1 files changed, 832 insertions, 0 deletions

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
new file mode 100644
index 000000000000..729d4b15b645
--- /dev/null
+++ b/mm/memory-failure.c
@@ -0,0 +1,832 @@
+/*
+ * Copyright (C) 2008, 2009 Intel Corporation
+ * Authors: Andi Kleen, Fengguang Wu
+ *
+ * This software may be redistributed and/or modified under the terms of
+ * the GNU General Public License ("GPL") version 2 only as published by the
+ * Free Software Foundation.
+ *
+ * High level machine check handler. Handles pages reported by the
+ * hardware as being corrupted usually due to a 2bit ECC memory or cache
+ * failure.
+ *
+ * Handles page cache pages in various states.  The tricky part
+ * here is that we can access any page asynchronous to other VM
+ * users, because memory failures could happen anytime and anywhere,
+ * possibly violating some of their assumptions. This is why this code
+ * has to be extremely careful. Generally it tries to use normal locking
+ * rules, as in get the standard locks, even if that means the
+ * error handling takes potentially a long time.
+ *
+ * The operation to map back from RMAP chains to processes has to walk
+ * the complete process list and has non linear complexity with the number
+ * mappings. In short it can be quite slow. But since memory corruptions
+ * are rare we hope to get away with this.
+ */
+
+/*
+ * Notebook:
+ * - hugetlb needs more code
+ * - kcore/oldmem/vmcore/mem/kmem check for hwpoison pages
+ * - pass bad pages to kdump next kernel
+ */
+#define DEBUG 1         /* remove me in 2.6.34 */
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/page-flags.h>
+#include <linux/sched.h>
+#include <linux/rmap.h>
+#include <linux/pagemap.h>
+#include <linux/swap.h>
+#include <linux/backing-dev.h>
+#include "internal.h"
+
+int sysctl_memory_failure_early_kill __read_mostly = 0;
+
+int sysctl_memory_failure_recovery __read_mostly = 1;
+
+atomic_long_t mce_bad_pages __read_mostly = ATOMIC_LONG_INIT(0);
+
+/*
+ * Send all the processes who have the page mapped an ``action optional''
+ * signal.
+ */
+static int kill_proc_ao(struct task_struct *t, unsigned long addr, int trapno,
+                        unsigned long pfn)
+{
+        struct siginfo si;
+        int ret;
+
+        printk(KERN_ERR
+                "MCE %#lx: Killing %s:%d early due to hardware memory corruption\n",
+                pfn, t->comm, t->pid);
+        si.si_signo = SIGBUS;
+        si.si_errno = 0;
+        si.si_code = BUS_MCEERR_AO;
+        si.si_addr = (void *)addr;
+#ifdef __ARCH_SI_TRAPNO
+        si.si_trapno = trapno;
+#endif
+        si.si_addr_lsb = PAGE_SHIFT;
+        /*
+         * Don't use force here, it's convenient if the signal
+         * can be temporarily blocked.
+         * This could cause a loop when the user sets SIGBUS
+         * to SIG_IGN, but hopefully noone will do that?
+         */
+        ret = send_sig_info(SIGBUS, &si, t);  /* synchronous? */
+        if (ret < 0)
+                printk(KERN_INFO "MCE: Error sending signal to %s:%d: %d\n",
+                       t->comm, t->pid, ret);
+        return ret;
+}
+
+/*
+ * Kill all processes that have a poisoned page mapped and then isolate
+ * the page.
+ *
+ * General strategy:
+ * Find all processes having the page mapped and kill them.
+ * But we keep a page reference around so that the page is not
+ * actually freed yet.
+ * Then stash the page away
+ *
+ * There's no convenient way to get back to mapped processes
+ * from the VMAs. So do a brute-force search over all
+ * running processes.
+ *
+ * Remember that machine checks are not common (or rather
+ * if they are common you have other problems), so this shouldn't
+ * be a performance issue.
+ *
+ * Also there are some races possible while we get from the
+ * error detection to actually handle it.
+ */
+
+struct to_kill {
+        struct list_head nd;
+        struct task_struct *tsk;
+        unsigned long addr;
+        unsigned addr_valid:1;
+};
+
+/*
+ * Failure handling: if we can't find or can't kill a process there's
+ * not much we can do.  We just print a message and ignore otherwise.
+ */
+
+/*
+ * Schedule a process for later kill.
+ * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
+ * TBD would GFP_NOIO be enough?
+ */
+static void add_to_kill(struct task_struct *tsk, struct page *p,
+                       struct vm_area_struct *vma,
+                       struct list_head *to_kill,
+                       struct to_kill **tkc)
+{
+        struct to_kill *tk;
+
+        if (*tkc) {
+                tk = *tkc;
+                *tkc = NULL;
+        } else {
+                tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
+                if (!tk) {
+                        printk(KERN_ERR
+                "MCE: Out of memory while machine check handling\n");
+                        return;
+                }
+        }
+        tk->addr = page_address_in_vma(p, vma);
+        tk->addr_valid = 1;
+
+        /*
+         * In theory we don't have to kill when the page was
+         * munmaped. But it could be also a mremap. Since that's
+         * likely very rare kill anyways just out of paranoia, but use
+         * a SIGKILL because the error is not contained anymore.
+         */
+        if (tk->addr == -EFAULT) {
+                pr_debug("MCE: Unable to find user space address %lx in %s\n",
+                        page_to_pfn(p), tsk->comm);
+                tk->addr_valid = 0;
+        }
+        get_task_struct(tsk);
+        tk->tsk = tsk;
+        list_add_tail(&tk->nd, to_kill);
+}
+
+/*
+ * Kill the processes that have been collected earlier.
+ *
+ * Only do anything when DOIT is set, otherwise just free the list
+ * (this is used for clean pages which do not need killing)
+ * Also when FAIL is set do a force kill because something went
+ * wrong earlier.
+ */
+static void kill_procs_ao(struct list_head *to_kill, int doit, int trapno,
+                          int fail, unsigned long pfn)
+{
+        struct to_kill *tk, *next;
+
+        list_for_each_entry_safe (tk, next, to_kill, nd) {
+                if (doit) {
+                        /*
+                         * In case something went wrong with munmaping
+                         * make sure the process doesn't catch the
+                         * signal and then access the memory. Just kill it.
+                         * the signal handlers
+                         */
+                        if (fail || tk->addr_valid == 0) {
+                                printk(KERN_ERR
+                "MCE %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n",
+                                        pfn, tk->tsk->comm, tk->tsk->pid);
+                                force_sig(SIGKILL, tk->tsk);
+                        }
+
+                        /*
+                         * In theory the process could have mapped
+                         * something else on the address in-between. We could
+                         * check for that, but we need to tell the
+                         * process anyways.
+                         */
+                        else if (kill_proc_ao(tk->tsk, tk->addr, trapno,
+                                              pfn) < 0)
+                                printk(KERN_ERR
+                "MCE %#lx: Cannot send advisory machine check signal to %s:%d\n",
+                                        pfn, tk->tsk->comm, tk->tsk->pid);
+                }
+                put_task_struct(tk->tsk);
+                kfree(tk);
+        }
+}
+
+static int task_early_kill(struct task_struct *tsk)
+{
+        if (!tsk->mm)
+                return 0;
+        if (tsk->flags & PF_MCE_PROCESS)
+                return !!(tsk->flags & PF_MCE_EARLY);
+        return sysctl_memory_failure_early_kill;
+}
+
+/*
+ * Collect processes when the error hit an anonymous page.
+ */
+static void collect_procs_anon(struct page *page, struct list_head *to_kill,
+                              struct to_kill **tkc)
+{
+        struct vm_area_struct *vma;
+        struct task_struct *tsk;
+        struct anon_vma *av;
+
+        read_lock(&tasklist_lock);
+        av = page_lock_anon_vma(page);
+        if (av == NULL) /* Not actually mapped anymore */
+                goto out;
+        for_each_process (tsk) {
+                if (!task_early_kill(tsk))
+                        continue;
+                list_for_each_entry (vma, &av->head, anon_vma_node) {
+                        if (!page_mapped_in_vma(page, vma))
+                                continue;
+                        if (vma->vm_mm == tsk->mm)
+                                add_to_kill(tsk, page, vma, to_kill, tkc);
+                }
+        }
+        page_unlock_anon_vma(av);
+out:
+        read_unlock(&tasklist_lock);
+}
+
+/*
+ * Collect processes when the error hit a file mapped page.
+ */
+static void collect_procs_file(struct page *page, struct list_head *to_kill,
+                              struct to_kill **tkc)
+{
+        struct vm_area_struct *vma;
+        struct task_struct *tsk;
+        struct prio_tree_iter iter;
+        struct address_space *mapping = page->mapping;
+
+        /*
+         * A note on the locking order between the two locks.
+         * We don't rely on this particular order.
+         * If you have some other code that needs a different order
+         * feel free to switch them around. Or add a reverse link
+         * from mm_struct to task_struct, then this could be all
+         * done without taking tasklist_lock and looping over all tasks.
+         */
+
+        read_lock(&tasklist_lock);
+        spin_lock(&mapping->i_mmap_lock);
+        for_each_process(tsk) {
+                pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
+
+                if (!task_early_kill(tsk))
+                        continue;
+
+                vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff,
+                                      pgoff) {
+                        /*
+                         * Send early kill signal to tasks where a vma covers
+                         * the page but the corrupted page is not necessarily
+                         * mapped it in its pte.
+                         * Assume applications who requested early kill want
+                         * to be informed of all such data corruptions.
+                         */
+                        if (vma->vm_mm == tsk->mm)
+                                add_to_kill(tsk, page, vma, to_kill, tkc);
+                }
+        }
+        spin_unlock(&mapping->i_mmap_lock);
+        read_unlock(&tasklist_lock);
+}
+
+/*
+ * Collect the processes who have the corrupted page mapped to kill.
+ * This is done in two steps for locking reasons.
+ * First preallocate one tokill structure outside the spin locks,
+ * so that we can kill at least one process reasonably reliable.
+ */
+static void collect_procs(struct page *page, struct list_head *tokill)
+{
+        struct to_kill *tk;
+
+        if (!page->mapping)
+                return;
+
+        tk = kmalloc(sizeof(struct to_kill), GFP_NOIO);
+        if (!tk)
+                return;
+        if (PageAnon(page))
+                collect_procs_anon(page, tokill, &tk);
+        else
+                collect_procs_file(page, tokill, &tk);
+        kfree(tk);
+}
+
+/*
+ * Error handlers for various types of pages.
+ */
+
+enum outcome {
+        FAILED,         /* Error handling failed */
+        DELAYED,        /* Will be handled later */
+        IGNORED,        /* Error safely ignored */
+        RECOVERED,      /* Successfully recovered */
+};
+
+static const char *action_name[] = {
+        [FAILED] = "Failed",
+        [DELAYED] = "Delayed",
+        [IGNORED] = "Ignored",
+        [RECOVERED] = "Recovered",
+};
+
+/*
+ * Error hit kernel page.
+ * Do nothing, try to be lucky and not touch this instead. For a few cases we
+ * could be more sophisticated.
+ */
+static int me_kernel(struct page *p, unsigned long pfn)
+{
+        return DELAYED;
+}
+
+/*
+ * Already poisoned page.
+ */
+static int me_ignore(struct page *p, unsigned long pfn)
+{
+        return IGNORED;
+}
+
+/*
+ * Page in unknown state. Do nothing.
+ */
+static int me_unknown(struct page *p, unsigned long pfn)
+{
+        printk(KERN_ERR "MCE %#lx: Unknown page state\n", pfn);
+        return FAILED;
+}
+
+/*
+ * Free memory
+ */
+static int me_free(struct page *p, unsigned long pfn)
+{
+        return DELAYED;
+}
+
+/*
+ * Clean (or cleaned) page cache page.
+ */
+static int me_pagecache_clean(struct page *p, unsigned long pfn)
+{
+        int err;
+        int ret = FAILED;
+        struct address_space *mapping;
+
+        if (!isolate_lru_page(p))
+                page_cache_release(p);
+
+        /*
+         * For anonymous pages we're done the only reference left
+         * should be the one m_f() holds.
+         */
+        if (PageAnon(p))
+                return RECOVERED;
+
+        /*
+         * Now truncate the page in the page cache. This is really
+         * more like a "temporary hole punch"
+         * Don't do this for block devices when someone else
+         * has a reference, because it could be file system metadata
+         * and that's not safe to truncate.
+         */
+        mapping = page_mapping(p);
+        if (!mapping) {
+                /*
+                 * Page has been teared down in the meanwhile
+                 */
+                return FAILED;
+        }
+
+        /*
+         * Truncation is a bit tricky. Enable it per file system for now.
+         *
+         * Open: to take i_mutex or not for this? Right now we don't.
+         */
+        if (mapping->a_ops->error_remove_page) {
+                err = mapping->a_ops->error_remove_page(mapping, p);
+                if (err != 0) {
+                        printk(KERN_INFO "MCE %#lx: Failed to punch page: %d\n",
+                                        pfn, err);
+                } else if (page_has_private(p) &&
+                                !try_to_release_page(p, GFP_NOIO)) {
+                        pr_debug("MCE %#lx: failed to release buffers\n", pfn);
+                } else {
+                        ret = RECOVERED;
+                }
+        } else {
+                /*
+                 * If the file system doesn't support it just invalidate
+                 * This fails on dirty or anything with private pages
+                 */
+                if (invalidate_inode_page(p))
+                        ret = RECOVERED;
+                else
+                        printk(KERN_INFO "MCE %#lx: Failed to invalidate\n",
+                                pfn);
+        }
+        return ret;
+}
+
+/*
+ * Dirty cache page page
+ * Issues: when the error hit a hole page the error is not properly
+ * propagated.
+ */
+static int me_pagecache_dirty(struct page *p, unsigned long pfn)
+{
+        struct address_space *mapping = page_mapping(p);
+
+        SetPageError(p);
+        /* TBD: print more information about the file. */
+        if (mapping) {
+                /*
+                 * IO error will be reported by write(), fsync(), etc.
+                 * who check the mapping.
+                 * This way the application knows that something went
+                 * wrong with its dirty file data.
+                 *
+                 * There's one open issue:
+                 *
+                 * The EIO will be only reported on the next IO
+                 * operation and then cleared through the IO map.
+                 * Normally Linux has two mechanisms to pass IO error
+                 * first through the AS_EIO flag in the address space
+                 * and then through the PageError flag in the page.
+                 * Since we drop pages on memory failure handling the
+                 * only mechanism open to use is through AS_AIO.
+                 *
+                 * This has the disadvantage that it gets cleared on
+                 * the first operation that returns an error, while
+                 * the PageError bit is more sticky and only cleared
+                 * when the page is reread or dropped.  If an
+                 * application assumes it will always get error on
+                 * fsync, but does other operations on the fd before
+                 * and the page is dropped inbetween then the error
+                 * will not be properly reported.
+                 *
+                 * This can already happen even without hwpoisoned
+                 * pages: first on metadata IO errors (which only
+                 * report through AS_EIO) or when the page is dropped
+                 * at the wrong time.
+                 *
+                 * So right now we assume that the application DTRT on
+                 * the first EIO, but we're not worse than other parts
+                 * of the kernel.
+                 */
+                mapping_set_error(mapping, EIO);
+        }
+
+        return me_pagecache_clean(p, pfn);
+}
+
+/*
+ * Clean and dirty swap cache.
+ *
+ * Dirty swap cache page is tricky to handle. The page could live both in page
+ * cache and swap cache(ie. page is freshly swapped in). So it could be
+ * referenced concurrently by 2 types of PTEs:
+ * normal PTEs and swap PTEs. We try to handle them consistently by calling
+ * try_to_unmap(TTU_IGNORE_HWPOISON) to convert the normal PTEs to swap PTEs,
+ * and then
+ *      - clear dirty bit to prevent IO
+ *      - remove from LRU
+ *      - but keep in the swap cache, so that when we return to it on
+ *        a later page fault, we know the application is accessing
+ *        corrupted data and shall be killed (we installed simple
+ *        interception code in do_swap_page to catch it).
+ *
+ * Clean swap cache pages can be directly isolated. A later page fault will
+ * bring in the known good data from disk.
+ */
+static int me_swapcache_dirty(struct page *p, unsigned long pfn)
+{
+        int ret = FAILED;
+
+        ClearPageDirty(p);
+        /* Trigger EIO in shmem: */
+        ClearPageUptodate(p);
+
+        if (!isolate_lru_page(p)) {
+                page_cache_release(p);
+                ret = DELAYED;
+        }
+
+        return ret;
+}
+
+static int me_swapcache_clean(struct page *p, unsigned long pfn)
+{
+        int ret = FAILED;
+
+        if (!isolate_lru_page(p)) {
+                page_cache_release(p);
+                ret = RECOVERED;
+        }
+        delete_from_swap_cache(p);
+        return ret;
+}
+
+/*
+ * Huge pages. Needs work.
+ * Issues:
+ * No rmap support so we cannot find the original mapper. In theory could walk
+ * all MMs and look for the mappings, but that would be non atomic and racy.
+ * Need rmap for hugepages for this. Alternatively we could employ a heuristic,
+ * like just walking the current process and hoping it has it mapped (that
+ * should be usually true for the common "shared database cache" case)
+ * Should handle free huge pages and dequeue them too, but this needs to
+ * handle huge page accounting correctly.
+ */
+static int me_huge_page(struct page *p, unsigned long pfn)
+{
+        return FAILED;
+}
+
+/*
+ * Various page states we can handle.
+ *
+ * A page state is defined by its current page->flags bits.
+ * The table matches them in order and calls the right handler.
+ *
+ * This is quite tricky because we can access page at any time
+ * in its live cycle, so all accesses have to be extremly careful.
+ *
+ * This is not complete. More states could be added.
+ * For any missing state don't attempt recovery.
+ */
+
+#define dirty           (1UL << PG_dirty)
+#define sc              (1UL << PG_swapcache)
+#define unevict         (1UL << PG_unevictable)
+#define mlock           (1UL << PG_mlocked)
+#define writeback       (1UL << PG_writeback)
+#define lru             (1UL << PG_lru)
+#define swapbacked      (1UL << PG_swapbacked)
+#define head            (1UL << PG_head)
+#define tail            (1UL << PG_tail)
+#define compound        (1UL << PG_compound)
+#define slab            (1UL << PG_slab)
+#define buddy           (1UL << PG_buddy)
+#define reserved        (1UL << PG_reserved)
+
+static struct page_state {
+        unsigned long mask;
+        unsigned long res;
+        char *msg;
+        int (*action)(struct page *p, unsigned long pfn);
+} error_states[] = {
+        { reserved,     reserved,       "reserved kernel",      me_ignore },
+        { buddy,        buddy,          "free kernel",  me_free },
+
+        /*
+         * Could in theory check if slab page is free or if we can drop
+         * currently unused objects without touching them. But just
+         * treat it as standard kernel for now.
+         */
+        { slab,         slab,           "kernel slab",  me_kernel },
+
+#ifdef CONFIG_PAGEFLAGS_EXTENDED
+        { head,         head,           "huge",         me_huge_page },
+        { tail,         tail,           "huge",         me_huge_page },
+#else
+        { compound,     compound,       "huge",         me_huge_page },
+#endif
+
+        { sc|dirty,     sc|dirty,       "swapcache",    me_swapcache_dirty },
+        { sc|dirty,     sc,             "swapcache",    me_swapcache_clean },
+
+        { unevict|dirty, unevict|dirty, "unevictable LRU", me_pagecache_dirty},
+        { unevict,      unevict,        "unevictable LRU", me_pagecache_clean},
+
+#ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
+        { mlock|dirty,  mlock|dirty,    "mlocked LRU",  me_pagecache_dirty },
+        { mlock,        mlock,          "mlocked LRU",  me_pagecache_clean },
+#endif
+
+        { lru|dirty,    lru|dirty,      "LRU",          me_pagecache_dirty },
+        { lru|dirty,    lru,            "clean LRU",    me_pagecache_clean },
+        { swapbacked,   swapbacked,     "anonymous",    me_pagecache_clean },
+
+        /*
+         * Catchall entry: must be at end.
+         */
+        { 0,            0,              "unknown page state",   me_unknown },
+};
+
+#undef lru
+
+static void action_result(unsigned long pfn, char *msg, int result)
+{
+        struct page *page = NULL;
+        if (pfn_valid(pfn))
+                page = pfn_to_page(pfn);
+
+        printk(KERN_ERR "MCE %#lx: %s%s page recovery: %s\n",
+                pfn,
+                page && PageDirty(page) ? "dirty " : "",
+                msg, action_name[result]);
+}
+
+static int page_action(struct page_state *ps, struct page *p,
+                        unsigned long pfn, int ref)
+{
+        int result;
+
+        result = ps->action(p, pfn);
+        action_result(pfn, ps->msg, result);
+        if (page_count(p) != 1 + ref)
+                printk(KERN_ERR
+                       "MCE %#lx: %s page still referenced by %d users\n",
+                       pfn, ps->msg, page_count(p) - 1);
+
+        /* Could do more checks here if page looks ok */
+        /*
+         * Could adjust zone counters here to correct for the missing page.
+         */
+
+        return result == RECOVERED ? 0 : -EBUSY;
+}
+
+#define N_UNMAP_TRIES 5
+
+/*
+ * Do all that is necessary to remove user space mappings. Unmap
+ * the pages and send SIGBUS to the processes if the data was dirty.
+ */
+static void hwpoison_user_mappings(struct page *p, unsigned long pfn,
+                                  int trapno)
+{
+        enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
+        struct address_space *mapping;
+        LIST_HEAD(tokill);
+        int ret;
+        int i;
+        int kill = 1;
+
+        if (PageReserved(p) || PageCompound(p) || PageSlab(p))
+                return;
+
+        if (!PageLRU(p))
+                lru_add_drain_all();
+
+        /*
+         * This check implies we don't kill processes if their pages
+         * are in the swap cache early. Those are always late kills.
+         */
+        if (!page_mapped(p))
+                return;
+
+        if (PageSwapCache(p)) {
+                printk(KERN_ERR
+                       "MCE %#lx: keeping poisoned page in swap cache\n", pfn);
+                ttu |= TTU_IGNORE_HWPOISON;
+        }
+
+        /*
+         * Propagate the dirty bit from PTEs to struct page first, because we
+         * need this to decide if we should kill or just drop the page.
+         */
+        mapping = page_mapping(p);
+        if (!PageDirty(p) && mapping && mapping_cap_writeback_dirty(mapping)) {
+                if (page_mkclean(p)) {
+                        SetPageDirty(p);
+                } else {
+                        kill = 0;
+                        ttu |= TTU_IGNORE_HWPOISON;
+                        printk(KERN_INFO
+        "MCE %#lx: corrupted page was clean: dropped without side effects\n",
+                                pfn);
+                }
+        }
+
+        /*
+         * First collect all the processes that have the page
+         * mapped in dirty form.  This has to be done before try_to_unmap,
+         * because ttu takes the rmap data structures down.
+         *
+         * Error handling: We ignore errors here because
+         * there's nothing that can be done.
+         */
+        if (kill)
+                collect_procs(p, &tokill);
+
+        /*
+         * try_to_unmap can fail temporarily due to races.
+         * Try a few times (RED-PEN better strategy?)
+         */
+        for (i = 0; i < N_UNMAP_TRIES; i++) {
+                ret = try_to_unmap(p, ttu);
+                if (ret == SWAP_SUCCESS)
+                        break;
+                pr_debug("MCE %#lx: try_to_unmap retry needed %d\n", pfn,  ret);
+        }
+
+        if (ret != SWAP_SUCCESS)
+                printk(KERN_ERR "MCE %#lx: failed to unmap page (mapcount=%d)\n",
+                                pfn, page_mapcount(p));
+
+        /*
+         * Now that the dirty bit has been propagated to the
+         * struct page and all unmaps done we can decide if
+         * killing is needed or not.  Only kill when the page
+         * was dirty, otherwise the tokill list is merely
+         * freed.  When there was a problem unmapping earlier
+         * use a more force-full uncatchable kill to prevent
+         * any accesses to the poisoned memory.
+         */
+        kill_procs_ao(&tokill, !!PageDirty(p), trapno,
+                      ret != SWAP_SUCCESS, pfn);
+}
+
+int __memory_failure(unsigned long pfn, int trapno, int ref)
+{
+        struct page_state *ps;
+        struct page *p;
+        int res;
+
+        if (!sysctl_memory_failure_recovery)
+                panic("Memory failure from trap %d on page %lx", trapno, pfn);
+
+        if (!pfn_valid(pfn)) {
+                action_result(pfn, "memory outside kernel control", IGNORED);
+                return -EIO;
+        }
+
+        p = pfn_to_page(pfn);
+        if (TestSetPageHWPoison(p)) {
+                action_result(pfn, "already hardware poisoned", IGNORED);
+                return 0;
+        }
+
+        atomic_long_add(1, &mce_bad_pages);
+
+        /*
+         * We need/can do nothing about count=0 pages.
+         * 1) it's a free page, and therefore in safe hand:
+         *    prep_new_page() will be the gate keeper.
+         * 2) it's part of a non-compound high order page.
+         *    Implies some kernel user: cannot stop them from
+         *    R/W the page; let's pray that the page has been
+         *    used and will be freed some time later.
+         * In fact it's dangerous to directly bump up page count from 0,
+         * that may make page_freeze_refs()/page_unfreeze_refs() mismatch.
+         */
+        if (!get_page_unless_zero(compound_head(p))) {
+                action_result(pfn, "free or high order kernel", IGNORED);
+                return PageBuddy(compound_head(p)) ? 0 : -EBUSY;
+        }
+
+        /*
+         * Lock the page and wait for writeback to finish.
+         * It's very difficult to mess with pages currently under IO
+         * and in many cases impossible, so we just avoid it here.
+         */
+        lock_page_nosync(p);
+        wait_on_page_writeback(p);
+
+        /*
+         * Now take care of user space mappings.
+         */
+        hwpoison_user_mappings(p, pfn, trapno);
+
+        /*
+         * Torn down by someone else?
+         */
+        if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) {
+                action_result(pfn, "already truncated LRU", IGNORED);
+                res = 0;
+                goto out;
+        }
+
+        res = -EBUSY;
+        for (ps = error_states;; ps++) {
+                if ((p->flags & ps->mask) == ps->res) {
+                        res = page_action(ps, p, pfn, ref);
+                        break;
+                }
+        }
+out:
+        unlock_page(p);
+        return res;
+}
+EXPORT_SYMBOL_GPL(__memory_failure);
+
+/**
+ * memory_failure - Handle memory failure of a page.
+ * @pfn: Page Number of the corrupted page
+ * @trapno: Trap number reported in the signal to user space.
+ *
+ * This function is called by the low level machine check code
+ * of an architecture when it detects hardware memory corruption
+ * of a page. It tries its best to recover, which includes
+ * dropping pages, killing processes etc.
+ *
+ * The function is primarily of use for corruptions that
+ * happen outside the current execution context (e.g. when
+ * detected by a background scrubber)
+ *
+ * Must run in process context (e.g. a work queue) with interrupts
+ * enabled and no spinlocks hold.
+ */
+void memory_failure(unsigned long pfn, int trapno)
+{
+        __memory_failure(pfn, trapno, 0);
+}