright (C) 2008, 2009 Intel Corporation
   3 * Authors: Andi Kleen, Fengguang Wu
   4 *
   5 * This software may be redistributed and/or modified under the terms of
   6 * the GNU General Public License ("GPL") version 2 only as published by the
   7 * Free Software Foundation.
   8 *
   9 * High level machine check handler. Handles pages reported by the
  10 * hardware as being corrupted usually due to a multi-bit ECC memory or cache
  11 * failure.
  12 * 
  13 * In addition there is a "soft offline" entry point that allows stop using
  14 * not-yet-corrupted-by-suspicious pages without killing anything.
  15 *
  16 * Handles page cache pages in various states.  The tricky part
  17 * here is that we can access any page asynchronously in respect to 
  18 * other VM users, because memory failures could happen anytime and 
  19 * anywhere. This could violate some of their assumptions. This is why 
  20 * this code has to be extremely careful. Generally it tries to use 
  21 * normal locking rules, as in get the standard locks, even if that means 
  22 * the error handling takes potentially a long time.
  23 * 
  24 * There are several operations here with exponential complexity because
  25 * of unsuitable VM data structures. For example the operation to map back 
  26 * from RMAP chains to processes has to walk the complete process list and 
  27 * has non linear complexity with the number. But since memory corruptions
  28 * are rare we hope to get away with this. This avoids impacting the core 
  29 * VM.
  30 */
  31
  32/*
  33 * Notebook:
  34 * - hugetlb needs more code
  35 * - kcore/oldmem/vmcore/mem/kmem check for hwpoison pages
  36 * - pass bad pages to kdump next kernel
  37 */
  38#include <linux/kernel.h>
  39#include <linux/mm.h>
  40#include <linux/page-flags.h>
  41#include <linux/kernel-page-flags.h>
  42#include <linux/sched.h>
  43#include <linux/ksm.h>
  44#include <linux/rmap.h>
  45#include <linux/pagemap.h>
  46#include <linux/swap.h>
  47#include <linux/backing-dev.h>
  48#include <linux/migrate.h>
  49#include <linux/page-isolation.h>
  50#include <linux/suspend.h>
  51#include <linux/slab.h>
  52#include <linux/swapops.h>
  53#include <linux/hugetlb.h>
  54#include <linux/memory_hotplug.h>
  55#include <linux/mm_inline.h>
  56#include <linux/kfifo.h>
  57#include "internal.h"
  58
  59int sysctl_memory_failure_early_kill __read_mostly = 0;
  60
  61int sysctl_memory_failure_recovery __read_mostly = 1;
  62
  63atomic_long_t mce_bad_pages __read_mostly = ATOMIC_LONG_INIT(0);
  64
  65#if defined(CONFIG_HWPOISON_INJECT) || defined(CONFIG_HWPOISON_INJECT_MODULE)
  66
  67u32 hwpoison_filter_enable = 0;
  68u32 hwpoison_filter_dev_major = ~0U;
  69u32 hwpoison_filter_dev_minor = ~0U;
  70u64 hwpoison_filter_flags_mask;
  71u64 hwpoison_filter_flags_value;
  72EXPORT_SYMBOL_GPL(hwpoison_filter_enable);
  73EXPORT_SYMBOL_GPL(hwpoison_filter_dev_major);
  74EXPORT_SYMBOL_GPL(hwpoison_filter_dev_minor);
  75EXPORT_SYMBOL_GPL(hwpoison_filter_flags_mask);
  76EXPORT_SYMBOL_GPL(hwpoison_filter_flags_value);
  77
  78static int hwpoison_filter_dev(struct page *p)
  79{
  80        struct address_space *mapping;
  81        dev_t dev;
  82
  83        if (hwpoison_filter_dev_major == ~0U &&
  84            hwpoison_filter_dev_minor == ~0U)
  85                return 0;
  86
  87        /*
  88         * page_mapping() does not accept slab pages.
  89         */
  90        if (PageSlab(p))
  91                return -EINVAL;
  92
  93        mapping = page_mapping(p);
  94        if (mapping == NULL || mapping->host == NULL)
  95                return -EINVAL;
  96
  97        dev = mapping->host->i_sb->s_dev;
  98        if (hwpoison_filter_dev_major != ~0U &&
  99            hwpoison_filter_dev_major != MAJOR(dev))
 100                return -EINVAL;
 101        if (hwpoison_filter_dev_minor != ~0U &&
 102            hwpoison_filter_dev_minor != MINOR(dev))
 103                return -EINVAL;
 104
 105        return 0;
 106}
 107
 108static int hwpoison_filter_flags(struct page *p)
 109{
 110        if (!hwpoison_filter_flags_mask)
 111                return 0;
 112
 113        if ((stable_page_flags(p) & hwpoison_filter_flags_mask) ==
 114                                    hwpoison_filter_flags_value)
 115                return 0;
 116        else
 117                return -EINVAL;
 118}
 119
 120/*
 121 * This allows stress tests to limit test scope to a collection of tasks
 122 * by putting them under some memcg. This prevents killing unrelated/important
 123 * processes such as /sbin/init. Note that the target task may share clean
 124 * pages with init (eg. libc text), which is harmless. If the target task
 125 * share _dirty_ pages with another task B, the test scheme must make sure B
 126 * is also included in the memcg. At last, due to race conditions this filter
 127 * can only guarantee that the page either belongs to the memcg tasks, or is
 128 * a freed page.
 129 */
 130#ifdef  CONFIG_CGROUP_MEM_RES_CTLR_SWAP
 131u64 hwpoison_filter_memcg;
 132EXPORT_SYMBOL_GPL(hwpoison_filter_memcg);
 133static int hwpoison_filter_task(struct page *p)
 134{
 135        struct mem_cgroup *mem;
 136        struct cgroup_subsys_state *css;
 137        unsigned long ino;
 138
 139        if (!hwpoison_filter_memcg)
 140                return 0;
 141
 142        mem = try_get_mem_cgroup_from_page(p);
 143        if (!mem)
 144                return -EINVAL;
 145
 146        css = mem_cgroup_css(mem);
 147        /* root_mem_cgroup has NULL dentries */
 148        if (!css->cgroup->dentry)
 149                return -EINVAL;
 150
 151        ino = css->cgroup->dentry->d_inode->i_ino;
 152        css_put(css);
 153
 154        if (ino != hwpoison_filter_memcg)
 155                return -EINVAL;
 156
 157        return 0;
 158}
 159#else
 160static int hwpoison_filter_task(struct page *p) { return 0; }
 161#endif
 162
 163int hwpoison_filter(struct page *p)
 164{
 165        if (!hwpoison_filter_enable)
 166                return 0;
 167
 168        if (hwpoison_filter_dev(p))
 169                return -EINVAL;
 170
 171        if (hwpoison_filter_flags(p))
 172                return -EINVAL;
 173
 174        if (hwpoison_filter_task(p))
 175                return -EINVAL;
 176
 177        return 0;
 178}
 179#else
 180int hwpoison_filter(struct page *p)
 181{
 182        return 0;
 183}
 184#endif
 185
 186EXPORT_SYMBOL_GPL(hwpoison_filter);
 187
 188/*
 189 * Send all the processes who have the page mapped an ``action optional''
 190 * signal.
 191 */
 192static int kill_proc_ao(struct task_struct *t, unsigned long addr, int trapno,
 193                        unsigned long pfn, struct page *page)
 194{
 195        struct siginfo si;
 196        int ret;
 197
 198        printk(KERN_ERR
 199                "MCE %#lx: Killing %s:%d early due to hardware memory corruption\n",
 200                pfn, t->comm, t->pid);
 201        si.si_signo = SIGBUS;
 202        si.si_errno = 0;
 203        si.si_code = BUS_MCEERR_AO;
 204        si.si_addr = (void *)addr;
 205#ifdef __ARCH_SI_TRAPNO
 206        si.si_trapno = trapno;
 207#endif
 208        si.si_addr_lsb = compound_trans_order(compound_head(page)) + PAGE_SHIFT;
 209        /*
 210         * Don't use force here, it's convenient if the signal
 211         * can be temporarily blocked.
 212         * This could cause a loop when the user sets SIGBUS
 213         * to SIG_IGN, but hopefully no one will do that?
 214         */
 215        ret = send_sig_info(SIGBUS, &si, t);  /* synchronous? */
 216        if (ret < 0)
 217                printk(KERN_INFO "MCE: Error sending signal to %s:%d: %d\n",
 218                       t->comm, t->pid, ret);
 219        return ret;
 220}
 221
 222/*
 223 * When a unknown page type is encountered drain as many buffers as possible
 224 * in the hope to turn the page into a LRU or free page, which we can handle.
 225 */
 226void shake_page(struct page *p, int access)
 227{
 228        if (!PageSlab(p)) {
 229                lru_add_drain_all();
 230                if (PageLRU(p))
 231                        return;
 232                drain_all_pages();
 233                if (PageLRU(p) || is_free_buddy_page(p))
 234                        return;
 235        }
 236
 237        /*
 238         * Only call shrink_slab here (which would also shrink other caches) if
 239         * access is not potentially fatal.
 240         */
 241        if (access) {
 242                int nr;
 243                do {
 244                        struct shrink_control shrink = {
 245                                .gfp_mask = GFP_KERNEL,
 246                        };
 247
 248                        nr = shrink_slab(&shrink, 1000, 1000);
 249                        if (page_count(p) == 1)
 250                                break;
 251                } while (nr > 10);
 252        }
 253}
 254EXPORT_SYMBOL_GPL(shake_page);
 255
 256/*
 257 * Kill all processes that have a poisoned page mapped and then isolate
 258 * the page.
 259 *
 260 * General strategy:
 261 * Find all processes having the page mapped and kill them.
 262 * But we keep a page reference around so that the page is not
 263 * actually freed yet.
 264 * Then stash the page away
 265 *
 266 * There's no convenient way to get back to mapped processes
 267 * from the VMAs. So do a brute-force search over all
 268 * running processes.
 269 *
 270 * Remember that machine checks are not common (or rather
 271 * if they are common you have other problems), so this shouldn't
 272 * be a performance issue.
 273 *
 274 * Also there are some races possible while we get from the
 275 * error detection to actually handle it.
 276 */
 277
 278struct to_kill {
 279        struct list_head nd;
 280        struct task_struct *tsk;
 281        unsigned long addr;
 282        char addr_valid;
 283};
 284
 285/*
 286 * Failure handling: if we can't find or can't kill a process there's
 287 * not much we can do.  We just print a message and ignore otherwise.
 288 */
 289
 290/*
 291 * Schedule a process for later kill.
 292 * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
 293 * TBD would GFP_NOIO be enough?
 294 */
 295static void add_to_kill(struct task_struct *tsk, struct page *p,
 296                       struct vm_area_struct *vma,
 297                       struct list_head *to_kill,
 298                       struct to_kill **tkc)
 299{
 300        struct to_kill *tk;
 301
 302        if (*tkc) {
 303                tk = *tkc;
 304                *tkc = NULL;
 305        } else {
 306                tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
 307                if (!tk) {
 308                        printk(KERN_ERR
 309                "MCE: Out of memory while machine check handling\n");
 310                        return;
 311                }
 312        }
 313        tk->addr = page_address_in_vma(p, vma);
 314        tk->addr_valid = 1;
 315
 316        /*
 317         * In theory we don't have to kill when the page was
 318         * munmaped. But it could be also a mremap. Since that's
 319         * likely very rare kill anyways just out of paranoia, but use
 320         * a SIGKILL because the error is not contained anymore.
 321         */
 322        if (tk->addr == -EFAULT) {
 323                pr_info("MCE: Unable to find user space address %lx in %s\n",
 324                        page_to_pfn(p), tsk->comm);
 325                tk->addr_valid = 0;
 326        }
 327        get_task_struct(tsk);
 328        tk->tsk = tsk;
 329        list_add_tail(&tk->nd, to_kill);
 330}
 331
 332/*
 333 * Kill the processes that have been collected earlier.
 334 *
 335 * Only do anything when DOIT is set, otherwise just free the list
 336 * (this is used for clean pages which do not need killing)
 337 * Also when FAIL is set do a force kill because something went
 338 * wrong earlier.
 339 */
 340static void kill_procs_ao(struct list_head *to_kill, int doit, int trapno,
 341                          int fail, struct page *page, unsigned long pfn)
 342{
 343        struct to_kill *tk, *next;
 344
 345        list_for_each_entry_safe (tk, next, to_kill, nd) {
 346                if (doit) {
 347                        /*
 348                         * In case something went wrong with munmapping
 349                         * make sure the process doesn't catch the
 350                         * signal and then access the memory. Just kill it.
 351                         */
 352                        if (fail || tk->addr_valid == 0) {
 353                                printk(KERN_ERR
 354                "MCE %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n",
 355                                        pfn, tk->tsk->comm, tk->tsk->pid);
 356                                force_sig(SIGKILL, tk->tsk);
 357                        }
 358
 359                        /*
 360                         * In theory the process could have mapped
 361                         * something else on the address in-between. We could
 362                         * check for that, but we need to tell the
 363                         * process anyways.
 364                         */
 365                        else if (kill_proc_ao(tk->tsk, tk->addr, trapno,
 366                                              pfn, page) < 0)
 367                                printk(KERN_ERR
 368                "MCE %#lx: Cannot send advisory machine check signal to %s:%d\n",
 369                                        pfn, tk->tsk->comm, tk->tsk->pid);
 370                }
 371                put_task_struct(tk->tsk);
 372                kfree(tk);
 373        }
 374}
 375
 376static int task_early_kill(struct task_struct *tsk)
 377{
 378        if (!tsk->mm)
 379                return 0;
 380        if (tsk->flags & PF_MCE_PROCESS)
 381                return !!(tsk->flags & PF_MCE_EARLY);
 382        return sysctl_memory_failure_early_kill;
 383}
 384
 385/*
 386 * Collect processes when the error hit an anonymous page.
 387 */
 388static void collect_procs_anon(struct page *page, struct list_head *to_kill,
 389                              struct to_kill **tkc)
 390{
 391        struct vm_area_struct *vma;
 392        struct task_struct *tsk;
 393        struct anon_vma *av;
 394
 395        av = page_lock_anon_vma(page);
 396        if (av == NULL) /* Not actually mapped anymore */
 397                return;
 398
 399        read_lock(&tasklist_lock);
 400        for_each_process (tsk) {
 401                struct anon_vma_chain *vmac;
 402
 403                if (!task_early_kill(tsk))
 404                        continue;
 405                list_for_each_entry(vmac, &av->head, same_anon_vma) {
 406                        vma = vmac->vma;
 407                        if (!page_mapped_in_vma(page, vma))
 408                                continue;
 409                        if (vma->vm_mm == tsk->mm)
 410                                add_to_kill(tsk, page, vma, to_kill, tkc);
 411                }
 412        }
 413        read_unlock(&tasklist_lock);
 414        page_unlock_anon_vma(av);
 415}
 416
 417/*
 418 * Collect processes when the error hit a file mapped page.
 419 */
 420static void collect_procs_file(struct page *page, struct list_head *to_kill,
 421                              struct to_kill **tkc)
 422{
 423        struct vm_area_struct *vma;
 424        struct task_struct *tsk;
 425        struct prio_tree_iter iter;
 426        struct address_space *mapping = page->mapping;
 427
 428        mutex_lock(&mapping->i_mmap_mutex);
 429        read_lock(&tasklist_lock);
 430        for_each_process(tsk) {
 431                pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
 432
 433                if (!task_early_kill(tsk))
 434                        continue;
 435
 436                vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff,
 437                                      pgoff) {
 438                        /*
 439                         * Send early kill signal to tasks where a vma covers
 440                         * the page but the corrupted page is not necessarily
 441                         * mapped it in its pte.
 442                         * Assume applications who requested early kill want
 443                         * to be informed of all such data corruptions.
 444                         */
 445                        if (vma->vm_mm == tsk->mm)
 446                                add_to_kill(tsk, page, vma, to_kill, tkc);
 447                }
 448        }
 449        read_unlock(&tasklist_lock);
 450        mutex_unlock(&mapping->i_mmap_mutex);
 451}
 452
 453/*
 454 * Collect the processes who have the corrupted page mapped to kill.
 455 * This is done in two steps for locking reasons.
 456 * First preallocate one tokill structure outside the spin locks,
 457 * so that we can kill at least one process reasonably reliable.
 458 */
 459static void collect_procs(struct page *page, struct list_head *tokill)
 460{
 461        struct to_kill *tk;
 462
 463        if (!page->mapping)
 464                return;
 465
 466        tk = kmalloc(sizeof(struct to_kill), GFP_NOIO);
 467        if (!tk)
 468                return;
 469        if (PageAnon(page))
 470                collect_procs_anon(page, tokill, &tk);
 471        else
 472                collect_procs_file(page, tokill, &tk);
 473        kfree(tk);
 474}
 475
 476/*
 477 * Error handlers for various types of pages.
 478 */
 479
 480enum outcome {
 481        IGNORED,        /* Error: cannot be handled */
 482        FAILED,         /* Error: handling failed */
 483        DELAYED,        /* Will be handled later */
 484        RECOVERED,      /* Successfully recovered */
 485};
 486
 487static const char *action_name[] = {
 488        [IGNORED] = "Ignored",
 489        [FAILED] = "Failed",
 490        [DELAYED] = "Delayed",
 491        [RECOVERED] = "Recovered",
 492};
 493
 494/*
 495 * XXX: It is possible that a page is isolated from LRU cache,
 496 * and then kept in swap cache or failed to remove from page cache.
 497 * The page count will stop it from being freed by unpoison.
 498 * Stress tests should be aware of this memory leak problem.
 499 */
 500static int delete_from_lru_cache(struct page *p)
 501{
 502        if (!isolate_lru_page(p)) {
 503                /*
 504                 * Clear sensible page flags, so that the buddy system won't
 505                 * complain when the page is unpoison-and-freed.
 506                 */
 507                ClearPageActive(p);
 508                ClearPageUnevictable(p);
 509                /*
 510                 * drop the page count elevated by isolate_lru_page()
 511                 */
 512                page_cache_release(p);
 513                return 0;
 514        }
 515        return -EIO;
 516}
 517
 518/*
 519 * Error hit kernel page.
 520 * Do nothing, try to be lucky and not touch this instead. For a few cases we
 521 * could be more sophisticated.
 522 */
 523static int me_kernel(struct page *p, unsigned long pfn)
 524{
 525        return IGNORED;
 526}
 527
 528/*
 529 * Page in unknown state. Do nothing.
 530 */
 531static int me_unknown(struct page *p, unsigned long pfn)
 532{
 533        printk(KERN_ERR "MCE %#lx: Unknown page state\n", pfn);
 534        return FAILED;
 535}
 536
 537/*
 538 * Clean (or cleaned) page cache page.
 539 */
 540static int me_pagecache_clean(struct page *p, unsigned long pfn)
 541{
 542        int err;
 543        int ret = FAILED;
 544        struct address_space *mapping;
 545
 546        delete_from_lru_cache(p);
 547
 548        /*
 549         * For anonymous pages we're done the only reference left
 550         * should be the one m_f() holds.
 551         */
 552        if (PageAnon(p))
 553                return RECOVERED;
 554
 555        /*
 556         * Now truncate the page in the page cache. This is really
 557         * more like a "temporary hole punch"
 558         * Don't do this for block devices when someone else
 559         * has a reference, because it could be file system metadata
 560         * and that's not safe to truncate.
 561         */
 562        mapping = page_mapping(p);
 563        if (!mapping) {
 564                /*
 565                 * Page has been teared down in the meanwhile
 566                 */
 567                return FAILED;
 568        }
 569
 570        /*
 571         * Truncation is a bit tricky. Enable it per file system for now.
 572         *
 573         * Open: to take i_mutex or not for this? Right now we don't.
 574         */
 575        if (mapping->a_ops->error_remove_page) {
 576                err = mapping->a_ops->error_remove_page(mapping, p);
 577                if (err != 0) {
 578                        printk(KERN_INFO "MCE %#lx: Failed to punch page: %d\n",
 579                                        pfn, err);
 580                } else if (page_has_private(p) &&
 581                                !try_to_release_page(p, GFP_NOIO)) {
 582                        pr_info("MCE %#lx: failed to release buffers\n", pfn);
 583                } else {
 584                        ret = RECOVERED;
 585                }
 586        } else {
 587                /*
 588                 * If the file system doesn't support it just invalidate
 589                 * This fails on dirty or anything with private pages
 590                 */
 591                if (invalidate_inode_page(p))
 592                        ret = RECOVERED;
 593                else
 594                        printk(KERN_INFO "MCE %#lx: Failed to invalidate\n",
 595                                pfn);
 596        }
 597        return ret;
 598}
 599
 600/*
 601 * Dirty cache page page
 602 * Issues: when the error hit a hole page the error is not properly
 603 * propagated.
 604 */
 605static int me_pagecache_dirty(struct page *p, unsigned long pfn)
 606{
 607        struct address_space *mapping = page_mapping(p);
 608
 609        SetPageError(p);
 610        /* TBD: print more information about the file. */
 611        if (mapping) {
 612                /*
 613                 * IO error will be reported by write(), fsync(), etc.
 614                 * who check the mapping.
 615                 * This way the application knows that something went
 616                 * wrong with its dirty file data.
 617                 *
 618                 * There's one open issue:
 619                 *
 620                 * The EIO will be only reported on the next IO
 621                 * operation and then cleared through the IO map.
 622                 * Normally Linux has two mechanisms to pass IO error
 623                 * first through the AS_EIO flag in the address space
 624                 * and then through the PageError flag in the page.
 625                 * Since we drop pages on memory failure handling the
 626                 * only mechanism open to use is through AS_AIO.
 627                 *
 628                 * This has the disadvantage that it gets cleared on
 629                 * the first operation that returns an error, while
 630                 * the PageError bit is more sticky and only cleared
 631                 * when the page is reread or dropped.  If an
 632                 * application assumes it will always get error on
 633                 * fsync, but does other operations on the fd before
 634                 * and the page is dropped between then the error
 635                 * will not be properly reported.
 636                 *
 637                 * This can already happen even without hwpoisoned
 638                 * pages: first on metadata IO errors (which only
 639                 * report through AS_EIO) or when the page is dropped
 640                 * at the wrong time.
 641                 *
 642                 * So right now we assume that the application DTRT on
 643                 * the first EIO, but we're not worse than other parts
 644                 * of the kernel.
 645                 */
 646                mapping_set_error(mapping, EIO);
 647        }
 648
 649        return me_pagecache_clean(p, pfn);
 650}
 651
 652/*
 653 * Clean and dirty swap cache.
 654 *
 655 * Dirty swap cache page is tricky to handle. The page could live both in page
 656 * cache and swap cache(ie. page is freshly swapped in). So it could be
 657 * referenced concurrently by 2 types of PTEs:
 658 * normal PTEs and swap PTEs. We try to handle them consistently by calling
 659 * try_to_unmap(TTU_IGNORE_HWPOISON) to convert the normal PTEs to swap PTEs,
 660 * and then
 661 *      - clear dirty bit to prevent IO
 662 *      - remove from LRU
 663 *      - but keep in the swap cache, so that when we return to it on
 664 *        a later page fault, we know the application is accessing
 665 *        corrupted data and shall be killed (we installed simple
 666 *        interception code in do_swap_page to catch it).
 667 *
 668 * Clean swap cache pages can be directly isolated. A later page fault will
 669 * bring in the known good data from disk.
 670 */
 671static int me_swapcache_dirty(struct page *p, unsigned long pfn)
 672{
 673        ClearPageDirty(p);
 674        /* Trigger EIO in shmem: */
 675        ClearPageUptodate(p);
 676
 677        if (!delete_from_lru_cache(p))
 678                return DELAYED;
 679        else
 680                return FAILED;
 681}
 682
 683static int me_swapcache_clean(struct page *p, unsigned long pfn)
 684{
 685        delete_from_swap_cache(p);
 686
 687        if (!delete_from_lru_cache(p))
 688                return RECOVERED;
 689        else
 690                return FAILED;
 691}
 692
 693/*
 694 * Huge pages. Needs work.
 695 * Issues:
 696 * - Error on hugepage is contained in hugepage unit (not in raw page unit.)
 697 *   To narrow down kill region to one page, we need to break up pmd.
 698 */
 699static int me_huge_page(struct page *p, unsigned long pfn)
 700{
 701        int res = 0;
 702        struct page *hpage = compound_head(p);
 703        /*
 704         * We can safely recover from error on free or reserved (i.e.
 705         * not in-use) hugepage by dequeuing it from freelist.
 706         * To check whether a hugepage is in-use or not, we can't use
 707         * page->lru because it can be used in other hugepage operations,
 708         * such as __unmap_hugepage_range() and gather_surplus_pages().
 709         * So instead we use page_mapping() and PageAnon().
 710         * We assume that this function is called with page lock held,
 711         * so there is no race between isolation and mapping/unmapping.
 712         */
 713        if (!(page_mapping(hpage) || PageAnon(hpage))) {
 714                res = dequeue_hwpoisoned_huge_page(hpage);
 715                if (!res)
 716                        return RECOVERED;
 717        }
 718        return DELAYED;
 719}
 720
 721/*
 722 * Various page states we can handle.
 723 *
 724 * A page state is defined by its current page->flags bits.
 725 * The table matches them in order and calls the right handler.
 726 *
 727 * This is quite tricky because we can access page at any time
 728 * in its live cycle, so all accesses have to be extremely careful.
 729 *
 730 * This is not complete. More states could be added.
 731 * For any missing state don't attempt recovery.
 732 */
 733
 734#define dirty           (1UL << PG_dirty)
 735#define sc              (1UL << PG_swapcache)
 736#define unevict         (1UL << PG_unevictable)
 737#define mlock           (1UL << PG_mlocked)
 738#define writeback       (1UL << PG_writeback)
 739#define lru             (1UL << PG_lru)
 740#define swapbacked      (1UL << PG_swapbacked)
 741#define head            (1UL << PG_head)
 742#define tail            (1UL << PG_tail)
 743#define compound        (1UL << PG_compound)
 744#define slab            (1UL << PG_slab)
 745#define reserved        (1UL << PG_reserved)
 746
 747static struct page_state {
 748        unsigned long mask;
 749        unsigned long res;
 750        char *msg;
 751        int (*action)(struct page *p, unsigned long pfn);
 752} error_states[] = {
 753        { reserved,     reserved,       "reserved kernel",      me_kernel },
 754        /*
 755         * free pages are specially detected outside this table:
 756         * PG_buddy pages only make a small fraction of all free pages.
 757         */
 758
 759        /*
 760         * Could in theory check if slab page is free or if we can drop
 761         * currently unused objects without touching them. But just
 762         * treat it as standard kernel for now.
 763         */
 764        { slab,         slab,           "kernel slab",  me_kernel },
 765
 766#ifdef CONFIG_PAGEFLAGS_EXTENDED
 767        { head,         head,           "huge",         me_huge_page },
 768        { tail,         tail,           "huge",         me_huge_page },
 769#else
 770        { compound,     compound,       "huge",         me_huge_page },
 771#endif
 772
 773        { sc|dirty,     sc|dirty,       "swapcache",    me_swapcache_dirty },
 774        { sc|dirty,     sc,             "swapcache",    me_swapcache_clean },
 775
 776        { unevict|dirty, unevict|dirty, "unevictable LRU", me_pagecache_dirty},
 777        { unevict,      unevict,        "unevictable LRU", me_pagecache_clean},
 778
 779        { mlock|dirty,  mlock|dirty,    "mlocked LRU",  me_pagecache_dirty },
 780        { mlock,        mlock,          "mlocked LRU",  me_pagecache_clean },
 781
 782        { lru|dirty,    lru|dirty,      "LRU",          me_pagecache_dirty },
 783        { lru|dirty,    lru,            "clean LRU",    me_pagecache_clean },
 784
 785        /*
 786         * Catchall entry: must be at end.
 787         */
 788        { 0,            0,              "unknown page state",   me_unknown },
 789};
 790
 791#undef dirty
 792#undef sc
 793#undef unevict
 794#undef mlock
 795#undef writeback
 796#undef lru
 797#undef swapbacked
 798#undef head
 799#undef tail
 800#undef compound
 801#undef slab
 802#undef reserved
 803
 804static void action_result(unsigned long pfn, char *msg, int result)
 805{
 806        struct page *page = pfn_to_page(pfn);
 807
 808        printk(KERN_ERR "MCE %#lx: %s%s page recovery: %s\n",
 809                pfn,
 810                PageDirty(page) ? "dirty " : "",
 811                msg, action_name[result]);
 812}
 813
 814static int page_action(struct page_state *ps, struct page *p,
 815                        unsigned long pfn)
 816{
 817        int result;
 818        int count;
 819
 820        result = ps->action(p, pfn);
 821        action_result(pfn, ps->msg, result);
 822
 823        count = page_count(p) - 1;
 824        if (ps->action == me_swapcache_dirty && result == DELAYED)
 825                count--;
 826        if (count != 0) {
 827                printk(KERN_ERR
 828                       "MCE %#lx: %s page still referenced by %d users\n",
 829                       pfn, ps->msg, count);
 830                result = FAILED;
 831        }
 832
 833        /* Could do more checks here if page looks ok */
 834        /*
 835         * Could adjust zone counters here to correct for the missing page.
 836         */
 837
 838        return (result == RECOVERED || result == DELAYED) ? 0 : -EBUSY;
 839}
 840
 841/*
 842 * Do all that is necessary to remove user space mappings. Unmap
 843 * the pages and send SIGBUS to the processes if the data was dirty.
 844 */
 845static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
 846                                  int trapno)
 847{
 848        enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
 849        struct address_space *mapping;
 850        LIST_HEAD(tokill);
 851        int ret;
 852        int kill = 1;
 853        struct page *hpage = compound_head(p);
 854        struct page *ppage;
 855
 856        if (PageReserved(p) || PageSlab(p))
 857                return SWAP_SUCCESS;
 858
 859        /*
 860         * This check implies we don't kill processes if their pages
 861         * are in the swap cache early. Those are always late kills.
 862         */
 863        if (!page_mapped(hpage))
 864                return SWAP_SUCCESS;
 865
 866        if (PageKsm(p))
 867                return SWAP_FAIL;
 868
 869        if (PageSwapCache(p)) {
 870                printk(KERN_ERR
 871                       "MCE %#lx: keeping poisoned page in swap cache\n", pfn);
 872                ttu |= TTU_IGNORE_HWPOISON;
 873        }
 874
 875        /*
 876         * Propagate the dirty bit from PTEs to struct page first, because we
 877         * need this to decide if we should kill or just drop the page.
 878         * XXX: the dirty test could be racy: set_page_dirty() may not always
 879         * be called inside page lock (it's recommended but not enforced).
 880         */
 881        mapping = page_mapping(hpage);
 882        if (!PageDirty(hpage) && mapping &&
 883            mapping_cap_writeback_dirty(mapping)) {
 884                if (page_mkclean(hpage)) {
 885                        SetPageDirty(hpage);
 886                } else {
 887                        kill = 0;
 888                        ttu |= TTU_IGNORE_HWPOISON;
 889                        printk(KERN_INFO
 890        "MCE %#lx: corrupted page was clean: dropped without side effects\n",
 891                                pfn);
 892                }
 893        }
 894
 895        /*
 896         * ppage: poisoned page
 897         *   if p is regular page(4k page)
 898         *        ppage == real poisoned page;
 899         *   else p is hugetlb or THP, ppage == head page.
 900         */
 901        ppage = hpage;
 902
 903        if (PageTransHuge(hpage)) {
 904                /*
 905                 * Verify that this isn't a hugetlbfs head page, the check for
 906                 * PageAnon is just for avoid tripping a split_huge_page
 907                 * internal debug check, as split_huge_page refuses to deal with
 908                 * anything that isn't an anon page. PageAnon can't go away fro
 909                 * under us because we hold a refcount on the hpage, without a
 910                 * refcount on the hpage. split_huge_page can't be safely called
 911                 * in the first place, having a refcount on the tail isn't
 912                 * enough * to be safe.
 913                 */
 914                if (!PageHuge(hpage) && PageAnon(hpage)) {
 915                        if (unlikely(split_huge_page(hpage))) {
 916                                /*
 917                                 * FIXME: if splitting THP is failed, it is
 918                                 * better to stop the following operation rather
 919                                 * than causing panic by unmapping. System might
 920                                 * survive if the page is freed later.
 921                                 */
 922                                printk(KERN_INFO
 923                                        "MCE %#lx: failed to split THP\n", pfn);
 924
 925                                BUG_ON(!PageHWPoison(p));
 926                                return SWAP_FAIL;
 927                        }
 928                        /* THP is split, so ppage should be the real poisoned page. */
 929                        ppage = p;
 930                }
 931        }
 932
 933        /*
 934         * First collect all the processes that have the page
 935         * mapped in dirty form.  This has to be done before try_to_unmap,
 936         * because ttu takes the rmap data structures down.
 937         *
 938         * Error handling: We ignore errors here because
 939         * there's nothing that can be done.
 940         */
 941        if (kill)
 942                collect_procs(ppage, &tokill);
 943
 944        if (hpage != ppage)
 945                lock_page(ppage);
 946
 947        ret = try_to_unmap(ppage, ttu);
 948        if (ret != SWAP_SUCCESS)
 949                printk(KERN_ERR "MCE %#lx: failed to unmap page (mapcount=%d)\n",
 950                                pfn, page_mapcount(ppage));
 951
 952        if (hpage != ppage)
 953                unlock_page(ppage);
 954
 955        /*
 956         * Now that the dirty bit has been propagated to the
 957         * struct page and all unmaps done we can decide if
 958         * killing is needed or not.  Only kill when the page
 959         * was dirty, otherwise the tokill list is merely
 960         * freed.  When there was a problem unmapping earlier
 961         * use a more force-full uncatchable kill to prevent
 962         * any accesses to the poisoned memory.
 963         */
 964        kill_procs_ao(&tokill, !!PageDirty(ppage), trapno,
 965                      ret != SWAP_SUCCESS, p, pfn);
 966
 967        return ret;
 968}
 969
 970static void set_page_hwpoison_huge_page(struct page *hpage)
 971{
 972        int i;
 973        int nr_pages = 1 << compound_trans_order(hpage);
 974        for (i = 0; i < nr_pages; i++)
 975                SetPageHWPoison(hpage + i);
 976}
 977
 978static void clear_page_hwpoison_huge_page(struct page *hpage)
 979{
 980        int i;
 981        int nr_pages = 1 << compound_trans_order(hpage);
 982        for (i = 0; i < nr_pages; i++)
 983                ClearPageHWPoison(hpage + i);
 984}
 985
 986int __memory_failure(unsigned long pfn, int trapno, int flags)
 987{
 988        struct page_state *ps;
 989        struct page *p;
 990        struct page *hpage;
 991        int res;
 992        unsigned int nr_pages;
 993
 994        if (!sysctl_memory_failure_recovery)
 995                panic("Memory failure from trap %d on page %lx", trapno, pfn);
 996
 997        if (!pfn_valid(pfn)) {
 998                printk(KERN_ERR
 999                       "MCE %#lx: memory outside kernel control\n",
1000                       pfn);
1001                return -ENXIO;
1002        }
1003
1004        p = pfn_to_page(pfn);
1005        hpage = compound_head(p);
1006        if (TestSetPageHWPoison(p)) {
1007                printk(KERN_ERR "MCE %#lx: already hardware poisoned\n", pfn);
1008                return 0;
1009        }
1010
1011        nr_pages = 1 << compound_trans_order(hpage);
1012        atomic_long_add(nr_pages, &mce_bad_pages);
1013
1014        /*
1015         * We need/can do nothing about count=0 pages.
1016         * 1) it's a free page, and therefore in safe hand:
1017         *    prep_new_page() will be the gate keeper.
1018         * 2) it's a free hugepage, which is also safe:
1019         *    an affected hugepage will be dequeued from hugepage freelist,
1020         *    so there's no concern about reusing it ever after.
1021         * 3) it's part of a non-compound high order page.
1022         *    Implies some kernel user: cannot stop them from
1023         *    R/W the page; let's pray that the page has been
1024         *    used and will be freed some time later.
1025         * In fact it's dangerous to directly bump up page count from 0,
1026         * that may make page_freeze_refs()/page_unfreeze_refs() mismatch.
1027         */
1028        if (!(flags & MF_COUNT_INCREASED) &&
1029                !get_page_unless_zero(hpage)) {
1030                if (is_free_buddy_page(p)) {
1031                        action_result(pfn, "free buddy", DELAYED);
1032                        return 0;
1033                } else if (PageHuge(hpage)) {
1034                        /*
1035                         * Check "just unpoisoned", "filter hit", and
1036                         * "race with other subpage."
1037                         */
1038                        lock_page(hpage);
1039                        if (!PageHWPoison(hpage)
1040                            || (hwpoison_filter(p) && TestClearPageHWPoison(p))
1041                            || (p != hpage && TestSetPageHWPoison(hpage))) {
1042                                atomic_long_sub(nr_pages, &mce_bad_pages);
1043                                return 0;
1044                        }
1045                        set_page_hwpoison_huge_page(hpage);
1046                        res = dequeue_hwpoisoned_huge_page(hpage);
1047                        action_result(pfn, "free huge",
1048                                      res ? IGNORED : DELAYED);
1049                        unlock_page(hpage);
1050                        return res;
1051                } else {
1052                        action_result(pfn, "high order kernel", IGNORED);
1053                        return -EBUSY;
1054                }
1055        }
1056
1057        /*
1058         * We ignore non-LRU pages for good reasons.
1059         * - PG_locked is only well defined for LRU pages and a few others
1060         * - to avoid races with __set_page_locked()
1061         * - to avoid races with __SetPageSlab*() (and more non-atomic ops)
1062         * The check (unnecessarily) ignores LRU pages being isolated and
1063         * walked by the page reclaim code, however that's not a big loss.
1064         */
1065        if (!PageHuge(p) && !PageTransCompound(p)) {
1066                if (!PageLRU(p))
1067                        shake_page(p, 0);
1068                if (!PageLRU(p)) {
1069                        /*
1070                         * shake_page could have turned it free.
1071                         */
1072                        if (is_free_buddy_page(p)) {
1073                                action_result(pfn, "free buddy, 2nd try",
1074                                                DELAYED);
1075                                return 0;
1076                        }
1077                        action_result(pfn, "non LRU", IGNORED);
1078                        put_page(p);
1079                        return -EBUSY;
1080                }
1081        }
1082
1083        /*
1084         * Lock the page and wait for writeback to finish.
1085         * It's very difficult to mess with pages currently under IO
1086         * and in many cases impossible, so we just avoid it here.
1087         */
1088        lock_page(hpage);
1089
1090        /*
1091         * unpoison always clear PG_hwpoison inside page lock
1092         */
1093        if (!PageHWPoison(p)) {
1094                printk(KERN_ERR "MCE %#lx: just unpoisoned\n", pfn);
1095                res = 0;
1096                goto out;
1097        }
1098        if (hwpoison_filter(p)) {
1099                if (TestClearPageHWPoison(p))
1100                        atomic_long_sub(nr_pages, &mce_bad_pages);
1101                unlock_page(hpage);
1102                put_page(hpage);
1103                return 0;
1104        }
1105
1106        /*
1107         * For error on the tail page, we should set PG_hwpoison
1108         * on the head page to show that the hugepage is hwpoisoned
1109         */
1110        if (PageHuge(p) && PageTail(p) && TestSetPageHWPoison(hpage)) {
1111                action_result(pfn, "hugepage already hardware poisoned",
1112                                IGNORED);
1113                unlock_page(hpage);
1114                put_page(hpage);
1115                return 0;
1116        }
1117        /*
1118         * Set PG_hwpoison on all pages in an error hugepage,
1119         * because containment is done in hugepage unit for now.
1120         * Since we have done TestSetPageHWPoison() for the head page with
1121         * page lock held, we can safely set PG_hwpoison bits on tail pages.
1122         */
1123        if (PageHuge(p))
1124                set_page_hwpoison_huge_page(hpage);
1125
1126        wait_on_page_writeback(p);
1127
1128        /*
1129         * Now take care of user space mappings.
1130         * Abort on fail: __delete_from_page_cache() assumes unmapped page.
1131         */
1132        if (hwpoison_user_mappings(p, pfn, trapno) != SWAP_SUCCESS) {
1133                printk(KERN_ERR "MCE %#lx: cannot unmap page, give up\n", pfn);
1134                res = -EBUSY;
1135                goto out;
1136        }
1137
1138        /*
1139         * Torn down by someone else?
1140         */
1141        if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) {
1142                action_result(pfn, "already truncated LRU", IGNORED);
1143                res = -EBUSY;
1144                goto out;
1145        }
1146
1147        res = -EBUSY;
1148        for (ps = error_states;; ps++) {
1149                if ((p->flags & ps->mask) == ps->res) {
1150                        res = page_action(ps, p, pfn);
1151                        break;
1152                }
1153        }
1154out:
1155        unlock_page(hpage);
1156        return res;
1157}
1158EXPORT_SYMBOL_GPL(__memory_failure);
1159
1160/**
1161 * memory_failure - Handle memory failure of a page.
1162 * @pfn: Page Number of the corrupted page
1163 * @trapno: Trap number reported in the signal to user space.
1164 *
1165 * This function is called by the low level machine check code
1166 * of an architecture when it detects hardware memory corruption
1167 * of a page. It tries its best to recover, which includes
1168 * dropping pages, killing processes etc.
1169 *
1170 * The function is primarily of use for corruptions that
1171 * happen outside the current execution context (e.g. when
1172 * detected by a background scrubber)
1173 *
1174 * Must run in process context (e.g. a work queue) with interrupts
1175 * enabled and no spinlocks hold.
1176 */
1177void memory_failure(unsigned long pfn, int trapno)
1178{
1179        __memory_failure(pfn, trapno, 0);
1180}
1181
1182#define MEMORY_FAILURE_FIFO_ORDER       4
1183#define MEMORY_FAILURE_FIFO_SIZE        (1 << MEMORY_FAILURE_FIFO_ORDER)
1184
1185struct memory_failure_entry {
1186        unsigned long pfn;
1187        int trapno;
1188        int flags;
1189};
1190
1191struct memory_failure_cpu {
1192        DECLARE_KFIFO(fifo, struct memory_failure_entry,
1193                      MEMORY_FAILURE_FIFO_SIZE);
1194        spinlock_t lock;
1195        struct work_struct work;
1196};
1197
1198static DEFINE_PER_CPU(struct memory_failure_cpu, memory_failure_cpu);
1199
1200/**
1201 * memory_failure_queue - Schedule handling memory failure of a page.
1202 * @pfn: Page Number of the corrupted page
1203 * @trapno: Trap number reported in the signal to user space.
1204 * @flags: Flags for memory failure handling
1205 *
1206 * This function is called by the low level hardware error handler
1207 * when it detects hardware memory corruption of a page. It schedules
1208 * the recovering of error page, including dropping pages, killing
1209 * processes etc.
1210 *
1211 * The function is primarily of use for corruptions that
1212 * happen outside the current execution context (e.g. when
1213 * detected by a background scrubber)
1214 *
1215 * Can run in IRQ context.
1216 */
1217void memory_failure_queue(unsigned long pfn, int trapno, int flags)
1218{
1219        struct memory_failure_cpu *mf_cpu;
1220        unsigned long proc_flags;
1221        struct memory_failure_entry entry = {
1222                .pfn =          pfn,
1223                .trapno =       trapno,
1224                .flags =        flags,
1225        };
1226
1227        mf_cpu = &get_cpu_var(memory_failure_cpu);
1228        spin_lock_irqsave(&mf_cpu->lock, proc_flags);
1229        if (kfifo_put(&mf_cpu->fifo, &entry))
1230                schedule_work_on(smp_processor_id(), &mf_cpu->work);
1231        else
1232                pr_err("Memory failure: buffer overflow when queuing memory failure at 0x%#lx\n",
1233                       pfn);
1234        spin_unlock_irqrestore(&mf_cpu->lock, proc_flags);
1235        put_cpu_var(memory_failure_cpu);
1236}
1237EXPORT_SYMBOL_GPL(memory_failure_queue);
1238
1239static void memory_failure_work_func(struct work_struct *work)
1240{
1241        struct memory_failure_cpu *mf_cpu;
1242        struct memory_failure_entry entry = { 0, };
1243        unsigned long proc_flags;
1244        int gotten;
1245
1246        mf_cpu = &__get_cpu_var(memory_failure_cpu);
1247        for (;;) {
1248                spin_lock_irqsave(&mf_cpu->lock, proc_flags);
1249                gotten = kfifo_get(&mf_cpu->fifo, &entry);
1250                spin_unlock_irqrestore(&mf_cpu->lock, proc_flags);
1251                if (!gotten)
1252                        break;
1253                __memory_failure(entry.pfn, entry.trapno, entry.flags);
1254        }
1255}
1256
1257static int __init memory_failure_init(void)
1258{
1259        struct memory_failure_cpu *mf_cpu;
1260        int cpu;
1261
1262        for_each_possible_cpu(cpu) {
1263                mf_cpu = &per_cpu(memory_failure_cpu, cpu);
1264                spin_lock_init(&mf_cpu->lock);
1265                INIT_KFIFO(mf_cpu->fifo);
1266                INIT_WORK(&mf_cpu->work, memory_failure_work_func);
1267        }
1268
1269        return 0;
1270}
1271core_initcall(memory_failure_init);
1272
1273/**
1274 * unpoison_memory - Unpoison a previously poisoned page
1275 * @pfn: Page number of the to be unpoisoned page
1276 *
1277 * Software-unpoison a page that has been poisoned by
1278 * memory_failure() earlier.
1279 *
1280 * This is only done on the software-level, so it only works
1281 * for linux injected failures, not real hardware failures
1282 *
1283 * Returns 0 for success, otherwise -errno.
1284 */
1285int unpoison_memory(unsigned long pfn)
1286{
1287        struct page *page;
1288        struct page *p;
1289        int freeit = 0;
1290        unsigned int nr_pages;
1291
1292        if (!pfn_valid(pfn))
1293                return -ENXIO;
1294
1295        p = pfn_to_page(pfn);
1296        page = compound_head(p);
1297
1298        if (!PageHWPoison(p)) {
1299                pr_info("MCE: Page was already unpoisoned %#lx\n", pfn);
1300                return 0;
1301        }
1302
1303        nr_pages = 1 << compound_trans_order(page);
1304
1305        if (!get_page_unless_zero(page)) {
1306                /*
1307                 * Since HWPoisoned hugepage should have non-zero refcount,
1308                 * race between memory failure and unpoison seems to happen.
1309                 * In such case unpoison fails and memory failure runs
1310                 * to the end.
1311                 */
1312                if (PageHuge(page)) {
1313                        pr_debug("MCE: Memory failure is now running on free hugepage %#lx\n", pfn);
1314                        return 0;
1315                }
1316                if (TestClearPageHWPoison(p))
1317                        atomic_long_sub(nr_pages, &mce_bad_pages);
1318                pr_info("MCE: Software-unpoisoned free page %#lx\n", pfn);
1319                return 0;
1320        }
1321
1322        lock_page(page);
1323        /*
1324         * This test is racy because PG_hwpoison is set outside of page lock.
1325         * That's acceptable because that won't trigger kernel panic. Instead,
1326         * the PG_hwpoison page will be caught and isolated on the entrance to
1327         * the free buddy page pool.
1328         */
1329        if (TestClearPageHWPoison(page)) {
1330                pr_info("MCE: Software-unpoisoned page %#lx\n", pfn);
1331                atomic_long_sub(nr_pages, &mce_bad_pages);
1332                freeit = 1;
1333                if (PageHuge(page))
1334                        clear_page_hwpoison_huge_page(page);
1335        }
1336        unlock_page(page);
1337
1338        put_page(page);
1339        if (freeit)
1340                put_page(page);
1341
1342        return 0;
1343}
1344EXPORT_SYMBOL(unpoison_memory);
1345
1346static struct page *new_page(struct page *p, unsigned long private, int **x)
1347{
1348        int nid = page_to_nid(p);
1349        if (PageHuge(p))
1350                return alloc_huge_page_node(page_hstate(compound_head(p)),
1351                                                   nid);
1352        else
1353                return alloc_pages_exact_node(nid, GFP_HIGHUSER_MOVABLE, 0);
1354}
1355
1356/*
1357 * Safely get reference count of an arbitrary page.
1358 * Returns 0 for a free page, -EIO for a zero refcount page
1359 * that is not free, and 1 for any other page type.
1360 * For 1 the page is returned with increased page count, otherwise not.
1361 */
1362static int get_any_page(struct page *p, unsigned long pfn, int flags)
1363{
1364        int ret;
1365
1366        if (flags & MF_COUNT_INCREASED)
1367                return 1;
1368
1369        /*
1370         * The lock_memory_hotplug prevents a race with memory hotplug.
1371         * This is a big hammer, a better would be nicer.
1372         */
1373        lock_memory_hotplug();
1374
1375        /*
1376         * Isolate the page, so that it doesn't get reallocated if it
1377         * was free.
1378         */
1379        set_migratetype_isolate(p);
1380        /*
1381         * When the target page is a free hugepage, just remove it
1382         * from free hugepage list.
1383         */
1384        if (!get_page_unless_zero(compound_head(p))) {
1385                if (PageHuge(p)) {
1386                        pr_info("get_any_page: %#lx free huge page\n", pfn);
1387                        ret = dequeue_hwpoisoned_huge_page(compound_head(p));
1388                } else if (is_free_buddy_page(p)) {
1389                        pr_info("get_any_page: %#lx free buddy page\n", pfn);
1390                        /* Set hwpoison bit while page is still isolated */
1391                        SetPageHWPoison(p);
1392                        ret = 0;
1393                } else {
1394                        pr_info("get_any_page: %#lx: unknown zero refcount page type %lx\n",
1395                                pfn, p->flags);
1396                        ret = -EIO;
1397                }
1398        } else {
1399                /* Not a free page */
1400                ret = 1;
1401        }
1402        unset_migratetype_isolate(p);
1403        unlock_memory_hotplug();
1404        return ret;
1405}
1406
1407static int soft_offline_huge_page(struct page *page, int flags)
1408{
1409        int ret;
1410        unsigned long pfn = page_to_pfn(page);
1411        struct page *hpage = compound_head(page);
1412        LIST_HEAD(pagelist);
1413
1414        ret = get_any_page(page, pfn, flags);
1415        if (ret < 0)
1416                return ret;
1417        if (ret == 0)
1418                goto done;
1419
1420        if (PageHWPoison(hpage)) {
1421                put_page(hpage);
1422                pr_debug("soft offline: %#lx hugepage already poisoned\n", pfn);
1423                return -EBUSY;
1424        }
1425
1426        /* Keep page count to indicate a given hugepage is isolated. */
1427
1428        list_add(&hpage->lru, &pagelist);
1429        ret = migrate_huge_pages(&pagelist, new_page, MPOL_MF_MOVE_ALL, 0,
1430                                true);
1431        if (ret) {
1432                struct page *page1, *page2;
1433                list_for_each_entry_safe(page1, page2, &pagelist, lru)
1434                        put_page(page1);
1435
1436                pr_debug("soft offline: %#lx: migration failed %d, type %lx\n",
1437                         pfn, ret, page->flags);
1438                if (ret > 0)
1439                        ret = -EIO;
1440                return ret;
1441        }
1442done:
1443        if (!PageHWPoison(hpage))
1444                atomic_long_add(1 << compound_trans_order(hpage), &mce_bad_pages);
1445        set_page_hwpoison_huge_page(hpage);
1446        dequeue_hwpoisoned_huge_page(hpage);
1447        /* keep elevated page count for bad page */
1448        return ret;
1449}
1450
1451/**
1452 * soft_offline_page - Soft offline a page.
1453 * @page: page to offline
1454 * @flags: flags. Same as memory_failure().
1455 *
1456 * Returns 0 on success, otherwise negated errno.
1457 *
1458 * Soft offline a page, by migration or invalidation,
1459 * without killing anything. This is for the case when
1460 * a page is not corrupted yet (so it's still valid to access),
1461 * but has had a number of corrected errors and is better taken
1462 * out.
1463 *
1464 * The actual policy on when to do that is maintained by
1465 * user space.
1466 *
1467 * This should never impact any application or cause data loss,
1468 * however it might take some time.
1469 *
1470 * This is not a 100% solution for all memory, but tries to be
1471 * ``good enough'' for the majority of memory.
1472 */
1473int soft_offline_page(struct page *page, int flags)
1474{
1475        int ret;
1476        unsigned long pfn = page_to_pfn(page);
1477
1478        if (PageHuge(page))
1479                return soft_offline_huge_page(page, flags);
1480
1481        ret = get_any_page(page, pfn, flags);
1482        if (ret < 0)
1483                return ret;
1484        if (ret == 0)
1485                goto done;
1486
1487        /*
1488         * Page cache page we can handle?
1489         */
1490        if (!PageLRU(page)) {
1491                /*
1492                 * Try to free it.
1493                 */
1494                put_page(page);
1495                shake_page(page, 1);
1496
1497                /*
1498                 * Did it turn free?
1499                 */
1500                ret = get_any_page(page, pfn, 0);
1501                if (ret < 0)
1502                        return ret;
1503                if (ret == 0)
1504                        goto done;
1505        }
1506        if (!PageLRU(page)) {
1507                pr_info("soft_offline: %#lx: unknown non LRU page type %lx\n",
1508                                pfn, page->flags);
1509                return -EIO;
1510        }
1511
1512        lock_page(page);
1513        wait_on_page_writeback(page);
1514
1515        /*
1516         * Synchronized using the page lock with memory_failure()
1517         */
1518        if (PageHWPoison(page)) {
1519                unlock_page(page);
1520                put_page(page);
1521                pr_info("soft offline: %#lx page already poisoned\n", pfn);
1522                return -EBUSY;
1523        }
1524
1525        /*
1526         * Try to invalidate first. This should work for
1527         * non dirty unmapped page cache pages.
1528         */
1529        ret = invalidate_inode_page(page);
1530        unlock_page(page);
1531        /*
1532         * RED-PEN would be better to keep it isolated here, but we
1533         * would need to fix isolation locking first.
1534         */
1535        if (ret == 1) {
1536                put_page(page);
1537                ret = 0;
1538                pr_info("soft_offline: %#lx: invalidated\n", pfn);
1539                goto done;
1540        }
1541
1542        /*
1543         * Simple invalidation didn't work.
1544         * Try to migrate to a new page instead. migrate.c
1545         * handles a large number of cases for us.
1546         */
1547        ret = isolate_lru_page(page);
1548        /*
1549         * Drop page reference which is came from get_any_page()
1550         * successful isolate_lru_page() already took another one.
1551         */
1552        put_page(page);
1553        if (!ret) {
1554                LIST_HEAD(pagelist);
1555                inc_zone_page_state(page, NR_ISOLATED_ANON +
1556                                            page_is_file_cache(page));
1557                list_add(&page->lru, &pagelist);
1558                ret = migrate_pages(&pagelist, new_page, MPOL_MF_MOVE_ALL,
1559                                                                0, true);
1560                if (ret) {
1561                        putback_lru_pages(&pagelist);
1562                        pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
1563                                pfn, ret, page->flags);
1564                        if (ret > 0)
1565                                ret = -EIO;
1566                }
1567        } else {
1568                pr_info("soft offline: %#lx: isolation failed: %d, page count %d, type %lx\n",
1569                                pfn, ret, page_count(page), page->flags);
1570        }
1571        if (ret)
1572                return ret;
1573
1574done:
1575        atomic_long_add(1, &mce_bad_pages);
1576        SetPageHWPoison(page);
1577        /* keep elevated page count for bad page */
1578        return ret;
1579}
1580
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