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-rw-r--r--kernel/mm/memory-failure.c1790
1 files changed, 1790 insertions, 0 deletions
diff --git a/kernel/mm/memory-failure.c b/kernel/mm/memory-failure.c
new file mode 100644
index 000000000..501820c81
--- /dev/null
+++ b/kernel/mm/memory-failure.c
@@ -0,0 +1,1790 @@
+/*
+ * Copyright (C) 2008, 2009 Intel Corporation
+ * Authors: Andi Kleen, Fengguang Wu
+ *
+ * This software may be redistributed and/or modified under the terms of
+ * the GNU General Public License ("GPL") version 2 only as published by the
+ * Free Software Foundation.
+ *
+ * High level machine check handler. Handles pages reported by the
+ * hardware as being corrupted usually due to a multi-bit ECC memory or cache
+ * failure.
+ *
+ * In addition there is a "soft offline" entry point that allows stop using
+ * not-yet-corrupted-by-suspicious pages without killing anything.
+ *
+ * Handles page cache pages in various states. The tricky part
+ * 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.
+ */
+
+/*
+ * 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>
+#include <linux/kernel-page-flags.h>
+#include <linux/sched.h>
+#include <linux/ksm.h>
+#include <linux/rmap.h>
+#include <linux/export.h>
+#include <linux/pagemap.h>
+#include <linux/swap.h>
+#include <linux/backing-dev.h>
+#include <linux/migrate.h>
+#include <linux/page-isolation.h>
+#include <linux/suspend.h>
+#include <linux/slab.h>
+#include <linux/swapops.h>
+#include <linux/hugetlb.h>
+#include <linux/memory_hotplug.h>
+#include <linux/mm_inline.h>
+#include <linux/kfifo.h>
+#include "internal.h"
+
+int sysctl_memory_failure_early_kill __read_mostly = 0;
+
+int sysctl_memory_failure_recovery __read_mostly = 1;
+
+atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0);
+
+#if defined(CONFIG_HWPOISON_INJECT) || defined(CONFIG_HWPOISON_INJECT_MODULE)
+
+u32 hwpoison_filter_enable = 0;
+u32 hwpoison_filter_dev_major = ~0U;
+u32 hwpoison_filter_dev_minor = ~0U;
+u64 hwpoison_filter_flags_mask;
+u64 hwpoison_filter_flags_value;
+EXPORT_SYMBOL_GPL(hwpoison_filter_enable);
+EXPORT_SYMBOL_GPL(hwpoison_filter_dev_major);
+EXPORT_SYMBOL_GPL(hwpoison_filter_dev_minor);
+EXPORT_SYMBOL_GPL(hwpoison_filter_flags_mask);
+EXPORT_SYMBOL_GPL(hwpoison_filter_flags_value);
+
+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;
+
+ /*
+ * page_mapping() does not accept slab pages.
+ */
+ 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;
+}
+
+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;
+}
+
+/*
+ * 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.
+ */
+#ifdef CONFIG_MEMCG_SWAP
+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);
+ ino = cgroup_ino(css->cgroup);
+ css_put(css);
+
+ if (ino != hwpoison_filter_memcg)
+ return -EINVAL;
+
+ return 0;
+}
+#else
+static int hwpoison_filter_task(struct page *p) { return 0; }
+#endif
+
+int hwpoison_filter(struct page *p)
+{
+ if (!hwpoison_filter_enable)
+ return 0;
+
+ if (hwpoison_filter_dev(p))
+ return -EINVAL;
+
+ if (hwpoison_filter_flags(p))
+ return -EINVAL;
+
+ if (hwpoison_filter_task(p))
+ return -EINVAL;
+
+ return 0;
+}
+#else
+int hwpoison_filter(struct page *p)
+{
+ return 0;
+}
+#endif
+
+EXPORT_SYMBOL_GPL(hwpoison_filter);
+
+/*
+ * 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
+ */
+static int kill_proc(struct task_struct *t, unsigned long addr, int trapno,
+ unsigned long pfn, struct page *page, int flags)
+{
+ struct siginfo si;
+ int ret;
+
+ printk(KERN_ERR
+ "MCE %#lx: Killing %s:%d due to hardware memory corruption\n",
+ 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
+ si.si_addr_lsb = compound_order(compound_head(page)) + PAGE_SHIFT;
+
+ if ((flags & MF_ACTION_REQUIRED) && t->mm == current->mm) {
+ si.si_code = BUS_MCEERR_AR;
+ ret = force_sig_info(SIGBUS, &si, current);
+ } 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? */
+ }
+ if (ret < 0)
+ printk(KERN_INFO "MCE: Error sending signal to %s:%d: %d\n",
+ t->comm, t->pid, ret);
+ return ret;
+}
+
+/*
+ * 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.
+ */
+void shake_page(struct page *p, int access)
+{
+ if (!PageSlab(p)) {
+ lru_add_drain_all();
+ if (PageLRU(p))
+ return;
+ drain_all_pages(page_zone(p));
+ if (PageLRU(p) || is_free_buddy_page(p))
+ return;
+ }
+
+ /*
+ * Only call shrink_node_slabs here (which would also shrink
+ * other caches) if access is not potentially fatal.
+ */
+ if (access)
+ drop_slab_node(page_to_nid(p));
+}
+EXPORT_SYMBOL_GPL(shake_page);
+
+/*
+ * 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;
+ char addr_valid;
+};
+
+/*
+ * Failure handling: if we can't find or can't kill a process there's
+ * not much we can do. We just print a message and ignore otherwise.
+ */
+
+/*
+ * Schedule a process for later kill.
+ * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
+ * TBD would GFP_NOIO be enough?
+ */
+static void add_to_kill(struct task_struct *tsk, struct page *p,
+ struct vm_area_struct *vma,
+ struct list_head *to_kill,
+ struct to_kill **tkc)
+{
+ struct to_kill *tk;
+
+ if (*tkc) {
+ tk = *tkc;
+ *tkc = NULL;
+ } else {
+ tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
+ if (!tk) {
+ printk(KERN_ERR
+ "MCE: Out of memory while machine check handling\n");
+ return;
+ }
+ }
+ tk->addr = page_address_in_vma(p, vma);
+ tk->addr_valid = 1;
+
+ /*
+ * In theory we don't have to kill when the page was
+ * munmaped. But it could be also a mremap. Since that's
+ * likely very rare kill anyways just out of paranoia, but use
+ * a SIGKILL because the error is not contained anymore.
+ */
+ if (tk->addr == -EFAULT) {
+ pr_info("MCE: Unable to find user space address %lx in %s\n",
+ page_to_pfn(p), tsk->comm);
+ tk->addr_valid = 0;
+ }
+ get_task_struct(tsk);
+ tk->tsk = tsk;
+ list_add_tail(&tk->nd, to_kill);
+}
+
+/*
+ * Kill the processes that have been collected earlier.
+ *
+ * Only do anything when DOIT is set, otherwise just free the list
+ * (this is used for clean pages which do not need killing)
+ * Also when FAIL is set do a force kill because something went
+ * wrong earlier.
+ */
+static void kill_procs(struct list_head *to_kill, int forcekill, int trapno,
+ int fail, struct page *page, unsigned long pfn,
+ int flags)
+{
+ struct to_kill *tk, *next;
+
+ list_for_each_entry_safe (tk, next, to_kill, nd) {
+ if (forcekill) {
+ /*
+ * In case something went wrong with munmapping
+ * 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.
+ */
+ else if (kill_proc(tk->tsk, tk->addr, trapno,
+ pfn, page, flags) < 0)
+ printk(KERN_ERR
+ "MCE %#lx: Cannot send advisory machine check signal to %s:%d\n",
+ pfn, tk->tsk->comm, tk->tsk->pid);
+ }
+ put_task_struct(tk->tsk);
+ kfree(tk);
+ }
+}
+
+/*
+ * 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)
+{
+ 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;
+ if (!tsk->mm)
+ return NULL;
+ if (force_early)
+ return tsk;
+ t = find_early_kill_thread(tsk);
+ if (t)
+ return t;
+ if (sysctl_memory_failure_early_kill)
+ return tsk;
+ return NULL;
+}
+
+/*
+ * Collect processes when the error hit an anonymous page.
+ */
+static void collect_procs_anon(struct page *page, struct list_head *to_kill,
+ struct to_kill **tkc, int force_early)
+{
+ struct vm_area_struct *vma;
+ struct task_struct *tsk;
+ struct anon_vma *av;
+ pgoff_t pgoff;
+
+ av = page_lock_anon_vma_read(page);
+ if (av == NULL) /* Not actually mapped anymore */
+ return;
+
+ pgoff = page_to_pgoff(page);
+ read_lock(&tasklist_lock);
+ for_each_process (tsk) {
+ struct anon_vma_chain *vmac;
+ struct task_struct *t = task_early_kill(tsk, force_early);
+
+ if (!t)
+ continue;
+ anon_vma_interval_tree_foreach(vmac, &av->rb_root,
+ pgoff, pgoff) {
+ vma = vmac->vma;
+ if (!page_mapped_in_vma(page, vma))
+ continue;
+ if (vma->vm_mm == t->mm)
+ add_to_kill(t, page, vma, to_kill, tkc);
+ }
+ }
+ read_unlock(&tasklist_lock);
+ page_unlock_anon_vma_read(av);
+}
+
+/*
+ * Collect processes when the error hit a file mapped page.
+ */
+static void collect_procs_file(struct page *page, struct list_head *to_kill,
+ struct to_kill **tkc, int force_early)
+{
+ struct vm_area_struct *vma;
+ struct task_struct *tsk;
+ struct address_space *mapping = page->mapping;
+
+ i_mmap_lock_read(mapping);
+ read_lock(&tasklist_lock);
+ for_each_process(tsk) {
+ pgoff_t pgoff = page_to_pgoff(page);
+ struct task_struct *t = task_early_kill(tsk, force_early);
+
+ if (!t)
+ continue;
+ vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff,
+ pgoff) {
+ /*
+ * Send early kill signal to tasks where a vma covers
+ * the page but the corrupted page is not necessarily
+ * mapped it in its pte.
+ * Assume applications who requested early kill want
+ * to be informed of all such data corruptions.
+ */
+ if (vma->vm_mm == t->mm)
+ add_to_kill(t, page, vma, to_kill, tkc);
+ }
+ }
+ read_unlock(&tasklist_lock);
+ i_mmap_unlock_read(mapping);
+}
+
+/*
+ * Collect the processes who have the corrupted page mapped to kill.
+ * This is done in two steps for locking reasons.
+ * First preallocate one tokill structure outside the spin locks,
+ * so that we can kill at least one process reasonably reliable.
+ */
+static void collect_procs(struct page *page, struct list_head *tokill,
+ int force_early)
+{
+ struct to_kill *tk;
+
+ if (!page->mapping)
+ return;
+
+ tk = kmalloc(sizeof(struct to_kill), GFP_NOIO);
+ if (!tk)
+ return;
+ if (PageAnon(page))
+ collect_procs_anon(page, tokill, &tk, force_early);
+ else
+ collect_procs_file(page, tokill, &tk, force_early);
+ kfree(tk);
+}
+
+/*
+ * Error handlers for various types of pages.
+ */
+
+enum outcome {
+ IGNORED, /* Error: cannot be handled */
+ FAILED, /* Error: handling failed */
+ DELAYED, /* Will be handled later */
+ RECOVERED, /* Successfully recovered */
+};
+
+static const char *action_name[] = {
+ [IGNORED] = "Ignored",
+ [FAILED] = "Failed",
+ [DELAYED] = "Delayed",
+ [RECOVERED] = "Recovered",
+};
+
+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",
+};
+
+/*
+ * 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;
+}
+
+/*
+ * 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;
+
+ delete_from_lru_cache(p);
+
+ /*
+ * For anonymous pages we're done the only reference left
+ * should be the one m_f() holds.
+ */
+ if (PageAnon(p))
+ return RECOVERED;
+
+ /*
+ * Now truncate the page in the page cache. This is really
+ * more like a "temporary hole punch"
+ * Don't do this for block devices when someone else
+ * has a reference, because it could be file system metadata
+ * and that's not safe to truncate.
+ */
+ mapping = page_mapping(p);
+ if (!mapping) {
+ /*
+ * Page has been teared down in the meanwhile
+ */
+ return FAILED;
+ }
+
+ /*
+ * Truncation is a bit tricky. Enable it per file system for now.
+ *
+ * Open: to take i_mutex or not for this? Right now we don't.
+ */
+ if (mapping->a_ops->error_remove_page) {
+ err = mapping->a_ops->error_remove_page(mapping, p);
+ if (err != 0) {
+ printk(KERN_INFO "MCE %#lx: Failed to punch page: %d\n",
+ pfn, err);
+ } else if (page_has_private(p) &&
+ !try_to_release_page(p, GFP_NOIO)) {
+ pr_info("MCE %#lx: failed to release buffers\n", pfn);
+ } else {
+ ret = RECOVERED;
+ }
+ } else {
+ /*
+ * If the file system doesn't support it just invalidate
+ * This fails on dirty or anything with private pages
+ */
+ if (invalidate_inode_page(p))
+ ret = RECOVERED;
+ else
+ printk(KERN_INFO "MCE %#lx: Failed to invalidate\n",
+ pfn);
+ }
+ return ret;
+}
+
+/*
+ * Dirty pagecache 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 between 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)
+{
+ ClearPageDirty(p);
+ /* Trigger EIO in shmem: */
+ ClearPageUptodate(p);
+
+ if (!delete_from_lru_cache(p))
+ return DELAYED;
+ else
+ return FAILED;
+}
+
+static int me_swapcache_clean(struct page *p, unsigned long pfn)
+{
+ delete_from_swap_cache(p);
+
+ if (!delete_from_lru_cache(p))
+ return RECOVERED;
+ else
+ return FAILED;
+}
+
+/*
+ * Huge pages. Needs work.
+ * Issues:
+ * - 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.
+ */
+static int me_huge_page(struct page *p, unsigned long pfn)
+{
+ int res = 0;
+ 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))) {
+ res = dequeue_hwpoisoned_huge_page(hpage);
+ if (!res)
+ return RECOVERED;
+ }
+ return DELAYED;
+}
+
+/*
+ * 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 extremely 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 reserved (1UL << PG_reserved)
+
+static struct page_state {
+ unsigned long mask;
+ unsigned long res;
+ enum action_page_type type;
+ int (*action)(struct page *p, unsigned long pfn);
+} error_states[] = {
+ { reserved, reserved, MSG_KERNEL, me_kernel },
+ /*
+ * free pages are specially detected outside this table:
+ * PG_buddy pages only make a small fraction of all free pages.
+ */
+
+ /*
+ * 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, MSG_SLAB, me_kernel },
+
+#ifdef CONFIG_PAGEFLAGS_EXTENDED
+ { head, head, MSG_HUGE, me_huge_page },
+ { tail, tail, MSG_HUGE, me_huge_page },
+#else
+ { compound, compound, MSG_HUGE, me_huge_page },
+#endif
+
+ { sc|dirty, sc|dirty, MSG_DIRTY_SWAPCACHE, me_swapcache_dirty },
+ { sc|dirty, sc, MSG_CLEAN_SWAPCACHE, me_swapcache_clean },
+
+ { mlock|dirty, mlock|dirty, MSG_DIRTY_MLOCKED_LRU, me_pagecache_dirty },
+ { mlock|dirty, mlock, MSG_CLEAN_MLOCKED_LRU, me_pagecache_clean },
+
+ { unevict|dirty, unevict|dirty, MSG_DIRTY_UNEVICTABLE_LRU, me_pagecache_dirty },
+ { unevict|dirty, unevict, MSG_CLEAN_UNEVICTABLE_LRU, me_pagecache_clean },
+
+ { lru|dirty, lru|dirty, MSG_DIRTY_LRU, me_pagecache_dirty },
+ { lru|dirty, lru, MSG_CLEAN_LRU, me_pagecache_clean },
+
+ /*
+ * Catchall entry: must be at end.
+ */
+ { 0, 0, MSG_UNKNOWN, me_unknown },
+};
+
+#undef dirty
+#undef sc
+#undef unevict
+#undef mlock
+#undef writeback
+#undef lru
+#undef swapbacked
+#undef head
+#undef tail
+#undef compound
+#undef slab
+#undef reserved
+
+/*
+ * "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().
+ */
+static void action_result(unsigned long pfn, enum action_page_type type, int result)
+{
+ pr_err("MCE %#lx: recovery action for %s: %s\n",
+ pfn, action_page_types[type], action_name[result]);
+}
+
+static int page_action(struct page_state *ps, struct page *p,
+ unsigned long pfn)
+{
+ int result;
+ int count;
+
+ result = ps->action(p, pfn);
+
+ count = page_count(p) - 1;
+ if (ps->action == me_swapcache_dirty && result == DELAYED)
+ count--;
+ if (count != 0) {
+ printk(KERN_ERR
+ "MCE %#lx: %s still referenced by %d users\n",
+ pfn, action_page_types[ps->type], count);
+ result = FAILED;
+ }
+ action_result(pfn, ps->type, result);
+
+ /* Could do more checks here if page looks ok */
+ /*
+ * Could adjust zone counters here to correct for the missing page.
+ */
+
+ return (result == RECOVERED || result == DELAYED) ? 0 : -EBUSY;
+}
+
+/*
+ * 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 int hwpoison_user_mappings(struct page *p, unsigned long pfn,
+ int trapno, int flags, struct page **hpagep)
+{
+ enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
+ struct address_space *mapping;
+ LIST_HEAD(tokill);
+ int ret;
+ int kill = 1, forcekill;
+ struct page *hpage = *hpagep;
+ struct page *ppage;
+
+ /*
+ * 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)))
+ return SWAP_SUCCESS;
+
+ /*
+ * 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(hpage))
+ return SWAP_SUCCESS;
+
+ if (PageKsm(p)) {
+ pr_err("MCE %#lx: can't handle KSM pages.\n", pfn);
+ return SWAP_FAIL;
+ }
+
+ 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.
+ * XXX: the dirty test could be racy: set_page_dirty() may not always
+ * be called inside page lock (it's recommended but not enforced).
+ */
+ mapping = page_mapping(hpage);
+ if (!(flags & MF_MUST_KILL) && !PageDirty(hpage) && mapping &&
+ mapping_cap_writeback_dirty(mapping)) {
+ if (page_mkclean(hpage)) {
+ SetPageDirty(hpage);
+ } else {
+ kill = 0;
+ ttu |= TTU_IGNORE_HWPOISON;
+ printk(KERN_INFO
+ "MCE %#lx: corrupted page was clean: dropped without side effects\n",
+ pfn);
+ }
+ }
+
+ /*
+ * 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;
+
+ 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;
+ }
+ /*
+ * 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
+ * to it. Similarly, page lock is shifted.
+ */
+ if (hpage != p) {
+ if (!(flags & MF_COUNT_INCREASED)) {
+ put_page(hpage);
+ get_page(p);
+ }
+ lock_page(p);
+ unlock_page(hpage);
+ *hpagep = p;
+ }
+ /* THP is split, so ppage should be the real poisoned page. */
+ ppage = p;
+ }
+ }
+
+ /*
+ * 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(ppage, &tokill, flags & MF_ACTION_REQUIRED);
+
+ ret = try_to_unmap(ppage, ttu);
+ if (ret != SWAP_SUCCESS)
+ printk(KERN_ERR "MCE %#lx: failed to unmap page (mapcount=%d)\n",
+ pfn, page_mapcount(ppage));
+
+ /*
+ * 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 or the process is not restartable,
+ * 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.
+ */
+ forcekill = PageDirty(ppage) || (flags & MF_MUST_KILL);
+ kill_procs(&tokill, forcekill, trapno,
+ ret != SWAP_SUCCESS, p, pfn, flags);
+
+ return ret;
+}
+
+static void set_page_hwpoison_huge_page(struct page *hpage)
+{
+ int i;
+ int nr_pages = 1 << compound_order(hpage);
+ for (i = 0; i < nr_pages; i++)
+ SetPageHWPoison(hpage + i);
+}
+
+static void clear_page_hwpoison_huge_page(struct page *hpage)
+{
+ int i;
+ int nr_pages = 1 << compound_order(hpage);
+ for (i = 0; i < nr_pages; i++)
+ ClearPageHWPoison(hpage + i);
+}
+
+/**
+ * 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)
+{
+ struct page_state *ps;
+ struct page *p;
+ struct page *hpage;
+ int res;
+ unsigned int nr_pages;
+ unsigned long page_flags;
+
+ if (!sysctl_memory_failure_recovery)
+ panic("Memory failure from trap %d on page %lx", trapno, pfn);
+
+ if (!pfn_valid(pfn)) {
+ printk(KERN_ERR
+ "MCE %#lx: memory outside kernel control\n",
+ pfn);
+ return -ENXIO;
+ }
+
+ p = pfn_to_page(pfn);
+ hpage = compound_head(p);
+ if (TestSetPageHWPoison(p)) {
+ printk(KERN_ERR "MCE %#lx: already hardware poisoned\n", pfn);
+ return 0;
+ }
+
+ /*
+ * 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;
+ atomic_long_add(nr_pages, &num_poisoned_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 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.
+ * 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 (!(flags & MF_COUNT_INCREASED) &&
+ !get_page_unless_zero(hpage)) {
+ if (is_free_buddy_page(p)) {
+ action_result(pfn, MSG_BUDDY, DELAYED);
+ return 0;
+ } else if (PageHuge(hpage)) {
+ /*
+ * Check "filter hit" and "race with other subpage."
+ */
+ lock_page(hpage);
+ 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;
+ }
+ }
+ set_page_hwpoison_huge_page(hpage);
+ res = dequeue_hwpoisoned_huge_page(hpage);
+ action_result(pfn, MSG_FREE_HUGE,
+ res ? IGNORED : DELAYED);
+ unlock_page(hpage);
+ return res;
+ } else {
+ action_result(pfn, MSG_KERNEL_HIGH_ORDER, IGNORED);
+ return -EBUSY;
+ }
+ }
+
+ /*
+ * 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.
+ */
+ if (!PageHuge(p)) {
+ if (!PageLRU(hpage))
+ shake_page(hpage, 0);
+ if (!PageLRU(hpage)) {
+ /*
+ * shake_page could have turned it free.
+ */
+ if (is_free_buddy_page(p)) {
+ if (flags & MF_COUNT_INCREASED)
+ action_result(pfn, MSG_BUDDY, DELAYED);
+ else
+ action_result(pfn, MSG_BUDDY_2ND,
+ DELAYED);
+ return 0;
+ }
+ }
+ }
+
+ lock_page(hpage);
+
+ /*
+ * The page could have changed compound pages during the locking.
+ * If this happens just bail out.
+ */
+ if (compound_head(p) != hpage) {
+ action_result(pfn, MSG_DIFFERENT_COMPOUND, IGNORED);
+ res = -EBUSY;
+ goto out;
+ }
+
+ /*
+ * 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;
+
+ /*
+ * unpoison always clear PG_hwpoison inside page lock
+ */
+ if (!PageHWPoison(p)) {
+ printk(KERN_ERR "MCE %#lx: just unpoisoned\n", pfn);
+ atomic_long_sub(nr_pages, &num_poisoned_pages);
+ put_page(hpage);
+ res = 0;
+ goto out;
+ }
+ if (hwpoison_filter(p)) {
+ if (TestClearPageHWPoison(p))
+ atomic_long_sub(nr_pages, &num_poisoned_pages);
+ unlock_page(hpage);
+ put_page(hpage);
+ return 0;
+ }
+
+ if (!PageHuge(p) && !PageTransTail(p) && !PageLRU(p))
+ goto identify_page_state;
+
+ /*
+ * For error on the tail page, we should set PG_hwpoison
+ * on the head page to show that the hugepage is hwpoisoned
+ */
+ if (PageHuge(p) && PageTail(p) && TestSetPageHWPoison(hpage)) {
+ action_result(pfn, MSG_POISONED_HUGE, IGNORED);
+ 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);
+
+ /*
+ * It's very difficult to mess with pages currently under IO
+ * and in many cases impossible, so we just avoid it here.
+ */
+ wait_on_page_writeback(p);
+
+ /*
+ * Now take care of user space mappings.
+ * Abort on fail: __delete_from_page_cache() assumes unmapped page.
+ *
+ * When the raw error page is thp tail page, hpage points to the raw
+ * page after thp split.
+ */
+ if (hwpoison_user_mappings(p, pfn, trapno, flags, &hpage)
+ != SWAP_SUCCESS) {
+ action_result(pfn, MSG_UNMAP_FAILED, IGNORED);
+ res = -EBUSY;
+ goto out;
+ }
+
+ /*
+ * Torn down by someone else?
+ */
+ if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) {
+ action_result(pfn, MSG_TRUNCATED_LRU, IGNORED);
+ res = -EBUSY;
+ goto out;
+ }
+
+identify_page_state:
+ res = -EBUSY;
+ /*
+ * 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)
+ break;
+
+ page_flags |= (p->flags & (1UL << PG_dirty));
+
+ if (!ps->mask)
+ for (ps = error_states;; ps++)
+ if ((page_flags & ps->mask) == ps->res)
+ break;
+ res = page_action(ps, p, pfn);
+out:
+ unlock_page(hpage);
+ return res;
+}
+EXPORT_SYMBOL_GPL(memory_failure);
+
+#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);
+ if (kfifo_put(&mf_cpu->fifo, entry))
+ schedule_work_on(smp_processor_id(), &mf_cpu->work);
+ else
+ pr_err("Memory failure: buffer overflow when queuing memory failure at %#lx\n",
+ 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;
+
+ mf_cpu = this_cpu_ptr(&memory_failure_cpu);
+ 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;
+ 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);
+ }
+}
+
+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);
+
+/**
+ * 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;
+ unsigned int nr_pages;
+
+ if (!pfn_valid(pfn))
+ return -ENXIO;
+
+ p = pfn_to_page(pfn);
+ page = compound_head(p);
+
+ if (!PageHWPoison(p)) {
+ pr_info("MCE: Page was already unpoisoned %#lx\n", pfn);
+ return 0;
+ }
+
+ /*
+ * 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.
+ */
+ if (!PageHuge(page) && PageTransHuge(page)) {
+ pr_info("MCE: Memory failure is now running on %#lx\n", pfn);
+ return 0;
+ }
+
+ nr_pages = 1 << compound_order(page);
+
+ if (!get_page_unless_zero(page)) {
+ /*
+ * 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)) {
+ pr_info("MCE: Memory failure is now running on free hugepage %#lx\n", pfn);
+ return 0;
+ }
+ if (TestClearPageHWPoison(p))
+ atomic_long_dec(&num_poisoned_pages);
+ pr_info("MCE: Software-unpoisoned free page %#lx\n", pfn);
+ return 0;
+ }
+
+ lock_page(page);
+ /*
+ * 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.
+ */
+ if (TestClearPageHWPoison(page)) {
+ pr_info("MCE: Software-unpoisoned page %#lx\n", pfn);
+ atomic_long_sub(nr_pages, &num_poisoned_pages);
+ freeit = 1;
+ if (PageHuge(page))
+ clear_page_hwpoison_huge_page(page);
+ }
+ unlock_page(page);
+
+ put_page(page);
+ if (freeit && !(pfn == my_zero_pfn(0) && page_count(p) == 1))
+ put_page(page);
+
+ return 0;
+}
+EXPORT_SYMBOL(unpoison_memory);
+
+static struct page *new_page(struct page *p, unsigned long private, int **x)
+{
+ int nid = page_to_nid(p);
+ 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);
+}
+
+/*
+ * 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.
+ */
+static int __get_any_page(struct page *p, unsigned long pfn, int flags)
+{
+ int ret;
+
+ if (flags & MF_COUNT_INCREASED)
+ return 1;
+
+ /*
+ * When the target page is a free hugepage, just remove it
+ * from free hugepage list.
+ */
+ if (!get_page_unless_zero(compound_head(p))) {
+ if (PageHuge(p)) {
+ pr_info("%s: %#lx free huge page\n", __func__, pfn);
+ ret = 0;
+ } else if (is_free_buddy_page(p)) {
+ pr_info("%s: %#lx free buddy page\n", __func__, pfn);
+ ret = 0;
+ } else {
+ pr_info("%s: %#lx: unknown zero refcount page type %lx\n",
+ __func__, pfn, p->flags);
+ ret = -EIO;
+ }
+ } else {
+ /* Not a free page */
+ ret = 1;
+ }
+ return ret;
+}
+
+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;
+}
+
+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);
+ LIST_HEAD(pagelist);
+
+ /*
+ * This double-check of PageHWPoison is to avoid the race with
+ * memory_failure(). See also comment in __soft_offline_page().
+ */
+ lock_page(hpage);
+ if (PageHWPoison(hpage)) {
+ unlock_page(hpage);
+ put_page(hpage);
+ pr_info("soft offline: %#lx hugepage already poisoned\n", pfn);
+ return -EBUSY;
+ }
+ unlock_page(hpage);
+
+ 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;
+ }
+
+ ret = migrate_pages(&pagelist, new_page, NULL, MPOL_MF_MOVE_ALL,
+ MIGRATE_SYNC, MR_MEMORY_FAILURE);
+ if (ret) {
+ pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
+ pfn, ret, page->flags);
+ /*
+ * 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;
+ } else {
+ /* 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);
+ }
+ }
+ return ret;
+}
+
+static int __soft_offline_page(struct page *page, int flags)
+{
+ int ret;
+ unsigned long pfn = page_to_pfn(page);
+
+ /*
+ * 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().
+ */
+ lock_page(page);
+ wait_on_page_writeback(page);
+ if (PageHWPoison(page)) {
+ unlock_page(page);
+ put_page(page);
+ pr_info("soft offline: %#lx page already poisoned\n", pfn);
+ return -EBUSY;
+ }
+ /*
+ * 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) {
+ put_page(page);
+ pr_info("soft_offline: %#lx: invalidated\n", pfn);
+ SetPageHWPoison(page);
+ atomic_long_inc(&num_poisoned_pages);
+ return 0;
+ }
+
+ /*
+ * 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);
+ /*
+ * Drop page reference which is came from get_any_page()
+ * successful isolate_lru_page() already took another one.
+ */
+ put_page(page);
+ if (!ret) {
+ LIST_HEAD(pagelist);
+ inc_zone_page_state(page, NR_ISOLATED_ANON +
+ page_is_file_cache(page));
+ list_add(&page->lru, &pagelist);
+ ret = migrate_pages(&pagelist, new_page, NULL, MPOL_MF_MOVE_ALL,
+ MIGRATE_SYNC, MR_MEMORY_FAILURE);
+ if (ret) {
+ 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);
+ }
+
+ pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
+ pfn, ret, page->flags);
+ if (ret > 0)
+ ret = -EIO;
+ } else {
+ /*
+ * 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))
+ drain_all_pages(page_zone(page));
+ SetPageHWPoison(page);
+ if (!is_free_buddy_page(page))
+ pr_info("soft offline: %#lx: page leaked\n",
+ pfn);
+ atomic_long_inc(&num_poisoned_pages);
+ }
+ } else {
+ pr_info("soft offline: %#lx: isolation failed: %d, page count %d, type %lx\n",
+ pfn, ret, page_count(page), page->flags);
+ }
+ return ret;
+}
+
+/**
+ * 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);
+ struct page *hpage = compound_head(page);
+
+ 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;
+ }
+ }
+
+ get_online_mems();
+
+ /*
+ * 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);
+
+ ret = get_any_page(page, pfn, flags);
+ put_online_mems();
+ if (ret > 0) { /* for in-use pages */
+ if (PageHuge(page))
+ ret = soft_offline_huge_page(page, flags);
+ else
+ ret = __soft_offline_page(page, flags);
+ } else if (ret == 0) { /* for free pages */
+ if (PageHuge(page)) {
+ set_page_hwpoison_huge_page(hpage);
+ if (!dequeue_hwpoisoned_huge_page(hpage))
+ atomic_long_add(1 << compound_order(hpage),
+ &num_poisoned_pages);
+ } else {
+ if (!TestSetPageHWPoison(page))
+ atomic_long_inc(&num_poisoned_pages);
+ }
+ }
+ unset_migratetype_isolate(page, MIGRATE_MOVABLE);
+ return ret;
+}