https://github.com/torvalds/linux
Tip revision: 9e1ff307c779ce1f0f810c7ecce3d95bbae40896 authored by Linus Torvalds on 03 October 2021, 21:08:47 UTC
Linux 5.15-rc4
Linux 5.15-rc4
Tip revision: 9e1ff30
migrate.c
// 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/pagewalk.h>
#include <linux/pfn_t.h>
#include <linux/memremap.h>
#include <linux/userfaultfd_k.h>
#include <linux/balloon_compaction.h>
#include <linux/mmu_notifier.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 <asm/tlbflush.h>
#define CREATE_TRACE_POINTS
#include <trace/events/migrate.h>
#include "internal.h"
int isolate_movable_page(struct page *page, isolate_mode_t mode)
{
struct address_space *mapping;
/*
* 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;
/*
* Check PageMovable before holding a PG_lock because page's owner
* assumes anybody doesn't touch PG_lock of newly allocated page
* so unconditionally grabbing the lock ruins page's owner side.
*/
if (unlikely(!__PageMovable(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;
mapping = page_mapping(page);
VM_BUG_ON_PAGE(!mapping, page);
if (!mapping->a_ops->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)
{
struct address_space *mapping;
mapping = page_mapping(page);
mapping->a_ops->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_huge_page().
*/
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))) {
putback_active_hugepage(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 page *page, struct vm_area_struct *vma,
unsigned long addr, void *old)
{
struct page_vma_mapped_walk pvmw = {
.page = old,
.vma = vma,
.address = addr,
.flags = PVMW_SYNC | PVMW_MIGRATION,
};
struct page *new;
pte_t pte;
swp_entry_t entry;
VM_BUG_ON_PAGE(PageTail(page), page);
while (page_vma_mapped_walk(&pvmw)) {
if (PageKsm(page))
new = page;
else
new = page - pvmw.page->index +
linear_page_index(vma, pvmw.address);
#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
/* PMD-mapped THP migration entry */
if (!pvmw.pte) {
VM_BUG_ON_PAGE(PageHuge(page) || !PageTransCompound(page), page);
remove_migration_pmd(&pvmw, new);
continue;
}
#endif
get_page(new);
pte = pte_mkold(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_writable_migration_entry(entry))
pte = maybe_mkwrite(pte, vma);
else if (pte_swp_uffd_wp(*pvmw.pte))
pte = pte_mkuffd_wp(pte);
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 (PageHuge(new)) {
unsigned int shift = huge_page_shift(hstate_vma(vma));
pte = pte_mkhuge(pte);
pte = arch_make_huge_pte(pte, shift, vma->vm_flags);
set_huge_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
if (PageAnon(new))
hugepage_add_anon_rmap(new, vma, pvmw.address);
else
page_dup_rmap(new, true);
} else
#endif
{
set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
if (PageAnon(new))
page_add_anon_rmap(new, vma, pvmw.address, false);
else
page_add_file_rmap(new, false);
}
if (vma->vm_flags & VM_LOCKED && !PageTransCompound(new))
mlock_vma_page(new);
if (PageTransHuge(page) && PageMlocked(page))
clear_page_mlock(page);
/* 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 page *old, struct page *new, bool locked)
{
struct rmap_walk_control rwc = {
.rmap_one = remove_migration_pte,
.arg = old,
};
if (locked)
rmap_walk_locked(new, &rwc);
else
rmap_walk(new, &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;
struct page *page;
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;
page = pfn_swap_entry_to_page(entry);
page = compound_head(page);
/*
* Once page cache replacement of page migration started, page_count
* is zero; but we must not call put_and_wait_on_page_locked() without
* a ref. Use get_page_unless_zero(), and just fault again if it fails.
*/
if (!get_page_unless_zero(page))
goto out;
pte_unmap_unlock(ptep, ptl);
put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE);
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);
}
void migration_entry_wait_huge(struct vm_area_struct *vma,
struct mm_struct *mm, pte_t *pte)
{
spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte);
__migration_entry_wait(mm, pte, ptl);
}
#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
{
spinlock_t *ptl;
struct page *page;
ptl = pmd_lock(mm, pmd);
if (!is_pmd_migration_entry(*pmd))
goto unlock;
page = pfn_swap_entry_to_page(pmd_to_swp_entry(*pmd));
if (!get_page_unless_zero(page))
goto unlock;
spin_unlock(ptl);
put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE);
return;
unlock:
spin_unlock(ptl);
}
#endif
static int expected_page_refs(struct address_space *mapping, struct page *page)
{
int expected_count = 1;
/*
* Device private pages have an extra refcount as they are
* ZONE_DEVICE pages.
*/
expected_count += is_device_private_page(page);
if (mapping)
expected_count += thp_nr_pages(page) + page_has_private(page);
return expected_count;
}
/*
* 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 migrate_page_move_mapping(struct address_space *mapping,
struct page *newpage, struct page *page, int extra_count)
{
XA_STATE(xas, &mapping->i_pages, page_index(page));
struct zone *oldzone, *newzone;
int dirty;
int expected_count = expected_page_refs(mapping, page) + extra_count;
int nr = thp_nr_pages(page);
if (!mapping) {
/* Anonymous page without mapping */
if (page_count(page) != expected_count)
return -EAGAIN;
/* No turning back from here */
newpage->index = page->index;
newpage->mapping = page->mapping;
if (PageSwapBacked(page))
__SetPageSwapBacked(newpage);
return MIGRATEPAGE_SUCCESS;
}
oldzone = page_zone(page);
newzone = page_zone(newpage);
xas_lock_irq(&xas);
if (page_count(page) != expected_count || xas_load(&xas) != page) {
xas_unlock_irq(&xas);
return -EAGAIN;
}
if (!page_ref_freeze(page, expected_count)) {
xas_unlock_irq(&xas);
return -EAGAIN;
}
/*
* Now we know that no one else is looking at the page:
* no turning back from here.
*/
newpage->index = page->index;
newpage->mapping = page->mapping;
page_ref_add(newpage, nr); /* add cache reference */
if (PageSwapBacked(page)) {
__SetPageSwapBacked(newpage);
if (PageSwapCache(page)) {
SetPageSwapCache(newpage);
set_page_private(newpage, page_private(page));
}
} else {
VM_BUG_ON_PAGE(PageSwapCache(page), page);
}
/* Move dirty while page refs frozen and newpage not yet exposed */
dirty = PageDirty(page);
if (dirty) {
ClearPageDirty(page);
SetPageDirty(newpage);
}
xas_store(&xas, newpage);
if (PageTransHuge(page)) {
int i;
for (i = 1; i < nr; i++) {
xas_next(&xas);
xas_store(&xas, newpage);
}
}
/*
* Drop cache reference from old page by unfreezing
* to one less reference.
* We know this isn't the last reference.
*/
page_ref_unfreeze(page, 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 = page_memcg(page);
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 (PageSwapBacked(page) && !PageSwapCache(page)) {
__mod_lruvec_state(old_lruvec, NR_SHMEM, -nr);
__mod_lruvec_state(new_lruvec, NR_SHMEM, nr);
}
#ifdef CONFIG_SWAP
if (PageSwapCache(page)) {
__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(migrate_page_move_mapping);
/*
* The expected number of remaining references is the same as that
* of migrate_page_move_mapping().
*/
int migrate_huge_page_move_mapping(struct address_space *mapping,
struct page *newpage, struct page *page)
{
XA_STATE(xas, &mapping->i_pages, page_index(page));
int expected_count;
xas_lock_irq(&xas);
expected_count = 2 + page_has_private(page);
if (page_count(page) != expected_count || xas_load(&xas) != page) {
xas_unlock_irq(&xas);
return -EAGAIN;
}
if (!page_ref_freeze(page, expected_count)) {
xas_unlock_irq(&xas);
return -EAGAIN;
}
newpage->index = page->index;
newpage->mapping = page->mapping;
get_page(newpage);
xas_store(&xas, newpage);
page_ref_unfreeze(page, expected_count - 1);
xas_unlock_irq(&xas);
return MIGRATEPAGE_SUCCESS;
}
/*
* Copy the page to its new location
*/
void migrate_page_states(struct page *newpage, struct page *page)
{
int cpupid;
if (PageError(page))
SetPageError(newpage);
if (PageReferenced(page))
SetPageReferenced(newpage);
if (PageUptodate(page))
SetPageUptodate(newpage);
if (TestClearPageActive(page)) {
VM_BUG_ON_PAGE(PageUnevictable(page), page);
SetPageActive(newpage);
} else if (TestClearPageUnevictable(page))
SetPageUnevictable(newpage);
if (PageWorkingset(page))
SetPageWorkingset(newpage);
if (PageChecked(page))
SetPageChecked(newpage);
if (PageMappedToDisk(page))
SetPageMappedToDisk(newpage);
/* Move dirty on pages not done by migrate_page_move_mapping() */
if (PageDirty(page))
SetPageDirty(newpage);
if (page_is_young(page))
set_page_young(newpage);
if (page_is_idle(page))
set_page_idle(newpage);
/*
* Copy NUMA information to the new page, to prevent over-eager
* future migrations of this same page.
*/
cpupid = page_cpupid_xchg_last(page, -1);
page_cpupid_xchg_last(newpage, cpupid);
ksm_migrate_page(newpage, page);
/*
* Please do not reorder this without considering how mm/ksm.c's
* get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
*/
if (PageSwapCache(page))
ClearPageSwapCache(page);
ClearPagePrivate(page);
/* page->private contains hugetlb specific flags */
if (!PageHuge(page))
set_page_private(page, 0);
/*
* If any waiters have accumulated on the new page then
* wake them up.
*/
if (PageWriteback(newpage))
end_page_writeback(newpage);
/*
* 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 (PageReadahead(page))
SetPageReadahead(newpage);
copy_page_owner(page, newpage);
if (!PageHuge(page))
mem_cgroup_migrate(page, newpage);
}
EXPORT_SYMBOL(migrate_page_states);
void migrate_page_copy(struct page *newpage, struct page *page)
{
if (PageHuge(page) || PageTransHuge(page))
copy_huge_page(newpage, page);
else
copy_highpage(newpage, page);
migrate_page_states(newpage, page);
}
EXPORT_SYMBOL(migrate_page_copy);
/************************************************************
* Migration functions
***********************************************************/
/*
* Common logic to directly migrate a single LRU page suitable for
* pages that do not use PagePrivate/PagePrivate2.
*
* Pages are locked upon entry and exit.
*/
int migrate_page(struct address_space *mapping,
struct page *newpage, struct page *page,
enum migrate_mode mode)
{
int rc;
BUG_ON(PageWriteback(page)); /* Writeback must be complete */
rc = migrate_page_move_mapping(mapping, newpage, page, 0);
if (rc != MIGRATEPAGE_SUCCESS)
return rc;
if (mode != MIGRATE_SYNC_NO_COPY)
migrate_page_copy(newpage, page);
else
migrate_page_states(newpage, page);
return MIGRATEPAGE_SUCCESS;
}
EXPORT_SYMBOL(migrate_page);
#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_page(struct address_space *mapping,
struct page *newpage, struct page *page, enum migrate_mode mode,
bool check_refs)
{
struct buffer_head *bh, *head;
int rc;
int expected_count;
if (!page_has_buffers(page))
return migrate_page(mapping, newpage, page, mode);
/* Check whether page does not have extra refs before we do more work */
expected_count = expected_page_refs(mapping, page);
if (page_count(page) != expected_count)
return -EAGAIN;
head = page_buffers(page);
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 = migrate_page_move_mapping(mapping, newpage, page, 0);
if (rc != MIGRATEPAGE_SUCCESS)
goto unlock_buffers;
attach_page_private(newpage, detach_page_private(page));
bh = head;
do {
set_bh_page(bh, newpage, bh_offset(bh));
bh = bh->b_this_page;
} while (bh != head);
if (mode != MIGRATE_SYNC_NO_COPY)
migrate_page_copy(newpage, page);
else
migrate_page_states(newpage, page);
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;
}
/*
* Migration function for pages with buffers. This function can only be used
* if the underlying filesystem guarantees that no other references to "page"
* exist. For example attached buffer heads are accessed only under page lock.
*/
int buffer_migrate_page(struct address_space *mapping,
struct page *newpage, struct page *page, enum migrate_mode mode)
{
return __buffer_migrate_page(mapping, newpage, page, mode, false);
}
EXPORT_SYMBOL(buffer_migrate_page);
/*
* Same as above 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).
*/
int buffer_migrate_page_norefs(struct address_space *mapping,
struct page *newpage, struct page *page, enum migrate_mode mode)
{
return __buffer_migrate_page(mapping, newpage, page, mode, true);
}
#endif
/*
* Writeback a page to clean the dirty state
*/
static int writeout(struct address_space *mapping, struct page *page)
{
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 (!clear_page_dirty_for_io(page))
/* Someone else already triggered a write */
return -EAGAIN;
/*
* A dirty page may imply that the underlying filesystem has
* the page on some queue. So the page must be clean for
* migration. Writeout may mean we loose the lock and the
* page state is no longer what we checked for earlier.
* At this point we know that the migration attempt cannot
* be successful.
*/
remove_migration_ptes(page, page, false);
rc = mapping->a_ops->writepage(page, &wbc);
if (rc != AOP_WRITEPAGE_ACTIVATE)
/* unlocked. Relock */
lock_page(page);
return (rc < 0) ? -EIO : -EAGAIN;
}
/*
* Default handling if a filesystem does not provide a migration function.
*/
static int fallback_migrate_page(struct address_space *mapping,
struct page *newpage, struct page *page, enum migrate_mode mode)
{
if (PageDirty(page)) {
/* Only writeback pages in full synchronous migration */
switch (mode) {
case MIGRATE_SYNC:
case MIGRATE_SYNC_NO_COPY:
break;
default:
return -EBUSY;
}
return writeout(mapping, page);
}
/*
* Buffers may be managed in a filesystem specific way.
* We must have no buffers or drop them.
*/
if (page_has_private(page) &&
!try_to_release_page(page, GFP_KERNEL))
return mode == MIGRATE_SYNC ? -EAGAIN : -EBUSY;
return migrate_page(mapping, newpage, page, 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_page(struct page *newpage, struct page *page,
enum migrate_mode mode)
{
struct address_space *mapping;
int rc = -EAGAIN;
bool is_lru = !__PageMovable(page);
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
mapping = page_mapping(page);
if (likely(is_lru)) {
if (!mapping)
rc = migrate_page(mapping, newpage, page, mode);
else if (mapping->a_ops->migratepage)
/*
* Most pages have a mapping and most filesystems
* provide a migratepage callback. Anonymous pages
* are part of swap space which also has its own
* migratepage callback. This is the most common path
* for page migration.
*/
rc = mapping->a_ops->migratepage(mapping, newpage,
page, mode);
else
rc = fallback_migrate_page(mapping, newpage,
page, mode);
} else {
/*
* In case of non-lru page, it could be released after
* isolation step. In that case, we shouldn't try migration.
*/
VM_BUG_ON_PAGE(!PageIsolated(page), page);
if (!PageMovable(page)) {
rc = MIGRATEPAGE_SUCCESS;
__ClearPageIsolated(page);
goto out;
}
rc = mapping->a_ops->migratepage(mapping, newpage,
page, mode);
WARN_ON_ONCE(rc == MIGRATEPAGE_SUCCESS &&
!PageIsolated(page));
}
/*
* When successful, old pagecache page->mapping must be cleared before
* page is freed; but stats require that PageAnon be left as PageAnon.
*/
if (rc == MIGRATEPAGE_SUCCESS) {
if (__PageMovable(page)) {
VM_BUG_ON_PAGE(!PageIsolated(page), page);
/*
* We clear PG_movable under page_lock so any compactor
* cannot try to migrate this page.
*/
__ClearPageIsolated(page);
}
/*
* Anonymous and movable page->mapping will be cleared by
* free_pages_prepare so don't reset it here for keeping
* the type to work PageAnon, for example.
*/
if (!PageMappingFlags(page))
page->mapping = NULL;
if (likely(!is_zone_device_page(newpage)))
flush_dcache_page(newpage);
}
out:
return rc;
}
static int __unmap_and_move(struct page *page, struct page *newpage,
int force, enum migrate_mode mode)
{
int rc = -EAGAIN;
bool page_was_mapped = false;
struct anon_vma *anon_vma = NULL;
bool is_lru = !__PageMovable(page);
if (!trylock_page(page)) {
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;
lock_page(page);
}
if (PageWriteback(page)) {
/*
* 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;
wait_on_page_writeback(page);
}
/*
* By try_to_migrate(), page->mapcount goes down to 0 here. In this case,
* we cannot notice that anon_vma is freed while we migrates 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 page_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 (PageAnon(page) && !PageKsm(page))
anon_vma = page_get_anon_vma(page);
/*
* 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 newpage at this point. We used to have a BUG
* here if trylock_page(newpage) fails, but would like to allow for
* cases where there might be a race with the previous use of newpage.
* This is much like races on refcount of oldpage: just don't BUG().
*/
if (unlikely(!trylock_page(newpage)))
goto out_unlock;
if (unlikely(!is_lru)) {
rc = move_to_new_page(newpage, page, 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 page->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 (!page->mapping) {
VM_BUG_ON_PAGE(PageAnon(page), page);
if (page_has_private(page)) {
try_to_free_buffers(page);
goto out_unlock_both;
}
} else if (page_mapped(page)) {
/* Establish migration ptes */
VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma,
page);
try_to_migrate(page, 0);
page_was_mapped = true;
}
if (!page_mapped(page))
rc = move_to_new_page(newpage, page, mode);
if (page_was_mapped)
remove_migration_ptes(page,
rc == MIGRATEPAGE_SUCCESS ? newpage : page, false);
out_unlock_both:
unlock_page(newpage);
out_unlock:
/* Drop an anon_vma reference if we took one */
if (anon_vma)
put_anon_vma(anon_vma);
unlock_page(page);
out:
/*
* If migration is successful, decrease refcount of the newpage
* which will not free the page because new page owner increased
* refcounter. As well, if it is LRU page, add the page to LRU
* list in here. Use the old state of the isolated source page to
* determine if we migrated a LRU page. newpage was already unlocked
* and possibly modified by its owner - don't rely on the page
* state.
*/
if (rc == MIGRATEPAGE_SUCCESS) {
if (unlikely(!is_lru))
put_page(newpage);
else
putback_lru_page(newpage);
}
return rc;
}
/*
* node_demotion[] example:
*
* Consider a system with two sockets. Each socket has
* three classes of memory attached: fast, medium and slow.
* Each memory class is placed in its own NUMA node. The
* CPUs are placed in the node with the "fast" memory. The
* 6 NUMA nodes (0-5) might be split among the sockets like
* this:
*
* Socket A: 0, 1, 2
* Socket B: 3, 4, 5
*
* When Node 0 fills up, its memory should be migrated to
* Node 1. When Node 1 fills up, it should be migrated to
* Node 2. The migration path start on the nodes with the
* processors (since allocations default to this node) and
* fast memory, progress through medium and end with the
* slow memory:
*
* 0 -> 1 -> 2 -> stop
* 3 -> 4 -> 5 -> stop
*
* This is represented in the node_demotion[] like this:
*
* { 1, // Node 0 migrates to 1
* 2, // Node 1 migrates to 2
* -1, // Node 2 does not migrate
* 4, // Node 3 migrates to 4
* 5, // Node 4 migrates to 5
* -1} // Node 5 does not migrate
*/
/*
* Writes to this array occur without locking. Cycles are
* not allowed: Node X demotes to Y which demotes to X...
*
* If multiple reads are performed, a single rcu_read_lock()
* must be held over all reads to ensure that no cycles are
* observed.
*/
static int node_demotion[MAX_NUMNODES] __read_mostly =
{[0 ... MAX_NUMNODES - 1] = NUMA_NO_NODE};
/**
* next_demotion_node() - Get the next node in the demotion path
* @node: The starting node to lookup the next node
*
* Return: node id for next memory node in the demotion path hierarchy
* from @node; NUMA_NO_NODE if @node is terminal. This does not keep
* @node online or guarantee that it *continues* to be the next demotion
* target.
*/
int next_demotion_node(int node)
{
int target;
/*
* node_demotion[] is updated without excluding this
* function from running. RCU doesn't provide any
* compiler barriers, so the READ_ONCE() is required
* to avoid compiler reordering or read merging.
*
* Make sure to use RCU over entire code blocks if
* node_demotion[] reads need to be consistent.
*/
rcu_read_lock();
target = READ_ONCE(node_demotion[node]);
rcu_read_unlock();
return target;
}
/*
* Obtain the lock on page, remove all ptes and migrate the page
* to the newly allocated page in newpage.
*/
static int unmap_and_move(new_page_t get_new_page,
free_page_t put_new_page,
unsigned long private, struct page *page,
int force, enum migrate_mode mode,
enum migrate_reason reason,
struct list_head *ret)
{
int rc = MIGRATEPAGE_SUCCESS;
struct page *newpage = NULL;
if (!thp_migration_supported() && PageTransHuge(page))
return -ENOSYS;
if (page_count(page) == 1) {
/* page was freed from under us. So we are done. */
ClearPageActive(page);
ClearPageUnevictable(page);
if (unlikely(__PageMovable(page))) {
lock_page(page);
if (!PageMovable(page))
__ClearPageIsolated(page);
unlock_page(page);
}
goto out;
}
newpage = get_new_page(page, private);
if (!newpage)
return -ENOMEM;
rc = __unmap_and_move(page, newpage, force, mode);
if (rc == MIGRATEPAGE_SUCCESS)
set_page_owner_migrate_reason(newpage, reason);
out:
if (rc != -EAGAIN) {
/*
* A page that has been migrated has all references
* removed and will be freed. A page that has not been
* migrated will have kept its references and be restored.
*/
list_del(&page->lru);
}
/*
* If migration is successful, releases reference grabbed during
* isolation. Otherwise, restore the page to right list unless
* we want to retry.
*/
if (rc == MIGRATEPAGE_SUCCESS) {
/*
* Compaction can migrate also non-LRU pages which are
* not accounted to NR_ISOLATED_*. They can be recognized
* as __PageMovable
*/
if (likely(!__PageMovable(page)))
mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
page_is_file_lru(page), -thp_nr_pages(page));
if (reason != MR_MEMORY_FAILURE)
/*
* We release the page in page_handle_poison.
*/
put_page(page);
} else {
if (rc != -EAGAIN)
list_add_tail(&page->lru, ret);
if (put_new_page)
put_new_page(newpage, private);
else
put_page(newpage);
}
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)
{
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))) {
list_move_tail(&hpage->lru, ret);
return -ENOSYS;
}
if (page_count(hpage) == 1) {
/* page was freed from under us. So we are done. */
putback_active_hugepage(hpage);
return MIGRATEPAGE_SUCCESS;
}
new_hpage = get_new_page(hpage, private);
if (!new_hpage)
return -ENOMEM;
if (!trylock_page(hpage)) {
if (!force)
goto out;
switch (mode) {
case MIGRATE_SYNC:
case MIGRATE_SYNC_NO_COPY:
break;
default:
goto out;
}
lock_page(hpage);
}
/*
* Check for pages which are in the process of being freed. Without
* page_mapping() set, hugetlbfs specific move page routine will not
* be called and we could leak usage counts for subpools.
*/
if (hugetlb_page_subpool(hpage) && !page_mapping(hpage)) {
rc = -EBUSY;
goto out_unlock;
}
if (PageAnon(hpage))
anon_vma = page_get_anon_vma(hpage);
if (unlikely(!trylock_page(new_hpage)))
goto put_anon;
if (page_mapped(hpage)) {
bool mapping_locked = false;
enum ttu_flags ttu = 0;
if (!PageAnon(hpage)) {
/*
* 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;
mapping_locked = true;
ttu |= TTU_RMAP_LOCKED;
}
try_to_migrate(hpage, ttu);
page_was_mapped = 1;
if (mapping_locked)
i_mmap_unlock_write(mapping);
}
if (!page_mapped(hpage))
rc = move_to_new_page(new_hpage, hpage, mode);
if (page_was_mapped)
remove_migration_ptes(hpage,
rc == MIGRATEPAGE_SUCCESS ? new_hpage : hpage, false);
unlock_put_anon:
unlock_page(new_hpage);
put_anon:
if (anon_vma)
put_anon_vma(anon_vma);
if (rc == MIGRATEPAGE_SUCCESS) {
move_hugetlb_state(hpage, new_hpage, reason);
put_new_page = NULL;
}
out_unlock:
unlock_page(hpage);
out:
if (rc == MIGRATEPAGE_SUCCESS)
putback_active_hugepage(hpage);
else if (rc != -EAGAIN)
list_move_tail(&hpage->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
putback_active_hugepage(new_hpage);
return rc;
}
static inline int try_split_thp(struct page *page, struct page **page2,
struct list_head *from)
{
int rc = 0;
lock_page(page);
rc = split_huge_page_to_list(page, from);
unlock_page(page);
if (!rc)
list_safe_reset_next(page, *page2, lru);
return rc;
}
/*
* migrate_pages - migrate the pages specified in a list, to the free pages
* supplied as the target for the page migration
*
* @from: The list of pages to be migrated.
* @get_new_page: The function used to allocate free pages to be used
* as the target of the page migration.
* @put_new_page: The function used to free target pages 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
* page migration, if any.
* @reason: The reason for page migration.
* @ret_succeeded: Set to the number of pages migrated successfully if
* the caller passes a non-NULL pointer.
*
* The function returns after 10 attempts or if no pages are movable any more
* because the list has become empty or no retryable pages exist any more.
* It is caller's responsibility to call putback_movable_pages() to return pages
* to the LRU or free list only if ret != 0.
*
* Returns the number of pages that were not migrated, or an error code.
*/
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 thp_retry = 1;
int nr_failed = 0;
int nr_succeeded = 0;
int nr_thp_succeeded = 0;
int nr_thp_failed = 0;
int nr_thp_split = 0;
int pass = 0;
bool is_thp = false;
struct page *page;
struct page *page2;
int swapwrite = current->flags & PF_SWAPWRITE;
int rc, nr_subpages;
LIST_HEAD(ret_pages);
bool nosplit = (reason == MR_NUMA_MISPLACED);
trace_mm_migrate_pages_start(mode, reason);
if (!swapwrite)
current->flags |= PF_SWAPWRITE;
for (pass = 0; pass < 10 && (retry || thp_retry); pass++) {
retry = 0;
thp_retry = 0;
list_for_each_entry_safe(page, page2, from, lru) {
retry:
/*
* THP statistics is based on the source huge page.
* Capture required information that might get lost
* during migration.
*/
is_thp = PageTransHuge(page) && !PageHuge(page);
nr_subpages = thp_nr_pages(page);
cond_resched();
if (PageHuge(page))
rc = unmap_and_move_huge_page(get_new_page,
put_new_page, private, page,
pass > 2, mode, reason,
&ret_pages);
else
rc = unmap_and_move(get_new_page, put_new_page,
private, page, pass > 2, mode,
reason, &ret_pages);
/*
* The rules are:
* Success: non hugetlb page will be freed, hugetlb
* page will be put back
* -EAGAIN: stay on the from list
* -ENOMEM: stay on the from list
* Other errno: put on ret_pages list then splice to
* from list
*/
switch(rc) {
/*
* THP migration might be unsupported or the
* allocation could've failed so we should
* retry on the same page with the THP split
* to base pages.
*
* Head page is retried immediately and tail
* pages are added to the tail of the list so
* we encounter them after the rest of the list
* is processed.
*/
case -ENOSYS:
/* THP migration is unsupported */
if (is_thp) {
if (!try_split_thp(page, &page2, from)) {
nr_thp_split++;
goto retry;
}
nr_thp_failed++;
nr_failed += nr_subpages;
break;
}
/* Hugetlb migration is unsupported */
nr_failed++;
break;
case -ENOMEM:
/*
* When memory is low, don't bother to try to migrate
* other pages, just exit.
* THP NUMA faulting doesn't split THP to retry.
*/
if (is_thp && !nosplit) {
if (!try_split_thp(page, &page2, from)) {
nr_thp_split++;
goto retry;
}
nr_thp_failed++;
nr_failed += nr_subpages;
goto out;
}
nr_failed++;
goto out;
case -EAGAIN:
if (is_thp) {
thp_retry++;
break;
}
retry++;
break;
case MIGRATEPAGE_SUCCESS:
if (is_thp) {
nr_thp_succeeded++;
nr_succeeded += nr_subpages;
break;
}
nr_succeeded++;
break;
default:
/*
* Permanent failure (-EBUSY, etc.):
* unlike -EAGAIN case, the failed page is
* removed from migration page list and not
* retried in the next outer loop.
*/
if (is_thp) {
nr_thp_failed++;
nr_failed += nr_subpages;
break;
}
nr_failed++;
break;
}
}
}
nr_failed += retry + thp_retry;
nr_thp_failed += thp_retry;
rc = nr_failed;
out:
/*
* Put the permanent failure page back to migration list, they
* will be put back to the right list by the caller.
*/
list_splice(&ret_pages, from);
count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
count_vm_events(PGMIGRATE_FAIL, nr_failed);
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, nr_thp_succeeded,
nr_thp_failed, nr_thp_split, mode, reason);
if (!swapwrite)
current->flags &= ~PF_SWAPWRITE;
if (ret_succeeded)
*ret_succeeded = nr_succeeded;
return rc;
}
struct page *alloc_migration_target(struct page *page, unsigned long private)
{
struct migration_target_control *mtc;
gfp_t gfp_mask;
unsigned int order = 0;
struct page *new_page = 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 = page_to_nid(page);
if (PageHuge(page)) {
struct hstate *h = page_hstate(compound_head(page));
gfp_mask = htlb_modify_alloc_mask(h, gfp_mask);
return alloc_huge_page_nodemask(h, nid, mtc->nmask, gfp_mask);
}
if (PageTransHuge(page)) {
/*
* clear __GFP_RECLAIM to make the migration callback
* consistent with regular THP allocations.
*/
gfp_mask &= ~__GFP_RECLAIM;
gfp_mask |= GFP_TRANSHUGE;
order = HPAGE_PMD_ORDER;
}
zidx = zone_idx(page_zone(page));
if (is_highmem_idx(zidx) || zidx == ZONE_MOVABLE)
gfp_mask |= __GFP_HIGHMEM;
new_page = __alloc_pages(gfp_mask, order, nid, mtc->nmask);
if (new_page && PageTransHuge(new_page))
prep_transhuge_page(new_page);
return new_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;
unsigned int follflags;
int err;
mmap_read_lock(mm);
err = -EFAULT;
vma = find_vma(mm, addr);
if (!vma || addr < vma->vm_start || !vma_migratable(vma))
goto out;
/* FOLL_DUMP to ignore special (like zero) pages */
follflags = FOLL_GET | FOLL_DUMP;
page = follow_page(vma, addr, follflags);
err = PTR_ERR(page);
if (IS_ERR(page))
goto out;
err = -ENOENT;
if (!page)
goto out;
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)) {
isolate_huge_page(page, pagelist);
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 - 1;
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;
}
/*
* 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)
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_DUMP);
err = PTR_ERR(page);
if (IS_ERR(page))
goto set_status;
err = page ? page_to_nid(page) : -ENOENT;
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 16
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;
chunk_nr = nr_pages;
if (chunk_nr > DO_PAGES_STAT_CHUNK_NR)
chunk_nr = 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 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 (!populated_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;
struct page *newpage;
newpage = __alloc_pages_node(nid,
(GFP_HIGHUSER_MOVABLE |
__GFP_THISNODE | __GFP_NOMEMALLOC |
__GFP_NORETRY | __GFP_NOWARN) &
~__GFP_RECLAIM, 0);
return newpage;
}
static struct page *alloc_misplaced_dst_page_thp(struct page *page,
unsigned long data)
{
int nid = (int) data;
struct page *newpage;
newpage = alloc_pages_node(nid, (GFP_TRANSHUGE_LIGHT | __GFP_THISNODE),
HPAGE_PMD_ORDER);
if (!newpage)
goto out;
prep_transhuge_page(newpage);
out:
return newpage;
}
static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
{
int page_lru;
int nr_pages = thp_nr_pages(page);
VM_BUG_ON_PAGE(compound_order(page) && !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))
return 0;
if (isolate_lru_page(page))
return 0;
page_lru = page_is_file_lru(page);
mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_lru,
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;
LIST_HEAD(migratepages);
new_page_t *new;
bool compound;
int nr_pages = thp_nr_pages(page);
/*
* PTE mapped THP or HugeTLB page can't reach here so the page could
* be either base page or THP. And it must be head page if it is
* THP.
*/
compound = PageTransHuge(page);
if (compound)
new = alloc_misplaced_dst_page_thp;
else
new = alloc_misplaced_dst_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, *new, NULL, node,
MIGRATE_ASYNC, MR_NUMA_MISPLACED, NULL);
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;
} else
count_vm_numa_events(NUMA_PAGE_MIGRATE, nr_pages);
BUG_ON(!list_empty(&migratepages));
return isolated;
out:
put_page(page);
return 0;
}
#endif /* CONFIG_NUMA_BALANCING */
#endif /* CONFIG_NUMA */
#ifdef CONFIG_DEVICE_PRIVATE
static int migrate_vma_collect_skip(unsigned long start,
unsigned long end,
struct mm_walk *walk)
{
struct migrate_vma *migrate = walk->private;
unsigned long addr;
for (addr = start; addr < end; addr += PAGE_SIZE) {
migrate->dst[migrate->npages] = 0;
migrate->src[migrate->npages++] = 0;
}
return 0;
}
static int migrate_vma_collect_hole(unsigned long start,
unsigned long end,
__always_unused int depth,
struct mm_walk *walk)
{
struct migrate_vma *migrate = walk->private;
unsigned long addr;
/* Only allow populating anonymous memory. */
if (!vma_is_anonymous(walk->vma))
return migrate_vma_collect_skip(start, end, walk);
for (addr = start; addr < end; addr += PAGE_SIZE) {
migrate->src[migrate->npages] = MIGRATE_PFN_MIGRATE;
migrate->dst[migrate->npages] = 0;
migrate->npages++;
migrate->cpages++;
}
return 0;
}
static int migrate_vma_collect_pmd(pmd_t *pmdp,
unsigned long start,
unsigned long end,
struct mm_walk *walk)
{
struct migrate_vma *migrate = walk->private;
struct vm_area_struct *vma = walk->vma;
struct mm_struct *mm = vma->vm_mm;
unsigned long addr = start, unmapped = 0;
spinlock_t *ptl;
pte_t *ptep;
again:
if (pmd_none(*pmdp))
return migrate_vma_collect_hole(start, end, -1, walk);
if (pmd_trans_huge(*pmdp)) {
struct page *page;
ptl = pmd_lock(mm, pmdp);
if (unlikely(!pmd_trans_huge(*pmdp))) {
spin_unlock(ptl);
goto again;
}
page = pmd_page(*pmdp);
if (is_huge_zero_page(page)) {
spin_unlock(ptl);
split_huge_pmd(vma, pmdp, addr);
if (pmd_trans_unstable(pmdp))
return migrate_vma_collect_skip(start, end,
walk);
} else {
int ret;
get_page(page);
spin_unlock(ptl);
if (unlikely(!trylock_page(page)))
return migrate_vma_collect_skip(start, end,
walk);
ret = split_huge_page(page);
unlock_page(page);
put_page(page);
if (ret)
return migrate_vma_collect_skip(start, end,
walk);
if (pmd_none(*pmdp))
return migrate_vma_collect_hole(start, end, -1,
walk);
}
}
if (unlikely(pmd_bad(*pmdp)))
return migrate_vma_collect_skip(start, end, walk);
ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
arch_enter_lazy_mmu_mode();
for (; addr < end; addr += PAGE_SIZE, ptep++) {
unsigned long mpfn = 0, pfn;
struct page *page;
swp_entry_t entry;
pte_t pte;
pte = *ptep;
if (pte_none(pte)) {
if (vma_is_anonymous(vma)) {
mpfn = MIGRATE_PFN_MIGRATE;
migrate->cpages++;
}
goto next;
}
if (!pte_present(pte)) {
/*
* Only care about unaddressable device page special
* page table entry. Other special swap entries are not
* migratable, and we ignore regular swapped page.
*/
entry = pte_to_swp_entry(pte);
if (!is_device_private_entry(entry))
goto next;
page = pfn_swap_entry_to_page(entry);
if (!(migrate->flags &
MIGRATE_VMA_SELECT_DEVICE_PRIVATE) ||
page->pgmap->owner != migrate->pgmap_owner)
goto next;
mpfn = migrate_pfn(page_to_pfn(page)) |
MIGRATE_PFN_MIGRATE;
if (is_writable_device_private_entry(entry))
mpfn |= MIGRATE_PFN_WRITE;
} else {
if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM))
goto next;
pfn = pte_pfn(pte);
if (is_zero_pfn(pfn)) {
mpfn = MIGRATE_PFN_MIGRATE;
migrate->cpages++;
goto next;
}
page = vm_normal_page(migrate->vma, addr, pte);
mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
}
/* FIXME support THP */
if (!page || !page->mapping || PageTransCompound(page)) {
mpfn = 0;
goto next;
}
/*
* By getting a reference on the page we pin it and that blocks
* any kind of migration. Side effect is that it "freezes" the
* pte.
*
* We drop this reference after isolating the page from the lru
* for non device page (device page are not on the lru and thus
* can't be dropped from it).
*/
get_page(page);
migrate->cpages++;
/*
* Optimize for the common case where page is only mapped once
* in one process. If we can lock the page, then we can safely
* set up a special migration page table entry now.
*/
if (trylock_page(page)) {
pte_t swp_pte;
mpfn |= MIGRATE_PFN_LOCKED;
ptep_get_and_clear(mm, addr, ptep);
/* Setup special migration page table entry */
if (mpfn & MIGRATE_PFN_WRITE)
entry = make_writable_migration_entry(
page_to_pfn(page));
else
entry = make_readable_migration_entry(
page_to_pfn(page));
swp_pte = swp_entry_to_pte(entry);
if (pte_present(pte)) {
if (pte_soft_dirty(pte))
swp_pte = pte_swp_mksoft_dirty(swp_pte);
if (pte_uffd_wp(pte))
swp_pte = pte_swp_mkuffd_wp(swp_pte);
} else {
if (pte_swp_soft_dirty(pte))
swp_pte = pte_swp_mksoft_dirty(swp_pte);
if (pte_swp_uffd_wp(pte))
swp_pte = pte_swp_mkuffd_wp(swp_pte);
}
set_pte_at(mm, addr, ptep, swp_pte);
/*
* This is like regular unmap: we remove the rmap and
* drop page refcount. Page won't be freed, as we took
* a reference just above.
*/
page_remove_rmap(page, false);
put_page(page);
if (pte_present(pte))
unmapped++;
}
next:
migrate->dst[migrate->npages] = 0;
migrate->src[migrate->npages++] = mpfn;
}
arch_leave_lazy_mmu_mode();
pte_unmap_unlock(ptep - 1, ptl);
/* Only flush the TLB if we actually modified any entries */
if (unmapped)
flush_tlb_range(walk->vma, start, end);
return 0;
}
static const struct mm_walk_ops migrate_vma_walk_ops = {
.pmd_entry = migrate_vma_collect_pmd,
.pte_hole = migrate_vma_collect_hole,
};
/*
* migrate_vma_collect() - collect pages over a range of virtual addresses
* @migrate: migrate struct containing all migration information
*
* This will walk the CPU page table. For each virtual address backed by a
* valid page, it updates the src array and takes a reference on the page, in
* order to pin the page until we lock it and unmap it.
*/
static void migrate_vma_collect(struct migrate_vma *migrate)
{
struct mmu_notifier_range range;
/*
* Note that the pgmap_owner is passed to the mmu notifier callback so
* that the registered device driver can skip invalidating device
* private page mappings that won't be migrated.
*/
mmu_notifier_range_init_owner(&range, MMU_NOTIFY_MIGRATE, 0,
migrate->vma, migrate->vma->vm_mm, migrate->start, migrate->end,
migrate->pgmap_owner);
mmu_notifier_invalidate_range_start(&range);
walk_page_range(migrate->vma->vm_mm, migrate->start, migrate->end,
&migrate_vma_walk_ops, migrate);
mmu_notifier_invalidate_range_end(&range);
migrate->end = migrate->start + (migrate->npages << PAGE_SHIFT);
}
/*
* migrate_vma_check_page() - check if page is pinned or not
* @page: struct page to check
*
* Pinned pages cannot be migrated. This is the same test as in
* migrate_page_move_mapping(), except that here we allow migration of a
* ZONE_DEVICE page.
*/
static bool migrate_vma_check_page(struct page *page)
{
/*
* One extra ref because caller holds an extra reference, either from
* isolate_lru_page() for a regular page, or migrate_vma_collect() for
* a device page.
*/
int extra = 1;
/*
* FIXME support THP (transparent huge page), it is bit more complex to
* check them than regular pages, because they can be mapped with a pmd
* or with a pte (split pte mapping).
*/
if (PageCompound(page))
return false;
/* Page from ZONE_DEVICE have one extra reference */
if (is_zone_device_page(page)) {
/*
* Private page can never be pin as they have no valid pte and
* GUP will fail for those. Yet if there is a pending migration
* a thread might try to wait on the pte migration entry and
* will bump the page reference count. Sadly there is no way to
* differentiate a regular pin from migration wait. Hence to
* avoid 2 racing thread trying to migrate back to CPU to enter
* infinite loop (one stopping migration because the other is
* waiting on pte migration entry). We always return true here.
*
* FIXME proper solution is to rework migration_entry_wait() so
* it does not need to take a reference on page.
*/
return is_device_private_page(page);
}
/* For file back page */
if (page_mapping(page))
extra += 1 + page_has_private(page);
if ((page_count(page) - extra) > page_mapcount(page))
return false;
return true;
}
/*
* migrate_vma_prepare() - lock pages and isolate them from the lru
* @migrate: migrate struct containing all migration information
*
* This locks pages that have been collected by migrate_vma_collect(). Once each
* page is locked it is isolated from the lru (for non-device pages). Finally,
* the ref taken by migrate_vma_collect() is dropped, as locked pages cannot be
* migrated by concurrent kernel threads.
*/
static void migrate_vma_prepare(struct migrate_vma *migrate)
{
const unsigned long npages = migrate->npages;
const unsigned long start = migrate->start;
unsigned long addr, i, restore = 0;
bool allow_drain = true;
lru_add_drain();
for (i = 0; (i < npages) && migrate->cpages; i++) {
struct page *page = migrate_pfn_to_page(migrate->src[i]);
bool remap = true;
if (!page)
continue;
if (!(migrate->src[i] & MIGRATE_PFN_LOCKED)) {
/*
* Because we are migrating several pages there can be
* a deadlock between 2 concurrent migration where each
* are waiting on each other page lock.
*
* Make migrate_vma() a best effort thing and backoff
* for any page we can not lock right away.
*/
if (!trylock_page(page)) {
migrate->src[i] = 0;
migrate->cpages--;
put_page(page);
continue;
}
remap = false;
migrate->src[i] |= MIGRATE_PFN_LOCKED;
}
/* ZONE_DEVICE pages are not on LRU */
if (!is_zone_device_page(page)) {
if (!PageLRU(page) && allow_drain) {
/* Drain CPU's pagevec */
lru_add_drain_all();
allow_drain = false;
}
if (isolate_lru_page(page)) {
if (remap) {
migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
migrate->cpages--;
restore++;
} else {
migrate->src[i] = 0;
unlock_page(page);
migrate->cpages--;
put_page(page);
}
continue;
}
/* Drop the reference we took in collect */
put_page(page);
}
if (!migrate_vma_check_page(page)) {
if (remap) {
migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
migrate->cpages--;
restore++;
if (!is_zone_device_page(page)) {
get_page(page);
putback_lru_page(page);
}
} else {
migrate->src[i] = 0;
unlock_page(page);
migrate->cpages--;
if (!is_zone_device_page(page))
putback_lru_page(page);
else
put_page(page);
}
}
}
for (i = 0, addr = start; i < npages && restore; i++, addr += PAGE_SIZE) {
struct page *page = migrate_pfn_to_page(migrate->src[i]);
if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE))
continue;
remove_migration_pte(page, migrate->vma, addr, page);
migrate->src[i] = 0;
unlock_page(page);
put_page(page);
restore--;
}
}
/*
* migrate_vma_unmap() - replace page mapping with special migration pte entry
* @migrate: migrate struct containing all migration information
*
* Replace page mapping (CPU page table pte) with a special migration pte entry
* and check again if it has been pinned. Pinned pages are restored because we
* cannot migrate them.
*
* This is the last step before we call the device driver callback to allocate
* destination memory and copy contents of original page over to new page.
*/
static void migrate_vma_unmap(struct migrate_vma *migrate)
{
const unsigned long npages = migrate->npages;
const unsigned long start = migrate->start;
unsigned long addr, i, restore = 0;
for (i = 0; i < npages; i++) {
struct page *page = migrate_pfn_to_page(migrate->src[i]);
if (!page || !(migrate->src[i] & MIGRATE_PFN_MIGRATE))
continue;
if (page_mapped(page)) {
try_to_migrate(page, 0);
if (page_mapped(page))
goto restore;
}
if (migrate_vma_check_page(page))
continue;
restore:
migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
migrate->cpages--;
restore++;
}
for (addr = start, i = 0; i < npages && restore; addr += PAGE_SIZE, i++) {
struct page *page = migrate_pfn_to_page(migrate->src[i]);
if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE))
continue;
remove_migration_ptes(page, page, false);
migrate->src[i] = 0;
unlock_page(page);
restore--;
if (is_zone_device_page(page))
put_page(page);
else
putback_lru_page(page);
}
}
/**
* migrate_vma_setup() - prepare to migrate a range of memory
* @args: contains the vma, start, and pfns arrays for the migration
*
* Returns: negative errno on failures, 0 when 0 or more pages were migrated
* without an error.
*
* Prepare to migrate a range of memory virtual address range by collecting all
* the pages backing each virtual address in the range, saving them inside the
* src array. Then lock those pages and unmap them. Once the pages are locked
* and unmapped, check whether each page is pinned or not. Pages that aren't
* pinned have the MIGRATE_PFN_MIGRATE flag set (by this function) in the
* corresponding src array entry. Then restores any pages that are pinned, by
* remapping and unlocking those pages.
*
* The caller should then allocate destination memory and copy source memory to
* it for all those entries (ie with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE
* flag set). Once these are allocated and copied, the caller must update each
* corresponding entry in the dst array with the pfn value of the destination
* page and with the MIGRATE_PFN_VALID and MIGRATE_PFN_LOCKED flags set
* (destination pages must have their struct pages locked, via lock_page()).
*
* Note that the caller does not have to migrate all the pages that are marked
* with MIGRATE_PFN_MIGRATE flag in src array unless this is a migration from
* device memory to system memory. If the caller cannot migrate a device page
* back to system memory, then it must return VM_FAULT_SIGBUS, which has severe
* consequences for the userspace process, so it must be avoided if at all
* possible.
*
* For empty entries inside CPU page table (pte_none() or pmd_none() is true) we
* do set MIGRATE_PFN_MIGRATE flag inside the corresponding source array thus
* allowing the caller to allocate device memory for those unbacked virtual
* addresses. For this the caller simply has to allocate device memory and
* properly set the destination entry like for regular migration. Note that
* this can still fail, and thus inside the device driver you must check if the
* migration was successful for those entries after calling migrate_vma_pages(),
* just like for regular migration.
*
* After that, the callers must call migrate_vma_pages() to go over each entry
* in the src array that has the MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag
* set. If the corresponding entry in dst array has MIGRATE_PFN_VALID flag set,
* then migrate_vma_pages() to migrate struct page information from the source
* struct page to the destination struct page. If it fails to migrate the
* struct page information, then it clears the MIGRATE_PFN_MIGRATE flag in the
* src array.
*
* At this point all successfully migrated pages have an entry in the src
* array with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag set and the dst
* array entry with MIGRATE_PFN_VALID flag set.
*
* Once migrate_vma_pages() returns the caller may inspect which pages were
* successfully migrated, and which were not. Successfully migrated pages will
* have the MIGRATE_PFN_MIGRATE flag set for their src array entry.
*
* It is safe to update device page table after migrate_vma_pages() because
* both destination and source page are still locked, and the mmap_lock is held
* in read mode (hence no one can unmap the range being migrated).
*
* Once the caller is done cleaning up things and updating its page table (if it
* chose to do so, this is not an obligation) it finally calls
* migrate_vma_finalize() to update the CPU page table to point to new pages
* for successfully migrated pages or otherwise restore the CPU page table to
* point to the original source pages.
*/
int migrate_vma_setup(struct migrate_vma *args)
{
long nr_pages = (args->end - args->start) >> PAGE_SHIFT;
args->start &= PAGE_MASK;
args->end &= PAGE_MASK;
if (!args->vma || is_vm_hugetlb_page(args->vma) ||
(args->vma->vm_flags & VM_SPECIAL) || vma_is_dax(args->vma))
return -EINVAL;
if (nr_pages <= 0)
return -EINVAL;
if (args->start < args->vma->vm_start ||
args->start >= args->vma->vm_end)
return -EINVAL;
if (args->end <= args->vma->vm_start || args->end > args->vma->vm_end)
return -EINVAL;
if (!args->src || !args->dst)
return -EINVAL;
memset(args->src, 0, sizeof(*args->src) * nr_pages);
args->cpages = 0;
args->npages = 0;
migrate_vma_collect(args);
if (args->cpages)
migrate_vma_prepare(args);
if (args->cpages)
migrate_vma_unmap(args);
/*
* At this point pages are locked and unmapped, and thus they have
* stable content and can safely be copied to destination memory that
* is allocated by the drivers.
*/
return 0;
}
EXPORT_SYMBOL(migrate_vma_setup);
/*
* This code closely matches the code in:
* __handle_mm_fault()
* handle_pte_fault()
* do_anonymous_page()
* to map in an anonymous zero page but the struct page will be a ZONE_DEVICE
* private page.
*/
static void migrate_vma_insert_page(struct migrate_vma *migrate,
unsigned long addr,
struct page *page,
unsigned long *src)
{
struct vm_area_struct *vma = migrate->vma;
struct mm_struct *mm = vma->vm_mm;
bool flush = false;
spinlock_t *ptl;
pte_t entry;
pgd_t *pgdp;
p4d_t *p4dp;
pud_t *pudp;
pmd_t *pmdp;
pte_t *ptep;
/* Only allow populating anonymous memory */
if (!vma_is_anonymous(vma))
goto abort;
pgdp = pgd_offset(mm, addr);
p4dp = p4d_alloc(mm, pgdp, addr);
if (!p4dp)
goto abort;
pudp = pud_alloc(mm, p4dp, addr);
if (!pudp)
goto abort;
pmdp = pmd_alloc(mm, pudp, addr);
if (!pmdp)
goto abort;
if (pmd_trans_huge(*pmdp) || pmd_devmap(*pmdp))
goto abort;
/*
* Use pte_alloc() instead of pte_alloc_map(). We can't run
* pte_offset_map() on pmds where a huge pmd might be created
* from a different thread.
*
* pte_alloc_map() is safe to use under mmap_write_lock(mm) or when
* parallel threads are excluded by other means.
*
* Here we only have mmap_read_lock(mm).
*/
if (pte_alloc(mm, pmdp))
goto abort;
/* See the comment in pte_alloc_one_map() */
if (unlikely(pmd_trans_unstable(pmdp)))
goto abort;
if (unlikely(anon_vma_prepare(vma)))
goto abort;
if (mem_cgroup_charge(page, vma->vm_mm, GFP_KERNEL))
goto abort;
/*
* The memory barrier inside __SetPageUptodate makes sure that
* preceding stores to the page contents become visible before
* the set_pte_at() write.
*/
__SetPageUptodate(page);
if (is_zone_device_page(page)) {
if (is_device_private_page(page)) {
swp_entry_t swp_entry;
if (vma->vm_flags & VM_WRITE)
swp_entry = make_writable_device_private_entry(
page_to_pfn(page));
else
swp_entry = make_readable_device_private_entry(
page_to_pfn(page));
entry = swp_entry_to_pte(swp_entry);
} else {
/*
* For now we only support migrating to un-addressable
* device memory.
*/
pr_warn_once("Unsupported ZONE_DEVICE page type.\n");
goto abort;
}
} else {
entry = mk_pte(page, vma->vm_page_prot);
if (vma->vm_flags & VM_WRITE)
entry = pte_mkwrite(pte_mkdirty(entry));
}
ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
if (check_stable_address_space(mm))
goto unlock_abort;
if (pte_present(*ptep)) {
unsigned long pfn = pte_pfn(*ptep);
if (!is_zero_pfn(pfn))
goto unlock_abort;
flush = true;
} else if (!pte_none(*ptep))
goto unlock_abort;
/*
* Check for userfaultfd but do not deliver the fault. Instead,
* just back off.
*/
if (userfaultfd_missing(vma))
goto unlock_abort;
inc_mm_counter(mm, MM_ANONPAGES);
page_add_new_anon_rmap(page, vma, addr, false);
if (!is_zone_device_page(page))
lru_cache_add_inactive_or_unevictable(page, vma);
get_page(page);
if (flush) {
flush_cache_page(vma, addr, pte_pfn(*ptep));
ptep_clear_flush_notify(vma, addr, ptep);
set_pte_at_notify(mm, addr, ptep, entry);
update_mmu_cache(vma, addr, ptep);
} else {
/* No need to invalidate - it was non-present before */
set_pte_at(mm, addr, ptep, entry);
update_mmu_cache(vma, addr, ptep);
}
pte_unmap_unlock(ptep, ptl);
*src = MIGRATE_PFN_MIGRATE;
return;
unlock_abort:
pte_unmap_unlock(ptep, ptl);
abort:
*src &= ~MIGRATE_PFN_MIGRATE;
}
/**
* migrate_vma_pages() - migrate meta-data from src page to dst page
* @migrate: migrate struct containing all migration information
*
* This migrates struct page meta-data from source struct page to destination
* struct page. This effectively finishes the migration from source page to the
* destination page.
*/
void migrate_vma_pages(struct migrate_vma *migrate)
{
const unsigned long npages = migrate->npages;
const unsigned long start = migrate->start;
struct mmu_notifier_range range;
unsigned long addr, i;
bool notified = false;
for (i = 0, addr = start; i < npages; addr += PAGE_SIZE, i++) {
struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
struct page *page = migrate_pfn_to_page(migrate->src[i]);
struct address_space *mapping;
int r;
if (!newpage) {
migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
continue;
}
if (!page) {
if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE))
continue;
if (!notified) {
notified = true;
mmu_notifier_range_init_owner(&range,
MMU_NOTIFY_MIGRATE, 0, migrate->vma,
migrate->vma->vm_mm, addr, migrate->end,
migrate->pgmap_owner);
mmu_notifier_invalidate_range_start(&range);
}
migrate_vma_insert_page(migrate, addr, newpage,
&migrate->src[i]);
continue;
}
mapping = page_mapping(page);
if (is_zone_device_page(newpage)) {
if (is_device_private_page(newpage)) {
/*
* For now only support private anonymous when
* migrating to un-addressable device memory.
*/
if (mapping) {
migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
continue;
}
} else {
/*
* Other types of ZONE_DEVICE page are not
* supported.
*/
migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
continue;
}
}
r = migrate_page(mapping, newpage, page, MIGRATE_SYNC_NO_COPY);
if (r != MIGRATEPAGE_SUCCESS)
migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
}
/*
* No need to double call mmu_notifier->invalidate_range() callback as
* the above ptep_clear_flush_notify() inside migrate_vma_insert_page()
* did already call it.
*/
if (notified)
mmu_notifier_invalidate_range_only_end(&range);
}
EXPORT_SYMBOL(migrate_vma_pages);
/**
* migrate_vma_finalize() - restore CPU page table entry
* @migrate: migrate struct containing all migration information
*
* This replaces the special migration pte entry with either a mapping to the
* new page if migration was successful for that page, or to the original page
* otherwise.
*
* This also unlocks the pages and puts them back on the lru, or drops the extra
* refcount, for device pages.
*/
void migrate_vma_finalize(struct migrate_vma *migrate)
{
const unsigned long npages = migrate->npages;
unsigned long i;
for (i = 0; i < npages; i++) {
struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
struct page *page = migrate_pfn_to_page(migrate->src[i]);
if (!page) {
if (newpage) {
unlock_page(newpage);
put_page(newpage);
}
continue;
}
if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE) || !newpage) {
if (newpage) {
unlock_page(newpage);
put_page(newpage);
}
newpage = page;
}
remove_migration_ptes(page, newpage, false);
unlock_page(page);
if (is_zone_device_page(page))
put_page(page);
else
putback_lru_page(page);
if (newpage != page) {
unlock_page(newpage);
if (is_zone_device_page(newpage))
put_page(newpage);
else
putback_lru_page(newpage);
}
}
}
EXPORT_SYMBOL(migrate_vma_finalize);
#endif /* CONFIG_DEVICE_PRIVATE */
#if defined(CONFIG_MEMORY_HOTPLUG)
/* Disable reclaim-based migration. */
static void __disable_all_migrate_targets(void)
{
int node;
for_each_online_node(node)
node_demotion[node] = NUMA_NO_NODE;
}
static void disable_all_migrate_targets(void)
{
__disable_all_migrate_targets();
/*
* Ensure that the "disable" is visible across the system.
* Readers will see either a combination of before+disable
* state or disable+after. They will never see before and
* after state together.
*
* The before+after state together might have cycles and
* could cause readers to do things like loop until this
* function finishes. This ensures they can only see a
* single "bad" read and would, for instance, only loop
* once.
*/
synchronize_rcu();
}
/*
* Find an automatic demotion target for 'node'.
* Failing here is OK. It might just indicate
* being at the end of a chain.
*/
static int establish_migrate_target(int node, nodemask_t *used)
{
int migration_target;
/*
* Can not set a migration target on a
* node with it already set.
*
* No need for READ_ONCE() here since this
* in the write path for node_demotion[].
* This should be the only thread writing.
*/
if (node_demotion[node] != NUMA_NO_NODE)
return NUMA_NO_NODE;
migration_target = find_next_best_node(node, used);
if (migration_target == NUMA_NO_NODE)
return NUMA_NO_NODE;
node_demotion[node] = migration_target;
return migration_target;
}
/*
* When memory fills up on a node, memory contents can be
* automatically migrated to another node instead of
* discarded at reclaim.
*
* Establish a "migration path" which will start at nodes
* with CPUs and will follow the priorities used to build the
* page allocator zonelists.
*
* The difference here is that cycles must be avoided. If
* node0 migrates to node1, then neither node1, nor anything
* node1 migrates to can migrate to node0.
*
* This function can run simultaneously with readers of
* node_demotion[]. However, it can not run simultaneously
* with itself. Exclusion is provided by memory hotplug events
* being single-threaded.
*/
static void __set_migration_target_nodes(void)
{
nodemask_t next_pass = NODE_MASK_NONE;
nodemask_t this_pass = NODE_MASK_NONE;
nodemask_t used_targets = NODE_MASK_NONE;
int node;
/*
* Avoid any oddities like cycles that could occur
* from changes in the topology. This will leave
* a momentary gap when migration is disabled.
*/
disable_all_migrate_targets();
/*
* Allocations go close to CPUs, first. Assume that
* the migration path starts at the nodes with CPUs.
*/
next_pass = node_states[N_CPU];
again:
this_pass = next_pass;
next_pass = NODE_MASK_NONE;
/*
* To avoid cycles in the migration "graph", ensure
* that migration sources are not future targets by
* setting them in 'used_targets'. Do this only
* once per pass so that multiple source nodes can
* share a target node.
*
* 'used_targets' will become unavailable in future
* passes. This limits some opportunities for
* multiple source nodes to share a destination.
*/
nodes_or(used_targets, used_targets, this_pass);
for_each_node_mask(node, this_pass) {
int target_node = establish_migrate_target(node, &used_targets);
if (target_node == NUMA_NO_NODE)
continue;
/*
* Visit targets from this pass in the next pass.
* Eventually, every node will have been part of
* a pass, and will become set in 'used_targets'.
*/
node_set(target_node, next_pass);
}
/*
* 'next_pass' contains nodes which became migration
* targets in this pass. Make additional passes until
* no more migrations targets are available.
*/
if (!nodes_empty(next_pass))
goto again;
}
/*
* For callers that do not hold get_online_mems() already.
*/
static void set_migration_target_nodes(void)
{
get_online_mems();
__set_migration_target_nodes();
put_online_mems();
}
/*
* React to hotplug events that might affect the migration targets
* like events that online or offline NUMA nodes.
*
* The ordering is also currently dependent on which nodes have
* CPUs. That means we need CPU on/offline notification too.
*/
static int migration_online_cpu(unsigned int cpu)
{
set_migration_target_nodes();
return 0;
}
static int migration_offline_cpu(unsigned int cpu)
{
set_migration_target_nodes();
return 0;
}
/*
* This leaves migrate-on-reclaim transiently disabled between
* the MEM_GOING_OFFLINE and MEM_OFFLINE events. This runs
* whether reclaim-based migration is enabled or not, which
* ensures that the user can turn reclaim-based migration at
* any time without needing to recalculate migration targets.
*
* These callbacks already hold get_online_mems(). That is why
* __set_migration_target_nodes() can be used as opposed to
* set_migration_target_nodes().
*/
static int __meminit migrate_on_reclaim_callback(struct notifier_block *self,
unsigned long action, void *arg)
{
switch (action) {
case MEM_GOING_OFFLINE:
/*
* Make sure there are not transient states where
* an offline node is a migration target. This
* will leave migration disabled until the offline
* completes and the MEM_OFFLINE case below runs.
*/
disable_all_migrate_targets();
break;
case MEM_OFFLINE:
case MEM_ONLINE:
/*
* Recalculate the target nodes once the node
* reaches its final state (online or offline).
*/
__set_migration_target_nodes();
break;
case MEM_CANCEL_OFFLINE:
/*
* MEM_GOING_OFFLINE disabled all the migration
* targets. Reenable them.
*/
__set_migration_target_nodes();
break;
case MEM_GOING_ONLINE:
case MEM_CANCEL_ONLINE:
break;
}
return notifier_from_errno(0);
}
static int __init migrate_on_reclaim_init(void)
{
int ret;
ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "migrate on reclaim",
migration_online_cpu,
migration_offline_cpu);
/*
* In the unlikely case that this fails, the automatic
* migration targets may become suboptimal for nodes
* where N_CPU changes. With such a small impact in a
* rare case, do not bother trying to do anything special.
*/
WARN_ON(ret < 0);
hotplug_memory_notifier(migrate_on_reclaim_callback, 100);
return 0;
}
late_initcall(migrate_on_reclaim_init);
#endif /* CONFIG_MEMORY_HOTPLUG */
