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@@ -0,0 +1,832 @@
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+/*
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+ * Copyright (C) 2008, 2009 Intel Corporation
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+ * Authors: Andi Kleen, Fengguang Wu
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+ *
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+ * This software may be redistributed and/or modified under the terms of
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+ * the GNU General Public License ("GPL") version 2 only as published by the
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+ * Free Software Foundation.
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+ *
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+ * High level machine check handler. Handles pages reported by the
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+ * hardware as being corrupted usually due to a 2bit ECC memory or cache
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+ * failure.
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+ *
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+ * Handles page cache pages in various states. The tricky part
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+ * here is that we can access any page asynchronous to other VM
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+ * users, because memory failures could happen anytime and anywhere,
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+ * possibly violating some of their assumptions. This is why this code
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+ * has to be extremely careful. Generally it tries to use normal locking
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+ * rules, as in get the standard locks, even if that means the
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+ * error handling takes potentially a long time.
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+ *
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+ * The operation to map back from RMAP chains to processes has to walk
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+ * the complete process list and has non linear complexity with the number
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+ * mappings. In short it can be quite slow. But since memory corruptions
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+ * are rare we hope to get away with this.
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+ */
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+
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+/*
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+ * Notebook:
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+ * - hugetlb needs more code
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+ * - kcore/oldmem/vmcore/mem/kmem check for hwpoison pages
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+ * - pass bad pages to kdump next kernel
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+ */
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+#define DEBUG 1 /* remove me in 2.6.34 */
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+#include <linux/kernel.h>
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+#include <linux/mm.h>
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+#include <linux/page-flags.h>
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+#include <linux/sched.h>
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+#include <linux/rmap.h>
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+#include <linux/pagemap.h>
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+#include <linux/swap.h>
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+#include <linux/backing-dev.h>
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+#include "internal.h"
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+
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+int sysctl_memory_failure_early_kill __read_mostly = 0;
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+
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+int sysctl_memory_failure_recovery __read_mostly = 1;
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+
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+atomic_long_t mce_bad_pages __read_mostly = ATOMIC_LONG_INIT(0);
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+
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+/*
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+ * Send all the processes who have the page mapped an ``action optional''
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+ * signal.
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+ */
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+static int kill_proc_ao(struct task_struct *t, unsigned long addr, int trapno,
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+ unsigned long pfn)
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+{
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+ struct siginfo si;
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+ int ret;
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+
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+ printk(KERN_ERR
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+ "MCE %#lx: Killing %s:%d early due to hardware memory corruption\n",
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+ pfn, t->comm, t->pid);
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+ si.si_signo = SIGBUS;
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+ si.si_errno = 0;
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+ si.si_code = BUS_MCEERR_AO;
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+ si.si_addr = (void *)addr;
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+#ifdef __ARCH_SI_TRAPNO
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+ si.si_trapno = trapno;
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+#endif
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+ si.si_addr_lsb = PAGE_SHIFT;
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+ /*
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+ * Don't use force here, it's convenient if the signal
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+ * can be temporarily blocked.
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+ * This could cause a loop when the user sets SIGBUS
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+ * to SIG_IGN, but hopefully noone will do that?
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+ */
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+ ret = send_sig_info(SIGBUS, &si, t); /* synchronous? */
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+ if (ret < 0)
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+ printk(KERN_INFO "MCE: Error sending signal to %s:%d: %d\n",
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+ t->comm, t->pid, ret);
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+ return ret;
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+}
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+
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+/*
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+ * Kill all processes that have a poisoned page mapped and then isolate
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+ * the page.
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+ *
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+ * General strategy:
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+ * Find all processes having the page mapped and kill them.
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+ * But we keep a page reference around so that the page is not
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+ * actually freed yet.
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+ * Then stash the page away
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+ *
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+ * There's no convenient way to get back to mapped processes
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+ * from the VMAs. So do a brute-force search over all
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+ * running processes.
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+ *
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+ * Remember that machine checks are not common (or rather
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+ * if they are common you have other problems), so this shouldn't
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+ * be a performance issue.
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+ *
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+ * Also there are some races possible while we get from the
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+ * error detection to actually handle it.
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+ */
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+
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+struct to_kill {
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+ struct list_head nd;
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+ struct task_struct *tsk;
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+ unsigned long addr;
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+ unsigned addr_valid:1;
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+};
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+
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+/*
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+ * Failure handling: if we can't find or can't kill a process there's
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+ * not much we can do. We just print a message and ignore otherwise.
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+ */
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+
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+/*
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+ * Schedule a process for later kill.
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+ * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
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+ * TBD would GFP_NOIO be enough?
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+ */
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+static void add_to_kill(struct task_struct *tsk, struct page *p,
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+ struct vm_area_struct *vma,
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+ struct list_head *to_kill,
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+ struct to_kill **tkc)
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+{
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+ struct to_kill *tk;
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+
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+ if (*tkc) {
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+ tk = *tkc;
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+ *tkc = NULL;
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+ } else {
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+ tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
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+ if (!tk) {
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+ printk(KERN_ERR
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+ "MCE: Out of memory while machine check handling\n");
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+ return;
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+ }
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+ }
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+ tk->addr = page_address_in_vma(p, vma);
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+ tk->addr_valid = 1;
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+
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+ /*
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+ * In theory we don't have to kill when the page was
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+ * munmaped. But it could be also a mremap. Since that's
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+ * likely very rare kill anyways just out of paranoia, but use
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+ * a SIGKILL because the error is not contained anymore.
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+ */
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+ if (tk->addr == -EFAULT) {
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+ pr_debug("MCE: Unable to find user space address %lx in %s\n",
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+ page_to_pfn(p), tsk->comm);
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+ tk->addr_valid = 0;
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+ }
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+ get_task_struct(tsk);
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+ tk->tsk = tsk;
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+ list_add_tail(&tk->nd, to_kill);
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+}
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+
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+/*
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+ * Kill the processes that have been collected earlier.
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+ *
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+ * Only do anything when DOIT is set, otherwise just free the list
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+ * (this is used for clean pages which do not need killing)
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+ * Also when FAIL is set do a force kill because something went
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+ * wrong earlier.
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+ */
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+static void kill_procs_ao(struct list_head *to_kill, int doit, int trapno,
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+ int fail, unsigned long pfn)
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+{
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+ struct to_kill *tk, *next;
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+
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+ list_for_each_entry_safe (tk, next, to_kill, nd) {
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+ if (doit) {
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+ /*
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+ * In case something went wrong with munmaping
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+ * make sure the process doesn't catch the
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+ * signal and then access the memory. Just kill it.
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+ * the signal handlers
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+ */
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+ if (fail || tk->addr_valid == 0) {
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+ printk(KERN_ERR
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+ "MCE %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n",
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+ pfn, tk->tsk->comm, tk->tsk->pid);
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+ force_sig(SIGKILL, tk->tsk);
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+ }
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+
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+ /*
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+ * In theory the process could have mapped
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+ * something else on the address in-between. We could
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+ * check for that, but we need to tell the
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+ * process anyways.
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+ */
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+ else if (kill_proc_ao(tk->tsk, tk->addr, trapno,
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+ pfn) < 0)
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+ printk(KERN_ERR
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+ "MCE %#lx: Cannot send advisory machine check signal to %s:%d\n",
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+ pfn, tk->tsk->comm, tk->tsk->pid);
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+ }
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+ put_task_struct(tk->tsk);
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+ kfree(tk);
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+ }
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+}
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+
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+static int task_early_kill(struct task_struct *tsk)
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+{
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+ if (!tsk->mm)
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+ return 0;
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+ if (tsk->flags & PF_MCE_PROCESS)
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+ return !!(tsk->flags & PF_MCE_EARLY);
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+ return sysctl_memory_failure_early_kill;
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+}
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+
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+/*
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+ * Collect processes when the error hit an anonymous page.
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+ */
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+static void collect_procs_anon(struct page *page, struct list_head *to_kill,
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+ struct to_kill **tkc)
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+{
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+ struct vm_area_struct *vma;
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+ struct task_struct *tsk;
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+ struct anon_vma *av;
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+
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+ read_lock(&tasklist_lock);
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+ av = page_lock_anon_vma(page);
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+ if (av == NULL) /* Not actually mapped anymore */
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+ goto out;
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+ for_each_process (tsk) {
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+ if (!task_early_kill(tsk))
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+ continue;
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+ list_for_each_entry (vma, &av->head, anon_vma_node) {
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+ if (!page_mapped_in_vma(page, vma))
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+ continue;
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+ if (vma->vm_mm == tsk->mm)
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+ add_to_kill(tsk, page, vma, to_kill, tkc);
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+ }
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+ }
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+ page_unlock_anon_vma(av);
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+out:
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+ read_unlock(&tasklist_lock);
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+}
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+
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+/*
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+ * Collect processes when the error hit a file mapped page.
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+ */
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+static void collect_procs_file(struct page *page, struct list_head *to_kill,
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+ struct to_kill **tkc)
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+{
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+ struct vm_area_struct *vma;
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+ struct task_struct *tsk;
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+ struct prio_tree_iter iter;
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+ struct address_space *mapping = page->mapping;
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+
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+ /*
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+ * A note on the locking order between the two locks.
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+ * We don't rely on this particular order.
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+ * If you have some other code that needs a different order
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+ * feel free to switch them around. Or add a reverse link
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+ * from mm_struct to task_struct, then this could be all
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+ * done without taking tasklist_lock and looping over all tasks.
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+ */
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+
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+ read_lock(&tasklist_lock);
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+ spin_lock(&mapping->i_mmap_lock);
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+ for_each_process(tsk) {
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+ pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
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+
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+ if (!task_early_kill(tsk))
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+ continue;
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+
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+ vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff,
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+ pgoff) {
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+ /*
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+ * Send early kill signal to tasks where a vma covers
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+ * the page but the corrupted page is not necessarily
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+ * mapped it in its pte.
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+ * Assume applications who requested early kill want
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+ * to be informed of all such data corruptions.
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+ */
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+ if (vma->vm_mm == tsk->mm)
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+ add_to_kill(tsk, page, vma, to_kill, tkc);
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+ }
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+ }
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+ spin_unlock(&mapping->i_mmap_lock);
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+ read_unlock(&tasklist_lock);
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+}
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+
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+/*
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+ * Collect the processes who have the corrupted page mapped to kill.
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+ * This is done in two steps for locking reasons.
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+ * First preallocate one tokill structure outside the spin locks,
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+ * so that we can kill at least one process reasonably reliable.
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+ */
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+static void collect_procs(struct page *page, struct list_head *tokill)
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+{
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+ struct to_kill *tk;
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+
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+ if (!page->mapping)
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+ return;
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+
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+ tk = kmalloc(sizeof(struct to_kill), GFP_NOIO);
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+ if (!tk)
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+ return;
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+ if (PageAnon(page))
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+ collect_procs_anon(page, tokill, &tk);
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+ else
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+ collect_procs_file(page, tokill, &tk);
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+ kfree(tk);
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+}
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+
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+/*
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+ * Error handlers for various types of pages.
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+ */
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+
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+enum outcome {
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+ FAILED, /* Error handling failed */
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+ DELAYED, /* Will be handled later */
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+ IGNORED, /* Error safely ignored */
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+ RECOVERED, /* Successfully recovered */
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+};
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+
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+static const char *action_name[] = {
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+ [FAILED] = "Failed",
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+ [DELAYED] = "Delayed",
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+ [IGNORED] = "Ignored",
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+ [RECOVERED] = "Recovered",
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+};
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+
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+/*
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+ * Error hit kernel page.
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+ * Do nothing, try to be lucky and not touch this instead. For a few cases we
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+ * could be more sophisticated.
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+ */
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+static int me_kernel(struct page *p, unsigned long pfn)
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+{
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+ return DELAYED;
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+}
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+
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+/*
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+ * Already poisoned page.
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+ */
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+static int me_ignore(struct page *p, unsigned long pfn)
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+{
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+ return IGNORED;
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+}
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+
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+/*
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+ * Page in unknown state. Do nothing.
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+ */
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+static int me_unknown(struct page *p, unsigned long pfn)
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+{
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+ printk(KERN_ERR "MCE %#lx: Unknown page state\n", pfn);
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+ return FAILED;
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+}
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+
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+/*
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+ * Free memory
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+ */
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+static int me_free(struct page *p, unsigned long pfn)
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+{
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+ return DELAYED;
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+}
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+
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+/*
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+ * Clean (or cleaned) page cache page.
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+ */
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+static int me_pagecache_clean(struct page *p, unsigned long pfn)
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+{
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+ int err;
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+ int ret = FAILED;
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+ struct address_space *mapping;
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+
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+ if (!isolate_lru_page(p))
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+ page_cache_release(p);
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+
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+ /*
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+ * For anonymous pages we're done the only reference left
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+ * should be the one m_f() holds.
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+ */
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+ if (PageAnon(p))
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+ return RECOVERED;
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+
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+ /*
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+ * Now truncate the page in the page cache. This is really
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+ * more like a "temporary hole punch"
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+ * Don't do this for block devices when someone else
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+ * has a reference, because it could be file system metadata
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+ * and that's not safe to truncate.
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+ */
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+ mapping = page_mapping(p);
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+ if (!mapping) {
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+ /*
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+ * Page has been teared down in the meanwhile
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+ */
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+ return FAILED;
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+ }
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+
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+ /*
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+ * Truncation is a bit tricky. Enable it per file system for now.
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+ *
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+ * Open: to take i_mutex or not for this? Right now we don't.
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+ */
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+ if (mapping->a_ops->error_remove_page) {
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+ err = mapping->a_ops->error_remove_page(mapping, p);
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+ if (err != 0) {
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+ printk(KERN_INFO "MCE %#lx: Failed to punch page: %d\n",
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+ pfn, err);
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+ } else if (page_has_private(p) &&
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+ !try_to_release_page(p, GFP_NOIO)) {
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+ pr_debug("MCE %#lx: failed to release buffers\n", pfn);
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+ } else {
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+ ret = RECOVERED;
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+ }
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+ } else {
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+ /*
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+ * If the file system doesn't support it just invalidate
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+ * This fails on dirty or anything with private pages
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|
+ */
|
|
|
+ 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
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+ * enabled and no spinlocks hold.
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+ */
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+void memory_failure(unsigned long pfn, int trapno)
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+{
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+ __memory_failure(pfn, trapno, 0);
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+}
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Linus Torvalds