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linux/mm/huge_memory.c
David Hildenbrand 1462c52e9f mm/huge_memory: conditionally call maybe_mkwrite() and drop pte_wrprotect() in __split_huge_pmd_locked() 
No need to call maybe_mkwrite() to then wrprotect if the source PMD was not
writable.

It's worth nothing that this now allows for PTEs to be writable even if
the source PMD was not writable: if vma->vm_page_prot includes write
permissions.

As documented in commit 931298e103 ("mm/userfaultfd: rely on
vma->vm_page_prot in uffd_wp_range()"), any mechanism that intends to
have pages wrprotected (COW, writenotify, mprotect, uffd-wp, softdirty,
...) has to properly adjust vma->vm_page_prot upfront, to not include
write permissions. If vma->vm_page_prot includes write permissions, the
PTE/PMD can be writable as default.

This now mimics the handling in mm/migrate.c:remove_migration_pte() and in
mm/huge_memory.c:remove_migration_pmd(), which has been in place for a
long time (except that 96a9c287e2 ("mm/migrate: fix wrongly apply write
bit after mkdirty on sparc64") temporarily changed it).

Link: https://lkml.kernel.org/r/20230411142512.438404-7-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2023-04-18 16:30:01 -07:00

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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/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 <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 atomic_t huge_zero_refcount;
struct page *huge_zero_page __read_mostly;
unsigned long huge_zero_pfn __read_mostly = ~0UL;
bool hugepage_vma_check(struct vm_area_struct *vma, unsigned long vm_flags,
bool smaps, bool in_pf, bool enforce_sysfs)
{
if (!vma->vm_mm) /* vdso */
return false;
/*
* Explicitly disabled through madvise or prctl, or some
* architectures may disable THP for some mappings, for
* example, s390 kvm.
* */
if ((vm_flags & VM_NOHUGEPAGE) ||
test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
return false;
/*
* If the hardware/firmware marked hugepage support disabled.
*/
if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_UNSUPPORTED))
return false;
/* khugepaged doesn't collapse DAX vma, but page fault is fine. */
if (vma_is_dax(vma))
return in_pf;
/*
* Special VMA and hugetlb VMA.
* Must be checked after dax since some dax mappings may have
* VM_MIXEDMAP set.
*/
if (vm_flags & VM_NO_KHUGEPAGED)
return false;
/*
* Check alignment for file vma and size for both file and anon vma.
*
* Skip the check for page fault. Huge fault does the check in fault
* handlers. And this check is not suitable for huge PUD fault.
*/
if (!in_pf &&
!transhuge_vma_suitable(vma, (vma->vm_end - HPAGE_PMD_SIZE)))
return false;
/*
* 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_is_huge(file_inode(vma->vm_file), vma->vm_pgoff,
!enforce_sysfs, vma->vm_mm, vm_flags);
/* Enforce sysfs THP requirements as necessary */
if (enforce_sysfs &&
(!hugepage_flags_enabled() || (!(vm_flags & VM_HUGEPAGE) &&
!hugepage_flags_always())))
return false;
/* Only regular file is valid */
if (!in_pf && file_thp_enabled(vma))
return true;
if (!vma_is_anonymous(vma))
return false;
if (vma_is_temporary_stack(vma))
return false;
/*
* 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);
return true;
}
static bool get_huge_zero_page(void)
{
struct page *zero_page;
retry:
if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
return true;
zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
HPAGE_PMD_ORDER);
if (!zero_page) {
count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
return false;
}
preempt_disable();
if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
preempt_enable();
__free_pages(zero_page, compound_order(zero_page));
goto retry;
}
WRITE_ONCE(huge_zero_pfn, page_to_pfn(zero_page));
/* 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 page *mm_get_huge_zero_page(struct mm_struct *mm)
{
if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
return READ_ONCE(huge_zero_page);
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_page);
}
void mm_put_huge_zero_page(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 page *zero_page = xchg(&huge_zero_page, NULL);
BUG_ON(zero_page == NULL);
WRITE_ONCE(huge_zero_pfn, ~0UL);
__free_pages(zero_page, compound_order(zero_page));
return HPAGE_PMD_NR;
}
return 0;
}
static struct shrinker huge_zero_page_shrinker = {
.count_objects = shrink_huge_zero_page_count,
.scan_objects = shrink_huge_zero_page_scan,
.seeks = DEFAULT_SEEKS,
};
#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 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
NULL,
};
static const struct attribute_group hugepage_attr_group = {
.attrs = hugepage_attr,
};
static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
{
int err;
*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;
}
return 0;
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)
{
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 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_ORDER);
/*
* we use page->mapping and page->index in second tail page
* as list_head: assuming THP order >= 2
*/
MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
err = hugepage_init_sysfs(&hugepage_kobj);
if (err)
goto err_sysfs;
err = khugepaged_init();
if (err)
goto err_slab;
err = register_shrinker(&huge_zero_page_shrinker, "thp-zero");
if (err)
goto err_hzp_shrinker;
err = register_shrinker(&deferred_split_shrinker, "thp-deferred_split");
if (err)
goto err_split_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:
unregister_shrinker(&deferred_split_shrinker);
err_split_shrinker:
unregister_shrinker(&huge_zero_page_shrinker);
err_hzp_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);
pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
{
if (likely(vma->vm_flags & VM_WRITE))
pmd = pmd_mkwrite(pmd);
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
void prep_transhuge_page(struct page *page)
{
struct folio *folio = (struct folio *)page;
VM_BUG_ON_FOLIO(folio_order(folio) < 2, folio);
INIT_LIST_HEAD(&folio->_deferred_list);
set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
}
static inline bool is_transparent_hugepage(struct page *page)
{
struct folio *folio;
if (!PageCompound(page))
return false;
folio = page_folio(page);
return is_huge_zero_page(&folio->page) ||
folio->_folio_dtor == TRANSHUGE_PAGE_DTOR;
}
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)
{
loff_t off_end = off + len;
loff_t off_align = round_up(off, size);
unsigned long len_pad, ret;
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 = current->mm->get_unmapped_area(filp, addr, len_pad,
off >> PAGE_SHIFT, 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;
ret += (off - ret) & (size - 1);
return ret;
}
unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
unsigned long len, unsigned long pgoff, unsigned long flags)
{
unsigned long ret;
loff_t off = (loff_t)pgoff << PAGE_SHIFT;
ret = __thp_get_unmapped_area(filp, addr, len, off, flags, PMD_SIZE);
if (ret)
return ret;
return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
}
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);
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;
}
clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
/*
* The memory barrier inside __folio_mark_uptodate makes sure that
* clear_huge_page 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);
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);
spin_unlock(vmf->ptl);
count_vm_event(THP_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_page(pgtable_t pgtable, struct mm_struct *mm,
struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
struct page *zero_page)
{
pmd_t entry;
if (!pmd_none(*pmd))
return;
entry = mk_pmd(zero_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;
if (!transhuge_vma_suitable(vma, haddr))
return VM_FAULT_FALLBACK;
if (unlikely(anon_vma_prepare(vma)))
return VM_FAULT_OOM;
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 page *zero_page;
vm_fault_t ret;
pgtable = pte_alloc_one(vma->vm_mm);
if (unlikely(!pgtable))
return VM_FAULT_OOM;
zero_page = mm_get_huge_zero_page(vma->vm_mm);
if (unlikely(!zero_page)) {
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_page(pgtable, vma->vm_mm, vma,
haddr, vmf->pmd, zero_page);
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);
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);
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 (pud_pfn(*pud) != pfn_t_to_pfn(pfn)) {
WARN_ON_ONCE(!is_huge_zero_pud(*pud));
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);
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 */
static 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_page(page, 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;
pmd_t pmd;
pgtable_t pgtable = NULL;
int ret = -ENOMEM;
/* 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)) {
/*
* get_huge_zero_page() will never allocate a new page here,
* since we already have a zero page to copy. It just takes a
* reference.
*/
mm_get_huge_zero_page(dst_mm);
goto out_zero_page;
}
src_page = pmd_page(pmd);
VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
get_page(src_page);
if (unlikely(page_try_dup_anon_rmap(src_page, true, src_vma))) {
/* Page maybe pinned: split and retry the fault on PTEs. */
put_page(src_page);
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_mkold(pmd_wrprotect(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
static 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);
}
struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
pud_t *pud, int flags, struct dev_pagemap **pgmap)
{
unsigned long pfn = pud_pfn(*pud);
struct mm_struct *mm = vma->vm_mm;
struct page *page;
int ret;
assert_spin_locked(pud_lockptr(mm, pud));
if (flags & FOLL_WRITE && !pud_write(*pud))
return NULL;
if (pud_present(*pud) && pud_devmap(*pud))
/* pass */;
else
return NULL;
if (flags & FOLL_TOUCH)
touch_pud(vma, addr, pud, flags & FOLL_WRITE);
/*
* device mapped pages can only be returned if the
* caller will manage the page reference count.
*
* At least one of FOLL_GET | FOLL_PIN must be set, so assert that here:
*/
if (!(flags & (FOLL_GET | FOLL_PIN)))
return ERR_PTR(-EEXIST);
pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
*pgmap = get_dev_pagemap(pfn, *pgmap);
if (!*pgmap)
return ERR_PTR(-EFAULT);
page = pfn_to_page(pfn);
ret = try_grab_page(page, flags);
if (ret)
page = ERR_PTR(ret);
return page;
}
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;
/*
* When page table lock is held, the huge zero pud should not be
* under splitting since we don't split the page itself, only pud to
* a page table.
*/
if (is_huge_zero_pud(pud)) {
/* No huge zero pud yet */
}
/*
* TODO: once we support anonymous pages, use page_try_dup_anon_rmap()
* and split if duplicating fails.
*/
pudp_set_wrprotect(src_mm, addr, src_pud);
pud = pud_mkold(pud_wrprotect(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 pagevecs 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;
page_move_anon_rmap(page, vma);
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 (vma_soft_dirty_enabled(vma) && !pmd_soft_dirty(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);
}
/* FOLL_FORCE can write to even unwritable PMDs in COW mappings. */
static inline bool can_follow_write_pmd(pmd_t pmd, struct page *page,
struct vm_area_struct *vma,
unsigned int flags)
{
/* If the pmd is writable, we can write to the page. */
if (pmd_write(pmd))
return true;
/* Maybe FOLL_FORCE is set to override it? */
if (!(flags & FOLL_FORCE))
return false;
/* But FOLL_FORCE has no effect on shared mappings */
if (vma->vm_flags & (VM_MAYSHARE | VM_SHARED))
return false;
/* ... or read-only private ones */
if (!(vma->vm_flags & VM_MAYWRITE))
return false;
/* ... or already writable ones that just need to take a write fault */
if (vma->vm_flags & VM_WRITE)
return false;
/*
* See can_change_pte_writable(): we broke COW and could map the page
* writable if we have an exclusive anonymous page ...
*/
if (!page || !PageAnon(page) || !PageAnonExclusive(page))
return false;
/* ... and a write-fault isn't required for other reasons. */
if (vma_soft_dirty_enabled(vma) && !pmd_soft_dirty(pmd))
return false;
return !userfaultfd_huge_pmd_wp(vma, pmd);
}
struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
unsigned long addr,
pmd_t *pmd,
unsigned int flags)
{
struct mm_struct *mm = vma->vm_mm;
struct page *page;
int ret;
assert_spin_locked(pmd_lockptr(mm, pmd));
page = pmd_page(*pmd);
VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
if ((flags & FOLL_WRITE) &&
!can_follow_write_pmd(*pmd, page, vma, flags))
return NULL;
/* Avoid dumping huge zero page */
if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
return ERR_PTR(-EFAULT);
/* Full NUMA hinting faults to serialise migration in fault paths */
if (pmd_protnone(*pmd) && !gup_can_follow_protnone(flags))
return NULL;
if (!pmd_write(*pmd) && gup_must_unshare(vma, flags, page))
return ERR_PTR(-EMLINK);
VM_BUG_ON_PAGE((flags & FOLL_PIN) && PageAnon(page) &&
!PageAnonExclusive(page), page);
ret = try_grab_page(page, flags);
if (ret)
return ERR_PTR(ret);
if (flags & FOLL_TOUCH)
touch_pmd(vma, addr, pmd, flags & FOLL_WRITE);
page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
return page;
}
/* 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;
pmd_t oldpmd = vmf->orig_pmd;
pmd_t pmd;
struct page *page;
unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
int page_nid = NUMA_NO_NODE;
int target_nid, last_cpupid = (-1 & LAST_CPUPID_MASK);
bool migrated = false, writable = false;
int flags = 0;
vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
if (unlikely(!pmd_same(oldpmd, *vmf->pmd))) {
spin_unlock(vmf->ptl);
goto out;
}
pmd = pmd_modify(oldpmd, 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;
page = vm_normal_page_pmd(vma, haddr, pmd);
if (!page)
goto out_map;
/* See similar comment in do_numa_page for explanation */
if (!writable)
flags |= TNF_NO_GROUP;
page_nid = page_to_nid(page);
/*
* For memory tiering mode, cpupid of slow memory page is used
* to record page access time. So use default value.
*/
if (node_is_toptier(page_nid))
last_cpupid = page_cpupid_last(page);
target_nid = numa_migrate_prep(page, vma, haddr, page_nid,
&flags);
if (target_nid == NUMA_NO_NODE) {
put_page(page);
goto out_map;
}
spin_unlock(vmf->ptl);
writable = false;
migrated = migrate_misplaced_page(page, vma, target_nid);
if (migrated) {
flags |= TNF_MIGRATED;
page_nid = target_nid;
} else {
flags |= TNF_MIGRATE_FAIL;
vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
if (unlikely(!pmd_same(oldpmd, *vmf->pmd))) {
spin_unlock(vmf->ptl);
goto out;
}
goto out_map;
}
out:
if (page_nid != NUMA_NO_NODE)
task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
flags);
return 0;
out_map:
/* Restore the PMD */
pmd = pmd_modify(oldpmd, vma->vm_page_prot);
pmd = pmd_mkyoung(pmd);
if (writable)
pmd = pmd_mkwrite(pmd);
set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
spin_unlock(vmf->ptl);
goto out;
}
/*
* 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 = pfn_folio(pmd_pfn(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_mapcount(folio) != 1)
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);
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 page *page = NULL;
int flush_needed = 1;
if (pmd_present(orig_pmd)) {
page = pmd_page(orig_pmd);
page_remove_rmap(page, vma, true);
VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
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);
page = pfn_swap_entry_to_page(entry);
flush_needed = 0;
} else
WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
if (PageAnon(page)) {
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(page), -HPAGE_PMD_NR);
}
spin_unlock(ptl);
if (flush_needed)
tlb_remove_page_size(tlb, 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 release it.
*/
if (WARN_ON(!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 page *page = pfn_swap_entry_to_page(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 (PageAnon(page))
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 page *page;
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;
page = pmd_page(*pmd);
toptier = node_is_toptier(page_to_nid(page));
/*
* Skip scanning top tier node if normal numa
* balancing is disabled
*/
if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) &&
toptier)
goto unlock;
if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING &&
!toptier)
xchg_page_access_time(page, 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);
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 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;
ptl = __pud_trans_huge_lock(pud, vma);
if (!ptl)
return 0;
pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm);
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_notify(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);
/*
* No need to double call mmu_notifier->invalidate_range() callback as
* the above pudp_huge_clear_flush_notify() did already call it.
*/
mmu_notifier_invalidate_range_only_end(&range);
}
#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;
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);
for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
pte_t *pte, entry;
entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
entry = pte_mkspecial(entry);
if (pmd_uffd_wp(old_pmd))
entry = pte_mkuffd_wp(entry);
pte = pte_offset_map(&_pmd, haddr);
VM_BUG_ON(!pte_none(*pte));
set_pte_at(mm, haddr, pte, entry);
pte_unmap(pte);
}
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 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;
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_notify(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);
page = pfn_swap_entry_to_page(entry);
} else {
page = pmd_page(old_pmd);
if (!PageDirty(page) && pmd_dirty(old_pmd))
set_page_dirty(page);
if (!PageReferenced(page) && pmd_young(old_pmd))
SetPageReferenced(page);
page_remove_rmap(page, vma, true);
put_page(page);
}
add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
return;
}
if (is_huge_zero_pmd(*pmd)) {
/*
* FIXME: Do we want to invalidate secondary mmu by calling
* mmu_notifier_invalidate_range() 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);
}
/*
* 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);
pmd_migration = is_pmd_migration_entry(old_pmd);
if (unlikely(pmd_migration)) {
swp_entry_t entry;
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 {
page = pmd_page(old_pmd);
if (pmd_dirty(old_pmd)) {
dirty = true;
SetPageDirty(page);
}
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_BUG_ON_PAGE(!page_count(page), page);
/*
* 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 page_try_share_anon_rmap(): invalidate PMD first.
*/
anon_exclusive = PageAnon(page) && PageAnonExclusive(page);
if (freeze && anon_exclusive && page_try_share_anon_rmap(page))
freeze = false;
if (!freeze)
page_ref_add(page, HPAGE_PMD_NR - 1);
}
/*
* 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);
for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
pte_t entry, *pte;
/*
* Note that NUMA hinting access restrictions are not
* transferred to avoid any possibility of altering
* permissions across VMAs.
*/
if (freeze || pmd_migration) {
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);
} else {
entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
if (write)
entry = maybe_mkwrite(entry, vma);
if (anon_exclusive)
SetPageAnonExclusive(page + i);
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);
page_add_anon_rmap(page + i, vma, addr, false);
}
pte = pte_offset_map(&_pmd, addr);
BUG_ON(!pte_none(*pte));
set_pte_at(mm, addr, pte, entry);
pte_unmap(pte);
}
if (!pmd_migration)
page_remove_rmap(page, vma, true);
if (freeze)
put_page(page);
smp_wmb(); /* make pte visible before pmd */
pmd_populate(mm, pmd, pgtable);
}
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);
/*
* If caller asks to setup a migration entry, we need a folio to check
* pmd against. Otherwise we can end up replacing wrong folio.
*/
VM_BUG_ON(freeze && !folio);
VM_WARN_ON_ONCE(folio && !folio_test_locked(folio));
if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) ||
is_pmd_migration_entry(*pmd)) {
/*
* It's safe to call pmd_page when folio is set because it's
* guaranteed that pmd is present.
*/
if (folio && folio != page_folio(pmd_page(*pmd)))
goto out;
__split_huge_pmd_locked(vma, pmd, range.start, freeze);
}
out:
spin_unlock(ptl);
/*
* No need to double call mmu_notifier->invalidate_range() callback.
* They are 3 cases to consider inside __split_huge_pmd_locked():
* 1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
* 2) __split_huge_zero_page_pmd() read only zero page and any write
* fault will trigger a flush_notify before pointing to a new page
* (it is fine if the secondary mmu keeps pointing to the old zero
* page in the meantime)
* 3) Split a huge pmd into pte pointing to the same page. No need
* to invalidate secondary tlb entry they are all still valid.
* any further changes to individual pte will notify. So no need
* to call mmu_notifier->invalidate_range()
*/
mmu_notifier_invalidate_range_only_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_SPLIT_HUGE_PMD |
TTU_SYNC;
VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
/*
* 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);
}
static void remap_page(struct folio *folio, unsigned long nr)
{
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, true);
i += folio_nr_pages(folio);
if (i >= nr)
break;
folio = folio_next(folio);
}
}
static void lru_add_page_tail(struct page *head, struct page *tail,
struct lruvec *lruvec, struct list_head *list)
{
VM_BUG_ON_PAGE(!PageHead(head), head);
VM_BUG_ON_PAGE(PageCompound(tail), head);
VM_BUG_ON_PAGE(PageLRU(tail), head);
lockdep_assert_held(&lruvec->lru_lock);
if (list) {
/* page reclaim is reclaiming a huge page */
VM_WARN_ON(PageLRU(head));
get_page(tail);
list_add_tail(&tail->lru, list);
} else {
/* head is still on lru (and we have it frozen) */
VM_WARN_ON(!PageLRU(head));
if (PageUnevictable(tail))
tail->mlock_count = 0;
else
list_add_tail(&tail->lru, &head->lru);
SetPageLRU(tail);
}
}
static void __split_huge_page_tail(struct page *head, int tail,
struct lruvec *lruvec, struct list_head *list)
{
struct page *page_tail = head + 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_X
(1L << PG_arch_2) |
(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 with the exception
* of swap cache pages that store the swp_entry_t in tail pages.
* Fix up and warn once if private is unexpectedly set.
*
* What of 32-bit systems, on which folio->_pincount overlays
* head[1].private? No problem: THP_SWAP is not enabled on 32-bit, and
* pincount must be 0 for folio_ref_freeze() to have succeeded.
*/
if (!folio_test_swapcache(page_folio(head))) {
VM_WARN_ON_ONCE_PAGE(page_tail->private != 0, page_tail);
page_tail->private = 0;
}
/* 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);
/* Finally unfreeze refcount. Additional reference from page cache. */
page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
PageSwapCache(head)));
if (page_is_young(head))
set_page_young(page_tail);
if (page_is_idle(head))
set_page_idle(page_tail);
page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
/*
* 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(head, page_tail, lruvec, list);
}
static void __split_huge_page(struct page *page, struct list_head *list,
pgoff_t end)
{
struct folio *folio = page_folio(page);
struct page *head = &folio->page;
struct lruvec *lruvec;
struct address_space *swap_cache = NULL;
unsigned long offset = 0;
unsigned int nr = thp_nr_pages(head);
int i;
/* complete memcg works before add pages to LRU */
split_page_memcg(head, nr);
if (PageAnon(head) && PageSwapCache(head)) {
swp_entry_t entry = { .val = page_private(head) };
offset = swp_offset(entry);
swap_cache = swap_address_space(entry);
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 - 1; i >= 1; i--) {
__split_huge_page_tail(head, i, lruvec, list);
/* 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(head->mapping))
shmem_uncharge(head->mapping->host, 1);
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(&head->mapping->i_pages, head[i].index,
head + i, 0);
} else if (swap_cache) {
__xa_store(&swap_cache->i_pages, offset + i,
head + i, 0);
}
}
ClearPageCompound(head);
unlock_page_lruvec(lruvec);
/* Caller disabled irqs, so they are still disabled here */
split_page_owner(head, nr);
/* See comment in __split_huge_page_tail() */
if (PageAnon(head)) {
/* Additional pin to swap cache */
if (PageSwapCache(head)) {
page_ref_add(head, 2);
xa_unlock(&swap_cache->i_pages);
} else {
page_ref_inc(head);
}
} else {
/* Additional pin to page cache */
page_ref_add(head, 2);
xa_unlock(&head->mapping->i_pages);
}
local_irq_enable();
remap_page(folio, nr);
if (PageSwapCache(head)) {
swp_entry_t entry = { .val = page_private(head) };
split_swap_cluster(entry);
}
for (i = 0; i < nr; i++) {
struct page *subpage = head + i;
if (subpage == page)
continue;
unlock_page(subpage);
/*
* 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 *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 - 1;
}
/*
* This function splits huge page into normal pages. @page can point to any
* subpage of huge page to split. Split doesn't change the position of @page.
*
* Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
* The huge page must be locked.
*
* If @list is null, tail pages will be added to LRU list, otherwise, to @list.
*
* Both head page and tail pages will inherit mapping, flags, and so on from
* the hugepage.
*
* GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
* they are not mapped.
*
* Returns 0 if the hugepage is split successfully.
* Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
* us.
*/
int split_huge_page_to_list(struct page *page, struct list_head *list)
{
struct folio *folio = page_folio(page);
struct deferred_split *ds_queue = get_deferred_split_queue(folio);
XA_STATE(xas, &folio->mapping->i_pages, folio->index);
struct anon_vma *anon_vma = NULL;
struct address_space *mapping = NULL;
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);
is_hzp = is_huge_zero_page(&folio->page);
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 (folio_test_anon(folio)) {
/*
* 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 {
gfp_t gfp;
mapping = folio->mapping;
/* Truncated ? */
if (!mapping) {
ret = -EBUSY;
goto out;
}
gfp = current_gfp_context(mapping_gfp_mask(mapping) &
GFP_RECLAIM_MASK);
if (folio_test_private(folio) &&
!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, &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 (!list_empty(&folio->_deferred_list)) {
ds_queue->split_queue_len--;
list_del(&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_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);
}
}
__split_huge_page(page, list, end);
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));
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);
count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
return ret;
}
void free_transhuge_page(struct page *page)
{
struct folio *folio = (struct folio *)page;
struct deferred_split *ds_queue = get_deferred_split_queue(folio);
unsigned long flags;
spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
if (!list_empty(&folio->_deferred_list)) {
ds_queue->split_queue_len--;
list_del(&folio->_deferred_list);
}
spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
free_compound_page(page);
}
void deferred_split_folio(struct folio *folio)
{
struct deferred_split *ds_queue = get_deferred_split_queue(folio);
#ifdef CONFIG_MEMCG
struct mem_cgroup *memcg = folio_memcg(folio);
#endif
unsigned long flags;
VM_BUG_ON_FOLIO(folio_order(folio) < 2, folio);
/*
* The try_to_unmap() in page reclaim path might reach here too,
* this may cause a race condition to corrupt deferred split queue.
* And, if page reclaim is already handling the same folio, it is
* unnecessary to handle it again in shrinker.
*
* Check the swapcache flag to determine if the folio is being
* handled by page reclaim since THP swap would add the folio into
* swap cache before calling try_to_unmap().
*/
if (folio_test_swapcache(folio))
return;
if (!list_empty(&folio->_deferred_list))
return;
spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
if (list_empty(&folio->_deferred_list)) {
count_vm_event(THP_DEFERRED_SPLIT_PAGE);
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 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;
int split = 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() */
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) {
if (!folio_trylock(folio))
goto next;
/* split_huge_page() removes page from list on success */
if (!split_folio(folio))
split++;
folio_unlock(folio);
next:
folio_put(folio);
}
spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
list_splice_tail(&list, &ds_queue->split_queue);
spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
/*
* 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;
}
static struct shrinker deferred_split_shrinker = {
.count_objects = deferred_split_count,
.scan_objects = deferred_split_scan,
.seeks = DEFAULT_SEEKS,
.flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE |
SHRINKER_NONSLAB,
};
#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)
{
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;
/* Find the task_struct from pid */
rcu_read_lock();
task = find_task_by_vpid(pid);
if (!task) {
rcu_read_unlock();
ret = -ESRCH;
goto out;
}
get_task_struct(task);
rcu_read_unlock();
/* 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 page *page;
if (!vma)
break;
/* skip special VMA and hugetlb VMA */
if (vma_not_suitable_for_thp_split(vma)) {
addr = vma->vm_end;
continue;
}
/* FOLL_DUMP to ignore special (like zero) pages */
page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
if (IS_ERR_OR_NULL(page))
continue;
if (!is_transparent_hugepage(page))
goto next;
total++;
if (!can_split_folio(page_folio(page), NULL))
goto next;
if (!trylock_page(page))
goto next;
if (!split_huge_page(page))
split++;
unlock_page(page);
next:
put_page(page);
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)
{
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;
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;
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 (!folio_trylock(folio))
goto next;
if (!split_folio(folio))
split++;
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 or file_path, off_start, off_end */
char input_buf[MAX_INPUT_BUF_SZ];
int pid;
unsigned long vaddr_start, vaddr_end;
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", &off_start, &off_end);
if (ret != 2) {
ret = -EINVAL;
goto out;
}
ret = split_huge_pages_in_file(file_path, off_start, off_end);
if (!ret)
ret = input_len;
goto out;
}
ret = sscanf(input_buf, "%d,0x%lx,0x%lx", &pid, &vaddr_start, &vaddr_end);
if (ret == 1 && pid == 1) {
split_huge_pages_all();
ret = strlen(input_buf);
goto out;
} else if (ret != 3) {
ret = -EINVAL;
goto out;
}
ret = split_huge_pages_pid(pid, vaddr_start, vaddr_end);
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,
.llseek = no_llseek,
};
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 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 page_try_share_anon_rmap(): invalidate PMD first. */
anon_exclusive = PageAnon(page) && PageAnonExclusive(page);
if (anon_exclusive && page_try_share_anon_rmap(page)) {
set_pmd_at(mm, address, pvmw->pmd, pmdval);
return -EBUSY;
}
if (pmd_dirty(pmdval))
set_page_dirty(page);
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);
page_remove_rmap(page, vma, true);
put_page(page);
trace_set_migration_pmd(address, pmd_val(pmdswp));
return 0;
}
void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *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);
get_page(new);
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 = maybe_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 (PageDirty(new) && is_migration_entry_dirty(entry))
pmde = pmd_mkdirty(pmde);
if (PageAnon(new)) {
rmap_t rmap_flags = RMAP_COMPOUND;
if (!is_readable_migration_entry(entry))
rmap_flags |= RMAP_EXCLUSIVE;
page_add_anon_rmap(new, vma, haddr, rmap_flags);
} else {
page_add_file_rmap(new, vma, true);
}
VM_BUG_ON(pmd_write(pmde) && PageAnon(new) && !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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