linux/mm/migrate.c
Baolin Wang eebb3dabbb mm: migrate: record the mlocked page status to remove unnecessary lru drain
When doing compaction, I found the lru_add_drain() is an obvious hotspot
when migrating pages. The distribution of this hotspot is as follows:
   - 18.75% compact_zone
      - 17.39% migrate_pages
         - 13.79% migrate_pages_batch
            - 11.66% migrate_folio_move
               - 7.02% lru_add_drain
                  + 7.02% lru_add_drain_cpu
               + 3.00% move_to_new_folio
                 1.23% rmap_walk
            + 1.92% migrate_folio_unmap
         + 3.20% migrate_pages_sync
      + 0.90% isolate_migratepages

The lru_add_drain() was added by commit c3096e6782 ("mm/migrate:
__unmap_and_move() push good newpage to LRU") to drain the newpage to LRU
immediately, to help to build up the correct newpage->mlock_count in
remove_migration_ptes() for mlocked pages.  However, if there are no
mlocked pages are migrating, then we can avoid this lru drain operation,
especailly for the heavy concurrent scenarios.

So we can record the source pages' mlocked status in
migrate_folio_unmap(), and only drain the lru list when the mlocked status
is set in migrate_folio_move().

In addition, the page was already isolated from lru when migrating, so
checking the mlocked status is stable by folio_test_mlocked() in
migrate_folio_unmap().

After this patch, I can see the hotpot of the lru_add_drain() is gone:
   - 9.41% migrate_pages_batch
      - 6.15% migrate_folio_move
         - 3.64% move_to_new_folio
            + 1.80% migrate_folio_extra
            + 1.70% buffer_migrate_folio
         + 1.41% rmap_walk
         + 0.62% folio_add_lru
      + 3.07% migrate_folio_unmap

Meanwhile, the compaction latency shows some improvements when running
thpscale:
                            base                   patched
Amean     fault-both-1      1131.22 (   0.00%)     1112.55 *   1.65%*
Amean     fault-both-3      2489.75 (   0.00%)     2324.15 *   6.65%*
Amean     fault-both-5      3257.37 (   0.00%)     3183.18 *   2.28%*
Amean     fault-both-7      4257.99 (   0.00%)     4079.04 *   4.20%*
Amean     fault-both-12     6614.02 (   0.00%)     6075.60 *   8.14%*
Amean     fault-both-18    10607.78 (   0.00%)     8978.86 *  15.36%*
Amean     fault-both-24    14911.65 (   0.00%)    11619.55 *  22.08%*
Amean     fault-both-30    14954.67 (   0.00%)    14925.66 *   0.19%*
Amean     fault-both-32    16654.87 (   0.00%)    15580.31 *   6.45%*

Link: https://lkml.kernel.org/r/06e9153a7a4850352ec36602df3a3a844de45698.1697859741.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yin Fengwei <fengwei.yin@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2023-10-25 16:47:14 -07:00

2605 lines
69 KiB
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/ksm.h>
#include <linux/rmap.h>
#include <linux/topology.h>
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/writeback.h>
#include <linux/mempolicy.h>
#include <linux/vmalloc.h>
#include <linux/security.h>
#include <linux/backing-dev.h>
#include <linux/compaction.h>
#include <linux/syscalls.h>
#include <linux/compat.h>
#include <linux/hugetlb.h>
#include <linux/hugetlb_cgroup.h>
#include <linux/gfp.h>
#include <linux/pfn_t.h>
#include <linux/memremap.h>
#include <linux/userfaultfd_k.h>
#include <linux/balloon_compaction.h>
#include <linux/page_idle.h>
#include <linux/page_owner.h>
#include <linux/sched/mm.h>
#include <linux/ptrace.h>
#include <linux/oom.h>
#include <linux/memory.h>
#include <linux/random.h>
#include <linux/sched/sysctl.h>
#include <linux/memory-tiers.h>
#include <asm/tlbflush.h>
#include <trace/events/migrate.h>
#include "internal.h"
bool isolate_movable_page(struct page *page, isolate_mode_t mode)
{
struct folio *folio = folio_get_nontail_page(page);
const struct movable_operations *mops;
/*
* Avoid burning cycles with pages that are yet under __free_pages(),
* or just got freed under us.
*
* In case we 'win' a race for a movable page being freed under us and
* raise its refcount preventing __free_pages() from doing its job
* the put_page() at the end of this block will take care of
* release this page, thus avoiding a nasty leakage.
*/
if (!folio)
goto out;
if (unlikely(folio_test_slab(folio)))
goto out_putfolio;
/* Pairs with smp_wmb() in slab freeing, e.g. SLUB's __free_slab() */
smp_rmb();
/*
* Check movable flag before taking the page lock because
* we use non-atomic bitops on newly allocated page flags so
* unconditionally grabbing the lock ruins page's owner side.
*/
if (unlikely(!__folio_test_movable(folio)))
goto out_putfolio;
/* Pairs with smp_wmb() in slab allocation, e.g. SLUB's alloc_slab_page() */
smp_rmb();
if (unlikely(folio_test_slab(folio)))
goto out_putfolio;
/*
* 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(!folio_trylock(folio)))
goto out_putfolio;
if (!folio_test_movable(folio) || folio_test_isolated(folio))
goto out_no_isolated;
mops = folio_movable_ops(folio);
VM_BUG_ON_FOLIO(!mops, folio);
if (!mops->isolate_page(&folio->page, mode))
goto out_no_isolated;
/* Driver shouldn't use PG_isolated bit of page->flags */
WARN_ON_ONCE(folio_test_isolated(folio));
folio_set_isolated(folio);
folio_unlock(folio);
return true;
out_no_isolated:
folio_unlock(folio);
out_putfolio:
folio_put(folio);
out:
return false;
}
static void putback_movable_folio(struct folio *folio)
{
const struct movable_operations *mops = folio_movable_ops(folio);
mops->putback_page(&folio->page);
folio_clear_isolated(folio);
}
/*
* Put previously isolated pages back onto the appropriate lists
* from where they were once taken off for compaction/migration.
*
* This function shall be used whenever the isolated pageset has been
* built from lru, balloon, hugetlbfs page. See isolate_migratepages_range()
* and isolate_hugetlb().
*/
void putback_movable_pages(struct list_head *l)
{
struct folio *folio;
struct folio *folio2;
list_for_each_entry_safe(folio, folio2, l, lru) {
if (unlikely(folio_test_hugetlb(folio))) {
folio_putback_active_hugetlb(folio);
continue;
}
list_del(&folio->lru);
/*
* We isolated non-lru movable folio so here we can use
* __folio_test_movable because LRU folio's mapping cannot
* have PAGE_MAPPING_MOVABLE.
*/
if (unlikely(__folio_test_movable(folio))) {
VM_BUG_ON_FOLIO(!folio_test_isolated(folio), folio);
folio_lock(folio);
if (folio_test_movable(folio))
putback_movable_folio(folio);
else
folio_clear_isolated(folio);
folio_unlock(folio);
folio_put(folio);
} else {
node_stat_mod_folio(folio, NR_ISOLATED_ANON +
folio_is_file_lru(folio), -folio_nr_pages(folio));
folio_putback_lru(folio);
}
}
}
/*
* Restore a potential migration pte to a working pte entry
*/
static bool remove_migration_pte(struct folio *folio,
struct vm_area_struct *vma, unsigned long addr, void *old)
{
DEFINE_FOLIO_VMA_WALK(pvmw, old, vma, addr, PVMW_SYNC | PVMW_MIGRATION);
while (page_vma_mapped_walk(&pvmw)) {
rmap_t rmap_flags = RMAP_NONE;
pte_t old_pte;
pte_t pte;
swp_entry_t entry;
struct page *new;
unsigned long idx = 0;
/* pgoff is invalid for ksm pages, but they are never large */
if (folio_test_large(folio) && !folio_test_hugetlb(folio))
idx = linear_page_index(vma, pvmw.address) - pvmw.pgoff;
new = folio_page(folio, idx);
#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
/* PMD-mapped THP migration entry */
if (!pvmw.pte) {
VM_BUG_ON_FOLIO(folio_test_hugetlb(folio) ||
!folio_test_pmd_mappable(folio), folio);
remove_migration_pmd(&pvmw, new);
continue;
}
#endif
folio_get(folio);
pte = mk_pte(new, READ_ONCE(vma->vm_page_prot));
old_pte = ptep_get(pvmw.pte);
if (pte_swp_soft_dirty(old_pte))
pte = pte_mksoft_dirty(pte);
entry = pte_to_swp_entry(old_pte);
if (!is_migration_entry_young(entry))
pte = pte_mkold(pte);
if (folio_test_dirty(folio) && is_migration_entry_dirty(entry))
pte = pte_mkdirty(pte);
if (is_writable_migration_entry(entry))
pte = pte_mkwrite(pte, vma);
else if (pte_swp_uffd_wp(old_pte))
pte = pte_mkuffd_wp(pte);
if (folio_test_anon(folio) && !is_readable_migration_entry(entry))
rmap_flags |= RMAP_EXCLUSIVE;
if (unlikely(is_device_private_page(new))) {
if (pte_write(pte))
entry = make_writable_device_private_entry(
page_to_pfn(new));
else
entry = make_readable_device_private_entry(
page_to_pfn(new));
pte = swp_entry_to_pte(entry);
if (pte_swp_soft_dirty(old_pte))
pte = pte_swp_mksoft_dirty(pte);
if (pte_swp_uffd_wp(old_pte))
pte = pte_swp_mkuffd_wp(pte);
}
#ifdef CONFIG_HUGETLB_PAGE
if (folio_test_hugetlb(folio)) {
struct hstate *h = hstate_vma(vma);
unsigned int shift = huge_page_shift(h);
unsigned long psize = huge_page_size(h);
pte = arch_make_huge_pte(pte, shift, vma->vm_flags);
if (folio_test_anon(folio))
hugepage_add_anon_rmap(folio, vma, pvmw.address,
rmap_flags);
else
page_dup_file_rmap(new, true);
set_huge_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte,
psize);
} else
#endif
{
if (folio_test_anon(folio))
page_add_anon_rmap(new, vma, pvmw.address,
rmap_flags);
else
page_add_file_rmap(new, vma, false);
set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
}
if (vma->vm_flags & VM_LOCKED)
mlock_drain_local();
trace_remove_migration_pte(pvmw.address, pte_val(pte),
compound_order(new));
/* No need to invalidate - it was non-present before */
update_mmu_cache(vma, pvmw.address, pvmw.pte);
}
return true;
}
/*
* Get rid of all migration entries and replace them by
* references to the indicated page.
*/
void remove_migration_ptes(struct folio *src, struct folio *dst, bool locked)
{
struct rmap_walk_control rwc = {
.rmap_one = remove_migration_pte,
.arg = src,
};
if (locked)
rmap_walk_locked(dst, &rwc);
else
rmap_walk(dst, &rwc);
}
/*
* Something used the pte of a page under migration. We need to
* get to the page and wait until migration is finished.
* When we return from this function the fault will be retried.
*/
void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
unsigned long address)
{
spinlock_t *ptl;
pte_t *ptep;
pte_t pte;
swp_entry_t entry;
ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
if (!ptep)
return;
pte = ptep_get(ptep);
pte_unmap(ptep);
if (!is_swap_pte(pte))
goto out;
entry = pte_to_swp_entry(pte);
if (!is_migration_entry(entry))
goto out;
migration_entry_wait_on_locked(entry, ptl);
return;
out:
spin_unlock(ptl);
}
#ifdef CONFIG_HUGETLB_PAGE
/*
* The vma read lock must be held upon entry. Holding that lock prevents either
* the pte or the ptl from being freed.
*
* This function will release the vma lock before returning.
*/
void migration_entry_wait_huge(struct vm_area_struct *vma, pte_t *ptep)
{
spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), vma->vm_mm, ptep);
pte_t pte;
hugetlb_vma_assert_locked(vma);
spin_lock(ptl);
pte = huge_ptep_get(ptep);
if (unlikely(!is_hugetlb_entry_migration(pte))) {
spin_unlock(ptl);
hugetlb_vma_unlock_read(vma);
} else {
/*
* If migration entry existed, safe to release vma lock
* here because the pgtable page won't be freed without the
* pgtable lock released. See comment right above pgtable
* lock release in migration_entry_wait_on_locked().
*/
hugetlb_vma_unlock_read(vma);
migration_entry_wait_on_locked(pte_to_swp_entry(pte), ptl);
}
}
#endif
#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
{
spinlock_t *ptl;
ptl = pmd_lock(mm, pmd);
if (!is_pmd_migration_entry(*pmd))
goto unlock;
migration_entry_wait_on_locked(pmd_to_swp_entry(*pmd), ptl);
return;
unlock:
spin_unlock(ptl);
}
#endif
static int folio_expected_refs(struct address_space *mapping,
struct folio *folio)
{
int refs = 1;
if (!mapping)
return refs;
refs += folio_nr_pages(folio);
if (folio_test_private(folio))
refs++;
return refs;
}
/*
* Replace the page in the mapping.
*
* The number of remaining references must be:
* 1 for anonymous pages without a mapping
* 2 for pages with a mapping
* 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
*/
int folio_migrate_mapping(struct address_space *mapping,
struct folio *newfolio, struct folio *folio, int extra_count)
{
XA_STATE(xas, &mapping->i_pages, folio_index(folio));
struct zone *oldzone, *newzone;
int dirty;
int expected_count = folio_expected_refs(mapping, folio) + extra_count;
long nr = folio_nr_pages(folio);
if (!mapping) {
/* Anonymous page without mapping */
if (folio_ref_count(folio) != expected_count)
return -EAGAIN;
/* No turning back from here */
newfolio->index = folio->index;
newfolio->mapping = folio->mapping;
if (folio_test_swapbacked(folio))
__folio_set_swapbacked(newfolio);
return MIGRATEPAGE_SUCCESS;
}
oldzone = folio_zone(folio);
newzone = folio_zone(newfolio);
xas_lock_irq(&xas);
if (!folio_ref_freeze(folio, expected_count)) {
xas_unlock_irq(&xas);
return -EAGAIN;
}
/*
* Now we know that no one else is looking at the folio:
* no turning back from here.
*/
newfolio->index = folio->index;
newfolio->mapping = folio->mapping;
folio_ref_add(newfolio, nr); /* add cache reference */
if (folio_test_swapbacked(folio)) {
__folio_set_swapbacked(newfolio);
if (folio_test_swapcache(folio)) {
folio_set_swapcache(newfolio);
newfolio->private = folio_get_private(folio);
}
} else {
VM_BUG_ON_FOLIO(folio_test_swapcache(folio), folio);
}
/* Move dirty while page refs frozen and newpage not yet exposed */
dirty = folio_test_dirty(folio);
if (dirty) {
folio_clear_dirty(folio);
folio_set_dirty(newfolio);
}
xas_store(&xas, newfolio);
/*
* Drop cache reference from old page by unfreezing
* to one less reference.
* We know this isn't the last reference.
*/
folio_ref_unfreeze(folio, expected_count - nr);
xas_unlock(&xas);
/* Leave irq disabled to prevent preemption while updating stats */
/*
* If moved to a different zone then also account
* the page for that zone. Other VM counters will be
* taken care of when we establish references to the
* new page and drop references to the old page.
*
* Note that anonymous pages are accounted for
* via NR_FILE_PAGES and NR_ANON_MAPPED if they
* are mapped to swap space.
*/
if (newzone != oldzone) {
struct lruvec *old_lruvec, *new_lruvec;
struct mem_cgroup *memcg;
memcg = folio_memcg(folio);
old_lruvec = mem_cgroup_lruvec(memcg, oldzone->zone_pgdat);
new_lruvec = mem_cgroup_lruvec(memcg, newzone->zone_pgdat);
__mod_lruvec_state(old_lruvec, NR_FILE_PAGES, -nr);
__mod_lruvec_state(new_lruvec, NR_FILE_PAGES, nr);
if (folio_test_swapbacked(folio) && !folio_test_swapcache(folio)) {
__mod_lruvec_state(old_lruvec, NR_SHMEM, -nr);
__mod_lruvec_state(new_lruvec, NR_SHMEM, nr);
if (folio_test_pmd_mappable(folio)) {
__mod_lruvec_state(old_lruvec, NR_SHMEM_THPS, -nr);
__mod_lruvec_state(new_lruvec, NR_SHMEM_THPS, nr);
}
}
#ifdef CONFIG_SWAP
if (folio_test_swapcache(folio)) {
__mod_lruvec_state(old_lruvec, NR_SWAPCACHE, -nr);
__mod_lruvec_state(new_lruvec, NR_SWAPCACHE, nr);
}
#endif
if (dirty && mapping_can_writeback(mapping)) {
__mod_lruvec_state(old_lruvec, NR_FILE_DIRTY, -nr);
__mod_zone_page_state(oldzone, NR_ZONE_WRITE_PENDING, -nr);
__mod_lruvec_state(new_lruvec, NR_FILE_DIRTY, nr);
__mod_zone_page_state(newzone, NR_ZONE_WRITE_PENDING, nr);
}
}
local_irq_enable();
return MIGRATEPAGE_SUCCESS;
}
EXPORT_SYMBOL(folio_migrate_mapping);
/*
* The expected number of remaining references is the same as that
* of folio_migrate_mapping().
*/
int migrate_huge_page_move_mapping(struct address_space *mapping,
struct folio *dst, struct folio *src)
{
XA_STATE(xas, &mapping->i_pages, folio_index(src));
int expected_count;
xas_lock_irq(&xas);
expected_count = folio_expected_refs(mapping, src);
if (!folio_ref_freeze(src, expected_count)) {
xas_unlock_irq(&xas);
return -EAGAIN;
}
dst->index = src->index;
dst->mapping = src->mapping;
folio_ref_add(dst, folio_nr_pages(dst));
xas_store(&xas, dst);
folio_ref_unfreeze(src, expected_count - folio_nr_pages(src));
xas_unlock_irq(&xas);
return MIGRATEPAGE_SUCCESS;
}
/*
* Copy the flags and some other ancillary information
*/
void folio_migrate_flags(struct folio *newfolio, struct folio *folio)
{
int cpupid;
if (folio_test_error(folio))
folio_set_error(newfolio);
if (folio_test_referenced(folio))
folio_set_referenced(newfolio);
if (folio_test_uptodate(folio))
folio_mark_uptodate(newfolio);
if (folio_test_clear_active(folio)) {
VM_BUG_ON_FOLIO(folio_test_unevictable(folio), folio);
folio_set_active(newfolio);
} else if (folio_test_clear_unevictable(folio))
folio_set_unevictable(newfolio);
if (folio_test_workingset(folio))
folio_set_workingset(newfolio);
if (folio_test_checked(folio))
folio_set_checked(newfolio);
/*
* PG_anon_exclusive (-> PG_mappedtodisk) is always migrated via
* migration entries. We can still have PG_anon_exclusive set on an
* effectively unmapped and unreferenced first sub-pages of an
* anonymous THP: we can simply copy it here via PG_mappedtodisk.
*/
if (folio_test_mappedtodisk(folio))
folio_set_mappedtodisk(newfolio);
/* Move dirty on pages not done by folio_migrate_mapping() */
if (folio_test_dirty(folio))
folio_set_dirty(newfolio);
if (folio_test_young(folio))
folio_set_young(newfolio);
if (folio_test_idle(folio))
folio_set_idle(newfolio);
/*
* Copy NUMA information to the new page, to prevent over-eager
* future migrations of this same page.
*/
cpupid = folio_xchg_last_cpupid(folio, -1);
/*
* For memory tiering mode, when migrate between slow and fast
* memory node, reset cpupid, because that is used to record
* page access time in slow memory node.
*/
if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) {
bool f_toptier = node_is_toptier(folio_nid(folio));
bool t_toptier = node_is_toptier(folio_nid(newfolio));
if (f_toptier != t_toptier)
cpupid = -1;
}
folio_xchg_last_cpupid(newfolio, cpupid);
folio_migrate_ksm(newfolio, folio);
/*
* Please do not reorder this without considering how mm/ksm.c's
* get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
*/
if (folio_test_swapcache(folio))
folio_clear_swapcache(folio);
folio_clear_private(folio);
/* page->private contains hugetlb specific flags */
if (!folio_test_hugetlb(folio))
folio->private = NULL;
/*
* If any waiters have accumulated on the new page then
* wake them up.
*/
if (folio_test_writeback(newfolio))
folio_end_writeback(newfolio);
/*
* PG_readahead shares the same bit with PG_reclaim. The above
* end_page_writeback() may clear PG_readahead mistakenly, so set the
* bit after that.
*/
if (folio_test_readahead(folio))
folio_set_readahead(newfolio);
folio_copy_owner(newfolio, folio);
mem_cgroup_migrate(folio, newfolio);
}
EXPORT_SYMBOL(folio_migrate_flags);
void folio_migrate_copy(struct folio *newfolio, struct folio *folio)
{
folio_copy(newfolio, folio);
folio_migrate_flags(newfolio, folio);
}
EXPORT_SYMBOL(folio_migrate_copy);
/************************************************************
* Migration functions
***********************************************************/
int migrate_folio_extra(struct address_space *mapping, struct folio *dst,
struct folio *src, enum migrate_mode mode, int extra_count)
{
int rc;
BUG_ON(folio_test_writeback(src)); /* Writeback must be complete */
rc = folio_migrate_mapping(mapping, dst, src, extra_count);
if (rc != MIGRATEPAGE_SUCCESS)
return rc;
if (mode != MIGRATE_SYNC_NO_COPY)
folio_migrate_copy(dst, src);
else
folio_migrate_flags(dst, src);
return MIGRATEPAGE_SUCCESS;
}
/**
* migrate_folio() - Simple folio migration.
* @mapping: The address_space containing the folio.
* @dst: The folio to migrate the data to.
* @src: The folio containing the current data.
* @mode: How to migrate the page.
*
* Common logic to directly migrate a single LRU folio suitable for
* folios that do not use PagePrivate/PagePrivate2.
*
* Folios are locked upon entry and exit.
*/
int migrate_folio(struct address_space *mapping, struct folio *dst,
struct folio *src, enum migrate_mode mode)
{
return migrate_folio_extra(mapping, dst, src, mode, 0);
}
EXPORT_SYMBOL(migrate_folio);
#ifdef CONFIG_BUFFER_HEAD
/* 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;
struct buffer_head *failed_bh;
do {
if (!trylock_buffer(bh)) {
if (mode == MIGRATE_ASYNC)
goto unlock;
if (mode == MIGRATE_SYNC_LIGHT && !buffer_uptodate(bh))
goto unlock;
lock_buffer(bh);
}
bh = bh->b_this_page;
} while (bh != head);
return true;
unlock:
/* We failed to lock the buffer and cannot stall. */
failed_bh = bh;
bh = head;
while (bh != failed_bh) {
unlock_buffer(bh);
bh = bh->b_this_page;
}
return false;
}
static int __buffer_migrate_folio(struct address_space *mapping,
struct folio *dst, struct folio *src, enum migrate_mode mode,
bool check_refs)
{
struct buffer_head *bh, *head;
int rc;
int expected_count;
head = folio_buffers(src);
if (!head)
return migrate_folio(mapping, dst, src, mode);
/* Check whether page does not have extra refs before we do more work */
expected_count = folio_expected_refs(mapping, src);
if (folio_ref_count(src) != expected_count)
return -EAGAIN;
if (!buffer_migrate_lock_buffers(head, mode))
return -EAGAIN;
if (check_refs) {
bool busy;
bool invalidated = false;
recheck_buffers:
busy = false;
spin_lock(&mapping->private_lock);
bh = head;
do {
if (atomic_read(&bh->b_count)) {
busy = true;
break;
}
bh = bh->b_this_page;
} while (bh != head);
if (busy) {
if (invalidated) {
rc = -EAGAIN;
goto unlock_buffers;
}
spin_unlock(&mapping->private_lock);
invalidate_bh_lrus();
invalidated = true;
goto recheck_buffers;
}
}
rc = folio_migrate_mapping(mapping, dst, src, 0);
if (rc != MIGRATEPAGE_SUCCESS)
goto unlock_buffers;
folio_attach_private(dst, folio_detach_private(src));
bh = head;
do {
folio_set_bh(bh, dst, bh_offset(bh));
bh = bh->b_this_page;
} while (bh != head);
if (mode != MIGRATE_SYNC_NO_COPY)
folio_migrate_copy(dst, src);
else
folio_migrate_flags(dst, src);
rc = MIGRATEPAGE_SUCCESS;
unlock_buffers:
if (check_refs)
spin_unlock(&mapping->private_lock);
bh = head;
do {
unlock_buffer(bh);
bh = bh->b_this_page;
} while (bh != head);
return rc;
}
/**
* buffer_migrate_folio() - Migration function for folios with buffers.
* @mapping: The address space containing @src.
* @dst: The folio to migrate to.
* @src: The folio to migrate from.
* @mode: How to migrate the folio.
*
* This function can only be used if the underlying filesystem guarantees
* that no other references to @src exist. For example attached buffer
* heads are accessed only under the folio lock. If your filesystem cannot
* provide this guarantee, buffer_migrate_folio_norefs() may be more
* appropriate.
*
* Return: 0 on success or a negative errno on failure.
*/
int buffer_migrate_folio(struct address_space *mapping,
struct folio *dst, struct folio *src, enum migrate_mode mode)
{
return __buffer_migrate_folio(mapping, dst, src, mode, false);
}
EXPORT_SYMBOL(buffer_migrate_folio);
/**
* buffer_migrate_folio_norefs() - Migration function for folios with buffers.
* @mapping: The address space containing @src.
* @dst: The folio to migrate to.
* @src: The folio to migrate from.
* @mode: How to migrate the folio.
*
* Like buffer_migrate_folio() except that this variant is more careful
* and checks that there are also no buffer head references. This function
* is the right one for mappings where buffer heads are directly looked
* up and referenced (such as block device mappings).
*
* Return: 0 on success or a negative errno on failure.
*/
int buffer_migrate_folio_norefs(struct address_space *mapping,
struct folio *dst, struct folio *src, enum migrate_mode mode)
{
return __buffer_migrate_folio(mapping, dst, src, mode, true);
}
EXPORT_SYMBOL_GPL(buffer_migrate_folio_norefs);
#endif /* CONFIG_BUFFER_HEAD */
int filemap_migrate_folio(struct address_space *mapping,
struct folio *dst, struct folio *src, enum migrate_mode mode)
{
int ret;
ret = folio_migrate_mapping(mapping, dst, src, 0);
if (ret != MIGRATEPAGE_SUCCESS)
return ret;
if (folio_get_private(src))
folio_attach_private(dst, folio_detach_private(src));
if (mode != MIGRATE_SYNC_NO_COPY)
folio_migrate_copy(dst, src);
else
folio_migrate_flags(dst, src);
return MIGRATEPAGE_SUCCESS;
}
EXPORT_SYMBOL_GPL(filemap_migrate_folio);
/*
* Writeback a folio to clean the dirty state
*/
static int writeout(struct address_space *mapping, struct folio *folio)
{
struct writeback_control wbc = {
.sync_mode = WB_SYNC_NONE,
.nr_to_write = 1,
.range_start = 0,
.range_end = LLONG_MAX,
.for_reclaim = 1
};
int rc;
if (!mapping->a_ops->writepage)
/* No write method for the address space */
return -EINVAL;
if (!folio_clear_dirty_for_io(folio))
/* Someone else already triggered a write */
return -EAGAIN;
/*
* A dirty folio may imply that the underlying filesystem has
* the folio on some queue. So the folio must be clean for
* migration. Writeout may mean we lose the lock and the
* folio state is no longer what we checked for earlier.
* At this point we know that the migration attempt cannot
* be successful.
*/
remove_migration_ptes(folio, folio, false);
rc = mapping->a_ops->writepage(&folio->page, &wbc);
if (rc != AOP_WRITEPAGE_ACTIVATE)
/* unlocked. Relock */
folio_lock(folio);
return (rc < 0) ? -EIO : -EAGAIN;
}
/*
* Default handling if a filesystem does not provide a migration function.
*/
static int fallback_migrate_folio(struct address_space *mapping,
struct folio *dst, struct folio *src, enum migrate_mode mode)
{
if (folio_test_dirty(src)) {
/* Only writeback folios in full synchronous migration */
switch (mode) {
case MIGRATE_SYNC:
case MIGRATE_SYNC_NO_COPY:
break;
default:
return -EBUSY;
}
return writeout(mapping, src);
}
/*
* Buffers may be managed in a filesystem specific way.
* We must have no buffers or drop them.
*/
if (!filemap_release_folio(src, GFP_KERNEL))
return mode == MIGRATE_SYNC ? -EAGAIN : -EBUSY;
return migrate_folio(mapping, dst, src, mode);
}
/*
* Move a page to a newly allocated page
* The page is locked and all ptes have been successfully removed.
*
* The new page will have replaced the old page if this function
* is successful.
*
* Return value:
* < 0 - error code
* MIGRATEPAGE_SUCCESS - success
*/
static int move_to_new_folio(struct folio *dst, struct folio *src,
enum migrate_mode mode)
{
int rc = -EAGAIN;
bool is_lru = !__folio_test_movable(src);
VM_BUG_ON_FOLIO(!folio_test_locked(src), src);
VM_BUG_ON_FOLIO(!folio_test_locked(dst), dst);
if (likely(is_lru)) {
struct address_space *mapping = folio_mapping(src);
if (!mapping)
rc = migrate_folio(mapping, dst, src, mode);
else if (mapping->a_ops->migrate_folio)
/*
* Most folios have a mapping and most filesystems
* provide a migrate_folio callback. Anonymous folios
* are part of swap space which also has its own
* migrate_folio callback. This is the most common path
* for page migration.
*/
rc = mapping->a_ops->migrate_folio(mapping, dst, src,
mode);
else
rc = fallback_migrate_folio(mapping, dst, src, mode);
} else {
const struct movable_operations *mops;
/*
* In case of non-lru page, it could be released after
* isolation step. In that case, we shouldn't try migration.
*/
VM_BUG_ON_FOLIO(!folio_test_isolated(src), src);
if (!folio_test_movable(src)) {
rc = MIGRATEPAGE_SUCCESS;
folio_clear_isolated(src);
goto out;
}
mops = folio_movable_ops(src);
rc = mops->migrate_page(&dst->page, &src->page, mode);
WARN_ON_ONCE(rc == MIGRATEPAGE_SUCCESS &&
!folio_test_isolated(src));
}
/*
* When successful, old pagecache src->mapping must be cleared before
* src is freed; but stats require that PageAnon be left as PageAnon.
*/
if (rc == MIGRATEPAGE_SUCCESS) {
if (__folio_test_movable(src)) {
VM_BUG_ON_FOLIO(!folio_test_isolated(src), src);
/*
* We clear PG_movable under page_lock so any compactor
* cannot try to migrate this page.
*/
folio_clear_isolated(src);
}
/*
* Anonymous and movable src->mapping will be cleared by
* free_pages_prepare so don't reset it here for keeping
* the type to work PageAnon, for example.
*/
if (!folio_mapping_flags(src))
src->mapping = NULL;
if (likely(!folio_is_zone_device(dst)))
flush_dcache_folio(dst);
}
out:
return rc;
}
/*
* To record some information during migration, we use some unused
* fields (mapping and private) of struct folio of the newly allocated
* destination folio. This is safe because nobody is using them
* except us.
*/
union migration_ptr {
struct anon_vma *anon_vma;
struct address_space *mapping;
};
enum {
PAGE_WAS_MAPPED = BIT(0),
PAGE_WAS_MLOCKED = BIT(1),
};
static void __migrate_folio_record(struct folio *dst,
unsigned long old_page_state,
struct anon_vma *anon_vma)
{
union migration_ptr ptr = { .anon_vma = anon_vma };
dst->mapping = ptr.mapping;
dst->private = (void *)old_page_state;
}
static void __migrate_folio_extract(struct folio *dst,
int *old_page_state,
struct anon_vma **anon_vmap)
{
union migration_ptr ptr = { .mapping = dst->mapping };
*anon_vmap = ptr.anon_vma;
*old_page_state = (unsigned long)dst->private;
dst->mapping = NULL;
dst->private = NULL;
}
/* Restore the source folio to the original state upon failure */
static void migrate_folio_undo_src(struct folio *src,
int page_was_mapped,
struct anon_vma *anon_vma,
bool locked,
struct list_head *ret)
{
if (page_was_mapped)
remove_migration_ptes(src, src, false);
/* Drop an anon_vma reference if we took one */
if (anon_vma)
put_anon_vma(anon_vma);
if (locked)
folio_unlock(src);
if (ret)
list_move_tail(&src->lru, ret);
}
/* Restore the destination folio to the original state upon failure */
static void migrate_folio_undo_dst(struct folio *dst, bool locked,
free_folio_t put_new_folio, unsigned long private)
{
if (locked)
folio_unlock(dst);
if (put_new_folio)
put_new_folio(dst, private);
else
folio_put(dst);
}
/* Cleanup src folio upon migration success */
static void migrate_folio_done(struct folio *src,
enum migrate_reason reason)
{
/*
* Compaction can migrate also non-LRU pages which are
* not accounted to NR_ISOLATED_*. They can be recognized
* as __folio_test_movable
*/
if (likely(!__folio_test_movable(src)))
mod_node_page_state(folio_pgdat(src), NR_ISOLATED_ANON +
folio_is_file_lru(src), -folio_nr_pages(src));
if (reason != MR_MEMORY_FAILURE)
/* We release the page in page_handle_poison. */
folio_put(src);
}
/* Obtain the lock on page, remove all ptes. */
static int migrate_folio_unmap(new_folio_t get_new_folio,
free_folio_t put_new_folio, unsigned long private,
struct folio *src, struct folio **dstp, enum migrate_mode mode,
enum migrate_reason reason, struct list_head *ret)
{
struct folio *dst;
int rc = -EAGAIN;
int old_page_state = 0;
struct anon_vma *anon_vma = NULL;
bool is_lru = !__folio_test_movable(src);
bool locked = false;
bool dst_locked = false;
if (folio_ref_count(src) == 1) {
/* Folio was freed from under us. So we are done. */
folio_clear_active(src);
folio_clear_unevictable(src);
/* free_pages_prepare() will clear PG_isolated. */
list_del(&src->lru);
migrate_folio_done(src, reason);
return MIGRATEPAGE_SUCCESS;
}
dst = get_new_folio(src, private);
if (!dst)
return -ENOMEM;
*dstp = dst;
dst->private = NULL;
if (!folio_trylock(src)) {
if (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;
/*
* In "light" mode, we can wait for transient locks (eg
* inserting a page into the page table), but it's not
* worth waiting for I/O.
*/
if (mode == MIGRATE_SYNC_LIGHT && !folio_test_uptodate(src))
goto out;
folio_lock(src);
}
locked = true;
if (folio_test_mlocked(src))
old_page_state |= PAGE_WAS_MLOCKED;
if (folio_test_writeback(src)) {
/*
* Only in the case of a full synchronous migration is it
* necessary to wait for PageWriteback. In the async case,
* the retry loop is too short and in the sync-light case,
* the overhead of stalling is too much
*/
switch (mode) {
case MIGRATE_SYNC:
case MIGRATE_SYNC_NO_COPY:
break;
default:
rc = -EBUSY;
goto out;
}
folio_wait_writeback(src);
}
/*
* By try_to_migrate(), src->mapcount goes down to 0 here. In this case,
* we cannot notice that anon_vma is freed while we migrate a page.
* This get_anon_vma() delays freeing anon_vma pointer until the end
* of migration. File cache pages are no problem because of page_lock()
* File Caches may use write_page() or lock_page() in migration, then,
* just care Anon page here.
*
* Only folio_get_anon_vma() understands the subtleties of
* getting a hold on an anon_vma from outside one of its mms.
* But if we cannot get anon_vma, then we won't need it anyway,
* because that implies that the anon page is no longer mapped
* (and cannot be remapped so long as we hold the page lock).
*/
if (folio_test_anon(src) && !folio_test_ksm(src))
anon_vma = folio_get_anon_vma(src);
/*
* Block others from accessing the new page when we get around to
* establishing additional references. We are usually the only one
* holding a reference to dst at this point. We used to have a BUG
* here if folio_trylock(dst) fails, but would like to allow for
* cases where there might be a race with the previous use of dst.
* This is much like races on refcount of oldpage: just don't BUG().
*/
if (unlikely(!folio_trylock(dst)))
goto out;
dst_locked = true;
if (unlikely(!is_lru)) {
__migrate_folio_record(dst, old_page_state, anon_vma);
return MIGRATEPAGE_UNMAP;
}
/*
* Corner case handling:
* 1. When a new swap-cache page is read into, it is added to the LRU
* and treated as swapcache but it has no rmap yet.
* Calling try_to_unmap() against a src->mapping==NULL page will
* trigger a BUG. So handle it here.
* 2. An orphaned page (see truncate_cleanup_page) might have
* fs-private metadata. The page can be picked up due to memory
* offlining. Everywhere else except page reclaim, the page is
* invisible to the vm, so the page can not be migrated. So try to
* free the metadata, so the page can be freed.
*/
if (!src->mapping) {
if (folio_test_private(src)) {
try_to_free_buffers(src);
goto out;
}
} else if (folio_mapped(src)) {
/* Establish migration ptes */
VM_BUG_ON_FOLIO(folio_test_anon(src) &&
!folio_test_ksm(src) && !anon_vma, src);
try_to_migrate(src, mode == MIGRATE_ASYNC ? TTU_BATCH_FLUSH : 0);
old_page_state |= PAGE_WAS_MAPPED;
}
if (!folio_mapped(src)) {
__migrate_folio_record(dst, old_page_state, anon_vma);
return MIGRATEPAGE_UNMAP;
}
out:
/*
* A folio that has not been unmapped will be restored to
* right list unless we want to retry.
*/
if (rc == -EAGAIN)
ret = NULL;
migrate_folio_undo_src(src, old_page_state & PAGE_WAS_MAPPED,
anon_vma, locked, ret);
migrate_folio_undo_dst(dst, dst_locked, put_new_folio, private);
return rc;
}
/* Migrate the folio to the newly allocated folio in dst. */
static int migrate_folio_move(free_folio_t put_new_folio, unsigned long private,
struct folio *src, struct folio *dst,
enum migrate_mode mode, enum migrate_reason reason,
struct list_head *ret)
{
int rc;
int old_page_state = 0;
struct anon_vma *anon_vma = NULL;
bool is_lru = !__folio_test_movable(src);
struct list_head *prev;
__migrate_folio_extract(dst, &old_page_state, &anon_vma);
prev = dst->lru.prev;
list_del(&dst->lru);
rc = move_to_new_folio(dst, src, mode);
if (rc)
goto out;
if (unlikely(!is_lru))
goto out_unlock_both;
/*
* When successful, push dst to LRU immediately: so that if it
* turns out to be an mlocked page, remove_migration_ptes() will
* automatically build up the correct dst->mlock_count for it.
*
* We would like to do something similar for the old page, when
* unsuccessful, and other cases when a page has been temporarily
* isolated from the unevictable LRU: but this case is the easiest.
*/
folio_add_lru(dst);
if (old_page_state & PAGE_WAS_MLOCKED)
lru_add_drain();
if (old_page_state & PAGE_WAS_MAPPED)
remove_migration_ptes(src, dst, false);
out_unlock_both:
folio_unlock(dst);
set_page_owner_migrate_reason(&dst->page, reason);
/*
* If migration is successful, decrease refcount of dst,
* which will not free the page because new page owner increased
* refcounter.
*/
folio_put(dst);
/*
* A folio that has been migrated has all references removed
* and will be freed.
*/
list_del(&src->lru);
/* Drop an anon_vma reference if we took one */
if (anon_vma)
put_anon_vma(anon_vma);
folio_unlock(src);
migrate_folio_done(src, reason);
return rc;
out:
/*
* A folio that has not been migrated will be restored to
* right list unless we want to retry.
*/
if (rc == -EAGAIN) {
list_add(&dst->lru, prev);
__migrate_folio_record(dst, old_page_state, anon_vma);
return rc;
}
migrate_folio_undo_src(src, old_page_state & PAGE_WAS_MAPPED,
anon_vma, true, ret);
migrate_folio_undo_dst(dst, true, put_new_folio, private);
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_folio_t get_new_folio,
free_folio_t put_new_folio, unsigned long private,
struct folio *src, int force, enum migrate_mode mode,
int reason, struct list_head *ret)
{
struct folio *dst;
int rc = -EAGAIN;
int page_was_mapped = 0;
struct anon_vma *anon_vma = NULL;
struct address_space *mapping = NULL;
if (folio_ref_count(src) == 1) {
/* page was freed from under us. So we are done. */
folio_putback_active_hugetlb(src);
return MIGRATEPAGE_SUCCESS;
}
dst = get_new_folio(src, private);
if (!dst)
return -ENOMEM;
if (!folio_trylock(src)) {
if (!force)
goto out;
switch (mode) {
case MIGRATE_SYNC:
case MIGRATE_SYNC_NO_COPY:
break;
default:
goto out;
}
folio_lock(src);
}
/*
* Check for pages which are in the process of being freed. Without
* folio_mapping() set, hugetlbfs specific move page routine will not
* be called and we could leak usage counts for subpools.
*/
if (hugetlb_folio_subpool(src) && !folio_mapping(src)) {
rc = -EBUSY;
goto out_unlock;
}
if (folio_test_anon(src))
anon_vma = folio_get_anon_vma(src);
if (unlikely(!folio_trylock(dst)))
goto put_anon;
if (folio_mapped(src)) {
enum ttu_flags ttu = 0;
if (!folio_test_anon(src)) {
/*
* In shared mappings, try_to_unmap could potentially
* call huge_pmd_unshare. Because of this, take
* semaphore in write mode here and set TTU_RMAP_LOCKED
* to let lower levels know we have taken the lock.
*/
mapping = hugetlb_page_mapping_lock_write(&src->page);
if (unlikely(!mapping))
goto unlock_put_anon;
ttu = TTU_RMAP_LOCKED;
}
try_to_migrate(src, ttu);
page_was_mapped = 1;
if (ttu & TTU_RMAP_LOCKED)
i_mmap_unlock_write(mapping);
}
if (!folio_mapped(src))
rc = move_to_new_folio(dst, src, mode);
if (page_was_mapped)
remove_migration_ptes(src,
rc == MIGRATEPAGE_SUCCESS ? dst : src, false);
unlock_put_anon:
folio_unlock(dst);
put_anon:
if (anon_vma)
put_anon_vma(anon_vma);
if (rc == MIGRATEPAGE_SUCCESS) {
move_hugetlb_state(src, dst, reason);
put_new_folio = NULL;
}
out_unlock:
folio_unlock(src);
out:
if (rc == MIGRATEPAGE_SUCCESS)
folio_putback_active_hugetlb(src);
else if (rc != -EAGAIN)
list_move_tail(&src->lru, ret);
/*
* If migration was not successful and there's a freeing callback, use
* it. Otherwise, put_page() will drop the reference grabbed during
* isolation.
*/
if (put_new_folio)
put_new_folio(dst, private);
else
folio_putback_active_hugetlb(dst);
return rc;
}
static inline int try_split_folio(struct folio *folio, struct list_head *split_folios)
{
int rc;
folio_lock(folio);
rc = split_folio_to_list(folio, split_folios);
folio_unlock(folio);
if (!rc)
list_move_tail(&folio->lru, split_folios);
return rc;
}
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
#define NR_MAX_BATCHED_MIGRATION HPAGE_PMD_NR
#else
#define NR_MAX_BATCHED_MIGRATION 512
#endif
#define NR_MAX_MIGRATE_PAGES_RETRY 10
#define NR_MAX_MIGRATE_ASYNC_RETRY 3
#define NR_MAX_MIGRATE_SYNC_RETRY \
(NR_MAX_MIGRATE_PAGES_RETRY - NR_MAX_MIGRATE_ASYNC_RETRY)
struct migrate_pages_stats {
int nr_succeeded; /* Normal and large folios migrated successfully, in
units of base pages */
int nr_failed_pages; /* Normal and large folios failed to be migrated, in
units of base pages. Untried folios aren't counted */
int nr_thp_succeeded; /* THP migrated successfully */
int nr_thp_failed; /* THP failed to be migrated */
int nr_thp_split; /* THP split before migrating */
int nr_split; /* Large folio (include THP) split before migrating */
};
/*
* Returns the number of hugetlb folios that were not migrated, or an error code
* after NR_MAX_MIGRATE_PAGES_RETRY attempts or if no hugetlb folios are movable
* any more because the list has become empty or no retryable hugetlb folios
* exist any more. It is caller's responsibility to call putback_movable_pages()
* only if ret != 0.
*/
static int migrate_hugetlbs(struct list_head *from, new_folio_t get_new_folio,
free_folio_t put_new_folio, unsigned long private,
enum migrate_mode mode, int reason,
struct migrate_pages_stats *stats,
struct list_head *ret_folios)
{
int retry = 1;
int nr_failed = 0;
int nr_retry_pages = 0;
int pass = 0;
struct folio *folio, *folio2;
int rc, nr_pages;
for (pass = 0; pass < NR_MAX_MIGRATE_PAGES_RETRY && retry; pass++) {
retry = 0;
nr_retry_pages = 0;
list_for_each_entry_safe(folio, folio2, from, lru) {
if (!folio_test_hugetlb(folio))
continue;
nr_pages = folio_nr_pages(folio);
cond_resched();
/*
* 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(folio_hstate(folio))) {
nr_failed++;
stats->nr_failed_pages += nr_pages;
list_move_tail(&folio->lru, ret_folios);
continue;
}
rc = unmap_and_move_huge_page(get_new_folio,
put_new_folio, private,
folio, pass > 2, mode,
reason, ret_folios);
/*
* The rules are:
* Success: hugetlb folio will be put back
* -EAGAIN: stay on the from list
* -ENOMEM: stay on the from list
* Other errno: put on ret_folios list
*/
switch(rc) {
case -ENOMEM:
/*
* When memory is low, don't bother to try to migrate
* other folios, just exit.
*/
stats->nr_failed_pages += nr_pages + nr_retry_pages;
return -ENOMEM;
case -EAGAIN:
retry++;
nr_retry_pages += nr_pages;
break;
case MIGRATEPAGE_SUCCESS:
stats->nr_succeeded += nr_pages;
break;
default:
/*
* Permanent failure (-EBUSY, etc.):
* unlike -EAGAIN case, the failed folio is
* removed from migration folio list and not
* retried in the next outer loop.
*/
nr_failed++;
stats->nr_failed_pages += nr_pages;
break;
}
}
}
/*
* nr_failed is number of hugetlb folios failed to be migrated. After
* NR_MAX_MIGRATE_PAGES_RETRY attempts, give up and count retried hugetlb
* folios as failed.
*/
nr_failed += retry;
stats->nr_failed_pages += nr_retry_pages;
return nr_failed;
}
/*
* migrate_pages_batch() first unmaps folios in the from list as many as
* possible, then move the unmapped folios.
*
* We only batch migration if mode == MIGRATE_ASYNC to avoid to wait a
* lock or bit when we have locked more than one folio. Which may cause
* deadlock (e.g., for loop device). So, if mode != MIGRATE_ASYNC, the
* length of the from list must be <= 1.
*/
static int migrate_pages_batch(struct list_head *from,
new_folio_t get_new_folio, free_folio_t put_new_folio,
unsigned long private, enum migrate_mode mode, int reason,
struct list_head *ret_folios, struct list_head *split_folios,
struct migrate_pages_stats *stats, int nr_pass)
{
int retry = 1;
int thp_retry = 1;
int nr_failed = 0;
int nr_retry_pages = 0;
int pass = 0;
bool is_thp = false;
bool is_large = false;
struct folio *folio, *folio2, *dst = NULL, *dst2;
int rc, rc_saved = 0, nr_pages;
LIST_HEAD(unmap_folios);
LIST_HEAD(dst_folios);
bool nosplit = (reason == MR_NUMA_MISPLACED);
VM_WARN_ON_ONCE(mode != MIGRATE_ASYNC &&
!list_empty(from) && !list_is_singular(from));
for (pass = 0; pass < nr_pass && retry; pass++) {
retry = 0;
thp_retry = 0;
nr_retry_pages = 0;
list_for_each_entry_safe(folio, folio2, from, lru) {
is_large = folio_test_large(folio);
is_thp = is_large && folio_test_pmd_mappable(folio);
nr_pages = folio_nr_pages(folio);
cond_resched();
/*
* Large folio migration might be unsupported or
* the allocation might be failed so we should retry
* on the same folio with the large folio split
* to normal folios.
*
* Split folios are put in split_folios, and
* we will migrate them after the rest of the
* list is processed.
*/
if (!thp_migration_supported() && is_thp) {
nr_failed++;
stats->nr_thp_failed++;
if (!try_split_folio(folio, split_folios)) {
stats->nr_thp_split++;
stats->nr_split++;
continue;
}
stats->nr_failed_pages += nr_pages;
list_move_tail(&folio->lru, ret_folios);
continue;
}
rc = migrate_folio_unmap(get_new_folio, put_new_folio,
private, folio, &dst, mode, reason,
ret_folios);
/*
* The rules are:
* Success: folio will be freed
* Unmap: folio will be put on unmap_folios list,
* dst folio put on dst_folios list
* -EAGAIN: stay on the from list
* -ENOMEM: stay on the from list
* Other errno: put on ret_folios list
*/
switch(rc) {
case -ENOMEM:
/*
* When memory is low, don't bother to try to migrate
* other folios, move unmapped folios, then exit.
*/
nr_failed++;
stats->nr_thp_failed += is_thp;
/* Large folio NUMA faulting doesn't split to retry. */
if (is_large && !nosplit) {
int ret = try_split_folio(folio, split_folios);
if (!ret) {
stats->nr_thp_split += is_thp;
stats->nr_split++;
break;
} else if (reason == MR_LONGTERM_PIN &&
ret == -EAGAIN) {
/*
* Try again to split large folio to
* mitigate the failure of longterm pinning.
*/
retry++;
thp_retry += is_thp;
nr_retry_pages += nr_pages;
/* Undo duplicated failure counting. */
nr_failed--;
stats->nr_thp_failed -= is_thp;
break;
}
}
stats->nr_failed_pages += nr_pages + nr_retry_pages;
/* nr_failed isn't updated for not used */
stats->nr_thp_failed += thp_retry;
rc_saved = rc;
if (list_empty(&unmap_folios))
goto out;
else
goto move;
case -EAGAIN:
retry++;
thp_retry += is_thp;
nr_retry_pages += nr_pages;
break;
case MIGRATEPAGE_SUCCESS:
stats->nr_succeeded += nr_pages;
stats->nr_thp_succeeded += is_thp;
break;
case MIGRATEPAGE_UNMAP:
list_move_tail(&folio->lru, &unmap_folios);
list_add_tail(&dst->lru, &dst_folios);
break;
default:
/*
* Permanent failure (-EBUSY, etc.):
* unlike -EAGAIN case, the failed folio is
* removed from migration folio list and not
* retried in the next outer loop.
*/
nr_failed++;
stats->nr_thp_failed += is_thp;
stats->nr_failed_pages += nr_pages;
break;
}
}
}
nr_failed += retry;
stats->nr_thp_failed += thp_retry;
stats->nr_failed_pages += nr_retry_pages;
move:
/* Flush TLBs for all unmapped folios */
try_to_unmap_flush();
retry = 1;
for (pass = 0; pass < nr_pass && retry; pass++) {
retry = 0;
thp_retry = 0;
nr_retry_pages = 0;
dst = list_first_entry(&dst_folios, struct folio, lru);
dst2 = list_next_entry(dst, lru);
list_for_each_entry_safe(folio, folio2, &unmap_folios, lru) {
is_thp = folio_test_large(folio) && folio_test_pmd_mappable(folio);
nr_pages = folio_nr_pages(folio);
cond_resched();
rc = migrate_folio_move(put_new_folio, private,
folio, dst, mode,
reason, ret_folios);
/*
* The rules are:
* Success: folio will be freed
* -EAGAIN: stay on the unmap_folios list
* Other errno: put on ret_folios list
*/
switch(rc) {
case -EAGAIN:
retry++;
thp_retry += is_thp;
nr_retry_pages += nr_pages;
break;
case MIGRATEPAGE_SUCCESS:
stats->nr_succeeded += nr_pages;
stats->nr_thp_succeeded += is_thp;
break;
default:
nr_failed++;
stats->nr_thp_failed += is_thp;
stats->nr_failed_pages += nr_pages;
break;
}
dst = dst2;
dst2 = list_next_entry(dst, lru);
}
}
nr_failed += retry;
stats->nr_thp_failed += thp_retry;
stats->nr_failed_pages += nr_retry_pages;
rc = rc_saved ? : nr_failed;
out:
/* Cleanup remaining folios */
dst = list_first_entry(&dst_folios, struct folio, lru);
dst2 = list_next_entry(dst, lru);
list_for_each_entry_safe(folio, folio2, &unmap_folios, lru) {
int old_page_state = 0;
struct anon_vma *anon_vma = NULL;
__migrate_folio_extract(dst, &old_page_state, &anon_vma);
migrate_folio_undo_src(folio, old_page_state & PAGE_WAS_MAPPED,
anon_vma, true, ret_folios);
list_del(&dst->lru);
migrate_folio_undo_dst(dst, true, put_new_folio, private);
dst = dst2;
dst2 = list_next_entry(dst, lru);
}
return rc;
}
static int migrate_pages_sync(struct list_head *from, new_folio_t get_new_folio,
free_folio_t put_new_folio, unsigned long private,
enum migrate_mode mode, int reason,
struct list_head *ret_folios, struct list_head *split_folios,
struct migrate_pages_stats *stats)
{
int rc, nr_failed = 0;
LIST_HEAD(folios);
struct migrate_pages_stats astats;
memset(&astats, 0, sizeof(astats));
/* Try to migrate in batch with MIGRATE_ASYNC mode firstly */
rc = migrate_pages_batch(from, get_new_folio, put_new_folio, private, MIGRATE_ASYNC,
reason, &folios, split_folios, &astats,
NR_MAX_MIGRATE_ASYNC_RETRY);
stats->nr_succeeded += astats.nr_succeeded;
stats->nr_thp_succeeded += astats.nr_thp_succeeded;
stats->nr_thp_split += astats.nr_thp_split;
stats->nr_split += astats.nr_split;
if (rc < 0) {
stats->nr_failed_pages += astats.nr_failed_pages;
stats->nr_thp_failed += astats.nr_thp_failed;
list_splice_tail(&folios, ret_folios);
return rc;
}
stats->nr_thp_failed += astats.nr_thp_split;
/*
* Do not count rc, as pages will be retried below.
* Count nr_split only, since it includes nr_thp_split.
*/
nr_failed += astats.nr_split;
/*
* Fall back to migrate all failed folios one by one synchronously. All
* failed folios except split THPs will be retried, so their failure
* isn't counted
*/
list_splice_tail_init(&folios, from);
while (!list_empty(from)) {
list_move(from->next, &folios);
rc = migrate_pages_batch(&folios, get_new_folio, put_new_folio,
private, mode, reason, ret_folios,
split_folios, stats, NR_MAX_MIGRATE_SYNC_RETRY);
list_splice_tail_init(&folios, ret_folios);
if (rc < 0)
return rc;
nr_failed += rc;
}
return nr_failed;
}
/*
* migrate_pages - migrate the folios specified in a list, to the free folios
* supplied as the target for the page migration
*
* @from: The list of folios to be migrated.
* @get_new_folio: The function used to allocate free folios to be used
* as the target of the folio migration.
* @put_new_folio: The function used to free target folios if migration
* fails, or NULL if no special handling is necessary.
* @private: Private data to be passed on to get_new_folio()
* @mode: The migration mode that specifies the constraints for
* folio migration, if any.
* @reason: The reason for folio migration.
* @ret_succeeded: Set to the number of folios migrated successfully if
* the caller passes a non-NULL pointer.
*
* The function returns after NR_MAX_MIGRATE_PAGES_RETRY attempts or if no folios
* are movable any more because the list has become empty or no retryable folios
* exist any more. It is caller's responsibility to call putback_movable_pages()
* only if ret != 0.
*
* Returns the number of {normal folio, large folio, hugetlb} that were not
* migrated, or an error code. The number of large folio splits will be
* considered as the number of non-migrated large folio, no matter how many
* split folios of the large folio are migrated successfully.
*/
int migrate_pages(struct list_head *from, new_folio_t get_new_folio,
free_folio_t put_new_folio, unsigned long private,
enum migrate_mode mode, int reason, unsigned int *ret_succeeded)
{
int rc, rc_gather;
int nr_pages;
struct folio *folio, *folio2;
LIST_HEAD(folios);
LIST_HEAD(ret_folios);
LIST_HEAD(split_folios);
struct migrate_pages_stats stats;
trace_mm_migrate_pages_start(mode, reason);
memset(&stats, 0, sizeof(stats));
rc_gather = migrate_hugetlbs(from, get_new_folio, put_new_folio, private,
mode, reason, &stats, &ret_folios);
if (rc_gather < 0)
goto out;
again:
nr_pages = 0;
list_for_each_entry_safe(folio, folio2, from, lru) {
/* Retried hugetlb folios will be kept in list */
if (folio_test_hugetlb(folio)) {
list_move_tail(&folio->lru, &ret_folios);
continue;
}
nr_pages += folio_nr_pages(folio);
if (nr_pages >= NR_MAX_BATCHED_MIGRATION)
break;
}
if (nr_pages >= NR_MAX_BATCHED_MIGRATION)
list_cut_before(&folios, from, &folio2->lru);
else
list_splice_init(from, &folios);
if (mode == MIGRATE_ASYNC)
rc = migrate_pages_batch(&folios, get_new_folio, put_new_folio,
private, mode, reason, &ret_folios,
&split_folios, &stats,
NR_MAX_MIGRATE_PAGES_RETRY);
else
rc = migrate_pages_sync(&folios, get_new_folio, put_new_folio,
private, mode, reason, &ret_folios,
&split_folios, &stats);
list_splice_tail_init(&folios, &ret_folios);
if (rc < 0) {
rc_gather = rc;
list_splice_tail(&split_folios, &ret_folios);
goto out;
}
if (!list_empty(&split_folios)) {
/*
* Failure isn't counted since all split folios of a large folio
* is counted as 1 failure already. And, we only try to migrate
* with minimal effort, force MIGRATE_ASYNC mode and retry once.
*/
migrate_pages_batch(&split_folios, get_new_folio,
put_new_folio, private, MIGRATE_ASYNC, reason,
&ret_folios, NULL, &stats, 1);
list_splice_tail_init(&split_folios, &ret_folios);
}
rc_gather += rc;
if (!list_empty(from))
goto again;
out:
/*
* Put the permanent failure folio back to migration list, they
* will be put back to the right list by the caller.
*/
list_splice(&ret_folios, from);
/*
* Return 0 in case all split folios of fail-to-migrate large folios
* are migrated successfully.
*/
if (list_empty(from))
rc_gather = 0;
count_vm_events(PGMIGRATE_SUCCESS, stats.nr_succeeded);
count_vm_events(PGMIGRATE_FAIL, stats.nr_failed_pages);
count_vm_events(THP_MIGRATION_SUCCESS, stats.nr_thp_succeeded);
count_vm_events(THP_MIGRATION_FAIL, stats.nr_thp_failed);
count_vm_events(THP_MIGRATION_SPLIT, stats.nr_thp_split);
trace_mm_migrate_pages(stats.nr_succeeded, stats.nr_failed_pages,
stats.nr_thp_succeeded, stats.nr_thp_failed,
stats.nr_thp_split, stats.nr_split, mode,
reason);
if (ret_succeeded)
*ret_succeeded = stats.nr_succeeded;
return rc_gather;
}
struct folio *alloc_migration_target(struct folio *src, unsigned long private)
{
struct migration_target_control *mtc;
gfp_t gfp_mask;
unsigned int order = 0;
int nid;
int zidx;
mtc = (struct migration_target_control *)private;
gfp_mask = mtc->gfp_mask;
nid = mtc->nid;
if (nid == NUMA_NO_NODE)
nid = folio_nid(src);
if (folio_test_hugetlb(src)) {
struct hstate *h = folio_hstate(src);
gfp_mask = htlb_modify_alloc_mask(h, gfp_mask);
return alloc_hugetlb_folio_nodemask(h, nid,
mtc->nmask, gfp_mask);
}
if (folio_test_large(src)) {
/*
* clear __GFP_RECLAIM to make the migration callback
* consistent with regular THP allocations.
*/
gfp_mask &= ~__GFP_RECLAIM;
gfp_mask |= GFP_TRANSHUGE;
order = folio_order(src);
}
zidx = zone_idx(folio_zone(src));
if (is_highmem_idx(zidx) || zidx == ZONE_MOVABLE)
gfp_mask |= __GFP_HIGHMEM;
return __folio_alloc(gfp_mask, order, nid, mtc->nmask);
}
#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 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, const void __user *p,
int node, struct list_head *pagelist, bool migrate_all)
{
struct vm_area_struct *vma;
unsigned long addr;
struct page *page;
struct folio *folio;
int err;
mmap_read_lock(mm);
addr = (unsigned long)untagged_addr_remote(mm, p);
err = -EFAULT;
vma = vma_lookup(mm, addr);
if (!vma || !vma_migratable(vma))
goto out;
/* FOLL_DUMP to ignore special (like zero) pages */
page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
err = PTR_ERR(page);
if (IS_ERR(page))
goto out;
err = -ENOENT;
if (!page)
goto out;
folio = page_folio(page);
if (folio_is_zone_device(folio))
goto out_putfolio;
err = 0;
if (folio_nid(folio) == node)
goto out_putfolio;
err = -EACCES;
if (page_mapcount(page) > 1 && !migrate_all)
goto out_putfolio;
err = -EBUSY;
if (folio_test_hugetlb(folio)) {
if (isolate_hugetlb(folio, pagelist))
err = 1;
} else {
if (!folio_isolate_lru(folio))
goto out_putfolio;
err = 1;
list_add_tail(&folio->lru, pagelist);
node_stat_mod_folio(folio,
NR_ISOLATED_ANON + folio_is_file_lru(folio),
folio_nr_pages(folio));
}
out_putfolio:
/*
* Either remove the duplicate refcount from folio_isolate_lru()
* or drop the folio ref if it was not isolated.
*/
folio_put(folio);
out:
mmap_read_unlock(mm);
return err;
}
static int move_pages_and_store_status(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(pagelist, node);
if (err) {
/*
* Positive err means the number of failed
* pages to migrate. Since we are going to
* abort and return the number of non-migrated
* pages, so need to include the rest of the
* nr_pages that have not been attempted as
* well.
*/
if (err > 0)
err += nr_pages - i;
return err;
}
return store_status(status, start, node, i - start);
}
/*
* Migrate an array of page address onto an array of nodes and fill
* the corresponding array of status.
*/
static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
unsigned long nr_pages,
const void __user * __user *pages,
const int __user *nodes,
int __user *status, int flags)
{
compat_uptr_t __user *compat_pages = (void __user *)pages;
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;
int node;
err = -EFAULT;
if (in_compat_syscall()) {
compat_uptr_t cp;
if (get_user(cp, compat_pages + i))
goto out_flush;
p = compat_ptr(cp);
} else {
if (get_user(p, pages + i))
goto out_flush;
}
if (get_user(node, nodes + i))
goto out_flush;
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(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, p, current_node, &pagelist,
flags & MPOL_MF_MOVE_ALL);
if (err > 0) {
/* The page is successfully queued for migration */
continue;
}
/*
* The move_pages() man page does not have an -EEXIST choice, so
* use -EFAULT instead.
*/
if (err == -EEXIST)
err = -EFAULT;
/*
* If the page is already on the target node (!err), store the
* node, otherwise, store the err.
*/
err = store_status(status, i, err ? : current_node, 1);
if (err)
goto out_flush;
err = move_pages_and_store_status(current_node, &pagelist,
status, start, i, nr_pages);
if (err) {
/* We have accounted for page i */
if (err > 0)
err--;
goto out;
}
current_node = NUMA_NO_NODE;
}
out_flush:
/* Make sure we do not overwrite the existing error */
err1 = move_pages_and_store_status(current_node, &pagelist,
status, start, i, nr_pages);
if (err >= 0)
err = err1;
out:
lru_cache_enable();
return err;
}
/*
* Determine the nodes of an array of pages and store it in an array of status.
*/
static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
const void __user **pages, int *status)
{
unsigned long i;
mmap_read_lock(mm);
for (i = 0; i < nr_pages; i++) {
unsigned long addr = (unsigned long)(*pages);
struct vm_area_struct *vma;
struct page *page;
int err = -EFAULT;
vma = vma_lookup(mm, addr);
if (!vma)
goto set_status;
/* FOLL_DUMP to ignore special (like zero) pages */
page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
err = PTR_ERR(page);
if (IS_ERR(page))
goto set_status;
err = -ENOENT;
if (!page)
goto set_status;
if (!is_zone_device_page(page))
err = page_to_nid(page);
put_page(page);
set_status:
*status = err;
pages++;
status++;
}
mmap_read_unlock(mm);
}
static int get_compat_pages_array(const void __user *chunk_pages[],
const void __user * __user *pages,
unsigned long chunk_nr)
{
compat_uptr_t __user *pages32 = (compat_uptr_t __user *)pages;
compat_uptr_t p;
int i;
for (i = 0; i < chunk_nr; i++) {
if (get_user(p, pages32 + i))
return -EFAULT;
chunk_pages[i] = compat_ptr(p);
}
return 0;
}
/*
* Determine the nodes of a user array of pages and store it in
* a user array of status.
*/
static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
const void __user * __user *pages,
int __user *status)
{
#define DO_PAGES_STAT_CHUNK_NR 16UL
const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
int chunk_status[DO_PAGES_STAT_CHUNK_NR];
while (nr_pages) {
unsigned long chunk_nr = min(nr_pages, DO_PAGES_STAT_CHUNK_NR);
if (in_compat_syscall()) {
if (get_compat_pages_array(chunk_pages, pages,
chunk_nr))
break;
} else {
if (copy_from_user(chunk_pages, pages,
chunk_nr * sizeof(*chunk_pages)))
break;
}
do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
break;
pages += chunk_nr;
status += chunk_nr;
nr_pages -= chunk_nr;
}
return nr_pages ? -EFAULT : 0;
}
static struct mm_struct *find_mm_struct(pid_t pid, nodemask_t *mem_nodes)
{
struct task_struct *task;
struct mm_struct *mm;
/*
* There is no need to check if current process has the right to modify
* the specified process when they are same.
*/
if (!pid) {
mmget(current->mm);
*mem_nodes = cpuset_mems_allowed(current);
return current->mm;
}
/* Find the mm_struct */
rcu_read_lock();
task = find_task_by_vpid(pid);
if (!task) {
rcu_read_unlock();
return ERR_PTR(-ESRCH);
}
get_task_struct(task);
/*
* Check if this process has the right to modify the specified
* process. Use the regular "ptrace_may_access()" checks.
*/
if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
rcu_read_unlock();
mm = ERR_PTR(-EPERM);
goto out;
}
rcu_read_unlock();
mm = ERR_PTR(security_task_movememory(task));
if (IS_ERR(mm))
goto out;
*mem_nodes = cpuset_mems_allowed(task);
mm = get_task_mm(task);
out:
put_task_struct(task);
if (!mm)
mm = ERR_PTR(-EINVAL);
return mm;
}
/*
* Move a list of pages in the address space of the currently executing
* process.
*/
static int kernel_move_pages(pid_t pid, unsigned long nr_pages,
const void __user * __user *pages,
const int __user *nodes,
int __user *status, int flags)
{
struct mm_struct *mm;
int err;
nodemask_t task_nodes;
/* Check flags */
if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
return -EINVAL;
if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
return -EPERM;
mm = find_mm_struct(pid, &task_nodes);
if (IS_ERR(mm))
return PTR_ERR(mm);
if (nodes)
err = do_pages_move(mm, task_nodes, nr_pages, pages,
nodes, status, flags);
else
err = do_pages_stat(mm, nr_pages, pages, status);
mmput(mm);
return err;
}
SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
const void __user * __user *, pages,
const int __user *, nodes,
int __user *, status, int, flags)
{
return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags);
}
#ifdef CONFIG_NUMA_BALANCING
/*
* Returns true if this is a safe migration target node for misplaced NUMA
* pages. Currently it only checks the watermarks which is crude.
*/
static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
unsigned long nr_migrate_pages)
{
int z;
for (z = pgdat->nr_zones - 1; z >= 0; z--) {
struct zone *zone = pgdat->node_zones + z;
if (!managed_zone(zone))
continue;
/* Avoid waking kswapd by allocating pages_to_migrate pages. */
if (!zone_watermark_ok(zone, 0,
high_wmark_pages(zone) +
nr_migrate_pages,
ZONE_MOVABLE, 0))
continue;
return true;
}
return false;
}
static struct folio *alloc_misplaced_dst_folio(struct folio *src,
unsigned long data)
{
int nid = (int) data;
int order = folio_order(src);
gfp_t gfp = __GFP_THISNODE;
if (order > 0)
gfp |= GFP_TRANSHUGE_LIGHT;
else {
gfp |= GFP_HIGHUSER_MOVABLE | __GFP_NOMEMALLOC | __GFP_NORETRY |
__GFP_NOWARN;
gfp &= ~__GFP_RECLAIM;
}
return __folio_alloc_node(gfp, order, nid);
}
static int numamigrate_isolate_folio(pg_data_t *pgdat, struct folio *folio)
{
int nr_pages = folio_nr_pages(folio);
/* Avoid migrating to a node that is nearly full */
if (!migrate_balanced_pgdat(pgdat, nr_pages)) {
int z;
if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING))
return 0;
for (z = pgdat->nr_zones - 1; z >= 0; z--) {
if (managed_zone(pgdat->node_zones + z))
break;
}
wakeup_kswapd(pgdat->node_zones + z, 0,
folio_order(folio), ZONE_MOVABLE);
return 0;
}
if (!folio_isolate_lru(folio))
return 0;
node_stat_mod_folio(folio, NR_ISOLATED_ANON + folio_is_file_lru(folio),
nr_pages);
/*
* Isolating the folio has taken another reference, so the
* caller's reference can be safely dropped without the folio
* disappearing underneath us during migration.
*/
folio_put(folio);
return 1;
}
/*
* Attempt to migrate a misplaced folio to the specified destination
* node. Caller is expected to have an elevated reference count on
* the folio that will be dropped by this function before returning.
*/
int migrate_misplaced_folio(struct folio *folio, struct vm_area_struct *vma,
int node)
{
pg_data_t *pgdat = NODE_DATA(node);
int isolated;
int nr_remaining;
unsigned int nr_succeeded;
LIST_HEAD(migratepages);
int nr_pages = folio_nr_pages(folio);
/*
* Don't migrate file folios that are mapped in multiple processes
* with execute permissions as they are probably shared libraries.
* To check if the folio is shared, ideally we want to make sure
* every page is mapped to the same process. Doing that is very
* expensive, so check the estimated mapcount of the folio instead.
*/
if (folio_estimated_sharers(folio) != 1 && folio_is_file_lru(folio) &&
(vma->vm_flags & VM_EXEC))
goto out;
/*
* Also do not migrate dirty folios as not all filesystems can move
* dirty folios in MIGRATE_ASYNC mode which is a waste of cycles.
*/
if (folio_is_file_lru(folio) && folio_test_dirty(folio))
goto out;
isolated = numamigrate_isolate_folio(pgdat, folio);
if (!isolated)
goto out;
list_add(&folio->lru, &migratepages);
nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_folio,
NULL, node, MIGRATE_ASYNC,
MR_NUMA_MISPLACED, &nr_succeeded);
if (nr_remaining) {
if (!list_empty(&migratepages)) {
list_del(&folio->lru);
node_stat_mod_folio(folio, NR_ISOLATED_ANON +
folio_is_file_lru(folio), -nr_pages);
folio_putback_lru(folio);
}
isolated = 0;
}
if (nr_succeeded) {
count_vm_numa_events(NUMA_PAGE_MIGRATE, nr_succeeded);
if (!node_is_toptier(folio_nid(folio)) && node_is_toptier(node))
mod_node_page_state(pgdat, PGPROMOTE_SUCCESS,
nr_succeeded);
}
BUG_ON(!list_empty(&migratepages));
return isolated;
out:
folio_put(folio);
return 0;
}
#endif /* CONFIG_NUMA_BALANCING */
#endif /* CONFIG_NUMA */