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-rw-r--r--mm/memory-failure.c1936
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diff --git a/mm/memory-failure.c b/mm/memory-failure.c
new file mode 100644
index 000000000..f320ff02c
--- /dev/null
+++ b/mm/memory-failure.c
@@ -0,0 +1,1936 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2008, 2009 Intel Corporation
+ * Authors: Andi Kleen, Fengguang Wu
+ *
+ * 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.
+ *
+ * It can be very tempting to add handling for obscure cases here.
+ * In general any code for handling new cases should only be added iff:
+ * - You know how to test it.
+ * - You have a test that can be added to mce-test
+ * https://git.kernel.org/cgit/utils/cpu/mce/mce-test.git/
+ * - The case actually shows up as a frequent (top 10) page state in
+ * tools/vm/page-types when running a real workload.
+ *
+ * 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.
+ */
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/page-flags.h>
+#include <linux/kernel-page-flags.h>
+#include <linux/sched/signal.h>
+#include <linux/sched/task.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/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/memremap.h>
+#include <linux/kfifo.h>
+#include <linux/ratelimit.h>
+#include <linux/page-isolation.h>
+#include "internal.h"
+#include "ras/ras_event.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);
+
+static bool page_handle_poison(struct page *page, bool hugepage_or_freepage, bool release)
+{
+ if (hugepage_or_freepage) {
+ /*
+ * Doing this check for free pages is also fine since dissolve_free_huge_page
+ * returns 0 for non-hugetlb pages as well.
+ */
+ if (dissolve_free_huge_page(page) || !take_page_off_buddy(page))
+ /*
+ * We could fail to take off the target page from buddy
+ * for example due to racy page allocaiton, but that's
+ * acceptable because soft-offlined page is not broken
+ * and if someone really want to use it, they should
+ * take it.
+ */
+ return false;
+ }
+
+ SetPageHWPoison(page);
+ if (release)
+ put_page(page);
+ page_ref_inc(page);
+ num_poisoned_pages_inc();
+
+ return true;
+}
+
+#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
+u64 hwpoison_filter_memcg;
+EXPORT_SYMBOL_GPL(hwpoison_filter_memcg);
+static int hwpoison_filter_task(struct page *p)
+{
+ if (!hwpoison_filter_memcg)
+ return 0;
+
+ if (page_cgroup_ino(p) != 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);
+
+/*
+ * 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;
+ short size_shift;
+};
+
+/*
+ * 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 to_kill *tk, unsigned long pfn, int flags)
+{
+ struct task_struct *t = tk->tsk;
+ short addr_lsb = tk->size_shift;
+ int ret = 0;
+
+ pr_err("Memory failure: %#lx: Sending SIGBUS to %s:%d due to hardware memory corruption\n",
+ pfn, t->comm, t->pid);
+
+ if (flags & MF_ACTION_REQUIRED) {
+ WARN_ON_ONCE(t != current);
+ ret = force_sig_mceerr(BUS_MCEERR_AR,
+ (void __user *)tk->addr, addr_lsb);
+ } 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?
+ */
+ ret = send_sig_mceerr(BUS_MCEERR_AO, (void __user *)tk->addr,
+ addr_lsb, t); /* synchronous? */
+ }
+ if (ret < 0)
+ pr_info("Memory failure: 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 (PageHuge(p))
+ return;
+
+ 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);
+
+static unsigned long dev_pagemap_mapping_shift(struct page *page,
+ struct vm_area_struct *vma)
+{
+ unsigned long address = vma_address(page, vma);
+ pgd_t *pgd;
+ p4d_t *p4d;
+ pud_t *pud;
+ pmd_t *pmd;
+ pte_t *pte;
+
+ pgd = pgd_offset(vma->vm_mm, address);
+ if (!pgd_present(*pgd))
+ return 0;
+ p4d = p4d_offset(pgd, address);
+ if (!p4d_present(*p4d))
+ return 0;
+ pud = pud_offset(p4d, address);
+ if (!pud_present(*pud))
+ return 0;
+ if (pud_devmap(*pud))
+ return PUD_SHIFT;
+ pmd = pmd_offset(pud, address);
+ if (!pmd_present(*pmd))
+ return 0;
+ if (pmd_devmap(*pmd))
+ return PMD_SHIFT;
+ pte = pte_offset_map(pmd, address);
+ if (!pte_present(*pte))
+ return 0;
+ if (pte_devmap(*pte))
+ return PAGE_SHIFT;
+ return 0;
+}
+
+/*
+ * 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.
+ */
+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 *tk;
+
+ tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
+ if (!tk) {
+ pr_err("Memory failure: Out of memory while machine check handling\n");
+ return;
+ }
+
+ tk->addr = page_address_in_vma(p, vma);
+ if (is_zone_device_page(p))
+ tk->size_shift = dev_pagemap_mapping_shift(p, vma);
+ else
+ tk->size_shift = page_shift(compound_head(p));
+
+ /*
+ * Send SIGKILL if "tk->addr == -EFAULT". Also, as
+ * "tk->size_shift" is always non-zero for !is_zone_device_page(),
+ * so "tk->size_shift == 0" effectively checks no mapping on
+ * ZONE_DEVICE. Indeed, when a devdax page is mmapped N times
+ * to a process' address space, it's possible not all N VMAs
+ * contain mappings for the page, but at least one VMA does.
+ * Only deliver SIGBUS with payload derived from the VMA that
+ * has a mapping for the page.
+ */
+ if (tk->addr == -EFAULT) {
+ pr_info("Memory failure: Unable to find user space address %lx in %s\n",
+ page_to_pfn(p), tsk->comm);
+ } else if (tk->size_shift == 0) {
+ kfree(tk);
+ return;
+ }
+
+ 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, bool fail,
+ 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 == -EFAULT) {
+ pr_err("Memory failure: %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n",
+ pfn, tk->tsk->comm, tk->tsk->pid);
+ do_send_sig_info(SIGKILL, SEND_SIG_PRIV,
+ tk->tsk, PIDTYPE_PID);
+ }
+
+ /*
+ * 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, pfn, flags) < 0)
+ pr_err("Memory failure: %#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) {
+ if (t->flags & PF_MCE_EARLY)
+ return t;
+ } else {
+ if (sysctl_memory_failure_early_kill)
+ 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.
+ *
+ * Note that the above is true for Action Optional case, but not for Action
+ * Required case where SIGBUS should sent only to the current thread.
+ */
+static struct task_struct *task_early_kill(struct task_struct *tsk,
+ int force_early)
+{
+ if (!tsk->mm)
+ return NULL;
+ if (force_early) {
+ /*
+ * Comparing ->mm here because current task might represent
+ * a subthread, while tsk always points to the main thread.
+ */
+ if (tsk->mm == current->mm)
+ return current;
+ else
+ return NULL;
+ }
+ return find_early_kill_thread(tsk);
+}
+
+/*
+ * Collect processes when the error hit an anonymous page.
+ */
+static void collect_procs_anon(struct page *page, struct list_head *to_kill,
+ 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);
+ }
+ }
+ 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,
+ int force_early)
+{
+ struct vm_area_struct *vma;
+ struct task_struct *tsk;
+ struct address_space *mapping = page->mapping;
+ pgoff_t pgoff;
+
+ i_mmap_lock_read(mapping);
+ read_lock(&tasklist_lock);
+ pgoff = page_to_pgoff(page);
+ for_each_process(tsk) {
+ 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);
+ }
+ }
+ read_unlock(&tasklist_lock);
+ i_mmap_unlock_read(mapping);
+}
+
+/*
+ * Collect the processes who have the corrupted page mapped to kill.
+ */
+static void collect_procs(struct page *page, struct list_head *tokill,
+ int force_early)
+{
+ if (!page->mapping)
+ return;
+
+ if (PageAnon(page))
+ collect_procs_anon(page, tokill, force_early);
+ else
+ collect_procs_file(page, tokill, force_early);
+}
+
+static const char *action_name[] = {
+ [MF_IGNORED] = "Ignored",
+ [MF_FAILED] = "Failed",
+ [MF_DELAYED] = "Delayed",
+ [MF_RECOVERED] = "Recovered",
+};
+
+static const char * const action_page_types[] = {
+ [MF_MSG_KERNEL] = "reserved kernel page",
+ [MF_MSG_KERNEL_HIGH_ORDER] = "high-order kernel page",
+ [MF_MSG_SLAB] = "kernel slab page",
+ [MF_MSG_DIFFERENT_COMPOUND] = "different compound page after locking",
+ [MF_MSG_POISONED_HUGE] = "huge page already hardware poisoned",
+ [MF_MSG_HUGE] = "huge page",
+ [MF_MSG_FREE_HUGE] = "free huge page",
+ [MF_MSG_NON_PMD_HUGE] = "non-pmd-sized huge page",
+ [MF_MSG_UNMAP_FAILED] = "unmapping failed page",
+ [MF_MSG_DIRTY_SWAPCACHE] = "dirty swapcache page",
+ [MF_MSG_CLEAN_SWAPCACHE] = "clean swapcache page",
+ [MF_MSG_DIRTY_MLOCKED_LRU] = "dirty mlocked LRU page",
+ [MF_MSG_CLEAN_MLOCKED_LRU] = "clean mlocked LRU page",
+ [MF_MSG_DIRTY_UNEVICTABLE_LRU] = "dirty unevictable LRU page",
+ [MF_MSG_CLEAN_UNEVICTABLE_LRU] = "clean unevictable LRU page",
+ [MF_MSG_DIRTY_LRU] = "dirty LRU page",
+ [MF_MSG_CLEAN_LRU] = "clean LRU page",
+ [MF_MSG_TRUNCATED_LRU] = "already truncated LRU page",
+ [MF_MSG_BUDDY] = "free buddy page",
+ [MF_MSG_BUDDY_2ND] = "free buddy page (2nd try)",
+ [MF_MSG_DAX] = "dax page",
+ [MF_MSG_UNSPLIT_THP] = "unsplit thp",
+ [MF_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);
+
+ /*
+ * Poisoned page might never drop its ref count to 0 so we have
+ * to uncharge it manually from its memcg.
+ */
+ mem_cgroup_uncharge(p);
+
+ /*
+ * drop the page count elevated by isolate_lru_page()
+ */
+ put_page(p);
+ return 0;
+ }
+ return -EIO;
+}
+
+static int truncate_error_page(struct page *p, unsigned long pfn,
+ struct address_space *mapping)
+{
+ int ret = MF_FAILED;
+
+ if (mapping->a_ops->error_remove_page) {
+ int err = mapping->a_ops->error_remove_page(mapping, p);
+
+ if (err != 0) {
+ pr_info("Memory failure: %#lx: Failed to punch page: %d\n",
+ pfn, err);
+ } else if (page_has_private(p) &&
+ !try_to_release_page(p, GFP_NOIO)) {
+ pr_info("Memory failure: %#lx: failed to release buffers\n",
+ pfn);
+ } else {
+ ret = MF_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 = MF_RECOVERED;
+ else
+ pr_info("Memory failure: %#lx: Failed to invalidate\n",
+ pfn);
+ }
+
+ return ret;
+}
+
+/*
+ * 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 MF_IGNORED;
+}
+
+/*
+ * Page in unknown state. Do nothing.
+ */
+static int me_unknown(struct page *p, unsigned long pfn)
+{
+ pr_err("Memory failure: %#lx: Unknown page state\n", pfn);
+ return MF_FAILED;
+}
+
+/*
+ * Clean (or cleaned) page cache page.
+ */
+static int me_pagecache_clean(struct page *p, unsigned long pfn)
+{
+ 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 MF_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 MF_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.
+ */
+ return truncate_error_page(p, pfn, mapping);
+}
+
+/*
+ * 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 MF_DELAYED;
+ else
+ return MF_FAILED;
+}
+
+static int me_swapcache_clean(struct page *p, unsigned long pfn)
+{
+ delete_from_swap_cache(p);
+
+ if (!delete_from_lru_cache(p))
+ return MF_RECOVERED;
+ else
+ return MF_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);
+ struct address_space *mapping;
+
+ if (!PageHuge(hpage))
+ return MF_DELAYED;
+
+ mapping = page_mapping(hpage);
+ if (mapping) {
+ res = truncate_error_page(hpage, pfn, mapping);
+ } else {
+ unlock_page(hpage);
+ /*
+ * migration entry prevents later access on error anonymous
+ * hugepage, so we can free and dissolve it into buddy to
+ * save healthy subpages.
+ */
+ if (PageAnon(hpage))
+ put_page(hpage);
+ dissolve_free_huge_page(p);
+ res = MF_RECOVERED;
+ lock_page(hpage);
+ }
+
+ return res;
+}
+
+/*
+ * 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) | (1UL << PG_swapbacked))
+#define unevict (1UL << PG_unevictable)
+#define mlock (1UL << PG_mlocked)
+#define lru (1UL << PG_lru)
+#define head (1UL << PG_head)
+#define slab (1UL << PG_slab)
+#define reserved (1UL << PG_reserved)
+
+static struct page_state {
+ unsigned long mask;
+ unsigned long res;
+ enum mf_action_page_type type;
+ int (*action)(struct page *p, unsigned long pfn);
+} error_states[] = {
+ { reserved, reserved, MF_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, MF_MSG_SLAB, me_kernel },
+
+ { head, head, MF_MSG_HUGE, me_huge_page },
+
+ { sc|dirty, sc|dirty, MF_MSG_DIRTY_SWAPCACHE, me_swapcache_dirty },
+ { sc|dirty, sc, MF_MSG_CLEAN_SWAPCACHE, me_swapcache_clean },
+
+ { mlock|dirty, mlock|dirty, MF_MSG_DIRTY_MLOCKED_LRU, me_pagecache_dirty },
+ { mlock|dirty, mlock, MF_MSG_CLEAN_MLOCKED_LRU, me_pagecache_clean },
+
+ { unevict|dirty, unevict|dirty, MF_MSG_DIRTY_UNEVICTABLE_LRU, me_pagecache_dirty },
+ { unevict|dirty, unevict, MF_MSG_CLEAN_UNEVICTABLE_LRU, me_pagecache_clean },
+
+ { lru|dirty, lru|dirty, MF_MSG_DIRTY_LRU, me_pagecache_dirty },
+ { lru|dirty, lru, MF_MSG_CLEAN_LRU, me_pagecache_clean },
+
+ /*
+ * Catchall entry: must be at end.
+ */
+ { 0, 0, MF_MSG_UNKNOWN, me_unknown },
+};
+
+#undef dirty
+#undef sc
+#undef unevict
+#undef mlock
+#undef lru
+#undef head
+#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 mf_action_page_type type,
+ enum mf_result result)
+{
+ trace_memory_failure_event(pfn, type, result);
+
+ pr_err("Memory failure: %#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 == MF_DELAYED)
+ count--;
+ if (count > 0) {
+ pr_err("Memory failure: %#lx: %s still referenced by %d users\n",
+ pfn, action_page_types[ps->type], count);
+ result = MF_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 == MF_RECOVERED || result == MF_DELAYED) ? 0 : -EBUSY;
+}
+
+/**
+ * get_hwpoison_page() - Get refcount for memory error handling:
+ * @page: raw error page (hit by memory error)
+ *
+ * Return: return 0 if failed to grab the refcount, otherwise true (some
+ * non-zero value.)
+ */
+static int get_hwpoison_page(struct page *page)
+{
+ struct page *head = compound_head(page);
+
+ if (!PageHuge(head) && PageTransHuge(head)) {
+ /*
+ * Non anonymous thp exists only in allocation/free time. We
+ * can't handle such a case correctly, so let's give it up.
+ * This should be better than triggering BUG_ON when kernel
+ * tries to touch the "partially handled" page.
+ */
+ if (!PageAnon(head)) {
+ pr_err("Memory failure: %#lx: non anonymous thp\n",
+ page_to_pfn(page));
+ return 0;
+ }
+ }
+
+ if (get_page_unless_zero(head)) {
+ if (head == compound_head(page))
+ return 1;
+
+ pr_info("Memory failure: %#lx cannot catch tail\n",
+ page_to_pfn(page));
+ put_page(head);
+ }
+
+ return 0;
+}
+
+/*
+ * 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 bool hwpoison_user_mappings(struct page *p, unsigned long pfn,
+ int flags, struct page **hpagep)
+{
+ enum ttu_flags ttu = TTU_IGNORE_MLOCK;
+ struct address_space *mapping;
+ LIST_HEAD(tokill);
+ bool unmap_success = true;
+ int kill = 1, forcekill;
+ struct page *hpage = *hpagep;
+ bool mlocked = PageMlocked(hpage);
+
+ /*
+ * Here we are interested only in user-mapped pages, so skip any
+ * other types of pages.
+ */
+ if (PageReserved(p) || PageSlab(p))
+ return true;
+ if (!(PageLRU(hpage) || PageHuge(p)))
+ return true;
+
+ /*
+ * This check implies we don't kill processes if their pages
+ * are in the swap cache early. Those are always late kills.
+ */
+ if (!page_mapped(p))
+ return true;
+
+ if (PageKsm(p)) {
+ pr_err("Memory failure: %#lx: can't handle KSM pages.\n", pfn);
+ return false;
+ }
+
+ if (PageSwapCache(p)) {
+ pr_err("Memory failure: %#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_can_writeback(mapping)) {
+ if (page_mkclean(hpage)) {
+ SetPageDirty(hpage);
+ } else {
+ kill = 0;
+ ttu |= TTU_IGNORE_HWPOISON;
+ pr_info("Memory failure: %#lx: corrupted page was clean: dropped without side effects\n",
+ pfn);
+ }
+ }
+
+ /*
+ * First collect all the processes that have the page
+ * mapped in dirty form. This has to be done before try_to_unmap,
+ * because ttu takes the rmap data structures down.
+ *
+ * Error handling: We ignore errors here because
+ * there's nothing that can be done.
+ */
+ if (kill)
+ collect_procs(hpage, &tokill, flags & MF_ACTION_REQUIRED);
+
+ if (!PageHuge(hpage)) {
+ unmap_success = try_to_unmap(hpage, ttu);
+ } else {
+ if (!PageAnon(hpage)) {
+ /*
+ * For hugetlb pages in shared mappings, try_to_unmap
+ * could potentially call huge_pmd_unshare. Because of
+ * this, take semaphore in write mode here and set
+ * TTU_RMAP_LOCKED to indicate we have taken the lock
+ * at this higer level.
+ */
+ mapping = hugetlb_page_mapping_lock_write(hpage);
+ if (mapping) {
+ unmap_success = try_to_unmap(hpage,
+ ttu|TTU_RMAP_LOCKED);
+ i_mmap_unlock_write(mapping);
+ } else {
+ pr_info("Memory failure: %#lx: could not lock mapping for mapped huge page\n", pfn);
+ unmap_success = false;
+ }
+ } else {
+ unmap_success = try_to_unmap(p, ttu);
+ }
+ }
+ if (!unmap_success)
+ pr_err("Memory failure: %#lx: failed to unmap page (mapcount=%d)\n",
+ pfn, page_mapcount(p));
+
+ /*
+ * try_to_unmap() might put mlocked page in lru cache, so call
+ * shake_page() again to ensure that it's flushed.
+ */
+ if (mlocked)
+ shake_page(hpage, 0);
+
+ /*
+ * 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(hpage) || (flags & MF_MUST_KILL);
+ kill_procs(&tokill, forcekill, !unmap_success, pfn, flags);
+
+ return unmap_success;
+}
+
+static int identify_page_state(unsigned long pfn, struct page *p,
+ unsigned long page_flags)
+{
+ struct page_state *ps;
+
+ /*
+ * The first check uses the current page flags which may not have any
+ * relevant information. The second check with the saved page flags 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;
+ return page_action(ps, p, pfn);
+}
+
+static int try_to_split_thp_page(struct page *page, const char *msg)
+{
+ lock_page(page);
+ if (!PageAnon(page) || unlikely(split_huge_page(page))) {
+ unsigned long pfn = page_to_pfn(page);
+
+ unlock_page(page);
+ if (!PageAnon(page))
+ pr_info("%s: %#lx: non anonymous thp\n", msg, pfn);
+ else
+ pr_info("%s: %#lx: thp split failed\n", msg, pfn);
+ put_page(page);
+ return -EBUSY;
+ }
+ unlock_page(page);
+
+ return 0;
+}
+
+static int memory_failure_hugetlb(unsigned long pfn, int flags)
+{
+ struct page *p = pfn_to_page(pfn);
+ struct page *head = compound_head(p);
+ int res;
+ unsigned long page_flags;
+
+ if (TestSetPageHWPoison(head)) {
+ pr_err("Memory failure: %#lx: already hardware poisoned\n",
+ pfn);
+ return 0;
+ }
+
+ num_poisoned_pages_inc();
+
+ if (!(flags & MF_COUNT_INCREASED) && !get_hwpoison_page(p)) {
+ /*
+ * Check "filter hit" and "race with other subpage."
+ */
+ lock_page(head);
+ if (PageHWPoison(head)) {
+ if ((hwpoison_filter(p) && TestClearPageHWPoison(p))
+ || (p != head && TestSetPageHWPoison(head))) {
+ num_poisoned_pages_dec();
+ unlock_page(head);
+ return 0;
+ }
+ }
+ unlock_page(head);
+ dissolve_free_huge_page(p);
+ action_result(pfn, MF_MSG_FREE_HUGE, MF_DELAYED);
+ return 0;
+ }
+
+ lock_page(head);
+ page_flags = head->flags;
+
+ if (!PageHWPoison(head)) {
+ pr_err("Memory failure: %#lx: just unpoisoned\n", pfn);
+ num_poisoned_pages_dec();
+ unlock_page(head);
+ put_page(head);
+ return 0;
+ }
+
+ /*
+ * TODO: hwpoison for pud-sized hugetlb doesn't work right now, so
+ * simply disable it. In order to make it work properly, we need
+ * make sure that:
+ * - conversion of a pud that maps an error hugetlb into hwpoison
+ * entry properly works, and
+ * - other mm code walking over page table is aware of pud-aligned
+ * hwpoison entries.
+ */
+ if (huge_page_size(page_hstate(head)) > PMD_SIZE) {
+ action_result(pfn, MF_MSG_NON_PMD_HUGE, MF_IGNORED);
+ res = -EBUSY;
+ goto out;
+ }
+
+ if (!hwpoison_user_mappings(p, pfn, flags, &head)) {
+ action_result(pfn, MF_MSG_UNMAP_FAILED, MF_IGNORED);
+ res = -EBUSY;
+ goto out;
+ }
+
+ res = identify_page_state(pfn, p, page_flags);
+out:
+ unlock_page(head);
+ return res;
+}
+
+static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
+ struct dev_pagemap *pgmap)
+{
+ struct page *page = pfn_to_page(pfn);
+ const bool unmap_success = true;
+ unsigned long size = 0;
+ struct to_kill *tk;
+ LIST_HEAD(tokill);
+ int rc = -EBUSY;
+ loff_t start;
+ dax_entry_t cookie;
+
+ if (flags & MF_COUNT_INCREASED)
+ /*
+ * Drop the extra refcount in case we come from madvise().
+ */
+ put_page(page);
+
+ /* device metadata space is not recoverable */
+ if (!pgmap_pfn_valid(pgmap, pfn)) {
+ rc = -ENXIO;
+ goto out;
+ }
+
+ /*
+ * Prevent the inode from being freed while we are interrogating
+ * the address_space, typically this would be handled by
+ * lock_page(), but dax pages do not use the page lock. This
+ * also prevents changes to the mapping of this pfn until
+ * poison signaling is complete.
+ */
+ cookie = dax_lock_page(page);
+ if (!cookie)
+ goto out;
+
+ if (hwpoison_filter(page)) {
+ rc = 0;
+ goto unlock;
+ }
+
+ if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
+ /*
+ * TODO: Handle HMM pages which may need coordination
+ * with device-side memory.
+ */
+ goto unlock;
+ }
+
+ /*
+ * Use this flag as an indication that the dax page has been
+ * remapped UC to prevent speculative consumption of poison.
+ */
+ SetPageHWPoison(page);
+
+ /*
+ * Unlike System-RAM there is no possibility to swap in a
+ * different physical page at a given virtual address, so all
+ * userspace consumption of ZONE_DEVICE memory necessitates
+ * SIGBUS (i.e. MF_MUST_KILL)
+ */
+ flags |= MF_ACTION_REQUIRED | MF_MUST_KILL;
+ collect_procs(page, &tokill, flags & MF_ACTION_REQUIRED);
+
+ list_for_each_entry(tk, &tokill, nd)
+ if (tk->size_shift)
+ size = max(size, 1UL << tk->size_shift);
+ if (size) {
+ /*
+ * Unmap the largest mapping to avoid breaking up
+ * device-dax mappings which are constant size. The
+ * actual size of the mapping being torn down is
+ * communicated in siginfo, see kill_proc()
+ */
+ start = (page->index << PAGE_SHIFT) & ~(size - 1);
+ unmap_mapping_range(page->mapping, start, size, 0);
+ }
+ kill_procs(&tokill, flags & MF_MUST_KILL, !unmap_success, pfn, flags);
+ rc = 0;
+unlock:
+ dax_unlock_page(page, cookie);
+out:
+ /* drop pgmap ref acquired in caller */
+ put_dev_pagemap(pgmap);
+ action_result(pfn, MF_MSG_DAX, rc ? MF_FAILED : MF_RECOVERED);
+ return rc;
+}
+
+/**
+ * memory_failure - Handle memory failure of a page.
+ * @pfn: Page Number of the corrupted page
+ * @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 flags)
+{
+ struct page *p;
+ struct page *hpage;
+ struct page *orig_head;
+ struct dev_pagemap *pgmap;
+ int res;
+ unsigned long page_flags;
+
+ if (!sysctl_memory_failure_recovery)
+ panic("Memory failure on page %lx", pfn);
+
+ p = pfn_to_online_page(pfn);
+ if (!p) {
+ if (pfn_valid(pfn)) {
+ pgmap = get_dev_pagemap(pfn, NULL);
+ if (pgmap)
+ return memory_failure_dev_pagemap(pfn, flags,
+ pgmap);
+ }
+ pr_err("Memory failure: %#lx: memory outside kernel control\n",
+ pfn);
+ return -ENXIO;
+ }
+
+ if (PageHuge(p))
+ return memory_failure_hugetlb(pfn, flags);
+ if (TestSetPageHWPoison(p)) {
+ pr_err("Memory failure: %#lx: already hardware poisoned\n",
+ pfn);
+ return 0;
+ }
+
+ orig_head = hpage = compound_head(p);
+ num_poisoned_pages_inc();
+
+ /*
+ * We need/can do nothing about count=0 pages.
+ * 1) it's a free page, and therefore in safe hand:
+ * prep_new_page() will be the gate keeper.
+ * 2) it's part of a non-compound high order page.
+ * Implies some kernel user: cannot stop them from
+ * R/W the page; let's pray that the page has been
+ * used and will be freed some time later.
+ * In fact it's dangerous to directly bump up page count from 0,
+ * that may make page_ref_freeze()/page_ref_unfreeze() mismatch.
+ */
+ if (!(flags & MF_COUNT_INCREASED) && !get_hwpoison_page(p)) {
+ if (is_free_buddy_page(p)) {
+ action_result(pfn, MF_MSG_BUDDY, MF_DELAYED);
+ return 0;
+ } else {
+ action_result(pfn, MF_MSG_KERNEL_HIGH_ORDER, MF_IGNORED);
+ return -EBUSY;
+ }
+ }
+
+ if (PageTransHuge(hpage)) {
+ if (try_to_split_thp_page(p, "Memory Failure") < 0) {
+ action_result(pfn, MF_MSG_UNSPLIT_THP, MF_IGNORED);
+ return -EBUSY;
+ }
+ VM_BUG_ON_PAGE(!page_count(p), p);
+ }
+
+ /*
+ * 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 __SetPageLocked()
+ * - 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.
+ */
+ shake_page(p, 0);
+ /* shake_page could have turned it free. */
+ if (!PageLRU(p) && is_free_buddy_page(p)) {
+ if (flags & MF_COUNT_INCREASED)
+ action_result(pfn, MF_MSG_BUDDY, MF_DELAYED);
+ else
+ action_result(pfn, MF_MSG_BUDDY_2ND, MF_DELAYED);
+ return 0;
+ }
+
+ lock_page(p);
+
+ /*
+ * The page could have changed compound pages during the locking.
+ * If this happens just bail out.
+ */
+ if (PageCompound(p) && compound_head(p) != orig_head) {
+ action_result(pfn, MF_MSG_DIFFERENT_COMPOUND, MF_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)) {
+ pr_err("Memory failure: %#lx: just unpoisoned\n", pfn);
+ num_poisoned_pages_dec();
+ unlock_page(p);
+ put_page(p);
+ return 0;
+ }
+ if (hwpoison_filter(p)) {
+ if (TestClearPageHWPoison(p))
+ num_poisoned_pages_dec();
+ unlock_page(p);
+ put_page(p);
+ return 0;
+ }
+
+ /*
+ * __munlock_pagevec may clear a writeback page's LRU flag without
+ * page_lock. We need wait writeback completion for this page or it
+ * may trigger vfs BUG while evict inode.
+ */
+ if (!PageTransTail(p) && !PageLRU(p) && !PageWriteback(p))
+ goto identify_page_state;
+
+ /*
+ * 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.
+ */
+ if (!hwpoison_user_mappings(p, pfn, flags, &p)) {
+ action_result(pfn, MF_MSG_UNMAP_FAILED, MF_IGNORED);
+ res = -EBUSY;
+ goto out;
+ }
+
+ /*
+ * Torn down by someone else?
+ */
+ if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) {
+ action_result(pfn, MF_MSG_TRUNCATED_LRU, MF_IGNORED);
+ res = -EBUSY;
+ goto out;
+ }
+
+identify_page_state:
+ res = identify_page_state(pfn, p, page_flags);
+out:
+ unlock_page(p);
+ 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 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
+ * @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 flags)
+{
+ struct memory_failure_cpu *mf_cpu;
+ unsigned long proc_flags;
+ struct memory_failure_entry entry = {
+ .pfn = pfn,
+ .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 = container_of(work, struct memory_failure_cpu, work);
+ 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(entry.pfn, entry.flags);
+ else
+ memory_failure(entry.pfn, entry.flags);
+ }
+}
+
+/*
+ * Process memory_failure work queued on the specified CPU.
+ * Used to avoid return-to-userspace racing with the memory_failure workqueue.
+ */
+void memory_failure_queue_kick(int cpu)
+{
+ struct memory_failure_cpu *mf_cpu;
+
+ mf_cpu = &per_cpu(memory_failure_cpu, cpu);
+ cancel_work_sync(&mf_cpu->work);
+ memory_failure_work_func(&mf_cpu->work);
+}
+
+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);
+
+#define unpoison_pr_info(fmt, pfn, rs) \
+({ \
+ if (__ratelimit(rs)) \
+ pr_info(fmt, pfn); \
+})
+
+/**
+ * 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;
+ static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL,
+ DEFAULT_RATELIMIT_BURST);
+
+ if (!pfn_valid(pfn))
+ return -ENXIO;
+
+ p = pfn_to_page(pfn);
+ page = compound_head(p);
+
+ if (!PageHWPoison(p)) {
+ unpoison_pr_info("Unpoison: Page was already unpoisoned %#lx\n",
+ pfn, &unpoison_rs);
+ return 0;
+ }
+
+ if (page_count(page) > 1) {
+ unpoison_pr_info("Unpoison: Someone grabs the hwpoison page %#lx\n",
+ pfn, &unpoison_rs);
+ return 0;
+ }
+
+ if (page_mapped(page)) {
+ unpoison_pr_info("Unpoison: Someone maps the hwpoison page %#lx\n",
+ pfn, &unpoison_rs);
+ return 0;
+ }
+
+ if (page_mapping(page)) {
+ unpoison_pr_info("Unpoison: the hwpoison page has non-NULL mapping %#lx\n",
+ pfn, &unpoison_rs);
+ 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)) {
+ unpoison_pr_info("Unpoison: Memory failure is now running on %#lx\n",
+ pfn, &unpoison_rs);
+ return 0;
+ }
+
+ if (!get_hwpoison_page(p)) {
+ if (TestClearPageHWPoison(p))
+ num_poisoned_pages_dec();
+ unpoison_pr_info("Unpoison: Software-unpoisoned free page %#lx\n",
+ pfn, &unpoison_rs);
+ 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)) {
+ unpoison_pr_info("Unpoison: Software-unpoisoned page %#lx\n",
+ pfn, &unpoison_rs);
+ num_poisoned_pages_dec();
+ freeit = 1;
+ }
+ 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);
+
+/*
+ * Safely get reference count of an arbitrary page.
+ * Returns 0 for a free page, 1 for an in-use page, -EIO for a page-type we
+ * cannot handle and -EBUSY if we raced with an allocation.
+ * We only incremented refcount in case the page was already in-use and it is
+ * a known type we can handle.
+ */
+static int get_any_page(struct page *p, int flags)
+{
+ int ret = 0, pass = 0;
+ bool count_increased = false;
+
+ if (flags & MF_COUNT_INCREASED)
+ count_increased = true;
+
+try_again:
+ if (!count_increased && !get_hwpoison_page(p)) {
+ if (page_count(p)) {
+ /* We raced with an allocation, retry. */
+ if (pass++ < 3)
+ goto try_again;
+ ret = -EBUSY;
+ } else if (!PageHuge(p) && !is_free_buddy_page(p)) {
+ /* We raced with put_page, retry. */
+ if (pass++ < 3)
+ goto try_again;
+ ret = -EIO;
+ }
+ } else {
+ if (PageHuge(p) || PageLRU(p) || __PageMovable(p)) {
+ ret = 1;
+ } else {
+ /*
+ * A page we cannot handle. Check whether we can turn
+ * it into something we can handle.
+ */
+ if (pass++ < 3) {
+ put_page(p);
+ shake_page(p, 1);
+ count_increased = false;
+ goto try_again;
+ }
+ put_page(p);
+ ret = -EIO;
+ }
+ }
+
+ return ret;
+}
+
+static bool isolate_page(struct page *page, struct list_head *pagelist)
+{
+ bool isolated = false;
+ bool lru = PageLRU(page);
+
+ if (PageHuge(page)) {
+ isolated = !isolate_hugetlb(page, pagelist);
+ } else {
+ if (lru)
+ isolated = !isolate_lru_page(page);
+ else
+ isolated = !isolate_movable_page(page, ISOLATE_UNEVICTABLE);
+
+ if (isolated)
+ list_add(&page->lru, pagelist);
+ }
+
+ if (isolated && lru)
+ inc_node_page_state(page, NR_ISOLATED_ANON +
+ page_is_file_lru(page));
+
+ /*
+ * If we succeed to isolate the page, we grabbed another refcount on
+ * the page, so we can safely drop the one we got from get_any_pages().
+ * If we failed to isolate the page, it means that we cannot go further
+ * and we will return an error, so drop the reference we got from
+ * get_any_pages() as well.
+ */
+ put_page(page);
+ return isolated;
+}
+
+/*
+ * __soft_offline_page handles hugetlb-pages and non-hugetlb pages.
+ * If the page is a non-dirty unmapped page-cache page, it simply invalidates.
+ * If the page is mapped, it migrates the contents over.
+ */
+static int __soft_offline_page(struct page *page)
+{
+ int ret = 0;
+ unsigned long pfn = page_to_pfn(page);
+ struct page *hpage = compound_head(page);
+ char const *msg_page[] = {"page", "hugepage"};
+ bool huge = PageHuge(page);
+ LIST_HEAD(pagelist);
+ struct migration_target_control mtc = {
+ .nid = NUMA_NO_NODE,
+ .gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL,
+ };
+
+ /*
+ * 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);
+ if (!PageHuge(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 0;
+ }
+
+ if (!PageHuge(page))
+ /*
+ * 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) {
+ pr_info("soft_offline: %#lx: invalidated\n", pfn);
+ page_handle_poison(page, false, true);
+ return 0;
+ }
+
+ if (isolate_page(hpage, &pagelist)) {
+ ret = migrate_pages(&pagelist, alloc_migration_target, NULL,
+ (unsigned long)&mtc, MIGRATE_SYNC, MR_MEMORY_FAILURE);
+ if (!ret) {
+ bool release = !huge;
+
+ if (!page_handle_poison(page, huge, release))
+ ret = -EBUSY;
+ } else {
+ if (!list_empty(&pagelist))
+ putback_movable_pages(&pagelist);
+
+ pr_info("soft offline: %#lx: %s migration failed %d, type %lx (%pGp)\n",
+ pfn, msg_page[huge], ret, page->flags, &page->flags);
+ if (ret > 0)
+ ret = -EBUSY;
+ }
+ } else {
+ pr_info("soft offline: %#lx: %s isolation failed, page count %d, type %lx (%pGp)\n",
+ pfn, msg_page[huge], page_count(page), page->flags, &page->flags);
+ ret = -EBUSY;
+ }
+ return ret;
+}
+
+static int soft_offline_in_use_page(struct page *page)
+{
+ struct page *hpage = compound_head(page);
+
+ if (!PageHuge(page) && PageTransHuge(hpage))
+ if (try_to_split_thp_page(page, "soft offline") < 0)
+ return -EBUSY;
+ return __soft_offline_page(page);
+}
+
+static void put_ref_page(struct page *page)
+{
+ if (page)
+ put_page(page);
+}
+
+/**
+ * soft_offline_page - Soft offline a page.
+ * @pfn: pfn to soft-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(unsigned long pfn, int flags)
+{
+ int ret;
+ bool try_again = true;
+ struct page *page, *ref_page = NULL;
+
+ WARN_ON_ONCE(!pfn_valid(pfn) && (flags & MF_COUNT_INCREASED));
+
+ if (!pfn_valid(pfn))
+ return -ENXIO;
+ if (flags & MF_COUNT_INCREASED)
+ ref_page = pfn_to_page(pfn);
+
+ /* Only online pages can be soft-offlined (esp., not ZONE_DEVICE). */
+ page = pfn_to_online_page(pfn);
+ if (!page) {
+ put_ref_page(ref_page);
+ return -EIO;
+ }
+
+ if (PageHWPoison(page)) {
+ pr_info("%s: %#lx page already poisoned\n", __func__, pfn);
+ put_ref_page(ref_page);
+ return 0;
+ }
+
+retry:
+ get_online_mems();
+ ret = get_any_page(page, flags);
+ put_online_mems();
+
+ if (ret > 0) {
+ ret = soft_offline_in_use_page(page);
+ } else if (ret == 0) {
+ if (!page_handle_poison(page, true, false)) {
+ if (try_again) {
+ try_again = false;
+ flags &= ~MF_COUNT_INCREASED;
+ goto retry;
+ }
+ ret = -EBUSY;
+ }
+ } else if (ret == -EIO) {
+ pr_info("%s: %#lx: unknown page type: %lx (%pGp)\n",
+ __func__, pfn, page->flags, &page->flags);
+ }
+
+ return ret;
+}