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khugepaged.c
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khugepaged.c
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// SPDX-License-Identifier: GPL-2.0
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/sched/mm.h>
#include <linux/sched/coredump.h>
#include <linux/mmu_notifier.h>
#include <linux/rmap.h>
#include <linux/swap.h>
#include <linux/mm_inline.h>
#include <linux/kthread.h>
#include <linux/khugepaged.h>
#include <linux/freezer.h>
#include <linux/mman.h>
#include <linux/hashtable.h>
#include <linux/userfaultfd_k.h>
#include <linux/page_idle.h>
#include <linux/swapops.h>
#include <linux/shmem_fs.h>
#include <asm/tlb.h>
#include <asm/pgalloc.h>
#include "internal.h"
enum scan_result {
SCAN_FAIL,
SCAN_SUCCEED,
SCAN_PMD_NULL,
SCAN_EXCEED_NONE_PTE,
SCAN_EXCEED_SWAP_PTE,
SCAN_EXCEED_SHARED_PTE,
SCAN_PTE_NON_PRESENT,
SCAN_PTE_UFFD_WP,
SCAN_PAGE_RO,
SCAN_LACK_REFERENCED_PAGE,
SCAN_PAGE_NULL,
SCAN_SCAN_ABORT,
SCAN_PAGE_COUNT,
SCAN_PAGE_LRU,
SCAN_PAGE_LOCK,
SCAN_PAGE_ANON,
SCAN_PAGE_COMPOUND,
SCAN_ANY_PROCESS,
SCAN_VMA_NULL,
SCAN_VMA_CHECK,
SCAN_ADDRESS_RANGE,
SCAN_SWAP_CACHE_PAGE,
SCAN_DEL_PAGE_LRU,
SCAN_ALLOC_HUGE_PAGE_FAIL,
SCAN_CGROUP_CHARGE_FAIL,
SCAN_TRUNCATED,
SCAN_PAGE_HAS_PRIVATE,
};
#define CREATE_TRACE_POINTS
#include <trace/events/huge_memory.h>
static struct task_struct *khugepaged_thread __read_mostly;
static DEFINE_MUTEX(khugepaged_mutex);
/* default scan 8*512 pte (or vmas) every 30 second */
static unsigned int khugepaged_pages_to_scan __read_mostly;
static unsigned int khugepaged_pages_collapsed;
static unsigned int khugepaged_full_scans;
static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
/* during fragmentation poll the hugepage allocator once every minute */
static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
static unsigned long khugepaged_sleep_expire;
static DEFINE_SPINLOCK(khugepaged_mm_lock);
static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
/*
* default collapse hugepages if there is at least one pte mapped like
* it would have happened if the vma was large enough during page
* fault.
*/
static unsigned int khugepaged_max_ptes_none __read_mostly;
static unsigned int khugepaged_max_ptes_swap __read_mostly;
static unsigned int khugepaged_max_ptes_shared __read_mostly;
#define MM_SLOTS_HASH_BITS 10
static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
static struct kmem_cache *mm_slot_cache __read_mostly;
#define MAX_PTE_MAPPED_THP 8
/**
* struct mm_slot - hash lookup from mm to mm_slot
* @hash: hash collision list
* @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
* @mm: the mm that this information is valid for
* @nr_pte_mapped_thp: number of pte mapped THP
* @pte_mapped_thp: address array corresponding pte mapped THP
*/
struct mm_slot {
struct hlist_node hash;
struct list_head mm_node;
struct mm_struct *mm;
/* pte-mapped THP in this mm */
int nr_pte_mapped_thp;
unsigned long pte_mapped_thp[MAX_PTE_MAPPED_THP];
};
/**
* struct khugepaged_scan - cursor for scanning
* @mm_head: the head of the mm list to scan
* @mm_slot: the current mm_slot we are scanning
* @address: the next address inside that to be scanned
*
* There is only the one khugepaged_scan instance of this cursor structure.
*/
struct khugepaged_scan {
struct list_head mm_head;
struct mm_slot *mm_slot;
unsigned long address;
};
static struct khugepaged_scan khugepaged_scan = {
.mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
};
#ifdef CONFIG_SYSFS
static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
return sysfs_emit(buf, "%u\n", khugepaged_scan_sleep_millisecs);
}
static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
unsigned int msecs;
int err;
err = kstrtouint(buf, 10, &msecs);
if (err)
return -EINVAL;
khugepaged_scan_sleep_millisecs = msecs;
khugepaged_sleep_expire = 0;
wake_up_interruptible(&khugepaged_wait);
return count;
}
static struct kobj_attribute scan_sleep_millisecs_attr =
__ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
scan_sleep_millisecs_store);
static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
return sysfs_emit(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
}
static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
unsigned int msecs;
int err;
err = kstrtouint(buf, 10, &msecs);
if (err)
return -EINVAL;
khugepaged_alloc_sleep_millisecs = msecs;
khugepaged_sleep_expire = 0;
wake_up_interruptible(&khugepaged_wait);
return count;
}
static struct kobj_attribute alloc_sleep_millisecs_attr =
__ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
alloc_sleep_millisecs_store);
static ssize_t pages_to_scan_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
return sysfs_emit(buf, "%u\n", khugepaged_pages_to_scan);
}
static ssize_t pages_to_scan_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
unsigned int pages;
int err;
err = kstrtouint(buf, 10, &pages);
if (err || !pages)
return -EINVAL;
khugepaged_pages_to_scan = pages;
return count;
}
static struct kobj_attribute pages_to_scan_attr =
__ATTR(pages_to_scan, 0644, pages_to_scan_show,
pages_to_scan_store);
static ssize_t pages_collapsed_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
return sysfs_emit(buf, "%u\n", khugepaged_pages_collapsed);
}
static struct kobj_attribute pages_collapsed_attr =
__ATTR_RO(pages_collapsed);
static ssize_t full_scans_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
return sysfs_emit(buf, "%u\n", khugepaged_full_scans);
}
static struct kobj_attribute full_scans_attr =
__ATTR_RO(full_scans);
static ssize_t khugepaged_defrag_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return single_hugepage_flag_show(kobj, attr, buf,
TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
}
static ssize_t khugepaged_defrag_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
return single_hugepage_flag_store(kobj, attr, buf, count,
TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
}
static struct kobj_attribute khugepaged_defrag_attr =
__ATTR(defrag, 0644, khugepaged_defrag_show,
khugepaged_defrag_store);
/*
* max_ptes_none controls if khugepaged should collapse hugepages over
* any unmapped ptes in turn potentially increasing the memory
* footprint of the vmas. When max_ptes_none is 0 khugepaged will not
* reduce the available free memory in the system as it
* runs. Increasing max_ptes_none will instead potentially reduce the
* free memory in the system during the khugepaged scan.
*/
static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
return sysfs_emit(buf, "%u\n", khugepaged_max_ptes_none);
}
static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
int err;
unsigned long max_ptes_none;
err = kstrtoul(buf, 10, &max_ptes_none);
if (err || max_ptes_none > HPAGE_PMD_NR-1)
return -EINVAL;
khugepaged_max_ptes_none = max_ptes_none;
return count;
}
static struct kobj_attribute khugepaged_max_ptes_none_attr =
__ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
khugepaged_max_ptes_none_store);
static ssize_t khugepaged_max_ptes_swap_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
return sysfs_emit(buf, "%u\n", khugepaged_max_ptes_swap);
}
static ssize_t khugepaged_max_ptes_swap_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
int err;
unsigned long max_ptes_swap;
err = kstrtoul(buf, 10, &max_ptes_swap);
if (err || max_ptes_swap > HPAGE_PMD_NR-1)
return -EINVAL;
khugepaged_max_ptes_swap = max_ptes_swap;
return count;
}
static struct kobj_attribute khugepaged_max_ptes_swap_attr =
__ATTR(max_ptes_swap, 0644, khugepaged_max_ptes_swap_show,
khugepaged_max_ptes_swap_store);
static ssize_t khugepaged_max_ptes_shared_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
return sysfs_emit(buf, "%u\n", khugepaged_max_ptes_shared);
}
static ssize_t khugepaged_max_ptes_shared_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
int err;
unsigned long max_ptes_shared;
err = kstrtoul(buf, 10, &max_ptes_shared);
if (err || max_ptes_shared > HPAGE_PMD_NR-1)
return -EINVAL;
khugepaged_max_ptes_shared = max_ptes_shared;
return count;
}
static struct kobj_attribute khugepaged_max_ptes_shared_attr =
__ATTR(max_ptes_shared, 0644, khugepaged_max_ptes_shared_show,
khugepaged_max_ptes_shared_store);
static struct attribute *khugepaged_attr[] = {
&khugepaged_defrag_attr.attr,
&khugepaged_max_ptes_none_attr.attr,
&khugepaged_max_ptes_swap_attr.attr,
&khugepaged_max_ptes_shared_attr.attr,
&pages_to_scan_attr.attr,
&pages_collapsed_attr.attr,
&full_scans_attr.attr,
&scan_sleep_millisecs_attr.attr,
&alloc_sleep_millisecs_attr.attr,
NULL,
};
struct attribute_group khugepaged_attr_group = {
.attrs = khugepaged_attr,
.name = "khugepaged",
};
#endif /* CONFIG_SYSFS */
int hugepage_madvise(struct vm_area_struct *vma,
unsigned long *vm_flags, int advice)
{
switch (advice) {
case MADV_HUGEPAGE:
#ifdef CONFIG_S390
/*
* qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
* can't handle this properly after s390_enable_sie, so we simply
* ignore the madvise to prevent qemu from causing a SIGSEGV.
*/
if (mm_has_pgste(vma->vm_mm))
return 0;
#endif
*vm_flags &= ~VM_NOHUGEPAGE;
*vm_flags |= VM_HUGEPAGE;
/*
* If the vma become good for khugepaged to scan,
* register it here without waiting a page fault that
* may not happen any time soon.
*/
if (!(*vm_flags & VM_NO_KHUGEPAGED) &&
khugepaged_enter_vma_merge(vma, *vm_flags))
return -ENOMEM;
break;
case MADV_NOHUGEPAGE:
*vm_flags &= ~VM_HUGEPAGE;
*vm_flags |= VM_NOHUGEPAGE;
/*
* Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
* this vma even if we leave the mm registered in khugepaged if
* it got registered before VM_NOHUGEPAGE was set.
*/
break;
}
return 0;
}
int __init khugepaged_init(void)
{
mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
sizeof(struct mm_slot),
__alignof__(struct mm_slot), 0, NULL);
if (!mm_slot_cache)
return -ENOMEM;
khugepaged_pages_to_scan = HPAGE_PMD_NR * 8;
khugepaged_max_ptes_none = HPAGE_PMD_NR - 1;
khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8;
khugepaged_max_ptes_shared = HPAGE_PMD_NR / 2;
return 0;
}
void __init khugepaged_destroy(void)
{
kmem_cache_destroy(mm_slot_cache);
}
static inline struct mm_slot *alloc_mm_slot(void)
{
if (!mm_slot_cache) /* initialization failed */
return NULL;
return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
}
static inline void free_mm_slot(struct mm_slot *mm_slot)
{
kmem_cache_free(mm_slot_cache, mm_slot);
}
static struct mm_slot *get_mm_slot(struct mm_struct *mm)
{
struct mm_slot *mm_slot;
hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
if (mm == mm_slot->mm)
return mm_slot;
return NULL;
}
static void insert_to_mm_slots_hash(struct mm_struct *mm,
struct mm_slot *mm_slot)
{
mm_slot->mm = mm;
hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
}
static inline int khugepaged_test_exit(struct mm_struct *mm)
{
return atomic_read(&mm->mm_users) == 0;
}
static bool hugepage_vma_check(struct vm_area_struct *vma,
unsigned long vm_flags)
{
if (!transhuge_vma_enabled(vma, vm_flags))
return false;
if (vma->vm_file && !IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) -
vma->vm_pgoff, HPAGE_PMD_NR))
return false;
/* Enabled via shmem mount options or sysfs settings. */
if (shmem_file(vma->vm_file))
return shmem_huge_enabled(vma);
/* THP settings require madvise. */
if (!(vm_flags & VM_HUGEPAGE) && !khugepaged_always())
return false;
/* Only regular file is valid */
if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && vma->vm_file &&
(vm_flags & VM_EXEC)) {
struct inode *inode = vma->vm_file->f_inode;
return !inode_is_open_for_write(inode) &&
S_ISREG(inode->i_mode);
}
if (!vma->anon_vma || vma->vm_ops)
return false;
if (vma_is_temporary_stack(vma))
return false;
return !(vm_flags & VM_NO_KHUGEPAGED);
}
int __khugepaged_enter(struct mm_struct *mm)
{
struct mm_slot *mm_slot;
int wakeup;
mm_slot = alloc_mm_slot();
if (!mm_slot)
return -ENOMEM;
/* __khugepaged_exit() must not run from under us */
VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
free_mm_slot(mm_slot);
return 0;
}
spin_lock(&khugepaged_mm_lock);
insert_to_mm_slots_hash(mm, mm_slot);
/*
* Insert just behind the scanning cursor, to let the area settle
* down a little.
*/
wakeup = list_empty(&khugepaged_scan.mm_head);
list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
spin_unlock(&khugepaged_mm_lock);
mmgrab(mm);
if (wakeup)
wake_up_interruptible(&khugepaged_wait);
return 0;
}
int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
unsigned long vm_flags)
{
unsigned long hstart, hend;
/*
* khugepaged only supports read-only files for non-shmem files.
* khugepaged does not yet work on special mappings. And
* file-private shmem THP is not supported.
*/
if (!hugepage_vma_check(vma, vm_flags))
return 0;
hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
hend = vma->vm_end & HPAGE_PMD_MASK;
if (hstart < hend)
return khugepaged_enter(vma, vm_flags);
return 0;
}
void __khugepaged_exit(struct mm_struct *mm)
{
struct mm_slot *mm_slot;
int free = 0;
spin_lock(&khugepaged_mm_lock);
mm_slot = get_mm_slot(mm);
if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
hash_del(&mm_slot->hash);
list_del(&mm_slot->mm_node);
free = 1;
}
spin_unlock(&khugepaged_mm_lock);
if (free) {
clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
free_mm_slot(mm_slot);
mmdrop(mm);
} else if (mm_slot) {
/*
* This is required to serialize against
* khugepaged_test_exit() (which is guaranteed to run
* under mmap sem read mode). Stop here (after we
* return all pagetables will be destroyed) until
* khugepaged has finished working on the pagetables
* under the mmap_lock.
*/
mmap_write_lock(mm);
mmap_write_unlock(mm);
}
}
static void release_pte_page(struct page *page)
{
mod_node_page_state(page_pgdat(page),
NR_ISOLATED_ANON + page_is_file_lru(page),
-compound_nr(page));
unlock_page(page);
putback_lru_page(page);
}
static void release_pte_pages(pte_t *pte, pte_t *_pte,
struct list_head *compound_pagelist)
{
struct page *page, *tmp;
while (--_pte >= pte) {
pte_t pteval = *_pte;
page = pte_page(pteval);
if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)) &&
!PageCompound(page))
release_pte_page(page);
}
list_for_each_entry_safe(page, tmp, compound_pagelist, lru) {
list_del(&page->lru);
release_pte_page(page);
}
}
static bool is_refcount_suitable(struct page *page)
{
int expected_refcount;
expected_refcount = total_mapcount(page);
if (PageSwapCache(page))
expected_refcount += compound_nr(page);
return page_count(page) == expected_refcount;
}
static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
unsigned long address,
pte_t *pte,
struct list_head *compound_pagelist)
{
struct page *page = NULL;
pte_t *_pte;
int none_or_zero = 0, shared = 0, result = 0, referenced = 0;
bool writable = false;
for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
_pte++, address += PAGE_SIZE) {
pte_t pteval = *_pte;
if (pte_none(pteval) || (pte_present(pteval) &&
is_zero_pfn(pte_pfn(pteval)))) {
if (!userfaultfd_armed(vma) &&
++none_or_zero <= khugepaged_max_ptes_none) {
continue;
} else {
result = SCAN_EXCEED_NONE_PTE;
goto out;
}
}
if (!pte_present(pteval)) {
result = SCAN_PTE_NON_PRESENT;
goto out;
}
page = vm_normal_page(vma, address, pteval);
if (unlikely(!page)) {
result = SCAN_PAGE_NULL;
goto out;
}
VM_BUG_ON_PAGE(!PageAnon(page), page);
if (page_mapcount(page) > 1 &&
++shared > khugepaged_max_ptes_shared) {
result = SCAN_EXCEED_SHARED_PTE;
goto out;
}
if (PageCompound(page)) {
struct page *p;
page = compound_head(page);
/*
* Check if we have dealt with the compound page
* already
*/
list_for_each_entry(p, compound_pagelist, lru) {
if (page == p)
goto next;
}
}
/*
* We can do it before isolate_lru_page because the
* page can't be freed from under us. NOTE: PG_lock
* is needed to serialize against split_huge_page
* when invoked from the VM.
*/
if (!trylock_page(page)) {
result = SCAN_PAGE_LOCK;
goto out;
}
/*
* Check if the page has any GUP (or other external) pins.
*
* The page table that maps the page has been already unlinked
* from the page table tree and this process cannot get
* an additional pin on the page.
*
* New pins can come later if the page is shared across fork,
* but not from this process. The other process cannot write to
* the page, only trigger CoW.
*/
if (!is_refcount_suitable(page)) {
unlock_page(page);
result = SCAN_PAGE_COUNT;
goto out;
}
if (!pte_write(pteval) && PageSwapCache(page) &&
!reuse_swap_page(page, NULL)) {
/*
* Page is in the swap cache and cannot be re-used.
* It cannot be collapsed into a THP.
*/
unlock_page(page);
result = SCAN_SWAP_CACHE_PAGE;
goto out;
}
/*
* Isolate the page to avoid collapsing an hugepage
* currently in use by the VM.
*/
if (isolate_lru_page(page)) {
unlock_page(page);
result = SCAN_DEL_PAGE_LRU;
goto out;
}
mod_node_page_state(page_pgdat(page),
NR_ISOLATED_ANON + page_is_file_lru(page),
compound_nr(page));
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(PageLRU(page), page);
if (PageCompound(page))
list_add_tail(&page->lru, compound_pagelist);
next:
/* There should be enough young pte to collapse the page */
if (pte_young(pteval) ||
page_is_young(page) || PageReferenced(page) ||
mmu_notifier_test_young(vma->vm_mm, address))
referenced++;
if (pte_write(pteval))
writable = true;
}
if (unlikely(!writable)) {
result = SCAN_PAGE_RO;
} else if (unlikely(!referenced)) {
result = SCAN_LACK_REFERENCED_PAGE;
} else {
result = SCAN_SUCCEED;
trace_mm_collapse_huge_page_isolate(page, none_or_zero,
referenced, writable, result);
return 1;
}
out:
release_pte_pages(pte, _pte, compound_pagelist);
trace_mm_collapse_huge_page_isolate(page, none_or_zero,
referenced, writable, result);
return 0;
}
static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
struct vm_area_struct *vma,
unsigned long address,
spinlock_t *ptl,
struct list_head *compound_pagelist)
{
struct page *src_page, *tmp;
pte_t *_pte;
for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
_pte++, page++, address += PAGE_SIZE) {
pte_t pteval = *_pte;
if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
clear_user_highpage(page, address);
add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
if (is_zero_pfn(pte_pfn(pteval))) {
/*
* ptl mostly unnecessary.
*/
spin_lock(ptl);
/*
* paravirt calls inside pte_clear here are
* superfluous.
*/
pte_clear(vma->vm_mm, address, _pte);
spin_unlock(ptl);
}
} else {
src_page = pte_page(pteval);
copy_user_highpage(page, src_page, address, vma);
if (!PageCompound(src_page))
release_pte_page(src_page);
/*
* ptl mostly unnecessary, but preempt has to
* be disabled to update the per-cpu stats
* inside page_remove_rmap().
*/
spin_lock(ptl);
/*
* paravirt calls inside pte_clear here are
* superfluous.
*/
pte_clear(vma->vm_mm, address, _pte);
page_remove_rmap(src_page, false);
spin_unlock(ptl);
free_page_and_swap_cache(src_page);
}
}
list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) {
list_del(&src_page->lru);
release_pte_page(src_page);
}
}
static void khugepaged_alloc_sleep(void)
{
DEFINE_WAIT(wait);
add_wait_queue(&khugepaged_wait, &wait);
freezable_schedule_timeout_interruptible(
msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
remove_wait_queue(&khugepaged_wait, &wait);
}
static int khugepaged_node_load[MAX_NUMNODES];
static bool khugepaged_scan_abort(int nid)
{
int i;
/*
* If node_reclaim_mode is disabled, then no extra effort is made to
* allocate memory locally.
*/
if (!node_reclaim_enabled())
return false;
/* If there is a count for this node already, it must be acceptable */
if (khugepaged_node_load[nid])
return false;
for (i = 0; i < MAX_NUMNODES; i++) {
if (!khugepaged_node_load[i])
continue;
if (node_distance(nid, i) > node_reclaim_distance)
return true;
}
return false;
}
/* Defrag for khugepaged will enter direct reclaim/compaction if necessary */
static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void)
{
return khugepaged_defrag() ? GFP_TRANSHUGE : GFP_TRANSHUGE_LIGHT;
}
#ifdef CONFIG_NUMA
static int khugepaged_find_target_node(void)
{
static int last_khugepaged_target_node = NUMA_NO_NODE;
int nid, target_node = 0, max_value = 0;
/* find first node with max normal pages hit */
for (nid = 0; nid < MAX_NUMNODES; nid++)
if (khugepaged_node_load[nid] > max_value) {
max_value = khugepaged_node_load[nid];
target_node = nid;
}
/* do some balance if several nodes have the same hit record */
if (target_node <= last_khugepaged_target_node)
for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
nid++)
if (max_value == khugepaged_node_load[nid]) {
target_node = nid;
break;
}
last_khugepaged_target_node = target_node;
return target_node;
}
static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
{
if (IS_ERR(*hpage)) {
if (!*wait)
return false;
*wait = false;
*hpage = NULL;
khugepaged_alloc_sleep();
} else if (*hpage) {
put_page(*hpage);
*hpage = NULL;
}
return true;
}
static struct page *
khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
{
VM_BUG_ON_PAGE(*hpage, *hpage);
*hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
if (unlikely(!*hpage)) {
count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
*hpage = ERR_PTR(-ENOMEM);
return NULL;
}
prep_transhuge_page(*hpage);
count_vm_event(THP_COLLAPSE_ALLOC);
return *hpage;
}
#else
static int khugepaged_find_target_node(void)
{
return 0;
}
static inline struct page *alloc_khugepaged_hugepage(void)
{
struct page *page;
page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(),
HPAGE_PMD_ORDER);
if (page)
prep_transhuge_page(page);
return page;
}
static struct page *khugepaged_alloc_hugepage(bool *wait)
{
struct page *hpage;
do {
hpage = alloc_khugepaged_hugepage();
if (!hpage) {
count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
if (!*wait)
return NULL;
*wait = false;
khugepaged_alloc_sleep();
} else
count_vm_event(THP_COLLAPSE_ALLOC);
} while (unlikely(!hpage) && likely(khugepaged_enabled()));
return hpage;
}
static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
{
/*
* If the hpage allocated earlier was briefly exposed in page cache
* before collapse_file() failed, it is possible that racing lookups
* have not yet completed, and would then be unpleasantly surprised by
* finding the hpage reused for the same mapping at a different offset.
* Just release the previous allocation if there is any danger of that.
*/
if (*hpage && page_count(*hpage) > 1) {
put_page(*hpage);
*hpage = NULL;
}
if (!*hpage)
*hpage = khugepaged_alloc_hugepage(wait);
if (unlikely(!*hpage))
return false;
return true;
}
static struct page *
khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
{
VM_BUG_ON(!*hpage);
return *hpage;
}
#endif
/*
* If mmap_lock temporarily dropped, revalidate vma
* before taking mmap_lock.
* Return 0 if succeeds, otherwise return none-zero
* value (scan code).
*/
static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
struct vm_area_struct **vmap)
{
struct vm_area_struct *vma;
unsigned long hstart, hend;
if (unlikely(khugepaged_test_exit(mm)))
return SCAN_ANY_PROCESS;
*vmap = vma = find_vma(mm, address);
if (!vma)
return SCAN_VMA_NULL;
hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
hend = vma->vm_end & HPAGE_PMD_MASK;
if (address < hstart || address + HPAGE_PMD_SIZE > hend)
return SCAN_ADDRESS_RANGE;
if (!hugepage_vma_check(vma, vma->vm_flags))
return SCAN_VMA_CHECK;
/* Anon VMA expected */
if (!vma->anon_vma || vma->vm_ops)
return SCAN_VMA_CHECK;
return 0;
}
/*
* Bring missing pages in from swap, to complete THP collapse.
* Only done if khugepaged_scan_pmd believes it is worthwhile.
*
* Called and returns without pte mapped or spinlocks held,