blob: 4d0be47a322a8a33491c94072100ebcec829becd [file] [log] [blame]
// 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/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/mmu_notifier.h>
#include <linux/page_idle.h>
#include <linux/page_owner.h>
#include <linux/sched/mm.h>
#include <linux/ptrace.h>
#include <asm/tlbflush.h>
#define CREATE_TRACE_POINTS
#include <trace/events/migrate.h>
#include "internal.h"
/*
* migrate_prep() needs to be called before we start compiling a list of pages
* to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
* undesirable, use migrate_prep_local()
*/
int migrate_prep(void)
{
/*
* Clear the LRU lists so pages can be isolated.
* Note that pages may be moved off the LRU after we have
* drained them. Those pages will fail to migrate like other
* pages that may be busy.
*/
lru_add_drain_all();
return 0;
}
/* Do the necessary work of migrate_prep but not if it involves other CPUs */
int migrate_prep_local(void)
{
lru_add_drain();
return 0;
}
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 grapping 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;
}
/* It should be called on page which is PG_movable */
void putback_movable_page(struct page *page)
{
struct address_space *mapping;
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(!PageMovable(page), page);
VM_BUG_ON_PAGE(!PageIsolated(page), page);
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_cache(page), -hpage_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_write_migration_entry(entry))
pte = maybe_mkwrite(pte, vma);
if (unlikely(is_zone_device_page(new))) {
if (is_device_private_page(new)) {
entry = make_device_private_entry(new, pte_write(pte));
pte = swp_entry_to_pte(entry);
} else if (is_device_public_page(new)) {
pte = pte_mkdevmap(pte);
flush_dcache_page(new);
}
} else
flush_dcache_page(new);
#ifdef CONFIG_HUGETLB_PAGE
if (PageHuge(new)) {
pte = pte_mkhuge(pte);
pte = arch_make_huge_pte(pte, vma, new, 0);
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);
/* 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 = migration_entry_to_page(entry);
/*
* Once radix-tree replacement of page migration started, page_count
* *must* be zero. And, we don't want to call wait_on_page_locked()
* against a page without get_page().
* So, we use get_page_unless_zero(), here. Even failed, page fault
* will occur again.
*/
if (!get_page_unless_zero(page))
goto out;
pte_unmap_unlock(ptep, ptl);
wait_on_page_locked(page);
put_page(page);
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 = migration_entry_to_page(pmd_to_swp_entry(*pmd));
if (!get_page_unless_zero(page))
goto unlock;
spin_unlock(ptl);
wait_on_page_locked(page);
put_page(page);
return;
unlock:
spin_unlock(ptl);
}
#endif
#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 {
get_bh(bh);
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 {
get_bh(bh);
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;
put_bh(failed_bh);
bh = head;
while (bh != failed_bh) {
unlock_buffer(bh);
put_bh(bh);
bh = bh->b_this_page;
}
return false;
}
bh = bh->b_this_page;
} while (bh != head);
return true;
}
#else
static inline bool buffer_migrate_lock_buffers(struct buffer_head *head,
enum migrate_mode mode)
{
return true;
}
#endif /* CONFIG_BLOCK */
/*
* 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,
struct buffer_head *head, enum migrate_mode mode,
int extra_count)
{
struct zone *oldzone, *newzone;
int dirty;
int expected_count = 1 + extra_count;
void **pslot;
/*
* Device public or private pages have an extra refcount as they are
* ZONE_DEVICE pages.
*/
expected_count += is_device_private_page(page);
expected_count += is_device_public_page(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);
spin_lock_irq(&mapping->tree_lock);
pslot = radix_tree_lookup_slot(&mapping->page_tree,
page_index(page));
expected_count += 1 + page_has_private(page);
if (page_count(page) != expected_count ||
radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
spin_unlock_irq(&mapping->tree_lock);
return -EAGAIN;
}
if (!page_ref_freeze(page, expected_count)) {
spin_unlock_irq(&mapping->tree_lock);
return -EAGAIN;
}
/*
* In the async migration case of moving a page with buffers, lock the
* buffers using trylock before the mapping is moved. If the mapping
* was moved, we later failed to lock the buffers and could not move
* the mapping back due to an elevated page count, we would have to
* block waiting on other references to be dropped.
*/
if (mode == MIGRATE_ASYNC && head &&
!buffer_migrate_lock_buffers(head, mode)) {
page_ref_unfreeze(page, expected_count);
spin_unlock_irq(&mapping->tree_lock);
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;
get_page(newpage); /* 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);
}
radix_tree_replace_slot(&mapping->page_tree, pslot, 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 - 1);
spin_unlock(&mapping->tree_lock);
/* 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) {
__dec_node_state(oldzone->zone_pgdat, NR_FILE_PAGES);
__inc_node_state(newzone->zone_pgdat, NR_FILE_PAGES);
if (PageSwapBacked(page) && !PageSwapCache(page)) {
__dec_node_state(oldzone->zone_pgdat, NR_SHMEM);
__inc_node_state(newzone->zone_pgdat, NR_SHMEM);
}
if (dirty && mapping_cap_account_dirty(mapping)) {
__dec_node_state(oldzone->zone_pgdat, NR_FILE_DIRTY);
__dec_zone_state(oldzone, NR_ZONE_WRITE_PENDING);
__inc_node_state(newzone->zone_pgdat, NR_FILE_DIRTY);
__inc_zone_state(newzone, NR_ZONE_WRITE_PENDING);
}
}
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)
{
int expected_count;
void **pslot;
spin_lock_irq(&mapping->tree_lock);
pslot = radix_tree_lookup_slot(&mapping->page_tree,
page_index(page));
expected_count = 2 + page_has_private(page);
if (page_count(page) != expected_count ||
radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
spin_unlock_irq(&mapping->tree_lock);
return -EAGAIN;
}
if (!page_ref_freeze(page, expected_count)) {
spin_unlock_irq(&mapping->tree_lock);
return -EAGAIN;
}
newpage->index = page->index;
newpage->mapping = page->mapping;
get_page(newpage);
radix_tree_replace_slot(&mapping->page_tree, pslot, newpage);
page_ref_unfreeze(page, expected_count - 1);
spin_unlock_irq(&mapping->tree_lock);
return MIGRATEPAGE_SUCCESS;
}
/*
* Gigantic pages are so large that we do not guarantee that page++ pointer
* arithmetic will work across the entire page. We need something more
* specialized.
*/
static void __copy_gigantic_page(struct page *dst, struct page *src,
int nr_pages)
{
int i;
struct page *dst_base = dst;
struct page *src_base = src;
for (i = 0; i < nr_pages; ) {
cond_resched();
copy_highpage(dst, src);
i++;
dst = mem_map_next(dst, dst_base, i);
src = mem_map_next(src, src_base, i);
}
}
static void copy_huge_page(struct page *dst, struct page *src)
{
int i;
int nr_pages;
if (PageHuge(src)) {
/* hugetlbfs page */
struct hstate *h = page_hstate(src);
nr_pages = pages_per_huge_page(h);
if (unlikely(nr_pages > MAX_ORDER_NR_PAGES)) {
__copy_gigantic_page(dst, src, nr_pages);
return;
}
} else {
/* thp page */
BUG_ON(!PageTransHuge(src));
nr_pages = hpage_nr_pages(src);
}
for (i = 0; i < nr_pages; i++) {
cond_resched();
copy_highpage(dst + i, src + i);
}
}
/*
* 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 (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);
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);
copy_page_owner(page, newpage);
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, NULL, mode, 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
/*
* Migration function for pages with buffers. This function can only be used
* if the underlying filesystem guarantees that no other references to "page"
* exist.
*/
int buffer_migrate_page(struct address_space *mapping,
struct page *newpage, struct page *page, enum migrate_mode mode)
{
struct buffer_head *bh, *head;
int rc;
if (!page_has_buffers(page))
return migrate_page(mapping, newpage, page, mode);
head = page_buffers(page);
rc = migrate_page_move_mapping(mapping, newpage, page, head, mode, 0);
if (rc != MIGRATEPAGE_SUCCESS)
return rc;
/*
* In the async case, migrate_page_move_mapping locked the buffers
* with an IRQ-safe spinlock held. In the sync case, the buffers
* need to be locked now
*/
if (mode != MIGRATE_ASYNC)
BUG_ON(!buffer_migrate_lock_buffers(head, mode));
ClearPagePrivate(page);
set_page_private(newpage, page_private(page));
set_page_private(page, 0);
put_page(page);
get_page(newpage);
bh = head;
do {
set_bh_page(bh, newpage, bh_offset(bh));
bh = bh->b_this_page;
} while (bh != head);
SetPagePrivate(newpage);
if (mode != MIGRATE_SYNC_NO_COPY)
migrate_page_copy(newpage, page);
else
migrate_page_states(newpage, page);
bh = head;
do {
unlock_buffer(bh);
put_bh(bh);
bh = bh->b_this_page;
} while (bh != head);
return MIGRATEPAGE_SUCCESS;
}
EXPORT_SYMBOL(buffer_migrate_page);
#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 -EAGAIN;
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 cleard 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;
}
out:
return rc;
}
static int __unmap_and_move(struct page *page, struct page *newpage,
int force, enum migrate_mode mode)
{
int rc = -EAGAIN;
int page_was_mapped = 0;
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_readpages). 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_unmap(), 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_complete_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_unmap(page,
TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
page_was_mapped = 1;
}
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.
*/
if (rc == MIGRATEPAGE_SUCCESS) {
if (unlikely(__PageMovable(newpage)))
put_page(newpage);
else
putback_lru_page(newpage);
}
return rc;
}
/*
* gcc 4.7 and 4.8 on arm get an ICEs when inlining unmap_and_move(). Work
* around it.
*/
#if (GCC_VERSION >= 40700 && GCC_VERSION < 40900) && defined(CONFIG_ARM)
#define ICE_noinline noinline
#else
#define ICE_noinline
#endif
/*
* Obtain the lock on page, remove all ptes and migrate the page
* to the newly allocated page in newpage.
*/
static ICE_noinline 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)
{
int rc = MIGRATEPAGE_SUCCESS;
int *result = NULL;
struct page *newpage;
newpage = get_new_page(page, private, &result);
if (!newpage)
return -ENOMEM;
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);
}
if (put_new_page)
put_new_page(newpage, private);
else
put_page(newpage);
goto out;
}
if (unlikely(PageTransHuge(page) && !PageTransHuge(newpage))) {
lock_page(page);
rc = split_huge_page(page);
unlock_page(page);
if (rc)
goto out;
}
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 kepts its references and be
* restored.
*/
list_del(&page->lru);
/*
* 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_cache(page), -hpage_nr_pages(page));
}
/*
* 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) {
put_page(page);
if (reason == MR_MEMORY_FAILURE) {
/*
* Set PG_HWPoison on just freed page
* intentionally. Although it's rather weird,
* it's how HWPoison flag works at the moment.
*/
if (!test_set_page_hwpoison(page))
num_poisoned_pages_inc();
}
} else {
if (rc != -EAGAIN) {
if (likely(!__PageMovable(page))) {
putback_lru_page(page);
goto put_new;
}
lock_page(page);
if (PageMovable(page))
putback_movable_page(page);
else
__ClearPageIsolated(page);
unlock_page(page);
put_page(page);
}
put_new:
if (put_new_page)
put_new_page(newpage, private);
else
put_page(newpage);
}
if (result) {
if (rc)
*result = rc;
else
*result = page_to_nid(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)
{
int rc = -EAGAIN;
int *result = NULL;
int page_was_mapped = 0;
struct page *new_hpage;
struct anon_vma *anon_vma = NULL;
/*
* Movability of hugepages depends on architectures and hugepage 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))) {
putback_active_hugepage(hpage);
return -ENOSYS;
}
new_hpage = get_new_page(hpage, private, &result);
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);
}
if (PageAnon(hpage))
anon_vma = page_get_anon_vma(hpage);
if (unlikely(!trylock_page(new_hpage)))
goto put_anon;
if (page_mapped(hpage)) {
try_to_unmap(hpage,
TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
page_was_mapped = 1;
}
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_page(new_hpage);
put_anon:
if (anon_vma)
put_anon_vma(anon_vma);
if (rc == MIGRATEPAGE_SUCCESS) {
hugetlb_cgroup_migrate(hpage, new_hpage);
put_new_page = NULL;
set_page_owner_migrate_reason(new_hpage, reason);
}
unlock_page(hpage);
out:
if (rc != -EAGAIN)
putback_active_hugepage(hpage);
if (reason == MR_MEMORY_FAILURE && !test_set_page_hwpoison(hpage))
num_poisoned_pages_inc();
/*
* 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);
if (result) {
if (rc)
*result = rc;
else
*result = page_to_nid(new_hpage);
}
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.
*
* 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.
* The caller should 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)
{
int retry = 1;
int nr_failed = 0;
int nr_succeeded = 0;
int pass = 0;
struct page *page;
struct page *page2;
int swapwrite = current->flags & PF_SWAPWRITE;
int rc;
if (!swapwrite)
current->flags |= PF_SWAPWRITE;
for(pass = 0; pass < 10 && retry; pass++) {
retry = 0;
list_for_each_entry_safe(page, page2, from, lru) {
cond_resched();
if (PageHuge(page))
rc = unmap_and_move_huge_page(get_new_page,
put_new_page, private, page,
pass > 2, mode, reason);
else
rc = unmap_and_move(get_new_page, put_new_page,
private, page, pass > 2, mode,
reason);
switch(rc) {
case -ENOMEM:
nr_failed++;
goto out;
case -EAGAIN:
retry++;
break;
case MIGRATEPAGE_SUCCESS:
nr_succeeded++;
break;
default:
/*
* Permanent failure (-EBUSY, -ENOSYS, etc.):
* unlike -EAGAIN case, the failed page is
* removed from migration page list and not
* retried in the next outer loop.
*/
nr_failed++;
break;
}
}
}
nr_failed += retry;
rc = nr_failed;
out:
if (nr_succeeded)
count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
if (nr_failed)
count_vm_events(PGMIGRATE_FAIL, nr_failed);
trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason);
if (!swapwrite)
current->flags &= ~PF_SWAPWRITE;
return rc;
}
#ifdef CONFIG_NUMA
/*
* Move a list of individual pages
*/
struct page_to_node {
unsigned long addr;
struct page *page;
int node;
int status;
};
static struct page *new_page_node(struct page *p, unsigned long private,
int **result)
{
struct page_to_node *pm = (struct page_to_node *)private;
while (pm->node != MAX_NUMNODES && pm->page != p)
pm++;
if (pm->node == MAX_NUMNODES)
return NULL;
*result = &pm->status;
if (PageHuge(p))
return alloc_huge_page_node(page_hstate(compound_head(p)),
pm->node);
else if (thp_migration_supported() && PageTransHuge(p)) {
struct page *thp;
thp = alloc_pages_node(pm->node,
(GFP_TRANSHUGE | __GFP_THISNODE) & ~__GFP_RECLAIM,
HPAGE_PMD_ORDER);
if (!thp)
return NULL;
prep_transhuge_page(thp);
return thp;
} else
return __alloc_pages_node(pm->node,
GFP_HIGHUSER_MOVABLE | __GFP_THISNODE, 0);
}
/*
* Move a set of pages as indicated in the pm array. The addr
* field must be set to the virtual address of the page to be moved
* and the node number must contain a valid target node.
* The pm array ends with node = MAX_NUMNODES.
*/
static int do_move_page_to_node_array(struct mm_struct *mm,
struct page_to_node *pm,
int migrate_all)
{
int err;
struct page_to_node *pp;
LIST_HEAD(pagelist);
down_read(&mm->mmap_sem);
/*
* Build a list of pages to migrate
*/
for (pp = pm; pp->node != MAX_NUMNODES; pp++) {
struct vm_area_struct *vma;
struct page *page;
struct page *head;
unsigned int follflags;
err = -EFAULT;
vma = find_vma(mm, pp->addr);
if (!vma || pp->addr < vma->vm_start || !vma_migratable(vma))
goto set_status;
/* FOLL_DUMP to ignore special (like zero) pages */
follflags = FOLL_GET | FOLL_DUMP;
if (!thp_migration_supported())
follflags |= FOLL_SPLIT;
page = follow_page(vma, pp->addr, follflags);
err = PTR_ERR(page);
if (IS_ERR(page))
goto set_status;
err = -ENOENT;
if (!page)
goto set_status;
err = page_to_nid(page);
if (err == pp->node)
/*
* Node already in the right place
*/
goto put_and_set;
err = -EACCES;
if (page_mapcount(page) > 1 &&
!migrate_all)
goto put_and_set;
if (PageHuge(page)) {
if (PageHead(page)) {
isolate_huge_page(page, &pagelist);
err = 0;
pp->page = page;
}
goto put_and_set;
}
pp->page = compound_head(page);
head = compound_head(page);
err = isolate_lru_page(head);
if (!err) {
list_add_tail(&head->lru, &pagelist);
mod_node_page_state(page_pgdat(head),
NR_ISOLATED_ANON + page_is_file_cache(head),
hpage_nr_pages(head));
}
put_and_set:
/*
* Either remove the duplicate refcount from
* isolate_lru_page() or drop the page ref if it was
* not isolated.
*/
put_page(page);
set_status:
pp->status = err;
}
err = 0;
if (!list_empty(&pagelist)) {
err = migrate_pages(&pagelist, new_page_node, NULL,
(unsigned long)pm, MIGRATE_SYNC, MR_SYSCALL);
if (err)
putback_movable_pages(&pagelist);
}
up_read(&mm->mmap_sem);
return err;
}
/*
* 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)
{
struct page_to_node *pm;
unsigned long chunk_nr_pages;
unsigned long chunk_start;
int err;
err = -ENOMEM;
pm = (struct page_to_node *)__get_free_page(GFP_KERNEL);
if (!pm)
goto out;
migrate_prep();
/*
* Store a chunk of page_to_node array in a page,
* but keep the last one as a marker
*/
chunk_nr_pages = (PAGE_SIZE / sizeof(struct page_to_node)) - 1;
for (chunk_start = 0;
chunk_start < nr_pages;
chunk_start += chunk_nr_pages) {
int j;
if (chunk_start + chunk_nr_pages > nr_pages)
chunk_nr_pages = nr_pages - chunk_start;
/* fill the chunk pm with addrs and nodes from user-space */
for (j = 0; j < chunk_nr_pages; j++) {
const void __user *p;
int node;
err = -EFAULT;
if (get_user(p, pages + j + chunk_start))
goto out_pm;
pm[j].addr = (unsigned long) p;
if (get_user(node, nodes + j + chunk_start))
goto out_pm;
err = -ENODEV;
if (node < 0 || node >= MAX_NUMNODES)
goto out_pm;
if (!node_state(node, N_MEMORY))
goto out_pm;
err = -EACCES;
if (!node_isset(node, task_nodes))
goto out_pm;
pm[j].node = node;
}
/* End marker for this chunk */
pm[chunk_nr_pages].node = MAX_NUMNODES;
/* Migrate this chunk */
err = do_move_page_to_node_array(mm, pm,
flags & MPOL_MF_MOVE_ALL);
if (err < 0)
goto out_pm;
/* Return status information */
for (j = 0; j < chunk_nr_pages; j++)
if (put_user(pm[j].status, status + j + chunk_start)) {
err = -EFAULT;
goto out_pm;
}
}
err = 0;
out_pm:
free_page((unsigned long)pm);
out:
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;
down_read(&mm->mmap_sem);
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 = find_vma(mm, addr);
if (!vma || addr < vma->vm_start)
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++;
}
up_read(&mm->mmap_sem);
}
/*
* 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 (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;
}
/*
* Move a list of pages in the address space of the currently executing
* process.
*/
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)
{
struct task_struct *task;
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;
/* Find the mm_struct */
rcu_read_lock();
task = pid ? find_task_by_vpid(pid) : current;
if (!task) {
rcu_read_unlock();
return -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();
err = -EPERM;
goto out;
}
rcu_read_unlock();
err = security_task_movememory(task);
if (err)
goto out;
task_nodes = cpuset_mems_allowed(task);
mm = get_task_mm(task);
put_task_struct(task);
if (!mm)
return -EINVAL;
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;
out:
put_task_struct(task);
return err;
}
#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,
0, 0))
continue;
return true;
}
return false;
}
static struct page *alloc_misplaced_dst_page(struct page *page,
unsigned long data,
int **result)
{
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;
}
/*
* page migration rate limiting control.
* Do not migrate more than @pages_to_migrate in a @migrate_interval_millisecs
* window of time. Default here says do not migrate more than 1280M per second.
*/
static unsigned int migrate_interval_millisecs __read_mostly = 100;
static unsigned int ratelimit_pages __read_mostly = 128 << (20 - PAGE_SHIFT);
/* Returns true if the node is migrate rate-limited after the update */
static bool numamigrate_update_ratelimit(pg_data_t *pgdat,
unsigned long nr_pages)
{
/*
* Rate-limit the amount of data that is being migrated to a node.
* Optimal placement is no good if the memory bus is saturated and
* all the time is being spent migrating!
*/
if (time_after(jiffies, pgdat->numabalancing_migrate_next_window)) {
spin_lock(&pgdat->numabalancing_migrate_lock);
pgdat->numabalancing_migrate_nr_pages = 0;
pgdat->numabalancing_migrate_next_window = jiffies +
msecs_to_jiffies(migrate_interval_millisecs);
spin_unlock(&pgdat->numabalancing_migrate_lock);
}
if (pgdat->numabalancing_migrate_nr_pages > ratelimit_pages) {
trace_mm_numa_migrate_ratelimit(current, pgdat->node_id,
nr_pages);
return true;
}
/*
* This is an unlocked non-atomic update so errors are possible.
* The consequences are failing to migrate when we potentiall should
* have which is not severe enough to warrant locking. If it is ever
* a problem, it can be converted to a per-cpu counter.
*/
pgdat->numabalancing_migrate_nr_pages += nr_pages;
return false;
}
static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
{
int page_lru;
VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page);
/* Avoid migrating to a node that is nearly full */
if (!migrate_balanced_pgdat(pgdat, 1UL << compound_order(page)))
return 0;
if (isolate_lru_page(page))
return 0;
/*
* migrate_misplaced_transhuge_page() skips page migration's usual
* check on page_count(), so we must do it here, now that the page
* has been isolated: a GUP pin, or any other pin, prevents migration.
* The expected page count is 3: 1 for page's mapcount and 1 for the
* caller's pin and 1 for the reference taken by isolate_lru_page().
*/
if (PageTransHuge(page) && page_count(page) != 3) {
putback_lru_page(page);
return 0;
}
page_lru = page_is_file_cache(page);
mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_lru,
hpage_nr_pages(page));
/*
* 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;
}
bool pmd_trans_migrating(pmd_t pmd)
{
struct page *page = pmd_page(pmd);
return PageLocked(page);
}
/*
* 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);
/*
* 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_cache(page) &&
(vma->vm_flags & VM_EXEC))
goto out;
/*
* Rate-limit the amount of data that is being migrated to a node.
* Optimal placement is no good if the memory bus is saturated and
* all the time is being spent migrating!
*/
if (numamigrate_update_ratelimit(pgdat, 1))
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);
if (nr_remaining) {
if (!list_empty(&migratepages)) {
list_del(&page->lru);
dec_node_page_state(page, NR_ISOLATED_ANON +
page_is_file_cache(page));
putback_lru_page(page);
}
isolated = 0;
} else
count_vm_numa_event(NUMA_PAGE_MIGRATE);
BUG_ON(!list_empty(&migratepages));
return isolated;
out:
put_page(page);
return 0;
}
#endif /* CONFIG_NUMA_BALANCING */
#if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
/*
* Migrates a THP to a given target node. page must be locked and is unlocked
* before returning.
*/
int migrate_misplaced_transhuge_page(struct mm_struct *mm,
struct vm_area_struct *vma,
pmd_t *pmd, pmd_t entry,
unsigned long address,
struct page *page, int node)
{
spinlock_t *ptl;
pg_data_t *pgdat = NODE_DATA(node);
int isolated = 0;
struct page *new_page = NULL;
int page_lru = page_is_file_cache(page);
unsigned long mmun_start = address & HPAGE_PMD_MASK;
unsigned long mmun_end = mmun_start + HPAGE_PMD_SIZE;
/*
* Rate-limit the amount of data that is being migrated to a node.
* Optimal placement is no good if the memory bus is saturated and
* all the time is being spent migrating!
*/
if (numamigrate_update_ratelimit(pgdat, HPAGE_PMD_NR))
goto out_dropref;
new_page = alloc_pages_node(node,
(GFP_TRANSHUGE_LIGHT | __GFP_THISNODE),
HPAGE_PMD_ORDER);
if (!new_page)
goto out_fail;
prep_transhuge_page(new_page);
isolated = numamigrate_isolate_page(pgdat, page);
if (!isolated) {
put_page(new_page);
goto out_fail;
}
/* Prepare a page as a migration target */
__SetPageLocked(new_page);
if (PageSwapBacked(page))
__SetPageSwapBacked(new_page);
/* anon mapping, we can simply copy page->mapping to the new page: */
new_page->mapping = page->mapping;
new_page->index = page->index;
migrate_page_copy(new_page, page);
WARN_ON(PageLRU(new_page));
/* Recheck the target PMD */
mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
ptl = pmd_lock(mm, pmd);
if (unlikely(!pmd_same(*pmd, entry) || !page_ref_freeze(page, 2))) {
spin_unlock(ptl);
mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
/* Reverse changes made by migrate_page_copy() */
if (TestClearPageActive(new_page))
SetPageActive(page);
if (TestClearPageUnevictable(new_page))
SetPageUnevictable(page);
unlock_page(new_page);
put_page(new_page); /* Free it */
/* Retake the callers reference and putback on LRU */
get_page(page);
putback_lru_page(page);
mod_node_page_state(page_pgdat(page),
NR_ISOLATED_ANON + page_lru, -HPAGE_PMD_NR);
goto out_unlock;
}
entry = mk_huge_pmd(new_page, vma->vm_page_prot);
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
/*
* Clear the old entry under pagetable lock and establish the new PTE.
* Any parallel GUP will either observe the old page blocking on the
* page lock, block on the page table lock or observe the new page.
* The SetPageUptodate on the new page and page_add_new_anon_rmap
* guarantee the copy is visible before the pagetable update.
*/
flush_cache_range(vma, mmun_start, mmun_end);
page_add_anon_rmap(new_page, vma, mmun_start, true);
pmdp_huge_clear_flush_notify(vma, mmun_start, pmd);
set_pmd_at(mm, mmun_start, pmd, entry);
update_mmu_cache_pmd(vma, address, &entry);
page_ref_unfreeze(page, 2);
mlock_migrate_page(new_page, page);
page_remove_rmap(page, true);
set_page_owner_migrate_reason(new_page, MR_NUMA_MISPLACED);
spin_unlock(ptl);
/*
* No need to double call mmu_notifier->invalidate_range() callback as
* the above pmdp_huge_clear_flush_notify() did already call it.
*/
mmu_notifier_invalidate_range_only_end(mm, mmun_start, mmun_end);
/* Take an "isolate" reference and put new page on the LRU. */
get_page(new_page);
putback_lru_page(new_page);
unlock_page(new_page);
unlock_page(page);
put_page(page); /* Drop the rmap reference */
put_page(page); /* Drop the LRU isolation reference */
count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR);
count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR);
mod_node_page_state(page_pgdat(page),
NR_ISOLATED_ANON + page_lru,
-HPAGE_PMD_NR);
return isolated;
out_fail:
count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
out_dropref:
ptl = pmd_lock(mm, pmd);
if (pmd_same(*pmd, entry)) {
entry = pmd_modify(entry, vma->vm_page_prot);
set_pmd_at(mm, mmun_start, pmd, entry);
update_mmu_cache_pmd(vma, address, &entry);
}
spin_unlock(ptl);
out_unlock:
unlock_page(page);
put_page(page);
return 0;
}
#endif /* CONFIG_NUMA_BALANCING */
#endif /* CONFIG_NUMA */
#if defined(CONFIG_MIGRATE_VMA_HELPER)
struct migrate_vma {
struct vm_area_struct *vma;
unsigned long *dst;
unsigned long *src;
unsigned long cpages;
unsigned long npages;
unsigned long start;
unsigned long end;
};
static int migrate_vma_collect_hole(unsigned long start,
unsigned long end,
struct mm_walk *walk)
{
struct migrate_vma *migrate = walk->private;
unsigned long addr;
for (addr = start & PAGE_MASK; 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_skip(unsigned long start,
unsigned long end,
struct mm_walk *walk)
{
struct migrate_vma *migrate = walk->private;
unsigned long addr;
for (addr = start & PAGE_MASK; addr < end; addr += PAGE_SIZE) {
migrate->dst[migrate->npages] = 0;
migrate->src[migrate->npages++] = 0;
}
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, 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,
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, pfn;
struct page *page;
swp_entry_t entry;
pte_t pte;
pte = *ptep;
pfn = pte_pfn(pte);
if (pte_none(pte)) {
mpfn = MIGRATE_PFN_MIGRATE;
migrate->cpages++;
pfn = 0;
goto next;
}
if (!pte_present(pte)) {
mpfn = pfn = 0;
/*
* 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 = device_private_entry_to_page(entry);
mpfn = migrate_pfn(page_to_pfn(page))|
MIGRATE_PFN_DEVICE | MIGRATE_PFN_MIGRATE;
if (is_write_device_private_entry(entry))
mpfn |= MIGRATE_PFN_WRITE;
} else {
if (is_zero_pfn(pfn)) {
mpfn = MIGRATE_PFN_MIGRATE;
migrate->cpages++;
pfn = 0;
goto next;
}
page = _vm_normal_page(migrate->vma, addr, pte, true);
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 = pfn = 0;
goto next;
}
pfn = page_to_pfn(page);
/*
* 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 */
entry = make_migration_entry(page, pte_write(pte));
swp_pte = swp_entry_to_pte(entry);
if (pte_soft_dirty(pte))
swp_pte = pte_swp_mksoft_dirty(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;
}
/*
* 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 mm_walk mm_walk;
mm_walk.pmd_entry = migrate_vma_collect_pmd;
mm_walk.pte_entry = NULL;
mm_walk.pte_hole = migrate_vma_collect_hole;
mm_walk.hugetlb_entry = NULL;
mm_walk.test_walk = NULL;
mm_walk.vma = migrate->vma;
mm_walk.mm = migrate->vma->vm_mm;
mm_walk.private = migrate;
mmu_notifier_invalidate_range_start(mm_walk.mm,
migrate->start,
migrate->end);
walk_page_range(migrate->start, migrate->end, &mm_walk);
mmu_notifier_invalidate_range_end(mm_walk.mm,
migrate->start,
migrate->end);
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 stoping 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.
*/
if (is_device_private_page(page))
return true;
/*
* Only allow device public page to be migrated and account for
* the extra reference count imply by ZONE_DEVICE pages.
*/
if (!is_device_public_page(page))
return false;
extra++;
}
/* 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)
{
int flags = TTU_MIGRATION | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
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_unmap(page, flags);
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);
}
}
static void migrate_vma_insert_page(struct migrate_vma *migrate,
unsigned long addr,
struct page *page,
unsigned long *src,
unsigned long *dst)
{
struct vm_area_struct *vma = migrate->vma;
struct mm_struct *mm = vma->vm_mm;
struct mem_cgroup *memcg;
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 down_write(mmap_sem) or when
* parallel threads are excluded by other means.
*
* Here we only have down_read(mmap_sem).
*/
if (pte_alloc(mm, pmdp, addr))
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_try_charge(page, vma->vm_mm, GFP_KERNEL, &memcg, false))
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;
swp_entry = make_device_private_entry(page, vma->vm_flags & VM_WRITE);
entry = swp_entry_to_pte(swp_entry);
} else if (is_device_public_page(page)) {
entry = pte_mkold(mk_pte(page, READ_ONCE(vma->vm_page_prot)));
if (vma->vm_flags & VM_WRITE)
entry = pte_mkwrite(pte_mkdirty(entry));
entry = pte_mkdevmap(entry);
}
} 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 (pte_present(*ptep)) {
unsigned long pfn = pte_pfn(*ptep);
if (!is_zero_pfn(pfn)) {
pte_unmap_unlock(ptep, ptl);
mem_cgroup_cancel_charge(page, memcg, false);
goto abort;
}
flush = true;
} else if (!pte_none(*ptep)) {
pte_unmap_unlock(ptep, ptl);
mem_cgroup_cancel_charge(page, memcg, false);
goto abort;
}
/*
* Check for usefaultfd but do not deliver the fault. Instead,
* just back off.
*/
if (userfaultfd_missing(vma)) {
pte_unmap_unlock(ptep, ptl);
mem_cgroup_cancel_charge(page, memcg, false);
goto abort;
}
inc_mm_counter(mm, MM_ANONPAGES);
page_add_new_anon_rmap(page, vma, addr, false);
mem_cgroup_commit_charge(page, memcg, false, false);
if (!is_zone_device_page(page))
lru_cache_add_active_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;
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.
*/
static void migrate_vma_pages(struct migrate_vma *migrate)
{
const unsigned long npages = migrate->npages;
const unsigned long start = migrate->start;
struct vm_area_struct *vma = migrate->vma;
struct mm_struct *mm = vma->vm_mm;
unsigned long addr, i, mmu_start;
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) {
mmu_start = addr;
notified = true;
mmu_notifier_invalidate_range_start(mm,
mmu_start,
migrate->end);
}
migrate_vma_insert_page(migrate, addr, newpage,
&migrate->src[i],
&migrate->dst[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 if (!is_device_public_page(newpage)) {
/*
* 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(mm, mmu_start,
migrate->end);
}
/*
* 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.
*/
static 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);
migrate->cpages--;
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);
}
}
}
/*
* migrate_vma() - migrate a range of memory inside vma
*
* @ops: migration callback for allocating destination memory and copying
* @vma: virtual memory area containing the range to be migrated
* @start: start address of the range to migrate (inclusive)
* @end: end address of the range to migrate (exclusive)
* @src: array of hmm_pfn_t containing source pfns
* @dst: array of hmm_pfn_t containing destination pfns
* @private: pointer passed back to each of the callback
* Returns: 0 on success, error code otherwise
*
* This function tries to migrate a range of memory virtual address range, using
* callbacks to allocate and copy memory from source to destination. First it
* collects all the pages backing each virtual address in the range, saving this
* inside the src array. Then it locks those pages and unmaps them. Once the pages
* are locked and unmapped, it checks 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. It then restores any pages that are
* pinned, by remapping and unlocking those pages.
*
* At this point it calls the alloc_and_copy() callback. For documentation on
* what is expected from that callback, see struct migrate_vma_ops comments in
* include/linux/migrate.h
*
* After the alloc_and_copy() callback, this function goes 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 the function tries 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.
*
* It then calls the finalize_and_map() callback. See comments for "struct
* migrate_vma_ops", in include/linux/migrate.h for details about
* finalize_and_map() behavior.
*
* After the finalize_and_map() callback, for successfully migrated pages, this
* function updates the CPU page table to point to new pages, otherwise it
* restores the CPU page table to point to the original source pages.
*
* Function returns 0 after the above steps, even if no pages were migrated
* (The function only returns an error if any of the arguments are invalid.)
*
* Both src and dst array must be big enough for (end - start) >> PAGE_SHIFT
* unsigned long entries.