// SPDX-License-Identifier: GPL-2.0
/*
* Memory Migration functionality - linux/mm/migrate.c
*
* Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter
*
* Page migration was first developed in the context of the memory hotplug
* project. The main authors of the migration code are:
*
* IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
* Hirokazu Takahashi <taka@valinux.co.jp>
* Dave Hansen <haveblue@us.ibm.com>
* Christoph Lameter
*/
#include <linux/migrate.h>
#include <linux/export.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/pagemap.h>
#include <linux/buffer_head.h>
#include <linux/mm_inline.h>
#include <linux/nsproxy.h>
#include <linux/pagevec.h>
#include <linux/ksm.h>
#include <linux/rmap.h>
#include <linux/topology.h>
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/writeback.h>
#include <linux/mempolicy.h>
#include <linux/vmalloc.h>
#include <linux/security.h>
#include <linux/backing-dev.h>
#include <linux/compaction.h>
#include <linux/syscalls.h>
#include <linux/compat.h>
#include <linux/hugetlb.h>
#include <linux/hugetlb_cgroup.h>
#include <linux/gfp.h>
#include <linux/pfn_t.h>
#include <linux/memremap.h>
#include <linux/userfaultfd_k.h>
#include <linux/balloon_compaction.h>
#include <linux/page_idle.h>
#include <linux/page_owner.h>
#include <linux/sched/mm.h>
#include <linux/ptrace.h>
#include <linux/oom.h>
#include <linux/memory.h>
#include <linux/random.h>
#include <linux/sched/sysctl.h>
#include <linux/memory-tiers.h>
#include <asm/tlbflush.h>
#include <trace/events/migrate.h>
#include "internal.h"
int isolate_movable_page(struct page *page, isolate_mode_t mode)
{
const struct movable_operations *mops;
/*
* Avoid burning cycles with pages that are yet under __free_pages(),
* or just got freed under us.
*
* In case we 'win' a race for a movable page being freed under us and
* raise its refcount preventing __free_pages() from doing its job
* the put_page() at the end of this block will take care of
* release this page, thus avoiding a nasty leakage.
*/
if (unlikely(!get_page_unless_zero(page)))
goto out;
if (unlikely(PageSlab(page)))
goto out_putpage;
/* Pairs with smp_wmb() in slab freeing, e.g. SLUB's __free_slab() */
smp_rmb();
/*
* Check movable flag before taking the page lock because
* we use non-atomic bitops on newly allocated page flags so
* unconditionally grabbing the lock ruins page's owner side.
*/
if (unlikely(!__PageMovable(page)))
goto out_putpage;
/* Pairs with smp_wmb() in slab allocation, e.g. SLUB's alloc_slab_page() */
smp_rmb();
if (unlikely(PageSlab(page)))
goto out_putpage;
/*
* As movable pages are not isolated from LRU lists, concurrent
* compaction threads can race against page migration functions
* as well as race against the releasing a page.
*
* In order to avoid having an already isolated movable page
* being (wrongly) re-isolated while it is under migration,
* or to avoid attempting to isolate pages being released,
* lets be sure we have the page lock
* before proceeding with the movable page isolation steps.
*/
if (unlikely(!trylock_page(page)))
goto out_putpage;
if (!PageMovable(page) || PageIsolated(page))
goto out_no_isolated;
mops = page_movable_ops(page);
VM_BUG_ON_PAGE(!mops, page);
if (!mops->isolate_page(page, mode))
goto out_no_isolated;
/* Driver shouldn't use PG_isolated bit of page->flags */
WARN_ON_ONCE(PageIsolated(page));
SetPageIsolated(page);
unlock_page(page);
return 0;
out_no_isolated:
unlock_page(page);
out_putpage:
put_page(page);
out:
return -EBUSY;
}
static void putback_movable_page(struct page *page)
{
const struct movable_operations *mops = page_movable_ops(page);
mops->putback_page(page);
ClearPageIsolated(page);
}
/*
* Put previously isolated pages back onto the appropriate lists
* from where they were once taken off for compaction/migration.
*
* This function shall be used whenever the isolated pageset has been
* built from lru, balloon, hugetlbfs page. See isolate_migratepages_range()
* and isolate_hugetlb().
*/
void putback_movable_pages(struct list_head *l)
{
struct page *page;
struct page *page2;
list_for_each_entry_safe(page, page2, l, lru) {
if (unlikely(PageHuge(page))) {
folio_putback_active_hugetlb(page_folio(page));
continue;
}
list_del(&page->lru);
/*
* We isolated non-lru movable page so here we can use
* __PageMovable because LRU page's mapping cannot have
* PAGE_MAPPING_MOVABLE.
*/
if (unlikely(__PageMovable(page))) {
VM_BUG_ON_PAGE(!PageIsolated(page), page);
lock_page(page);
if (PageMovable(page))
putback_movable_page(page);
else
ClearPageIsolated(page);
unlock_page(page);
put_page(page);
} else {
mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
page_is_file_lru(page), -thp_nr_pages(page));
putback_lru_page(page);
}
}
}
/*
* Restore a potential migration pte to a working pte entry
*/
static bool remove_migration_pte(struct folio *folio,
struct vm_area_struct *vma, unsigned long addr, void *old)
{
DEFINE_FOLIO_VMA_WALK(pvmw, old, vma, addr, PVMW_SYNC | PVMW_MIGRATION);
while (page_vma_mapped_walk(&pvmw)) {
rmap_t rmap_flags = RMAP_NONE;
pte_t pte;
swp_entry_t entry;
struct page *new;
unsigned long idx = 0;
/* pgoff is invalid for ksm pages, but they are never large */
if (folio_test_large(folio) && !folio_test_hugetlb(folio))
idx = linear_page_index(vma, pvmw.address) - pvmw.pgoff;
new = folio_page(folio, idx);
#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
/* PMD-mapped THP migration entry */
if (!pvmw.pte) {
VM_BUG_ON_FOLIO(folio_test_hugetlb(folio) ||
!folio_test_pmd_mappable(folio), folio);
remove_migration_pmd(&pvmw, new);
continue;
}
#endif
folio_get(folio);
pte = mk_pte(new, READ_ONCE(vma->vm_page_prot));
if (pte_swp_soft_dirty(*pvmw.pte))
pte = pte_mksoft_dirty(pte);
/*
* Recheck VMA as permissions can change since migration started
*/
entry = pte_to_swp_entry(*pvmw.pte);
if (!is_migration_entry_young(entry))
pte = pte_mkold(pte);
if (folio_test_dirty(folio) && is_migration_entry_dirty(entry))
pte = pte_mkdirty(pte);
if (is_writable_migration_entry(entry))
pte = maybe_mkwrite(pte, vma);
else if (pte_swp_uffd_wp(*pvmw.pte))
pte = pte_mkuffd_wp(pte);
if (folio_test_anon(folio) && !is_readable_migration_entry(entry))
rmap_flags |= RMAP_EXCLUSIVE;
if (unlikely(is_device_private_page(new))) {
if (pte_write(pte))
entry = make_writable_device_private_entry(
page_to_pfn(new));
else
entry = make_readable_device_private_entry(
page_to_pfn(new));
pte = swp_entry_to_pte(entry);
if (pte_swp_soft_dirty(*pvmw.pte))
pte = pte_swp_mksoft_dirty(pte);
if (pte_swp_uffd_wp(*pvmw.pte))
pte = pte_swp_mkuffd_wp(pte);
}
#ifdef CONFIG_HUGETLB_PAGE
if (folio_test_hugetlb(folio)) {
unsigned int shift = huge_page_shift(hstate_vma(vma));
pte = pte_mkhuge(pte);
pte = arch_make_huge_pte(pte, shift, vma->vm_flags);
if (folio_test_anon(folio))
hugepage_add_anon_rmap(new, vma, pvmw.address,
rmap_flags);
else
page_dup_file_rmap(new, true);
set_huge_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
} else
#endif
{
if (folio_test_anon(folio))
page_add_anon_rmap(new, vma, pvmw.address,
rmap_flags);
else
page_add_file_rmap(new, vma, false);
set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
}
if (vma->vm_flags & VM_LOCKED)
mlock_drain_local();
trace_remove_migration_pte(pvmw.address, pte_val(pte),
compound_order(new));
/* No need to invalidate - it was non-present before */
update_mmu_cache(vma, pvmw.address, pvmw.pte);
}
return true;
}
/*
* Get rid of all migration entries and replace them by
* references to the indicated page.
*/
void remove_migration_ptes(struct folio *src, struct folio *dst, bool locked)
{
struct rmap_walk_control rwc = {
.rmap_one = remove_migration_pte,
.arg = src,
};
if (locked)
rmap_walk_locked(dst, &rwc);
else
rmap_walk(dst, &rwc);
}
/*
* Something used the pte of a page under migration. We need to
* get to the page and wait until migration is finished.
* When we return from this function the fault will be retried.
*/
void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
spinlock_t *ptl)
{
pte_t pte;
swp_entry_t entry;
spin_lock(ptl);
pte = *ptep;
if (!is_swap_pte(pte))
goto out;
entry = pte_to_swp_entry(pte);
if (!is_migration_entry(entry))
goto out;
migration_entry_wait_on_locked(entry, ptep, ptl);
return;
out:
pte_unmap_unlock(ptep, ptl);
}
void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
unsigned long address)
{
spinlock_t *ptl = pte_lockptr(mm, pmd);
pte_t *ptep = pte_offset_map(pmd, address);
__migration_entry_wait(mm, ptep, ptl);
}
#ifdef CONFIG_HUGETLB_PAGE
/*
* The vma read lock must be held upon entry. Holding that lock prevents either
* the pte or the ptl from being freed.
*
* This function will release the vma lock before returning.
*/
void __migration_entry_wait_huge(struct vm_area_struct *vma,
pte_t *ptep, spinlock_t *ptl)
{
pte_t pte;
hugetlb_vma_assert_locked(vma);
spin_lock(ptl);
pte = huge_ptep_get(ptep);
if (unlikely(!is_hugetlb_entry_migration(pte))) {
spin_unlock(ptl);
hugetlb_vma_unlock_read(vma);
} else {
/*
* If migration entry existed, safe to release vma lock
* here because the pgtable page won't be freed without the
* pgtable lock released. See comment right above pgtable
* lock release in migration_entry_wait_on_locked().
*/
hugetlb_vma_unlock_read(vma);
migration_entry_wait_on_locked(pte_to_swp_entry(pte), NULL, ptl);
}
}
void migration_entry_wait_huge(struct vm_area_struct *vma, pte_t *pte)
{
spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), vma->vm_mm, pte);
__migration_entry_wait_huge(vma, pte, ptl);
}
#endif
#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
{
spinlock_t *ptl;
ptl = pmd_lock(mm, pmd);
if (!is_pmd_migration_entry(*pmd))
goto unlock;
migration_entry_wait_on_locked(pmd_to_swp_entry(*pmd), NULL, ptl);
return;
unlock:
spin_unlock(ptl);
}
#endif
static int folio_expected_refs(struct address_space *mapping,
struct folio *folio)
{
int refs = 1;
if (!mapping)
return refs;
refs += folio_nr_pages(folio);
if (folio_test_private(folio))
refs++;
return refs;
}
/*
* Replace the page in the mapping.
*
* The number of remaining references must be:
* 1 for anonymous pages without a mapping
* 2 for pages with a mapping
* 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
*/
int folio_migrate_mapping(struct address_space *mapping,
struct folio *newfolio, struct folio *folio, int extra_count)
{
XA_STATE(xas, &mapping->i_pages, folio_index(folio));
struct zone *oldzone, *newzone;
int dirty;
int expected_count = folio_expected_refs(mapping, folio) + extra_count;
long nr = folio_nr_pages(folio);
if (!mapping) {
/* Anonymous page without mapping */
if (folio_ref_count(folio) != expected_count)
return -EAGAIN;
/* No turning back from here */
newfolio->index = folio->index;
newfolio->mapping = folio->mapping;
if (folio_test_swapbacked(folio))
__folio_set_swapbacked(newfolio);
return MIGRATEPAGE_SUCCESS;
}
oldzone = folio_zone(folio);
newzone = folio_zone(newfolio);
xas_lock_irq(&xas);
if (!folio_ref_freeze(folio, expected_count)) {
xas_unlock_irq(&xas);
return -EAGAIN;
}
/*
* Now we know that no one else is looking at the folio:
* no turning back from here.
*/
newfolio->index = folio->index;
newfolio->mapping = folio->mapping;
folio_ref_add(newfolio, nr); /* add cache reference */
if (folio_test_swapbacked(folio)) {
__folio_set_swapbacked(newfolio);
if (folio_test_swapcache(folio)) {
folio_set_swapcache(newfolio);
newfolio->private = folio_get_private(folio);
}
} else {
VM_BUG_ON_FOLIO(folio_test_swapcache(folio), folio);
}
/* Move dirty while page refs frozen and newpage not yet exposed */
dirty = folio_test_dirty(folio);
if (dirty) {
folio_clear_dirty(folio);
folio_set_dirty(newfolio);
}
xas_store(&xas, newfolio);
/*
* Drop cache reference from old page by unfreezing
* to one less reference.
* We know this isn't the last reference.
*/
folio_ref_unfreeze(folio, expected_count - nr);
xas_unlock(&xas);
/* Leave irq disabled to prevent preemption while updating stats */
/*
* If moved to a different zone then also account
* the page for that zone. Other VM counters will be
* taken care of when we establish references to the
* new page and drop references to the old page.
*
* Note that anonymous pages are accounted for
* via NR_FILE_PAGES and NR_ANON_MAPPED if they
* are mapped to swap space.
*/
if (newzone != oldzone) {
struct lruvec *old_lruvec, *new_lruvec;
struct mem_cgroup *memcg;
memcg = folio_memcg(folio);
old_lruvec = mem_cgroup_lruvec(memcg, oldzone->zone_pgdat);
new_lruvec = mem_cgroup_lruvec(memcg, newzone->zone_pgdat);
__mod_lruvec_state(old_lruvec, NR_FILE_PAGES, -nr);
__mod_lruvec_state(new_lruvec, NR_FILE_PAGES, nr);
if (folio_test_swapbacked(folio) && !folio_test_swapcache(folio)) {
__mod_lruvec_state(old_lruvec, NR_SHMEM, -nr);
__mod_lruvec_state(new_lruvec, NR_SHMEM, nr);
}
#ifdef CONFIG_SWAP
if (folio_test_swapcache(folio)) {
__mod_lruvec_state(old_lruvec, NR_SWAPCACHE, -nr);
__mod_lruvec_state(new_lruvec, NR_SWAPCACHE, nr);
}
#endif
if (dirty && mapping_can_writeback(mapping)) {
__mod_lruvec_state(old_lruvec, NR_FILE_DIRTY, -nr);
__mod_zone_page_state(oldzone, NR_ZONE_WRITE_PENDING, -nr);
__mod_lruvec_state(new_lruvec, NR_FILE_DIRTY, nr);
__mod_zone_page_state(newzone, NR_ZONE_WRITE_PENDING, nr);
}
}
local_irq_enable();
return MIGRATEPAGE_SUCCESS;
}
EXPORT_SYMBOL(folio_migrate_mapping);
/*
* The expected number of remaining references is the same as that
* of folio_migrate_mapping().
*/
int migrate_huge_page_move_mapping(struct address_space *mapping,
struct folio *dst, struct folio *src)
{
XA_STATE(xas, &mapping->i_pages, folio_index(src));
int expected_count;
xas_lock_irq(&xas);
expected_count = 2 + folio_has_private(src);
if (!folio_ref_freeze(src, expected_count)) {
xas_unlock_irq(&xas);
return -EAGAIN;
}
dst->index = src->index;
dst->mapping = src->mapping;
folio_get(dst);
xas_store(&xas, dst);
folio_ref_unfreeze(src, expected_count - 1);
xas_unlock_irq(&xas);
return MIGRATEPAGE_SUCCESS;
}
/*
* Copy the flags and some other ancillary information
*/
void folio_migrate_flags(struct folio *newfolio, struct folio *folio)
{
int cpupid;
if (folio_test_error(folio))
folio_set_error(newfolio);
if (folio_test_referenced(folio))
folio_set_referenced(newfolio);
if (folio_test_uptodate(folio))
folio_mark_uptodate(newfolio);
if (folio_test_clear_active(folio)) {
VM_BUG_ON_FOLIO(folio_test_unevictable(folio), folio);
folio_set_active(newfolio);
} else if (folio_test_clear_unevictable(folio))
folio_set_unevictable(newfolio);
if (folio_test_workingset(folio))
folio_set_workingset(newfolio);
if (folio_test_checked(folio))
folio_set_checked(newfolio);
/*
* PG_anon_exclusive (-> PG_mappedtodisk) is always migrated via
* migration entries. We can still have PG_anon_exclusive set on an
* effectively unmapped and unreferenced first sub-pages of an
* anonymous THP: we can simply copy it here via PG_mappedtodisk.
*/
if (folio_test_mappedtodisk(folio))
folio_set_mappedtodisk(newfolio);
/* Move dirty on pages not done by folio_migrate_mapping() */
if (folio_test_dirty(folio))
folio_set_dirty(newfolio);
if (folio_test_young(folio))
folio_set_young(newfolio);
if (folio_test_idle(folio))
folio_set_idle(newfolio);
/*
* Copy NUMA information to the new page, to prevent over-eager
* future migrations of this same page.
*/
cpupid = page_cpupid_xchg_last(&folio->page, -1);
/*
* For memory tiering mode, when migrate between slow and fast
* memory node, reset cpupid, because that is used to record
* page access time in slow memory node.
*/
if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) {
bool f_toptier = node_is_toptier(page_to_nid(&folio->page));
bool t_toptier = node_is_toptier(page_to_nid(&newfolio->page));
if (f_toptier != t_toptier)
cpupid = -1;
}
page_cpupid_xchg_last(&newfolio->page, cpupid);
folio_migrate_ksm(newfolio, folio);
/*
* Please do not reorder this without considering how mm/ksm.c's
* get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
*/
if (folio_test_swapcache(folio))
folio_clear_swapcache(folio);
folio_clear_private(folio);
/* page->private contains hugetlb specific flags */
if (!folio_test_hugetlb(folio))
folio->private = NULL;
/*
* If any waiters have accumulated on the new page then
* wake them up.
*/
if (folio_test_writeback(newfolio))
folio_end_writeback(newfolio);
/*
* PG_readahead shares the same bit with PG_reclaim. The above
* end_page_writeback() may clear PG_readahead mistakenly, so set the
* bit after that.
*/
if (folio_test_readahead(folio))
folio_set_readahead(newfolio);
folio_copy_owner(newfolio, folio);
if (!folio_test_hugetlb(folio))
mem_cgroup_migrate(folio, newfolio);
}
EXPORT_SYMBOL(folio_migrate_flags);
void folio_migrate_copy(struct folio *newfolio, struct folio *folio)
{
folio_copy(newfolio, folio);
folio_migrate_flags(newfolio, folio);
}
EXPORT_SYMBOL(folio_migrate_copy);
/************************************************************
* Migration functions
***********************************************************/
int migrate_folio_extra(struct address_space *mapping, struct folio *dst,
struct folio *src, enum migrate_mode mode, int extra_count)
{
int rc;
BUG_ON(folio_test_writeback(src)); /* Writeback must be complete */
rc = folio_migrate_mapping(mapping, dst, src, extra_count);
if (rc != MIGRATEPAGE_SUCCESS)
return rc;
if (mode != MIGRATE_SYNC_NO_COPY)
folio_migrate_copy(dst, src);
else
folio_migrate_flags(dst, src);
return MIGRATEPAGE_SUCCESS;
}
/**
* migrate_folio() - Simple folio migration.
* @mapping: The address_space containing the folio.
* @dst: The folio to migrate the data to.
* @src: The folio containing the current data.
* @mode: How to migrate the page.
*
* Common logic to directly migrate a single LRU folio suitable for
* folios that do not use PagePrivate/PagePrivate2.
*
* Folios are locked upon entry and exit.
*/
int migrate_folio(struct address_space *mapping, struct folio *dst,
struct folio *src, enum migrate_mode mode)
{
return migrate_folio_extra(mapping, dst, src, mode, 0);
}
EXPORT_SYMBOL(migrate_folio);
#ifdef CONFIG_BLOCK
/* Returns true if all buffers are successfully locked */
static bool buffer_migrate_lock_buffers(struct buffer_head *head,
enum migrate_mode mode)
{
struct buffer_head *bh = head;
/* Simple case, sync compaction */
if (mode != MIGRATE_ASYNC) {
do {
lock_buffer(bh);
bh = bh->b_this_page;
} while (bh != head);
return true;
}
/* async case, we cannot block on lock_buffer so use trylock_buffer */
do {
if (!trylock_buffer(bh)) {
/*
* We failed to lock the buffer and cannot stall in
* async migration. Release the taken locks
*/
struct buffer_head *failed_bh = bh;
bh = head;
while (bh != failed_bh) {
unlock_buffer(bh);
bh = bh->b_this_page;
}
return false;
}
bh = bh->b_this_page;
} while (bh != head);
return true;
}
static int __buffer_migrate_folio(struct address_space *mapping,
struct folio *dst, struct folio *src, enum migrate_mode mode,
bool check_refs)
{
struct buffer_head *bh, *head;
int rc;
int expected_count;
head = folio_buffers(src);
if (!head)
return migrate_folio(mapping, dst, src, mode);
/* Check whether page does not have extra refs before we do more work */
expected_count = folio_expected_refs(mapping, src);
if (folio_ref_count(src) != expected_count)
return -EAGAIN;
if (!buffer_migrate_lock_buffers(head, mode))
return -EAGAIN;
if (check_refs) {
bool busy;
bool invalidated = false;
recheck_buffers:
busy = false;
spin_lock(&mapping->private_lock);
bh = head;
do {
if (atomic_read(&bh->b_count)) {
busy = true;
break;
}
bh = bh->b_this_page;
} while (bh != head);
if (busy) {
if (invalidated) {
rc = -EAGAIN;
goto unlock_buffers;
}
spin_unlock(&mapping->private_lock);
invalidate_bh_lrus();
invalidated = true;
goto recheck_buffers;
}
}
rc = folio_migrate_mapping(mapping, dst, src, 0);
if (rc != MIGRATEPAGE_SUCCESS)
goto unlock_buffers;
folio_attach_private(dst, folio_detach_private(src));
bh = head;
do {
set_bh_page(bh, &dst->page, bh_offset(bh));
bh = bh->b_this_page;
} while (bh != head);
if (mode != MIGRATE_SYNC_NO_COPY)
folio_migrate_copy(dst, src);
else
folio_migrate_flags(dst, src);
rc = MIGRATEPAGE_SUCCESS;
unlock_buffers:
if (check_refs)
spin_unlock(&mapping->private_lock);
bh = head;
do {
unlock_buffer(bh);
bh = bh->b_this_page;
} while (bh != head);
return rc;
}
/**
* buffer_migrate_folio() - Migration function for folios with buffers.
* @mapping: The address space containing @src.
* @dst: The folio to migrate to.
* @src: The folio to migrate from.
* @mode: How to migrate the folio.
*
* This function can only be used if the underlying filesystem guarantees
* that no other references to @src exist. For example attached buffer
* heads are accessed only under the folio lock. If your filesystem cannot
* provide this guarantee, buffer_migrate_folio_norefs() may be more
* appropriate.
*
* Return: 0 on success or a negative errno on failure.
*/
int buffer_migrate_folio(struct address_space *mapping,
struct folio *dst, struct folio *src, enum migrate_mode mode)
{
return __buffer_migrate_folio(mapping, dst, src, mode, false);
}
EXPORT_SYMBOL(buffer_migrate_folio);
/**
* buffer_migrate_folio_norefs() - Migration function for folios with buffers.
* @mapping: The address space containing @src.
* @dst: The folio to migrate to.
* @src: The folio to migrate from.
* @mode: How to migrate the folio.
*
* Like buffer_migrate_folio() except that this variant is more careful
* and checks that there are also no buffer head references. This function
* is the right one for mappings where buffer heads are directly looked
* up and referenced (such as block device mappings).
*
* Return: 0 on success or a negative errno on failure.
*/
int buffer_migrate_folio_norefs(struct address_space *mapping,
struct folio *dst, struct folio *src, enum migrate_mode mode)
{
return __buffer_migrate_folio(mapping, dst, src, mode, true);
}
EXPORT_SYMBOL_GPL(buffer_migrate_folio_norefs);
#endif
int filemap_migrate_folio(struct address_space *mapping,
struct folio *dst, struct folio *src, enum migrate_mode mode)
{
int ret;
ret = folio_migrate_mapping(mapping, dst, src, 0);
if (ret != MIGRATEPAGE_SUCCESS)
return ret;
if (folio_get_private(src))
folio_attach_private(dst, folio_detach_private(src));
if (mode != MIGRATE_SYNC_NO_COPY)
folio_migrate_copy(dst, src);
else
folio_migrate_flags(dst, src);
return MIGRATEPAGE_SUCCESS;
}
EXPORT_SYMBOL_GPL(filemap_migrate_folio);
/*
* Writeback a folio to clean the dirty state
*/
static int writeout(struct address_space *mapping, struct folio *folio)
{
struct writeback_control wbc = {
.sync_mode = WB_SYNC_NONE,
.nr_to_write = 1,
.range_start = 0,
.range_end = LLONG_MAX,
.for_reclaim = 1
};
int rc;
if (!mapping->a_ops->writepage)
/* No write method for the address space */
return -EINVAL;
if (!folio_clear_dirty_for_io(folio))
/* Someone else already triggered a write */
return -EAGAIN;
/*
* A dirty folio may imply that the underlying filesystem has
* the folio on some queue. So the folio must be clean for
* migration. Writeout may mean we lose the lock and the
* folio state is no longer what we checked for earlier.
* At this point we know that the migration attempt cannot
* be successful.
*/
remove_migration_ptes(folio, folio, false);
rc = mapping->a_ops->writepage(&folio->page, &wbc);
if (rc != AOP_WRITEPAGE_ACTIVATE)
/* unlocked. Relock */
folio_lock(folio);
return (rc < 0) ? -EIO : -EAGAIN;
}
/*
* Default handling if a filesystem does not provide a migration function.
*/
static int fallback_migrate_folio(struct address_space *mapping,
struct folio *dst, struct folio *src, enum migrate_mode mode)
{
if (folio_test_dirty(src)) {
/* Only writeback folios in full synchronous migration */
switch (mode) {
case MIGRATE_SYNC:
case MIGRATE_SYNC_NO_COPY:
break;
default:
return -EBUSY;
}
return writeout(mapping, src);
}
/*
* Buffers may be managed in a filesystem specific way.
* We must have no buffers or drop them.
*/
if (folio_test_private(src) &&
!filemap_release_folio(src, GFP_KERNEL))
return mode == MIGRATE_SYNC ? -EAGAIN : -EBUSY;
return migrate_folio(mapping, dst, src, mode);
}
/*
* Move a page to a newly allocated page
* The page is locked and all ptes have been successfully removed.
*
* The new page will have replaced the old page if this function
* is successful.
*
* Return value:
* < 0 - error code
* MIGRATEPAGE_SUCCESS - success
*/
static int move_to_new_folio(struct folio *dst, struct folio *src,
enum migrate_mode mode)
{
int rc = -EAGAIN;
bool is_lru = !__PageMovable(&src->page);
VM_BUG_ON_FOLIO(!folio_test_locked(src), src);
VM_BUG_ON_FOLIO(!folio_test_locked(dst), dst);
if (likely(is_lru)) {
struct address_space *mapping = folio_mapping(src);
if (!mapping)
rc = migrate_folio(mapping, dst, src, mode);
else if (mapping->a_ops->migrate_folio)
/*
* Most folios have a mapping and most filesystems
* provide a migrate_folio callback. Anonymous folios
* are part of swap space which also has its own
* migrate_folio callback. This is the most common path
* for page migration.
*/
rc = mapping->a_ops->migrate_folio(mapping, dst, src,
mode);
else
rc = fallback_migrate_folio(mapping, dst, src, mode);
} else {
const struct movable_operations *mops;
/*
* In case of non-lru page, it could be released after
* isolation step. In that case, we shouldn't try migration.
*/
VM_BUG_ON_FOLIO(!folio_test_isolated(src), src);
if (!folio_test_movable(src)) {
rc = MIGRATEPAGE_SUCCESS;
folio_clear_isolated(src);
goto out;
}
mops = page_movable_ops(&src->page);
rc = mops->migrate_page(&dst->page, &src->page, mode);
WARN_ON_ONCE(rc == MIGRATEPAGE_SUCCESS &&
!folio_test_isolated(src));
}
/*
* When successful, old pagecache src->mapping must be cleared before
* src is freed; but stats require that PageAnon be left as PageAnon.
*/
if (rc == MIGRATEPAGE_SUCCESS) {
if (__PageMovable(&src->page)) {
VM_BUG_ON_FOLIO(!folio_test_isolated(src), src);
/*
* We clear PG_movable under page_lock so any compactor
* cannot try to migrate this page.
*/
folio_clear_isolated(src);
}
/*
* Anonymous and movable src->mapping will be cleared by
* free_pages_prepare so don't reset it here for keeping
* the type to work PageAnon, for example.
*/
if (!folio_mapping_flags(src))
src->mapping = NULL;
if (likely(!folio_is_zone_device(dst)))
flush_dcache_folio(dst);
}
out:
return rc;
}
static int __unmap_and_move(struct folio *src, struct folio *dst,
int force, enum migrate_mode mode)
{
int rc = -EAGAIN;
bool page_was_mapped = false;
struct anon_vma *anon_vma = NULL;
bool is_lru = !__PageMovable(&src->page);
if (!folio_trylock(src)) {
if (!force || mode == MIGRATE_ASYNC)
goto out;
/*
* It's not safe for direct compaction to call lock_page.
* For example, during page readahead pages are added locked
* to the LRU. Later, when the IO completes the pages are
* marked uptodate and unlocked. However, the queueing
* could be merging multiple pages for one bio (e.g.
* mpage_readahead). If an allocation happens for the
* second or third page, the process can end up locking
* the same page twice and deadlocking. Rather than
* trying to be clever about what pages can be locked,
* avoid the use of lock_page for direct compaction
* altogether.
*/
if (current->flags & PF_MEMALLOC)
goto out;
folio_lock(src);
}
if (folio_test_writeback(src)) {
/*
* Only in the case of a full synchronous migration is it
* necessary to wait for PageWriteback. In the async case,
* the retry loop is too short and in the sync-light case,
* the overhead of stalling is too much
*/
switch (mode) {
case MIGRATE_SYNC:
case MIGRATE_SYNC_NO_COPY:
break;
default:
rc = -EBUSY;
goto out_unlock;
}
if (!force)
goto out_unlock;
folio_wait_writeback(src);
}
/*
* By try_to_migrate(), src->mapcount goes down to 0 here. In this case,
* we cannot notice that anon_vma is freed while we migrate a page.
* This get_anon_vma() delays freeing anon_vma pointer until the end
* of migration. File cache pages are no problem because of page_lock()
* File Caches may use write_page() or lock_page() in migration, then,
* just care Anon page here.
*
* Only folio_get_anon_vma() understands the subtleties of
* getting a hold on an anon_vma from outside one of its mms.
* But if we cannot get anon_vma, then we won't need it anyway,
* because that implies that the anon page is no longer mapped
* (and cannot be remapped so long as we hold the page lock).
*/
if (folio_test_anon(src) && !folio_test_ksm(src))
anon_vma = folio_get_anon_vma(src);
/*
* Block others from accessing the new page when we get around to
* establishing additional references. We are usually the only one
* holding a reference to dst at this point. We used to have a BUG
* here if folio_trylock(dst) fails, but would like to allow for
* cases where there might be a race with the previous use of dst.
* This is much like races on refcount of oldpage: just don't BUG().
*/
if (unlikely(!folio_trylock(dst)))
goto out_unlock;
if (unlikely(!is_lru)) {
rc = move_to_new_folio(dst, src, mode);
goto out_unlock_both;
}
/*
* Corner case handling:
* 1. When a new swap-cache page is read into, it is added to the LRU
* and treated as swapcache but it has no rmap yet.
* Calling try_to_unmap() against a src->mapping==NULL page will
* trigger a BUG. So handle it here.
* 2. An orphaned page (see truncate_cleanup_page) might have
* fs-private metadata. The page can be picked up due to memory
* offlining. Everywhere else except page reclaim, the page is
* invisible to the vm, so the page can not be migrated. So try to
* free the metadata, so the page can be freed.
*/
if (!src->mapping) {
if (folio_test_private(src)) {
try_to_free_buffers(src);
goto out_unlock_both;
}
} else if (folio_mapped(src)) {
/* Establish migration ptes */
VM_BUG_ON_FOLIO(folio_test_anon(src) &&
!folio_test_ksm(src) && !anon_vma, src);
try_to_migrate(src, 0);
page_was_mapped = true;
}
if (!folio_mapped(src))
rc = move_to_new_folio(dst, src, mode);
/*
* When successful, push dst to LRU immediately: so that if it
* turns out to be an mlocked page, remove_migration_ptes() will
* automatically build up the correct dst->mlock_count for it.
*
* We would like to do something similar for the old page, when
* unsuccessful, and other cases when a page has been temporarily
* isolated from the unevictable LRU: but this case is the easiest.
*/
if (rc == MIGRATEPAGE_SUCCESS) {
folio_add_lru(dst);
if (page_was_mapped)
lru_add_drain();
}
if (page_was_mapped)
remove_migration_ptes(src,
rc == MIGRATEPAGE_SUCCESS ? dst : src, false);
out_unlock_both:
folio_unlock(dst);
out_unlock:
/* Drop an anon_vma reference if we took one */
if (anon_vma)
put_anon_vma(anon_vma);
folio_unlock(src);
out:
/*
* If migration is successful, decrease refcount of dst,
* which will not free the page because new page owner increased
* refcounter.
*/
if (rc == MIGRATEPAGE_SUCCESS)
folio_put(dst);
return rc;
}
/*
* Obtain the lock on folio, remove all ptes and migrate the folio
* to the newly allocated folio in dst.
*/
static int unmap_and_move(new_page_t get_new_page,
free_page_t put_new_page,
unsigned long private, struct folio *src,
int force, enum migrate_mode mode,
enum migrate_reason reason,
struct list_head *ret)
{
struct folio *dst;
int rc = MIGRATEPAGE_SUCCESS;
struct page *newpage = NULL;
if (!thp_migration_supported() && folio_test_transhuge(src))
return -ENOSYS;
if (folio_ref_count(src) == 1) {
/* Folio was freed from under us. So we are done. */
folio_clear_active(src);
folio_clear_unevictable(src);
/* free_pages_prepare() will clear PG_isolated. */
goto out;
}
newpage = get_new_page(&src->page, private);
if (!newpage)
return -ENOMEM;
dst = page_folio(newpage);
dst->private = NULL;
rc = __unmap_and_move(src, dst, force, mode);
if (rc == MIGRATEPAGE_SUCCESS)
set_page_owner_migrate_reason(&dst->page, reason);
out:
if (rc != -EAGAIN) {
/*
* A folio that has been migrated has all references
* removed and will be freed. A folio that has not been
* migrated will have kept its references and be restored.
*/
list_del(&src->lru);
}
/*
* If migration is successful, releases reference grabbed during
* isolation. Otherwise, restore the folio to right list unless
* we want to retry.
*/
if (rc == MIGRATEPAGE_SUCCESS) {
/*
* Compaction can migrate also non-LRU folios which are
* not accounted to NR_ISOLATED_*. They can be recognized
* as __folio_test_movable
*/
if (likely(!__folio_test_movable(src)))
mod_node_page_state(folio_pgdat(src), NR_ISOLATED_ANON +
folio_is_file_lru(src), -folio_nr_pages(src));
if (reason != MR_MEMORY_FAILURE)
/*
* We release the folio in page_handle_poison.
*/
folio_put(src);
} else {
if (rc != -EAGAIN)
list_add_tail(&src->lru, ret);
if (put_new_page)
put_new_page(&dst->page, private);
else
folio_put(dst);
}
return rc;
}
/*
* Counterpart of unmap_and_move_page() for hugepage migration.
*
* This function doesn't wait the completion of hugepage I/O
* because there is no race between I/O and migration for hugepage.
* Note that currently hugepage I/O occurs only in direct I/O
* where no lock is held and PG_writeback is irrelevant,
* and writeback status of all subpages are counted in the reference
* count of the head page (i.e. if all subpages of a 2MB hugepage are
* under direct I/O, the reference of the head page is 512 and a bit more.)
* This means that when we try to migrate hugepage whose subpages are
* doing direct I/O, some references remain after try_to_unmap() and
* hugepage migration fails without data corruption.
*
* There is also no race when direct I/O is issued on the page under migration,
* because then pte is replaced with migration swap entry and direct I/O code
* will wait in the page fault for migration to complete.
*/
static int unmap_and_move_huge_page(new_page_t get_new_page,
free_page_t put_new_page, unsigned long private,
struct page *hpage, int force,
enum migrate_mode mode, int reason,
struct list_head *ret)
{
struct folio *dst, *src = page_folio(hpage);
int rc = -EAGAIN;
int page_was_mapped = 0;
struct page *new_hpage;
struct anon_vma *anon_vma = NULL;
struct address_space *mapping = NULL;
/*
* Migratability of hugepages depends on architectures and their size.
* This check is necessary because some callers of hugepage migration
* like soft offline and memory hotremove don't walk through page
* tables or check whether the hugepage is pmd-based or not before
* kicking migration.
*/
if (!hugepage_migration_supported(page_hstate(hpage)))
return -ENOSYS;
if (folio_ref_count(src) == 1) {
/* page was freed from under us. So we are done. */
folio_putback_active_hugetlb(src);
return MIGRATEPAGE_SUCCESS;
}
new_hpage = get_new_page(hpage, private);
if (!new_hpage)
return -ENOMEM;
dst = page_folio(new_hpage);
if (!folio_trylock(src)) {
if (!force)
goto out;
switch (mode) {
case MIGRATE_SYNC:
case MIGRATE_SYNC_NO_COPY:
break;
default:
goto out;
}
folio_lock(src);
}
/*
* Check for pages which are in the process of being freed. Without
* folio_mapping() set, hugetlbfs specific move page routine will not
* be called and we could leak usage counts for subpools.
*/
if (hugetlb_folio_subpool(src) && !folio_mapping(src)) {
rc = -EBUSY;
goto out_unlock;
}
if (folio_test_anon(src))
anon_vma = folio_get_anon_vma(src);
if (unlikely(!folio_trylock(dst)))
goto put_anon;
if (folio_mapped(src)) {
enum ttu_flags ttu = 0;
if (!folio_test_anon(src)) {
/*
* In shared mappings, try_to_unmap could potentially
* call huge_pmd_unshare. Because of this, take
* semaphore in write mode here and set TTU_RMAP_LOCKED
* to let lower levels know we have taken the lock.
*/
mapping = hugetlb_page_mapping_lock_write(hpage);
if (unlikely(!mapping))
goto unlock_put_anon;
ttu = TTU_RMAP_LOCKED;
}
try_to_migrate(src, ttu);
page_was_mapped = 1;
if (ttu & TTU_RMAP_LOCKED)
i_mmap_unlock_write(mapping);
}
if (!folio_mapped(src))
rc = move_to_new_folio(dst, src, mode);
if (page_was_mapped)
remove_migration_ptes(src,
rc == MIGRATEPAGE_SUCCESS ? dst : src, false);
unlock_put_anon:
folio_unlock(dst);
put_anon:
if (anon_vma)
put_anon_vma(anon_vma);
if (rc == MIGRATEPAGE_SUCCESS) {
move_hugetlb_state(src, dst, reason);
put_new_page = NULL;
}
out_unlock:
folio_unlock(src);
out:
if (rc == MIGRATEPAGE_SUCCESS)
folio_putback_active_hugetlb(src);
else if (rc != -EAGAIN)
list_move_tail(&src->lru, ret);
/*
* If migration was not successful and there's a freeing callback, use
* it. Otherwise, put_page() will drop the reference grabbed during
* isolation.
*/
if (put_new_page)
put_new_page(new_hpage, private);
else
folio_putback_active_hugetlb(dst);
return rc;
}
static inline int try_split_folio(struct folio *folio, struct list_head *split_folios)
{
int rc;
folio_lock(folio);
rc = split_folio_to_list(folio, split_folios);
folio_unlock(folio);
if (!rc)
list_move_tail(&folio->lru, split_folios);
return rc;
}
/*
* migrate_pages - migrate the folios specified in a list, to the free folios
* supplied as the target for the page migration
*
* @from: The list of folios to be migrated.
* @get_new_page: The function used to allocate free folios to be used
* as the target of the folio migration.
* @put_new_page: The function used to free target folios if migration
* fails, or NULL if no special handling is necessary.
* @private: Private data to be passed on to get_new_page()
* @mode: The migration mode that specifies the constraints for
* folio migration, if any.
* @reason: The reason for folio migration.
* @ret_succeeded: Set to the number of folios migrated successfully if
* the caller passes a non-NULL pointer.
*
* The function returns after 10 attempts or if no folios are movable any more
* because the list has become empty or no retryable folios exist any more.
* It is caller's responsibility to call putback_movable_pages() to return folios
* to the LRU or free list only if ret != 0.
*
* Returns the number of {normal folio, large folio, hugetlb} that were not
* migrated, or an error code. The number of large folio splits will be
* considered as the number of non-migrated large folio, no matter how many
* split folios of the large folio are migrated successfully.
*/
int migrate_pages(struct list_head *from, new_page_t get_new_page,
free_page_t put_new_page, unsigned long private,
enum migrate_mode mode, int reason, unsigned int *ret_succeeded)
{
int retry = 1;
int large_retry = 1;
int thp_retry = 1;
int nr_failed = 0;
int nr_failed_pages = 0;
int nr_retry_pages = 0;
int nr_succeeded = 0;
int nr_thp_succeeded = 0;
int nr_large_failed = 0;
int nr_thp_failed = 0;
int nr_thp_split = 0;
int pass = 0;
bool is_large = false;
bool is_thp = false;
struct folio *folio, *folio2;
int rc, nr_pages;
LIST_HEAD(ret_folios);
LIST_HEAD(split_folios);
bool nosplit = (reason == MR_NUMA_MISPLACED);
bool no_split_folio_counting = false;
trace_mm_migrate_pages_start(mode, reason);
split_folio_migration:
for (pass = 0; pass < 10 && (retry || large_retry); pass++) {
retry = 0;
large_retry = 0;
thp_retry = 0;
nr_retry_pages = 0;
list_for_each_entry_safe(folio, folio2, from, lru) {
/*
* Large folio statistics is based on the source large
* folio. Capture required information that might get
* lost during migration.
*/
is_large = folio_test_large(folio) && !folio_test_hugetlb(folio);
is_thp = is_large && folio_test_pmd_mappable(folio);
nr_pages = folio_nr_pages(folio);
cond_resched();
if (folio_test_hugetlb(folio))
rc = unmap_and_move_huge_page(get_new_page,
put_new_page, private,
&folio->page, pass > 2, mode,
reason,
&ret_folios);
else
rc = unmap_and_move(get_new_page, put_new_page,
private, folio, pass > 2, mode,
reason, &ret_folios);
/*
* The rules are:
* Success: non hugetlb folio will be freed, hugetlb
* folio will be put back
* -EAGAIN: stay on the from list
* -ENOMEM: stay on the from list
* -ENOSYS: stay on the from list
* Other errno: put on ret_folios list then splice to
* from list
*/
switch(rc) {
/*
* Large folio migration might be unsupported or
* the allocation could've failed so we should retry
* on the same folio with the large folio split
* to normal folios.
*
* Split folios are put in split_folios, and
* we will migrate them after the rest of the
* list is processed.
*/
case -ENOSYS:
/* Large folio migration is unsupported */
if (is_large) {
nr_large_failed++;
nr_thp_failed += is_thp;
if (!try_split_folio(folio, &split_folios)) {
nr_thp_split += is_thp;
break;
}
/* Hugetlb migration is unsupported */
} else if (!no_split_folio_counting) {
nr_failed++;
}
nr_failed_pages += nr_pages;
list_move_tail(&folio->lru, &ret_folios);
break;
case -ENOMEM:
/*
* When memory is low, don't bother to try to migrate
* other folios, just exit.
*/
if (is_large) {
nr_large_failed++;
nr_thp_failed += is_thp;
/* Large folio NUMA faulting doesn't split to retry. */
if (!nosplit) {
int ret = try_split_folio(folio, &split_folios);
if (!ret) {
nr_thp_split += is_thp;
break;
} else if (reason == MR_LONGTERM_PIN &&
ret == -EAGAIN) {
/*
* Try again to split large folio to
* mitigate the failure of longterm pinning.
*/
large_retry++;
thp_retry += is_thp;
nr_retry_pages += nr_pages;
break;
}
}
} else if (!no_split_folio_counting) {
nr_failed++;
}
nr_failed_pages += nr_pages + nr_retry_pages;
/*
* There might be some split folios of fail-to-migrate large
* folios left in split_folios list. Move them back to migration
* list so that they could be put back to the right list by
* the caller otherwise the folio refcnt will be leaked.
*/
list_splice_init(&split_folios, from);
/* nr_failed isn't updated for not used */
nr_large_failed += large_retry;
nr_thp_failed += thp_retry;
goto out;
case -EAGAIN:
if (is_large) {
large_retry++;
thp_retry += is_thp;
} else if (!no_split_folio_counting) {
retry++;
}
nr_retry_pages += nr_pages;
break;
case MIGRATEPAGE_SUCCESS:
nr_succeeded += nr_pages;
nr_thp_succeeded += is_thp;
break;
default:
/*
* Permanent failure (-EBUSY, etc.):
* unlike -EAGAIN case, the failed folio is
* removed from migration folio list and not
* retried in the next outer loop.
*/
if (is_large) {
nr_large_failed++;
nr_thp_failed += is_thp;
} else if (!no_split_folio_counting) {
nr_failed++;
}
nr_failed_pages += nr_pages;
break;
}
}
}
nr_failed += retry;
nr_large_failed += large_retry;
nr_thp_failed += thp_retry;
nr_failed_pages += nr_retry_pages;
/*
* Try to migrate split folios of fail-to-migrate large folios, no
* nr_failed counting in this round, since all split folios of a
* large folio is counted as 1 failure in the first round.
*/
if (!list_empty(&split_folios)) {
/*
* Move non-migrated folios (after 10 retries) to ret_folios
* to avoid migrating them again.
*/
list_splice_init(from, &ret_folios);
list_splice_init(&split_folios, from);
no_split_folio_counting = true;
retry = 1;
goto split_folio_migration;
}
rc = nr_failed + nr_large_failed;
out:
/*
* Put the permanent failure folio back to migration list, they
* will be put back to the right list by the caller.
*/
list_splice(&ret_folios, from);
/*
* Return 0 in case all split folios of fail-to-migrate large folios
* are migrated successfully.
*/
if (list_empty(from))
rc = 0;
count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
count_vm_events(PGMIGRATE_FAIL, nr_failed_pages);
count_vm_events(THP_MIGRATION_SUCCESS, nr_thp_succeeded);
count_vm_events(THP_MIGRATION_FAIL, nr_thp_failed);
count_vm_events(THP_MIGRATION_SPLIT, nr_thp_split);
trace_mm_migrate_pages(nr_succeeded, nr_failed_pages, nr_thp_succeeded,
nr_thp_failed, nr_thp_split, mode, reason);
if (ret_succeeded)
*ret_succeeded = nr_succeeded;
return rc;
}
struct page *alloc_migration_target(struct page *page, unsigned long private)
{
struct folio *folio = page_folio(page);
struct migration_target_control *mtc;
gfp_t gfp_mask;
unsigned int order = 0;
struct folio *hugetlb_folio = NULL;
struct folio *new_folio = NULL;
int nid;
int zidx;
mtc = (struct migration_target_control *)private;
gfp_mask = mtc->gfp_mask;
nid = mtc->nid;
if (nid == NUMA_NO_NODE)
nid = folio_nid(folio);
if (folio_test_hugetlb(folio)) {
struct hstate *h = folio_hstate(folio);
gfp_mask = htlb_modify_alloc_mask(h, gfp_mask);
hugetlb_folio = alloc_hugetlb_folio_nodemask(h, nid,
mtc->nmask, gfp_mask);
return &hugetlb_folio->page;
}
if (folio_test_large(folio)) {
/*
* clear __GFP_RECLAIM to make the migration callback
* consistent with regular THP allocations.
*/
gfp_mask &= ~__GFP_RECLAIM;
gfp_mask |= GFP_TRANSHUGE;
order = folio_order(folio);
}
zidx = zone_idx(folio_zone(folio));
if (is_highmem_idx(zidx) || zidx == ZONE_MOVABLE)
gfp_mask |= __GFP_HIGHMEM;
new_folio = __folio_alloc(gfp_mask, order, nid, mtc->nmask);
return &new_folio->page;
}
#ifdef CONFIG_NUMA
static int store_status(int __user *status, int start, int value, int nr)
{
while (nr-- > 0) {
if (put_user(value, status + start))
return -EFAULT;
start++;
}
return 0;
}
static int do_move_pages_to_node(struct mm_struct *mm,
struct list_head *pagelist, int node)
{
int err;
struct migration_target_control mtc = {
.nid = node,
.gfp_mask = GFP_HIGHUSER_MOVABLE | __GFP_THISNODE,
};
err = migrate_pages(pagelist, alloc_migration_target, NULL,
(unsigned long)&mtc, MIGRATE_SYNC, MR_SYSCALL, NULL);
if (err)
putback_movable_pages(pagelist);
return err;
}
/*
* Resolves the given address to a struct page, isolates it from the LRU and
* puts it to the given pagelist.
* Returns:
* errno - if the page cannot be found/isolated
* 0 - when it doesn't have to be migrated because it is already on the
* target node
* 1 - when it has been queued
*/
static int add_page_for_migration(struct mm_struct *mm, unsigned long addr,
int node, struct list_head *pagelist, bool migrate_all)
{
struct vm_area_struct *vma;
struct page *page;
int err;
mmap_read_lock(mm);
err = -EFAULT;
vma = vma_lookup(mm, addr);
if (!vma || !vma_migratable(vma))
goto out;
/* FOLL_DUMP to ignore special (like zero) pages */
page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
err = PTR_ERR(page);
if (IS_ERR(page))
goto out;
err = -ENOENT;
if (!page)
goto out;
if (is_zone_device_page(page))
goto out_putpage;
err = 0;
if (page_to_nid(page) == node)
goto out_putpage;
err = -EACCES;
if (page_mapcount(page) > 1 && !migrate_all)
goto out_putpage;
if (PageHuge(page)) {
if (PageHead(page)) {
err = isolate_hugetlb(page_folio(page), pagelist);
if (!err)
err = 1;
}
} else {
struct page *head;
head = compound_head(page);
err = isolate_lru_page(head);
if (err)
goto out_putpage;
err = 1;
list_add_tail(&head->lru, pagelist);
mod_node_page_state(page_pgdat(head),
NR_ISOLATED_ANON + page_is_file_lru(head),
thp_nr_pages(head));
}
out_putpage:
/*
* Either remove the duplicate refcount from
* isolate_lru_page() or drop the page ref if it was
* not isolated.
*/
put_page(page);
out:
mmap_read_unlock(mm);
return err;
}
static int move_pages_and_store_status(struct mm_struct *mm, int node,
struct list_head *pagelist, int __user *status,
int start, int i, unsigned long nr_pages)
{
int err;
if (list_empty(pagelist))
return 0;
err = do_move_pages_to_node(mm, pagelist, node);
if (err) {
/*
* Positive err means the number of failed
* pages to migrate. Since we are going to
* abort and return the number of non-migrated
* pages, so need to include the rest of the
* nr_pages that have not been attempted as
* well.
*/
if (err > 0)
err += nr_pages - i;
return err;
}
return store_status(status, start, node, i - start);
}
/*
* Migrate an array of page address onto an array of nodes and fill
* the corresponding array of status.
*/
static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
unsigned long nr_pages,
const void __user * __user *pages,
const int __user *nodes,
int __user *status, int flags)
{
int current_node = NUMA_NO_NODE;
LIST_HEAD(pagelist);
int start, i;
int err = 0, err1;
lru_cache_disable();
for (i = start = 0; i < nr_pages; i++) {
const void __user *p;
unsigned long addr;
int node;
err = -EFAULT;
if (get_user(p, pages + i))
goto out_flush;
if (get_user(node, nodes + i))
goto out_flush;
addr = (unsigned long)untagged_addr(p);
err = -ENODEV;
if (node < 0 || node >= MAX_NUMNODES)
goto out_flush;
if (!node_state(node, N_MEMORY))
goto out_flush;
err = -EACCES;
if (!node_isset(node, task_nodes))
goto out_flush;
if (current_node == NUMA_NO_NODE) {
current_node = node;
start = i;
} else if (node != current_node) {
err = move_pages_and_store_status(mm, current_node,
&pagelist, status, start, i, nr_pages);
if (err)
goto out;
start = i;
current_node = node;
}
/*
* Errors in the page lookup or isolation are not fatal and we simply
* report them via status
*/
err = add_page_for_migration(mm, addr, current_node,
&pagelist, flags & MPOL_MF_MOVE_ALL);
if (err > 0) {
/* The page is successfully queued for migration */
continue;
}
/*
* The move_pages() man page does not have an -EEXIST choice, so
* use -EFAULT instead.
*/
if (err == -EEXIST)
err = -EFAULT;
/*
* If the page is already on the target node (!err), store the
* node, otherwise, store the err.
*/
err = store_status(status, i, err ? : current_node, 1);
if (err)
goto out_flush;
err = move_pages_and_store_status(mm, current_node, &pagelist,
status, start, i, nr_pages);
if (err) {
/* We have accounted for page i */
if (err > 0)
err--;
goto out;
}
current_node = NUMA_NO_NODE;
}
out_flush:
/* Make sure we do not overwrite the existing error */
err1 = move_pages_and_store_status(mm, current_node, &pagelist,
status, start, i, nr_pages);
if (err >= 0)
err = err1;
out:
lru_cache_enable();
return err;
}
/*
* Determine the nodes of an array of pages and store it in an array of status.
*/
static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
const void __user **pages, int *status)
{
unsigned long i;
mmap_read_lock(mm);
for (i = 0; i < nr_pages; i++) {
unsigned long addr = (unsigned long)(*pages);
struct vm_area_struct *vma;
struct page *page;
int err = -EFAULT;
vma = vma_lookup(mm, addr);
if (!vma)
goto set_status;
/* FOLL_DUMP to ignore special (like zero) pages */
page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
err = PTR_ERR(page);
if (IS_ERR(page))
goto set_status;
err = -ENOENT;
if (!page)
goto set_status;
if (!is_zone_device_page(page))
err = page_to_nid(page);
put_page(page);
set_status:
*status = err;
pages++;
status++;
}
mmap_read_unlock(mm);
}
static int get_compat_pages_array(const void __user *chunk_pages[],
const void __user * __user *pages,
unsigned long chunk_nr)
{
compat_uptr_t __user *pages32 = (compat_uptr_t __user *)pages;
compat_uptr_t p;
int i;
for (i = 0; i < chunk_nr; i++) {
if (get_user(p, pages32 + i))
return -EFAULT;
chunk_pages[i] = compat_ptr(p);
}
return 0;
}
/*
* Determine the nodes of a user array of pages and store it in
* a user array of status.
*/
static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
const void __user * __user *pages,
int __user *status)
{
#define DO_PAGES_STAT_CHUNK_NR 16UL
const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
int chunk_status[DO_PAGES_STAT_CHUNK_NR];
while (nr_pages) {
unsigned long chunk_nr = min(nr_pages, DO_PAGES_STAT_CHUNK_NR);
if (in_compat_syscall()) {
if (get_compat_pages_array(chunk_pages, pages,
chunk_nr))
break;
} else {
if (copy_from_user(chunk_pages, pages,
chunk_nr * sizeof(*chunk_pages)))
break;
}
do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
break;
pages += chunk_nr;
status += chunk_nr;
nr_pages -= chunk_nr;
}
return nr_pages ? -EFAULT : 0;
}
static struct mm_struct *find_mm_struct(pid_t pid, nodemask_t *mem_nodes)
{
struct task_struct *task;
struct mm_struct *mm;
/*
* There is no need to check if current process has the right to modify
* the specified process when they are same.
*/
if (!pid) {
mmget(current->mm);
*mem_nodes = cpuset_mems_allowed(current);
return current->mm;
}
/* Find the mm_struct */
rcu_read_lock();
task = find_task_by_vpid(pid);
if (!task) {
rcu_read_unlock();
return ERR_PTR(-ESRCH);
}
get_task_struct(task);
/*
* Check if this process has the right to modify the specified
* process. Use the regular "ptrace_may_access()" checks.
*/
if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
rcu_read_unlock();
mm = ERR_PTR(-EPERM);
goto out;
}
rcu_read_unlock();
mm = ERR_PTR(security_task_movememory(task));
if (IS_ERR(mm))
goto out;
*mem_nodes = cpuset_mems_allowed(task);
mm = get_task_mm(task);
out:
put_task_struct(task);
if (!mm)
mm = ERR_PTR(-EINVAL);
return mm;
}
/*
* Move a list of pages in the address space of the currently executing
* process.
*/
static int kernel_move_pages(pid_t pid, unsigned long nr_pages,
const void __user * __user *pages,
const int __user *nodes,
int __user *status, int flags)
{
struct mm_struct *mm;
int err;
nodemask_t task_nodes;
/* Check flags */
if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
return -EINVAL;
if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
return -EPERM;
mm = find_mm_struct(pid, &task_nodes);
if (IS_ERR(mm))
return PTR_ERR(mm);
if (nodes)
err = do_pages_move(mm, task_nodes, nr_pages, pages,
nodes, status, flags);
else
err = do_pages_stat(mm, nr_pages, pages, status);
mmput(mm);
return err;
}
SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
const void __user * __user *, pages,
const int __user *, nodes,
int __user *, status, int, flags)
{
return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags);
}
#ifdef CONFIG_NUMA_BALANCING
/*
* Returns true if this is a safe migration target node for misplaced NUMA
* pages. Currently it only checks the watermarks which is crude.
*/
static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
unsigned long nr_migrate_pages)
{
int z;
for (z = pgdat->nr_zones - 1; z >= 0; z--) {
struct zone *zone = pgdat->node_zones + z;
if (!managed_zone(zone))
continue;
/* Avoid waking kswapd by allocating pages_to_migrate pages. */
if (!zone_watermark_ok(zone, 0,
high_wmark_pages(zone) +
nr_migrate_pages,
ZONE_MOVABLE, 0))
continue;
return true;
}
return false;
}
static struct page *alloc_misplaced_dst_page(struct page *page,
unsigned long data)
{
int nid = (int) data;
int order = compound_order(page);
gfp_t gfp = __GFP_THISNODE;
struct folio *new;
if (order > 0)
gfp |= GFP_TRANSHUGE_LIGHT;
else {
gfp |= GFP_HIGHUSER_MOVABLE | __GFP_NOMEMALLOC | __GFP_NORETRY |
__GFP_NOWARN;
gfp &= ~__GFP_RECLAIM;
}
new = __folio_alloc_node(gfp, order, nid);
return &new->page;
}
static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
{
int nr_pages = thp_nr_pages(page);
int order = compound_order(page);
VM_BUG_ON_PAGE(order && !PageTransHuge(page), page);
/* Do not migrate THP mapped by multiple processes */
if (PageTransHuge(page) && total_mapcount(page) > 1)
return 0;
/* Avoid migrating to a node that is nearly full */
if (!migrate_balanced_pgdat(pgdat, nr_pages)) {
int z;
if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING))
return 0;
for (z = pgdat->nr_zones - 1; z >= 0; z--) {
if (managed_zone(pgdat->node_zones + z))
break;
}
wakeup_kswapd(pgdat->node_zones + z, 0, order, ZONE_MOVABLE);
return 0;
}
if (isolate_lru_page(page))
return 0;
mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_is_file_lru(page),
nr_pages);
/*
* Isolating the page has taken another reference, so the
* caller's reference can be safely dropped without the page
* disappearing underneath us during migration.
*/
put_page(page);
return 1;
}
/*
* Attempt to migrate a misplaced page to the specified destination
* node. Caller is expected to have an elevated reference count on
* the page that will be dropped by this function before returning.
*/
int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
int node)
{
pg_data_t *pgdat = NODE_DATA(node);
int isolated;
int nr_remaining;
unsigned int nr_succeeded;
LIST_HEAD(migratepages);
int nr_pages = thp_nr_pages(page);
/*
* Don't migrate file pages that are mapped in multiple processes
* with execute permissions as they are probably shared libraries.
*/
if (page_mapcount(page) != 1 && page_is_file_lru(page) &&
(vma->vm_flags & VM_EXEC))
goto out;
/*
* Also do not migrate dirty pages as not all filesystems can move
* dirty pages in MIGRATE_ASYNC mode which is a waste of cycles.
*/
if (page_is_file_lru(page) && PageDirty(page))
goto out;
isolated = numamigrate_isolate_page(pgdat, page);
if (!isolated)
goto out;
list_add(&page->lru, &migratepages);
nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page,
NULL, node, MIGRATE_ASYNC,
MR_NUMA_MISPLACED, &nr_succeeded);
if (nr_remaining) {
if (!list_empty(&migratepages)) {
list_del(&page->lru);
mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
page_is_file_lru(page), -nr_pages);
putback_lru_page(page);
}
isolated = 0;
}
if (nr_succeeded) {
count_vm_numa_events(NUMA_PAGE_MIGRATE, nr_succeeded);
if (!node_is_toptier(page_to_nid(page)) && node_is_toptier(node))
mod_node_page_state(pgdat, PGPROMOTE_SUCCESS,
nr_succeeded);
}
BUG_ON(!list_empty(&migratepages));
return isolated;
out:
put_page(page);
return 0;
}
#endif /* CONFIG_NUMA_BALANCING */
#endif /* CONFIG_NUMA */
