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-rw-r--r--mm/migrate.c2605
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diff --git a/mm/migrate.c b/mm/migrate.c
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+++ b/mm/migrate.c
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+// 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
+ * __PageMovable 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(new, vma, pvmw.address,
+ rmap_flags);
+ else
+ page_dup_file_rmap(new, true);
+ set_huge_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte,
+ 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);
+ long entries, i;
+
+ 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);
+ }
+ entries = nr;
+ } else {
+ VM_BUG_ON_FOLIO(folio_test_swapcache(folio), folio);
+ entries = 1;
+ }
+
+ /* 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);
+ }
+
+ /* Swap cache still stores N entries instead of a high-order entry */
+ for (i = 0; i < entries; i++) {
+ xas_store(&xas, newfolio);
+ xas_next(&xas);
+ }
+
+ /*
+ * 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 = 2 + folio_has_private(src);
+ if (!folio_ref_freeze(src, expected_count)) {
+ xas_unlock_irq(&xas);
+ return -EAGAIN;
+ }
+
+ dst->index = src->index;
+ dst->mapping = src->mapping;
+
+ folio_get(dst);
+
+ xas_store(&xas, dst);
+
+ folio_ref_unfreeze(src, expected_count - 1);
+
+ xas_unlock_irq(&xas);
+
+ return MIGRATEPAGE_SUCCESS;
+}
+
+/*
+ * Copy the flags and some other ancillary information
+ */
+void folio_migrate_flags(struct folio *newfolio, struct folio *folio)
+{
+ int cpupid;
+
+ if (folio_test_error(folio))
+ folio_set_error(newfolio);
+ if (folio_test_referenced(folio))
+ folio_set_referenced(newfolio);
+ if (folio_test_uptodate(folio))
+ folio_mark_uptodate(newfolio);
+ if (folio_test_clear_active(folio)) {
+ VM_BUG_ON_FOLIO(folio_test_unevictable(folio), folio);
+ folio_set_active(newfolio);
+ } else if (folio_test_clear_unevictable(folio))
+ folio_set_unevictable(newfolio);
+ if (folio_test_workingset(folio))
+ folio_set_workingset(newfolio);
+ if (folio_test_checked(folio))
+ folio_set_checked(newfolio);
+ /*
+ * PG_anon_exclusive (-> PG_mappedtodisk) is always migrated via
+ * migration entries. We can still have PG_anon_exclusive set on an
+ * effectively unmapped and unreferenced first sub-pages of an
+ * anonymous THP: we can simply copy it here via PG_mappedtodisk.
+ */
+ if (folio_test_mappedtodisk(folio))
+ folio_set_mappedtodisk(newfolio);
+
+ /* Move dirty on pages not done by folio_migrate_mapping() */
+ if (folio_test_dirty(folio))
+ folio_set_dirty(newfolio);
+
+ if (folio_test_young(folio))
+ folio_set_young(newfolio);
+ if (folio_test_idle(folio))
+ folio_set_idle(newfolio);
+
+ /*
+ * Copy NUMA information to the new page, to prevent over-eager
+ * future migrations of this same page.
+ */
+ cpupid = page_cpupid_xchg_last(&folio->page, -1);
+ /*
+ * For memory tiering mode, when migrate between slow and fast
+ * memory node, reset cpupid, because that is used to record
+ * page access time in slow memory node.
+ */
+ if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) {
+ bool f_toptier = node_is_toptier(page_to_nid(&folio->page));
+ bool t_toptier = node_is_toptier(page_to_nid(&newfolio->page));
+
+ if (f_toptier != t_toptier)
+ cpupid = -1;
+ }
+ page_cpupid_xchg_last(&newfolio->page, cpupid);
+
+ folio_migrate_ksm(newfolio, folio);
+ /*
+ * Please do not reorder this without considering how mm/ksm.c's
+ * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
+ */
+ if (folio_test_swapcache(folio))
+ folio_clear_swapcache(folio);
+ folio_clear_private(folio);
+
+ /* page->private contains hugetlb specific flags */
+ if (!folio_test_hugetlb(folio))
+ folio->private = NULL;
+
+ /*
+ * If any waiters have accumulated on the new page then
+ * wake them up.
+ */
+ if (folio_test_writeback(newfolio))
+ folio_end_writeback(newfolio);
+
+ /*
+ * PG_readahead shares the same bit with PG_reclaim. The above
+ * end_page_writeback() may clear PG_readahead mistakenly, so set the
+ * bit after that.
+ */
+ if (folio_test_readahead(folio))
+ folio_set_readahead(newfolio);
+
+ folio_copy_owner(newfolio, folio);
+
+ if (!folio_test_hugetlb(folio))
+ mem_cgroup_migrate(folio, newfolio);
+}
+EXPORT_SYMBOL(folio_migrate_flags);
+
+void folio_migrate_copy(struct folio *newfolio, struct folio *folio)
+{
+ folio_copy(newfolio, folio);
+ folio_migrate_flags(newfolio, folio);
+}
+EXPORT_SYMBOL(folio_migrate_copy);
+
+/************************************************************
+ * Migration functions
+ ***********************************************************/
+
+int migrate_folio_extra(struct address_space *mapping, struct folio *dst,
+ struct folio *src, enum migrate_mode mode, int extra_count)
+{
+ int rc;
+
+ BUG_ON(folio_test_writeback(src)); /* Writeback must be complete */
+
+ rc = folio_migrate_mapping(mapping, dst, src, extra_count);
+
+ if (rc != MIGRATEPAGE_SUCCESS)
+ return rc;
+
+ if (mode != MIGRATE_SYNC_NO_COPY)
+ folio_migrate_copy(dst, src);
+ else
+ folio_migrate_flags(dst, src);
+ return MIGRATEPAGE_SUCCESS;
+}
+
+/**
+ * migrate_folio() - Simple folio migration.
+ * @mapping: The address_space containing the folio.
+ * @dst: The folio to migrate the data to.
+ * @src: The folio containing the current data.
+ * @mode: How to migrate the page.
+ *
+ * Common logic to directly migrate a single LRU folio suitable for
+ * folios that do not use PagePrivate/PagePrivate2.
+ *
+ * Folios are locked upon entry and exit.
+ */
+int migrate_folio(struct address_space *mapping, struct folio *dst,
+ struct folio *src, enum migrate_mode mode)
+{
+ return migrate_folio_extra(mapping, dst, src, mode, 0);
+}
+EXPORT_SYMBOL(migrate_folio);
+
+#ifdef CONFIG_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 = !__PageMovable(&src->page);
+
+ VM_BUG_ON_FOLIO(!folio_test_locked(src), src);
+ VM_BUG_ON_FOLIO(!folio_test_locked(dst), dst);
+
+ if (likely(is_lru)) {
+ struct address_space *mapping = folio_mapping(src);
+
+ if (!mapping)
+ rc = migrate_folio(mapping, dst, src, mode);
+ else if (mapping->a_ops->migrate_folio)
+ /*
+ * Most folios have a mapping and most filesystems
+ * provide a migrate_folio callback. Anonymous folios
+ * are part of swap space which also has its own
+ * migrate_folio callback. This is the most common path
+ * for page migration.
+ */
+ rc = mapping->a_ops->migrate_folio(mapping, dst, src,
+ mode);
+ else
+ rc = fallback_migrate_folio(mapping, dst, src, mode);
+ } else {
+ const struct movable_operations *mops;
+
+ /*
+ * In case of non-lru page, it could be released after
+ * isolation step. In that case, we shouldn't try migration.
+ */
+ VM_BUG_ON_FOLIO(!folio_test_isolated(src), src);
+ if (!folio_test_movable(src)) {
+ rc = MIGRATEPAGE_SUCCESS;
+ folio_clear_isolated(src);
+ goto out;
+ }
+
+ mops = 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 (__PageMovable(&src->page)) {
+ VM_BUG_ON_FOLIO(!folio_test_isolated(src), src);
+
+ /*
+ * We clear PG_movable under page_lock so any compactor
+ * cannot try to migrate this page.
+ */
+ folio_clear_isolated(src);
+ }
+
+ /*
+ * Anonymous and movable src->mapping will be cleared by
+ * free_pages_prepare so don't reset it here for keeping
+ * the type to work PageAnon, for example.
+ */
+ if (!folio_mapping_flags(src))
+ src->mapping = NULL;
+
+ if (likely(!folio_is_zone_device(dst)))
+ flush_dcache_folio(dst);
+ }
+out:
+ return rc;
+}
+
+/*
+ * To record some information during migration, we use unused private
+ * field of struct folio of the newly allocated destination folio.
+ * This is safe because nobody is using it except us.
+ */
+enum {
+ PAGE_WAS_MAPPED = BIT(0),
+ PAGE_WAS_MLOCKED = BIT(1),
+ PAGE_OLD_STATES = PAGE_WAS_MAPPED | PAGE_WAS_MLOCKED,
+};
+
+static void __migrate_folio_record(struct folio *dst,
+ int old_page_state,
+ struct anon_vma *anon_vma)
+{
+ dst->private = (void *)anon_vma + old_page_state;
+}
+
+static void __migrate_folio_extract(struct folio *dst,
+ int *old_page_state,
+ struct anon_vma **anon_vmap)
+{
+ unsigned long private = (unsigned long)dst->private;
+
+ *anon_vmap = (struct anon_vma *)(private & ~PAGE_OLD_STATES);
+ *old_page_state = private & PAGE_OLD_STATES;
+ 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 __PageMovable
+ */
+ 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 = !__PageMovable(&src->page);
+ 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 = !__PageMovable(&src->page);
+ 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 */
+};
+
+/*
+ * 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;
+ 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_thp = folio_test_large(folio) && 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++;
+ 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 (folio_test_large(folio) && !nosplit) {
+ int ret = try_split_folio(folio, split_folios);
+
+ if (!ret) {
+ stats->nr_thp_split += is_thp;
+ break;
+ } else if (reason == MR_LONGTERM_PIN &&
+ ret == -EAGAIN) {
+ /*
+ * Try again to split large folio to
+ * mitigate the failure of longterm pinning.
+ */
+ 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;
+ 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;
+ nr_failed += astats.nr_thp_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, 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 mm_struct *mm,
+ struct list_head *pagelist, int node)
+{
+ int err;
+ struct migration_target_control mtc = {
+ .nid = node,
+ .gfp_mask = GFP_HIGHUSER_MOVABLE | __GFP_THISNODE,
+ };
+
+ err = migrate_pages(pagelist, alloc_migration_target, NULL,
+ (unsigned long)&mtc, MIGRATE_SYNC, MR_SYSCALL, NULL);
+ if (err)
+ putback_movable_pages(pagelist);
+ return err;
+}
+
+/*
+ * Resolves the given address to a struct page, isolates it from the LRU and
+ * puts it to the given pagelist.
+ * Returns:
+ * errno - if the page cannot be found/isolated
+ * 0 - when it doesn't have to be migrated because it is already on the
+ * target node
+ * 1 - when it has been queued
+ */
+static int add_page_for_migration(struct mm_struct *mm, const void __user *p,
+ int node, struct list_head *pagelist, bool migrate_all)
+{
+ struct vm_area_struct *vma;
+ unsigned long addr;
+ struct page *page;
+ int err;
+ bool isolated;
+
+ 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;
+
+ if (is_zone_device_page(page))
+ goto out_putpage;
+
+ err = 0;
+ if (page_to_nid(page) == node)
+ goto out_putpage;
+
+ err = -EACCES;
+ if (page_mapcount(page) > 1 && !migrate_all)
+ goto out_putpage;
+
+ if (PageHuge(page)) {
+ if (PageHead(page)) {
+ isolated = isolate_hugetlb(page_folio(page), pagelist);
+ err = isolated ? 1 : -EBUSY;
+ }
+ } else {
+ struct page *head;
+
+ head = compound_head(page);
+ isolated = isolate_lru_page(head);
+ if (!isolated) {
+ err = -EBUSY;
+ goto out_putpage;
+ }
+
+ err = 1;
+ list_add_tail(&head->lru, pagelist);
+ mod_node_page_state(page_pgdat(head),
+ NR_ISOLATED_ANON + page_is_file_lru(head),
+ thp_nr_pages(head));
+ }
+out_putpage:
+ /*
+ * Either remove the duplicate refcount from
+ * isolate_lru_page() or drop the page ref if it was
+ * not isolated.
+ */
+ put_page(page);
+out:
+ mmap_read_unlock(mm);
+ return err;
+}
+
+static int move_pages_and_store_status(struct mm_struct *mm, int node,
+ struct list_head *pagelist, int __user *status,
+ int start, int i, unsigned long nr_pages)
+{
+ int err;
+
+ if (list_empty(pagelist))
+ return 0;
+
+ err = do_move_pages_to_node(mm, pagelist, node);
+ if (err) {
+ /*
+ * Positive err means the number of failed
+ * pages to migrate. Since we are going to
+ * abort and return the number of non-migrated
+ * pages, so need to include the rest of the
+ * nr_pages that have not been attempted as
+ * well.
+ */
+ if (err > 0)
+ err += nr_pages - i;
+ return err;
+ }
+ return store_status(status, start, node, i - start);
+}
+
+/*
+ * Migrate an array of page address onto an array of nodes and fill
+ * the corresponding array of status.
+ */
+static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
+ unsigned long nr_pages,
+ const void __user * __user *pages,
+ const int __user *nodes,
+ int __user *status, int flags)
+{
+ 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(mm, current_node,
+ &pagelist, status, start, i, nr_pages);
+ if (err)
+ goto out;
+ start = i;
+ current_node = node;
+ }
+
+ /*
+ * Errors in the page lookup or isolation are not fatal and we simply
+ * report them via status
+ */
+ err = add_page_for_migration(mm, 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(mm, current_node, &pagelist,
+ status, start, i, nr_pages);
+ if (err) {
+ /* We have accounted for page i */
+ if (err > 0)
+ err--;
+ goto out;
+ }
+ current_node = NUMA_NO_NODE;
+ }
+out_flush:
+ /* Make sure we do not overwrite the existing error */
+ err1 = move_pages_and_store_status(mm, current_node, &pagelist,
+ status, start, i, nr_pages);
+ if (err >= 0)
+ err = err1;
+out:
+ lru_cache_enable();
+ return err;
+}
+
+/*
+ * Determine the nodes of an array of pages and store it in an array of status.
+ */
+static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
+ const void __user **pages, int *status)
+{
+ unsigned long i;
+
+ mmap_read_lock(mm);
+
+ for (i = 0; i < nr_pages; i++) {
+ unsigned long addr = (unsigned long)(*pages);
+ struct vm_area_struct *vma;
+ struct page *page;
+ int err = -EFAULT;
+
+ vma = vma_lookup(mm, addr);
+ if (!vma)
+ goto set_status;
+
+ /* FOLL_DUMP to ignore special (like zero) pages */
+ page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
+
+ err = PTR_ERR(page);
+ if (IS_ERR(page))
+ goto set_status;
+
+ err = -ENOENT;
+ if (!page)
+ goto set_status;
+
+ if (!is_zone_device_page(page))
+ err = page_to_nid(page);
+
+ put_page(page);
+set_status:
+ *status = err;
+
+ pages++;
+ status++;
+ }
+
+ mmap_read_unlock(mm);
+}
+
+static int get_compat_pages_array(const void __user *chunk_pages[],
+ const void __user * __user *pages,
+ unsigned long chunk_nr)
+{
+ compat_uptr_t __user *pages32 = (compat_uptr_t __user *)pages;
+ compat_uptr_t p;
+ int i;
+
+ for (i = 0; i < chunk_nr; i++) {
+ if (get_user(p, pages32 + i))
+ return -EFAULT;
+ chunk_pages[i] = compat_ptr(p);
+ }
+
+ return 0;
+}
+
+/*
+ * Determine the nodes of a user array of pages and store it in
+ * a user array of status.
+ */
+static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
+ const void __user * __user *pages,
+ int __user *status)
+{
+#define DO_PAGES_STAT_CHUNK_NR 16UL
+ const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
+ int chunk_status[DO_PAGES_STAT_CHUNK_NR];
+
+ while (nr_pages) {
+ unsigned long chunk_nr = min(nr_pages, DO_PAGES_STAT_CHUNK_NR);
+
+ if (in_compat_syscall()) {
+ if (get_compat_pages_array(chunk_pages, pages,
+ chunk_nr))
+ break;
+ } else {
+ if (copy_from_user(chunk_pages, pages,
+ chunk_nr * sizeof(*chunk_pages)))
+ break;
+ }
+
+ do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
+
+ if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
+ break;
+
+ pages += chunk_nr;
+ status += chunk_nr;
+ nr_pages -= chunk_nr;
+ }
+ return nr_pages ? -EFAULT : 0;
+}
+
+static struct mm_struct *find_mm_struct(pid_t pid, nodemask_t *mem_nodes)
+{
+ struct task_struct *task;
+ struct mm_struct *mm;
+
+ /*
+ * There is no need to check if current process has the right to modify
+ * the specified process when they are same.
+ */
+ if (!pid) {
+ mmget(current->mm);
+ *mem_nodes = cpuset_mems_allowed(current);
+ return current->mm;
+ }
+
+ /* Find the mm_struct */
+ rcu_read_lock();
+ task = find_task_by_vpid(pid);
+ if (!task) {
+ rcu_read_unlock();
+ return ERR_PTR(-ESRCH);
+ }
+ get_task_struct(task);
+
+ /*
+ * Check if this process has the right to modify the specified
+ * process. Use the regular "ptrace_may_access()" checks.
+ */
+ if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
+ rcu_read_unlock();
+ mm = ERR_PTR(-EPERM);
+ goto out;
+ }
+ rcu_read_unlock();
+
+ mm = ERR_PTR(security_task_movememory(task));
+ if (IS_ERR(mm))
+ goto out;
+ *mem_nodes = cpuset_mems_allowed(task);
+ mm = get_task_mm(task);
+out:
+ put_task_struct(task);
+ if (!mm)
+ mm = ERR_PTR(-EINVAL);
+ return mm;
+}
+
+/*
+ * Move a list of pages in the address space of the currently executing
+ * process.
+ */
+static int kernel_move_pages(pid_t pid, unsigned long nr_pages,
+ const void __user * __user *pages,
+ const int __user *nodes,
+ int __user *status, int flags)
+{
+ struct mm_struct *mm;
+ int err;
+ nodemask_t task_nodes;
+
+ /* Check flags */
+ if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
+ return -EINVAL;
+
+ if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
+ return -EPERM;
+
+ mm = find_mm_struct(pid, &task_nodes);
+ if (IS_ERR(mm))
+ return PTR_ERR(mm);
+
+ if (nodes)
+ err = do_pages_move(mm, task_nodes, nr_pages, pages,
+ nodes, status, flags);
+ else
+ err = do_pages_stat(mm, nr_pages, pages, status);
+
+ mmput(mm);
+ return err;
+}
+
+SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
+ const void __user * __user *, pages,
+ const int __user *, nodes,
+ int __user *, status, int, flags)
+{
+ return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags);
+}
+
+#ifdef CONFIG_NUMA_BALANCING
+/*
+ * Returns true if this is a safe migration target node for misplaced NUMA
+ * pages. Currently it only checks the watermarks which is crude.
+ */
+static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
+ unsigned long nr_migrate_pages)
+{
+ int z;
+
+ for (z = pgdat->nr_zones - 1; z >= 0; z--) {
+ struct zone *zone = pgdat->node_zones + z;
+
+ if (!managed_zone(zone))
+ continue;
+
+ /* Avoid waking kswapd by allocating pages_to_migrate pages. */
+ if (!zone_watermark_ok(zone, 0,
+ high_wmark_pages(zone) +
+ nr_migrate_pages,
+ ZONE_MOVABLE, 0))
+ continue;
+ return true;
+ }
+ return false;
+}
+
+static struct 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_page(pg_data_t *pgdat, struct page *page)
+{
+ int nr_pages = thp_nr_pages(page);
+ int order = compound_order(page);
+
+ VM_BUG_ON_PAGE(order && !PageTransHuge(page), page);
+
+ /* Do not migrate THP mapped by multiple processes */
+ if (PageTransHuge(page) && total_mapcount(page) > 1)
+ return 0;
+
+ /* Avoid migrating to a node that is nearly full */
+ if (!migrate_balanced_pgdat(pgdat, nr_pages)) {
+ int z;
+
+ if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING))
+ return 0;
+ for (z = pgdat->nr_zones - 1; z >= 0; z--) {
+ if (managed_zone(pgdat->node_zones + z))
+ break;
+ }
+ wakeup_kswapd(pgdat->node_zones + z, 0, order, ZONE_MOVABLE);
+ return 0;
+ }
+
+ if (!isolate_lru_page(page))
+ return 0;
+
+ mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_is_file_lru(page),
+ nr_pages);
+
+ /*
+ * Isolating the page has taken another reference, so the
+ * caller's reference can be safely dropped without the page
+ * disappearing underneath us during migration.
+ */
+ put_page(page);
+ return 1;
+}
+
+/*
+ * Attempt to migrate a misplaced page to the specified destination
+ * node. Caller is expected to have an elevated reference count on
+ * the page that will be dropped by this function before returning.
+ */
+int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
+ int node)
+{
+ pg_data_t *pgdat = NODE_DATA(node);
+ int isolated;
+ int nr_remaining;
+ unsigned int nr_succeeded;
+ LIST_HEAD(migratepages);
+ int nr_pages = thp_nr_pages(page);
+
+ /*
+ * Don't migrate file pages that are mapped in multiple processes
+ * with execute permissions as they are probably shared libraries.
+ */
+ if (page_mapcount(page) != 1 && page_is_file_lru(page) &&
+ (vma->vm_flags & VM_EXEC))
+ goto out;
+
+ /*
+ * Also do not migrate dirty pages as not all filesystems can move
+ * dirty pages in MIGRATE_ASYNC mode which is a waste of cycles.
+ */
+ if (page_is_file_lru(page) && PageDirty(page))
+ goto out;
+
+ isolated = numamigrate_isolate_page(pgdat, page);
+ if (!isolated)
+ goto out;
+
+ list_add(&page->lru, &migratepages);
+ nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_folio,
+ NULL, node, MIGRATE_ASYNC,
+ MR_NUMA_MISPLACED, &nr_succeeded);
+ if (nr_remaining) {
+ if (!list_empty(&migratepages)) {
+ list_del(&page->lru);
+ mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
+ page_is_file_lru(page), -nr_pages);
+ putback_lru_page(page);
+ }
+ isolated = 0;
+ }
+ if (nr_succeeded) {
+ count_vm_numa_events(NUMA_PAGE_MIGRATE, nr_succeeded);
+ if (!node_is_toptier(page_to_nid(page)) && node_is_toptier(node))
+ mod_node_page_state(pgdat, PGPROMOTE_SUCCESS,
+ nr_succeeded);
+ }
+ BUG_ON(!list_empty(&migratepages));
+ return isolated;
+
+out:
+ put_page(page);
+ return 0;
+}
+#endif /* CONFIG_NUMA_BALANCING */
+#endif /* CONFIG_NUMA */