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Diffstat (limited to '')
| -rw-r--r-- | mm/migrate.c | 2605 |
1 files changed, 2605 insertions, 0 deletions
diff --git a/mm/migrate.c b/mm/migrate.c new file mode 100644 index 0000000000..b4d972d80b --- /dev/null +++ b/mm/migrate.c @@ -0,0 +1,2605 @@ +// 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 */ |