memory-failure.c 49.2 KB
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/*
 * 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
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 * hardware as being corrupted usually due to a multi-bit ECC memory or cache
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 * failure.
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 * 
 * In addition there is a "soft offline" entry point that allows stop using
 * not-yet-corrupted-by-suspicious pages without killing anything.
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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 asynchronously in respect to 
 * other VM users, because memory failures could happen anytime and 
 * anywhere. This could violate 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.
 * 
 * There are several operations here with exponential complexity because
 * of unsuitable VM data structures. For example 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. But since memory corruptions
 * are rare we hope to get away with this. This avoids impacting the core 
 * VM.
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 */

/*
 * Notebook:
 * - hugetlb needs more code
 * - kcore/oldmem/vmcore/mem/kmem check for hwpoison pages
 * - pass bad pages to kdump next kernel
 */
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/page-flags.h>
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#include <linux/kernel-page-flags.h>
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#include <linux/sched.h>
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#include <linux/ksm.h>
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#include <linux/rmap.h>
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#include <linux/export.h>
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#include <linux/pagemap.h>
#include <linux/swap.h>
#include <linux/backing-dev.h>
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#include <linux/migrate.h>
#include <linux/page-isolation.h>
#include <linux/suspend.h>
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#include <linux/slab.h>
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#include <linux/swapops.h>
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#include <linux/hugetlb.h>
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#include <linux/memory_hotplug.h>
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#include <linux/mm_inline.h>
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#include <linux/kfifo.h>
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#include "internal.h"

int sysctl_memory_failure_early_kill __read_mostly = 0;

int sysctl_memory_failure_recovery __read_mostly = 1;

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atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0);
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#if defined(CONFIG_HWPOISON_INJECT) || defined(CONFIG_HWPOISON_INJECT_MODULE)

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u32 hwpoison_filter_enable = 0;
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u32 hwpoison_filter_dev_major = ~0U;
u32 hwpoison_filter_dev_minor = ~0U;
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u64 hwpoison_filter_flags_mask;
u64 hwpoison_filter_flags_value;
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EXPORT_SYMBOL_GPL(hwpoison_filter_enable);
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EXPORT_SYMBOL_GPL(hwpoison_filter_dev_major);
EXPORT_SYMBOL_GPL(hwpoison_filter_dev_minor);
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EXPORT_SYMBOL_GPL(hwpoison_filter_flags_mask);
EXPORT_SYMBOL_GPL(hwpoison_filter_flags_value);
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static int hwpoison_filter_dev(struct page *p)
{
	struct address_space *mapping;
	dev_t dev;

	if (hwpoison_filter_dev_major == ~0U &&
	    hwpoison_filter_dev_minor == ~0U)
		return 0;

	/*
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	 * page_mapping() does not accept slab pages.
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	 */
	if (PageSlab(p))
		return -EINVAL;

	mapping = page_mapping(p);
	if (mapping == NULL || mapping->host == NULL)
		return -EINVAL;

	dev = mapping->host->i_sb->s_dev;
	if (hwpoison_filter_dev_major != ~0U &&
	    hwpoison_filter_dev_major != MAJOR(dev))
		return -EINVAL;
	if (hwpoison_filter_dev_minor != ~0U &&
	    hwpoison_filter_dev_minor != MINOR(dev))
		return -EINVAL;

	return 0;
}

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static int hwpoison_filter_flags(struct page *p)
{
	if (!hwpoison_filter_flags_mask)
		return 0;

	if ((stable_page_flags(p) & hwpoison_filter_flags_mask) ==
				    hwpoison_filter_flags_value)
		return 0;
	else
		return -EINVAL;
}

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/*
 * This allows stress tests to limit test scope to a collection of tasks
 * by putting them under some memcg. This prevents killing unrelated/important
 * processes such as /sbin/init. Note that the target task may share clean
 * pages with init (eg. libc text), which is harmless. If the target task
 * share _dirty_ pages with another task B, the test scheme must make sure B
 * is also included in the memcg. At last, due to race conditions this filter
 * can only guarantee that the page either belongs to the memcg tasks, or is
 * a freed page.
 */
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#ifdef	CONFIG_MEMCG_SWAP
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u64 hwpoison_filter_memcg;
EXPORT_SYMBOL_GPL(hwpoison_filter_memcg);
static int hwpoison_filter_task(struct page *p)
{
	struct mem_cgroup *mem;
	struct cgroup_subsys_state *css;
	unsigned long ino;

	if (!hwpoison_filter_memcg)
		return 0;

	mem = try_get_mem_cgroup_from_page(p);
	if (!mem)
		return -EINVAL;

	css = mem_cgroup_css(mem);
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	ino = cgroup_ino(css->cgroup);
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	css_put(css);

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	if (ino != hwpoison_filter_memcg)
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		return -EINVAL;

	return 0;
}
#else
static int hwpoison_filter_task(struct page *p) { return 0; }
#endif

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int hwpoison_filter(struct page *p)
{
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	if (!hwpoison_filter_enable)
		return 0;

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	if (hwpoison_filter_dev(p))
		return -EINVAL;

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	if (hwpoison_filter_flags(p))
		return -EINVAL;

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	if (hwpoison_filter_task(p))
		return -EINVAL;

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	return 0;
}
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#else
int hwpoison_filter(struct page *p)
{
	return 0;
}
#endif

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EXPORT_SYMBOL_GPL(hwpoison_filter);

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/*
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 * Send all the processes who have the page mapped a signal.
 * ``action optional'' if they are not immediately affected by the error
 * ``action required'' if error happened in current execution context
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 */
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static int kill_proc(struct task_struct *t, unsigned long addr, int trapno,
			unsigned long pfn, struct page *page, int flags)
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{
	struct siginfo si;
	int ret;

	printk(KERN_ERR
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		"MCE %#lx: Killing %s:%d due to hardware memory corruption\n",
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		pfn, t->comm, t->pid);
	si.si_signo = SIGBUS;
	si.si_errno = 0;
	si.si_addr = (void *)addr;
#ifdef __ARCH_SI_TRAPNO
	si.si_trapno = trapno;
#endif
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	si.si_addr_lsb = compound_order(compound_head(page)) + PAGE_SHIFT;
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	if ((flags & MF_ACTION_REQUIRED) && t->mm == current->mm) {
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		si.si_code = BUS_MCEERR_AR;
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		ret = force_sig_info(SIGBUS, &si, current);
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	} else {
		/*
		 * 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 no one will do that?
		 */
		si.si_code = BUS_MCEERR_AO;
		ret = send_sig_info(SIGBUS, &si, t);  /* synchronous? */
	}
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	if (ret < 0)
		printk(KERN_INFO "MCE: Error sending signal to %s:%d: %d\n",
		       t->comm, t->pid, ret);
	return ret;
}

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/*
 * When a unknown page type is encountered drain as many buffers as possible
 * in the hope to turn the page into a LRU or free page, which we can handle.
 */
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void shake_page(struct page *p, int access)
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{
	if (!PageSlab(p)) {
		lru_add_drain_all();
		if (PageLRU(p))
			return;
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		drain_all_pages(page_zone(p));
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		if (PageLRU(p) || is_free_buddy_page(p))
			return;
	}
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	/*
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	 * Only call shrink_node_slabs here (which would also shrink
	 * other caches) if access is not potentially fatal.
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	 */
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	if (access)
		drop_slab_node(page_to_nid(p));
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}
EXPORT_SYMBOL_GPL(shake_page);

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/*
 * 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;
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	char addr_valid;
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};

/*
 * 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) {
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		pr_info("MCE: Unable to find user space address %lx in %s\n",
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			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.
 */
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static void kill_procs(struct list_head *to_kill, int forcekill, int trapno,
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			  int fail, struct page *page, unsigned long pfn,
			  int flags)
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{
	struct to_kill *tk, *next;

	list_for_each_entry_safe (tk, next, to_kill, nd) {
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		if (forcekill) {
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			/*
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			 * In case something went wrong with munmapping
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			 * make sure the process doesn't catch the
			 * signal and then access the memory. Just kill it.
			 */
			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.
			 */
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			else if (kill_proc(tk->tsk, tk->addr, trapno,
					      pfn, page, flags) < 0)
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				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);
	}
}

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/*
 * Find a dedicated thread which is supposed to handle SIGBUS(BUS_MCEERR_AO)
 * on behalf of the thread group. Return task_struct of the (first found)
 * dedicated thread if found, and return NULL otherwise.
 *
 * We already hold read_lock(&tasklist_lock) in the caller, so we don't
 * have to call rcu_read_lock/unlock() in this function.
 */
static struct task_struct *find_early_kill_thread(struct task_struct *tsk)
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{
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	struct task_struct *t;

	for_each_thread(tsk, t)
		if ((t->flags & PF_MCE_PROCESS) && (t->flags & PF_MCE_EARLY))
			return t;
	return NULL;
}

/*
 * Determine whether a given process is "early kill" process which expects
 * to be signaled when some page under the process is hwpoisoned.
 * Return task_struct of the dedicated thread (main thread unless explicitly
 * specified) if the process is "early kill," and otherwise returns NULL.
 */
static struct task_struct *task_early_kill(struct task_struct *tsk,
					   int force_early)
{
	struct task_struct *t;
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	if (!tsk->mm)
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		return NULL;
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	if (force_early)
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		return tsk;
	t = find_early_kill_thread(tsk);
	if (t)
		return t;
	if (sysctl_memory_failure_early_kill)
		return tsk;
	return NULL;
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}

/*
 * Collect processes when the error hit an anonymous page.
 */
static void collect_procs_anon(struct page *page, struct list_head *to_kill,
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			      struct to_kill **tkc, int force_early)
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{
	struct vm_area_struct *vma;
	struct task_struct *tsk;
	struct anon_vma *av;
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	pgoff_t pgoff;
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	av = page_lock_anon_vma_read(page);
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	if (av == NULL)	/* Not actually mapped anymore */
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		return;

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	pgoff = page_to_pgoff(page);
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	read_lock(&tasklist_lock);
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	for_each_process (tsk) {
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		struct anon_vma_chain *vmac;
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		struct task_struct *t = task_early_kill(tsk, force_early);
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		if (!t)
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			continue;
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		anon_vma_interval_tree_foreach(vmac, &av->rb_root,
					       pgoff, pgoff) {
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			vma = vmac->vma;
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			if (!page_mapped_in_vma(page, vma))
				continue;
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			if (vma->vm_mm == t->mm)
				add_to_kill(t, page, vma, to_kill, tkc);
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		}
	}
	read_unlock(&tasklist_lock);
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	page_unlock_anon_vma_read(av);
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}

/*
 * Collect processes when the error hit a file mapped page.
 */
static void collect_procs_file(struct page *page, struct list_head *to_kill,
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			      struct to_kill **tkc, int force_early)
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{
	struct vm_area_struct *vma;
	struct task_struct *tsk;
	struct address_space *mapping = page->mapping;

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	i_mmap_lock_read(mapping);
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	read_lock(&tasklist_lock);
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	for_each_process(tsk) {
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		pgoff_t pgoff = page_to_pgoff(page);
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		struct task_struct *t = task_early_kill(tsk, force_early);
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		if (!t)
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			continue;
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		vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff,
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				      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.
			 */
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			if (vma->vm_mm == t->mm)
				add_to_kill(t, page, vma, to_kill, tkc);
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		}
	}
	read_unlock(&tasklist_lock);
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	i_mmap_unlock_read(mapping);
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}

/*
 * 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.
 */
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static void collect_procs(struct page *page, struct list_head *tokill,
				int force_early)
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{
	struct to_kill *tk;

	if (!page->mapping)
		return;

	tk = kmalloc(sizeof(struct to_kill), GFP_NOIO);
	if (!tk)
		return;
	if (PageAnon(page))
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		collect_procs_anon(page, tokill, &tk, force_early);
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	else
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		collect_procs_file(page, tokill, &tk, force_early);
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	kfree(tk);
}

/*
 * Error handlers for various types of pages.
 */

enum outcome {
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	IGNORED,	/* Error: cannot be handled */
	FAILED,		/* Error: handling failed */
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	DELAYED,	/* Will be handled later */
	RECOVERED,	/* Successfully recovered */
};

static const char *action_name[] = {
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	[IGNORED] = "Ignored",
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	[FAILED] = "Failed",
	[DELAYED] = "Delayed",
	[RECOVERED] = "Recovered",
};

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enum action_page_type {
	MSG_KERNEL,
	MSG_KERNEL_HIGH_ORDER,
	MSG_SLAB,
	MSG_DIFFERENT_COMPOUND,
	MSG_POISONED_HUGE,
	MSG_HUGE,
	MSG_FREE_HUGE,
	MSG_UNMAP_FAILED,
	MSG_DIRTY_SWAPCACHE,
	MSG_CLEAN_SWAPCACHE,
	MSG_DIRTY_MLOCKED_LRU,
	MSG_CLEAN_MLOCKED_LRU,
	MSG_DIRTY_UNEVICTABLE_LRU,
	MSG_CLEAN_UNEVICTABLE_LRU,
	MSG_DIRTY_LRU,
	MSG_CLEAN_LRU,
	MSG_TRUNCATED_LRU,
	MSG_BUDDY,
	MSG_BUDDY_2ND,
	MSG_UNKNOWN,
};

static const char * const action_page_types[] = {
	[MSG_KERNEL]			= "reserved kernel page",
	[MSG_KERNEL_HIGH_ORDER]		= "high-order kernel page",
	[MSG_SLAB]			= "kernel slab page",
	[MSG_DIFFERENT_COMPOUND]	= "different compound page after locking",
	[MSG_POISONED_HUGE]		= "huge page already hardware poisoned",
	[MSG_HUGE]			= "huge page",
	[MSG_FREE_HUGE]			= "free huge page",
	[MSG_UNMAP_FAILED]		= "unmapping failed page",
	[MSG_DIRTY_SWAPCACHE]		= "dirty swapcache page",
	[MSG_CLEAN_SWAPCACHE]		= "clean swapcache page",
	[MSG_DIRTY_MLOCKED_LRU]		= "dirty mlocked LRU page",
	[MSG_CLEAN_MLOCKED_LRU]		= "clean mlocked LRU page",
	[MSG_DIRTY_UNEVICTABLE_LRU]	= "dirty unevictable LRU page",
	[MSG_CLEAN_UNEVICTABLE_LRU]	= "clean unevictable LRU page",
	[MSG_DIRTY_LRU]			= "dirty LRU page",
	[MSG_CLEAN_LRU]			= "clean LRU page",
	[MSG_TRUNCATED_LRU]		= "already truncated LRU page",
	[MSG_BUDDY]			= "free buddy page",
	[MSG_BUDDY_2ND]			= "free buddy page (2nd try)",
	[MSG_UNKNOWN]			= "unknown page",
};

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/*
 * XXX: It is possible that a page is isolated from LRU cache,
 * and then kept in swap cache or failed to remove from page cache.
 * The page count will stop it from being freed by unpoison.
 * Stress tests should be aware of this memory leak problem.
 */
static int delete_from_lru_cache(struct page *p)
{
	if (!isolate_lru_page(p)) {
		/*
		 * Clear sensible page flags, so that the buddy system won't
		 * complain when the page is unpoison-and-freed.
		 */
		ClearPageActive(p);
		ClearPageUnevictable(p);
		/*
		 * drop the page count elevated by isolate_lru_page()
		 */
		page_cache_release(p);
		return 0;
	}
	return -EIO;
}

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/*
 * 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 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;
}

/*
 * 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;

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	delete_from_lru_cache(p);

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	/*
	 * 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)) {
658
			pr_info("MCE %#lx: failed to release buffers\n", pfn);
659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676
		} 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;
}

/*
677
 * Dirty pagecache page
678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709
 * 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
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Lucas De Marchi 已提交
710
		 * and the page is dropped between then the error
711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752
		 * 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)
{
	ClearPageDirty(p);
	/* Trigger EIO in shmem: */
	ClearPageUptodate(p);

753 754 755 756
	if (!delete_from_lru_cache(p))
		return DELAYED;
	else
		return FAILED;
757 758 759 760 761
}

static int me_swapcache_clean(struct page *p, unsigned long pfn)
{
	delete_from_swap_cache(p);
762

763 764 765 766
	if (!delete_from_lru_cache(p))
		return RECOVERED;
	else
		return FAILED;
767 768 769 770 771
}

/*
 * Huge pages. Needs work.
 * Issues:
772 773
 * - Error on hugepage is contained in hugepage unit (not in raw page unit.)
 *   To narrow down kill region to one page, we need to break up pmd.
774 775 776
 */
static int me_huge_page(struct page *p, unsigned long pfn)
{
777
	int res = 0;
778 779 780 781 782 783 784 785 786 787 788 789
	struct page *hpage = compound_head(p);
	/*
	 * We can safely recover from error on free or reserved (i.e.
	 * not in-use) hugepage by dequeuing it from freelist.
	 * To check whether a hugepage is in-use or not, we can't use
	 * page->lru because it can be used in other hugepage operations,
	 * such as __unmap_hugepage_range() and gather_surplus_pages().
	 * So instead we use page_mapping() and PageAnon().
	 * We assume that this function is called with page lock held,
	 * so there is no race between isolation and mapping/unmapping.
	 */
	if (!(page_mapping(hpage) || PageAnon(hpage))) {
790 791 792
		res = dequeue_hwpoisoned_huge_page(hpage);
		if (!res)
			return RECOVERED;
793 794
	}
	return DELAYED;
795 796 797 798 799 800 801 802 803
}

/*
 * 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
L
Lucas De Marchi 已提交
804
 * in its live cycle, so all accesses have to be extremely careful.
805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825
 *
 * 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 reserved	(1UL << PG_reserved)

static struct page_state {
	unsigned long mask;
	unsigned long res;
826
	enum action_page_type type;
827 828
	int (*action)(struct page *p, unsigned long pfn);
} error_states[] = {
829
	{ reserved,	reserved,	MSG_KERNEL,	me_kernel },
830 831 832 833
	/*
	 * free pages are specially detected outside this table:
	 * PG_buddy pages only make a small fraction of all free pages.
	 */
834 835 836 837 838 839

	/*
	 * 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.
	 */
840
	{ slab,		slab,		MSG_SLAB,	me_kernel },
841 842

#ifdef CONFIG_PAGEFLAGS_EXTENDED
843 844
	{ head,		head,		MSG_HUGE,		me_huge_page },
	{ tail,		tail,		MSG_HUGE,		me_huge_page },
845
#else
846
	{ compound,	compound,	MSG_HUGE,		me_huge_page },
847 848
#endif

849 850
	{ sc|dirty,	sc|dirty,	MSG_DIRTY_SWAPCACHE,	me_swapcache_dirty },
	{ sc|dirty,	sc,		MSG_CLEAN_SWAPCACHE,	me_swapcache_clean },
851

852 853
	{ mlock|dirty,	mlock|dirty,	MSG_DIRTY_MLOCKED_LRU,	me_pagecache_dirty },
	{ mlock|dirty,	mlock,		MSG_CLEAN_MLOCKED_LRU,	me_pagecache_clean },
854

855 856
	{ unevict|dirty, unevict|dirty,	MSG_DIRTY_UNEVICTABLE_LRU,	me_pagecache_dirty },
	{ unevict|dirty, unevict,	MSG_CLEAN_UNEVICTABLE_LRU,	me_pagecache_clean },
857

858 859
	{ lru|dirty,	lru|dirty,	MSG_DIRTY_LRU,	me_pagecache_dirty },
	{ lru|dirty,	lru,		MSG_CLEAN_LRU,	me_pagecache_clean },
860 861 862 863

	/*
	 * Catchall entry: must be at end.
	 */
864
	{ 0,		0,		MSG_UNKNOWN,	me_unknown },
865 866
};

867 868 869 870 871 872 873 874 875 876 877 878 879
#undef dirty
#undef sc
#undef unevict
#undef mlock
#undef writeback
#undef lru
#undef swapbacked
#undef head
#undef tail
#undef compound
#undef slab
#undef reserved

880 881 882 883
/*
 * "Dirty/Clean" indication is not 100% accurate due to the possibility of
 * setting PG_dirty outside page lock. See also comment above set_page_dirty().
 */
884
static void action_result(unsigned long pfn, enum action_page_type type, int result)
885
{
886 887
	pr_err("MCE %#lx: recovery action for %s: %s\n",
		pfn, action_page_types[type], action_name[result]);
888 889 890
}

static int page_action(struct page_state *ps, struct page *p,
891
			unsigned long pfn)
892 893
{
	int result;
894
	int count;
895 896

	result = ps->action(p, pfn);
897

898
	count = page_count(p) - 1;
899 900 901
	if (ps->action == me_swapcache_dirty && result == DELAYED)
		count--;
	if (count != 0) {
902
		printk(KERN_ERR
903 904
		       "MCE %#lx: %s still referenced by %d users\n",
		       pfn, action_page_types[ps->type], count);
905 906
		result = FAILED;
	}
907
	action_result(pfn, ps->type, result);
908 909 910 911 912 913

	/* Could do more checks here if page looks ok */
	/*
	 * Could adjust zone counters here to correct for the missing page.
	 */

914
	return (result == RECOVERED || result == DELAYED) ? 0 : -EBUSY;
915 916 917 918 919 920
}

/*
 * Do all that is necessary to remove user space mappings. Unmap
 * the pages and send SIGBUS to the processes if the data was dirty.
 */
W
Wu Fengguang 已提交
921
static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
922
				  int trapno, int flags, struct page **hpagep)
923 924 925 926 927
{
	enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
	struct address_space *mapping;
	LIST_HEAD(tokill);
	int ret;
928
	int kill = 1, forcekill;
929
	struct page *hpage = *hpagep;
930
	struct page *ppage;
931

932 933 934 935 936 937 938
	/*
	 * Here we are interested only in user-mapped pages, so skip any
	 * other types of pages.
	 */
	if (PageReserved(p) || PageSlab(p))
		return SWAP_SUCCESS;
	if (!(PageLRU(hpage) || PageHuge(p)))
W
Wu Fengguang 已提交
939
		return SWAP_SUCCESS;
940 941 942 943 944

	/*
	 * This check implies we don't kill processes if their pages
	 * are in the swap cache early. Those are always late kills.
	 */
945
	if (!page_mapped(hpage))
W
Wu Fengguang 已提交
946 947
		return SWAP_SUCCESS;

948 949
	if (PageKsm(p)) {
		pr_err("MCE %#lx: can't handle KSM pages.\n", pfn);
W
Wu Fengguang 已提交
950
		return SWAP_FAIL;
951
	}
952 953 954 955 956 957 958 959 960 961

	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.
962 963
	 * XXX: the dirty test could be racy: set_page_dirty() may not always
	 * be called inside page lock (it's recommended but not enforced).
964
	 */
965
	mapping = page_mapping(hpage);
966
	if (!(flags & MF_MUST_KILL) && !PageDirty(hpage) && mapping &&
967 968 969
	    mapping_cap_writeback_dirty(mapping)) {
		if (page_mkclean(hpage)) {
			SetPageDirty(hpage);
970 971 972 973 974 975 976 977 978
		} else {
			kill = 0;
			ttu |= TTU_IGNORE_HWPOISON;
			printk(KERN_INFO
	"MCE %#lx: corrupted page was clean: dropped without side effects\n",
				pfn);
		}
	}

979 980 981 982 983 984 985 986
	/*
	 * ppage: poisoned page
	 *   if p is regular page(4k page)
	 *        ppage == real poisoned page;
	 *   else p is hugetlb or THP, ppage == head page.
	 */
	ppage = hpage;

987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011
	if (PageTransHuge(hpage)) {
		/*
		 * Verify that this isn't a hugetlbfs head page, the check for
		 * PageAnon is just for avoid tripping a split_huge_page
		 * internal debug check, as split_huge_page refuses to deal with
		 * anything that isn't an anon page. PageAnon can't go away fro
		 * under us because we hold a refcount on the hpage, without a
		 * refcount on the hpage. split_huge_page can't be safely called
		 * in the first place, having a refcount on the tail isn't
		 * enough * to be safe.
		 */
		if (!PageHuge(hpage) && PageAnon(hpage)) {
			if (unlikely(split_huge_page(hpage))) {
				/*
				 * FIXME: if splitting THP is failed, it is
				 * better to stop the following operation rather
				 * than causing panic by unmapping. System might
				 * survive if the page is freed later.
				 */
				printk(KERN_INFO
					"MCE %#lx: failed to split THP\n", pfn);

				BUG_ON(!PageHWPoison(p));
				return SWAP_FAIL;
			}
1012 1013 1014 1015
			/*
			 * We pinned the head page for hwpoison handling,
			 * now we split the thp and we are interested in
			 * the hwpoisoned raw page, so move the refcount
1016
			 * to it. Similarly, page lock is shifted.
1017 1018
			 */
			if (hpage != p) {
1019 1020 1021 1022
				if (!(flags & MF_COUNT_INCREASED)) {
					put_page(hpage);
					get_page(p);
				}
1023 1024 1025
				lock_page(p);
				unlock_page(hpage);
				*hpagep = p;
1026
			}
1027 1028
			/* THP is split, so ppage should be the real poisoned page. */
			ppage = p;
1029 1030 1031
		}
	}

1032 1033 1034 1035 1036 1037 1038 1039 1040
	/*
	 * 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)
1041
		collect_procs(ppage, &tokill, flags & MF_ACTION_REQUIRED);
1042

1043
	ret = try_to_unmap(ppage, ttu);
1044 1045
	if (ret != SWAP_SUCCESS)
		printk(KERN_ERR "MCE %#lx: failed to unmap page (mapcount=%d)\n",
1046 1047
				pfn, page_mapcount(ppage));

1048 1049 1050 1051
	/*
	 * 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
1052 1053
	 * was dirty or the process is not restartable,
	 * otherwise the tokill list is merely
1054 1055 1056 1057
	 * freed.  When there was a problem unmapping earlier
	 * use a more force-full uncatchable kill to prevent
	 * any accesses to the poisoned memory.
	 */
1058 1059
	forcekill = PageDirty(ppage) || (flags & MF_MUST_KILL);
	kill_procs(&tokill, forcekill, trapno,
1060
		      ret != SWAP_SUCCESS, p, pfn, flags);
W
Wu Fengguang 已提交
1061 1062

	return ret;
1063 1064
}

1065 1066 1067
static void set_page_hwpoison_huge_page(struct page *hpage)
{
	int i;
1068
	int nr_pages = 1 << compound_order(hpage);
1069 1070 1071 1072 1073 1074 1075
	for (i = 0; i < nr_pages; i++)
		SetPageHWPoison(hpage + i);
}

static void clear_page_hwpoison_huge_page(struct page *hpage)
{
	int i;
1076
	int nr_pages = 1 << compound_order(hpage);
1077 1078 1079 1080
	for (i = 0; i < nr_pages; i++)
		ClearPageHWPoison(hpage + i);
}

1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099
/**
 * 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.
 * @flags: fine tune action taken
 *
 * 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.
 */
int memory_failure(unsigned long pfn, int trapno, int flags)
1100 1101 1102
{
	struct page_state *ps;
	struct page *p;
1103
	struct page *hpage;
1104
	int res;
1105
	unsigned int nr_pages;
1106
	unsigned long page_flags;
1107 1108 1109 1110 1111

	if (!sysctl_memory_failure_recovery)
		panic("Memory failure from trap %d on page %lx", trapno, pfn);

	if (!pfn_valid(pfn)) {
1112 1113 1114 1115
		printk(KERN_ERR
		       "MCE %#lx: memory outside kernel control\n",
		       pfn);
		return -ENXIO;
1116 1117 1118
	}

	p = pfn_to_page(pfn);
1119
	hpage = compound_head(p);
1120
	if (TestSetPageHWPoison(p)) {
1121
		printk(KERN_ERR "MCE %#lx: already hardware poisoned\n", pfn);
1122 1123 1124
		return 0;
	}

1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135
	/*
	 * Currently errors on hugetlbfs pages are measured in hugepage units,
	 * so nr_pages should be 1 << compound_order.  OTOH when errors are on
	 * transparent hugepages, they are supposed to be split and error
	 * measurement is done in normal page units.  So nr_pages should be one
	 * in this case.
	 */
	if (PageHuge(p))
		nr_pages = 1 << compound_order(hpage);
	else /* normal page or thp */
		nr_pages = 1;
1136
	atomic_long_add(nr_pages, &num_poisoned_pages);
1137 1138 1139 1140 1141

	/*
	 * 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.
1142 1143 1144 1145
	 * 2) it's a free hugepage, which is also safe:
	 *    an affected hugepage will be dequeued from hugepage freelist,
	 *    so there's no concern about reusing it ever after.
	 * 3) it's part of a non-compound high order page.
1146 1147 1148 1149 1150 1151
	 *    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.
	 */
1152
	if (!(flags & MF_COUNT_INCREASED) &&
1153
		!get_page_unless_zero(hpage)) {
1154
		if (is_free_buddy_page(p)) {
1155
			action_result(pfn, MSG_BUDDY, DELAYED);
1156
			return 0;
1157 1158
		} else if (PageHuge(hpage)) {
			/*
1159
			 * Check "filter hit" and "race with other subpage."
1160
			 */
J
Jens Axboe 已提交
1161
			lock_page(hpage);
1162 1163 1164 1165 1166 1167 1168
			if (PageHWPoison(hpage)) {
				if ((hwpoison_filter(p) && TestClearPageHWPoison(p))
				    || (p != hpage && TestSetPageHWPoison(hpage))) {
					atomic_long_sub(nr_pages, &num_poisoned_pages);
					unlock_page(hpage);
					return 0;
				}
1169 1170 1171
			}
			set_page_hwpoison_huge_page(hpage);
			res = dequeue_hwpoisoned_huge_page(hpage);
1172
			action_result(pfn, MSG_FREE_HUGE,
1173 1174 1175
				      res ? IGNORED : DELAYED);
			unlock_page(hpage);
			return res;
1176
		} else {
1177
			action_result(pfn, MSG_KERNEL_HIGH_ORDER, IGNORED);
1178 1179
			return -EBUSY;
		}
1180 1181
	}

1182 1183 1184 1185 1186 1187 1188 1189
	/*
	 * We ignore non-LRU pages for good reasons.
	 * - PG_locked is only well defined for LRU pages and a few others
	 * - to avoid races with __set_page_locked()
	 * - to avoid races with __SetPageSlab*() (and more non-atomic ops)
	 * The check (unnecessarily) ignores LRU pages being isolated and
	 * walked by the page reclaim code, however that's not a big loss.
	 */
1190 1191 1192 1193
	if (!PageHuge(p)) {
		if (!PageLRU(hpage))
			shake_page(hpage, 0);
		if (!PageLRU(hpage)) {
1194 1195 1196 1197
			/*
			 * shake_page could have turned it free.
			 */
			if (is_free_buddy_page(p)) {
1198
				if (flags & MF_COUNT_INCREASED)
1199
					action_result(pfn, MSG_BUDDY, DELAYED);
1200
				else
1201 1202
					action_result(pfn, MSG_BUDDY_2ND,
						      DELAYED);
1203 1204
				return 0;
			}
1205
		}
1206 1207
	}

J
Jens Axboe 已提交
1208
	lock_page(hpage);
W
Wu Fengguang 已提交
1209

1210 1211 1212 1213 1214
	/*
	 * The page could have changed compound pages during the locking.
	 * If this happens just bail out.
	 */
	if (compound_head(p) != hpage) {
1215
		action_result(pfn, MSG_DIFFERENT_COMPOUND, IGNORED);
1216 1217 1218 1219
		res = -EBUSY;
		goto out;
	}

1220 1221 1222 1223 1224 1225 1226 1227 1228
	/*
	 * We use page flags to determine what action should be taken, but
	 * the flags can be modified by the error containment action.  One
	 * example is an mlocked page, where PG_mlocked is cleared by
	 * page_remove_rmap() in try_to_unmap_one(). So to determine page status
	 * correctly, we save a copy of the page flags at this time.
	 */
	page_flags = p->flags;

W
Wu Fengguang 已提交
1229 1230 1231 1232
	/*
	 * unpoison always clear PG_hwpoison inside page lock
	 */
	if (!PageHWPoison(p)) {
1233
		printk(KERN_ERR "MCE %#lx: just unpoisoned\n", pfn);
1234 1235
		atomic_long_sub(nr_pages, &num_poisoned_pages);
		put_page(hpage);
W
Wu Fengguang 已提交
1236 1237 1238
		res = 0;
		goto out;
	}
W
Wu Fengguang 已提交
1239 1240
	if (hwpoison_filter(p)) {
		if (TestClearPageHWPoison(p))
1241
			atomic_long_sub(nr_pages, &num_poisoned_pages);
1242 1243
		unlock_page(hpage);
		put_page(hpage);
W
Wu Fengguang 已提交
1244 1245
		return 0;
	}
W
Wu Fengguang 已提交
1246

1247 1248 1249
	if (!PageHuge(p) && !PageTransTail(p) && !PageLRU(p))
		goto identify_page_state;

1250 1251 1252 1253
	/*
	 * For error on the tail page, we should set PG_hwpoison
	 * on the head page to show that the hugepage is hwpoisoned
	 */
1254
	if (PageHuge(p) && PageTail(p) && TestSetPageHWPoison(hpage)) {
1255
		action_result(pfn, MSG_POISONED_HUGE, IGNORED);
1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268
		unlock_page(hpage);
		put_page(hpage);
		return 0;
	}
	/*
	 * Set PG_hwpoison on all pages in an error hugepage,
	 * because containment is done in hugepage unit for now.
	 * Since we have done TestSetPageHWPoison() for the head page with
	 * page lock held, we can safely set PG_hwpoison bits on tail pages.
	 */
	if (PageHuge(p))
		set_page_hwpoison_huge_page(hpage);

1269 1270 1271 1272
	/*
	 * It's very difficult to mess with pages currently under IO
	 * and in many cases impossible, so we just avoid it here.
	 */
1273 1274 1275 1276
	wait_on_page_writeback(p);

	/*
	 * Now take care of user space mappings.
1277
	 * Abort on fail: __delete_from_page_cache() assumes unmapped page.
1278 1279 1280
	 *
	 * When the raw error page is thp tail page, hpage points to the raw
	 * page after thp split.
1281
	 */
1282 1283
	if (hwpoison_user_mappings(p, pfn, trapno, flags, &hpage)
	    != SWAP_SUCCESS) {
1284
		action_result(pfn, MSG_UNMAP_FAILED, IGNORED);
W
Wu Fengguang 已提交
1285 1286 1287
		res = -EBUSY;
		goto out;
	}
1288 1289 1290 1291

	/*
	 * Torn down by someone else?
	 */
1292
	if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) {
1293
		action_result(pfn, MSG_TRUNCATED_LRU, IGNORED);
1294
		res = -EBUSY;
1295 1296 1297
		goto out;
	}

1298
identify_page_state:
1299
	res = -EBUSY;
1300 1301 1302 1303 1304 1305 1306
	/*
	 * The first check uses the current page flags which may not have any
	 * relevant information. The second check with the saved page flagss is
	 * carried out only if the first check can't determine the page status.
	 */
	for (ps = error_states;; ps++)
		if ((p->flags & ps->mask) == ps->res)
1307
			break;
1308 1309 1310

	page_flags |= (p->flags & (1UL << PG_dirty));

1311 1312 1313 1314 1315
	if (!ps->mask)
		for (ps = error_states;; ps++)
			if ((page_flags & ps->mask) == ps->res)
				break;
	res = page_action(ps, p, pfn);
1316
out:
1317
	unlock_page(hpage);
1318 1319
	return res;
}
1320
EXPORT_SYMBOL_GPL(memory_failure);
W
Wu Fengguang 已提交
1321

1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368
#define MEMORY_FAILURE_FIFO_ORDER	4
#define MEMORY_FAILURE_FIFO_SIZE	(1 << MEMORY_FAILURE_FIFO_ORDER)

struct memory_failure_entry {
	unsigned long pfn;
	int trapno;
	int flags;
};

struct memory_failure_cpu {
	DECLARE_KFIFO(fifo, struct memory_failure_entry,
		      MEMORY_FAILURE_FIFO_SIZE);
	spinlock_t lock;
	struct work_struct work;
};

static DEFINE_PER_CPU(struct memory_failure_cpu, memory_failure_cpu);

/**
 * memory_failure_queue - Schedule handling memory failure of a page.
 * @pfn: Page Number of the corrupted page
 * @trapno: Trap number reported in the signal to user space.
 * @flags: Flags for memory failure handling
 *
 * This function is called by the low level hardware error handler
 * when it detects hardware memory corruption of a page. It schedules
 * the recovering of error page, including 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)
 *
 * Can run in IRQ context.
 */
void memory_failure_queue(unsigned long pfn, int trapno, int flags)
{
	struct memory_failure_cpu *mf_cpu;
	unsigned long proc_flags;
	struct memory_failure_entry entry = {
		.pfn =		pfn,
		.trapno =	trapno,
		.flags =	flags,
	};

	mf_cpu = &get_cpu_var(memory_failure_cpu);
	spin_lock_irqsave(&mf_cpu->lock, proc_flags);
S
Stefani Seibold 已提交
1369
	if (kfifo_put(&mf_cpu->fifo, entry))
1370 1371
		schedule_work_on(smp_processor_id(), &mf_cpu->work);
	else
J
Joe Perches 已提交
1372
		pr_err("Memory failure: buffer overflow when queuing memory failure at %#lx\n",
1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385
		       pfn);
	spin_unlock_irqrestore(&mf_cpu->lock, proc_flags);
	put_cpu_var(memory_failure_cpu);
}
EXPORT_SYMBOL_GPL(memory_failure_queue);

static void memory_failure_work_func(struct work_struct *work)
{
	struct memory_failure_cpu *mf_cpu;
	struct memory_failure_entry entry = { 0, };
	unsigned long proc_flags;
	int gotten;

1386
	mf_cpu = this_cpu_ptr(&memory_failure_cpu);
1387 1388 1389 1390 1391 1392
	for (;;) {
		spin_lock_irqsave(&mf_cpu->lock, proc_flags);
		gotten = kfifo_get(&mf_cpu->fifo, &entry);
		spin_unlock_irqrestore(&mf_cpu->lock, proc_flags);
		if (!gotten)
			break;
1393 1394 1395 1396
		if (entry.flags & MF_SOFT_OFFLINE)
			soft_offline_page(pfn_to_page(entry.pfn), entry.flags);
		else
			memory_failure(entry.pfn, entry.trapno, entry.flags);
1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415
	}
}

static int __init memory_failure_init(void)
{
	struct memory_failure_cpu *mf_cpu;
	int cpu;

	for_each_possible_cpu(cpu) {
		mf_cpu = &per_cpu(memory_failure_cpu, cpu);
		spin_lock_init(&mf_cpu->lock);
		INIT_KFIFO(mf_cpu->fifo);
		INIT_WORK(&mf_cpu->work, memory_failure_work_func);
	}

	return 0;
}
core_initcall(memory_failure_init);

W
Wu Fengguang 已提交
1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432
/**
 * unpoison_memory - Unpoison a previously poisoned page
 * @pfn: Page number of the to be unpoisoned page
 *
 * Software-unpoison a page that has been poisoned by
 * memory_failure() earlier.
 *
 * This is only done on the software-level, so it only works
 * for linux injected failures, not real hardware failures
 *
 * Returns 0 for success, otherwise -errno.
 */
int unpoison_memory(unsigned long pfn)
{
	struct page *page;
	struct page *p;
	int freeit = 0;
1433
	unsigned int nr_pages;
W
Wu Fengguang 已提交
1434 1435 1436 1437 1438 1439 1440 1441

	if (!pfn_valid(pfn))
		return -ENXIO;

	p = pfn_to_page(pfn);
	page = compound_head(p);

	if (!PageHWPoison(p)) {
1442
		pr_info("MCE: Page was already unpoisoned %#lx\n", pfn);
W
Wu Fengguang 已提交
1443 1444 1445
		return 0;
	}

1446 1447 1448 1449 1450
	/*
	 * unpoison_memory() can encounter thp only when the thp is being
	 * worked by memory_failure() and the page lock is not held yet.
	 * In such case, we yield to memory_failure() and make unpoison fail.
	 */
1451
	if (!PageHuge(page) && PageTransHuge(page)) {
1452 1453 1454 1455
		pr_info("MCE: Memory failure is now running on %#lx\n", pfn);
			return 0;
	}

1456
	nr_pages = 1 << compound_order(page);
1457

W
Wu Fengguang 已提交
1458
	if (!get_page_unless_zero(page)) {
1459 1460 1461 1462 1463 1464 1465
		/*
		 * Since HWPoisoned hugepage should have non-zero refcount,
		 * race between memory failure and unpoison seems to happen.
		 * In such case unpoison fails and memory failure runs
		 * to the end.
		 */
		if (PageHuge(page)) {
1466
			pr_info("MCE: Memory failure is now running on free hugepage %#lx\n", pfn);
1467 1468
			return 0;
		}
W
Wu Fengguang 已提交
1469
		if (TestClearPageHWPoison(p))
1470
			atomic_long_dec(&num_poisoned_pages);
1471
		pr_info("MCE: Software-unpoisoned free page %#lx\n", pfn);
W
Wu Fengguang 已提交
1472 1473 1474
		return 0;
	}

J
Jens Axboe 已提交
1475
	lock_page(page);
W
Wu Fengguang 已提交
1476 1477 1478 1479 1480 1481
	/*
	 * This test is racy because PG_hwpoison is set outside of page lock.
	 * That's acceptable because that won't trigger kernel panic. Instead,
	 * the PG_hwpoison page will be caught and isolated on the entrance to
	 * the free buddy page pool.
	 */
1482
	if (TestClearPageHWPoison(page)) {
1483
		pr_info("MCE: Software-unpoisoned page %#lx\n", pfn);
1484
		atomic_long_sub(nr_pages, &num_poisoned_pages);
W
Wu Fengguang 已提交
1485
		freeit = 1;
1486 1487
		if (PageHuge(page))
			clear_page_hwpoison_huge_page(page);
W
Wu Fengguang 已提交
1488 1489 1490 1491
	}
	unlock_page(page);

	put_page(page);
1492
	if (freeit && !(pfn == my_zero_pfn(0) && page_count(p) == 1))
W
Wu Fengguang 已提交
1493 1494 1495 1496 1497
		put_page(page);

	return 0;
}
EXPORT_SYMBOL(unpoison_memory);
1498 1499 1500

static struct page *new_page(struct page *p, unsigned long private, int **x)
{
1501
	int nid = page_to_nid(p);
1502 1503 1504 1505 1506
	if (PageHuge(p))
		return alloc_huge_page_node(page_hstate(compound_head(p)),
						   nid);
	else
		return alloc_pages_exact_node(nid, GFP_HIGHUSER_MOVABLE, 0);
1507 1508 1509 1510 1511 1512 1513 1514
}

/*
 * Safely get reference count of an arbitrary page.
 * Returns 0 for a free page, -EIO for a zero refcount page
 * that is not free, and 1 for any other page type.
 * For 1 the page is returned with increased page count, otherwise not.
 */
1515
static int __get_any_page(struct page *p, unsigned long pfn, int flags)
1516 1517 1518 1519 1520 1521
{
	int ret;

	if (flags & MF_COUNT_INCREASED)
		return 1;

1522 1523 1524 1525
	/*
	 * When the target page is a free hugepage, just remove it
	 * from free hugepage list.
	 */
1526
	if (!get_page_unless_zero(compound_head(p))) {
1527
		if (PageHuge(p)) {
1528
			pr_info("%s: %#lx free huge page\n", __func__, pfn);
1529
			ret = 0;
1530
		} else if (is_free_buddy_page(p)) {
1531
			pr_info("%s: %#lx free buddy page\n", __func__, pfn);
1532 1533
			ret = 0;
		} else {
1534 1535
			pr_info("%s: %#lx: unknown zero refcount page type %lx\n",
				__func__, pfn, p->flags);
1536 1537 1538 1539 1540 1541 1542 1543 1544
			ret = -EIO;
		}
	} else {
		/* Not a free page */
		ret = 1;
	}
	return ret;
}

1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568
static int get_any_page(struct page *page, unsigned long pfn, int flags)
{
	int ret = __get_any_page(page, pfn, flags);

	if (ret == 1 && !PageHuge(page) && !PageLRU(page)) {
		/*
		 * Try to free it.
		 */
		put_page(page);
		shake_page(page, 1);

		/*
		 * Did it turn free?
		 */
		ret = __get_any_page(page, pfn, 0);
		if (!PageLRU(page)) {
			pr_info("soft_offline: %#lx: unknown non LRU page type %lx\n",
				pfn, page->flags);
			return -EIO;
		}
	}
	return ret;
}

1569 1570 1571 1572 1573
static int soft_offline_huge_page(struct page *page, int flags)
{
	int ret;
	unsigned long pfn = page_to_pfn(page);
	struct page *hpage = compound_head(page);
1574
	LIST_HEAD(pagelist);
1575

1576 1577 1578 1579 1580
	/*
	 * This double-check of PageHWPoison is to avoid the race with
	 * memory_failure(). See also comment in __soft_offline_page().
	 */
	lock_page(hpage);
1581
	if (PageHWPoison(hpage)) {
1582 1583
		unlock_page(hpage);
		put_page(hpage);
1584
		pr_info("soft offline: %#lx hugepage already poisoned\n", pfn);
1585
		return -EBUSY;
1586
	}
1587
	unlock_page(hpage);
1588

1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600
	ret = isolate_huge_page(hpage, &pagelist);
	if (ret) {
		/*
		 * get_any_page() and isolate_huge_page() takes a refcount each,
		 * so need to drop one here.
		 */
		put_page(hpage);
	} else {
		pr_info("soft offline: %#lx hugepage failed to isolate\n", pfn);
		return -EBUSY;
	}

1601
	ret = migrate_pages(&pagelist, new_page, NULL, MPOL_MF_MOVE_ALL,
1602
				MIGRATE_SYNC, MR_MEMORY_FAILURE);
1603
	if (ret) {
1604 1605
		pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
			pfn, ret, page->flags);
1606 1607 1608 1609 1610 1611 1612 1613
		/*
		 * We know that soft_offline_huge_page() tries to migrate
		 * only one hugepage pointed to by hpage, so we need not
		 * run through the pagelist here.
		 */
		putback_active_hugepage(hpage);
		if (ret > 0)
			ret = -EIO;
1614
	} else {
1615 1616 1617 1618 1619 1620 1621 1622 1623 1624
		/* overcommit hugetlb page will be freed to buddy */
		if (PageHuge(page)) {
			set_page_hwpoison_huge_page(hpage);
			dequeue_hwpoisoned_huge_page(hpage);
			atomic_long_add(1 << compound_order(hpage),
					&num_poisoned_pages);
		} else {
			SetPageHWPoison(page);
			atomic_long_inc(&num_poisoned_pages);
		}
1625 1626 1627 1628
	}
	return ret;
}

1629 1630 1631 1632
static int __soft_offline_page(struct page *page, int flags)
{
	int ret;
	unsigned long pfn = page_to_pfn(page);
1633 1634

	/*
1635 1636 1637 1638
	 * Check PageHWPoison again inside page lock because PageHWPoison
	 * is set by memory_failure() outside page lock. Note that
	 * memory_failure() also double-checks PageHWPoison inside page lock,
	 * so there's no race between soft_offline_page() and memory_failure().
1639
	 */
1640 1641
	lock_page(page);
	wait_on_page_writeback(page);
1642 1643 1644 1645 1646 1647
	if (PageHWPoison(page)) {
		unlock_page(page);
		put_page(page);
		pr_info("soft offline: %#lx page already poisoned\n", pfn);
		return -EBUSY;
	}
1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658
	/*
	 * Try to invalidate first. This should work for
	 * non dirty unmapped page cache pages.
	 */
	ret = invalidate_inode_page(page);
	unlock_page(page);
	/*
	 * RED-PEN would be better to keep it isolated here, but we
	 * would need to fix isolation locking first.
	 */
	if (ret == 1) {
1659
		put_page(page);
1660
		pr_info("soft_offline: %#lx: invalidated\n", pfn);
1661 1662 1663
		SetPageHWPoison(page);
		atomic_long_inc(&num_poisoned_pages);
		return 0;
1664 1665 1666 1667 1668 1669 1670 1671
	}

	/*
	 * Simple invalidation didn't work.
	 * Try to migrate to a new page instead. migrate.c
	 * handles a large number of cases for us.
	 */
	ret = isolate_lru_page(page);
1672 1673 1674 1675 1676
	/*
	 * Drop page reference which is came from get_any_page()
	 * successful isolate_lru_page() already took another one.
	 */
	put_page(page);
1677 1678
	if (!ret) {
		LIST_HEAD(pagelist);
1679
		inc_zone_page_state(page, NR_ISOLATED_ANON +
1680
					page_is_file_cache(page));
1681
		list_add(&page->lru, &pagelist);
1682
		ret = migrate_pages(&pagelist, new_page, NULL, MPOL_MF_MOVE_ALL,
1683
					MIGRATE_SYNC, MR_MEMORY_FAILURE);
1684
		if (ret) {
1685 1686 1687 1688 1689 1690 1691
			if (!list_empty(&pagelist)) {
				list_del(&page->lru);
				dec_zone_page_state(page, NR_ISOLATED_ANON +
						page_is_file_cache(page));
				putback_lru_page(page);
			}

1692
			pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
1693 1694 1695
				pfn, ret, page->flags);
			if (ret > 0)
				ret = -EIO;
1696
		} else {
1697 1698 1699 1700 1701 1702 1703 1704 1705
			/*
			 * After page migration succeeds, the source page can
			 * be trapped in pagevec and actual freeing is delayed.
			 * Freeing code works differently based on PG_hwpoison,
			 * so there's a race. We need to make sure that the
			 * source page should be freed back to buddy before
			 * setting PG_hwpoison.
			 */
			if (!is_free_buddy_page(page))
1706
				drain_all_pages(page_zone(page));
1707
			SetPageHWPoison(page);
1708 1709 1710
			if (!is_free_buddy_page(page))
				pr_info("soft offline: %#lx: page leaked\n",
					pfn);
1711
			atomic_long_inc(&num_poisoned_pages);
1712 1713
		}
	} else {
1714
		pr_info("soft offline: %#lx: isolation failed: %d, page count %d, type %lx\n",
1715
			pfn, ret, page_count(page), page->flags);
1716 1717 1718
	}
	return ret;
}
1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745

/**
 * soft_offline_page - Soft offline a page.
 * @page: page to offline
 * @flags: flags. Same as memory_failure().
 *
 * Returns 0 on success, otherwise negated errno.
 *
 * Soft offline a page, by migration or invalidation,
 * without killing anything. This is for the case when
 * a page is not corrupted yet (so it's still valid to access),
 * but has had a number of corrected errors and is better taken
 * out.
 *
 * The actual policy on when to do that is maintained by
 * user space.
 *
 * This should never impact any application or cause data loss,
 * however it might take some time.
 *
 * This is not a 100% solution for all memory, but tries to be
 * ``good enough'' for the majority of memory.
 */
int soft_offline_page(struct page *page, int flags)
{
	int ret;
	unsigned long pfn = page_to_pfn(page);
D
David Rientjes 已提交
1746
	struct page *hpage = compound_head(page);
1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759

	if (PageHWPoison(page)) {
		pr_info("soft offline: %#lx page already poisoned\n", pfn);
		return -EBUSY;
	}
	if (!PageHuge(page) && PageTransHuge(hpage)) {
		if (PageAnon(hpage) && unlikely(split_huge_page(hpage))) {
			pr_info("soft offline: %#lx: failed to split THP\n",
				pfn);
			return -EBUSY;
		}
	}

1760
	get_online_mems();
1761 1762 1763 1764 1765 1766 1767 1768 1769

	/*
	 * Isolate the page, so that it doesn't get reallocated if it
	 * was free. This flag should be kept set until the source page
	 * is freed and PG_hwpoison on it is set.
	 */
	if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
		set_migratetype_isolate(page, true);

1770
	ret = get_any_page(page, pfn, flags);
1771
	put_online_mems();
1772
	if (ret > 0) { /* for in-use pages */
1773 1774 1775 1776
		if (PageHuge(page))
			ret = soft_offline_huge_page(page, flags);
		else
			ret = __soft_offline_page(page, flags);
1777
	} else if (ret == 0) { /* for free pages */
1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790
		if (PageHuge(page)) {
			set_page_hwpoison_huge_page(hpage);
			dequeue_hwpoisoned_huge_page(hpage);
			atomic_long_add(1 << compound_order(hpage),
					&num_poisoned_pages);
		} else {
			SetPageHWPoison(page);
			atomic_long_inc(&num_poisoned_pages);
		}
	}
	unset_migratetype_isolate(page, MIGRATE_MOVABLE);
	return ret;
}