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linux/mm/huge_memory.c
Leo Stone d3ac65d274 mm: huge_memory: handle strsep not finding delimiter 
split_huge_pages_write() does not handle the case where strsep finds no
delimiter in the given string and sets the input buffer to NULL, which
allows this reproducer to trigger a protection fault.

Link: https://lkml.kernel.org/r/20241216042752.257090-2-leocstone@gmail.com
Signed-off-by: Leo Stone <leocstone@gmail.com>
Reported-by: syzbot+8a3da2f1bbf59227c289@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=8a3da2f1bbf59227c289
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-12-18 19:04:47 -08:00

4321 lines
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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2009 Red Hat, Inc.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/sched/mm.h>
#include <linux/sched/numa_balancing.h>
#include <linux/highmem.h>
#include <linux/hugetlb.h>
#include <linux/mmu_notifier.h>
#include <linux/rmap.h>
#include <linux/swap.h>
#include <linux/shrinker.h>
#include <linux/mm_inline.h>
#include <linux/swapops.h>
#include <linux/backing-dev.h>
#include <linux/dax.h>
#include <linux/mm_types.h>
#include <linux/khugepaged.h>
#include <linux/freezer.h>
#include <linux/pfn_t.h>
#include <linux/mman.h>
#include <linux/memremap.h>
#include <linux/pagemap.h>
#include <linux/debugfs.h>
#include <linux/migrate.h>
#include <linux/hashtable.h>
#include <linux/userfaultfd_k.h>
#include <linux/page_idle.h>
#include <linux/shmem_fs.h>
#include <linux/oom.h>
#include <linux/numa.h>
#include <linux/page_owner.h>
#include <linux/sched/sysctl.h>
#include <linux/memory-tiers.h>
#include <linux/compat.h>
#include <linux/pgalloc_tag.h>
#include <linux/pagewalk.h>
#include <asm/tlb.h>
#include <asm/pgalloc.h>
#include "internal.h"
#include "swap.h"
#define CREATE_TRACE_POINTS
#include <trace/events/thp.h>
/*
* By default, transparent hugepage support is disabled in order to avoid
* risking an increased memory footprint for applications that are not
* guaranteed to benefit from it. When transparent hugepage support is
* enabled, it is for all mappings, and khugepaged scans all mappings.
* Defrag is invoked by khugepaged hugepage allocations and by page faults
* for all hugepage allocations.
*/
unsigned long transparent_hugepage_flags __read_mostly =
#ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
(1<<TRANSPARENT_HUGEPAGE_FLAG)|
#endif
#ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
(1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
#endif
(1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
(1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
(1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
static struct shrinker *deferred_split_shrinker;
static unsigned long deferred_split_count(struct shrinker *shrink,
struct shrink_control *sc);
static unsigned long deferred_split_scan(struct shrinker *shrink,
struct shrink_control *sc);
static bool split_underused_thp = true;
static atomic_t huge_zero_refcount;
struct folio *huge_zero_folio __read_mostly;
unsigned long huge_zero_pfn __read_mostly = ~0UL;
unsigned long huge_anon_orders_always __read_mostly;
unsigned long huge_anon_orders_madvise __read_mostly;
unsigned long huge_anon_orders_inherit __read_mostly;
static bool anon_orders_configured __initdata;
static inline bool file_thp_enabled(struct vm_area_struct *vma)
{
struct inode *inode;
if (!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS))
return false;
if (!vma->vm_file)
return false;
inode = file_inode(vma->vm_file);
return !inode_is_open_for_write(inode) && S_ISREG(inode->i_mode);
}
unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma,
unsigned long vm_flags,
unsigned long tva_flags,
unsigned long orders)
{
bool smaps = tva_flags & TVA_SMAPS;
bool in_pf = tva_flags & TVA_IN_PF;
bool enforce_sysfs = tva_flags & TVA_ENFORCE_SYSFS;
unsigned long supported_orders;
/* Check the intersection of requested and supported orders. */
if (vma_is_anonymous(vma))
supported_orders = THP_ORDERS_ALL_ANON;
else if (vma_is_special_huge(vma))
supported_orders = THP_ORDERS_ALL_SPECIAL;
else
supported_orders = THP_ORDERS_ALL_FILE_DEFAULT;
orders &= supported_orders;
if (!orders)
return 0;
if (!vma->vm_mm) /* vdso */
return 0;
if (thp_disabled_by_hw() || vma_thp_disabled(vma, vm_flags))
return 0;
/* khugepaged doesn't collapse DAX vma, but page fault is fine. */
if (vma_is_dax(vma))
return in_pf ? orders : 0;
/*
* khugepaged special VMA and hugetlb VMA.
* Must be checked after dax since some dax mappings may have
* VM_MIXEDMAP set.
*/
if (!in_pf && !smaps && (vm_flags & VM_NO_KHUGEPAGED))
return 0;
/*
* Check alignment for file vma and size for both file and anon vma by
* filtering out the unsuitable orders.
*
* Skip the check for page fault. Huge fault does the check in fault
* handlers.
*/
if (!in_pf) {
int order = highest_order(orders);
unsigned long addr;
while (orders) {
addr = vma->vm_end - (PAGE_SIZE << order);
if (thp_vma_suitable_order(vma, addr, order))
break;
order = next_order(&orders, order);
}
if (!orders)
return 0;
}
/*
* Enabled via shmem mount options or sysfs settings.
* Must be done before hugepage flags check since shmem has its
* own flags.
*/
if (!in_pf && shmem_file(vma->vm_file))
return shmem_allowable_huge_orders(file_inode(vma->vm_file),
vma, vma->vm_pgoff, 0,
!enforce_sysfs);
if (!vma_is_anonymous(vma)) {
/*
* Enforce sysfs THP requirements as necessary. Anonymous vmas
* were already handled in thp_vma_allowable_orders().
*/
if (enforce_sysfs &&
(!hugepage_global_enabled() || (!(vm_flags & VM_HUGEPAGE) &&
!hugepage_global_always())))
return 0;
/*
* Trust that ->huge_fault() handlers know what they are doing
* in fault path.
*/
if (((in_pf || smaps)) && vma->vm_ops->huge_fault)
return orders;
/* Only regular file is valid in collapse path */
if (((!in_pf || smaps)) && file_thp_enabled(vma))
return orders;
return 0;
}
if (vma_is_temporary_stack(vma))
return 0;
/*
* THPeligible bit of smaps should show 1 for proper VMAs even
* though anon_vma is not initialized yet.
*
* Allow page fault since anon_vma may be not initialized until
* the first page fault.
*/
if (!vma->anon_vma)
return (smaps || in_pf) ? orders : 0;
return orders;
}
static bool get_huge_zero_page(void)
{
struct folio *zero_folio;
retry:
if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
return true;
zero_folio = folio_alloc((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
HPAGE_PMD_ORDER);
if (!zero_folio) {
count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
return false;
}
/* Ensure zero folio won't have large_rmappable flag set. */
folio_clear_large_rmappable(zero_folio);
preempt_disable();
if (cmpxchg(&huge_zero_folio, NULL, zero_folio)) {
preempt_enable();
folio_put(zero_folio);
goto retry;
}
WRITE_ONCE(huge_zero_pfn, folio_pfn(zero_folio));
/* We take additional reference here. It will be put back by shrinker */
atomic_set(&huge_zero_refcount, 2);
preempt_enable();
count_vm_event(THP_ZERO_PAGE_ALLOC);
return true;
}
static void put_huge_zero_page(void)
{
/*
* Counter should never go to zero here. Only shrinker can put
* last reference.
*/
BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
}
struct folio *mm_get_huge_zero_folio(struct mm_struct *mm)
{
if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
return READ_ONCE(huge_zero_folio);
if (!get_huge_zero_page())
return NULL;
if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
put_huge_zero_page();
return READ_ONCE(huge_zero_folio);
}
void mm_put_huge_zero_folio(struct mm_struct *mm)
{
if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
put_huge_zero_page();
}
static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
struct shrink_control *sc)
{
/* we can free zero page only if last reference remains */
return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
}
static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
struct shrink_control *sc)
{
if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
struct folio *zero_folio = xchg(&huge_zero_folio, NULL);
BUG_ON(zero_folio == NULL);
WRITE_ONCE(huge_zero_pfn, ~0UL);
folio_put(zero_folio);
return HPAGE_PMD_NR;
}
return 0;
}
static struct shrinker *huge_zero_page_shrinker;
#ifdef CONFIG_SYSFS
static ssize_t enabled_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
const char *output;
if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
output = "[always] madvise never";
else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
&transparent_hugepage_flags))
output = "always [madvise] never";
else
output = "always madvise [never]";
return sysfs_emit(buf, "%s\n", output);
}
static ssize_t enabled_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
ssize_t ret = count;
if (sysfs_streq(buf, "always")) {
clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
} else if (sysfs_streq(buf, "madvise")) {
clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
} else if (sysfs_streq(buf, "never")) {
clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
} else
ret = -EINVAL;
if (ret > 0) {
int err = start_stop_khugepaged();
if (err)
ret = err;
}
return ret;
}
static struct kobj_attribute enabled_attr = __ATTR_RW(enabled);
ssize_t single_hugepage_flag_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf,
enum transparent_hugepage_flag flag)
{
return sysfs_emit(buf, "%d\n",
!!test_bit(flag, &transparent_hugepage_flags));
}
ssize_t single_hugepage_flag_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count,
enum transparent_hugepage_flag flag)
{
unsigned long value;
int ret;
ret = kstrtoul(buf, 10, &value);
if (ret < 0)
return ret;
if (value > 1)
return -EINVAL;
if (value)
set_bit(flag, &transparent_hugepage_flags);
else
clear_bit(flag, &transparent_hugepage_flags);
return count;
}
static ssize_t defrag_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
const char *output;
if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
&transparent_hugepage_flags))
output = "[always] defer defer+madvise madvise never";
else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG,
&transparent_hugepage_flags))
output = "always [defer] defer+madvise madvise never";
else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG,
&transparent_hugepage_flags))
output = "always defer [defer+madvise] madvise never";
else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG,
&transparent_hugepage_flags))
output = "always defer defer+madvise [madvise] never";
else
output = "always defer defer+madvise madvise [never]";
return sysfs_emit(buf, "%s\n", output);
}
static ssize_t defrag_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
if (sysfs_streq(buf, "always")) {
clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
} else if (sysfs_streq(buf, "defer+madvise")) {
clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
} else if (sysfs_streq(buf, "defer")) {
clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
} else if (sysfs_streq(buf, "madvise")) {
clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
} else if (sysfs_streq(buf, "never")) {
clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
} else
return -EINVAL;
return count;
}
static struct kobj_attribute defrag_attr = __ATTR_RW(defrag);
static ssize_t use_zero_page_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return single_hugepage_flag_show(kobj, attr, buf,
TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
}
static ssize_t use_zero_page_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_USE_ZERO_PAGE_FLAG);
}
static struct kobj_attribute use_zero_page_attr = __ATTR_RW(use_zero_page);
static ssize_t hpage_pmd_size_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return sysfs_emit(buf, "%lu\n", HPAGE_PMD_SIZE);
}
static struct kobj_attribute hpage_pmd_size_attr =
__ATTR_RO(hpage_pmd_size);
static ssize_t split_underused_thp_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return sysfs_emit(buf, "%d\n", split_underused_thp);
}
static ssize_t split_underused_thp_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
int err = kstrtobool(buf, &split_underused_thp);
if (err < 0)
return err;
return count;
}
static struct kobj_attribute split_underused_thp_attr = __ATTR(
shrink_underused, 0644, split_underused_thp_show, split_underused_thp_store);
static struct attribute *hugepage_attr[] = {
&enabled_attr.attr,
&defrag_attr.attr,
&use_zero_page_attr.attr,
&hpage_pmd_size_attr.attr,
#ifdef CONFIG_SHMEM
&shmem_enabled_attr.attr,
#endif
&split_underused_thp_attr.attr,
NULL,
};
static const struct attribute_group hugepage_attr_group = {
.attrs = hugepage_attr,
};
static void hugepage_exit_sysfs(struct kobject *hugepage_kobj);
static void thpsize_release(struct kobject *kobj);
static DEFINE_SPINLOCK(huge_anon_orders_lock);
static LIST_HEAD(thpsize_list);
static ssize_t anon_enabled_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
int order = to_thpsize(kobj)->order;
const char *output;
if (test_bit(order, &huge_anon_orders_always))
output = "[always] inherit madvise never";
else if (test_bit(order, &huge_anon_orders_inherit))
output = "always [inherit] madvise never";
else if (test_bit(order, &huge_anon_orders_madvise))
output = "always inherit [madvise] never";
else
output = "always inherit madvise [never]";
return sysfs_emit(buf, "%s\n", output);
}
static ssize_t anon_enabled_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
int order = to_thpsize(kobj)->order;
ssize_t ret = count;
if (sysfs_streq(buf, "always")) {
spin_lock(&huge_anon_orders_lock);
clear_bit(order, &huge_anon_orders_inherit);
clear_bit(order, &huge_anon_orders_madvise);
set_bit(order, &huge_anon_orders_always);
spin_unlock(&huge_anon_orders_lock);
} else if (sysfs_streq(buf, "inherit")) {
spin_lock(&huge_anon_orders_lock);
clear_bit(order, &huge_anon_orders_always);
clear_bit(order, &huge_anon_orders_madvise);
set_bit(order, &huge_anon_orders_inherit);
spin_unlock(&huge_anon_orders_lock);
} else if (sysfs_streq(buf, "madvise")) {
spin_lock(&huge_anon_orders_lock);
clear_bit(order, &huge_anon_orders_always);
clear_bit(order, &huge_anon_orders_inherit);
set_bit(order, &huge_anon_orders_madvise);
spin_unlock(&huge_anon_orders_lock);
} else if (sysfs_streq(buf, "never")) {
spin_lock(&huge_anon_orders_lock);
clear_bit(order, &huge_anon_orders_always);
clear_bit(order, &huge_anon_orders_inherit);
clear_bit(order, &huge_anon_orders_madvise);
spin_unlock(&huge_anon_orders_lock);
} else
ret = -EINVAL;
if (ret > 0) {
int err;
err = start_stop_khugepaged();
if (err)
ret = err;
}
return ret;
}
static struct kobj_attribute anon_enabled_attr =
__ATTR(enabled, 0644, anon_enabled_show, anon_enabled_store);
static struct attribute *anon_ctrl_attrs[] = {
&anon_enabled_attr.attr,
NULL,
};
static const struct attribute_group anon_ctrl_attr_grp = {
.attrs = anon_ctrl_attrs,
};
static struct attribute *file_ctrl_attrs[] = {
#ifdef CONFIG_SHMEM
&thpsize_shmem_enabled_attr.attr,
#endif
NULL,
};
static const struct attribute_group file_ctrl_attr_grp = {
.attrs = file_ctrl_attrs,
};
static struct attribute *any_ctrl_attrs[] = {
NULL,
};
static const struct attribute_group any_ctrl_attr_grp = {
.attrs = any_ctrl_attrs,
};
static const struct kobj_type thpsize_ktype = {
.release = &thpsize_release,
.sysfs_ops = &kobj_sysfs_ops,
};
DEFINE_PER_CPU(struct mthp_stat, mthp_stats) = {{{0}}};
static unsigned long sum_mthp_stat(int order, enum mthp_stat_item item)
{
unsigned long sum = 0;
int cpu;
for_each_possible_cpu(cpu) {
struct mthp_stat *this = &per_cpu(mthp_stats, cpu);
sum += this->stats[order][item];
}
return sum;
}
#define DEFINE_MTHP_STAT_ATTR(_name, _index) \
static ssize_t _name##_show(struct kobject *kobj, \
struct kobj_attribute *attr, char *buf) \
{ \
int order = to_thpsize(kobj)->order; \
\
return sysfs_emit(buf, "%lu\n", sum_mthp_stat(order, _index)); \
} \
static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
DEFINE_MTHP_STAT_ATTR(anon_fault_alloc, MTHP_STAT_ANON_FAULT_ALLOC);
DEFINE_MTHP_STAT_ATTR(anon_fault_fallback, MTHP_STAT_ANON_FAULT_FALLBACK);
DEFINE_MTHP_STAT_ATTR(anon_fault_fallback_charge, MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE);
DEFINE_MTHP_STAT_ATTR(zswpout, MTHP_STAT_ZSWPOUT);
DEFINE_MTHP_STAT_ATTR(swpin, MTHP_STAT_SWPIN);
DEFINE_MTHP_STAT_ATTR(swpout, MTHP_STAT_SWPOUT);
DEFINE_MTHP_STAT_ATTR(swpout_fallback, MTHP_STAT_SWPOUT_FALLBACK);
#ifdef CONFIG_SHMEM
DEFINE_MTHP_STAT_ATTR(shmem_alloc, MTHP_STAT_SHMEM_ALLOC);
DEFINE_MTHP_STAT_ATTR(shmem_fallback, MTHP_STAT_SHMEM_FALLBACK);
DEFINE_MTHP_STAT_ATTR(shmem_fallback_charge, MTHP_STAT_SHMEM_FALLBACK_CHARGE);
#endif
DEFINE_MTHP_STAT_ATTR(split, MTHP_STAT_SPLIT);
DEFINE_MTHP_STAT_ATTR(split_failed, MTHP_STAT_SPLIT_FAILED);
DEFINE_MTHP_STAT_ATTR(split_deferred, MTHP_STAT_SPLIT_DEFERRED);
DEFINE_MTHP_STAT_ATTR(nr_anon, MTHP_STAT_NR_ANON);
DEFINE_MTHP_STAT_ATTR(nr_anon_partially_mapped, MTHP_STAT_NR_ANON_PARTIALLY_MAPPED);
static struct attribute *anon_stats_attrs[] = {
&anon_fault_alloc_attr.attr,
&anon_fault_fallback_attr.attr,
&anon_fault_fallback_charge_attr.attr,
#ifndef CONFIG_SHMEM
&zswpout_attr.attr,
&swpin_attr.attr,
&swpout_attr.attr,
&swpout_fallback_attr.attr,
#endif
&split_deferred_attr.attr,
&nr_anon_attr.attr,
&nr_anon_partially_mapped_attr.attr,
NULL,
};
static struct attribute_group anon_stats_attr_grp = {
.name = "stats",
.attrs = anon_stats_attrs,
};
static struct attribute *file_stats_attrs[] = {
#ifdef CONFIG_SHMEM
&shmem_alloc_attr.attr,
&shmem_fallback_attr.attr,
&shmem_fallback_charge_attr.attr,
#endif
NULL,
};
static struct attribute_group file_stats_attr_grp = {
.name = "stats",
.attrs = file_stats_attrs,
};
static struct attribute *any_stats_attrs[] = {
#ifdef CONFIG_SHMEM
&zswpout_attr.attr,
&swpin_attr.attr,
&swpout_attr.attr,
&swpout_fallback_attr.attr,
#endif
&split_attr.attr,
&split_failed_attr.attr,
NULL,
};
static struct attribute_group any_stats_attr_grp = {
.name = "stats",
.attrs = any_stats_attrs,
};
static int sysfs_add_group(struct kobject *kobj,
const struct attribute_group *grp)
{
int ret = -ENOENT;
/*
* If the group is named, try to merge first, assuming the subdirectory
* was already created. This avoids the warning emitted by
* sysfs_create_group() if the directory already exists.
*/
if (grp->name)
ret = sysfs_merge_group(kobj, grp);
if (ret)
ret = sysfs_create_group(kobj, grp);
return ret;
}
static struct thpsize *thpsize_create(int order, struct kobject *parent)
{
unsigned long size = (PAGE_SIZE << order) / SZ_1K;
struct thpsize *thpsize;
int ret = -ENOMEM;
thpsize = kzalloc(sizeof(*thpsize), GFP_KERNEL);
if (!thpsize)
goto err;
thpsize->order = order;
ret = kobject_init_and_add(&thpsize->kobj, &thpsize_ktype, parent,
"hugepages-%lukB", size);
if (ret) {
kfree(thpsize);
goto err;
}
ret = sysfs_add_group(&thpsize->kobj, &any_ctrl_attr_grp);
if (ret)
goto err_put;
ret = sysfs_add_group(&thpsize->kobj, &any_stats_attr_grp);
if (ret)
goto err_put;
if (BIT(order) & THP_ORDERS_ALL_ANON) {
ret = sysfs_add_group(&thpsize->kobj, &anon_ctrl_attr_grp);
if (ret)
goto err_put;
ret = sysfs_add_group(&thpsize->kobj, &anon_stats_attr_grp);
if (ret)
goto err_put;
}
if (BIT(order) & THP_ORDERS_ALL_FILE_DEFAULT) {
ret = sysfs_add_group(&thpsize->kobj, &file_ctrl_attr_grp);
if (ret)
goto err_put;
ret = sysfs_add_group(&thpsize->kobj, &file_stats_attr_grp);
if (ret)
goto err_put;
}
return thpsize;
err_put:
kobject_put(&thpsize->kobj);
err:
return ERR_PTR(ret);
}
static void thpsize_release(struct kobject *kobj)
{
kfree(to_thpsize(kobj));
}
static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
{
int err;
struct thpsize *thpsize;
unsigned long orders;
int order;
/*
* Default to setting PMD-sized THP to inherit the global setting and
* disable all other sizes. powerpc's PMD_ORDER isn't a compile-time
* constant so we have to do this here.
*/
if (!anon_orders_configured)
huge_anon_orders_inherit = BIT(PMD_ORDER);
*hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
if (unlikely(!*hugepage_kobj)) {
pr_err("failed to create transparent hugepage kobject\n");
return -ENOMEM;
}
err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
if (err) {
pr_err("failed to register transparent hugepage group\n");
goto delete_obj;
}
err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
if (err) {
pr_err("failed to register transparent hugepage group\n");
goto remove_hp_group;
}
orders = THP_ORDERS_ALL_ANON | THP_ORDERS_ALL_FILE_DEFAULT;
order = highest_order(orders);
while (orders) {
thpsize = thpsize_create(order, *hugepage_kobj);
if (IS_ERR(thpsize)) {
pr_err("failed to create thpsize for order %d\n", order);
err = PTR_ERR(thpsize);
goto remove_all;
}
list_add(&thpsize->node, &thpsize_list);
order = next_order(&orders, order);
}
return 0;
remove_all:
hugepage_exit_sysfs(*hugepage_kobj);
return err;
remove_hp_group:
sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
delete_obj:
kobject_put(*hugepage_kobj);
return err;
}
static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
{
struct thpsize *thpsize, *tmp;
list_for_each_entry_safe(thpsize, tmp, &thpsize_list, node) {
list_del(&thpsize->node);
kobject_put(&thpsize->kobj);
}
sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
kobject_put(hugepage_kobj);
}
#else
static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
{
return 0;
}
static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
{
}
#endif /* CONFIG_SYSFS */
static int __init thp_shrinker_init(void)
{
huge_zero_page_shrinker = shrinker_alloc(0, "thp-zero");
if (!huge_zero_page_shrinker)
return -ENOMEM;
deferred_split_shrinker = shrinker_alloc(SHRINKER_NUMA_AWARE |
SHRINKER_MEMCG_AWARE |
SHRINKER_NONSLAB,
"thp-deferred_split");
if (!deferred_split_shrinker) {
shrinker_free(huge_zero_page_shrinker);
return -ENOMEM;
}
huge_zero_page_shrinker->count_objects = shrink_huge_zero_page_count;
huge_zero_page_shrinker->scan_objects = shrink_huge_zero_page_scan;
shrinker_register(huge_zero_page_shrinker);
deferred_split_shrinker->count_objects = deferred_split_count;
deferred_split_shrinker->scan_objects = deferred_split_scan;
shrinker_register(deferred_split_shrinker);
return 0;
}
static void __init thp_shrinker_exit(void)
{
shrinker_free(huge_zero_page_shrinker);
shrinker_free(deferred_split_shrinker);
}
static int __init hugepage_init(void)
{
int err;
struct kobject *hugepage_kobj;
if (!has_transparent_hugepage()) {
transparent_hugepage_flags = 1 << TRANSPARENT_HUGEPAGE_UNSUPPORTED;
return -EINVAL;
}
/*
* hugepages can't be allocated by the buddy allocator
*/
MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER > MAX_PAGE_ORDER);
err = hugepage_init_sysfs(&hugepage_kobj);
if (err)
goto err_sysfs;
err = khugepaged_init();
if (err)
goto err_slab;
err = thp_shrinker_init();
if (err)
goto err_shrinker;
/*
* By default disable transparent hugepages on smaller systems,
* where the extra memory used could hurt more than TLB overhead
* is likely to save. The admin can still enable it through /sys.
*/
if (totalram_pages() < (512 << (20 - PAGE_SHIFT))) {
transparent_hugepage_flags = 0;
return 0;
}
err = start_stop_khugepaged();
if (err)
goto err_khugepaged;
return 0;
err_khugepaged:
thp_shrinker_exit();
err_shrinker:
khugepaged_destroy();
err_slab:
hugepage_exit_sysfs(hugepage_kobj);
err_sysfs:
return err;
}
subsys_initcall(hugepage_init);
static int __init setup_transparent_hugepage(char *str)
{
int ret = 0;
if (!str)
goto out;
if (!strcmp(str, "always")) {
set_bit(TRANSPARENT_HUGEPAGE_FLAG,
&transparent_hugepage_flags);
clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
&transparent_hugepage_flags);
ret = 1;
} else if (!strcmp(str, "madvise")) {
clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
&transparent_hugepage_flags);
set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
&transparent_hugepage_flags);
ret = 1;
} else if (!strcmp(str, "never")) {
clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
&transparent_hugepage_flags);
clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
&transparent_hugepage_flags);
ret = 1;
}
out:
if (!ret)
pr_warn("transparent_hugepage= cannot parse, ignored\n");
return ret;
}
__setup("transparent_hugepage=", setup_transparent_hugepage);
static char str_dup[PAGE_SIZE] __initdata;
static int __init setup_thp_anon(char *str)
{
char *token, *range, *policy, *subtoken;
unsigned long always, inherit, madvise;
char *start_size, *end_size;
int start, end, nr;
char *p;
if (!str || strlen(str) + 1 > PAGE_SIZE)
goto err;
strscpy(str_dup, str);
always = huge_anon_orders_always;
madvise = huge_anon_orders_madvise;
inherit = huge_anon_orders_inherit;
p = str_dup;
while ((token = strsep(&p, ";")) != NULL) {
range = strsep(&token, ":");
policy = token;
if (!policy)
goto err;
while ((subtoken = strsep(&range, ",")) != NULL) {
if (strchr(subtoken, '-')) {
start_size = strsep(&subtoken, "-");
end_size = subtoken;
start = get_order_from_str(start_size, THP_ORDERS_ALL_ANON);
end = get_order_from_str(end_size, THP_ORDERS_ALL_ANON);
} else {
start_size = end_size = subtoken;
start = end = get_order_from_str(subtoken,
THP_ORDERS_ALL_ANON);
}
if (start == -EINVAL) {
pr_err("invalid size %s in thp_anon boot parameter\n", start_size);
goto err;
}
if (end == -EINVAL) {
pr_err("invalid size %s in thp_anon boot parameter\n", end_size);
goto err;
}
if (start < 0 || end < 0 || start > end)
goto err;
nr = end - start + 1;
if (!strcmp(policy, "always")) {
bitmap_set(&always, start, nr);
bitmap_clear(&inherit, start, nr);
bitmap_clear(&madvise, start, nr);
} else if (!strcmp(policy, "madvise")) {
bitmap_set(&madvise, start, nr);
bitmap_clear(&inherit, start, nr);
bitmap_clear(&always, start, nr);
} else if (!strcmp(policy, "inherit")) {
bitmap_set(&inherit, start, nr);
bitmap_clear(&madvise, start, nr);
bitmap_clear(&always, start, nr);
} else if (!strcmp(policy, "never")) {
bitmap_clear(&inherit, start, nr);
bitmap_clear(&madvise, start, nr);
bitmap_clear(&always, start, nr);
} else {
pr_err("invalid policy %s in thp_anon boot parameter\n", policy);
goto err;
}
}
}
huge_anon_orders_always = always;
huge_anon_orders_madvise = madvise;
huge_anon_orders_inherit = inherit;
anon_orders_configured = true;
return 1;
err:
pr_warn("thp_anon=%s: error parsing string, ignoring setting\n", str);
return 0;
}
__setup("thp_anon=", setup_thp_anon);
pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
{
if (likely(vma->vm_flags & VM_WRITE))
pmd = pmd_mkwrite(pmd, vma);
return pmd;
}
#ifdef CONFIG_MEMCG
static inline
struct deferred_split *get_deferred_split_queue(struct folio *folio)
{
struct mem_cgroup *memcg = folio_memcg(folio);
struct pglist_data *pgdat = NODE_DATA(folio_nid(folio));
if (memcg)
return &memcg->deferred_split_queue;
else
return &pgdat->deferred_split_queue;
}
#else
static inline
struct deferred_split *get_deferred_split_queue(struct folio *folio)
{
struct pglist_data *pgdat = NODE_DATA(folio_nid(folio));
return &pgdat->deferred_split_queue;
}
#endif
static inline bool is_transparent_hugepage(const struct folio *folio)
{
if (!folio_test_large(folio))
return false;
return is_huge_zero_folio(folio) ||
folio_test_large_rmappable(folio);
}
static unsigned long __thp_get_unmapped_area(struct file *filp,
unsigned long addr, unsigned long len,
loff_t off, unsigned long flags, unsigned long size,
vm_flags_t vm_flags)
{
loff_t off_end = off + len;
loff_t off_align = round_up(off, size);
unsigned long len_pad, ret, off_sub;
if (!IS_ENABLED(CONFIG_64BIT) || in_compat_syscall())
return 0;
if (off_end <= off_align || (off_end - off_align) < size)
return 0;
len_pad = len + size;
if (len_pad < len || (off + len_pad) < off)
return 0;
ret = mm_get_unmapped_area_vmflags(current->mm, filp, addr, len_pad,
off >> PAGE_SHIFT, flags, vm_flags);
/*
* The failure might be due to length padding. The caller will retry
* without the padding.
*/
if (IS_ERR_VALUE(ret))
return 0;
/*
* Do not try to align to THP boundary if allocation at the address
* hint succeeds.
*/
if (ret == addr)
return addr;
off_sub = (off - ret) & (size - 1);
if (test_bit(MMF_TOPDOWN, &current->mm->flags) && !off_sub)
return ret + size;
ret += off_sub;
return ret;
}
unsigned long thp_get_unmapped_area_vmflags(struct file *filp, unsigned long addr,
unsigned long len, unsigned long pgoff, unsigned long flags,
vm_flags_t vm_flags)
{
unsigned long ret;
loff_t off = (loff_t)pgoff << PAGE_SHIFT;
ret = __thp_get_unmapped_area(filp, addr, len, off, flags, PMD_SIZE, vm_flags);
if (ret)
return ret;
return mm_get_unmapped_area_vmflags(current->mm, filp, addr, len, pgoff, flags,
vm_flags);
}
unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
unsigned long len, unsigned long pgoff, unsigned long flags)
{
return thp_get_unmapped_area_vmflags(filp, addr, len, pgoff, flags, 0);
}
EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
static struct folio *vma_alloc_anon_folio_pmd(struct vm_area_struct *vma,
unsigned long addr)
{
gfp_t gfp = vma_thp_gfp_mask(vma);
const int order = HPAGE_PMD_ORDER;
struct folio *folio;
folio = vma_alloc_folio(gfp, order, vma, addr & HPAGE_PMD_MASK);
if (unlikely(!folio)) {
count_vm_event(THP_FAULT_FALLBACK);
count_mthp_stat(order, MTHP_STAT_ANON_FAULT_FALLBACK);
return NULL;
}
VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
if (mem_cgroup_charge(folio, vma->vm_mm, gfp)) {
folio_put(folio);
count_vm_event(THP_FAULT_FALLBACK);
count_vm_event(THP_FAULT_FALLBACK_CHARGE);
count_mthp_stat(order, MTHP_STAT_ANON_FAULT_FALLBACK);
count_mthp_stat(order, MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE);
return NULL;
}
folio_throttle_swaprate(folio, gfp);
/*
* When a folio is not zeroed during allocation (__GFP_ZERO not used)
* or user folios require special handling, folio_zero_user() is used to
* make sure that the page corresponding to the faulting address will be
* hot in the cache after zeroing.
*/
if (user_alloc_needs_zeroing())
folio_zero_user(folio, addr);
/*
* The memory barrier inside __folio_mark_uptodate makes sure that
* folio_zero_user writes become visible before the set_pmd_at()
* write.
*/
__folio_mark_uptodate(folio);
return folio;
}
static void map_anon_folio_pmd(struct folio *folio, pmd_t *pmd,
struct vm_area_struct *vma, unsigned long haddr)
{
pmd_t entry;
entry = mk_huge_pmd(&folio->page, vma->vm_page_prot);
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
folio_add_new_anon_rmap(folio, vma, haddr, RMAP_EXCLUSIVE);
folio_add_lru_vma(folio, vma);
set_pmd_at(vma->vm_mm, haddr, pmd, entry);
update_mmu_cache_pmd(vma, haddr, pmd);
add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
count_vm_event(THP_FAULT_ALLOC);
count_mthp_stat(HPAGE_PMD_ORDER, MTHP_STAT_ANON_FAULT_ALLOC);
count_memcg_event_mm(vma->vm_mm, THP_FAULT_ALLOC);
}
static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf)
{
unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
struct vm_area_struct *vma = vmf->vma;
struct folio *folio;
pgtable_t pgtable;
vm_fault_t ret = 0;
folio = vma_alloc_anon_folio_pmd(vma, vmf->address);
if (unlikely(!folio))
return VM_FAULT_FALLBACK;
pgtable = pte_alloc_one(vma->vm_mm);
if (unlikely(!pgtable)) {
ret = VM_FAULT_OOM;
goto release;
}
vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
if (unlikely(!pmd_none(*vmf->pmd))) {
goto unlock_release;
} else {
ret = check_stable_address_space(vma->vm_mm);
if (ret)
goto unlock_release;
/* Deliver the page fault to userland */
if (userfaultfd_missing(vma)) {
spin_unlock(vmf->ptl);
folio_put(folio);
pte_free(vma->vm_mm, pgtable);
ret = handle_userfault(vmf, VM_UFFD_MISSING);
VM_BUG_ON(ret & VM_FAULT_FALLBACK);
return ret;
}
pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
map_anon_folio_pmd(folio, vmf->pmd, vma, haddr);
mm_inc_nr_ptes(vma->vm_mm);
deferred_split_folio(folio, false);
spin_unlock(vmf->ptl);
}
return 0;
unlock_release:
spin_unlock(vmf->ptl);
release:
if (pgtable)
pte_free(vma->vm_mm, pgtable);
folio_put(folio);
return ret;
}
/*
* always: directly stall for all thp allocations
* defer: wake kswapd and fail if not immediately available
* defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
* fail if not immediately available
* madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
* available
* never: never stall for any thp allocation
*/
gfp_t vma_thp_gfp_mask(struct vm_area_struct *vma)
{
const bool vma_madvised = vma && (vma->vm_flags & VM_HUGEPAGE);
/* Always do synchronous compaction */
if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
/* Kick kcompactd and fail quickly */
if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
/* Synchronous compaction if madvised, otherwise kick kcompactd */
if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
return GFP_TRANSHUGE_LIGHT |
(vma_madvised ? __GFP_DIRECT_RECLAIM :
__GFP_KSWAPD_RECLAIM);
/* Only do synchronous compaction if madvised */
if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
return GFP_TRANSHUGE_LIGHT |
(vma_madvised ? __GFP_DIRECT_RECLAIM : 0);
return GFP_TRANSHUGE_LIGHT;
}
/* Caller must hold page table lock. */
static void set_huge_zero_folio(pgtable_t pgtable, struct mm_struct *mm,
struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
struct folio *zero_folio)
{
pmd_t entry;
if (!pmd_none(*pmd))
return;
entry = mk_pmd(&zero_folio->page, vma->vm_page_prot);
entry = pmd_mkhuge(entry);
pgtable_trans_huge_deposit(mm, pmd, pgtable);
set_pmd_at(mm, haddr, pmd, entry);
mm_inc_nr_ptes(mm);
}
vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
vm_fault_t ret;
if (!thp_vma_suitable_order(vma, haddr, PMD_ORDER))
return VM_FAULT_FALLBACK;
ret = vmf_anon_prepare(vmf);
if (ret)
return ret;
khugepaged_enter_vma(vma, vma->vm_flags);
if (!(vmf->flags & FAULT_FLAG_WRITE) &&
!mm_forbids_zeropage(vma->vm_mm) &&
transparent_hugepage_use_zero_page()) {
pgtable_t pgtable;
struct folio *zero_folio;
vm_fault_t ret;
pgtable = pte_alloc_one(vma->vm_mm);
if (unlikely(!pgtable))
return VM_FAULT_OOM;
zero_folio = mm_get_huge_zero_folio(vma->vm_mm);
if (unlikely(!zero_folio)) {
pte_free(vma->vm_mm, pgtable);
count_vm_event(THP_FAULT_FALLBACK);
return VM_FAULT_FALLBACK;
}
vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
ret = 0;
if (pmd_none(*vmf->pmd)) {
ret = check_stable_address_space(vma->vm_mm);
if (ret) {
spin_unlock(vmf->ptl);
pte_free(vma->vm_mm, pgtable);
} else if (userfaultfd_missing(vma)) {
spin_unlock(vmf->ptl);
pte_free(vma->vm_mm, pgtable);
ret = handle_userfault(vmf, VM_UFFD_MISSING);
VM_BUG_ON(ret & VM_FAULT_FALLBACK);
} else {
set_huge_zero_folio(pgtable, vma->vm_mm, vma,
haddr, vmf->pmd, zero_folio);
update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
spin_unlock(vmf->ptl);
}
} else {
spin_unlock(vmf->ptl);
pte_free(vma->vm_mm, pgtable);
}
return ret;
}
return __do_huge_pmd_anonymous_page(vmf);
}
static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
pgtable_t pgtable)
{
struct mm_struct *mm = vma->vm_mm;
pmd_t entry;
spinlock_t *ptl;
ptl = pmd_lock(mm, pmd);
if (!pmd_none(*pmd)) {
if (write) {
if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) {
WARN_ON_ONCE(!is_huge_zero_pmd(*pmd));
goto out_unlock;
}
entry = pmd_mkyoung(*pmd);
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
if (pmdp_set_access_flags(vma, addr, pmd, entry, 1))
update_mmu_cache_pmd(vma, addr, pmd);
}
goto out_unlock;
}
entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
if (pfn_t_devmap(pfn))
entry = pmd_mkdevmap(entry);
else
entry = pmd_mkspecial(entry);
if (write) {
entry = pmd_mkyoung(pmd_mkdirty(entry));
entry = maybe_pmd_mkwrite(entry, vma);
}
if (pgtable) {
pgtable_trans_huge_deposit(mm, pmd, pgtable);
mm_inc_nr_ptes(mm);
pgtable = NULL;
}
set_pmd_at(mm, addr, pmd, entry);
update_mmu_cache_pmd(vma, addr, pmd);
out_unlock:
spin_unlock(ptl);
if (pgtable)
pte_free(mm, pgtable);
}
/**
* vmf_insert_pfn_pmd - insert a pmd size pfn
* @vmf: Structure describing the fault
* @pfn: pfn to insert
* @write: whether it's a write fault
*
* Insert a pmd size pfn. See vmf_insert_pfn() for additional info.
*
* Return: vm_fault_t value.
*/
vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, pfn_t pfn, bool write)
{
unsigned long addr = vmf->address & PMD_MASK;
struct vm_area_struct *vma = vmf->vma;
pgprot_t pgprot = vma->vm_page_prot;
pgtable_t pgtable = NULL;
/*
* If we had pmd_special, we could avoid all these restrictions,
* but we need to be consistent with PTEs and architectures that
* can't support a 'special' bit.
*/
BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
!pfn_t_devmap(pfn));
BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
(VM_PFNMAP|VM_MIXEDMAP));
BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
if (addr < vma->vm_start || addr >= vma->vm_end)
return VM_FAULT_SIGBUS;
if (arch_needs_pgtable_deposit()) {
pgtable = pte_alloc_one(vma->vm_mm);
if (!pgtable)
return VM_FAULT_OOM;
}
track_pfn_insert(vma, &pgprot, pfn);
insert_pfn_pmd(vma, addr, vmf->pmd, pfn, pgprot, write, pgtable);
return VM_FAULT_NOPAGE;
}
EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
{
if (likely(vma->vm_flags & VM_WRITE))
pud = pud_mkwrite(pud);
return pud;
}
static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
pud_t *pud, pfn_t pfn, bool write)
{
struct mm_struct *mm = vma->vm_mm;
pgprot_t prot = vma->vm_page_prot;
pud_t entry;
spinlock_t *ptl;
ptl = pud_lock(mm, pud);
if (!pud_none(*pud)) {
if (write) {
if (WARN_ON_ONCE(pud_pfn(*pud) != pfn_t_to_pfn(pfn)))
goto out_unlock;
entry = pud_mkyoung(*pud);
entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma);
if (pudp_set_access_flags(vma, addr, pud, entry, 1))
update_mmu_cache_pud(vma, addr, pud);
}
goto out_unlock;
}
entry = pud_mkhuge(pfn_t_pud(pfn, prot));
if (pfn_t_devmap(pfn))
entry = pud_mkdevmap(entry);
else
entry = pud_mkspecial(entry);
if (write) {
entry = pud_mkyoung(pud_mkdirty(entry));
entry = maybe_pud_mkwrite(entry, vma);
}
set_pud_at(mm, addr, pud, entry);
update_mmu_cache_pud(vma, addr, pud);
out_unlock:
spin_unlock(ptl);
}
/**
* vmf_insert_pfn_pud - insert a pud size pfn
* @vmf: Structure describing the fault
* @pfn: pfn to insert
* @write: whether it's a write fault
*
* Insert a pud size pfn. See vmf_insert_pfn() for additional info.
*
* Return: vm_fault_t value.
*/
vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write)
{
unsigned long addr = vmf->address & PUD_MASK;
struct vm_area_struct *vma = vmf->vma;
pgprot_t pgprot = vma->vm_page_prot;
/*
* If we had pud_special, we could avoid all these restrictions,
* but we need to be consistent with PTEs and architectures that
* can't support a 'special' bit.
*/
BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
!pfn_t_devmap(pfn));
BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
(VM_PFNMAP|VM_MIXEDMAP));
BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
if (addr < vma->vm_start || addr >= vma->vm_end)
return VM_FAULT_SIGBUS;
track_pfn_insert(vma, &pgprot, pfn);
insert_pfn_pud(vma, addr, vmf->pud, pfn, write);
return VM_FAULT_NOPAGE;
}
EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
pmd_t *pmd, bool write)
{
pmd_t _pmd;
_pmd = pmd_mkyoung(*pmd);
if (write)
_pmd = pmd_mkdirty(_pmd);
if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
pmd, _pmd, write))
update_mmu_cache_pmd(vma, addr, pmd);
}
struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
pmd_t *pmd, int flags, struct dev_pagemap **pgmap)
{
unsigned long pfn = pmd_pfn(*pmd);
struct mm_struct *mm = vma->vm_mm;
struct page *page;
int ret;
assert_spin_locked(pmd_lockptr(mm, pmd));
if (flags & FOLL_WRITE && !pmd_write(*pmd))
return NULL;
if (pmd_present(*pmd) && pmd_devmap(*pmd))
/* pass */;
else
return NULL;
if (flags & FOLL_TOUCH)
touch_pmd(vma, addr, pmd, flags & FOLL_WRITE);
/*
* device mapped pages can only be returned if the
* caller will manage the page reference count.
*/
if (!(flags & (FOLL_GET | FOLL_PIN)))
return ERR_PTR(-EEXIST);
pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
*pgmap = get_dev_pagemap(pfn, *pgmap);
if (!*pgmap)
return ERR_PTR(-EFAULT);
page = pfn_to_page(pfn);
ret = try_grab_folio(page_folio(page), 1, flags);
if (ret)
page = ERR_PTR(ret);
return page;
}
int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma)
{
spinlock_t *dst_ptl, *src_ptl;
struct page *src_page;
struct folio *src_folio;
pmd_t pmd;
pgtable_t pgtable = NULL;
int ret = -ENOMEM;
pmd = pmdp_get_lockless(src_pmd);
if (unlikely(pmd_present(pmd) && pmd_special(pmd))) {
dst_ptl = pmd_lock(dst_mm, dst_pmd);
src_ptl = pmd_lockptr(src_mm, src_pmd);
spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
/*
* No need to recheck the pmd, it can't change with write
* mmap lock held here.
*
* Meanwhile, making sure it's not a CoW VMA with writable
* mapping, otherwise it means either the anon page wrongly
* applied special bit, or we made the PRIVATE mapping be
* able to wrongly write to the backend MMIO.
*/
VM_WARN_ON_ONCE(is_cow_mapping(src_vma->vm_flags) && pmd_write(pmd));
goto set_pmd;
}
/* Skip if can be re-fill on fault */
if (!vma_is_anonymous(dst_vma))
return 0;
pgtable = pte_alloc_one(dst_mm);
if (unlikely(!pgtable))
goto out;
dst_ptl = pmd_lock(dst_mm, dst_pmd);
src_ptl = pmd_lockptr(src_mm, src_pmd);
spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
ret = -EAGAIN;
pmd = *src_pmd;
#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
if (unlikely(is_swap_pmd(pmd))) {
swp_entry_t entry = pmd_to_swp_entry(pmd);
VM_BUG_ON(!is_pmd_migration_entry(pmd));
if (!is_readable_migration_entry(entry)) {
entry = make_readable_migration_entry(
swp_offset(entry));
pmd = swp_entry_to_pmd(entry);
if (pmd_swp_soft_dirty(*src_pmd))
pmd = pmd_swp_mksoft_dirty(pmd);
if (pmd_swp_uffd_wp(*src_pmd))
pmd = pmd_swp_mkuffd_wp(pmd);
set_pmd_at(src_mm, addr, src_pmd, pmd);
}
add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
mm_inc_nr_ptes(dst_mm);
pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
if (!userfaultfd_wp(dst_vma))
pmd = pmd_swp_clear_uffd_wp(pmd);
set_pmd_at(dst_mm, addr, dst_pmd, pmd);
ret = 0;
goto out_unlock;
}
#endif
if (unlikely(!pmd_trans_huge(pmd))) {
pte_free(dst_mm, pgtable);
goto out_unlock;
}
/*
* When page table lock is held, the huge zero pmd should not be
* under splitting since we don't split the page itself, only pmd to
* a page table.
*/
if (is_huge_zero_pmd(pmd)) {
/*
* mm_get_huge_zero_folio() will never allocate a new
* folio here, since we already have a zero page to
* copy. It just takes a reference.
*/
mm_get_huge_zero_folio(dst_mm);
goto out_zero_page;
}
src_page = pmd_page(pmd);
VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
src_folio = page_folio(src_page);
folio_get(src_folio);
if (unlikely(folio_try_dup_anon_rmap_pmd(src_folio, src_page, src_vma))) {
/* Page maybe pinned: split and retry the fault on PTEs. */
folio_put(src_folio);
pte_free(dst_mm, pgtable);
spin_unlock(src_ptl);
spin_unlock(dst_ptl);
__split_huge_pmd(src_vma, src_pmd, addr, false, NULL);
return -EAGAIN;
}
add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
out_zero_page:
mm_inc_nr_ptes(dst_mm);
pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
pmdp_set_wrprotect(src_mm, addr, src_pmd);
if (!userfaultfd_wp(dst_vma))
pmd = pmd_clear_uffd_wp(pmd);
pmd = pmd_wrprotect(pmd);
set_pmd:
pmd = pmd_mkold(pmd);
set_pmd_at(dst_mm, addr, dst_pmd, pmd);
ret = 0;
out_unlock:
spin_unlock(src_ptl);
spin_unlock(dst_ptl);
out:
return ret;
}
#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
void touch_pud(struct vm_area_struct *vma, unsigned long addr,
pud_t *pud, bool write)
{
pud_t _pud;
_pud = pud_mkyoung(*pud);
if (write)
_pud = pud_mkdirty(_pud);
if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
pud, _pud, write))
update_mmu_cache_pud(vma, addr, pud);
}
int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
struct vm_area_struct *vma)
{
spinlock_t *dst_ptl, *src_ptl;
pud_t pud;
int ret;
dst_ptl = pud_lock(dst_mm, dst_pud);
src_ptl = pud_lockptr(src_mm, src_pud);
spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
ret = -EAGAIN;
pud = *src_pud;
if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
goto out_unlock;
/*
* TODO: once we support anonymous pages, use
* folio_try_dup_anon_rmap_*() and split if duplicating fails.
*/
if (is_cow_mapping(vma->vm_flags) && pud_write(pud)) {
pudp_set_wrprotect(src_mm, addr, src_pud);
pud = pud_wrprotect(pud);
}
pud = pud_mkold(pud);
set_pud_at(dst_mm, addr, dst_pud, pud);
ret = 0;
out_unlock:
spin_unlock(src_ptl);
spin_unlock(dst_ptl);
return ret;
}
void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
{
bool write = vmf->flags & FAULT_FLAG_WRITE;
vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
if (unlikely(!pud_same(*vmf->pud, orig_pud)))
goto unlock;
touch_pud(vmf->vma, vmf->address, vmf->pud, write);
unlock:
spin_unlock(vmf->ptl);
}
#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
void huge_pmd_set_accessed(struct vm_fault *vmf)
{
bool write = vmf->flags & FAULT_FLAG_WRITE;
vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
if (unlikely(!pmd_same(*vmf->pmd, vmf->orig_pmd)))
goto unlock;
touch_pmd(vmf->vma, vmf->address, vmf->pmd, write);
unlock:
spin_unlock(vmf->ptl);
}
static vm_fault_t do_huge_zero_wp_pmd(struct vm_fault *vmf)
{
unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
struct vm_area_struct *vma = vmf->vma;
struct mmu_notifier_range range;
struct folio *folio;
vm_fault_t ret = 0;
folio = vma_alloc_anon_folio_pmd(vma, vmf->address);
if (unlikely(!folio))
return VM_FAULT_FALLBACK;
mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm, haddr,
haddr + HPAGE_PMD_SIZE);
mmu_notifier_invalidate_range_start(&range);
vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
if (unlikely(!pmd_same(pmdp_get(vmf->pmd), vmf->orig_pmd)))
goto release;
ret = check_stable_address_space(vma->vm_mm);
if (ret)
goto release;
(void)pmdp_huge_clear_flush(vma, haddr, vmf->pmd);
map_anon_folio_pmd(folio, vmf->pmd, vma, haddr);
goto unlock;
release:
folio_put(folio);
unlock:
spin_unlock(vmf->ptl);
mmu_notifier_invalidate_range_end(&range);
return ret;
}
vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf)
{
const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;
struct vm_area_struct *vma = vmf->vma;
struct folio *folio;
struct page *page;
unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
pmd_t orig_pmd = vmf->orig_pmd;
vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
VM_BUG_ON_VMA(!vma->anon_vma, vma);
if (is_huge_zero_pmd(orig_pmd)) {
vm_fault_t ret = do_huge_zero_wp_pmd(vmf);
if (!(ret & VM_FAULT_FALLBACK))
return ret;
/* Fallback to splitting PMD if THP cannot be allocated */
goto fallback;
}
spin_lock(vmf->ptl);
if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
spin_unlock(vmf->ptl);
return 0;
}
page = pmd_page(orig_pmd);
folio = page_folio(page);
VM_BUG_ON_PAGE(!PageHead(page), page);
/* Early check when only holding the PT lock. */
if (PageAnonExclusive(page))
goto reuse;
if (!folio_trylock(folio)) {
folio_get(folio);
spin_unlock(vmf->ptl);
folio_lock(folio);
spin_lock(vmf->ptl);
if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
spin_unlock(vmf->ptl);
folio_unlock(folio);
folio_put(folio);
return 0;
}
folio_put(folio);
}
/* Recheck after temporarily dropping the PT lock. */
if (PageAnonExclusive(page)) {
folio_unlock(folio);
goto reuse;
}
/*
* See do_wp_page(): we can only reuse the folio exclusively if
* there are no additional references. Note that we always drain
* the LRU cache immediately after adding a THP.
*/
if (folio_ref_count(folio) >
1 + folio_test_swapcache(folio) * folio_nr_pages(folio))
goto unlock_fallback;
if (folio_test_swapcache(folio))
folio_free_swap(folio);
if (folio_ref_count(folio) == 1) {
pmd_t entry;
folio_move_anon_rmap(folio, vma);
SetPageAnonExclusive(page);
folio_unlock(folio);
reuse:
if (unlikely(unshare)) {
spin_unlock(vmf->ptl);
return 0;
}
entry = pmd_mkyoung(orig_pmd);
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry, 1))
update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
spin_unlock(vmf->ptl);
return 0;
}
unlock_fallback:
folio_unlock(folio);
spin_unlock(vmf->ptl);
fallback:
__split_huge_pmd(vma, vmf->pmd, vmf->address, false, NULL);
return VM_FAULT_FALLBACK;
}
static inline bool can_change_pmd_writable(struct vm_area_struct *vma,
unsigned long addr, pmd_t pmd)
{
struct page *page;
if (WARN_ON_ONCE(!(vma->vm_flags & VM_WRITE)))
return false;
/* Don't touch entries that are not even readable (NUMA hinting). */
if (pmd_protnone(pmd))
return false;
/* Do we need write faults for softdirty tracking? */
if (pmd_needs_soft_dirty_wp(vma, pmd))
return false;
/* Do we need write faults for uffd-wp tracking? */
if (userfaultfd_huge_pmd_wp(vma, pmd))
return false;
if (!(vma->vm_flags & VM_SHARED)) {
/* See can_change_pte_writable(). */
page = vm_normal_page_pmd(vma, addr, pmd);
return page && PageAnon(page) && PageAnonExclusive(page);
}
/* See can_change_pte_writable(). */
return pmd_dirty(pmd);
}
/* NUMA hinting page fault entry point for trans huge pmds */
vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
struct folio *folio;
unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
int nid = NUMA_NO_NODE;
int target_nid, last_cpupid;
pmd_t pmd, old_pmd;
bool writable = false;
int flags = 0;
vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
old_pmd = pmdp_get(vmf->pmd);
if (unlikely(!pmd_same(old_pmd, vmf->orig_pmd))) {
spin_unlock(vmf->ptl);
return 0;
}
pmd = pmd_modify(old_pmd, vma->vm_page_prot);
/*
* Detect now whether the PMD could be writable; this information
* is only valid while holding the PT lock.
*/
writable = pmd_write(pmd);
if (!writable && vma_wants_manual_pte_write_upgrade(vma) &&
can_change_pmd_writable(vma, vmf->address, pmd))
writable = true;
folio = vm_normal_folio_pmd(vma, haddr, pmd);
if (!folio)
goto out_map;
nid = folio_nid(folio);
target_nid = numa_migrate_check(folio, vmf, haddr, &flags, writable,
&last_cpupid);
if (target_nid == NUMA_NO_NODE)
goto out_map;
if (migrate_misplaced_folio_prepare(folio, vma, target_nid)) {
flags |= TNF_MIGRATE_FAIL;
goto out_map;
}
/* The folio is isolated and isolation code holds a folio reference. */
spin_unlock(vmf->ptl);
writable = false;
if (!migrate_misplaced_folio(folio, vma, target_nid)) {
flags |= TNF_MIGRATED;
nid = target_nid;
task_numa_fault(last_cpupid, nid, HPAGE_PMD_NR, flags);
return 0;
}
flags |= TNF_MIGRATE_FAIL;
vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
if (unlikely(!pmd_same(pmdp_get(vmf->pmd), vmf->orig_pmd))) {
spin_unlock(vmf->ptl);
return 0;
}
out_map:
/* Restore the PMD */
pmd = pmd_modify(pmdp_get(vmf->pmd), vma->vm_page_prot);
pmd = pmd_mkyoung(pmd);
if (writable)
pmd = pmd_mkwrite(pmd, vma);
set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
spin_unlock(vmf->ptl);
if (nid != NUMA_NO_NODE)
task_numa_fault(last_cpupid, nid, HPAGE_PMD_NR, flags);
return 0;
}
/*
* Return true if we do MADV_FREE successfully on entire pmd page.
* Otherwise, return false.
*/
bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
pmd_t *pmd, unsigned long addr, unsigned long next)
{
spinlock_t *ptl;
pmd_t orig_pmd;
struct folio *folio;
struct mm_struct *mm = tlb->mm;
bool ret = false;
tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
ptl = pmd_trans_huge_lock(pmd, vma);
if (!ptl)
goto out_unlocked;
orig_pmd = *pmd;
if (is_huge_zero_pmd(orig_pmd))
goto out;
if (unlikely(!pmd_present(orig_pmd))) {
VM_BUG_ON(thp_migration_supported() &&
!is_pmd_migration_entry(orig_pmd));
goto out;
}
folio = pmd_folio(orig_pmd);
/*
* If other processes are mapping this folio, we couldn't discard
* the folio unless they all do MADV_FREE so let's skip the folio.
*/
if (folio_likely_mapped_shared(folio))
goto out;
if (!folio_trylock(folio))
goto out;
/*
* If user want to discard part-pages of THP, split it so MADV_FREE
* will deactivate only them.
*/
if (next - addr != HPAGE_PMD_SIZE) {
folio_get(folio);
spin_unlock(ptl);
split_folio(folio);
folio_unlock(folio);
folio_put(folio);
goto out_unlocked;
}
if (folio_test_dirty(folio))
folio_clear_dirty(folio);
folio_unlock(folio);
if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
pmdp_invalidate(vma, addr, pmd);
orig_pmd = pmd_mkold(orig_pmd);
orig_pmd = pmd_mkclean(orig_pmd);
set_pmd_at(mm, addr, pmd, orig_pmd);
tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
}
folio_mark_lazyfree(folio);
ret = true;
out:
spin_unlock(ptl);
out_unlocked:
return ret;
}
static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
{
pgtable_t pgtable;
pgtable = pgtable_trans_huge_withdraw(mm, pmd);
pte_free(mm, pgtable);
mm_dec_nr_ptes(mm);
}
int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
pmd_t *pmd, unsigned long addr)
{
pmd_t orig_pmd;
spinlock_t *ptl;
tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
ptl = __pmd_trans_huge_lock(pmd, vma);
if (!ptl)
return 0;
/*
* For architectures like ppc64 we look at deposited pgtable
* when calling pmdp_huge_get_and_clear. So do the
* pgtable_trans_huge_withdraw after finishing pmdp related
* operations.
*/
orig_pmd = pmdp_huge_get_and_clear_full(vma, addr, pmd,
tlb->fullmm);
arch_check_zapped_pmd(vma, orig_pmd);
tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
if (vma_is_special_huge(vma)) {
if (arch_needs_pgtable_deposit())
zap_deposited_table(tlb->mm, pmd);
spin_unlock(ptl);
} else if (is_huge_zero_pmd(orig_pmd)) {
zap_deposited_table(tlb->mm, pmd);
spin_unlock(ptl);
} else {
struct folio *folio = NULL;
int flush_needed = 1;
if (pmd_present(orig_pmd)) {
struct page *page = pmd_page(orig_pmd);
folio = page_folio(page);
folio_remove_rmap_pmd(folio, page, vma);
WARN_ON_ONCE(folio_mapcount(folio) < 0);
VM_BUG_ON_PAGE(!PageHead(page), page);
} else if (thp_migration_supported()) {
swp_entry_t entry;
VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
entry = pmd_to_swp_entry(orig_pmd);
folio = pfn_swap_entry_folio(entry);
flush_needed = 0;
} else
WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
if (folio_test_anon(folio)) {
zap_deposited_table(tlb->mm, pmd);
add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
} else {
if (arch_needs_pgtable_deposit())
zap_deposited_table(tlb->mm, pmd);
add_mm_counter(tlb->mm, mm_counter_file(folio),
-HPAGE_PMD_NR);
}
spin_unlock(ptl);
if (flush_needed)
tlb_remove_page_size(tlb, &folio->page, HPAGE_PMD_SIZE);
}
return 1;
}
#ifndef pmd_move_must_withdraw
static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
spinlock_t *old_pmd_ptl,
struct vm_area_struct *vma)
{
/*
* With split pmd lock we also need to move preallocated
* PTE page table if new_pmd is on different PMD page table.
*
* We also don't deposit and withdraw tables for file pages.
*/
return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
}
#endif
static pmd_t move_soft_dirty_pmd(pmd_t pmd)
{
#ifdef CONFIG_MEM_SOFT_DIRTY
if (unlikely(is_pmd_migration_entry(pmd)))
pmd = pmd_swp_mksoft_dirty(pmd);
else if (pmd_present(pmd))
pmd = pmd_mksoft_dirty(pmd);
#endif
return pmd;
}
bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd)
{
spinlock_t *old_ptl, *new_ptl;
pmd_t pmd;
struct mm_struct *mm = vma->vm_mm;
bool force_flush = false;
/*
* The destination pmd shouldn't be established, free_pgtables()
* should have released it; but move_page_tables() might have already
* inserted a page table, if racing against shmem/file collapse.
*/
if (!pmd_none(*new_pmd)) {
VM_BUG_ON(pmd_trans_huge(*new_pmd));
return false;
}
/*
* We don't have to worry about the ordering of src and dst
* ptlocks because exclusive mmap_lock prevents deadlock.
*/
old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
if (old_ptl) {
new_ptl = pmd_lockptr(mm, new_pmd);
if (new_ptl != old_ptl)
spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
if (pmd_present(pmd))
force_flush = true;
VM_BUG_ON(!pmd_none(*new_pmd));
if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
pgtable_t pgtable;
pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
}
pmd = move_soft_dirty_pmd(pmd);
set_pmd_at(mm, new_addr, new_pmd, pmd);
if (force_flush)
flush_pmd_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
if (new_ptl != old_ptl)
spin_unlock(new_ptl);
spin_unlock(old_ptl);
return true;
}
return false;
}
/*
* Returns
* - 0 if PMD could not be locked
* - 1 if PMD was locked but protections unchanged and TLB flush unnecessary
* or if prot_numa but THP migration is not supported
* - HPAGE_PMD_NR if protections changed and TLB flush necessary
*/
int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
pmd_t *pmd, unsigned long addr, pgprot_t newprot,
unsigned long cp_flags)
{
struct mm_struct *mm = vma->vm_mm;
spinlock_t *ptl;
pmd_t oldpmd, entry;
bool prot_numa = cp_flags & MM_CP_PROT_NUMA;
bool uffd_wp = cp_flags & MM_CP_UFFD_WP;
bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE;
int ret = 1;
tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
if (prot_numa && !thp_migration_supported())
return 1;
ptl = __pmd_trans_huge_lock(pmd, vma);
if (!ptl)
return 0;
#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
if (is_swap_pmd(*pmd)) {
swp_entry_t entry = pmd_to_swp_entry(*pmd);
struct folio *folio = pfn_swap_entry_folio(entry);
pmd_t newpmd;
VM_BUG_ON(!is_pmd_migration_entry(*pmd));
if (is_writable_migration_entry(entry)) {
/*
* A protection check is difficult so
* just be safe and disable write
*/
if (folio_test_anon(folio))
entry = make_readable_exclusive_migration_entry(swp_offset(entry));
else
entry = make_readable_migration_entry(swp_offset(entry));
newpmd = swp_entry_to_pmd(entry);
if (pmd_swp_soft_dirty(*pmd))
newpmd = pmd_swp_mksoft_dirty(newpmd);
} else {
newpmd = *pmd;
}
if (uffd_wp)
newpmd = pmd_swp_mkuffd_wp(newpmd);
else if (uffd_wp_resolve)
newpmd = pmd_swp_clear_uffd_wp(newpmd);
if (!pmd_same(*pmd, newpmd))
set_pmd_at(mm, addr, pmd, newpmd);
goto unlock;
}
#endif
if (prot_numa) {
struct folio *folio;
bool toptier;
/*
* Avoid trapping faults against the zero page. The read-only
* data is likely to be read-cached on the local CPU and
* local/remote hits to the zero page are not interesting.
*/
if (is_huge_zero_pmd(*pmd))
goto unlock;
if (pmd_protnone(*pmd))
goto unlock;
folio = pmd_folio(*pmd);
toptier = node_is_toptier(folio_nid(folio));
/*
* Skip scanning top tier node if normal numa
* balancing is disabled
*/
if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) &&
toptier)
goto unlock;
if (folio_use_access_time(folio))
folio_xchg_access_time(folio,
jiffies_to_msecs(jiffies));
}
/*
* In case prot_numa, we are under mmap_read_lock(mm). It's critical
* to not clear pmd intermittently to avoid race with MADV_DONTNEED
* which is also under mmap_read_lock(mm):
*
* CPU0: CPU1:
* change_huge_pmd(prot_numa=1)
* pmdp_huge_get_and_clear_notify()
* madvise_dontneed()
* zap_pmd_range()
* pmd_trans_huge(*pmd) == 0 (without ptl)
* // skip the pmd
* set_pmd_at();
* // pmd is re-established
*
* The race makes MADV_DONTNEED miss the huge pmd and don't clear it
* which may break userspace.
*
* pmdp_invalidate_ad() is required to make sure we don't miss
* dirty/young flags set by hardware.
*/
oldpmd = pmdp_invalidate_ad(vma, addr, pmd);
entry = pmd_modify(oldpmd, newprot);
if (uffd_wp)
entry = pmd_mkuffd_wp(entry);
else if (uffd_wp_resolve)
/*
* Leave the write bit to be handled by PF interrupt
* handler, then things like COW could be properly
* handled.
*/
entry = pmd_clear_uffd_wp(entry);
/* See change_pte_range(). */
if ((cp_flags & MM_CP_TRY_CHANGE_WRITABLE) && !pmd_write(entry) &&
can_change_pmd_writable(vma, addr, entry))
entry = pmd_mkwrite(entry, vma);
ret = HPAGE_PMD_NR;
set_pmd_at(mm, addr, pmd, entry);
if (huge_pmd_needs_flush(oldpmd, entry))
tlb_flush_pmd_range(tlb, addr, HPAGE_PMD_SIZE);
unlock:
spin_unlock(ptl);
return ret;
}
/*
* Returns:
*
* - 0: if pud leaf changed from under us
* - 1: if pud can be skipped
* - HPAGE_PUD_NR: if pud was successfully processed
*/
#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
int change_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
pud_t *pudp, unsigned long addr, pgprot_t newprot,
unsigned long cp_flags)
{
struct mm_struct *mm = vma->vm_mm;
pud_t oldpud, entry;
spinlock_t *ptl;
tlb_change_page_size(tlb, HPAGE_PUD_SIZE);
/* NUMA balancing doesn't apply to dax */
if (cp_flags & MM_CP_PROT_NUMA)
return 1;
/*
* Huge entries on userfault-wp only works with anonymous, while we
* don't have anonymous PUDs yet.
*/
if (WARN_ON_ONCE(cp_flags & MM_CP_UFFD_WP_ALL))
return 1;
ptl = __pud_trans_huge_lock(pudp, vma);
if (!ptl)
return 0;
/*
* Can't clear PUD or it can race with concurrent zapping. See
* change_huge_pmd().
*/
oldpud = pudp_invalidate(vma, addr, pudp);
entry = pud_modify(oldpud, newprot);
set_pud_at(mm, addr, pudp, entry);
tlb_flush_pud_range(tlb, addr, HPAGE_PUD_SIZE);
spin_unlock(ptl);
return HPAGE_PUD_NR;
}
#endif
#ifdef CONFIG_USERFAULTFD
/*
* The PT lock for src_pmd and dst_vma/src_vma (for reading) are locked by
* the caller, but it must return after releasing the page_table_lock.
* Just move the page from src_pmd to dst_pmd if possible.
* Return zero if succeeded in moving the page, -EAGAIN if it needs to be
* repeated by the caller, or other errors in case of failure.
*/
int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pmd_t dst_pmdval,
struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
unsigned long dst_addr, unsigned long src_addr)
{
pmd_t _dst_pmd, src_pmdval;
struct page *src_page;
struct folio *src_folio;
struct anon_vma *src_anon_vma;
spinlock_t *src_ptl, *dst_ptl;
pgtable_t src_pgtable;
struct mmu_notifier_range range;
int err = 0;
src_pmdval = *src_pmd;
src_ptl = pmd_lockptr(mm, src_pmd);
lockdep_assert_held(src_ptl);
vma_assert_locked(src_vma);
vma_assert_locked(dst_vma);
/* Sanity checks before the operation */
if (WARN_ON_ONCE(!pmd_none(dst_pmdval)) || WARN_ON_ONCE(src_addr & ~HPAGE_PMD_MASK) ||
WARN_ON_ONCE(dst_addr & ~HPAGE_PMD_MASK)) {
spin_unlock(src_ptl);
return -EINVAL;
}
if (!pmd_trans_huge(src_pmdval)) {
spin_unlock(src_ptl);
if (is_pmd_migration_entry(src_pmdval)) {
pmd_migration_entry_wait(mm, &src_pmdval);
return -EAGAIN;
}
return -ENOENT;
}
src_page = pmd_page(src_pmdval);
if (!is_huge_zero_pmd(src_pmdval)) {
if (unlikely(!PageAnonExclusive(src_page))) {
spin_unlock(src_ptl);
return -EBUSY;
}
src_folio = page_folio(src_page);
folio_get(src_folio);
} else
src_folio = NULL;
spin_unlock(src_ptl);
flush_cache_range(src_vma, src_addr, src_addr + HPAGE_PMD_SIZE);
mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, src_addr,
src_addr + HPAGE_PMD_SIZE);
mmu_notifier_invalidate_range_start(&range);
if (src_folio) {
folio_lock(src_folio);
/*
* split_huge_page walks the anon_vma chain without the page
* lock. Serialize against it with the anon_vma lock, the page
* lock is not enough.
*/
src_anon_vma = folio_get_anon_vma(src_folio);
if (!src_anon_vma) {
err = -EAGAIN;
goto unlock_folio;
}
anon_vma_lock_write(src_anon_vma);
} else
src_anon_vma = NULL;
dst_ptl = pmd_lockptr(mm, dst_pmd);
double_pt_lock(src_ptl, dst_ptl);
if (unlikely(!pmd_same(*src_pmd, src_pmdval) ||
!pmd_same(*dst_pmd, dst_pmdval))) {
err = -EAGAIN;
goto unlock_ptls;
}
if (src_folio) {
if (folio_maybe_dma_pinned(src_folio) ||
!PageAnonExclusive(&src_folio->page)) {
err = -EBUSY;
goto unlock_ptls;
}
if (WARN_ON_ONCE(!folio_test_head(src_folio)) ||
WARN_ON_ONCE(!folio_test_anon(src_folio))) {
err = -EBUSY;
goto unlock_ptls;
}
src_pmdval = pmdp_huge_clear_flush(src_vma, src_addr, src_pmd);
/* Folio got pinned from under us. Put it back and fail the move. */
if (folio_maybe_dma_pinned(src_folio)) {
set_pmd_at(mm, src_addr, src_pmd, src_pmdval);
err = -EBUSY;
goto unlock_ptls;
}
folio_move_anon_rmap(src_folio, dst_vma);
src_folio->index = linear_page_index(dst_vma, dst_addr);
_dst_pmd = mk_huge_pmd(&src_folio->page, dst_vma->vm_page_prot);
/* Follow mremap() behavior and treat the entry dirty after the move */
_dst_pmd = pmd_mkwrite(pmd_mkdirty(_dst_pmd), dst_vma);
} else {
src_pmdval = pmdp_huge_clear_flush(src_vma, src_addr, src_pmd);
_dst_pmd = mk_huge_pmd(src_page, dst_vma->vm_page_prot);
}
set_pmd_at(mm, dst_addr, dst_pmd, _dst_pmd);
src_pgtable = pgtable_trans_huge_withdraw(mm, src_pmd);
pgtable_trans_huge_deposit(mm, dst_pmd, src_pgtable);
unlock_ptls:
double_pt_unlock(src_ptl, dst_ptl);
if (src_anon_vma) {
anon_vma_unlock_write(src_anon_vma);
put_anon_vma(src_anon_vma);
}
unlock_folio:
/* unblock rmap walks */
if (src_folio)
folio_unlock(src_folio);
mmu_notifier_invalidate_range_end(&range);
if (src_folio)
folio_put(src_folio);
return err;
}
#endif /* CONFIG_USERFAULTFD */
/*
* Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
*
* Note that if it returns page table lock pointer, this routine returns without
* unlocking page table lock. So callers must unlock it.
*/
spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
{
spinlock_t *ptl;
ptl = pmd_lock(vma->vm_mm, pmd);
if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
pmd_devmap(*pmd)))
return ptl;
spin_unlock(ptl);
return NULL;
}
/*
* Returns page table lock pointer if a given pud maps a thp, NULL otherwise.
*
* Note that if it returns page table lock pointer, this routine returns without
* unlocking page table lock. So callers must unlock it.
*/
spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
{
spinlock_t *ptl;
ptl = pud_lock(vma->vm_mm, pud);
if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
return ptl;
spin_unlock(ptl);
return NULL;
}
#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
pud_t *pud, unsigned long addr)
{
spinlock_t *ptl;
pud_t orig_pud;
ptl = __pud_trans_huge_lock(pud, vma);
if (!ptl)
return 0;
orig_pud = pudp_huge_get_and_clear_full(vma, addr, pud, tlb->fullmm);
arch_check_zapped_pud(vma, orig_pud);
tlb_remove_pud_tlb_entry(tlb, pud, addr);
if (vma_is_special_huge(vma)) {
spin_unlock(ptl);
/* No zero page support yet */
} else {
/* No support for anonymous PUD pages yet */
BUG();
}
return 1;
}
static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
unsigned long haddr)
{
VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
count_vm_event(THP_SPLIT_PUD);
pudp_huge_clear_flush(vma, haddr, pud);
}
void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
unsigned long address)
{
spinlock_t *ptl;
struct mmu_notifier_range range;
mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
address & HPAGE_PUD_MASK,
(address & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE);
mmu_notifier_invalidate_range_start(&range);
ptl = pud_lock(vma->vm_mm, pud);
if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
goto out;
__split_huge_pud_locked(vma, pud, range.start);
out:
spin_unlock(ptl);
mmu_notifier_invalidate_range_end(&range);
}
#else
void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
unsigned long address)
{
}
#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
unsigned long haddr, pmd_t *pmd)
{
struct mm_struct *mm = vma->vm_mm;
pgtable_t pgtable;
pmd_t _pmd, old_pmd;
unsigned long addr;
pte_t *pte;
int i;
/*
* Leave pmd empty until pte is filled note that it is fine to delay
* notification until mmu_notifier_invalidate_range_end() as we are
* replacing a zero pmd write protected page with a zero pte write
* protected page.
*
* See Documentation/mm/mmu_notifier.rst
*/
old_pmd = pmdp_huge_clear_flush(vma, haddr, pmd);
pgtable = pgtable_trans_huge_withdraw(mm, pmd);
pmd_populate(mm, &_pmd, pgtable);
pte = pte_offset_map(&_pmd, haddr);
VM_BUG_ON(!pte);
for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
pte_t entry;
entry = pfn_pte(my_zero_pfn(addr), vma->vm_page_prot);
entry = pte_mkspecial(entry);
if (pmd_uffd_wp(old_pmd))
entry = pte_mkuffd_wp(entry);
VM_BUG_ON(!pte_none(ptep_get(pte)));
set_pte_at(mm, addr, pte, entry);
pte++;
}
pte_unmap(pte - 1);
smp_wmb(); /* make pte visible before pmd */
pmd_populate(mm, pmd, pgtable);
}
static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long haddr, bool freeze)
{
struct mm_struct *mm = vma->vm_mm;
struct folio *folio;
struct page *page;
pgtable_t pgtable;
pmd_t old_pmd, _pmd;
bool young, write, soft_dirty, pmd_migration = false, uffd_wp = false;
bool anon_exclusive = false, dirty = false;
unsigned long addr;
pte_t *pte;
int i;
VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
&& !pmd_devmap(*pmd));
count_vm_event(THP_SPLIT_PMD);
if (!vma_is_anonymous(vma)) {
old_pmd = pmdp_huge_clear_flush(vma, haddr, pmd);
/*
* We are going to unmap this huge page. So
* just go ahead and zap it
*/
if (arch_needs_pgtable_deposit())
zap_deposited_table(mm, pmd);
if (vma_is_special_huge(vma))
return;
if (unlikely(is_pmd_migration_entry(old_pmd))) {
swp_entry_t entry;
entry = pmd_to_swp_entry(old_pmd);
folio = pfn_swap_entry_folio(entry);
} else {
page = pmd_page(old_pmd);
folio = page_folio(page);
if (!folio_test_dirty(folio) && pmd_dirty(old_pmd))
folio_mark_dirty(folio);
if (!folio_test_referenced(folio) && pmd_young(old_pmd))
folio_set_referenced(folio);
folio_remove_rmap_pmd(folio, page, vma);
folio_put(folio);
}
add_mm_counter(mm, mm_counter_file(folio), -HPAGE_PMD_NR);
return;
}
if (is_huge_zero_pmd(*pmd)) {
/*
* FIXME: Do we want to invalidate secondary mmu by calling
* mmu_notifier_arch_invalidate_secondary_tlbs() see comments below
* inside __split_huge_pmd() ?
*
* We are going from a zero huge page write protected to zero
* small page also write protected so it does not seems useful
* to invalidate secondary mmu at this time.
*/
return __split_huge_zero_page_pmd(vma, haddr, pmd);
}
pmd_migration = is_pmd_migration_entry(*pmd);
if (unlikely(pmd_migration)) {
swp_entry_t entry;
old_pmd = *pmd;
entry = pmd_to_swp_entry(old_pmd);
page = pfn_swap_entry_to_page(entry);
write = is_writable_migration_entry(entry);
if (PageAnon(page))
anon_exclusive = is_readable_exclusive_migration_entry(entry);
young = is_migration_entry_young(entry);
dirty = is_migration_entry_dirty(entry);
soft_dirty = pmd_swp_soft_dirty(old_pmd);
uffd_wp = pmd_swp_uffd_wp(old_pmd);
} else {
/*
* Up to this point the pmd is present and huge and userland has
* the whole access to the hugepage during the split (which
* happens in place). If we overwrite the pmd with the not-huge
* version pointing to the pte here (which of course we could if
* all CPUs were bug free), userland could trigger a small page
* size TLB miss on the small sized TLB while the hugepage TLB
* entry is still established in the huge TLB. Some CPU doesn't
* like that. See
* http://support.amd.com/TechDocs/41322_10h_Rev_Gd.pdf, Erratum
* 383 on page 105. Intel should be safe but is also warns that
* it's only safe if the permission and cache attributes of the
* two entries loaded in the two TLB is identical (which should
* be the case here). But it is generally safer to never allow
* small and huge TLB entries for the same virtual address to be
* loaded simultaneously. So instead of doing "pmd_populate();
* flush_pmd_tlb_range();" we first mark the current pmd
* notpresent (atomically because here the pmd_trans_huge must
* remain set at all times on the pmd until the split is
* complete for this pmd), then we flush the SMP TLB and finally
* we write the non-huge version of the pmd entry with
* pmd_populate.
*/
old_pmd = pmdp_invalidate(vma, haddr, pmd);
page = pmd_page(old_pmd);
folio = page_folio(page);
if (pmd_dirty(old_pmd)) {
dirty = true;
folio_set_dirty(folio);
}
write = pmd_write(old_pmd);
young = pmd_young(old_pmd);
soft_dirty = pmd_soft_dirty(old_pmd);
uffd_wp = pmd_uffd_wp(old_pmd);
VM_WARN_ON_FOLIO(!folio_ref_count(folio), folio);
VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);
/*
* Without "freeze", we'll simply split the PMD, propagating the
* PageAnonExclusive() flag for each PTE by setting it for
* each subpage -- no need to (temporarily) clear.
*
* With "freeze" we want to replace mapped pages by
* migration entries right away. This is only possible if we
* managed to clear PageAnonExclusive() -- see
* set_pmd_migration_entry().
*
* In case we cannot clear PageAnonExclusive(), split the PMD
* only and let try_to_migrate_one() fail later.
*
* See folio_try_share_anon_rmap_pmd(): invalidate PMD first.
*/
anon_exclusive = PageAnonExclusive(page);
if (freeze && anon_exclusive &&
folio_try_share_anon_rmap_pmd(folio, page))
freeze = false;
if (!freeze) {
rmap_t rmap_flags = RMAP_NONE;
folio_ref_add(folio, HPAGE_PMD_NR - 1);
if (anon_exclusive)
rmap_flags |= RMAP_EXCLUSIVE;
folio_add_anon_rmap_ptes(folio, page, HPAGE_PMD_NR,
vma, haddr, rmap_flags);
}
}
/*
* Withdraw the table only after we mark the pmd entry invalid.
* This's critical for some architectures (Power).
*/
pgtable = pgtable_trans_huge_withdraw(mm, pmd);
pmd_populate(mm, &_pmd, pgtable);
pte = pte_offset_map(&_pmd, haddr);
VM_BUG_ON(!pte);
/*
* Note that NUMA hinting access restrictions are not transferred to
* avoid any possibility of altering permissions across VMAs.
*/
if (freeze || pmd_migration) {
for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
pte_t entry;
swp_entry_t swp_entry;
if (write)
swp_entry = make_writable_migration_entry(
page_to_pfn(page + i));
else if (anon_exclusive)
swp_entry = make_readable_exclusive_migration_entry(
page_to_pfn(page + i));
else
swp_entry = make_readable_migration_entry(
page_to_pfn(page + i));
if (young)
swp_entry = make_migration_entry_young(swp_entry);
if (dirty)
swp_entry = make_migration_entry_dirty(swp_entry);
entry = swp_entry_to_pte(swp_entry);
if (soft_dirty)
entry = pte_swp_mksoft_dirty(entry);
if (uffd_wp)
entry = pte_swp_mkuffd_wp(entry);
VM_WARN_ON(!pte_none(ptep_get(pte + i)));
set_pte_at(mm, addr, pte + i, entry);
}
} else {
pte_t entry;
entry = mk_pte(page, READ_ONCE(vma->vm_page_prot));
if (write)
entry = pte_mkwrite(entry, vma);
if (!young)
entry = pte_mkold(entry);
/* NOTE: this may set soft-dirty too on some archs */
if (dirty)
entry = pte_mkdirty(entry);
if (soft_dirty)
entry = pte_mksoft_dirty(entry);
if (uffd_wp)
entry = pte_mkuffd_wp(entry);
for (i = 0; i < HPAGE_PMD_NR; i++)
VM_WARN_ON(!pte_none(ptep_get(pte + i)));
set_ptes(mm, haddr, pte, entry, HPAGE_PMD_NR);
}
pte_unmap(pte);
if (!pmd_migration)
folio_remove_rmap_pmd(folio, page, vma);
if (freeze)
put_page(page);
smp_wmb(); /* make pte visible before pmd */
pmd_populate(mm, pmd, pgtable);
}
void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long address,
pmd_t *pmd, bool freeze, struct folio *folio)
{
VM_WARN_ON_ONCE(folio && !folio_test_pmd_mappable(folio));
VM_WARN_ON_ONCE(!IS_ALIGNED(address, HPAGE_PMD_SIZE));
VM_WARN_ON_ONCE(folio && !folio_test_locked(folio));
VM_BUG_ON(freeze && !folio);
/*
* When the caller requests to set up a migration entry, we
* require a folio to check the PMD against. Otherwise, there
* is a risk of replacing the wrong folio.
*/
if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) ||
is_pmd_migration_entry(*pmd)) {
if (folio && folio != pmd_folio(*pmd))
return;
__split_huge_pmd_locked(vma, pmd, address, freeze);
}
}
void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long address, bool freeze, struct folio *folio)
{
spinlock_t *ptl;
struct mmu_notifier_range range;
mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
address & HPAGE_PMD_MASK,
(address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE);
mmu_notifier_invalidate_range_start(&range);
ptl = pmd_lock(vma->vm_mm, pmd);
split_huge_pmd_locked(vma, range.start, pmd, freeze, folio);
spin_unlock(ptl);
mmu_notifier_invalidate_range_end(&range);
}
void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
bool freeze, struct folio *folio)
{
pmd_t *pmd = mm_find_pmd(vma->vm_mm, address);
if (!pmd)
return;
__split_huge_pmd(vma, pmd, address, freeze, folio);
}
static inline void split_huge_pmd_if_needed(struct vm_area_struct *vma, unsigned long address)
{
/*
* If the new address isn't hpage aligned and it could previously
* contain an hugepage: check if we need to split an huge pmd.
*/
if (!IS_ALIGNED(address, HPAGE_PMD_SIZE) &&
range_in_vma(vma, ALIGN_DOWN(address, HPAGE_PMD_SIZE),
ALIGN(address, HPAGE_PMD_SIZE)))
split_huge_pmd_address(vma, address, false, NULL);
}
void vma_adjust_trans_huge(struct vm_area_struct *vma,
unsigned long start,
unsigned long end,
long adjust_next)
{
/* Check if we need to split start first. */
split_huge_pmd_if_needed(vma, start);
/* Check if we need to split end next. */
split_huge_pmd_if_needed(vma, end);
/*
* If we're also updating the next vma vm_start,
* check if we need to split it.
*/
if (adjust_next > 0) {
struct vm_area_struct *next = find_vma(vma->vm_mm, vma->vm_end);
unsigned long nstart = next->vm_start;
nstart += adjust_next;
split_huge_pmd_if_needed(next, nstart);
}
}
static void unmap_folio(struct folio *folio)
{
enum ttu_flags ttu_flags = TTU_RMAP_LOCKED | TTU_SYNC |
TTU_BATCH_FLUSH;
VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
if (folio_test_pmd_mappable(folio))
ttu_flags |= TTU_SPLIT_HUGE_PMD;
/*
* Anon pages need migration entries to preserve them, but file
* pages can simply be left unmapped, then faulted back on demand.
* If that is ever changed (perhaps for mlock), update remap_page().
*/
if (folio_test_anon(folio))
try_to_migrate(folio, ttu_flags);
else
try_to_unmap(folio, ttu_flags | TTU_IGNORE_MLOCK);
try_to_unmap_flush();
}
static bool __discard_anon_folio_pmd_locked(struct vm_area_struct *vma,
unsigned long addr, pmd_t *pmdp,
struct folio *folio)
{
struct mm_struct *mm = vma->vm_mm;
int ref_count, map_count;
pmd_t orig_pmd = *pmdp;
if (folio_test_dirty(folio) || pmd_dirty(orig_pmd))
return false;
orig_pmd = pmdp_huge_clear_flush(vma, addr, pmdp);
/*
* Syncing against concurrent GUP-fast:
* - clear PMD; barrier; read refcount
* - inc refcount; barrier; read PMD
*/
smp_mb();
ref_count = folio_ref_count(folio);
map_count = folio_mapcount(folio);
/*
* Order reads for folio refcount and dirty flag
* (see comments in __remove_mapping()).
*/
smp_rmb();
/*
* If the folio or its PMD is redirtied at this point, or if there
* are unexpected references, we will give up to discard this folio
* and remap it.
*
* The only folio refs must be one from isolation plus the rmap(s).
*/
if (folio_test_dirty(folio) || pmd_dirty(orig_pmd) ||
ref_count != map_count + 1) {
set_pmd_at(mm, addr, pmdp, orig_pmd);
return false;
}
folio_remove_rmap_pmd(folio, pmd_page(orig_pmd), vma);
zap_deposited_table(mm, pmdp);
add_mm_counter(mm, MM_ANONPAGES, -HPAGE_PMD_NR);
if (vma->vm_flags & VM_LOCKED)
mlock_drain_local();
folio_put(folio);
return true;
}
bool unmap_huge_pmd_locked(struct vm_area_struct *vma, unsigned long addr,
pmd_t *pmdp, struct folio *folio)
{
VM_WARN_ON_FOLIO(!folio_test_pmd_mappable(folio), folio);
VM_WARN_ON_FOLIO(!folio_test_locked(folio), folio);
VM_WARN_ON_ONCE(!IS_ALIGNED(addr, HPAGE_PMD_SIZE));
if (folio_test_anon(folio) && !folio_test_swapbacked(folio))
return __discard_anon_folio_pmd_locked(vma, addr, pmdp, folio);
return false;
}
static void remap_page(struct folio *folio, unsigned long nr, int flags)
{
int i = 0;
/* If unmap_folio() uses try_to_migrate() on file, remove this check */
if (!folio_test_anon(folio))
return;
for (;;) {
remove_migration_ptes(folio, folio, RMP_LOCKED | flags);
i += folio_nr_pages(folio);
if (i >= nr)
break;
folio = folio_next(folio);
}
}
static void lru_add_page_tail(struct folio *folio, struct page *tail,
struct lruvec *lruvec, struct list_head *list)
{
VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
VM_BUG_ON_FOLIO(PageLRU(tail), folio);
lockdep_assert_held(&lruvec->lru_lock);
if (list) {
/* page reclaim is reclaiming a huge page */
VM_WARN_ON(folio_test_lru(folio));
get_page(tail);
list_add_tail(&tail->lru, list);
} else {
/* head is still on lru (and we have it frozen) */
VM_WARN_ON(!folio_test_lru(folio));
if (folio_test_unevictable(folio))
tail->mlock_count = 0;
else
list_add_tail(&tail->lru, &folio->lru);
SetPageLRU(tail);
}
}
static void __split_huge_page_tail(struct folio *folio, int tail,
struct lruvec *lruvec, struct list_head *list,
unsigned int new_order)
{
struct page *head = &folio->page;
struct page *page_tail = head + tail;
/*
* Careful: new_folio is not a "real" folio before we cleared PageTail.
* Don't pass it around before clear_compound_head().
*/
struct folio *new_folio = (struct folio *)page_tail;
VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
/*
* Clone page flags before unfreezing refcount.
*
* After successful get_page_unless_zero() might follow flags change,
* for example lock_page() which set PG_waiters.
*
* Note that for mapped sub-pages of an anonymous THP,
* PG_anon_exclusive has been cleared in unmap_folio() and is stored in
* the migration entry instead from where remap_page() will restore it.
* We can still have PG_anon_exclusive set on effectively unmapped and
* unreferenced sub-pages of an anonymous THP: we can simply drop
* PG_anon_exclusive (-> PG_mappedtodisk) for these here.
*/
page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
page_tail->flags |= (head->flags &
((1L << PG_referenced) |
(1L << PG_swapbacked) |
(1L << PG_swapcache) |
(1L << PG_mlocked) |
(1L << PG_uptodate) |
(1L << PG_active) |
(1L << PG_workingset) |
(1L << PG_locked) |
(1L << PG_unevictable) |
#ifdef CONFIG_ARCH_USES_PG_ARCH_2
(1L << PG_arch_2) |
#endif
#ifdef CONFIG_ARCH_USES_PG_ARCH_3
(1L << PG_arch_3) |
#endif
(1L << PG_dirty) |
LRU_GEN_MASK | LRU_REFS_MASK));
/* ->mapping in first and second tail page is replaced by other uses */
VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
page_tail);
new_folio->mapping = folio->mapping;
new_folio->index = folio->index + tail;
/*
* page->private should not be set in tail pages. Fix up and warn once
* if private is unexpectedly set.
*/
if (unlikely(page_tail->private)) {
VM_WARN_ON_ONCE_PAGE(true, page_tail);
page_tail->private = 0;
}
if (folio_test_swapcache(folio))
new_folio->swap.val = folio->swap.val + tail;
/* Page flags must be visible before we make the page non-compound. */
smp_wmb();
/*
* Clear PageTail before unfreezing page refcount.
*
* After successful get_page_unless_zero() might follow put_page()
* which needs correct compound_head().
*/
clear_compound_head(page_tail);
if (new_order) {
prep_compound_page(page_tail, new_order);
folio_set_large_rmappable(new_folio);
}
/* Finally unfreeze refcount. Additional reference from page cache. */
page_ref_unfreeze(page_tail,
1 + ((!folio_test_anon(folio) || folio_test_swapcache(folio)) ?
folio_nr_pages(new_folio) : 0));
if (folio_test_young(folio))
folio_set_young(new_folio);
if (folio_test_idle(folio))
folio_set_idle(new_folio);
folio_xchg_last_cpupid(new_folio, folio_last_cpupid(folio));
/*
* always add to the tail because some iterators expect new
* pages to show after the currently processed elements - e.g.
* migrate_pages
*/
lru_add_page_tail(folio, page_tail, lruvec, list);
}
static void __split_huge_page(struct page *page, struct list_head *list,
pgoff_t end, unsigned int new_order)
{
struct folio *folio = page_folio(page);
struct page *head = &folio->page;
struct lruvec *lruvec;
struct address_space *swap_cache = NULL;
unsigned long offset = 0;
int i, nr_dropped = 0;
unsigned int new_nr = 1 << new_order;
int order = folio_order(folio);
unsigned int nr = 1 << order;
/* complete memcg works before add pages to LRU */
split_page_memcg(head, order, new_order);
if (folio_test_anon(folio) && folio_test_swapcache(folio)) {
offset = swap_cache_index(folio->swap);
swap_cache = swap_address_space(folio->swap);
xa_lock(&swap_cache->i_pages);
}
/* lock lru list/PageCompound, ref frozen by page_ref_freeze */
lruvec = folio_lruvec_lock(folio);
ClearPageHasHWPoisoned(head);
for (i = nr - new_nr; i >= new_nr; i -= new_nr) {
struct folio *tail;
__split_huge_page_tail(folio, i, lruvec, list, new_order);
tail = page_folio(head + i);
/* Some pages can be beyond EOF: drop them from page cache */
if (tail->index >= end) {
if (shmem_mapping(folio->mapping))
nr_dropped++;
else if (folio_test_clear_dirty(tail))
folio_account_cleaned(tail,
inode_to_wb(folio->mapping->host));
__filemap_remove_folio(tail, NULL);
folio_put(tail);
} else if (!folio_test_anon(folio)) {
__xa_store(&folio->mapping->i_pages, tail->index,
tail, 0);
} else if (swap_cache) {
__xa_store(&swap_cache->i_pages, offset + i,
tail, 0);
}
}
if (!new_order)
ClearPageCompound(head);
else {
struct folio *new_folio = (struct folio *)head;
folio_set_order(new_folio, new_order);
}
unlock_page_lruvec(lruvec);
/* Caller disabled irqs, so they are still disabled here */
split_page_owner(head, order, new_order);
pgalloc_tag_split(folio, order, new_order);
/* See comment in __split_huge_page_tail() */
if (folio_test_anon(folio)) {
/* Additional pin to swap cache */
if (folio_test_swapcache(folio)) {
folio_ref_add(folio, 1 + new_nr);
xa_unlock(&swap_cache->i_pages);
} else {
folio_ref_inc(folio);
}
} else {
/* Additional pin to page cache */
folio_ref_add(folio, 1 + new_nr);
xa_unlock(&folio->mapping->i_pages);
}
local_irq_enable();
if (nr_dropped)
shmem_uncharge(folio->mapping->host, nr_dropped);
remap_page(folio, nr, PageAnon(head) ? RMP_USE_SHARED_ZEROPAGE : 0);
/*
* set page to its compound_head when split to non order-0 pages, so
* we can skip unlocking it below, since PG_locked is transferred to
* the compound_head of the page and the caller will unlock it.
*/
if (new_order)
page = compound_head(page);
for (i = 0; i < nr; i += new_nr) {
struct page *subpage = head + i;
struct folio *new_folio = page_folio(subpage);
if (subpage == page)
continue;
folio_unlock(new_folio);
/*
* Subpages may be freed if there wasn't any mapping
* like if add_to_swap() is running on a lru page that
* had its mapping zapped. And freeing these pages
* requires taking the lru_lock so we do the put_page
* of the tail pages after the split is complete.
*/
free_page_and_swap_cache(subpage);
}
}
/* Racy check whether the huge page can be split */
bool can_split_folio(struct folio *folio, int caller_pins, int *pextra_pins)
{
int extra_pins;
/* Additional pins from page cache */
if (folio_test_anon(folio))
extra_pins = folio_test_swapcache(folio) ?
folio_nr_pages(folio) : 0;
else
extra_pins = folio_nr_pages(folio);
if (pextra_pins)
*pextra_pins = extra_pins;
return folio_mapcount(folio) == folio_ref_count(folio) - extra_pins -
caller_pins;
}
/*
* This function splits a large folio into smaller folios of order @new_order.
* @page can point to any page of the large folio to split. The split operation
* does not change the position of @page.
*
* Prerequisites:
*
* 1) The caller must hold a reference on the @page's owning folio, also known
* as the large folio.
*
* 2) The large folio must be locked.
*
* 3) The folio must not be pinned. Any unexpected folio references, including
* GUP pins, will result in the folio not getting split; instead, the caller
* will receive an -EAGAIN.
*
* 4) @new_order > 1, usually. Splitting to order-1 anonymous folios is not
* supported for non-file-backed folios, because folio->_deferred_list, which
* is used by partially mapped folios, is stored in subpage 2, but an order-1
* folio only has subpages 0 and 1. File-backed order-1 folios are supported,
* since they do not use _deferred_list.
*
* After splitting, the caller's folio reference will be transferred to @page,
* resulting in a raised refcount of @page after this call. The other pages may
* be freed if they are not mapped.
*
* If @list is null, tail pages will be added to LRU list, otherwise, to @list.
*
* Pages in @new_order will inherit the mapping, flags, and so on from the
* huge page.
*
* Returns 0 if the huge page was split successfully.
*
* Returns -EAGAIN if the folio has unexpected reference (e.g., GUP) or if
* the folio was concurrently removed from the page cache.
*
* Returns -EBUSY when trying to split the huge zeropage, if the folio is
* under writeback, if fs-specific folio metadata cannot currently be
* released, or if some unexpected race happened (e.g., anon VMA disappeared,
* truncation).
*
* Callers should ensure that the order respects the address space mapping
* min-order if one is set for non-anonymous folios.
*
* Returns -EINVAL when trying to split to an order that is incompatible
* with the folio. Splitting to order 0 is compatible with all folios.
*/
int split_huge_page_to_list_to_order(struct page *page, struct list_head *list,
unsigned int new_order)
{
struct folio *folio = page_folio(page);
struct deferred_split *ds_queue = get_deferred_split_queue(folio);
/* reset xarray order to new order after split */
XA_STATE_ORDER(xas, &folio->mapping->i_pages, folio->index, new_order);
bool is_anon = folio_test_anon(folio);
struct address_space *mapping = NULL;
struct anon_vma *anon_vma = NULL;
int order = folio_order(folio);
int extra_pins, ret;
pgoff_t end;
bool is_hzp;
VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
if (new_order >= folio_order(folio))
return -EINVAL;
if (is_anon) {
/* order-1 is not supported for anonymous THP. */
if (new_order == 1) {
VM_WARN_ONCE(1, "Cannot split to order-1 folio");
return -EINVAL;
}
} else if (new_order) {
/* Split shmem folio to non-zero order not supported */
if (shmem_mapping(folio->mapping)) {
VM_WARN_ONCE(1,
"Cannot split shmem folio to non-0 order");
return -EINVAL;
}
/*
* No split if the file system does not support large folio.
* Note that we might still have THPs in such mappings due to
* CONFIG_READ_ONLY_THP_FOR_FS. But in that case, the mapping
* does not actually support large folios properly.
*/
if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) &&
!mapping_large_folio_support(folio->mapping)) {
VM_WARN_ONCE(1,
"Cannot split file folio to non-0 order");
return -EINVAL;
}
}
/* Only swapping a whole PMD-mapped folio is supported */
if (folio_test_swapcache(folio) && new_order)
return -EINVAL;
is_hzp = is_huge_zero_folio(folio);
if (is_hzp) {
pr_warn_ratelimited("Called split_huge_page for huge zero page\n");
return -EBUSY;
}
if (folio_test_writeback(folio))
return -EBUSY;
if (is_anon) {
/*
* The caller does not necessarily hold an mmap_lock that would
* prevent the anon_vma disappearing so we first we take a
* reference to it and then lock the anon_vma for write. This
* is similar to folio_lock_anon_vma_read except the write lock
* is taken to serialise against parallel split or collapse
* operations.
*/
anon_vma = folio_get_anon_vma(folio);
if (!anon_vma) {
ret = -EBUSY;
goto out;
}
end = -1;
mapping = NULL;
anon_vma_lock_write(anon_vma);
} else {
unsigned int min_order;
gfp_t gfp;
mapping = folio->mapping;
/* Truncated ? */
if (!mapping) {
ret = -EBUSY;
goto out;
}
min_order = mapping_min_folio_order(folio->mapping);
if (new_order < min_order) {
VM_WARN_ONCE(1, "Cannot split mapped folio below min-order: %u",
min_order);
ret = -EINVAL;
goto out;
}
gfp = current_gfp_context(mapping_gfp_mask(mapping) &
GFP_RECLAIM_MASK);
if (!filemap_release_folio(folio, gfp)) {
ret = -EBUSY;
goto out;
}
xas_split_alloc(&xas, folio, folio_order(folio), gfp);
if (xas_error(&xas)) {
ret = xas_error(&xas);
goto out;
}
anon_vma = NULL;
i_mmap_lock_read(mapping);
/*
*__split_huge_page() may need to trim off pages beyond EOF:
* but on 32-bit, i_size_read() takes an irq-unsafe seqlock,
* which cannot be nested inside the page tree lock. So note
* end now: i_size itself may be changed at any moment, but
* folio lock is good enough to serialize the trimming.
*/
end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
if (shmem_mapping(mapping))
end = shmem_fallocend(mapping->host, end);
}
/*
* Racy check if we can split the page, before unmap_folio() will
* split PMDs
*/
if (!can_split_folio(folio, 1, &extra_pins)) {
ret = -EAGAIN;
goto out_unlock;
}
unmap_folio(folio);
/* block interrupt reentry in xa_lock and spinlock */
local_irq_disable();
if (mapping) {
/*
* Check if the folio is present in page cache.
* We assume all tail are present too, if folio is there.
*/
xas_lock(&xas);
xas_reset(&xas);
if (xas_load(&xas) != folio)
goto fail;
}
/* Prevent deferred_split_scan() touching ->_refcount */
spin_lock(&ds_queue->split_queue_lock);
if (folio_ref_freeze(folio, 1 + extra_pins)) {
if (folio_order(folio) > 1 &&
!list_empty(&folio->_deferred_list)) {
ds_queue->split_queue_len--;
if (folio_test_partially_mapped(folio)) {
folio_clear_partially_mapped(folio);
mod_mthp_stat(folio_order(folio),
MTHP_STAT_NR_ANON_PARTIALLY_MAPPED, -1);
}
/*
* Reinitialize page_deferred_list after removing the
* page from the split_queue, otherwise a subsequent
* split will see list corruption when checking the
* page_deferred_list.
*/
list_del_init(&folio->_deferred_list);
}
spin_unlock(&ds_queue->split_queue_lock);
if (mapping) {
int nr = folio_nr_pages(folio);
xas_split(&xas, folio, folio_order(folio));
if (folio_test_pmd_mappable(folio) &&
new_order < HPAGE_PMD_ORDER) {
if (folio_test_swapbacked(folio)) {
__lruvec_stat_mod_folio(folio,
NR_SHMEM_THPS, -nr);
} else {
__lruvec_stat_mod_folio(folio,
NR_FILE_THPS, -nr);
filemap_nr_thps_dec(mapping);
}
}
}
if (is_anon) {
mod_mthp_stat(order, MTHP_STAT_NR_ANON, -1);
mod_mthp_stat(new_order, MTHP_STAT_NR_ANON, 1 << (order - new_order));
}
__split_huge_page(page, list, end, new_order);
ret = 0;
} else {
spin_unlock(&ds_queue->split_queue_lock);
fail:
if (mapping)
xas_unlock(&xas);
local_irq_enable();
remap_page(folio, folio_nr_pages(folio), 0);
ret = -EAGAIN;
}
out_unlock:
if (anon_vma) {
anon_vma_unlock_write(anon_vma);
put_anon_vma(anon_vma);
}
if (mapping)
i_mmap_unlock_read(mapping);
out:
xas_destroy(&xas);
if (order == HPAGE_PMD_ORDER)
count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
count_mthp_stat(order, !ret ? MTHP_STAT_SPLIT : MTHP_STAT_SPLIT_FAILED);
return ret;
}
int min_order_for_split(struct folio *folio)
{
if (folio_test_anon(folio))
return 0;
if (!folio->mapping) {
if (folio_test_pmd_mappable(folio))
count_vm_event(THP_SPLIT_PAGE_FAILED);
return -EBUSY;
}
return mapping_min_folio_order(folio->mapping);
}
int split_folio_to_list(struct folio *folio, struct list_head *list)
{
int ret = min_order_for_split(folio);
if (ret < 0)
return ret;
return split_huge_page_to_list_to_order(&folio->page, list, ret);
}
/*
* __folio_unqueue_deferred_split() is not to be called directly:
* the folio_unqueue_deferred_split() inline wrapper in mm/internal.h
* limits its calls to those folios which may have a _deferred_list for
* queueing THP splits, and that list is (racily observed to be) non-empty.
*
* It is unsafe to call folio_unqueue_deferred_split() until folio refcount is
* zero: because even when split_queue_lock is held, a non-empty _deferred_list
* might be in use on deferred_split_scan()'s unlocked on-stack list.
*
* If memory cgroups are enabled, split_queue_lock is in the mem_cgroup: it is
* therefore important to unqueue deferred split before changing folio memcg.
*/
bool __folio_unqueue_deferred_split(struct folio *folio)
{
struct deferred_split *ds_queue;
unsigned long flags;
bool unqueued = false;
WARN_ON_ONCE(folio_ref_count(folio));
WARN_ON_ONCE(!mem_cgroup_disabled() && !folio_memcg(folio));
ds_queue = get_deferred_split_queue(folio);
spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
if (!list_empty(&folio->_deferred_list)) {
ds_queue->split_queue_len--;
if (folio_test_partially_mapped(folio)) {
folio_clear_partially_mapped(folio);
mod_mthp_stat(folio_order(folio),
MTHP_STAT_NR_ANON_PARTIALLY_MAPPED, -1);
}
list_del_init(&folio->_deferred_list);
unqueued = true;
}
spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
return unqueued; /* useful for debug warnings */
}
/* partially_mapped=false won't clear PG_partially_mapped folio flag */
void deferred_split_folio(struct folio *folio, bool partially_mapped)
{
struct deferred_split *ds_queue = get_deferred_split_queue(folio);
#ifdef CONFIG_MEMCG
struct mem_cgroup *memcg = folio_memcg(folio);
#endif
unsigned long flags;
/*
* Order 1 folios have no space for a deferred list, but we also
* won't waste much memory by not adding them to the deferred list.
*/
if (folio_order(folio) <= 1)
return;
if (!partially_mapped && !split_underused_thp)
return;
/*
* Exclude swapcache: originally to avoid a corrupt deferred split
* queue. Nowadays that is fully prevented by mem_cgroup_swapout();
* but if page reclaim is already handling the same folio, it is
* unnecessary to handle it again in the shrinker, so excluding
* swapcache here may still be a useful optimization.
*/
if (folio_test_swapcache(folio))
return;
spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
if (partially_mapped) {
if (!folio_test_partially_mapped(folio)) {
folio_set_partially_mapped(folio);
if (folio_test_pmd_mappable(folio))
count_vm_event(THP_DEFERRED_SPLIT_PAGE);
count_mthp_stat(folio_order(folio), MTHP_STAT_SPLIT_DEFERRED);
mod_mthp_stat(folio_order(folio), MTHP_STAT_NR_ANON_PARTIALLY_MAPPED, 1);
}
} else {
/* partially mapped folios cannot become non-partially mapped */
VM_WARN_ON_FOLIO(folio_test_partially_mapped(folio), folio);
}
if (list_empty(&folio->_deferred_list)) {
list_add_tail(&folio->_deferred_list, &ds_queue->split_queue);
ds_queue->split_queue_len++;
#ifdef CONFIG_MEMCG
if (memcg)
set_shrinker_bit(memcg, folio_nid(folio),
deferred_split_shrinker->id);
#endif
}
spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
}
static unsigned long deferred_split_count(struct shrinker *shrink,
struct shrink_control *sc)
{
struct pglist_data *pgdata = NODE_DATA(sc->nid);
struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
#ifdef CONFIG_MEMCG
if (sc->memcg)
ds_queue = &sc->memcg->deferred_split_queue;
#endif
return READ_ONCE(ds_queue->split_queue_len);
}
static bool thp_underused(struct folio *folio)
{
int num_zero_pages = 0, num_filled_pages = 0;
void *kaddr;
int i;
if (khugepaged_max_ptes_none == HPAGE_PMD_NR - 1)
return false;
for (i = 0; i < folio_nr_pages(folio); i++) {
kaddr = kmap_local_folio(folio, i * PAGE_SIZE);
if (!memchr_inv(kaddr, 0, PAGE_SIZE)) {
num_zero_pages++;
if (num_zero_pages > khugepaged_max_ptes_none) {
kunmap_local(kaddr);
return true;
}
} else {
/*
* Another path for early exit once the number
* of non-zero filled pages exceeds threshold.
*/
num_filled_pages++;
if (num_filled_pages >= HPAGE_PMD_NR - khugepaged_max_ptes_none) {
kunmap_local(kaddr);
return false;
}
}
kunmap_local(kaddr);
}
return false;
}
static unsigned long deferred_split_scan(struct shrinker *shrink,
struct shrink_control *sc)
{
struct pglist_data *pgdata = NODE_DATA(sc->nid);
struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
unsigned long flags;
LIST_HEAD(list);
struct folio *folio, *next, *prev = NULL;
int split = 0, removed = 0;
#ifdef CONFIG_MEMCG
if (sc->memcg)
ds_queue = &sc->memcg->deferred_split_queue;
#endif
spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
/* Take pin on all head pages to avoid freeing them under us */
list_for_each_entry_safe(folio, next, &ds_queue->split_queue,
_deferred_list) {
if (folio_try_get(folio)) {
list_move(&folio->_deferred_list, &list);
} else {
/* We lost race with folio_put() */
if (folio_test_partially_mapped(folio)) {
folio_clear_partially_mapped(folio);
mod_mthp_stat(folio_order(folio),
MTHP_STAT_NR_ANON_PARTIALLY_MAPPED, -1);
}
list_del_init(&folio->_deferred_list);
ds_queue->split_queue_len--;
}
if (!--sc->nr_to_scan)
break;
}
spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
list_for_each_entry_safe(folio, next, &list, _deferred_list) {
bool did_split = false;
bool underused = false;
if (!folio_test_partially_mapped(folio)) {
underused = thp_underused(folio);
if (!underused)
goto next;
}
if (!folio_trylock(folio))
goto next;
if (!split_folio(folio)) {
did_split = true;
if (underused)
count_vm_event(THP_UNDERUSED_SPLIT_PAGE);
split++;
}
folio_unlock(folio);
next:
/*
* split_folio() removes folio from list on success.
* Only add back to the queue if folio is partially mapped.
* If thp_underused returns false, or if split_folio fails
* in the case it was underused, then consider it used and
* don't add it back to split_queue.
*/
if (did_split) {
; /* folio already removed from list */
} else if (!folio_test_partially_mapped(folio)) {
list_del_init(&folio->_deferred_list);
removed++;
} else {
/*
* That unlocked list_del_init() above would be unsafe,
* unless its folio is separated from any earlier folios
* left on the list (which may be concurrently unqueued)
* by one safe folio with refcount still raised.
*/
swap(folio, prev);
}
if (folio)
folio_put(folio);
}
spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
list_splice_tail(&list, &ds_queue->split_queue);
ds_queue->split_queue_len -= removed;
spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
if (prev)
folio_put(prev);
/*
* Stop shrinker if we didn't split any page, but the queue is empty.
* This can happen if pages were freed under us.
*/
if (!split && list_empty(&ds_queue->split_queue))
return SHRINK_STOP;
return split;
}
#ifdef CONFIG_DEBUG_FS
static void split_huge_pages_all(void)
{
struct zone *zone;
struct page *page;
struct folio *folio;
unsigned long pfn, max_zone_pfn;
unsigned long total = 0, split = 0;
pr_debug("Split all THPs\n");
for_each_zone(zone) {
if (!managed_zone(zone))
continue;
max_zone_pfn = zone_end_pfn(zone);
for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
int nr_pages;
page = pfn_to_online_page(pfn);
if (!page || PageTail(page))
continue;
folio = page_folio(page);
if (!folio_try_get(folio))
continue;
if (unlikely(page_folio(page) != folio))
goto next;
if (zone != folio_zone(folio))
goto next;
if (!folio_test_large(folio)
|| folio_test_hugetlb(folio)
|| !folio_test_lru(folio))
goto next;
total++;
folio_lock(folio);
nr_pages = folio_nr_pages(folio);
if (!split_folio(folio))
split++;
pfn += nr_pages - 1;
folio_unlock(folio);
next:
folio_put(folio);
cond_resched();
}
}
pr_debug("%lu of %lu THP split\n", split, total);
}
static inline bool vma_not_suitable_for_thp_split(struct vm_area_struct *vma)
{
return vma_is_special_huge(vma) || (vma->vm_flags & VM_IO) ||
is_vm_hugetlb_page(vma);
}
static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
unsigned long vaddr_end, unsigned int new_order)
{
int ret = 0;
struct task_struct *task;
struct mm_struct *mm;
unsigned long total = 0, split = 0;
unsigned long addr;
vaddr_start &= PAGE_MASK;
vaddr_end &= PAGE_MASK;
task = find_get_task_by_vpid(pid);
if (!task) {
ret = -ESRCH;
goto out;
}
/* Find the mm_struct */
mm = get_task_mm(task);
put_task_struct(task);
if (!mm) {
ret = -EINVAL;
goto out;
}
pr_debug("Split huge pages in pid: %d, vaddr: [0x%lx - 0x%lx]\n",
pid, vaddr_start, vaddr_end);
mmap_read_lock(mm);
/*
* always increase addr by PAGE_SIZE, since we could have a PTE page
* table filled with PTE-mapped THPs, each of which is distinct.
*/
for (addr = vaddr_start; addr < vaddr_end; addr += PAGE_SIZE) {
struct vm_area_struct *vma = vma_lookup(mm, addr);
struct folio_walk fw;
struct folio *folio;
struct address_space *mapping;
unsigned int target_order = new_order;
if (!vma)
break;
/* skip special VMA and hugetlb VMA */
if (vma_not_suitable_for_thp_split(vma)) {
addr = vma->vm_end;
continue;
}
folio = folio_walk_start(&fw, vma, addr, 0);
if (!folio)
continue;
if (!is_transparent_hugepage(folio))
goto next;
if (!folio_test_anon(folio)) {
mapping = folio->mapping;
target_order = max(new_order,
mapping_min_folio_order(mapping));
}
if (target_order >= folio_order(folio))
goto next;
total++;
/*
* For folios with private, split_huge_page_to_list_to_order()
* will try to drop it before split and then check if the folio
* can be split or not. So skip the check here.
*/
if (!folio_test_private(folio) &&
!can_split_folio(folio, 0, NULL))
goto next;
if (!folio_trylock(folio))
goto next;
folio_get(folio);
folio_walk_end(&fw, vma);
if (!folio_test_anon(folio) && folio->mapping != mapping)
goto unlock;
if (!split_folio_to_order(folio, target_order))
split++;
unlock:
folio_unlock(folio);
folio_put(folio);
cond_resched();
continue;
next:
folio_walk_end(&fw, vma);
cond_resched();
}
mmap_read_unlock(mm);
mmput(mm);
pr_debug("%lu of %lu THP split\n", split, total);
out:
return ret;
}
static int split_huge_pages_in_file(const char *file_path, pgoff_t off_start,
pgoff_t off_end, unsigned int new_order)
{
struct filename *file;
struct file *candidate;
struct address_space *mapping;
int ret = -EINVAL;
pgoff_t index;
int nr_pages = 1;
unsigned long total = 0, split = 0;
unsigned int min_order;
unsigned int target_order;
file = getname_kernel(file_path);
if (IS_ERR(file))
return ret;
candidate = file_open_name(file, O_RDONLY, 0);
if (IS_ERR(candidate))
goto out;
pr_debug("split file-backed THPs in file: %s, page offset: [0x%lx - 0x%lx]\n",
file_path, off_start, off_end);
mapping = candidate->f_mapping;
min_order = mapping_min_folio_order(mapping);
target_order = max(new_order, min_order);
for (index = off_start; index < off_end; index += nr_pages) {
struct folio *folio = filemap_get_folio(mapping, index);
nr_pages = 1;
if (IS_ERR(folio))
continue;
if (!folio_test_large(folio))
goto next;
total++;
nr_pages = folio_nr_pages(folio);
if (target_order >= folio_order(folio))
goto next;
if (!folio_trylock(folio))
goto next;
if (folio->mapping != mapping)
goto unlock;
if (!split_folio_to_order(folio, target_order))
split++;
unlock:
folio_unlock(folio);
next:
folio_put(folio);
cond_resched();
}
filp_close(candidate, NULL);
ret = 0;
pr_debug("%lu of %lu file-backed THP split\n", split, total);
out:
putname(file);
return ret;
}
#define MAX_INPUT_BUF_SZ 255
static ssize_t split_huge_pages_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppops)
{
static DEFINE_MUTEX(split_debug_mutex);
ssize_t ret;
/*
* hold pid, start_vaddr, end_vaddr, new_order or
* file_path, off_start, off_end, new_order
*/
char input_buf[MAX_INPUT_BUF_SZ];
int pid;
unsigned long vaddr_start, vaddr_end;
unsigned int new_order = 0;
ret = mutex_lock_interruptible(&split_debug_mutex);
if (ret)
return ret;
ret = -EFAULT;
memset(input_buf, 0, MAX_INPUT_BUF_SZ);
if (copy_from_user(input_buf, buf, min_t(size_t, count, MAX_INPUT_BUF_SZ)))
goto out;
input_buf[MAX_INPUT_BUF_SZ - 1] = '\0';
if (input_buf[0] == '/') {
char *tok;
char *buf = input_buf;
char file_path[MAX_INPUT_BUF_SZ];
pgoff_t off_start = 0, off_end = 0;
size_t input_len = strlen(input_buf);
tok = strsep(&buf, ",");
if (tok && buf) {
strscpy(file_path, tok);
} else {
ret = -EINVAL;
goto out;
}
ret = sscanf(buf, "0x%lx,0x%lx,%d", &off_start, &off_end, &new_order);
if (ret != 2 && ret != 3) {
ret = -EINVAL;
goto out;
}
ret = split_huge_pages_in_file(file_path, off_start, off_end, new_order);
if (!ret)
ret = input_len;
goto out;
}
ret = sscanf(input_buf, "%d,0x%lx,0x%lx,%d", &pid, &vaddr_start, &vaddr_end, &new_order);
if (ret == 1 && pid == 1) {
split_huge_pages_all();
ret = strlen(input_buf);
goto out;
} else if (ret != 3 && ret != 4) {
ret = -EINVAL;
goto out;
}
ret = split_huge_pages_pid(pid, vaddr_start, vaddr_end, new_order);
if (!ret)
ret = strlen(input_buf);
out:
mutex_unlock(&split_debug_mutex);
return ret;
}
static const struct file_operations split_huge_pages_fops = {
.owner = THIS_MODULE,
.write = split_huge_pages_write,
};
static int __init split_huge_pages_debugfs(void)
{
debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
&split_huge_pages_fops);
return 0;
}
late_initcall(split_huge_pages_debugfs);
#endif
#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
int set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
struct page *page)
{
struct folio *folio = page_folio(page);
struct vm_area_struct *vma = pvmw->vma;
struct mm_struct *mm = vma->vm_mm;
unsigned long address = pvmw->address;
bool anon_exclusive;
pmd_t pmdval;
swp_entry_t entry;
pmd_t pmdswp;
if (!(pvmw->pmd && !pvmw->pte))
return 0;
flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
pmdval = pmdp_invalidate(vma, address, pvmw->pmd);
/* See folio_try_share_anon_rmap_pmd(): invalidate PMD first. */
anon_exclusive = folio_test_anon(folio) && PageAnonExclusive(page);
if (anon_exclusive && folio_try_share_anon_rmap_pmd(folio, page)) {
set_pmd_at(mm, address, pvmw->pmd, pmdval);
return -EBUSY;
}
if (pmd_dirty(pmdval))
folio_mark_dirty(folio);
if (pmd_write(pmdval))
entry = make_writable_migration_entry(page_to_pfn(page));
else if (anon_exclusive)
entry = make_readable_exclusive_migration_entry(page_to_pfn(page));
else
entry = make_readable_migration_entry(page_to_pfn(page));
if (pmd_young(pmdval))
entry = make_migration_entry_young(entry);
if (pmd_dirty(pmdval))
entry = make_migration_entry_dirty(entry);
pmdswp = swp_entry_to_pmd(entry);
if (pmd_soft_dirty(pmdval))
pmdswp = pmd_swp_mksoft_dirty(pmdswp);
if (pmd_uffd_wp(pmdval))
pmdswp = pmd_swp_mkuffd_wp(pmdswp);
set_pmd_at(mm, address, pvmw->pmd, pmdswp);
folio_remove_rmap_pmd(folio, page, vma);
folio_put(folio);
trace_set_migration_pmd(address, pmd_val(pmdswp));
return 0;
}
void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
{
struct folio *folio = page_folio(new);
struct vm_area_struct *vma = pvmw->vma;
struct mm_struct *mm = vma->vm_mm;
unsigned long address = pvmw->address;
unsigned long haddr = address & HPAGE_PMD_MASK;
pmd_t pmde;
swp_entry_t entry;
if (!(pvmw->pmd && !pvmw->pte))
return;
entry = pmd_to_swp_entry(*pvmw->pmd);
folio_get(folio);
pmde = mk_huge_pmd(new, READ_ONCE(vma->vm_page_prot));
if (pmd_swp_soft_dirty(*pvmw->pmd))
pmde = pmd_mksoft_dirty(pmde);
if (is_writable_migration_entry(entry))
pmde = pmd_mkwrite(pmde, vma);
if (pmd_swp_uffd_wp(*pvmw->pmd))
pmde = pmd_mkuffd_wp(pmde);
if (!is_migration_entry_young(entry))
pmde = pmd_mkold(pmde);
/* NOTE: this may contain setting soft-dirty on some archs */
if (folio_test_dirty(folio) && is_migration_entry_dirty(entry))
pmde = pmd_mkdirty(pmde);
if (folio_test_anon(folio)) {
rmap_t rmap_flags = RMAP_NONE;
if (!is_readable_migration_entry(entry))
rmap_flags |= RMAP_EXCLUSIVE;
folio_add_anon_rmap_pmd(folio, new, vma, haddr, rmap_flags);
} else {
folio_add_file_rmap_pmd(folio, new, vma);
}
VM_BUG_ON(pmd_write(pmde) && folio_test_anon(folio) && !PageAnonExclusive(new));
set_pmd_at(mm, haddr, pvmw->pmd, pmde);
/* No need to invalidate - it was non-present before */
update_mmu_cache_pmd(vma, address, pvmw->pmd);
trace_remove_migration_pmd(address, pmd_val(pmde));
}
#endif
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