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Diffstat (limited to 'mm/memory-failure.c')
| -rw-r--r-- | mm/memory-failure.c | 1936 |
1 files changed, 1936 insertions, 0 deletions
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; +} |