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linux/mm/huge_memory.c
Hugh Dickins a3477c9e02 mm/thp: fix deferred split queue not partially_mapped: fix 
Though even more elusive than before, list_del corruption has still been
seen on THP's deferred split queue.

The idea in commit e66f3185fa was right, but its implementation wrong. 
The context omitted an important comment just before the critical test:
"split_folio() removes folio from list on success." In ignoring that
comment, when a THP split succeeded, the code went on to release the
preceding safe folio, preserving instead an irrelevant (formerly head)
folio: which gives no safety because it's not on the list.  Fix the logic.

Link: https://lkml.kernel.org/r/3c995a30-31ce-0998-1b9f-3a2cb9354c91@google.com
Fixes: e66f3185fa ("mm/thp: fix deferred split queue not partially_mapped")
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Usama Arif <usamaarif642@gmail.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-11-12 10:14:00 -08:00

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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/coredump.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;
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(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
&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
&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 inline int get_order_from_str(const char *size_str)
{
unsigned long size;
char *endptr;
int order;
size = memparse(size_str, &endptr);
if (!is_power_of_2(size))
goto err;
order = get_order(size);
if (BIT(order) & ~THP_ORDERS_ALL_ANON)
goto err;
return order;
err:
pr_err("invalid size %s in thp_anon boot parameter\n", size_str);
return -EINVAL;
}
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;
strcpy(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);
end = get_order_from_str(end_size);
} else {
start = end = get_order_from_str(subtoken);
}
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 vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
struct page *page, gfp_t gfp)
{
struct vm_area_struct *vma = vmf->vma;
struct folio *folio = page_folio(page);
pgtable_t pgtable;
unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
vm_fault_t ret = 0;
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(HPAGE_PMD_ORDER, MTHP_STAT_ANON_FAULT_FALLBACK);
count_mthp_stat(HPAGE_PMD_ORDER, MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE);
return VM_FAULT_FALLBACK;
}
folio_throttle_swaprate(folio, gfp);
pgtable = pte_alloc_one(vma->vm_mm);
if (unlikely(!pgtable)) {
ret = VM_FAULT_OOM;
goto release;
}
folio_zero_user(folio, vmf->address);
/*
* 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);
vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
if (unlikely(!pmd_none(*vmf->pmd))) {
goto unlock_release;
} else {
pmd_t entry;
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;
}
entry = mk_huge_pmd(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);
pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
mm_inc_nr_ptes(vma->vm_mm);
deferred_split_folio(folio, false);
spin_unlock(vmf->ptl);
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);
}
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;
gfp_t gfp;
struct folio *folio;
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;
}
gfp = vma_thp_gfp_mask(vma);
folio = vma_alloc_folio(gfp, HPAGE_PMD_ORDER, vma, haddr, true);
if (unlikely(!folio)) {
count_vm_event(THP_FAULT_FALLBACK);
count_mthp_stat(HPAGE_PMD_ORDER, MTHP_STAT_ANON_FAULT_FALLBACK);
return VM_FAULT_FALLBACK;
}
return __do_huge_pmd_anonymous_page(vmf, &folio->page, gfp);
}
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);
}
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))
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);
page_tail->mapping = head->mapping;
page_tail->index = head->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) {
__split_huge_page_tail(folio, i, lruvec, list, new_order);
/* Some pages can be beyond EOF: drop them from page cache */
if (head[i].index >= end) {
struct folio *tail = page_folio(head + i);
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 (!PageAnon(page)) {
__xa_store(&folio->mapping->i_pages, head[i].index,
head + i, 0);
} else if (swap_cache) {
__xa_store(&swap_cache->i_pages, offset + i,
head + i, 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) {
strcpy(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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