![Rik van Riel](/assets/img/avatar_default.png)
The old anon_vma code can lead to scalability issues with heavily forking workloads. Specifically, each anon_vma will be shared between the parent process and all its child processes. In a workload with 1000 child processes and a VMA with 1000 anonymous pages per process that get COWed, this leads to a system with a million anonymous pages in the same anon_vma, each of which is mapped in just one of the 1000 processes. However, the current rmap code needs to walk them all, leading to O(N) scanning complexity for each page. This can result in systems where one CPU is walking the page tables of 1000 processes in page_referenced_one, while all other CPUs are stuck on the anon_vma lock. This leads to catastrophic failure for a benchmark like AIM7, where the total number of processes can reach in the tens of thousands. Real workloads are still a factor 10 less process intensive than AIM7, but they are catching up. This patch changes the way anon_vmas and VMAs are linked, which allows us to associate multiple anon_vmas with a VMA. At fork time, each child process gets its own anon_vmas, in which its COWed pages will be instantiated. The parents' anon_vma is also linked to the VMA, because non-COWed pages could be present in any of the children. This reduces rmap scanning complexity to O(1) for the pages of the 1000 child processes, with O(N) complexity for at most 1/N pages in the system. This reduces the average scanning cost in heavily forking workloads from O(N) to 2. The only real complexity in this patch stems from the fact that linking a VMA to anon_vmas now involves memory allocations. This means vma_adjust can fail, if it needs to attach a VMA to anon_vma structures. This in turn means error handling needs to be added to the calling functions. A second source of complexity is that, because there can be multiple anon_vmas, the anon_vma linking in vma_adjust can no longer be done under "the" anon_vma lock. To prevent the rmap code from walking up an incomplete VMA, this patch introduces the VM_LOCK_RMAP VMA flag. This bit flag uses the same slot as the NOMMU VM_MAPPED_COPY, with an ifdef in mm.h to make sure it is impossible to compile a kernel that needs both symbolic values for the same bitflag. Some test results: Without the anon_vma changes, when AIM7 hits around 9.7k users (on a test box with 16GB RAM and not quite enough IO), the system ends up running >99% in system time, with every CPU on the same anon_vma lock in the pageout code. With these changes, AIM7 hits the cross-over point around 29.7k users. This happens with ~99% IO wait time, there never seems to be any spike in system time. The anon_vma lock contention appears to be resolved. [akpm@linux-foundation.org: cleanups] Signed-off-by: Rik van Riel <riel@redhat.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Larry Woodman <lwoodman@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com> Cc: Minchan Kim <minchan.kim@gmail.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1298 lines
34 KiB
C
1298 lines
34 KiB
C
/*
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* Copyright (C) 2008, 2009 Intel Corporation
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* Authors: Andi Kleen, Fengguang Wu
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*
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* This software may be redistributed and/or modified under the terms of
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* the GNU General Public License ("GPL") version 2 only as published by the
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* Free Software Foundation.
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*
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* High level machine check handler. Handles pages reported by the
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* hardware as being corrupted usually due to a 2bit ECC memory or cache
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* failure.
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*
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* Handles page cache pages in various states. The tricky part
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* here is that we can access any page asynchronous to other VM
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* users, because memory failures could happen anytime and anywhere,
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* possibly violating some of their assumptions. This is why this code
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* has to be extremely careful. Generally it tries to use normal locking
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* rules, as in get the standard locks, even if that means the
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* error handling takes potentially a long time.
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*
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* The operation to map back from RMAP chains to processes has to walk
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* the complete process list and has non linear complexity with the number
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* mappings. In short it can be quite slow. But since memory corruptions
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* are rare we hope to get away with this.
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*/
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/*
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* Notebook:
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* - hugetlb needs more code
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* - kcore/oldmem/vmcore/mem/kmem check for hwpoison pages
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* - pass bad pages to kdump next kernel
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*/
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#define DEBUG 1 /* remove me in 2.6.34 */
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <linux/page-flags.h>
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#include <linux/kernel-page-flags.h>
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#include <linux/sched.h>
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#include <linux/ksm.h>
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#include <linux/rmap.h>
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#include <linux/pagemap.h>
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#include <linux/swap.h>
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#include <linux/backing-dev.h>
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#include <linux/migrate.h>
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#include <linux/page-isolation.h>
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#include <linux/suspend.h>
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#include "internal.h"
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int sysctl_memory_failure_early_kill __read_mostly = 0;
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int sysctl_memory_failure_recovery __read_mostly = 1;
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atomic_long_t mce_bad_pages __read_mostly = ATOMIC_LONG_INIT(0);
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#if defined(CONFIG_HWPOISON_INJECT) || defined(CONFIG_HWPOISON_INJECT_MODULE)
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u32 hwpoison_filter_enable = 0;
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u32 hwpoison_filter_dev_major = ~0U;
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u32 hwpoison_filter_dev_minor = ~0U;
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u64 hwpoison_filter_flags_mask;
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u64 hwpoison_filter_flags_value;
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EXPORT_SYMBOL_GPL(hwpoison_filter_enable);
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EXPORT_SYMBOL_GPL(hwpoison_filter_dev_major);
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EXPORT_SYMBOL_GPL(hwpoison_filter_dev_minor);
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EXPORT_SYMBOL_GPL(hwpoison_filter_flags_mask);
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EXPORT_SYMBOL_GPL(hwpoison_filter_flags_value);
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static int hwpoison_filter_dev(struct page *p)
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{
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struct address_space *mapping;
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dev_t dev;
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if (hwpoison_filter_dev_major == ~0U &&
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hwpoison_filter_dev_minor == ~0U)
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return 0;
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/*
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* page_mapping() does not accept slab page
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*/
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if (PageSlab(p))
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return -EINVAL;
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mapping = page_mapping(p);
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if (mapping == NULL || mapping->host == NULL)
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return -EINVAL;
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dev = mapping->host->i_sb->s_dev;
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if (hwpoison_filter_dev_major != ~0U &&
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hwpoison_filter_dev_major != MAJOR(dev))
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return -EINVAL;
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if (hwpoison_filter_dev_minor != ~0U &&
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hwpoison_filter_dev_minor != MINOR(dev))
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return -EINVAL;
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return 0;
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}
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static int hwpoison_filter_flags(struct page *p)
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{
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if (!hwpoison_filter_flags_mask)
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return 0;
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if ((stable_page_flags(p) & hwpoison_filter_flags_mask) ==
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hwpoison_filter_flags_value)
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return 0;
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else
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return -EINVAL;
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}
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/*
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* This allows stress tests to limit test scope to a collection of tasks
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* by putting them under some memcg. This prevents killing unrelated/important
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* processes such as /sbin/init. Note that the target task may share clean
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* pages with init (eg. libc text), which is harmless. If the target task
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* share _dirty_ pages with another task B, the test scheme must make sure B
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* is also included in the memcg. At last, due to race conditions this filter
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* can only guarantee that the page either belongs to the memcg tasks, or is
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* a freed page.
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*/
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#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
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u64 hwpoison_filter_memcg;
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EXPORT_SYMBOL_GPL(hwpoison_filter_memcg);
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static int hwpoison_filter_task(struct page *p)
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{
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struct mem_cgroup *mem;
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struct cgroup_subsys_state *css;
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unsigned long ino;
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if (!hwpoison_filter_memcg)
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return 0;
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mem = try_get_mem_cgroup_from_page(p);
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if (!mem)
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return -EINVAL;
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css = mem_cgroup_css(mem);
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/* root_mem_cgroup has NULL dentries */
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if (!css->cgroup->dentry)
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return -EINVAL;
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ino = css->cgroup->dentry->d_inode->i_ino;
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css_put(css);
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if (ino != hwpoison_filter_memcg)
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return -EINVAL;
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return 0;
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}
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#else
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static int hwpoison_filter_task(struct page *p) { return 0; }
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#endif
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int hwpoison_filter(struct page *p)
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{
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if (!hwpoison_filter_enable)
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return 0;
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if (hwpoison_filter_dev(p))
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return -EINVAL;
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if (hwpoison_filter_flags(p))
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return -EINVAL;
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if (hwpoison_filter_task(p))
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return -EINVAL;
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return 0;
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}
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#else
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int hwpoison_filter(struct page *p)
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{
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return 0;
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}
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#endif
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EXPORT_SYMBOL_GPL(hwpoison_filter);
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/*
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* Send all the processes who have the page mapped an ``action optional''
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* signal.
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*/
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static int kill_proc_ao(struct task_struct *t, unsigned long addr, int trapno,
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unsigned long pfn)
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{
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struct siginfo si;
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int ret;
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printk(KERN_ERR
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"MCE %#lx: Killing %s:%d early due to hardware memory corruption\n",
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pfn, t->comm, t->pid);
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si.si_signo = SIGBUS;
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si.si_errno = 0;
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si.si_code = BUS_MCEERR_AO;
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si.si_addr = (void *)addr;
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#ifdef __ARCH_SI_TRAPNO
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si.si_trapno = trapno;
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#endif
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si.si_addr_lsb = PAGE_SHIFT;
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/*
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* Don't use force here, it's convenient if the signal
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* can be temporarily blocked.
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* This could cause a loop when the user sets SIGBUS
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* to SIG_IGN, but hopefully noone will do that?
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*/
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ret = send_sig_info(SIGBUS, &si, t); /* synchronous? */
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if (ret < 0)
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printk(KERN_INFO "MCE: Error sending signal to %s:%d: %d\n",
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t->comm, t->pid, ret);
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return ret;
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}
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/*
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* When a unknown page type is encountered drain as many buffers as possible
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* in the hope to turn the page into a LRU or free page, which we can handle.
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*/
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void shake_page(struct page *p, int access)
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{
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if (!PageSlab(p)) {
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lru_add_drain_all();
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if (PageLRU(p))
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return;
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drain_all_pages();
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if (PageLRU(p) || is_free_buddy_page(p))
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return;
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}
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/*
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* Only all shrink_slab here (which would also
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* shrink other caches) if access is not potentially fatal.
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*/
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if (access) {
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int nr;
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do {
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nr = shrink_slab(1000, GFP_KERNEL, 1000);
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if (page_count(p) == 0)
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break;
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} while (nr > 10);
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}
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}
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EXPORT_SYMBOL_GPL(shake_page);
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/*
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* Kill all processes that have a poisoned page mapped and then isolate
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* the page.
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*
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* General strategy:
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* Find all processes having the page mapped and kill them.
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* But we keep a page reference around so that the page is not
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* actually freed yet.
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* Then stash the page away
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*
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* There's no convenient way to get back to mapped processes
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* from the VMAs. So do a brute-force search over all
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* running processes.
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*
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* Remember that machine checks are not common (or rather
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* if they are common you have other problems), so this shouldn't
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* be a performance issue.
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*
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* Also there are some races possible while we get from the
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* error detection to actually handle it.
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*/
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struct to_kill {
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struct list_head nd;
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struct task_struct *tsk;
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unsigned long addr;
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unsigned addr_valid:1;
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};
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/*
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* Failure handling: if we can't find or can't kill a process there's
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* not much we can do. We just print a message and ignore otherwise.
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*/
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/*
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* Schedule a process for later kill.
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* Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
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* TBD would GFP_NOIO be enough?
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*/
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static void add_to_kill(struct task_struct *tsk, struct page *p,
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struct vm_area_struct *vma,
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struct list_head *to_kill,
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struct to_kill **tkc)
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{
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struct to_kill *tk;
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if (*tkc) {
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tk = *tkc;
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*tkc = NULL;
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} else {
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tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
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if (!tk) {
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printk(KERN_ERR
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"MCE: Out of memory while machine check handling\n");
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return;
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}
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}
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tk->addr = page_address_in_vma(p, vma);
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tk->addr_valid = 1;
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/*
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* In theory we don't have to kill when the page was
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* munmaped. But it could be also a mremap. Since that's
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* likely very rare kill anyways just out of paranoia, but use
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* a SIGKILL because the error is not contained anymore.
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*/
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if (tk->addr == -EFAULT) {
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pr_debug("MCE: Unable to find user space address %lx in %s\n",
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page_to_pfn(p), tsk->comm);
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tk->addr_valid = 0;
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}
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get_task_struct(tsk);
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tk->tsk = tsk;
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list_add_tail(&tk->nd, to_kill);
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}
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/*
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* Kill the processes that have been collected earlier.
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*
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* Only do anything when DOIT is set, otherwise just free the list
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* (this is used for clean pages which do not need killing)
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* Also when FAIL is set do a force kill because something went
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* wrong earlier.
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*/
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static void kill_procs_ao(struct list_head *to_kill, int doit, int trapno,
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int fail, unsigned long pfn)
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{
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struct to_kill *tk, *next;
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list_for_each_entry_safe (tk, next, to_kill, nd) {
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if (doit) {
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/*
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* In case something went wrong with munmapping
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* make sure the process doesn't catch the
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* signal and then access the memory. Just kill it.
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*/
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if (fail || tk->addr_valid == 0) {
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printk(KERN_ERR
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"MCE %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n",
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pfn, tk->tsk->comm, tk->tsk->pid);
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force_sig(SIGKILL, tk->tsk);
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}
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/*
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* In theory the process could have mapped
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* something else on the address in-between. We could
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* check for that, but we need to tell the
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* process anyways.
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*/
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else if (kill_proc_ao(tk->tsk, tk->addr, trapno,
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pfn) < 0)
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printk(KERN_ERR
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"MCE %#lx: Cannot send advisory machine check signal to %s:%d\n",
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pfn, tk->tsk->comm, tk->tsk->pid);
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}
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put_task_struct(tk->tsk);
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kfree(tk);
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}
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}
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static int task_early_kill(struct task_struct *tsk)
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{
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if (!tsk->mm)
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return 0;
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if (tsk->flags & PF_MCE_PROCESS)
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return !!(tsk->flags & PF_MCE_EARLY);
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return sysctl_memory_failure_early_kill;
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}
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/*
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* Collect processes when the error hit an anonymous page.
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*/
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static void collect_procs_anon(struct page *page, struct list_head *to_kill,
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struct to_kill **tkc)
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{
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struct vm_area_struct *vma;
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struct task_struct *tsk;
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struct anon_vma *av;
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read_lock(&tasklist_lock);
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av = page_lock_anon_vma(page);
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if (av == NULL) /* Not actually mapped anymore */
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goto out;
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for_each_process (tsk) {
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struct anon_vma_chain *vmac;
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if (!task_early_kill(tsk))
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continue;
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list_for_each_entry(vmac, &av->head, same_anon_vma) {
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vma = vmac->vma;
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if (!page_mapped_in_vma(page, vma))
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continue;
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if (vma->vm_mm == tsk->mm)
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add_to_kill(tsk, page, vma, to_kill, tkc);
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}
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}
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page_unlock_anon_vma(av);
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out:
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read_unlock(&tasklist_lock);
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}
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/*
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* Collect processes when the error hit a file mapped page.
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*/
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static void collect_procs_file(struct page *page, struct list_head *to_kill,
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struct to_kill **tkc)
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{
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struct vm_area_struct *vma;
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struct task_struct *tsk;
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struct prio_tree_iter iter;
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struct address_space *mapping = page->mapping;
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/*
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* A note on the locking order between the two locks.
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* We don't rely on this particular order.
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* If you have some other code that needs a different order
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* feel free to switch them around. Or add a reverse link
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* from mm_struct to task_struct, then this could be all
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* done without taking tasklist_lock and looping over all tasks.
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*/
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read_lock(&tasklist_lock);
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spin_lock(&mapping->i_mmap_lock);
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for_each_process(tsk) {
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pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
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if (!task_early_kill(tsk))
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continue;
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vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff,
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pgoff) {
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/*
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* Send early kill signal to tasks where a vma covers
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* the page but the corrupted page is not necessarily
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* mapped it in its pte.
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* Assume applications who requested early kill want
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* to be informed of all such data corruptions.
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*/
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if (vma->vm_mm == tsk->mm)
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add_to_kill(tsk, page, vma, to_kill, tkc);
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}
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}
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spin_unlock(&mapping->i_mmap_lock);
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read_unlock(&tasklist_lock);
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}
|
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|
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/*
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* Collect the processes who have the corrupted page mapped to kill.
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* This is done in two steps for locking reasons.
|
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* First preallocate one tokill structure outside the spin locks,
|
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* so that we can kill at least one process reasonably reliable.
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*/
|
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static void collect_procs(struct page *page, struct list_head *tokill)
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{
|
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struct to_kill *tk;
|
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|
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if (!page->mapping)
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return;
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|
|
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tk = kmalloc(sizeof(struct to_kill), GFP_NOIO);
|
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if (!tk)
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return;
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if (PageAnon(page))
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collect_procs_anon(page, tokill, &tk);
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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 },
|
|
};
|
|
|
|
#undef dirty
|
|
#undef sc
|
|
#undef unevict
|
|
#undef mlock
|
|
#undef writeback
|
|
#undef lru
|
|
#undef swapbacked
|
|
#undef head
|
|
#undef tail
|
|
#undef compound
|
|
#undef slab
|
|
#undef reserved
|
|
|
|
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))
|
|
shake_page(p, 0);
|
|
if (!PageLRU(p)) {
|
|
/*
|
|
* shake_page could have turned it free.
|
|
*/
|
|
if (is_free_buddy_page(p)) {
|
|
action_result(pfn, "free buddy, 2nd try", DELAYED);
|
|
return 0;
|
|
}
|
|
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);
|
|
|
|
static struct page *new_page(struct page *p, unsigned long private, int **x)
|
|
{
|
|
int nid = page_to_nid(p);
|
|
return alloc_pages_exact_node(nid, GFP_HIGHUSER_MOVABLE, 0);
|
|
}
|
|
|
|
/*
|
|
* Safely get reference count of an arbitrary page.
|
|
* Returns 0 for a free page, -EIO for a zero refcount page
|
|
* that is not free, and 1 for any other page type.
|
|
* For 1 the page is returned with increased page count, otherwise not.
|
|
*/
|
|
static int get_any_page(struct page *p, unsigned long pfn, int flags)
|
|
{
|
|
int ret;
|
|
|
|
if (flags & MF_COUNT_INCREASED)
|
|
return 1;
|
|
|
|
/*
|
|
* The lock_system_sleep prevents a race with memory hotplug,
|
|
* because the isolation assumes there's only a single user.
|
|
* This is a big hammer, a better would be nicer.
|
|
*/
|
|
lock_system_sleep();
|
|
|
|
/*
|
|
* Isolate the page, so that it doesn't get reallocated if it
|
|
* was free.
|
|
*/
|
|
set_migratetype_isolate(p);
|
|
if (!get_page_unless_zero(compound_head(p))) {
|
|
if (is_free_buddy_page(p)) {
|
|
pr_debug("get_any_page: %#lx free buddy page\n", pfn);
|
|
/* Set hwpoison bit while page is still isolated */
|
|
SetPageHWPoison(p);
|
|
ret = 0;
|
|
} else {
|
|
pr_debug("get_any_page: %#lx: unknown zero refcount page type %lx\n",
|
|
pfn, p->flags);
|
|
ret = -EIO;
|
|
}
|
|
} else {
|
|
/* Not a free page */
|
|
ret = 1;
|
|
}
|
|
unset_migratetype_isolate(p);
|
|
unlock_system_sleep();
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* soft_offline_page - Soft offline a page.
|
|
* @page: page to offline
|
|
* @flags: flags. Same as memory_failure().
|
|
*
|
|
* Returns 0 on success, otherwise negated errno.
|
|
*
|
|
* Soft offline a page, by migration or invalidation,
|
|
* without killing anything. This is for the case when
|
|
* a page is not corrupted yet (so it's still valid to access),
|
|
* but has had a number of corrected errors and is better taken
|
|
* out.
|
|
*
|
|
* The actual policy on when to do that is maintained by
|
|
* user space.
|
|
*
|
|
* This should never impact any application or cause data loss,
|
|
* however it might take some time.
|
|
*
|
|
* This is not a 100% solution for all memory, but tries to be
|
|
* ``good enough'' for the majority of memory.
|
|
*/
|
|
int soft_offline_page(struct page *page, int flags)
|
|
{
|
|
int ret;
|
|
unsigned long pfn = page_to_pfn(page);
|
|
|
|
ret = get_any_page(page, pfn, flags);
|
|
if (ret < 0)
|
|
return ret;
|
|
if (ret == 0)
|
|
goto done;
|
|
|
|
/*
|
|
* Page cache page we can handle?
|
|
*/
|
|
if (!PageLRU(page)) {
|
|
/*
|
|
* Try to free it.
|
|
*/
|
|
put_page(page);
|
|
shake_page(page, 1);
|
|
|
|
/*
|
|
* Did it turn free?
|
|
*/
|
|
ret = get_any_page(page, pfn, 0);
|
|
if (ret < 0)
|
|
return ret;
|
|
if (ret == 0)
|
|
goto done;
|
|
}
|
|
if (!PageLRU(page)) {
|
|
pr_debug("soft_offline: %#lx: unknown non LRU page type %lx\n",
|
|
pfn, page->flags);
|
|
return -EIO;
|
|
}
|
|
|
|
lock_page(page);
|
|
wait_on_page_writeback(page);
|
|
|
|
/*
|
|
* Synchronized using the page lock with memory_failure()
|
|
*/
|
|
if (PageHWPoison(page)) {
|
|
unlock_page(page);
|
|
put_page(page);
|
|
pr_debug("soft offline: %#lx page already poisoned\n", pfn);
|
|
return -EBUSY;
|
|
}
|
|
|
|
/*
|
|
* Try to invalidate first. This should work for
|
|
* non dirty unmapped page cache pages.
|
|
*/
|
|
ret = invalidate_inode_page(page);
|
|
unlock_page(page);
|
|
|
|
/*
|
|
* Drop count because page migration doesn't like raised
|
|
* counts. The page could get re-allocated, but if it becomes
|
|
* LRU the isolation will just fail.
|
|
* RED-PEN would be better to keep it isolated here, but we
|
|
* would need to fix isolation locking first.
|
|
*/
|
|
put_page(page);
|
|
if (ret == 1) {
|
|
ret = 0;
|
|
pr_debug("soft_offline: %#lx: invalidated\n", pfn);
|
|
goto done;
|
|
}
|
|
|
|
/*
|
|
* Simple invalidation didn't work.
|
|
* Try to migrate to a new page instead. migrate.c
|
|
* handles a large number of cases for us.
|
|
*/
|
|
ret = isolate_lru_page(page);
|
|
if (!ret) {
|
|
LIST_HEAD(pagelist);
|
|
|
|
list_add(&page->lru, &pagelist);
|
|
ret = migrate_pages(&pagelist, new_page, MPOL_MF_MOVE_ALL, 0);
|
|
if (ret) {
|
|
pr_debug("soft offline: %#lx: migration failed %d, type %lx\n",
|
|
pfn, ret, page->flags);
|
|
if (ret > 0)
|
|
ret = -EIO;
|
|
}
|
|
} else {
|
|
pr_debug("soft offline: %#lx: isolation failed: %d, page count %d, type %lx\n",
|
|
pfn, ret, page_count(page), page->flags);
|
|
}
|
|
if (ret)
|
|
return ret;
|
|
|
|
done:
|
|
atomic_long_add(1, &mce_bad_pages);
|
|
SetPageHWPoison(page);
|
|
/* keep elevated page count for bad page */
|
|
return ret;
|
|
}
|