| /* |
| * Copyright (C) 2008, 2009 Intel Corporation |
| * Authors: Andi Kleen, Fengguang Wu |
| * |
| * This software may be redistributed and/or modified under the terms of |
| * the GNU General Public License ("GPL") version 2 only as published by the |
| * Free Software Foundation. |
| * |
| * High level machine check handler. Handles pages reported by the |
| * hardware as being corrupted usually due to a 2bit ECC memory or cache |
| * failure. |
| * |
| * Handles page cache pages in various states. The tricky part |
| * here is that we can access any page asynchronous to other VM |
| * users, because memory failures could happen anytime and anywhere, |
| * possibly violating 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. |
| * |
| * 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 |
| * mappings. In short it can be quite slow. But since memory corruptions |
| * are rare we hope to get away with this. |
| */ |
| |
| /* |
| * Notebook: |
| * - hugetlb needs more code |
| * - kcore/oldmem/vmcore/mem/kmem check for hwpoison pages |
| * - pass bad pages to kdump next kernel |
| */ |
| #define DEBUG 1 /* remove me in 2.6.34 */ |
| #include <linux/kernel.h> |
| #include <linux/mm.h> |
| #include <linux/page-flags.h> |
| #include <linux/kernel-page-flags.h> |
| #include <linux/sched.h> |
| #include <linux/ksm.h> |
| #include <linux/rmap.h> |
| #include <linux/pagemap.h> |
| #include <linux/swap.h> |
| #include <linux/backing-dev.h> |
| #include "internal.h" |
| |
| int sysctl_memory_failure_early_kill __read_mostly = 0; |
| |
| int sysctl_memory_failure_recovery __read_mostly = 1; |
| |
| atomic_long_t mce_bad_pages __read_mostly = ATOMIC_LONG_INIT(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_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 page |
| */ |
| 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; |
| } |
| |
| int hwpoison_filter(struct page *p) |
| { |
| if (hwpoison_filter_dev(p)) |
| return -EINVAL; |
| |
| if (hwpoison_filter_flags(p)) |
| return -EINVAL; |
| |
| return 0; |
| } |
| EXPORT_SYMBOL_GPL(hwpoison_filter); |
| |
| /* |
| * Send all the processes who have the page mapped an ``action optional'' |
| * signal. |
| */ |
| static int kill_proc_ao(struct task_struct *t, unsigned long addr, int trapno, |
| unsigned long pfn) |
| { |
| struct siginfo si; |
| int ret; |
| |
| printk(KERN_ERR |
| "MCE %#lx: Killing %s:%d early due to hardware memory corruption\n", |
| pfn, t->comm, t->pid); |
| si.si_signo = SIGBUS; |
| si.si_errno = 0; |
| si.si_code = BUS_MCEERR_AO; |
| si.si_addr = (void *)addr; |
| #ifdef __ARCH_SI_TRAPNO |
| si.si_trapno = trapno; |
| #endif |
| si.si_addr_lsb = PAGE_SHIFT; |
| /* |
| * 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 noone will do that? |
| */ |
| ret = send_sig_info(SIGBUS, &si, t); /* synchronous? */ |
| if (ret < 0) |
| printk(KERN_INFO "MCE: Error sending signal to %s:%d: %d\n", |
| t->comm, t->pid, ret); |
| return ret; |
| } |
| |
| /* |
| * When a unknown page type is encountered drain as many buffers as possible |
| * in the hope to turn the page into a LRU or free page, which we can handle. |
| */ |
| void shake_page(struct page *p) |
| { |
| if (!PageSlab(p)) { |
| lru_add_drain_all(); |
| if (PageLRU(p)) |
| return; |
| drain_all_pages(); |
| if (PageLRU(p) || is_free_buddy_page(p)) |
| return; |
| } |
| /* |
| * Could call shrink_slab here (which would also |
| * shrink other caches). Unfortunately that might |
| * also access the corrupted page, which could be fatal. |
| */ |
| } |
| EXPORT_SYMBOL_GPL(shake_page); |
| |
| /* |
| * Kill all processes that have a poisoned page mapped and then isolate |
| * the page. |
| * |
| * General strategy: |
| * Find all processes having the page mapped and kill them. |
| * But we keep a page reference around so that the page is not |
| * actually freed yet. |
| * Then stash the page away |
| * |
| * There's no convenient way to get back to mapped processes |
| * from the VMAs. So do a brute-force search over all |
| * running processes. |
| * |
| * Remember that machine checks are not common (or rather |
| * if they are common you have other problems), so this shouldn't |
| * be a performance issue. |
| * |
| * Also there are some races possible while we get from the |
| * error detection to actually handle it. |
| */ |
| |
| struct to_kill { |
| struct list_head nd; |
| struct task_struct *tsk; |
| unsigned long addr; |
| unsigned addr_valid:1; |
| }; |
| |
| /* |
| * Failure handling: if we can't find or can't kill a process there's |
| * not much we can do. We just print a message and ignore otherwise. |
| */ |
| |
| /* |
| * Schedule a process for later kill. |
| * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM. |
| * TBD would GFP_NOIO be enough? |
| */ |
| static void add_to_kill(struct task_struct *tsk, struct page *p, |
| struct vm_area_struct *vma, |
| struct list_head *to_kill, |
| struct to_kill **tkc) |
| { |
| struct to_kill *tk; |
| |
| if (*tkc) { |
| tk = *tkc; |
| *tkc = NULL; |
| } else { |
| tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC); |
| if (!tk) { |
| printk(KERN_ERR |
| "MCE: Out of memory while machine check handling\n"); |
| return; |
| } |
| } |
| tk->addr = page_address_in_vma(p, vma); |
| tk->addr_valid = 1; |
| |
| /* |
| * In theory we don't have to kill when the page was |
| * munmaped. But it could be also a mremap. Since that's |
| * likely very rare kill anyways just out of paranoia, but use |
| * a SIGKILL because the error is not contained anymore. |
| */ |
| if (tk->addr == -EFAULT) { |
| pr_debug("MCE: Unable to find user space address %lx in %s\n", |
| page_to_pfn(p), tsk->comm); |
| tk->addr_valid = 0; |
| } |
| get_task_struct(tsk); |
| tk->tsk = tsk; |
| list_add_tail(&tk->nd, to_kill); |
| } |
| |
| /* |
| * Kill the processes that have been collected earlier. |
| * |
| * Only do anything when DOIT is set, otherwise just free the list |
| * (this is used for clean pages which do not need killing) |
| * Also when FAIL is set do a force kill because something went |
| * wrong earlier. |
| */ |
| static void kill_procs_ao(struct list_head *to_kill, int doit, int trapno, |
| int fail, unsigned long pfn) |
| { |
| struct to_kill *tk, *next; |
| |
| list_for_each_entry_safe (tk, next, to_kill, nd) { |
| if (doit) { |
| /* |
| * In case something went wrong with munmapping |
| * make sure the process doesn't catch the |
| * signal and then access the memory. Just kill it. |
| * the signal handlers |
| */ |
| if (fail || tk->addr_valid == 0) { |
| printk(KERN_ERR |
| "MCE %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n", |
| pfn, tk->tsk->comm, tk->tsk->pid); |
| force_sig(SIGKILL, tk->tsk); |
| } |
| |
| /* |
| * In theory the process could have mapped |
| * something else on the address in-between. We could |
| * check for that, but we need to tell the |
| * process anyways. |
| */ |
| else if (kill_proc_ao(tk->tsk, tk->addr, trapno, |
| pfn) < 0) |
| printk(KERN_ERR |
| "MCE %#lx: Cannot send advisory machine check signal to %s:%d\n", |
| pfn, tk->tsk->comm, tk->tsk->pid); |
| } |
| put_task_struct(tk->tsk); |
| kfree(tk); |
| } |
| } |
| |
| static int task_early_kill(struct task_struct *tsk) |
| { |
| if (!tsk->mm) |
| return 0; |
| if (tsk->flags & PF_MCE_PROCESS) |
| return !!(tsk->flags & PF_MCE_EARLY); |
| return sysctl_memory_failure_early_kill; |
| } |
| |
| /* |
| * Collect processes when the error hit an anonymous page. |
| */ |
| static void collect_procs_anon(struct page *page, struct list_head *to_kill, |
| struct to_kill **tkc) |
| { |
| struct vm_area_struct *vma; |
| struct task_struct *tsk; |
| struct anon_vma *av; |
| |
| read_lock(&tasklist_lock); |
| av = page_lock_anon_vma(page); |
| if (av == NULL) /* Not actually mapped anymore */ |
| goto out; |
| for_each_process (tsk) { |
| if (!task_early_kill(tsk)) |
| continue; |
| list_for_each_entry (vma, &av->head, anon_vma_node) { |
| if (!page_mapped_in_vma(page, vma)) |
| continue; |
| if (vma->vm_mm == tsk->mm) |
| add_to_kill(tsk, page, vma, to_kill, tkc); |
| } |
| } |
| page_unlock_anon_vma(av); |
| out: |
| read_unlock(&tasklist_lock); |
| } |
| |
| /* |
| * Collect processes when the error hit a file mapped page. |
| */ |
| static void collect_procs_file(struct page *page, struct list_head *to_kill, |
| struct to_kill **tkc) |
| { |
| struct vm_area_struct *vma; |
| struct task_struct *tsk; |
| struct prio_tree_iter iter; |
| struct address_space *mapping = page->mapping; |
| |
| /* |
| * A note on the locking order between the two locks. |
| * We don't rely on this particular order. |
| * If you have some other code that needs a different order |
| * feel free to switch them around. Or add a reverse link |
| * from mm_struct to task_struct, then this could be all |
| * done without taking tasklist_lock and looping over all tasks. |
| */ |
| |
| read_lock(&tasklist_lock); |
| spin_lock(&mapping->i_mmap_lock); |
| for_each_process(tsk) { |
| pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); |
| |
| if (!task_early_kill(tsk)) |
| continue; |
| |
| vma_prio_tree_foreach(vma, &iter, &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 == tsk->mm) |
| add_to_kill(tsk, page, vma, to_kill, tkc); |
| } |
| } |
| spin_unlock(&mapping->i_mmap_lock); |
| read_unlock(&tasklist_lock); |
| } |
| |
| /* |
| * Collect the processes who have the corrupted page mapped to kill. |
| * This is done in two steps for locking reasons. |
| * First preallocate one tokill structure outside the spin locks, |
| * so that we can kill at least one process reasonably reliable. |
| */ |
| static void collect_procs(struct page *page, struct list_head *tokill) |
| { |
| struct to_kill *tk; |
| |
| if (!page->mapping) |
| return; |
| |
| tk = kmalloc(sizeof(struct to_kill), GFP_NOIO); |
| if (!tk) |
| return; |
| if (PageAnon(page)) |
| collect_procs_anon(page, tokill, &tk); |
| else |
| collect_procs_file(page, tokill, &tk); |
| kfree(tk); |
| } |
| |
| /* |
| * Error handlers for various types of pages. |
| */ |
| |
| enum outcome { |
| IGNORED, /* Error: cannot be handled */ |
| FAILED, /* Error: handling failed */ |
| DELAYED, /* Will be handled later */ |
| RECOVERED, /* Successfully recovered */ |
| }; |
| |
| static const char *action_name[] = { |
| [IGNORED] = "Ignored", |
| [FAILED] = "Failed", |
| [DELAYED] = "Delayed", |
| [RECOVERED] = "Recovered", |
| }; |
| |
| /* |
| * XXX: It is possible that a page is isolated from LRU cache, |
| * and then kept in swap cache or failed to remove from page cache. |
| * The page count will stop it from being freed by unpoison. |
| * Stress tests should be aware of this memory leak problem. |
| */ |
| static int delete_from_lru_cache(struct page *p) |
| { |
| if (!isolate_lru_page(p)) { |
| /* |
| * Clear sensible page flags, so that the buddy system won't |
| * complain when the page is unpoison-and-freed. |
| */ |
| ClearPageActive(p); |
| ClearPageUnevictable(p); |
| /* |
| * drop the page count elevated by isolate_lru_page() |
| */ |
| page_cache_release(p); |
| return 0; |
| } |
| return -EIO; |
| } |
| |
| /* |
| * Error hit kernel page. |
| * Do nothing, try to be lucky and not touch this instead. For a few cases we |
| * could be more sophisticated. |
| */ |
| static int me_kernel(struct page *p, unsigned long pfn) |
| { |
| return IGNORED; |
| } |
| |
| /* |
| * Page in unknown state. Do nothing. |
| */ |
| static int me_unknown(struct page *p, unsigned long pfn) |
| { |
| printk(KERN_ERR "MCE %#lx: Unknown page state\n", pfn); |
| return FAILED; |
| } |
| |
| /* |
| * Clean (or cleaned) page cache page. |
| */ |
| static int me_pagecache_clean(struct page *p, unsigned long pfn) |
| { |
| int err; |
| int ret = FAILED; |
| struct address_space *mapping; |
| |
| delete_from_lru_cache(p); |
| |
| /* |
| * For anonymous pages we're done the only reference left |
| * should be the one m_f() holds. |
| */ |
| if (PageAnon(p)) |
| return RECOVERED; |
| |
| /* |
| * Now truncate the page in the page cache. This is really |
| * more like a "temporary hole punch" |
| * Don't do this for block devices when someone else |
| * has a reference, because it could be file system metadata |
| * and that's not safe to truncate. |
| */ |
| mapping = page_mapping(p); |
| if (!mapping) { |
| /* |
| * Page has been teared down in the meanwhile |
| */ |
| return FAILED; |
| } |
| |
| /* |
| * Truncation is a bit tricky. Enable it per file system for now. |
| * |
| * Open: to take i_mutex or not for this? Right now we don't. |
| */ |
| if (mapping->a_ops->error_remove_page) { |
| err = mapping->a_ops->error_remove_page(mapping, p); |
| if (err != 0) { |
| printk(KERN_INFO "MCE %#lx: Failed to punch page: %d\n", |
| pfn, err); |
| } else if (page_has_private(p) && |
| !try_to_release_page(p, GFP_NOIO)) { |
| pr_debug("MCE %#lx: failed to release buffers\n", pfn); |
| } else { |
| ret = RECOVERED; |
| } |
| } else { |
| /* |
| * If the file system doesn't support it just invalidate |
| * This fails on dirty or anything with private pages |
| */ |
| if (invalidate_inode_page(p)) |
| ret = RECOVERED; |
| else |
| printk(KERN_INFO "MCE %#lx: Failed to invalidate\n", |
| pfn); |
| } |
| return ret; |
| } |
| |
| /* |
| * Dirty cache page 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 inbetween then the error |
| * will not be properly reported. |
| * |
| * This can already happen even without hwpoisoned |
| * pages: first on metadata IO errors (which only |
| * report through AS_EIO) or when the page is dropped |
| * at the wrong time. |
| * |
| * So right now we assume that the application DTRT on |
| * the first EIO, but we're not worse than other parts |
| * of the kernel. |
| */ |
| mapping_set_error(mapping, EIO); |
| } |
| |
| return me_pagecache_clean(p, pfn); |
| } |
| |
| /* |
| * Clean and dirty swap cache. |
| * |
| * Dirty swap cache page is tricky to handle. The page could live both in page |
| * cache and swap cache(ie. page is freshly swapped in). So it could be |
| * referenced concurrently by 2 types of PTEs: |
| * normal PTEs and swap PTEs. We try to handle them consistently by calling |
| * try_to_unmap(TTU_IGNORE_HWPOISON) to convert the normal PTEs to swap PTEs, |
| * and then |
| * - clear dirty bit to prevent IO |
| * - remove from LRU |
| * - but keep in the swap cache, so that when we return to it on |
| * a later page fault, we know the application is accessing |
| * corrupted data and shall be killed (we installed simple |
| * interception code in do_swap_page to catch it). |
| * |
| * Clean swap cache pages can be directly isolated. A later page fault will |
| * bring in the known good data from disk. |
| */ |
| static int me_swapcache_dirty(struct page *p, unsigned long pfn) |
| { |
| ClearPageDirty(p); |
| /* Trigger EIO in shmem: */ |
| ClearPageUptodate(p); |
| |
| if (!delete_from_lru_cache(p)) |
| return DELAYED; |
| else |
| return FAILED; |
| } |
| |
| static int me_swapcache_clean(struct page *p, unsigned long pfn) |
| { |
| delete_from_swap_cache(p); |
| |
| if (!delete_from_lru_cache(p)) |
| return RECOVERED; |
| else |
| return FAILED; |
| } |
| |
| /* |
| * Huge pages. Needs work. |
| * Issues: |
| * No rmap support so we cannot find the original mapper. In theory could walk |
| * all MMs and look for the mappings, but that would be non atomic and racy. |
| * Need rmap for hugepages for this. Alternatively we could employ a heuristic, |
| * like just walking the current process and hoping it has it mapped (that |
| * should be usually true for the common "shared database cache" case) |
| * Should handle free huge pages and dequeue them too, but this needs to |
| * handle huge page accounting correctly. |
| */ |
| static int me_huge_page(struct page *p, unsigned long pfn) |
| { |
| return FAILED; |
| } |
| |
| /* |
| * 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 extremly careful. |
| * |
| * This is not complete. More states could be added. |
| * For any missing state don't attempt recovery. |
| */ |
| |
| #define dirty (1UL << PG_dirty) |
| #define sc (1UL << PG_swapcache) |
| #define unevict (1UL << PG_unevictable) |
| #define mlock (1UL << PG_mlocked) |
| #define writeback (1UL << PG_writeback) |
| #define lru (1UL << PG_lru) |
| #define swapbacked (1UL << PG_swapbacked) |
| #define head (1UL << PG_head) |
| #define tail (1UL << PG_tail) |
| #define compound (1UL << PG_compound) |
| #define slab (1UL << PG_slab) |
| #define reserved (1UL << PG_reserved) |
| |
| static struct page_state { |
| unsigned long mask; |
| unsigned long res; |
| char *msg; |
| int (*action)(struct page *p, unsigned long pfn); |
| } error_states[] = { |
| { reserved, reserved, "reserved 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, "kernel slab", me_kernel }, |
| |
| #ifdef CONFIG_PAGEFLAGS_EXTENDED |
| { head, head, "huge", me_huge_page }, |
| { tail, tail, "huge", me_huge_page }, |
| #else |
| { compound, compound, "huge", me_huge_page }, |
| #endif |
| |
| { sc|dirty, sc|dirty, "swapcache", me_swapcache_dirty }, |
| { sc|dirty, sc, "swapcache", me_swapcache_clean }, |
| |
| { unevict|dirty, unevict|dirty, "unevictable LRU", me_pagecache_dirty}, |
| { unevict, unevict, "unevictable LRU", me_pagecache_clean}, |
| |
| { mlock|dirty, mlock|dirty, "mlocked LRU", me_pagecache_dirty }, |
| { mlock, mlock, "mlocked LRU", me_pagecache_clean }, |
| |
| { lru|dirty, lru|dirty, "LRU", me_pagecache_dirty }, |
| { lru|dirty, lru, "clean LRU", me_pagecache_clean }, |
| |
| /* |
| * Catchall entry: must be at end. |
| */ |
| { 0, 0, "unknown page state", me_unknown }, |
| }; |
| |
| static void action_result(unsigned long pfn, char *msg, int result) |
| { |
| struct page *page = pfn_to_page(pfn); |
| |
| printk(KERN_ERR "MCE %#lx: %s%s page recovery: %s\n", |
| pfn, |
| PageDirty(page) ? "dirty " : "", |
| msg, 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); |
| action_result(pfn, ps->msg, result); |
| |
| count = page_count(p) - 1; |
| if (ps->action == me_swapcache_dirty && result == DELAYED) |
| count--; |
| if (count != 0) { |
| printk(KERN_ERR |
| "MCE %#lx: %s page still referenced by %d users\n", |
| pfn, ps->msg, count); |
| result = FAILED; |
| } |
| |
| /* Could do more checks here if page looks ok */ |
| /* |
| * Could adjust zone counters here to correct for the missing page. |
| */ |
| |
| return (result == RECOVERED || result == DELAYED) ? 0 : -EBUSY; |
| } |
| |
| #define N_UNMAP_TRIES 5 |
| |
| /* |
| * Do all that is necessary to remove user space mappings. Unmap |
| * the pages and send SIGBUS to the processes if the data was dirty. |
| */ |
| static int hwpoison_user_mappings(struct page *p, unsigned long pfn, |
| int trapno) |
| { |
| enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS; |
| struct address_space *mapping; |
| LIST_HEAD(tokill); |
| int ret; |
| int i; |
| int kill = 1; |
| |
| if (PageReserved(p) || PageSlab(p)) |
| return SWAP_SUCCESS; |
| |
| /* |
| * This check implies we don't kill processes if their pages |
| * are in the swap cache early. Those are always late kills. |
| */ |
| if (!page_mapped(p)) |
| return SWAP_SUCCESS; |
| |
| if (PageCompound(p) || PageKsm(p)) |
| return SWAP_FAIL; |
| |
| if (PageSwapCache(p)) { |
| printk(KERN_ERR |
| "MCE %#lx: keeping poisoned page in swap cache\n", pfn); |
| ttu |= TTU_IGNORE_HWPOISON; |
| } |
| |
| /* |
| * Propagate the dirty bit from PTEs to struct page first, because we |
| * need this to decide if we should kill or just drop the page. |
| * XXX: the dirty test could be racy: set_page_dirty() may not always |
| * be called inside page lock (it's recommended but not enforced). |
| */ |
| mapping = page_mapping(p); |
| if (!PageDirty(p) && mapping && mapping_cap_writeback_dirty(mapping)) { |
| if (page_mkclean(p)) { |
| SetPageDirty(p); |
| } else { |
| kill = 0; |
| ttu |= TTU_IGNORE_HWPOISON; |
| printk(KERN_INFO |
| "MCE %#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(p, &tokill); |
| |
| /* |
| * try_to_unmap can fail temporarily due to races. |
| * Try a few times (RED-PEN better strategy?) |
| */ |
| for (i = 0; i < N_UNMAP_TRIES; i++) { |
| ret = try_to_unmap(p, ttu); |
| if (ret == SWAP_SUCCESS) |
| break; |
| pr_debug("MCE %#lx: try_to_unmap retry needed %d\n", pfn, ret); |
| } |
| |
| if (ret != SWAP_SUCCESS) |
| printk(KERN_ERR "MCE %#lx: failed to unmap page (mapcount=%d)\n", |
| pfn, page_mapcount(p)); |
| |
| /* |
| * 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, 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. |
| */ |
| kill_procs_ao(&tokill, !!PageDirty(p), trapno, |
| ret != SWAP_SUCCESS, pfn); |
| |
| return ret; |
| } |
| |
| int __memory_failure(unsigned long pfn, int trapno, int flags) |
| { |
| struct page_state *ps; |
| struct page *p; |
| int res; |
| |
| if (!sysctl_memory_failure_recovery) |
| panic("Memory failure from trap %d on page %lx", trapno, pfn); |
| |
| if (!pfn_valid(pfn)) { |
| printk(KERN_ERR |
| "MCE %#lx: memory outside kernel control\n", |
| pfn); |
| return -ENXIO; |
| } |
| |
| p = pfn_to_page(pfn); |
| if (TestSetPageHWPoison(p)) { |
| printk(KERN_ERR "MCE %#lx: already hardware poisoned\n", pfn); |
| return 0; |
| } |
| |
| atomic_long_add(1, &mce_bad_pages); |
| |
| /* |
| * We need/can do nothing about count=0 pages. |
| * 1) it's a free page, and therefore in safe hand: |
| * prep_new_page() will be the gate keeper. |
| * 2) it's part of a non-compound high order page. |
| * Implies some kernel user: cannot stop them from |
| * R/W the page; let's pray that the page has been |
| * used and will be freed some time later. |
| * In fact it's dangerous to directly bump up page count from 0, |
| * that may make page_freeze_refs()/page_unfreeze_refs() mismatch. |
| */ |
| if (!(flags & MF_COUNT_INCREASED) && |
| !get_page_unless_zero(compound_head(p))) { |
| if (is_free_buddy_page(p)) { |
| action_result(pfn, "free buddy", DELAYED); |
| return 0; |
| } else { |
| action_result(pfn, "high order kernel", IGNORED); |
| return -EBUSY; |
| } |
| } |
| |
| /* |
| * We ignore non-LRU pages for good reasons. |
| * - PG_locked is only well defined for LRU pages and a few others |
| * - to avoid races with __set_page_locked() |
| * - to avoid races with __SetPageSlab*() (and more non-atomic ops) |
| * The check (unnecessarily) ignores LRU pages being isolated and |
| * walked by the page reclaim code, however that's not a big loss. |
| */ |
| if (!PageLRU(p)) |
| lru_add_drain_all(); |
| if (!PageLRU(p)) { |
| action_result(pfn, "non LRU", IGNORED); |
| put_page(p); |
| return -EBUSY; |
| } |
| |
| /* |
| * Lock the page and wait for writeback to finish. |
| * It's very difficult to mess with pages currently under IO |
| * and in many cases impossible, so we just avoid it here. |
| */ |
| lock_page_nosync(p); |
| |
| /* |
| * unpoison always clear PG_hwpoison inside page lock |
| */ |
| if (!PageHWPoison(p)) { |
| printk(KERN_ERR "MCE %#lx: just unpoisoned\n", pfn); |
| res = 0; |
| goto out; |
| } |
| if (hwpoison_filter(p)) { |
| if (TestClearPageHWPoison(p)) |
| atomic_long_dec(&mce_bad_pages); |
| unlock_page(p); |
| put_page(p); |
| return 0; |
| } |
| |
| wait_on_page_writeback(p); |
| |
| /* |
| * Now take care of user space mappings. |
| * Abort on fail: __remove_from_page_cache() assumes unmapped page. |
| */ |
| if (hwpoison_user_mappings(p, pfn, trapno) != SWAP_SUCCESS) { |
| printk(KERN_ERR "MCE %#lx: cannot unmap page, give up\n", pfn); |
| res = -EBUSY; |
| goto out; |
| } |
| |
| /* |
| * Torn down by someone else? |
| */ |
| if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) { |
| action_result(pfn, "already truncated LRU", IGNORED); |
| res = -EBUSY; |
| goto out; |
| } |
| |
| res = -EBUSY; |
| for (ps = error_states;; ps++) { |
| if ((p->flags & ps->mask) == ps->res) { |
| res = page_action(ps, p, pfn); |
| break; |
| } |
| } |
| out: |
| unlock_page(p); |
| return res; |
| } |
| EXPORT_SYMBOL_GPL(__memory_failure); |
| |
| /** |
| * memory_failure - Handle memory failure of a page. |
| * @pfn: Page Number of the corrupted page |
| * @trapno: Trap number reported in the signal to user space. |
| * |
| * 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. |
| */ |
| void memory_failure(unsigned long pfn, int trapno) |
| { |
| __memory_failure(pfn, trapno, 0); |
| } |
| |
| /** |
| * 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; |
| |
| if (!pfn_valid(pfn)) |
| return -ENXIO; |
| |
| p = pfn_to_page(pfn); |
| page = compound_head(p); |
| |
| if (!PageHWPoison(p)) { |
| pr_debug("MCE: Page was already unpoisoned %#lx\n", pfn); |
| return 0; |
| } |
| |
| if (!get_page_unless_zero(page)) { |
| if (TestClearPageHWPoison(p)) |
| atomic_long_dec(&mce_bad_pages); |
| pr_debug("MCE: Software-unpoisoned free page %#lx\n", pfn); |
| return 0; |
| } |
| |
| lock_page_nosync(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(p)) { |
| pr_debug("MCE: Software-unpoisoned page %#lx\n", pfn); |
| atomic_long_dec(&mce_bad_pages); |
| freeit = 1; |
| } |
| unlock_page(page); |
| |
| put_page(page); |
| if (freeit) |
| put_page(page); |
| |
| return 0; |
| } |
| EXPORT_SYMBOL(unpoison_memory); |