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Diffstat (limited to '')
| -rw-r--r-- | mm/memory-failure.c | 2793 |
1 files changed, 2793 insertions, 0 deletions
diff --git a/mm/memory-failure.c b/mm/memory-failure.c new file mode 100644 index 0000000000..455093f73a --- /dev/null +++ b/mm/memory-failure.c @@ -0,0 +1,2793 @@ +// 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/mm/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. + */ + +#define pr_fmt(fmt) "Memory failure: " fmt + +#include <linux/kernel.h> +#include <linux/mm.h> +#include <linux/page-flags.h> +#include <linux/sched/signal.h> +#include <linux/sched/task.h> +#include <linux/dax.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/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/pagewalk.h> +#include <linux/shmem_fs.h> +#include <linux/sysctl.h> +#include "swap.h" +#include "internal.h" +#include "ras/ras_event.h" + +static int sysctl_memory_failure_early_kill __read_mostly; + +static int sysctl_memory_failure_recovery __read_mostly = 1; + +atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0); + +static bool hw_memory_failure __read_mostly = false; + +static DEFINE_MUTEX(mf_mutex); + +void num_poisoned_pages_inc(unsigned long pfn) +{ + atomic_long_inc(&num_poisoned_pages); + memblk_nr_poison_inc(pfn); +} + +void num_poisoned_pages_sub(unsigned long pfn, long i) +{ + atomic_long_sub(i, &num_poisoned_pages); + if (pfn != -1UL) + memblk_nr_poison_sub(pfn, i); +} + +/** + * MF_ATTR_RO - Create sysfs entry for each memory failure statistics. + * @_name: name of the file in the per NUMA sysfs directory. + */ +#define MF_ATTR_RO(_name) \ +static ssize_t _name##_show(struct device *dev, \ + struct device_attribute *attr, \ + char *buf) \ +{ \ + struct memory_failure_stats *mf_stats = \ + &NODE_DATA(dev->id)->mf_stats; \ + return sprintf(buf, "%lu\n", mf_stats->_name); \ +} \ +static DEVICE_ATTR_RO(_name) + +MF_ATTR_RO(total); +MF_ATTR_RO(ignored); +MF_ATTR_RO(failed); +MF_ATTR_RO(delayed); +MF_ATTR_RO(recovered); + +static struct attribute *memory_failure_attr[] = { + &dev_attr_total.attr, + &dev_attr_ignored.attr, + &dev_attr_failed.attr, + &dev_attr_delayed.attr, + &dev_attr_recovered.attr, + NULL, +}; + +const struct attribute_group memory_failure_attr_group = { + .name = "memory_failure", + .attrs = memory_failure_attr, +}; + +static struct ctl_table memory_failure_table[] = { + { + .procname = "memory_failure_early_kill", + .data = &sysctl_memory_failure_early_kill, + .maxlen = sizeof(sysctl_memory_failure_early_kill), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_ONE, + }, + { + .procname = "memory_failure_recovery", + .data = &sysctl_memory_failure_recovery, + .maxlen = sizeof(sysctl_memory_failure_recovery), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_ONE, + }, + { } +}; + +/* + * Return values: + * 1: the page is dissolved (if needed) and taken off from buddy, + * 0: the page is dissolved (if needed) and not taken off from buddy, + * < 0: failed to dissolve. + */ +static int __page_handle_poison(struct page *page) +{ + int ret; + + zone_pcp_disable(page_zone(page)); + ret = dissolve_free_huge_page(page); + if (!ret) + ret = take_page_off_buddy(page); + zone_pcp_enable(page_zone(page)); + + return ret; +} + +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 (__page_handle_poison(page) <= 0) + /* + * We could fail to take off the target page from buddy + * for example due to racy page allocation, 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(page_to_pfn(page)); + + return true; +} + +#if IS_ENABLED(CONFIG_HWPOISON_INJECT) + +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; + + 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("%#lx: Sending SIGBUS to %s:%d due to hardware memory corruption\n", + pfn, t->comm, t->pid); + + if ((flags & MF_ACTION_REQUIRED) && (t == current)) + ret = force_sig_mceerr(BUS_MCEERR_AR, + (void __user *)tk->addr, addr_lsb); + else + /* + * Signal other processes sharing the page if they have + * PF_MCE_EARLY set. + * 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); + if (ret < 0) + pr_info("Error sending signal to %s:%d: %d\n", + t->comm, t->pid, ret); + return ret; +} + +/* + * Unknown page type encountered. Try to check whether it can turn PageLRU by + * lru_add_drain_all. + */ +void shake_page(struct page *p) +{ + if (PageHuge(p)) + return; + /* + * TODO: Could shrink slab caches here if a lightweight range-based + * shrinker will be available. + */ + if (PageSlab(p)) + return; + + lru_add_drain_all(); +} +EXPORT_SYMBOL_GPL(shake_page); + +static unsigned long dev_pagemap_mapping_shift(struct vm_area_struct *vma, + unsigned long address) +{ + unsigned long ret = 0; + pgd_t *pgd; + p4d_t *p4d; + pud_t *pud; + pmd_t *pmd; + pte_t *pte; + pte_t ptent; + + VM_BUG_ON_VMA(address == -EFAULT, vma); + 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) + return 0; + ptent = ptep_get(pte); + if (pte_present(ptent) && pte_devmap(ptent)) + ret = PAGE_SHIFT; + pte_unmap(pte); + return ret; +} + +/* + * 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. + */ + +#define FSDAX_INVALID_PGOFF ULONG_MAX + +/* + * Schedule a process for later kill. + * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM. + * + * Note: @fsdax_pgoff is used only when @p is a fsdax page and a + * filesystem with a memory failure handler has claimed the + * memory_failure event. In all other cases, page->index and + * page->mapping are sufficient for mapping the page back to its + * corresponding user virtual address. + */ +static void __add_to_kill(struct task_struct *tsk, struct page *p, + struct vm_area_struct *vma, struct list_head *to_kill, + unsigned long ksm_addr, pgoff_t fsdax_pgoff) +{ + struct to_kill *tk; + + tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC); + if (!tk) { + pr_err("Out of memory while machine check handling\n"); + return; + } + + tk->addr = ksm_addr ? ksm_addr : page_address_in_vma(p, vma); + if (is_zone_device_page(p)) { + if (fsdax_pgoff != FSDAX_INVALID_PGOFF) + tk->addr = vma_pgoff_address(fsdax_pgoff, 1, vma); + tk->size_shift = dev_pagemap_mapping_shift(vma, tk->addr); + } 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("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); +} + +static void add_to_kill_anon_file(struct task_struct *tsk, struct page *p, + struct vm_area_struct *vma, + struct list_head *to_kill) +{ + __add_to_kill(tsk, p, vma, to_kill, 0, FSDAX_INVALID_PGOFF); +} + +#ifdef CONFIG_KSM +static bool task_in_to_kill_list(struct list_head *to_kill, + struct task_struct *tsk) +{ + struct to_kill *tk, *next; + + list_for_each_entry_safe(tk, next, to_kill, nd) { + if (tk->tsk == tsk) + return true; + } + + return false; +} +void add_to_kill_ksm(struct task_struct *tsk, struct page *p, + struct vm_area_struct *vma, struct list_head *to_kill, + unsigned long ksm_addr) +{ + if (!task_in_to_kill_list(to_kill, tsk)) + __add_to_kill(tsk, p, vma, to_kill, ksm_addr, FSDAX_INVALID_PGOFF); +} +#endif +/* + * Kill the processes that have been collected earlier. + * + * Only do anything when FORCEKILL 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("%#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("%#lx: Cannot send advisory machine check signal to %s:%d\n", + pfn, tk->tsk->comm, tk->tsk->pid); + } + list_del(&tk->nd); + 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 rcu 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. For Action Required + * case, it's only meaningful to the current thread which need to be signaled + * with SIGBUS, this error is Action Optional for other non current + * processes sharing the same error page,if the process is "early kill", the + * task_struct of the dedicated thread will also be returned. + */ +struct task_struct *task_early_kill(struct task_struct *tsk, int force_early) +{ + if (!tsk->mm) + return NULL; + /* + * Comparing ->mm here because current task might represent + * a subthread, while tsk always points to the main thread. + */ + if (force_early && tsk->mm == current->mm) + return current; + + return find_early_kill_thread(tsk); +} + +/* + * Collect processes when the error hit an anonymous page. + */ +static void collect_procs_anon(struct folio *folio, 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 = folio_lock_anon_vma_read(folio, NULL); + if (av == NULL) /* Not actually mapped anymore */ + return; + + pgoff = page_to_pgoff(page); + rcu_read_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 (vma->vm_mm != t->mm) + continue; + if (!page_mapped_in_vma(page, vma)) + continue; + add_to_kill_anon_file(t, page, vma, to_kill); + } + } + rcu_read_unlock(); + anon_vma_unlock_read(av); +} + +/* + * Collect processes when the error hit a file mapped page. + */ +static void collect_procs_file(struct folio *folio, struct page *page, + struct list_head *to_kill, int force_early) +{ + struct vm_area_struct *vma; + struct task_struct *tsk; + struct address_space *mapping = folio->mapping; + pgoff_t pgoff; + + i_mmap_lock_read(mapping); + rcu_read_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 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_anon_file(t, page, vma, to_kill); + } + } + rcu_read_unlock(); + i_mmap_unlock_read(mapping); +} + +#ifdef CONFIG_FS_DAX +static void add_to_kill_fsdax(struct task_struct *tsk, struct page *p, + struct vm_area_struct *vma, + struct list_head *to_kill, pgoff_t pgoff) +{ + __add_to_kill(tsk, p, vma, to_kill, 0, pgoff); +} + +/* + * Collect processes when the error hit a fsdax page. + */ +static void collect_procs_fsdax(struct page *page, + struct address_space *mapping, pgoff_t pgoff, + struct list_head *to_kill) +{ + struct vm_area_struct *vma; + struct task_struct *tsk; + + i_mmap_lock_read(mapping); + rcu_read_lock(); + for_each_process(tsk) { + struct task_struct *t = task_early_kill(tsk, true); + + if (!t) + continue; + vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) { + if (vma->vm_mm == t->mm) + add_to_kill_fsdax(t, page, vma, to_kill, pgoff); + } + } + rcu_read_unlock(); + i_mmap_unlock_read(mapping); +} +#endif /* CONFIG_FS_DAX */ + +/* + * Collect the processes who have the corrupted page mapped to kill. + */ +static void collect_procs(struct folio *folio, struct page *page, + struct list_head *tokill, int force_early) +{ + if (!folio->mapping) + return; + if (unlikely(PageKsm(page))) + collect_procs_ksm(page, tokill, force_early); + else if (PageAnon(page)) + collect_procs_anon(folio, page, tokill, force_early); + else + collect_procs_file(folio, page, tokill, force_early); +} + +struct hwpoison_walk { + struct to_kill tk; + unsigned long pfn; + int flags; +}; + +static void set_to_kill(struct to_kill *tk, unsigned long addr, short shift) +{ + tk->addr = addr; + tk->size_shift = shift; +} + +static int check_hwpoisoned_entry(pte_t pte, unsigned long addr, short shift, + unsigned long poisoned_pfn, struct to_kill *tk) +{ + unsigned long pfn = 0; + + if (pte_present(pte)) { + pfn = pte_pfn(pte); + } else { + swp_entry_t swp = pte_to_swp_entry(pte); + + if (is_hwpoison_entry(swp)) + pfn = swp_offset_pfn(swp); + } + + if (!pfn || pfn != poisoned_pfn) + return 0; + + set_to_kill(tk, addr, shift); + return 1; +} + +#ifdef CONFIG_TRANSPARENT_HUGEPAGE +static int check_hwpoisoned_pmd_entry(pmd_t *pmdp, unsigned long addr, + struct hwpoison_walk *hwp) +{ + pmd_t pmd = *pmdp; + unsigned long pfn; + unsigned long hwpoison_vaddr; + + if (!pmd_present(pmd)) + return 0; + pfn = pmd_pfn(pmd); + if (pfn <= hwp->pfn && hwp->pfn < pfn + HPAGE_PMD_NR) { + hwpoison_vaddr = addr + ((hwp->pfn - pfn) << PAGE_SHIFT); + set_to_kill(&hwp->tk, hwpoison_vaddr, PAGE_SHIFT); + return 1; + } + return 0; +} +#else +static int check_hwpoisoned_pmd_entry(pmd_t *pmdp, unsigned long addr, + struct hwpoison_walk *hwp) +{ + return 0; +} +#endif + +static int hwpoison_pte_range(pmd_t *pmdp, unsigned long addr, + unsigned long end, struct mm_walk *walk) +{ + struct hwpoison_walk *hwp = walk->private; + int ret = 0; + pte_t *ptep, *mapped_pte; + spinlock_t *ptl; + + ptl = pmd_trans_huge_lock(pmdp, walk->vma); + if (ptl) { + ret = check_hwpoisoned_pmd_entry(pmdp, addr, hwp); + spin_unlock(ptl); + goto out; + } + + mapped_pte = ptep = pte_offset_map_lock(walk->vma->vm_mm, pmdp, + addr, &ptl); + if (!ptep) + goto out; + + for (; addr != end; ptep++, addr += PAGE_SIZE) { + ret = check_hwpoisoned_entry(ptep_get(ptep), addr, PAGE_SHIFT, + hwp->pfn, &hwp->tk); + if (ret == 1) + break; + } + pte_unmap_unlock(mapped_pte, ptl); +out: + cond_resched(); + return ret; +} + +#ifdef CONFIG_HUGETLB_PAGE +static int hwpoison_hugetlb_range(pte_t *ptep, unsigned long hmask, + unsigned long addr, unsigned long end, + struct mm_walk *walk) +{ + struct hwpoison_walk *hwp = walk->private; + pte_t pte = huge_ptep_get(ptep); + struct hstate *h = hstate_vma(walk->vma); + + return check_hwpoisoned_entry(pte, addr, huge_page_shift(h), + hwp->pfn, &hwp->tk); +} +#else +#define hwpoison_hugetlb_range NULL +#endif + +static const struct mm_walk_ops hwpoison_walk_ops = { + .pmd_entry = hwpoison_pte_range, + .hugetlb_entry = hwpoison_hugetlb_range, + .walk_lock = PGWALK_RDLOCK, +}; + +/* + * Sends SIGBUS to the current process with error info. + * + * This function is intended to handle "Action Required" MCEs on already + * hardware poisoned pages. They could happen, for example, when + * memory_failure() failed to unmap the error page at the first call, or + * when multiple local machine checks happened on different CPUs. + * + * MCE handler currently has no easy access to the error virtual address, + * so this function walks page table to find it. The returned virtual address + * is proper in most cases, but it could be wrong when the application + * process has multiple entries mapping the error page. + */ +static int kill_accessing_process(struct task_struct *p, unsigned long pfn, + int flags) +{ + int ret; + struct hwpoison_walk priv = { + .pfn = pfn, + }; + priv.tk.tsk = p; + + if (!p->mm) + return -EFAULT; + + mmap_read_lock(p->mm); + ret = walk_page_range(p->mm, 0, TASK_SIZE, &hwpoison_walk_ops, + (void *)&priv); + if (ret == 1 && priv.tk.addr) + kill_proc(&priv.tk, pfn, flags); + else + ret = 0; + mmap_read_unlock(p->mm); + return ret > 0 ? -EHWPOISON : -EFAULT; +} + +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_HUGE] = "huge page", + [MF_MSG_FREE_HUGE] = "free 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_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(page_folio(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) { + struct folio *folio = page_folio(p); + int err = mapping->a_ops->error_remove_page(mapping, p); + + if (err != 0) + pr_info("%#lx: Failed to punch page: %d\n", pfn, err); + else if (!filemap_release_folio(folio, GFP_NOIO)) + pr_info("%#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("%#lx: Failed to invalidate\n", pfn); + } + + return ret; +} + +struct page_state { + unsigned long mask; + unsigned long res; + enum mf_action_page_type type; + + /* Callback ->action() has to unlock the relevant page inside it. */ + int (*action)(struct page_state *ps, struct page *p); +}; + +/* + * Return true if page is still referenced by others, otherwise return + * false. + * + * The extra_pins is true when one extra refcount is expected. + */ +static bool has_extra_refcount(struct page_state *ps, struct page *p, + bool extra_pins) +{ + int count = page_count(p) - 1; + + if (extra_pins) + count -= 1; + + if (count > 0) { + pr_err("%#lx: %s still referenced by %d users\n", + page_to_pfn(p), action_page_types[ps->type], count); + return true; + } + + return false; +} + +/* + * 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_state *ps, struct page *p) +{ + unlock_page(p); + return MF_IGNORED; +} + +/* + * Page in unknown state. Do nothing. + */ +static int me_unknown(struct page_state *ps, struct page *p) +{ + pr_err("%#lx: Unknown page state\n", page_to_pfn(p)); + unlock_page(p); + return MF_FAILED; +} + +/* + * Clean (or cleaned) page cache page. + */ +static int me_pagecache_clean(struct page_state *ps, struct page *p) +{ + int ret; + struct address_space *mapping; + bool extra_pins; + + 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)) { + ret = MF_RECOVERED; + goto out; + } + + /* + * 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 + */ + ret = MF_FAILED; + goto out; + } + + /* + * The shmem page is kept in page cache instead of truncating + * so is expected to have an extra refcount after error-handling. + */ + extra_pins = shmem_mapping(mapping); + + /* + * Truncation is a bit tricky. Enable it per file system for now. + * + * Open: to take i_rwsem or not for this? Right now we don't. + */ + ret = truncate_error_page(p, page_to_pfn(p), mapping); + if (has_extra_refcount(ps, p, extra_pins)) + ret = MF_FAILED; + +out: + unlock_page(p); + + 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_state *ps, struct page *p) +{ + 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(ps, p); +} + +/* + * 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_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_state *ps, struct page *p) +{ + int ret; + bool extra_pins = false; + + ClearPageDirty(p); + /* Trigger EIO in shmem: */ + ClearPageUptodate(p); + + ret = delete_from_lru_cache(p) ? MF_FAILED : MF_DELAYED; + unlock_page(p); + + if (ret == MF_DELAYED) + extra_pins = true; + + if (has_extra_refcount(ps, p, extra_pins)) + ret = MF_FAILED; + + return ret; +} + +static int me_swapcache_clean(struct page_state *ps, struct page *p) +{ + struct folio *folio = page_folio(p); + int ret; + + delete_from_swap_cache(folio); + + ret = delete_from_lru_cache(p) ? MF_FAILED : MF_RECOVERED; + folio_unlock(folio); + + if (has_extra_refcount(ps, p, false)) + ret = MF_FAILED; + + return ret; +} + +/* + * 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_state *ps, struct page *p) +{ + int res; + struct page *hpage = compound_head(p); + struct address_space *mapping; + bool extra_pins = false; + + mapping = page_mapping(hpage); + if (mapping) { + res = truncate_error_page(hpage, page_to_pfn(p), mapping); + /* The page is kept in page cache. */ + extra_pins = true; + unlock_page(hpage); + } else { + unlock_page(hpage); + /* + * migration entry prevents later access on error hugepage, + * so we can free and dissolve it into buddy to save healthy + * subpages. + */ + put_page(hpage); + if (__page_handle_poison(p) >= 0) { + page_ref_inc(p); + res = MF_RECOVERED; + } else { + res = MF_FAILED; + } + } + + if (has_extra_refcount(ps, p, extra_pins)) + res = MF_FAILED; + + 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 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 + +static void update_per_node_mf_stats(unsigned long pfn, + enum mf_result result) +{ + int nid = MAX_NUMNODES; + struct memory_failure_stats *mf_stats = NULL; + + nid = pfn_to_nid(pfn); + if (unlikely(nid < 0 || nid >= MAX_NUMNODES)) { + WARN_ONCE(1, "Memory failure: pfn=%#lx, invalid nid=%d", pfn, nid); + return; + } + + mf_stats = &NODE_DATA(nid)->mf_stats; + switch (result) { + case MF_IGNORED: + ++mf_stats->ignored; + break; + case MF_FAILED: + ++mf_stats->failed; + break; + case MF_DELAYED: + ++mf_stats->delayed; + break; + case MF_RECOVERED: + ++mf_stats->recovered; + break; + default: + WARN_ONCE(1, "Memory failure: mf_result=%d is not properly handled", result); + break; + } + ++mf_stats->total; +} + +/* + * "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 int action_result(unsigned long pfn, enum mf_action_page_type type, + enum mf_result result) +{ + trace_memory_failure_event(pfn, type, result); + + num_poisoned_pages_inc(pfn); + + update_per_node_mf_stats(pfn, result); + + pr_err("%#lx: recovery action for %s: %s\n", + pfn, action_page_types[type], action_name[result]); + + return (result == MF_RECOVERED || result == MF_DELAYED) ? 0 : -EBUSY; +} + +static int page_action(struct page_state *ps, struct page *p, + unsigned long pfn) +{ + int result; + + /* page p should be unlocked after returning from ps->action(). */ + result = ps->action(ps, p); + + /* Could do more checks here if page looks ok */ + /* + * Could adjust zone counters here to correct for the missing page. + */ + + return action_result(pfn, ps->type, result); +} + +static inline bool PageHWPoisonTakenOff(struct page *page) +{ + return PageHWPoison(page) && page_private(page) == MAGIC_HWPOISON; +} + +void SetPageHWPoisonTakenOff(struct page *page) +{ + set_page_private(page, MAGIC_HWPOISON); +} + +void ClearPageHWPoisonTakenOff(struct page *page) +{ + if (PageHWPoison(page)) + set_page_private(page, 0); +} + +/* + * Return true if a page type of a given page is supported by hwpoison + * mechanism (while handling could fail), otherwise false. This function + * does not return true for hugetlb or device memory pages, so it's assumed + * to be called only in the context where we never have such pages. + */ +static inline bool HWPoisonHandlable(struct page *page, unsigned long flags) +{ + /* Soft offline could migrate non-LRU movable pages */ + if ((flags & MF_SOFT_OFFLINE) && __PageMovable(page)) + return true; + + return PageLRU(page) || is_free_buddy_page(page); +} + +static int __get_hwpoison_page(struct page *page, unsigned long flags) +{ + struct folio *folio = page_folio(page); + int ret = 0; + bool hugetlb = false; + + ret = get_hwpoison_hugetlb_folio(folio, &hugetlb, false); + if (hugetlb) { + /* Make sure hugetlb demotion did not happen from under us. */ + if (folio == page_folio(page)) + return ret; + if (ret > 0) { + folio_put(folio); + folio = page_folio(page); + } + } + + /* + * This check prevents from calling folio_try_get() for any + * unsupported type of folio in order to reduce the risk of unexpected + * races caused by taking a folio refcount. + */ + if (!HWPoisonHandlable(&folio->page, flags)) + return -EBUSY; + + if (folio_try_get(folio)) { + if (folio == page_folio(page)) + return 1; + + pr_info("%#lx cannot catch tail\n", page_to_pfn(page)); + folio_put(folio); + } + + return 0; +} + +static int get_any_page(struct page *p, unsigned long flags) +{ + int ret = 0, pass = 0; + bool count_increased = false; + + if (flags & MF_COUNT_INCREASED) + count_increased = true; + +try_again: + if (!count_increased) { + ret = __get_hwpoison_page(p, flags); + if (!ret) { + 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; + } + goto out; + } else if (ret == -EBUSY) { + /* + * We raced with (possibly temporary) unhandlable + * page, retry. + */ + if (pass++ < 3) { + shake_page(p); + goto try_again; + } + ret = -EIO; + goto out; + } + } + + if (PageHuge(p) || HWPoisonHandlable(p, flags)) { + 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); + count_increased = false; + goto try_again; + } + put_page(p); + ret = -EIO; + } +out: + if (ret == -EIO) + pr_err("%#lx: unhandlable page.\n", page_to_pfn(p)); + + return ret; +} + +static int __get_unpoison_page(struct page *page) +{ + struct folio *folio = page_folio(page); + int ret = 0; + bool hugetlb = false; + + ret = get_hwpoison_hugetlb_folio(folio, &hugetlb, true); + if (hugetlb) { + /* Make sure hugetlb demotion did not happen from under us. */ + if (folio == page_folio(page)) + return ret; + if (ret > 0) + folio_put(folio); + } + + /* + * PageHWPoisonTakenOff pages are not only marked as PG_hwpoison, + * but also isolated from buddy freelist, so need to identify the + * state and have to cancel both operations to unpoison. + */ + if (PageHWPoisonTakenOff(page)) + return -EHWPOISON; + + return get_page_unless_zero(page) ? 1 : 0; +} + +/** + * get_hwpoison_page() - Get refcount for memory error handling + * @p: Raw error page (hit by memory error) + * @flags: Flags controlling behavior of error handling + * + * get_hwpoison_page() takes a page refcount of an error page to handle memory + * error on it, after checking that the error page is in a well-defined state + * (defined as a page-type we can successfully handle the memory error on it, + * such as LRU page and hugetlb page). + * + * Memory error handling could be triggered at any time on any type of page, + * so it's prone to race with typical memory management lifecycle (like + * allocation and free). So to avoid such races, get_hwpoison_page() takes + * extra care for the error page's state (as done in __get_hwpoison_page()), + * and has some retry logic in get_any_page(). + * + * When called from unpoison_memory(), the caller should already ensure that + * the given page has PG_hwpoison. So it's never reused for other page + * allocations, and __get_unpoison_page() never races with them. + * + * Return: 0 on failure, + * 1 on success for in-use pages in a well-defined state, + * -EIO for pages on which we can not handle memory errors, + * -EBUSY when get_hwpoison_page() has raced with page lifecycle + * operations like allocation and free, + * -EHWPOISON when the page is hwpoisoned and taken off from buddy. + */ +static int get_hwpoison_page(struct page *p, unsigned long flags) +{ + int ret; + + zone_pcp_disable(page_zone(p)); + if (flags & MF_UNPOISON) + ret = __get_unpoison_page(p); + else + ret = get_any_page(p, flags); + zone_pcp_enable(page_zone(p)); + + return ret; +} + +/* + * 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 *hpage) +{ + struct folio *folio = page_folio(hpage); + enum ttu_flags ttu = TTU_IGNORE_MLOCK | TTU_SYNC | TTU_HWPOISON; + struct address_space *mapping; + LIST_HEAD(tokill); + bool unmap_success; + int forcekill; + 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) || PageTable(p) || PageOffline(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 (PageSwapCache(p)) { + pr_err("%#lx: keeping poisoned page in swap cache\n", pfn); + ttu &= ~TTU_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 { + ttu &= ~TTU_HWPOISON; + pr_info("%#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. + */ + collect_procs(folio, p, &tokill, flags & MF_ACTION_REQUIRED); + + if (PageHuge(hpage) && !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 higher level. + */ + mapping = hugetlb_page_mapping_lock_write(hpage); + if (mapping) { + try_to_unmap(folio, ttu|TTU_RMAP_LOCKED); + i_mmap_unlock_write(mapping); + } else + pr_info("%#lx: could not lock mapping for mapped huge page\n", pfn); + } else { + try_to_unmap(folio, ttu); + } + + unmap_success = !page_mapped(p); + if (!unmap_success) + pr_err("%#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); + + /* + * 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) || + !unmap_success; + 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) +{ + int ret; + + lock_page(page); + ret = split_huge_page(page); + unlock_page(page); + + if (unlikely(ret)) + put_page(page); + + return ret; +} + +static void unmap_and_kill(struct list_head *to_kill, unsigned long pfn, + struct address_space *mapping, pgoff_t index, int flags) +{ + struct to_kill *tk; + unsigned long size = 0; + + list_for_each_entry(tk, to_kill, 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() + */ + loff_t start = ((loff_t)index << PAGE_SHIFT) & ~(size - 1); + + unmap_mapping_range(mapping, start, size, 0); + } + + kill_procs(to_kill, flags & MF_MUST_KILL, false, pfn, flags); +} + +/* + * Only dev_pagemap pages get here, such as fsdax when the filesystem + * either do not claim or fails to claim a hwpoison event, or devdax. + * The fsdax pages are initialized per base page, and the devdax pages + * could be initialized either as base pages, or as compound pages with + * vmemmap optimization enabled. Devdax is simplistic in its dealing with + * hwpoison, such that, if a subpage of a compound page is poisoned, + * simply mark the compound head page is by far sufficient. + */ +static int mf_generic_kill_procs(unsigned long long pfn, int flags, + struct dev_pagemap *pgmap) +{ + struct folio *folio = pfn_folio(pfn); + LIST_HEAD(to_kill); + dax_entry_t cookie; + int rc = 0; + + /* + * 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_folio(folio); + if (!cookie) + return -EBUSY; + + if (hwpoison_filter(&folio->page)) { + rc = -EOPNOTSUPP; + goto unlock; + } + + switch (pgmap->type) { + case MEMORY_DEVICE_PRIVATE: + case MEMORY_DEVICE_COHERENT: + /* + * TODO: Handle device pages which may need coordination + * with device-side memory. + */ + rc = -ENXIO; + goto unlock; + default: + break; + } + + /* + * Use this flag as an indication that the dax page has been + * remapped UC to prevent speculative consumption of poison. + */ + SetPageHWPoison(&folio->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(folio, &folio->page, &to_kill, true); + + unmap_and_kill(&to_kill, pfn, folio->mapping, folio->index, flags); +unlock: + dax_unlock_folio(folio, cookie); + return rc; +} + +#ifdef CONFIG_FS_DAX +/** + * mf_dax_kill_procs - Collect and kill processes who are using this file range + * @mapping: address_space of the file in use + * @index: start pgoff of the range within the file + * @count: length of the range, in unit of PAGE_SIZE + * @mf_flags: memory failure flags + */ +int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index, + unsigned long count, int mf_flags) +{ + LIST_HEAD(to_kill); + dax_entry_t cookie; + struct page *page; + size_t end = index + count; + + mf_flags |= MF_ACTION_REQUIRED | MF_MUST_KILL; + + for (; index < end; index++) { + page = NULL; + cookie = dax_lock_mapping_entry(mapping, index, &page); + if (!cookie) + return -EBUSY; + if (!page) + goto unlock; + + SetPageHWPoison(page); + + collect_procs_fsdax(page, mapping, index, &to_kill); + unmap_and_kill(&to_kill, page_to_pfn(page), mapping, + index, mf_flags); +unlock: + dax_unlock_mapping_entry(mapping, index, cookie); + } + return 0; +} +EXPORT_SYMBOL_GPL(mf_dax_kill_procs); +#endif /* CONFIG_FS_DAX */ + +#ifdef CONFIG_HUGETLB_PAGE + +/* + * Struct raw_hwp_page represents information about "raw error page", + * constructing singly linked list from ->_hugetlb_hwpoison field of folio. + */ +struct raw_hwp_page { + struct llist_node node; + struct page *page; +}; + +static inline struct llist_head *raw_hwp_list_head(struct folio *folio) +{ + return (struct llist_head *)&folio->_hugetlb_hwpoison; +} + +bool is_raw_hwpoison_page_in_hugepage(struct page *page) +{ + struct llist_head *raw_hwp_head; + struct raw_hwp_page *p; + struct folio *folio = page_folio(page); + bool ret = false; + + if (!folio_test_hwpoison(folio)) + return false; + + if (!folio_test_hugetlb(folio)) + return PageHWPoison(page); + + /* + * When RawHwpUnreliable is set, kernel lost track of which subpages + * are HWPOISON. So return as if ALL subpages are HWPOISONed. + */ + if (folio_test_hugetlb_raw_hwp_unreliable(folio)) + return true; + + mutex_lock(&mf_mutex); + + raw_hwp_head = raw_hwp_list_head(folio); + llist_for_each_entry(p, raw_hwp_head->first, node) { + if (page == p->page) { + ret = true; + break; + } + } + + mutex_unlock(&mf_mutex); + + return ret; +} + +static unsigned long __folio_free_raw_hwp(struct folio *folio, bool move_flag) +{ + struct llist_node *head; + struct raw_hwp_page *p, *next; + unsigned long count = 0; + + head = llist_del_all(raw_hwp_list_head(folio)); + llist_for_each_entry_safe(p, next, head, node) { + if (move_flag) + SetPageHWPoison(p->page); + else + num_poisoned_pages_sub(page_to_pfn(p->page), 1); + kfree(p); + count++; + } + return count; +} + +static int folio_set_hugetlb_hwpoison(struct folio *folio, struct page *page) +{ + struct llist_head *head; + struct raw_hwp_page *raw_hwp; + struct raw_hwp_page *p, *next; + int ret = folio_test_set_hwpoison(folio) ? -EHWPOISON : 0; + + /* + * Once the hwpoison hugepage has lost reliable raw error info, + * there is little meaning to keep additional error info precisely, + * so skip to add additional raw error info. + */ + if (folio_test_hugetlb_raw_hwp_unreliable(folio)) + return -EHWPOISON; + head = raw_hwp_list_head(folio); + llist_for_each_entry_safe(p, next, head->first, node) { + if (p->page == page) + return -EHWPOISON; + } + + raw_hwp = kmalloc(sizeof(struct raw_hwp_page), GFP_ATOMIC); + if (raw_hwp) { + raw_hwp->page = page; + llist_add(&raw_hwp->node, head); + /* the first error event will be counted in action_result(). */ + if (ret) + num_poisoned_pages_inc(page_to_pfn(page)); + } else { + /* + * Failed to save raw error info. We no longer trace all + * hwpoisoned subpages, and we need refuse to free/dissolve + * this hwpoisoned hugepage. + */ + folio_set_hugetlb_raw_hwp_unreliable(folio); + /* + * Once hugetlb_raw_hwp_unreliable is set, raw_hwp_page is not + * used any more, so free it. + */ + __folio_free_raw_hwp(folio, false); + } + return ret; +} + +static unsigned long folio_free_raw_hwp(struct folio *folio, bool move_flag) +{ + /* + * hugetlb_vmemmap_optimized hugepages can't be freed because struct + * pages for tail pages are required but they don't exist. + */ + if (move_flag && folio_test_hugetlb_vmemmap_optimized(folio)) + return 0; + + /* + * hugetlb_raw_hwp_unreliable hugepages shouldn't be unpoisoned by + * definition. + */ + if (folio_test_hugetlb_raw_hwp_unreliable(folio)) + return 0; + + return __folio_free_raw_hwp(folio, move_flag); +} + +void folio_clear_hugetlb_hwpoison(struct folio *folio) +{ + if (folio_test_hugetlb_raw_hwp_unreliable(folio)) + return; + if (folio_test_hugetlb_vmemmap_optimized(folio)) + return; + folio_clear_hwpoison(folio); + folio_free_raw_hwp(folio, true); +} + +/* + * Called from hugetlb code with hugetlb_lock held. + * + * Return values: + * 0 - free hugepage + * 1 - in-use hugepage + * 2 - not a hugepage + * -EBUSY - the hugepage is busy (try to retry) + * -EHWPOISON - the hugepage is already hwpoisoned + */ +int __get_huge_page_for_hwpoison(unsigned long pfn, int flags, + bool *migratable_cleared) +{ + struct page *page = pfn_to_page(pfn); + struct folio *folio = page_folio(page); + int ret = 2; /* fallback to normal page handling */ + bool count_increased = false; + + if (!folio_test_hugetlb(folio)) + goto out; + + if (flags & MF_COUNT_INCREASED) { + ret = 1; + count_increased = true; + } else if (folio_test_hugetlb_freed(folio)) { + ret = 0; + } else if (folio_test_hugetlb_migratable(folio)) { + ret = folio_try_get(folio); + if (ret) + count_increased = true; + } else { + ret = -EBUSY; + if (!(flags & MF_NO_RETRY)) + goto out; + } + + if (folio_set_hugetlb_hwpoison(folio, page)) { + ret = -EHWPOISON; + goto out; + } + + /* + * Clearing hugetlb_migratable for hwpoisoned hugepages to prevent them + * from being migrated by memory hotremove. + */ + if (count_increased && folio_test_hugetlb_migratable(folio)) { + folio_clear_hugetlb_migratable(folio); + *migratable_cleared = true; + } + + return ret; +out: + if (count_increased) + folio_put(folio); + return ret; +} + +/* + * Taking refcount of hugetlb pages needs extra care about race conditions + * with basic operations like hugepage allocation/free/demotion. + * So some of prechecks for hwpoison (pinning, and testing/setting + * PageHWPoison) should be done in single hugetlb_lock range. + */ +static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb) +{ + int res; + struct page *p = pfn_to_page(pfn); + struct folio *folio; + unsigned long page_flags; + bool migratable_cleared = false; + + *hugetlb = 1; +retry: + res = get_huge_page_for_hwpoison(pfn, flags, &migratable_cleared); + if (res == 2) { /* fallback to normal page handling */ + *hugetlb = 0; + return 0; + } else if (res == -EHWPOISON) { + pr_err("%#lx: already hardware poisoned\n", pfn); + if (flags & MF_ACTION_REQUIRED) { + folio = page_folio(p); + res = kill_accessing_process(current, folio_pfn(folio), flags); + } + return res; + } else if (res == -EBUSY) { + if (!(flags & MF_NO_RETRY)) { + flags |= MF_NO_RETRY; + goto retry; + } + return action_result(pfn, MF_MSG_UNKNOWN, MF_IGNORED); + } + + folio = page_folio(p); + folio_lock(folio); + + if (hwpoison_filter(p)) { + folio_clear_hugetlb_hwpoison(folio); + if (migratable_cleared) + folio_set_hugetlb_migratable(folio); + folio_unlock(folio); + if (res == 1) + folio_put(folio); + return -EOPNOTSUPP; + } + + /* + * Handling free hugepage. The possible race with hugepage allocation + * or demotion can be prevented by PageHWPoison flag. + */ + if (res == 0) { + folio_unlock(folio); + if (__page_handle_poison(p) >= 0) { + page_ref_inc(p); + res = MF_RECOVERED; + } else { + res = MF_FAILED; + } + return action_result(pfn, MF_MSG_FREE_HUGE, res); + } + + page_flags = folio->flags; + + if (!hwpoison_user_mappings(p, pfn, flags, &folio->page)) { + folio_unlock(folio); + return action_result(pfn, MF_MSG_UNMAP_FAILED, MF_IGNORED); + } + + return identify_page_state(pfn, p, page_flags); +} + +#else +static inline int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb) +{ + return 0; +} + +static inline unsigned long folio_free_raw_hwp(struct folio *folio, bool flag) +{ + return 0; +} +#endif /* CONFIG_HUGETLB_PAGE */ + +/* Drop the extra refcount in case we come from madvise() */ +static void put_ref_page(unsigned long pfn, int flags) +{ + struct page *page; + + if (!(flags & MF_COUNT_INCREASED)) + return; + + page = pfn_to_page(pfn); + if (page) + put_page(page); +} + +static int memory_failure_dev_pagemap(unsigned long pfn, int flags, + struct dev_pagemap *pgmap) +{ + int rc = -ENXIO; + + /* device metadata space is not recoverable */ + if (!pgmap_pfn_valid(pgmap, pfn)) + goto out; + + /* + * Call driver's implementation to handle the memory failure, otherwise + * fall back to generic handler. + */ + if (pgmap_has_memory_failure(pgmap)) { + rc = pgmap->ops->memory_failure(pgmap, pfn, 1, flags); + /* + * Fall back to generic handler too if operation is not + * supported inside the driver/device/filesystem. + */ + if (rc != -EOPNOTSUPP) + goto out; + } + + rc = mf_generic_kill_procs(pfn, flags, pgmap); +out: + /* drop pgmap ref acquired in caller */ + put_dev_pagemap(pgmap); + if (rc != -EOPNOTSUPP) + 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 held. + * + * Return: 0 for successfully handled the memory error, + * -EOPNOTSUPP for hwpoison_filter() filtered the error event, + * < 0(except -EOPNOTSUPP) on failure. + */ +int memory_failure(unsigned long pfn, int flags) +{ + struct page *p; + struct page *hpage; + struct dev_pagemap *pgmap; + int res = 0; + unsigned long page_flags; + bool retry = true; + int hugetlb = 0; + + if (!sysctl_memory_failure_recovery) + panic("Memory failure on page %lx", pfn); + + mutex_lock(&mf_mutex); + + if (!(flags & MF_SW_SIMULATED)) + hw_memory_failure = true; + + p = pfn_to_online_page(pfn); + if (!p) { + res = arch_memory_failure(pfn, flags); + if (res == 0) + goto unlock_mutex; + + if (pfn_valid(pfn)) { + pgmap = get_dev_pagemap(pfn, NULL); + put_ref_page(pfn, flags); + if (pgmap) { + res = memory_failure_dev_pagemap(pfn, flags, + pgmap); + goto unlock_mutex; + } + } + pr_err("%#lx: memory outside kernel control\n", pfn); + res = -ENXIO; + goto unlock_mutex; + } + +try_again: + res = try_memory_failure_hugetlb(pfn, flags, &hugetlb); + if (hugetlb) + goto unlock_mutex; + + if (TestSetPageHWPoison(p)) { + pr_err("%#lx: already hardware poisoned\n", pfn); + res = -EHWPOISON; + if (flags & MF_ACTION_REQUIRED) + res = kill_accessing_process(current, pfn, flags); + if (flags & MF_COUNT_INCREASED) + put_page(p); + goto unlock_mutex; + } + + /* + * We need/can do nothing about count=0 pages. + * 1) it's a free page, and therefore in safe hand: + * check_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)) { + res = get_hwpoison_page(p, flags); + if (!res) { + if (is_free_buddy_page(p)) { + if (take_page_off_buddy(p)) { + page_ref_inc(p); + res = MF_RECOVERED; + } else { + /* We lost the race, try again */ + if (retry) { + ClearPageHWPoison(p); + retry = false; + goto try_again; + } + res = MF_FAILED; + } + res = action_result(pfn, MF_MSG_BUDDY, res); + } else { + res = action_result(pfn, MF_MSG_KERNEL_HIGH_ORDER, MF_IGNORED); + } + goto unlock_mutex; + } else if (res < 0) { + res = action_result(pfn, MF_MSG_UNKNOWN, MF_IGNORED); + goto unlock_mutex; + } + } + + hpage = compound_head(p); + if (PageTransHuge(hpage)) { + /* + * The flag must be set after the refcount is bumped + * otherwise it may race with THP split. + * And the flag can't be set in get_hwpoison_page() since + * it is called by soft offline too and it is just called + * for !MF_COUNT_INCREASED. So here seems to be the best + * place. + * + * Don't need care about the above error handling paths for + * get_hwpoison_page() since they handle either free page + * or unhandlable page. The refcount is bumped iff the + * page is a valid handlable page. + */ + SetPageHasHWPoisoned(hpage); + if (try_to_split_thp_page(p) < 0) { + res = action_result(pfn, MF_MSG_UNSPLIT_THP, MF_IGNORED); + goto unlock_mutex; + } + 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); + + lock_page(p); + + /* + * We're only intended to deal with the non-Compound page here. + * However, the page could have changed compound pages due to + * race window. If this happens, we could try again to hopefully + * handle the page next round. + */ + if (PageCompound(p)) { + if (retry) { + ClearPageHWPoison(p); + unlock_page(p); + put_page(p); + flags &= ~MF_COUNT_INCREASED; + retry = false; + goto try_again; + } + res = action_result(pfn, MF_MSG_DIFFERENT_COMPOUND, MF_IGNORED); + goto unlock_page; + } + + /* + * 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; + + if (hwpoison_filter(p)) { + ClearPageHWPoison(p); + unlock_page(p); + put_page(p); + res = -EOPNOTSUPP; + goto unlock_mutex; + } + + /* + * __munlock_folio() 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 (!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: __filemap_remove_folio() assumes unmapped page. + */ + if (!hwpoison_user_mappings(p, pfn, flags, p)) { + res = action_result(pfn, MF_MSG_UNMAP_FAILED, MF_IGNORED); + goto unlock_page; + } + + /* + * Torn down by someone else? + */ + if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) { + res = action_result(pfn, MF_MSG_TRUNCATED_LRU, MF_IGNORED); + goto unlock_page; + } + +identify_page_state: + res = identify_page_state(pfn, p, page_flags); + mutex_unlock(&mf_mutex); + return res; +unlock_page: + unlock_page(p); +unlock_mutex: + mutex_unlock(&mf_mutex); + 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("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); + } + + register_sysctl_init("vm", memory_failure_table); + + return 0; +} +core_initcall(memory_failure_init); + +#undef pr_fmt +#define pr_fmt(fmt) "" fmt +#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 folio *folio; + struct page *p; + int ret = -EBUSY, ghp; + unsigned long count = 1; + bool huge = false; + static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL, + DEFAULT_RATELIMIT_BURST); + + if (!pfn_valid(pfn)) + return -ENXIO; + + p = pfn_to_page(pfn); + folio = page_folio(p); + + mutex_lock(&mf_mutex); + + if (hw_memory_failure) { + unpoison_pr_info("Unpoison: Disabled after HW memory failure %#lx\n", + pfn, &unpoison_rs); + ret = -EOPNOTSUPP; + goto unlock_mutex; + } + + if (!PageHWPoison(p)) { + unpoison_pr_info("Unpoison: Page was already unpoisoned %#lx\n", + pfn, &unpoison_rs); + goto unlock_mutex; + } + + if (folio_ref_count(folio) > 1) { + unpoison_pr_info("Unpoison: Someone grabs the hwpoison page %#lx\n", + pfn, &unpoison_rs); + goto unlock_mutex; + } + + if (folio_test_slab(folio) || PageTable(&folio->page) || + folio_test_reserved(folio) || PageOffline(&folio->page)) + goto unlock_mutex; + + /* + * Note that folio->_mapcount is overloaded in SLAB, so the simple test + * in folio_mapped() has to be done after folio_test_slab() is checked. + */ + if (folio_mapped(folio)) { + unpoison_pr_info("Unpoison: Someone maps the hwpoison page %#lx\n", + pfn, &unpoison_rs); + goto unlock_mutex; + } + + if (folio_mapping(folio)) { + unpoison_pr_info("Unpoison: the hwpoison page has non-NULL mapping %#lx\n", + pfn, &unpoison_rs); + goto unlock_mutex; + } + + ghp = get_hwpoison_page(p, MF_UNPOISON); + if (!ghp) { + if (PageHuge(p)) { + huge = true; + count = folio_free_raw_hwp(folio, false); + if (count == 0) + goto unlock_mutex; + } + ret = folio_test_clear_hwpoison(folio) ? 0 : -EBUSY; + } else if (ghp < 0) { + if (ghp == -EHWPOISON) { + ret = put_page_back_buddy(p) ? 0 : -EBUSY; + } else { + ret = ghp; + unpoison_pr_info("Unpoison: failed to grab page %#lx\n", + pfn, &unpoison_rs); + } + } else { + if (PageHuge(p)) { + huge = true; + count = folio_free_raw_hwp(folio, false); + if (count == 0) { + folio_put(folio); + goto unlock_mutex; + } + } + + folio_put(folio); + if (TestClearPageHWPoison(p)) { + folio_put(folio); + ret = 0; + } + } + +unlock_mutex: + mutex_unlock(&mf_mutex); + if (!ret) { + if (!huge) + num_poisoned_pages_sub(pfn, 1); + unpoison_pr_info("Unpoison: Software-unpoisoned page %#lx\n", + page_to_pfn(p), &unpoison_rs); + } + return ret; +} +EXPORT_SYMBOL(unpoison_memory); + +static bool isolate_page(struct page *page, struct list_head *pagelist) +{ + bool isolated = false; + + if (PageHuge(page)) { + isolated = isolate_hugetlb(page_folio(page), pagelist); + } else { + bool lru = !__PageMovable(page); + + if (lru) + isolated = isolate_lru_page(page); + else + isolated = isolate_movable_page(page, + ISOLATE_UNEVICTABLE); + + if (isolated) { + list_add(&page->lru, pagelist); + if (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_page(). + * 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_page() as well. + */ + put_page(page); + return isolated; +} + +/* + * soft_offline_in_use_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_in_use_page(struct page *page) +{ + long 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, + }; + + if (!huge && PageTransHuge(hpage)) { + if (try_to_split_thp_page(page)) { + pr_info("soft offline: %#lx: thp split failed\n", pfn); + return -EBUSY; + } + hpage = page; + } + + lock_page(page); + if (!huge) + 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 (!huge && PageLRU(page) && !PageSwapCache(page)) + /* + * Try to invalidate first. This should work for + * non dirty unmapped page cache pages. + */ + ret = invalidate_inode_page(page); + unlock_page(page); + + 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, NULL); + 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 %ld, type %pGp\n", + pfn, msg_page[huge], ret, &page->flags); + if (ret > 0) + ret = -EBUSY; + } + } else { + pr_info("soft offline: %#lx: %s isolation failed, page count %d, type %pGp\n", + pfn, msg_page[huge], page_count(page), &page->flags); + ret = -EBUSY; + } + return ret; +} + +/** + * soft_offline_page - Soft offline a page. + * @pfn: pfn to soft-offline + * @flags: flags. Same as memory_failure(). + * + * Returns 0 on success + * -EOPNOTSUPP for hwpoison_filter() filtered the error event + * < 0 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; + + if (!pfn_valid(pfn)) { + WARN_ON_ONCE(flags & MF_COUNT_INCREASED); + return -ENXIO; + } + + /* Only online pages can be soft-offlined (esp., not ZONE_DEVICE). */ + page = pfn_to_online_page(pfn); + if (!page) { + put_ref_page(pfn, flags); + return -EIO; + } + + mutex_lock(&mf_mutex); + + if (PageHWPoison(page)) { + pr_info("%s: %#lx page already poisoned\n", __func__, pfn); + put_ref_page(pfn, flags); + mutex_unlock(&mf_mutex); + return 0; + } + +retry: + get_online_mems(); + ret = get_hwpoison_page(page, flags | MF_SOFT_OFFLINE); + put_online_mems(); + + if (hwpoison_filter(page)) { + if (ret > 0) + put_page(page); + + mutex_unlock(&mf_mutex); + return -EOPNOTSUPP; + } + + 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; + } + } + + mutex_unlock(&mf_mutex); + + return ret; +} |