linux/mm/memory-failure.c
Yang Shi d0505e9f7d mm: hwpoison: don't drop slab caches for offlining non-LRU page
In the current implementation of soft offline, if non-LRU page is met,
all the slab caches will be dropped to free the page then offline.  But
if the page is not slab page all the effort is wasted in vain.  Even
though it is a slab page, it is not guaranteed the page could be freed
at all.

However the side effect and cost is quite high.  It does not only drop
the slab caches, but also may drop a significant amount of page caches
which are associated with inode caches.  It could make the most
workingset gone in order to just offline a page.  And the offline is not
guaranteed to succeed at all, actually I really doubt the success rate
for real life workload.

Furthermore the worse consequence is the system may be locked up and
unusable since the page cache release may incur huge amount of works
queued for memcg release.

Actually we ran into such unpleasant case in our production environment.
Firstly, the workqueue of memory_failure_work_func is locked up as
below:

    BUG: workqueue lockup - pool cpus=1 node=0 flags=0x0 nice=0 stuck for 53s!
    Showing busy workqueues and worker pools:
    workqueue events: flags=0x0
     pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=14/256 refcnt=15
      in-flight: 409271:memory_failure_work_func
      pending: kfree_rcu_work, kfree_rcu_monitor, kfree_rcu_work, rht_deferred_worker, rht_deferred_worker, rht_deferred_worker, rht_deferred_worker, kfree_rcu_work, kfree_rcu_work, kfree_rcu_work, kfree_rcu_work, drain_local_stock, kfree_rcu_work
    workqueue mm_percpu_wq: flags=0x8
     pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/256 refcnt=2
      pending: vmstat_update
    workqueue cgroup_destroy: flags=0x0
      pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/1 refcnt=12072
        pending: css_release_work_fn

There were over 12K css_release_work_fn queued, and this caused a few
lockups due to the contention of worker pool lock with IRQ disabled, for
example:

    NMI watchdog: Watchdog detected hard LOCKUP on cpu 1
    Modules linked in: amd64_edac_mod edac_mce_amd crct10dif_pclmul crc32_pclmul ghash_clmulni_intel xt_DSCP iptable_mangle kvm_amd bpfilter vfat fat acpi_ipmi i2c_piix4 usb_storage ipmi_si k10temp i2c_core ipmi_devintf ipmi_msghandler acpi_cpufreq sch_fq_codel xfs libcrc32c crc32c_intel mlx5_core mlxfw nvme xhci_pci ptp nvme_core pps_core xhci_hcd
    CPU: 1 PID: 205500 Comm: kworker/1:0 Tainted: G             L    5.10.32-t1.el7.twitter.x86_64 #1
    Hardware name: TYAN F5AMT /z        /S8026GM2NRE-CGN, BIOS V8.030 03/30/2021
    Workqueue: events memory_failure_work_func
    RIP: 0010:queued_spin_lock_slowpath+0x41/0x1a0
    Code: 41 f0 0f ba 2f 08 0f 92 c0 0f b6 c0 c1 e0 08 89 c2 8b 07 30 e4 09 d0 a9 00 01 ff ff 75 1b 85 c0 74 0e 8b 07 84 c0 74 08 f3 90 <8b> 07 84 c0 75 f8 b8 01 00 00 00 66 89 07 c3 f6 c4 01 75 04 c6 47
    RSP: 0018:ffff9b2ac278f900 EFLAGS: 00000002
    RAX: 0000000000480101 RBX: ffff8ce98ce71800 RCX: 0000000000000084
    RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8ce98ce6a140
    RBP: 00000000000284c8 R08: ffffd7248dcb6808 R09: 0000000000000000
    R10: 0000000000000003 R11: ffff9b2ac278f9b0 R12: 0000000000000001
    R13: ffff8cb44dab9c00 R14: ffffffffbd1ce6a0 R15: ffff8cacaa37f068
    FS:  0000000000000000(0000) GS:ffff8ce98ce40000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 00007fcf6e8cb000 CR3: 0000000a0c60a000 CR4: 0000000000350ee0
    Call Trace:
     __queue_work+0xd6/0x3c0
     queue_work_on+0x1c/0x30
     uncharge_batch+0x10e/0x110
     mem_cgroup_uncharge_list+0x6d/0x80
     release_pages+0x37f/0x3f0
     __pagevec_release+0x1c/0x50
     __invalidate_mapping_pages+0x348/0x380
     inode_lru_isolate+0x10a/0x160
     __list_lru_walk_one+0x7b/0x170
     list_lru_walk_one+0x4a/0x60
     prune_icache_sb+0x37/0x50
     super_cache_scan+0x123/0x1a0
     do_shrink_slab+0x10c/0x2c0
     shrink_slab+0x1f1/0x290
     drop_slab_node+0x4d/0x70
     soft_offline_page+0x1ac/0x5b0
     memory_failure_work_func+0x6a/0x90
     process_one_work+0x19e/0x340
     worker_thread+0x30/0x360
     kthread+0x116/0x130

The lockup made the machine is quite unusable.  And it also made the
most workingset gone, the reclaimabled slab caches were reduced from 12G
to 300MB, the page caches were decreased from 17G to 4G.

But the most disappointing thing is all the effort doesn't make the page
offline, it just returns:

    soft_offline: 0x1469f2: unknown non LRU page type 5ffff0000000000 ()

It seems the aggressive behavior for non-LRU page didn't pay back, so it
doesn't make too much sense to keep it considering the terrible side
effect.

Link: https://lkml.kernel.org/r/20210819054116.266126-1-shy828301@gmail.com
Signed-off-by: Yang Shi <shy828301@gmail.com>
Reported-by: David Mackey <tdmackey@twitter.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-09-03 09:58:15 -07:00

2215 lines
59 KiB
C

// 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 <linux/pagewalk.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 ret;
zone_pcp_disable(page_zone(page));
ret = dissolve_free_huge_page(page);
if (!ret)
ret = take_page_off_buddy(page);
zone_pcp_enable(page_zone(page));
return ret;
}
static bool page_handle_poison(struct page *page, bool hugepage_or_freepage, bool release)
{
if (hugepage_or_freepage) {
/*
* Doing this check for free pages is also fine since dissolve_free_huge_page
* returns 0 for non-hugetlb pages as well.
*/
if (!__page_handle_poison(page))
/*
* We could fail to take off the target page from buddy
* for example due to racy page allocation, but that's
* acceptable because soft-offlined page is not broken
* and if someone really want to use it, they should
* take it.
*/
return false;
}
SetPageHWPoison(page);
if (release)
put_page(page);
page_ref_inc(page);
num_poisoned_pages_inc();
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) {
if (t == current)
ret = force_sig_mceerr(BUS_MCEERR_AR,
(void __user *)tk->addr, addr_lsb);
else
/* Signal other processes sharing the page if they have PF_MCE_EARLY set. */
ret = send_sig_mceerr(BUS_MCEERR_AO, (void __user *)tk->addr,
addr_lsb, t);
} 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;
}
/*
* Unknown page type encountered. Try to check whether it can turn PageLRU by
* lru_add_drain_all.
*/
void shake_page(struct page *p)
{
if (PageHuge(p))
return;
if (!PageSlab(p)) {
lru_add_drain_all();
if (PageLRU(p) || is_free_buddy_page(p))
return;
}
/*
* TODO: Could shrink slab caches here if a lightweight range-based
* shrinker will be available.
*/
}
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 FORCEKILL is set, otherwise just free the
* list (this is used for clean pages which do not need killing)
* Also when FAIL is set do a force kill because something went
* wrong earlier.
*/
static void kill_procs(struct list_head *to_kill, int forcekill, bool fail,
unsigned long pfn, int flags)
{
struct to_kill *tk, *next;
list_for_each_entry_safe (tk, next, to_kill, nd) {
if (forcekill) {
/*
* In case something went wrong with munmapping
* make sure the process doesn't catch the
* signal and then access the memory. Just kill it.
*/
if (fail || tk->addr == -EFAULT) {
pr_err("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. For Action Required
* case, it's only meaningful to the current thread which need to be signaled
* with SIGBUS, this error is Action Optional for other non current
* processes sharing the same error page,if the process is "early kill", the
* task_struct of the dedicated thread will also be returned.
*/
static struct task_struct *task_early_kill(struct task_struct *tsk,
int force_early)
{
if (!tsk->mm)
return NULL;
/*
* Comparing ->mm here because current task might represent
* a subthread, while tsk always points to the main thread.
*/
if (force_early && tsk->mm == current->mm)
return current;
return find_early_kill_thread(tsk);
}
/*
* Collect processes when the error hit an anonymous page.
*/
static void collect_procs_anon(struct 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);
}
struct hwp_walk {
struct to_kill tk;
unsigned long pfn;
int flags;
};
static void set_to_kill(struct to_kill *tk, unsigned long addr, short shift)
{
tk->addr = addr;
tk->size_shift = shift;
}
static int check_hwpoisoned_entry(pte_t pte, unsigned long addr, short shift,
unsigned long poisoned_pfn, struct to_kill *tk)
{
unsigned long pfn = 0;
if (pte_present(pte)) {
pfn = pte_pfn(pte);
} else {
swp_entry_t swp = pte_to_swp_entry(pte);
if (is_hwpoison_entry(swp))
pfn = hwpoison_entry_to_pfn(swp);
}
if (!pfn || pfn != poisoned_pfn)
return 0;
set_to_kill(tk, addr, shift);
return 1;
}
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
static int check_hwpoisoned_pmd_entry(pmd_t *pmdp, unsigned long addr,
struct hwp_walk *hwp)
{
pmd_t pmd = *pmdp;
unsigned long pfn;
unsigned long hwpoison_vaddr;
if (!pmd_present(pmd))
return 0;
pfn = pmd_pfn(pmd);
if (pfn <= hwp->pfn && hwp->pfn < pfn + HPAGE_PMD_NR) {
hwpoison_vaddr = addr + ((hwp->pfn - pfn) << PAGE_SHIFT);
set_to_kill(&hwp->tk, hwpoison_vaddr, PAGE_SHIFT);
return 1;
}
return 0;
}
#else
static int check_hwpoisoned_pmd_entry(pmd_t *pmdp, unsigned long addr,
struct hwp_walk *hwp)
{
return 0;
}
#endif
static int hwpoison_pte_range(pmd_t *pmdp, unsigned long addr,
unsigned long end, struct mm_walk *walk)
{
struct hwp_walk *hwp = (struct hwp_walk *)walk->private;
int ret = 0;
pte_t *ptep, *mapped_pte;
spinlock_t *ptl;
ptl = pmd_trans_huge_lock(pmdp, walk->vma);
if (ptl) {
ret = check_hwpoisoned_pmd_entry(pmdp, addr, hwp);
spin_unlock(ptl);
goto out;
}
if (pmd_trans_unstable(pmdp))
goto out;
mapped_pte = ptep = pte_offset_map_lock(walk->vma->vm_mm, pmdp,
addr, &ptl);
for (; addr != end; ptep++, addr += PAGE_SIZE) {
ret = check_hwpoisoned_entry(*ptep, addr, PAGE_SHIFT,
hwp->pfn, &hwp->tk);
if (ret == 1)
break;
}
pte_unmap_unlock(mapped_pte, ptl);
out:
cond_resched();
return ret;
}
#ifdef CONFIG_HUGETLB_PAGE
static int hwpoison_hugetlb_range(pte_t *ptep, unsigned long hmask,
unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
struct hwp_walk *hwp = (struct hwp_walk *)walk->private;
pte_t pte = huge_ptep_get(ptep);
struct hstate *h = hstate_vma(walk->vma);
return check_hwpoisoned_entry(pte, addr, huge_page_shift(h),
hwp->pfn, &hwp->tk);
}
#else
#define hwpoison_hugetlb_range NULL
#endif
static struct mm_walk_ops hwp_walk_ops = {
.pmd_entry = hwpoison_pte_range,
.hugetlb_entry = hwpoison_hugetlb_range,
};
/*
* Sends SIGBUS to the current process with error info.
*
* This function is intended to handle "Action Required" MCEs on already
* hardware poisoned pages. They could happen, for example, when
* memory_failure() failed to unmap the error page at the first call, or
* when multiple local machine checks happened on different CPUs.
*
* MCE handler currently has no easy access to the error virtual address,
* so this function walks page table to find it. The returned virtual address
* is proper in most cases, but it could be wrong when the application
* process has multiple entries mapping the error page.
*/
static int kill_accessing_process(struct task_struct *p, unsigned long pfn,
int flags)
{
int ret;
struct hwp_walk priv = {
.pfn = pfn,
};
priv.tk.tsk = p;
mmap_read_lock(p->mm);
ret = walk_page_range(p->mm, 0, TASK_SIZE, &hwp_walk_ops,
(void *)&priv);
if (ret == 1 && priv.tk.addr)
kill_proc(&priv.tk, pfn, flags);
mmap_read_unlock(p->mm);
return ret ? -EFAULT : -EHWPOISON;
}
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)
{
unlock_page(p);
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);
unlock_page(p);
return MF_FAILED;
}
/*
* Clean (or cleaned) page cache page.
*/
static int me_pagecache_clean(struct page *p, unsigned long pfn)
{
int ret;
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)) {
ret = MF_RECOVERED;
goto out;
}
/*
* Now truncate the page in the page cache. This is really
* more like a "temporary hole punch"
* Don't do this for block devices when someone else
* has a reference, because it could be file system metadata
* and that's not safe to truncate.
*/
mapping = page_mapping(p);
if (!mapping) {
/*
* Page has been teared down in the meanwhile
*/
ret = MF_FAILED;
goto out;
}
/*
* 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.
*/
ret = truncate_error_page(p, pfn, mapping);
out:
unlock_page(p);
return ret;
}
/*
* Dirty pagecache page
* Issues: when the error hit a hole page the error is not properly
* propagated.
*/
static int me_pagecache_dirty(struct page *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)
{
int ret;
ClearPageDirty(p);
/* Trigger EIO in shmem: */
ClearPageUptodate(p);
ret = delete_from_lru_cache(p) ? MF_FAILED : MF_DELAYED;
unlock_page(p);
return ret;
}
static int me_swapcache_clean(struct page *p, unsigned long pfn)
{
int ret;
delete_from_swap_cache(p);
ret = delete_from_lru_cache(p) ? MF_FAILED : MF_RECOVERED;
unlock_page(p);
return ret;
}
/*
* Huge pages. Needs work.
* Issues:
* - Error on hugepage is contained in hugepage unit (not in raw page unit.)
* To narrow down kill region to one page, we need to break up pmd.
*/
static int me_huge_page(struct page *p, unsigned long pfn)
{
int res;
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);
unlock_page(hpage);
} else {
res = MF_FAILED;
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);
if (__page_handle_poison(p)) {
page_ref_inc(p);
res = MF_RECOVERED;
}
}
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;
/* Callback ->action() has to unlock the relevant page inside it. */
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;
/* page p should be unlocked after returning from ps->action(). */
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;
}
/*
* Return true if a page type of a given page is supported by hwpoison
* mechanism (while handling could fail), otherwise false. This function
* does not return true for hugetlb or device memory pages, so it's assumed
* to be called only in the context where we never have such pages.
*/
static inline bool HWPoisonHandlable(struct page *page)
{
return PageLRU(page) || __PageMovable(page);
}
static int __get_hwpoison_page(struct page *page)
{
struct page *head = compound_head(page);
int ret = 0;
bool hugetlb = false;
ret = get_hwpoison_huge_page(head, &hugetlb);
if (hugetlb)
return ret;
/*
* This check prevents from calling get_hwpoison_unless_zero()
* for any unsupported type of page in order to reduce the risk of
* unexpected races caused by taking a page refcount.
*/
if (!HWPoisonHandlable(head))
return -EBUSY;
if (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;
}
static int get_any_page(struct page *p, unsigned long flags)
{
int ret = 0, pass = 0;
bool count_increased = false;
if (flags & MF_COUNT_INCREASED)
count_increased = true;
try_again:
if (!count_increased) {
ret = __get_hwpoison_page(p);
if (!ret) {
if (page_count(p)) {
/* We raced with an allocation, retry. */
if (pass++ < 3)
goto try_again;
ret = -EBUSY;
} else if (!PageHuge(p) && !is_free_buddy_page(p)) {
/* We raced with put_page, retry. */
if (pass++ < 3)
goto try_again;
ret = -EIO;
}
goto out;
} else if (ret == -EBUSY) {
/*
* We raced with (possibly temporary) unhandlable
* page, retry.
*/
if (pass++ < 3) {
shake_page(p);
goto try_again;
}
ret = -EIO;
goto out;
}
}
if (PageHuge(p) || HWPoisonHandlable(p)) {
ret = 1;
} else {
/*
* A page we cannot handle. Check whether we can turn
* it into something we can handle.
*/
if (pass++ < 3) {
put_page(p);
shake_page(p);
count_increased = false;
goto try_again;
}
put_page(p);
ret = -EIO;
}
out:
return ret;
}
/**
* get_hwpoison_page() - Get refcount for memory error handling
* @p: Raw error page (hit by memory error)
* @flags: Flags controlling behavior of error handling
*
* get_hwpoison_page() takes a page refcount of an error page to handle memory
* error on it, after checking that the error page is in a well-defined state
* (defined as a page-type we can successfully handle the memor error on it,
* such as LRU page and hugetlb page).
*
* Memory error handling could be triggered at any time on any type of page,
* so it's prone to race with typical memory management lifecycle (like
* allocation and free). So to avoid such races, get_hwpoison_page() takes
* extra care for the error page's state (as done in __get_hwpoison_page()),
* and has some retry logic in get_any_page().
*
* Return: 0 on failure,
* 1 on success for in-use pages in a well-defined state,
* -EIO for pages on which we can not handle memory errors,
* -EBUSY when get_hwpoison_page() has raced with page lifecycle
* operations like allocation and free.
*/
static int get_hwpoison_page(struct page *p, unsigned long flags)
{
int ret;
zone_pcp_disable(page_zone(p));
ret = get_any_page(p, flags);
zone_pcp_enable(page_zone(p));
return ret;
}
/*
* Do all that is necessary to remove user space mappings. Unmap
* the pages and send SIGBUS to the processes if the data was dirty.
*/
static bool hwpoison_user_mappings(struct page *p, unsigned long pfn,
int flags, struct page *hpage)
{
enum ttu_flags ttu = TTU_IGNORE_MLOCK | TTU_SYNC;
struct address_space *mapping;
LIST_HEAD(tokill);
bool unmap_success;
int kill = 1, forcekill;
bool mlocked = PageMlocked(hpage);
/*
* Here we are interested only in user-mapped pages, so skip any
* other types of pages.
*/
if (PageReserved(p) || PageSlab(p))
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(hpage))
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)) {
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 higher level.
*/
mapping = hugetlb_page_mapping_lock_write(hpage);
if (mapping) {
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);
} else {
try_to_unmap(hpage, ttu);
}
}
unmap_success = !page_mapped(hpage);
if (!unmap_success)
pr_err("Memory failure: %#lx: failed to unmap page (mapcount=%d)\n",
pfn, page_mapcount(hpage));
/*
* try_to_unmap() might put mlocked page in lru cache, so call
* shake_page() again to ensure that it's flushed.
*/
if (mlocked)
shake_page(hpage);
/*
* Now that the dirty bit has been propagated to the
* struct page and all unmaps done we can decide if
* killing is needed or not. Only kill when the page
* was dirty or the process is not restartable,
* otherwise the tokill list is merely
* freed. When there was a problem unmapping earlier
* use a more force-full uncatchable kill to prevent
* any accesses to the poisoned memory.
*/
forcekill = PageDirty(hpage) || (flags & MF_MUST_KILL);
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);
res = -EHWPOISON;
if (flags & MF_ACTION_REQUIRED)
res = kill_accessing_process(current, page_to_pfn(head), flags);
return res;
}
num_poisoned_pages_inc();
if (!(flags & MF_COUNT_INCREASED)) {
res = get_hwpoison_page(p, flags);
if (!res) {
/*
* 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);
res = MF_FAILED;
if (__page_handle_poison(p)) {
page_ref_inc(p);
res = MF_RECOVERED;
}
action_result(pfn, MF_MSG_FREE_HUGE, res);
return res == MF_RECOVERED ? 0 : -EBUSY;
} else if (res < 0) {
action_result(pfn, MF_MSG_UNKNOWN, MF_IGNORED);
return -EBUSY;
}
}
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;
}
return 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);
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, false, 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 = 0;
unsigned long page_flags;
bool retry = true;
static DEFINE_MUTEX(mf_mutex);
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;
}
mutex_lock(&mf_mutex);
try_again:
if (PageHuge(p)) {
res = memory_failure_hugetlb(pfn, flags);
goto unlock_mutex;
}
if (TestSetPageHWPoison(p)) {
pr_err("Memory failure: %#lx: already hardware poisoned\n",
pfn);
res = -EHWPOISON;
if (flags & MF_ACTION_REQUIRED)
res = kill_accessing_process(current, pfn, flags);
goto unlock_mutex;
}
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)) {
res = get_hwpoison_page(p, flags);
if (!res) {
if (is_free_buddy_page(p)) {
if (take_page_off_buddy(p)) {
page_ref_inc(p);
res = MF_RECOVERED;
} else {
/* We lost the race, try again */
if (retry) {
ClearPageHWPoison(p);
num_poisoned_pages_dec();
retry = false;
goto try_again;
}
res = MF_FAILED;
}
action_result(pfn, MF_MSG_BUDDY, res);
res = res == MF_RECOVERED ? 0 : -EBUSY;
} else {
action_result(pfn, MF_MSG_KERNEL_HIGH_ORDER, MF_IGNORED);
res = -EBUSY;
}
goto unlock_mutex;
} else if (res < 0) {
action_result(pfn, MF_MSG_UNKNOWN, MF_IGNORED);
res = -EBUSY;
goto unlock_mutex;
}
}
if (PageTransHuge(hpage)) {
if (try_to_split_thp_page(p, "Memory Failure") < 0) {
action_result(pfn, MF_MSG_UNSPLIT_THP, MF_IGNORED);
res = -EBUSY;
goto unlock_mutex;
}
VM_BUG_ON_PAGE(!page_count(p), p);
}
/*
* We ignore non-LRU pages for good reasons.
* - PG_locked is only well defined for LRU pages and a few others
* - to avoid races with __SetPageLocked()
* - to avoid races with __SetPageSlab*() (and more non-atomic ops)
* The check (unnecessarily) ignores LRU pages being isolated and
* walked by the page reclaim code, however that's not a big loss.
*/
shake_page(p);
lock_page(p);
/*
* 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 unlock_page;
}
/*
* We use page flags to determine what action should be taken, but
* the flags can be modified by the error containment action. One
* example is an mlocked page, where PG_mlocked is cleared by
* page_remove_rmap() in try_to_unmap_one(). So to determine page status
* correctly, we save a copy of the page flags at this time.
*/
page_flags = p->flags;
/*
* 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);
goto unlock_mutex;
}
if (hwpoison_filter(p)) {
if (TestClearPageHWPoison(p))
num_poisoned_pages_dec();
unlock_page(p);
put_page(p);
goto unlock_mutex;
}
/*
* __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 unlock_page;
}
/*
* 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 unlock_page;
}
identify_page_state:
res = identify_page_state(pfn, p, page_flags);
mutex_unlock(&mf_mutex);
return res;
unlock_page:
unlock_page(p);
unlock_mutex:
mutex_unlock(&mf_mutex);
return res;
}
EXPORT_SYMBOL_GPL(memory_failure);
#define MEMORY_FAILURE_FIFO_ORDER 4
#define MEMORY_FAILURE_FIFO_SIZE (1 << MEMORY_FAILURE_FIFO_ORDER)
struct memory_failure_entry {
unsigned long pfn;
int flags;
};
struct memory_failure_cpu {
DECLARE_KFIFO(fifo, struct memory_failure_entry,
MEMORY_FAILURE_FIFO_SIZE);
spinlock_t lock;
struct work_struct work;
};
static DEFINE_PER_CPU(struct memory_failure_cpu, memory_failure_cpu);
/**
* memory_failure_queue - Schedule handling memory failure of a page.
* @pfn: Page Number of the corrupted page
* @flags: Flags for memory failure handling
*
* This function is called by the low level hardware error handler
* when it detects hardware memory corruption of a page. It schedules
* the recovering of error page, including dropping pages, killing
* processes etc.
*
* The function is primarily of use for corruptions that
* happen outside the current execution context (e.g. when
* detected by a background scrubber)
*
* Can run in IRQ context.
*/
void memory_failure_queue(unsigned long pfn, int flags)
{
struct memory_failure_cpu *mf_cpu;
unsigned long proc_flags;
struct memory_failure_entry entry = {
.pfn = pfn,
.flags = flags,
};
mf_cpu = &get_cpu_var(memory_failure_cpu);
spin_lock_irqsave(&mf_cpu->lock, proc_flags);
if (kfifo_put(&mf_cpu->fifo, entry))
schedule_work_on(smp_processor_id(), &mf_cpu->work);
else
pr_err("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;
unsigned long flags = 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, flags)) {
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);
static bool isolate_page(struct page *page, struct list_head *pagelist)
{
bool isolated = false;
bool lru = PageLRU(page);
if (PageHuge(page)) {
isolated = isolate_huge_page(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 int soft_offline_free_page(struct page *page)
{
int rc = 0;
if (!page_handle_poison(page, true, false))
rc = -EBUSY;
return rc;
}
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_hwpoison_page(page, flags);
put_online_mems();
if (ret > 0) {
ret = soft_offline_in_use_page(page);
} else if (ret == 0) {
if (soft_offline_free_page(page) && try_again) {
try_again = false;
goto retry;
}
} else if (ret == -EIO) {
pr_info("%s: %#lx: unknown page type: %lx (%pGp)\n",
__func__, pfn, page->flags, &page->flags);
}
return ret;
}