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linux-hardened/mm/huge_memory.c
Peter Xu f45ec5ff16 userfaultfd: wp: support swap and page migration 
For either swap and page migration, we all use the bit 2 of the entry to
identify whether this entry is uffd write-protected.  It plays a similar
role as the existing soft dirty bit in swap entries but only for keeping
the uffd-wp tracking for a specific PTE/PMD.

Something special here is that when we want to recover the uffd-wp bit
from a swap/migration entry to the PTE bit we'll also need to take care of
the _PAGE_RW bit and make sure it's cleared, otherwise even with the
_PAGE_UFFD_WP bit we can't trap it at all.

In change_pte_range() we do nothing for uffd if the PTE is a swap entry.
That can lead to data mismatch if the page that we are going to write
protect is swapped out when sending the UFFDIO_WRITEPROTECT.  This patch
also applies/removes the uffd-wp bit even for the swap entries.

Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Link: http://lkml.kernel.org/r/20200220163112.11409-11-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-04-07 10:43:39 -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/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/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 <asm/tlb.h>
#include <asm/pgalloc.h>
#include "internal.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;
bool transparent_hugepage_enabled(struct vm_area_struct *vma)
{
/* The addr is used to check if the vma size fits */
unsigned long addr = (vma->vm_end & HPAGE_PMD_MASK) - HPAGE_PMD_SIZE;
if (!transhuge_vma_suitable(vma, addr))
return false;
if (vma_is_anonymous(vma))
return __transparent_hugepage_enabled(vma);
if (vma_is_shmem(vma))
return shmem_huge_enabled(vma);
return false;
}
static struct page *get_huge_zero_page(void)
{
struct page *zero_page;
retry:
if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
return READ_ONCE(huge_zero_page);
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 NULL;
}
count_vm_event(THP_ZERO_PAGE_ALLOC);
preempt_disable();
if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
preempt_enable();
__free_pages(zero_page, compound_order(zero_page));
goto retry;
}
/* We take additional reference here. It will be put back by shrinker */
atomic_set(&huge_zero_refcount, 2);
preempt_enable();
return READ_ONCE(huge_zero_page);
}
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);
__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)
{
if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
return sprintf(buf, "[always] madvise never\n");
else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags))
return sprintf(buf, "always [madvise] never\n");
else
return sprintf(buf, "always madvise [never]\n");
}
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(enabled, 0644, enabled_show, enabled_store);
ssize_t single_hugepage_flag_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf,
enum transparent_hugepage_flag flag)
{
return sprintf(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)
{
if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
return sprintf(buf, "[always] defer defer+madvise madvise never\n");
if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
return sprintf(buf, "always [defer] defer+madvise madvise never\n");
if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
return sprintf(buf, "always defer [defer+madvise] madvise never\n");
if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
return sprintf(buf, "always defer defer+madvise [madvise] never\n");
return sprintf(buf, "always defer defer+madvise madvise [never]\n");
}
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(defrag, 0644, defrag_show, defrag_store);
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(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
static ssize_t hpage_pmd_size_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return sprintf(buf, "%lu\n", HPAGE_PMD_SIZE);
}
static struct kobj_attribute hpage_pmd_size_attr =
__ATTR_RO(hpage_pmd_size);
#ifdef CONFIG_DEBUG_VM
static ssize_t debug_cow_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return single_hugepage_flag_show(kobj, attr, buf,
TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
}
static ssize_t debug_cow_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_DEBUG_COW_FLAG);
}
static struct kobj_attribute debug_cow_attr =
__ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
#endif /* CONFIG_DEBUG_VM */
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
#ifdef CONFIG_DEBUG_VM
&debug_cow_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 = 0;
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);
if (err)
goto err_hzp_shrinker;
err = register_shrinker(&deferred_split_shrinker);
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 page *page)
{
struct mem_cgroup *memcg = compound_head(page)->mem_cgroup;
struct pglist_data *pgdat = NODE_DATA(page_to_nid(page));
if (memcg)
return &memcg->deferred_split_queue;
else
return &pgdat->deferred_split_queue;
}
#else
static inline struct deferred_split *get_deferred_split_queue(struct page *page)
{
struct pglist_data *pgdat = NODE_DATA(page_to_nid(page));
return &pgdat->deferred_split_queue;
}
#endif
void prep_transhuge_page(struct page *page)
{
/*
* we use page->mapping and page->indexlru in second tail page
* as list_head: assuming THP order >= 2
*/
INIT_LIST_HEAD(page_deferred_list(page));
set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
}
bool is_transparent_hugepage(struct page *page)
{
if (!PageCompound(page))
return 0;
page = compound_head(page);
return is_huge_zero_page(page) ||
page[1].compound_dtor == TRANSHUGE_PAGE_DTOR;
}
EXPORT_SYMBOL_GPL(is_transparent_hugepage);
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;
if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
goto out;
ret = __thp_get_unmapped_area(filp, addr, len, off, flags, PMD_SIZE);
if (ret)
return ret;
out:
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 mem_cgroup *memcg;
pgtable_t pgtable;
unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
vm_fault_t ret = 0;
VM_BUG_ON_PAGE(!PageCompound(page), page);
if (mem_cgroup_try_charge_delay(page, vma->vm_mm, gfp, &memcg, true)) {
put_page(page);
count_vm_event(THP_FAULT_FALLBACK);
count_vm_event(THP_FAULT_FALLBACK_CHARGE);
return VM_FAULT_FALLBACK;
}
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 __SetPageUptodate makes sure that
* clear_huge_page writes become visible before the set_pmd_at()
* write.
*/
__SetPageUptodate(page);
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)) {
vm_fault_t ret2;
spin_unlock(vmf->ptl);
mem_cgroup_cancel_charge(page, memcg, true);
put_page(page);
pte_free(vma->vm_mm, pgtable);
ret2 = handle_userfault(vmf, VM_UFFD_MISSING);
VM_BUG_ON(ret2 & VM_FAULT_FALLBACK);
return ret2;
}
entry = mk_huge_pmd(page, vma->vm_page_prot);
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
page_add_new_anon_rmap(page, vma, haddr, true);
mem_cgroup_commit_charge(page, memcg, false, true);
lru_cache_add_active_or_unevictable(page, vma);
pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
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_events(memcg, THP_FAULT_ALLOC, 1);
}
return 0;
unlock_release:
spin_unlock(vmf->ptl);
release:
if (pgtable)
pte_free(vma->vm_mm, pgtable);
mem_cgroup_cancel_charge(page, memcg, true);
put_page(page);
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
*/
static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
{
const bool vma_madvised = !!(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 bool 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 false;
entry = mk_pmd(zero_page, vma->vm_page_prot);
entry = pmd_mkhuge(entry);
if (pgtable)
pgtable_trans_huge_deposit(mm, pmd, pgtable);
set_pmd_at(mm, haddr, pmd, entry);
mm_inc_nr_ptes(mm);
return true;
}
vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
gfp_t gfp;
struct page *page;
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;
if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
return VM_FAULT_OOM;
if (!(vmf->flags & FAULT_FLAG_WRITE) &&
!mm_forbids_zeropage(vma->vm_mm) &&
transparent_hugepage_use_zero_page()) {
pgtable_t pgtable;
struct page *zero_page;
bool set;
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;
set = false;
if (pmd_none(*vmf->pmd)) {
ret = check_stable_address_space(vma->vm_mm);
if (ret) {
spin_unlock(vmf->ptl);
} else if (userfaultfd_missing(vma)) {
spin_unlock(vmf->ptl);
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);
spin_unlock(vmf->ptl);
set = true;
}
} else
spin_unlock(vmf->ptl);
if (!set)
pte_free(vma->vm_mm, pgtable);
return ret;
}
gfp = alloc_hugepage_direct_gfpmask(vma);
page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
if (unlikely(!page)) {
count_vm_event(THP_FAULT_FALLBACK);
return VM_FAULT_FALLBACK;
}
prep_transhuge_page(page);
return __do_huge_pmd_anonymous_page(vmf, 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_prot - insert a pmd size pfn
* @vmf: Structure describing the fault
* @pfn: pfn to insert
* @pgprot: page protection to use
* @write: whether it's a write fault
*
* Insert a pmd size pfn. See vmf_insert_pfn() for additional info and
* also consult the vmf_insert_mixed_prot() documentation when
* @pgprot != @vmf->vma->vm_page_prot.
*
* Return: vm_fault_t value.
*/
vm_fault_t vmf_insert_pfn_pmd_prot(struct vm_fault *vmf, pfn_t pfn,
pgprot_t pgprot, bool write)
{
unsigned long addr = vmf->address & PMD_MASK;
struct vm_area_struct *vma = vmf->vma;
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_prot);
#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, pgprot_t prot, bool write)
{
struct mm_struct *mm = vma->vm_mm;
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_prot - insert a pud size pfn
* @vmf: Structure describing the fault
* @pfn: pfn to insert
* @pgprot: page protection to use
* @write: whether it's a write fault
*
* Insert a pud size pfn. See vmf_insert_pfn() for additional info and
* also consult the vmf_insert_mixed_prot() documentation when
* @pgprot != @vmf->vma->vm_page_prot.
*
* Return: vm_fault_t value.
*/
vm_fault_t vmf_insert_pfn_pud_prot(struct vm_fault *vmf, pfn_t pfn,
pgprot_t pgprot, bool write)
{
unsigned long addr = vmf->address & PUD_MASK;
struct vm_area_struct *vma = vmf->vma;
/*
* 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, pgprot, write);
return VM_FAULT_NOPAGE;
}
EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud_prot);
#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
pmd_t *pmd, int flags)
{
pmd_t _pmd;
_pmd = pmd_mkyoung(*pmd);
if (flags & FOLL_WRITE)
_pmd = pmd_mkdirty(_pmd);
if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
pmd, _pmd, flags & FOLL_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;
assert_spin_locked(pmd_lockptr(mm, pmd));
/*
* When we COW a devmap PMD entry, we split it into PTEs, so we should
* not be in this function with `flags & FOLL_COW` set.
*/
WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
/* FOLL_GET and FOLL_PIN are mutually exclusive. */
if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
(FOLL_PIN | FOLL_GET)))
return NULL;
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);
/*
* 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);
if (!try_grab_page(page, flags))
page = ERR_PTR(-ENOMEM);
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 *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(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;
/*
* Make sure the _PAGE_UFFD_WP bit is cleared if the new VMA
* does not have the VM_UFFD_WP, which means that the uffd
* fork event is not enabled.
*/
if (!(vma->vm_flags & VM_UFFD_WP))
pmd = pmd_clear_uffd_wp(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_write_migration_entry(entry)) {
make_migration_entry_read(&entry);
pmd = swp_entry_to_pmd(entry);
if (pmd_swp_soft_dirty(*src_pmd))
pmd = pmd_swp_mksoft_dirty(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);
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)) {
struct page *zero_page;
/*
* 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.
*/
zero_page = mm_get_huge_zero_page(dst_mm);
set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
zero_page);
ret = 0;
goto out_unlock;
}
src_page = pmd_page(pmd);
VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
get_page(src_page);
page_dup_rmap(src_page, true);
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);
pmdp_set_wrprotect(src_mm, addr, src_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, int flags)
{
pud_t _pud;
_pud = pud_mkyoung(*pud);
if (flags & FOLL_WRITE)
_pud = pud_mkdirty(_pud);
if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
pud, _pud, flags & FOLL_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;
assert_spin_locked(pud_lockptr(mm, pud));
if (flags & FOLL_WRITE && !pud_write(*pud))
return NULL;
/* FOLL_GET and FOLL_PIN are mutually exclusive. */
if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
(FOLL_PIN | FOLL_GET)))
return NULL;
if (pud_present(*pud) && pud_devmap(*pud))
/* pass */;
else
return NULL;
if (flags & FOLL_TOUCH)
touch_pud(vma, addr, pud, flags);
/*
* 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);
if (!try_grab_page(page, flags))
page = ERR_PTR(-ENOMEM);
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 */
}
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)
{
pud_t entry;
unsigned long haddr;
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;
entry = pud_mkyoung(orig_pud);
if (write)
entry = pud_mkdirty(entry);
haddr = vmf->address & HPAGE_PUD_MASK;
if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
unlock:
spin_unlock(vmf->ptl);
}
#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
{
pmd_t entry;
unsigned long haddr;
bool write = vmf->flags & FAULT_FLAG_WRITE;
vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
goto unlock;
entry = pmd_mkyoung(orig_pmd);
if (write)
entry = pmd_mkdirty(entry);
haddr = vmf->address & HPAGE_PMD_MASK;
if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
unlock:
spin_unlock(vmf->ptl);
}
static vm_fault_t do_huge_pmd_wp_page_fallback(struct vm_fault *vmf,
pmd_t orig_pmd, struct page *page)
{
struct vm_area_struct *vma = vmf->vma;
unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
struct mem_cgroup *memcg;
pgtable_t pgtable;
pmd_t _pmd;
int i;
vm_fault_t ret = 0;
struct page **pages;
struct mmu_notifier_range range;
pages = kmalloc_array(HPAGE_PMD_NR, sizeof(struct page *),
GFP_KERNEL);
if (unlikely(!pages)) {
ret |= VM_FAULT_OOM;
goto out;
}
for (i = 0; i < HPAGE_PMD_NR; i++) {
pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
vmf->address, page_to_nid(page));
if (unlikely(!pages[i] ||
mem_cgroup_try_charge_delay(pages[i], vma->vm_mm,
GFP_KERNEL, &memcg, false))) {
if (pages[i])
put_page(pages[i]);
while (--i >= 0) {
memcg = (void *)page_private(pages[i]);
set_page_private(pages[i], 0);
mem_cgroup_cancel_charge(pages[i], memcg,
false);
put_page(pages[i]);
}
kfree(pages);
ret |= VM_FAULT_OOM;
goto out;
}
set_page_private(pages[i], (unsigned long)memcg);
}
for (i = 0; i < HPAGE_PMD_NR; i++) {
copy_user_highpage(pages[i], page + i,
haddr + PAGE_SIZE * i, vma);
__SetPageUptodate(pages[i]);
cond_resched();
}
mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
haddr, haddr + HPAGE_PMD_SIZE);
mmu_notifier_invalidate_range_start(&range);
vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
goto out_free_pages;
VM_BUG_ON_PAGE(!PageHead(page), page);
/*
* Leave pmd empty until pte is filled note we must notify here as
* concurrent CPU thread might write to new page before the call to
* mmu_notifier_invalidate_range_end() happens which can lead to a
* device seeing memory write in different order than CPU.
*
* See Documentation/vm/mmu_notifier.rst
*/
pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
pmd_populate(vma->vm_mm, &_pmd, pgtable);
for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
pte_t entry;
entry = mk_pte(pages[i], vma->vm_page_prot);
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
memcg = (void *)page_private(pages[i]);
set_page_private(pages[i], 0);
page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
mem_cgroup_commit_charge(pages[i], memcg, false, false);
lru_cache_add_active_or_unevictable(pages[i], vma);
vmf->pte = pte_offset_map(&_pmd, haddr);
VM_BUG_ON(!pte_none(*vmf->pte));
set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
pte_unmap(vmf->pte);
}
kfree(pages);
smp_wmb(); /* make pte visible before pmd */
pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
page_remove_rmap(page, true);
spin_unlock(vmf->ptl);
/*
* No need to double call mmu_notifier->invalidate_range() callback as
* the above pmdp_huge_clear_flush_notify() did already call it.
*/
mmu_notifier_invalidate_range_only_end(&range);
ret |= VM_FAULT_WRITE;
put_page(page);
out:
return ret;
out_free_pages:
spin_unlock(vmf->ptl);
mmu_notifier_invalidate_range_end(&range);
for (i = 0; i < HPAGE_PMD_NR; i++) {
memcg = (void *)page_private(pages[i]);
set_page_private(pages[i], 0);
mem_cgroup_cancel_charge(pages[i], memcg, false);
put_page(pages[i]);
}
kfree(pages);
goto out;
}
vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
{
struct vm_area_struct *vma = vmf->vma;
struct page *page = NULL, *new_page;
struct mem_cgroup *memcg;
unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
struct mmu_notifier_range range;
gfp_t huge_gfp; /* for allocation and charge */
vm_fault_t ret = 0;
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 alloc;
spin_lock(vmf->ptl);
if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
goto out_unlock;
page = pmd_page(orig_pmd);
VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
/*
* We can only reuse the page if nobody else maps the huge page or it's
* part.
*/
if (!trylock_page(page)) {
get_page(page);
spin_unlock(vmf->ptl);
lock_page(page);
spin_lock(vmf->ptl);
if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
unlock_page(page);
put_page(page);
goto out_unlock;
}
put_page(page);
}
if (reuse_swap_page(page, NULL)) {
pmd_t entry;
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);
ret |= VM_FAULT_WRITE;
unlock_page(page);
goto out_unlock;
}
unlock_page(page);
get_page(page);
spin_unlock(vmf->ptl);
alloc:
if (__transparent_hugepage_enabled(vma) &&
!transparent_hugepage_debug_cow()) {
huge_gfp = alloc_hugepage_direct_gfpmask(vma);
new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
} else
new_page = NULL;
if (likely(new_page)) {
prep_transhuge_page(new_page);
} else {
if (!page) {
split_huge_pmd(vma, vmf->pmd, vmf->address);
ret |= VM_FAULT_FALLBACK;
} else {
ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
if (ret & VM_FAULT_OOM) {
split_huge_pmd(vma, vmf->pmd, vmf->address);
ret |= VM_FAULT_FALLBACK;
}
put_page(page);
}
count_vm_event(THP_FAULT_FALLBACK);
goto out;
}
if (unlikely(mem_cgroup_try_charge_delay(new_page, vma->vm_mm,
huge_gfp, &memcg, true))) {
put_page(new_page);
split_huge_pmd(vma, vmf->pmd, vmf->address);
if (page)
put_page(page);
ret |= VM_FAULT_FALLBACK;
count_vm_event(THP_FAULT_FALLBACK);
count_vm_event(THP_FAULT_FALLBACK_CHARGE);
goto out;
}
count_vm_event(THP_FAULT_ALLOC);
count_memcg_events(memcg, THP_FAULT_ALLOC, 1);
if (!page)
clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR);
else
copy_user_huge_page(new_page, page, vmf->address,
vma, HPAGE_PMD_NR);
__SetPageUptodate(new_page);
mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
haddr, haddr + HPAGE_PMD_SIZE);
mmu_notifier_invalidate_range_start(&range);
spin_lock(vmf->ptl);
if (page)
put_page(page);
if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
spin_unlock(vmf->ptl);
mem_cgroup_cancel_charge(new_page, memcg, true);
put_page(new_page);
goto out_mn;
} else {
pmd_t entry;
entry = mk_huge_pmd(new_page, vma->vm_page_prot);
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
page_add_new_anon_rmap(new_page, vma, haddr, true);
mem_cgroup_commit_charge(new_page, memcg, false, true);
lru_cache_add_active_or_unevictable(new_page, vma);
set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
if (!page) {
add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
} else {
VM_BUG_ON_PAGE(!PageHead(page), page);
page_remove_rmap(page, true);
put_page(page);
}
ret |= VM_FAULT_WRITE;
}
spin_unlock(vmf->ptl);
out_mn:
/*
* No need to double call mmu_notifier->invalidate_range() callback as
* the above pmdp_huge_clear_flush_notify() did already call it.
*/
mmu_notifier_invalidate_range_only_end(&range);
out:
return ret;
out_unlock:
spin_unlock(vmf->ptl);
return ret;
}
/*
* FOLL_FORCE can write to even unwritable pmd's, but only
* after we've gone through a COW cycle and they are dirty.
*/
static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
{
return pmd_write(pmd) ||
((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(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 = NULL;
assert_spin_locked(pmd_lockptr(mm, pmd));
if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
goto out;
/* 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 ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
goto out;
page = pmd_page(*pmd);
VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
if (!try_grab_page(page, flags))
return ERR_PTR(-ENOMEM);
if (flags & FOLL_TOUCH)
touch_pmd(vma, addr, pmd, flags);
if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
/*
* We don't mlock() pte-mapped THPs. This way we can avoid
* leaking mlocked pages into non-VM_LOCKED VMAs.
*
* For anon THP:
*
* In most cases the pmd is the only mapping of the page as we
* break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
* writable private mappings in populate_vma_page_range().
*
* The only scenario when we have the page shared here is if we
* mlocking read-only mapping shared over fork(). We skip
* mlocking such pages.
*
* For file THP:
*
* We can expect PageDoubleMap() to be stable under page lock:
* for file pages we set it in page_add_file_rmap(), which
* requires page to be locked.
*/
if (PageAnon(page) && compound_mapcount(page) != 1)
goto skip_mlock;
if (PageDoubleMap(page) || !page->mapping)
goto skip_mlock;
if (!trylock_page(page))
goto skip_mlock;
lru_add_drain();
if (page->mapping && !PageDoubleMap(page))
mlock_vma_page(page);
unlock_page(page);
}
skip_mlock:
page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
out:
return page;
}
/* NUMA hinting page fault entry point for trans huge pmds */
vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
{
struct vm_area_struct *vma = vmf->vma;
struct anon_vma *anon_vma = NULL;
struct page *page;
unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
int page_nid = NUMA_NO_NODE, this_nid = numa_node_id();
int target_nid, last_cpupid = -1;
bool page_locked;
bool migrated = false;
bool was_writable;
int flags = 0;
vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
if (unlikely(!pmd_same(pmd, *vmf->pmd)))
goto out_unlock;
/*
* If there are potential migrations, wait for completion and retry
* without disrupting NUMA hinting information. Do not relock and
* check_same as the page may no longer be mapped.
*/
if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
page = pmd_page(*vmf->pmd);
if (!get_page_unless_zero(page))
goto out_unlock;
spin_unlock(vmf->ptl);
put_and_wait_on_page_locked(page);
goto out;
}
page = pmd_page(pmd);
BUG_ON(is_huge_zero_page(page));
page_nid = page_to_nid(page);
last_cpupid = page_cpupid_last(page);
count_vm_numa_event(NUMA_HINT_FAULTS);
if (page_nid == this_nid) {
count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
flags |= TNF_FAULT_LOCAL;
}
/* See similar comment in do_numa_page for explanation */
if (!pmd_savedwrite(pmd))
flags |= TNF_NO_GROUP;
/*
* Acquire the page lock to serialise THP migrations but avoid dropping
* page_table_lock if at all possible
*/
page_locked = trylock_page(page);
target_nid = mpol_misplaced(page, vma, haddr);
if (target_nid == NUMA_NO_NODE) {
/* If the page was locked, there are no parallel migrations */
if (page_locked)
goto clear_pmdnuma;
}
/* Migration could have started since the pmd_trans_migrating check */
if (!page_locked) {
page_nid = NUMA_NO_NODE;
if (!get_page_unless_zero(page))
goto out_unlock;
spin_unlock(vmf->ptl);
put_and_wait_on_page_locked(page);
goto out;
}
/*
* Page is misplaced. Page lock serialises migrations. Acquire anon_vma
* to serialises splits
*/
get_page(page);
spin_unlock(vmf->ptl);
anon_vma = page_lock_anon_vma_read(page);
/* Confirm the PMD did not change while page_table_lock was released */
spin_lock(vmf->ptl);
if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
unlock_page(page);
put_page(page);
page_nid = NUMA_NO_NODE;
goto out_unlock;
}
/* Bail if we fail to protect against THP splits for any reason */
if (unlikely(!anon_vma)) {
put_page(page);
page_nid = NUMA_NO_NODE;
goto clear_pmdnuma;
}
/*
* Since we took the NUMA fault, we must have observed the !accessible
* bit. Make sure all other CPUs agree with that, to avoid them
* modifying the page we're about to migrate.
*
* Must be done under PTL such that we'll observe the relevant
* inc_tlb_flush_pending().
*
* We are not sure a pending tlb flush here is for a huge page
* mapping or not. Hence use the tlb range variant
*/
if (mm_tlb_flush_pending(vma->vm_mm)) {
flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
/*
* change_huge_pmd() released the pmd lock before
* invalidating the secondary MMUs sharing the primary
* MMU pagetables (with ->invalidate_range()). The
* mmu_notifier_invalidate_range_end() (which
* internally calls ->invalidate_range()) in
* change_pmd_range() will run after us, so we can't
* rely on it here and we need an explicit invalidate.
*/
mmu_notifier_invalidate_range(vma->vm_mm, haddr,
haddr + HPAGE_PMD_SIZE);
}
/*
* Migrate the THP to the requested node, returns with page unlocked
* and access rights restored.
*/
spin_unlock(vmf->ptl);
migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
vmf->pmd, pmd, vmf->address, page, target_nid);
if (migrated) {
flags |= TNF_MIGRATED;
page_nid = target_nid;
} else
flags |= TNF_MIGRATE_FAIL;
goto out;
clear_pmdnuma:
BUG_ON(!PageLocked(page));
was_writable = pmd_savedwrite(pmd);
pmd = pmd_modify(pmd, vma->vm_page_prot);
pmd = pmd_mkyoung(pmd);
if (was_writable)
pmd = pmd_mkwrite(pmd);
set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
unlock_page(page);
out_unlock:
spin_unlock(vmf->ptl);
out:
if (anon_vma)
page_unlock_anon_vma_read(anon_vma);
if (page_nid != NUMA_NO_NODE)
task_numa_fault(last_cpupid, page_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 page *page;
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;
}
page = pmd_page(orig_pmd);
/*
* If other processes are mapping this page, we couldn't discard
* the page unless they all do MADV_FREE so let's skip the page.
*/
if (page_mapcount(page) != 1)
goto out;
if (!trylock_page(page))
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) {
get_page(page);
spin_unlock(ptl);
split_huge_page(page);
unlock_page(page);
put_page(page);
goto out_unlocked;
}
if (PageDirty(page))
ClearPageDirty(page);
unlock_page(page);
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);
}
mark_page_lazyfree(page);
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(tlb->mm, 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);
if (is_huge_zero_pmd(orig_pmd))
tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
} else if (is_huge_zero_pmd(orig_pmd)) {
zap_deposited_table(tlb->mm, pmd);
spin_unlock(ptl);
tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
} else {
struct page *page = NULL;
int flush_needed = 1;
if (pmd_present(orig_pmd)) {
page = pmd_page(orig_pmd);
page_remove_rmap(page, 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_to_page(swp_offset(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, unsigned long old_end,
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;
if ((old_addr & ~HPAGE_PMD_MASK) ||
(new_addr & ~HPAGE_PMD_MASK) ||
old_end - old_addr < HPAGE_PMD_SIZE)
return 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_sem 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_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 unchange and TLB flush unnecessary
* - HPAGE_PMD_NR is protections changed and TLB flush necessary
*/
int change_huge_pmd(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 entry;
bool preserve_write;
int ret;
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;
ptl = __pmd_trans_huge_lock(pmd, vma);
if (!ptl)
return 0;
preserve_write = prot_numa && pmd_write(*pmd);
ret = 1;
#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
if (is_swap_pmd(*pmd)) {
swp_entry_t entry = pmd_to_swp_entry(*pmd);
VM_BUG_ON(!is_pmd_migration_entry(*pmd));
if (is_write_migration_entry(entry)) {
pmd_t newpmd;
/*
* A protection check is difficult so
* just be safe and disable write
*/
make_migration_entry_read(&entry);
newpmd = swp_entry_to_pmd(entry);
if (pmd_swp_soft_dirty(*pmd))
newpmd = pmd_swp_mksoft_dirty(newpmd);
set_pmd_at(mm, addr, pmd, newpmd);
}
goto unlock;
}
#endif
/*
* 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 (prot_numa && is_huge_zero_pmd(*pmd))
goto unlock;
if (prot_numa && pmd_protnone(*pmd))
goto unlock;
/*
* In case prot_numa, we are under down_read(mmap_sem). It's critical
* to not clear pmd intermittently to avoid race with MADV_DONTNEED
* which is also under down_read(mmap_sem):
*
* 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() is required to make sure we don't miss
* dirty/young flags set by hardware.
*/
entry = pmdp_invalidate(vma, addr, pmd);
entry = pmd_modify(entry, newprot);
if (preserve_write)
entry = pmd_mk_savedwrite(entry);
if (uffd_wp) {
entry = pmd_wrprotect(entry);
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);
}
ret = HPAGE_PMD_NR;
set_pmd_at(mm, addr, pmd, entry);
BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
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 true if a given pud maps a thp, false otherwise.
*
* Note that if it returns true, 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;
/*
* For architectures like ppc64 we look at deposited pgtable
* when calling pudp_huge_get_and_clear. So do the
* pgtable_trans_huge_withdraw after finishing pudp related
* operations.
*/
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, 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;
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/vm/mmu_notifier.rst
*/
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);
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;
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)) {
_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;
page = pmd_page(_pmd);
if (!PageDirty(page) && pmd_dirty(_pmd))
set_page_dirty(page);
if (!PageReferenced(page) && pmd_young(_pmd))
SetPageReferenced(page);
page_remove_rmap(page, true);
put_page(page);
add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
return;
} else 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/us/Processor_TechDocs/41322.pdf, Erratum
* 383 on page 93. 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_to_page(swp_offset(entry));
write = is_write_migration_entry(entry);
young = false;
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))
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);
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;
swp_entry = make_migration_entry(page + i, write);
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));
entry = maybe_mkwrite(entry, vma);
if (!write)
entry = pte_wrprotect(entry);
if (!young)
entry = pte_mkold(entry);
if (soft_dirty)
entry = pte_mksoft_dirty(entry);
if (uffd_wp)
entry = pte_mkuffd_wp(entry);
}
pte = pte_offset_map(&_pmd, addr);
BUG_ON(!pte_none(*pte));
set_pte_at(mm, addr, pte, entry);
atomic_inc(&page[i]._mapcount);
pte_unmap(pte);
}
/*
* Set PG_double_map before dropping compound_mapcount to avoid
* false-negative page_mapped().
*/
if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
for (i = 0; i < HPAGE_PMD_NR; i++)
atomic_inc(&page[i]._mapcount);
}
if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
/* Last compound_mapcount is gone. */
__dec_node_page_state(page, NR_ANON_THPS);
if (TestClearPageDoubleMap(page)) {
/* No need in mapcount reference anymore */
for (i = 0; i < HPAGE_PMD_NR; i++)
atomic_dec(&page[i]._mapcount);
}
}
smp_wmb(); /* make pte visible before pmd */
pmd_populate(mm, pmd, pgtable);
if (freeze) {
for (i = 0; i < HPAGE_PMD_NR; i++) {
page_remove_rmap(page + i, false);
put_page(page + i);
}
}
}
void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long address, bool freeze, struct page *page)
{
spinlock_t *ptl;
struct mmu_notifier_range range;
mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, 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 entries, we need a page to check
* pmd against. Otherwise we can end up replacing wrong page.
*/
VM_BUG_ON(freeze && !page);
if (page && page != pmd_page(*pmd))
goto out;
if (pmd_trans_huge(*pmd)) {
page = pmd_page(*pmd);
if (PageMlocked(page))
clear_page_mlock(page);
} else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*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 page *page)
{
pgd_t *pgd;
p4d_t *p4d;
pud_t *pud;
pmd_t *pmd;
pgd = pgd_offset(vma->vm_mm, address);
if (!pgd_present(*pgd))
return;
p4d = p4d_offset(pgd, address);
if (!p4d_present(*p4d))
return;
pud = pud_offset(p4d, address);
if (!pud_present(*pud))
return;
pmd = pmd_offset(pud, address);
__split_huge_pmd(vma, pmd, address, freeze, page);
}
void vma_adjust_trans_huge(struct vm_area_struct *vma,
unsigned long start,
unsigned long end,
long adjust_next)
{
/*
* If the new start address isn't hpage aligned and it could
* previously contain an hugepage: check if we need to split
* an huge pmd.
*/
if (start & ~HPAGE_PMD_MASK &&
(start & HPAGE_PMD_MASK) >= vma->vm_start &&
(start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
split_huge_pmd_address(vma, start, false, NULL);
/*
* If the new end address isn't hpage aligned and it could
* previously contain an hugepage: check if we need to split
* an huge pmd.
*/
if (end & ~HPAGE_PMD_MASK &&
(end & HPAGE_PMD_MASK) >= vma->vm_start &&
(end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
split_huge_pmd_address(vma, end, false, NULL);
/*
* If we're also updating the vma->vm_next->vm_start, if the new
* vm_next->vm_start isn't page aligned and it could previously
* contain an hugepage: check if we need to split an huge pmd.
*/
if (adjust_next > 0) {
struct vm_area_struct *next = vma->vm_next;
unsigned long nstart = next->vm_start;
nstart += adjust_next << PAGE_SHIFT;
if (nstart & ~HPAGE_PMD_MASK &&
(nstart & HPAGE_PMD_MASK) >= next->vm_start &&
(nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
split_huge_pmd_address(next, nstart, false, NULL);
}
}
static void unmap_page(struct page *page)
{
enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
bool unmap_success;
VM_BUG_ON_PAGE(!PageHead(page), page);
if (PageAnon(page))
ttu_flags |= TTU_SPLIT_FREEZE;
unmap_success = try_to_unmap(page, ttu_flags);
VM_BUG_ON_PAGE(!unmap_success, page);
}
static void remap_page(struct page *page)
{
int i;
if (PageTransHuge(page)) {
remove_migration_ptes(page, page, true);
} else {
for (i = 0; i < HPAGE_PMD_NR; i++)
remove_migration_ptes(page + i, page + i, true);
}
}
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 exmaple lock_page() which set PG_waiters.
*/
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) |
(1L << PG_dirty)));
/* ->mapping in first tail page is compound_mapcount */
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 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, unsigned long flags)
{
struct page *head = compound_head(page);
pg_data_t *pgdat = page_pgdat(head);
struct lruvec *lruvec;
struct address_space *swap_cache = NULL;
unsigned long offset = 0;
int i;
lruvec = mem_cgroup_page_lruvec(head, pgdat);
/* complete memcg works before add pages to LRU */
mem_cgroup_split_huge_fixup(head);
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);
}
for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
__split_huge_page_tail(head, i, lruvec, list);
/* Some pages can be beyond i_size: drop them from page cache */
if (head[i].index >= end) {
ClearPageDirty(head + i);
__delete_from_page_cache(head + i, NULL);
if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
shmem_uncharge(head->mapping->host, 1);
put_page(head + i);
} 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);
split_page_owner(head, HPAGE_PMD_ORDER);
/* 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);
}
spin_unlock_irqrestore(&pgdat->lru_lock, flags);
remap_page(head);
for (i = 0; i < HPAGE_PMD_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.
*/
put_page(subpage);
}
}
int total_mapcount(struct page *page)
{
int i, compound, ret;
VM_BUG_ON_PAGE(PageTail(page), page);
if (likely(!PageCompound(page)))
return atomic_read(&page->_mapcount) + 1;
compound = compound_mapcount(page);
if (PageHuge(page))
return compound;
ret = compound;
for (i = 0; i < HPAGE_PMD_NR; i++)
ret += atomic_read(&page[i]._mapcount) + 1;
/* File pages has compound_mapcount included in _mapcount */
if (!PageAnon(page))
return ret - compound * HPAGE_PMD_NR;
if (PageDoubleMap(page))
ret -= HPAGE_PMD_NR;
return ret;
}
/*
* This calculates accurately how many mappings a transparent hugepage
* has (unlike page_mapcount() which isn't fully accurate). This full
* accuracy is primarily needed to know if copy-on-write faults can
* reuse the page and change the mapping to read-write instead of
* copying them. At the same time this returns the total_mapcount too.
*
* The function returns the highest mapcount any one of the subpages
* has. If the return value is one, even if different processes are
* mapping different subpages of the transparent hugepage, they can
* all reuse it, because each process is reusing a different subpage.
*
* The total_mapcount is instead counting all virtual mappings of the
* subpages. If the total_mapcount is equal to "one", it tells the
* caller all mappings belong to the same "mm" and in turn the
* anon_vma of the transparent hugepage can become the vma->anon_vma
* local one as no other process may be mapping any of the subpages.
*
* It would be more accurate to replace page_mapcount() with
* page_trans_huge_mapcount(), however we only use
* page_trans_huge_mapcount() in the copy-on-write faults where we
* need full accuracy to avoid breaking page pinning, because
* page_trans_huge_mapcount() is slower than page_mapcount().
*/
int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
{
int i, ret, _total_mapcount, mapcount;
/* hugetlbfs shouldn't call it */
VM_BUG_ON_PAGE(PageHuge(page), page);
if (likely(!PageTransCompound(page))) {
mapcount = atomic_read(&page->_mapcount) + 1;
if (total_mapcount)
*total_mapcount = mapcount;
return mapcount;
}
page = compound_head(page);
_total_mapcount = ret = 0;
for (i = 0; i < HPAGE_PMD_NR; i++) {
mapcount = atomic_read(&page[i]._mapcount) + 1;
ret = max(ret, mapcount);
_total_mapcount += mapcount;
}
if (PageDoubleMap(page)) {
ret -= 1;
_total_mapcount -= HPAGE_PMD_NR;
}
mapcount = compound_mapcount(page);
ret += mapcount;
_total_mapcount += mapcount;
if (total_mapcount)
*total_mapcount = _total_mapcount;
return ret;
}
/* Racy check whether the huge page can be split */
bool can_split_huge_page(struct page *page, int *pextra_pins)
{
int extra_pins;
/* Additional pins from page cache */
if (PageAnon(page))
extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
else
extra_pins = HPAGE_PMD_NR;
if (pextra_pins)
*pextra_pins = extra_pins;
return total_mapcount(page) == page_count(page) - 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 page *head = compound_head(page);
struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
struct deferred_split *ds_queue = get_deferred_split_queue(head);
struct anon_vma *anon_vma = NULL;
struct address_space *mapping = NULL;
int count, mapcount, extra_pins, ret;
bool mlocked;
unsigned long flags;
pgoff_t end;
VM_BUG_ON_PAGE(is_huge_zero_page(head), head);
VM_BUG_ON_PAGE(!PageLocked(head), head);
VM_BUG_ON_PAGE(!PageCompound(head), head);
if (PageWriteback(head))
return -EBUSY;
if (PageAnon(head)) {
/*
* The caller does not necessarily hold an mmap_sem 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 page_lock_anon_vma_read except the write lock
* is taken to serialise against parallel split or collapse
* operations.
*/
anon_vma = page_get_anon_vma(head);
if (!anon_vma) {
ret = -EBUSY;
goto out;
}
end = -1;
mapping = NULL;
anon_vma_lock_write(anon_vma);
} else {
mapping = head->mapping;
/* Truncated ? */
if (!mapping) {
ret = -EBUSY;
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
* head page lock is good enough to serialize the trimming.
*/
end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
}
/*
* Racy check if we can split the page, before unmap_page() will
* split PMDs
*/
if (!can_split_huge_page(head, &extra_pins)) {
ret = -EBUSY;
goto out_unlock;
}
mlocked = PageMlocked(head);
unmap_page(head);
VM_BUG_ON_PAGE(compound_mapcount(head), head);
/* Make sure the page is not on per-CPU pagevec as it takes pin */
if (mlocked)
lru_add_drain();
/* prevent PageLRU to go away from under us, and freeze lru stats */
spin_lock_irqsave(&pgdata->lru_lock, flags);
if (mapping) {
XA_STATE(xas, &mapping->i_pages, page_index(head));
/*
* Check if the head page is present in page cache.
* We assume all tail are present too, if head is there.
*/
xa_lock(&mapping->i_pages);
if (xas_load(&xas) != head)
goto fail;
}
/* Prevent deferred_split_scan() touching ->_refcount */
spin_lock(&ds_queue->split_queue_lock);
count = page_count(head);
mapcount = total_mapcount(head);
if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
if (!list_empty(page_deferred_list(head))) {
ds_queue->split_queue_len--;
list_del(page_deferred_list(head));
}
spin_unlock(&ds_queue->split_queue_lock);
if (mapping) {
if (PageSwapBacked(head))
__dec_node_page_state(head, NR_SHMEM_THPS);
else
__dec_node_page_state(head, NR_FILE_THPS);
}
__split_huge_page(page, list, end, flags);
if (PageSwapCache(head)) {
swp_entry_t entry = { .val = page_private(head) };
ret = split_swap_cluster(entry);
} else
ret = 0;
} else {
if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
pr_alert("total_mapcount: %u, page_count(): %u\n",
mapcount, count);
if (PageTail(page))
dump_page(head, NULL);
dump_page(page, "total_mapcount(head) > 0");
BUG();
}
spin_unlock(&ds_queue->split_queue_lock);
fail: if (mapping)
xa_unlock(&mapping->i_pages);
spin_unlock_irqrestore(&pgdata->lru_lock, flags);
remap_page(head);
ret = -EBUSY;
}
out_unlock:
if (anon_vma) {
anon_vma_unlock_write(anon_vma);
put_anon_vma(anon_vma);
}
if (mapping)
i_mmap_unlock_read(mapping);
out:
count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
return ret;
}
void free_transhuge_page(struct page *page)
{
struct deferred_split *ds_queue = get_deferred_split_queue(page);
unsigned long flags;
spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
if (!list_empty(page_deferred_list(page))) {
ds_queue->split_queue_len--;
list_del(page_deferred_list(page));
}
spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
free_compound_page(page);
}
void deferred_split_huge_page(struct page *page)
{
struct deferred_split *ds_queue = get_deferred_split_queue(page);
#ifdef CONFIG_MEMCG
struct mem_cgroup *memcg = compound_head(page)->mem_cgroup;
#endif
unsigned long flags;
VM_BUG_ON_PAGE(!PageTransHuge(page), page);
/*
* 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 page, it is
* unnecessary to handle it again in shrinker.
*
* Check PageSwapCache to determine if the page is being
* handled by page reclaim since THP swap would add the page into
* swap cache before calling try_to_unmap().
*/
if (PageSwapCache(page))
return;
spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
if (list_empty(page_deferred_list(page))) {
count_vm_event(THP_DEFERRED_SPLIT_PAGE);
list_add_tail(page_deferred_list(page), &ds_queue->split_queue);
ds_queue->split_queue_len++;
#ifdef CONFIG_MEMCG
if (memcg)
memcg_set_shrinker_bit(memcg, page_to_nid(page),
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), *pos, *next;
struct page *page;
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_safe(pos, next, &ds_queue->split_queue) {
page = list_entry((void *)pos, struct page, mapping);
page = compound_head(page);
if (get_page_unless_zero(page)) {
list_move(page_deferred_list(page), &list);
} else {
/* We lost race with put_compound_page() */
list_del_init(page_deferred_list(page));
ds_queue->split_queue_len--;
}
if (!--sc->nr_to_scan)
break;
}
spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
list_for_each_safe(pos, next, &list) {
page = list_entry((void *)pos, struct page, mapping);
if (!trylock_page(page))
goto next;
/* split_huge_page() removes page from list on success */
if (!split_huge_page(page))
split++;
unlock_page(page);
next:
put_page(page);
}
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 int split_huge_pages_set(void *data, u64 val)
{
struct zone *zone;
struct page *page;
unsigned long pfn, max_zone_pfn;
unsigned long total = 0, split = 0;
if (val != 1)
return -EINVAL;
for_each_populated_zone(zone) {
max_zone_pfn = zone_end_pfn(zone);
for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
if (!pfn_valid(pfn))
continue;
page = pfn_to_page(pfn);
if (!get_page_unless_zero(page))
continue;
if (zone != page_zone(page))
goto next;
if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
goto next;
total++;
lock_page(page);
if (!split_huge_page(page))
split++;
unlock_page(page);
next:
put_page(page);
}
}
pr_info("%lu of %lu THP split\n", split, total);
return 0;
}
DEFINE_DEBUGFS_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
"%llu\n");
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
void 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;
pmd_t pmdval;
swp_entry_t entry;
pmd_t pmdswp;
if (!(pvmw->pmd && !pvmw->pte))
return;
flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
pmdval = pmdp_invalidate(vma, address, pvmw->pmd);
if (pmd_dirty(pmdval))
set_page_dirty(page);
entry = make_migration_entry(page, pmd_write(pmdval));
pmdswp = swp_entry_to_pmd(entry);
if (pmd_soft_dirty(pmdval))
pmdswp = pmd_swp_mksoft_dirty(pmdswp);
set_pmd_at(mm, address, pvmw->pmd, pmdswp);
page_remove_rmap(page, true);
put_page(page);
}
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 mmun_start = 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 = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
if (pmd_swp_soft_dirty(*pvmw->pmd))
pmde = pmd_mksoft_dirty(pmde);
if (is_write_migration_entry(entry))
pmde = maybe_pmd_mkwrite(pmde, vma);
flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
if (PageAnon(new))
page_add_anon_rmap(new, vma, mmun_start, true);
else
page_add_file_rmap(new, true);
set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new))
mlock_vma_page(new);
update_mmu_cache_pmd(vma, address, pvmw->pmd);
}
#endif
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