| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * Memory Migration functionality - linux/mm/migrate.c |
| * |
| * Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter |
| * |
| * Page migration was first developed in the context of the memory hotplug |
| * project. The main authors of the migration code are: |
| * |
| * IWAMOTO Toshihiro <iwamoto@valinux.co.jp> |
| * Hirokazu Takahashi <taka@valinux.co.jp> |
| * Dave Hansen <haveblue@us.ibm.com> |
| * Christoph Lameter |
| */ |
| |
| #include <linux/migrate.h> |
| #include <linux/export.h> |
| #include <linux/swap.h> |
| #include <linux/swapops.h> |
| #include <linux/pagemap.h> |
| #include <linux/buffer_head.h> |
| #include <linux/mm_inline.h> |
| #include <linux/nsproxy.h> |
| #include <linux/pagevec.h> |
| #include <linux/ksm.h> |
| #include <linux/rmap.h> |
| #include <linux/topology.h> |
| #include <linux/cpu.h> |
| #include <linux/cpuset.h> |
| #include <linux/writeback.h> |
| #include <linux/mempolicy.h> |
| #include <linux/vmalloc.h> |
| #include <linux/security.h> |
| #include <linux/backing-dev.h> |
| #include <linux/compaction.h> |
| #include <linux/syscalls.h> |
| #include <linux/compat.h> |
| #include <linux/hugetlb.h> |
| #include <linux/hugetlb_cgroup.h> |
| #include <linux/gfp.h> |
| #include <linux/pagewalk.h> |
| #include <linux/pfn_t.h> |
| #include <linux/memremap.h> |
| #include <linux/userfaultfd_k.h> |
| #include <linux/balloon_compaction.h> |
| #include <linux/mmu_notifier.h> |
| #include <linux/page_idle.h> |
| #include <linux/page_owner.h> |
| #include <linux/sched/mm.h> |
| #include <linux/ptrace.h> |
| #include <linux/oom.h> |
| #include <linux/memory.h> |
| |
| #include <asm/tlbflush.h> |
| |
| #define CREATE_TRACE_POINTS |
| #include <trace/events/migrate.h> |
| |
| #include "internal.h" |
| |
| int isolate_movable_page(struct page *page, isolate_mode_t mode) |
| { |
| struct address_space *mapping; |
| |
| /* |
| * Avoid burning cycles with pages that are yet under __free_pages(), |
| * or just got freed under us. |
| * |
| * In case we 'win' a race for a movable page being freed under us and |
| * raise its refcount preventing __free_pages() from doing its job |
| * the put_page() at the end of this block will take care of |
| * release this page, thus avoiding a nasty leakage. |
| */ |
| if (unlikely(!get_page_unless_zero(page))) |
| goto out; |
| |
| /* |
| * Check PageMovable before holding a PG_lock because page's owner |
| * assumes anybody doesn't touch PG_lock of newly allocated page |
| * so unconditionally grabbing the lock ruins page's owner side. |
| */ |
| if (unlikely(!__PageMovable(page))) |
| goto out_putpage; |
| /* |
| * As movable pages are not isolated from LRU lists, concurrent |
| * compaction threads can race against page migration functions |
| * as well as race against the releasing a page. |
| * |
| * In order to avoid having an already isolated movable page |
| * being (wrongly) re-isolated while it is under migration, |
| * or to avoid attempting to isolate pages being released, |
| * lets be sure we have the page lock |
| * before proceeding with the movable page isolation steps. |
| */ |
| if (unlikely(!trylock_page(page))) |
| goto out_putpage; |
| |
| if (!PageMovable(page) || PageIsolated(page)) |
| goto out_no_isolated; |
| |
| mapping = page_mapping(page); |
| VM_BUG_ON_PAGE(!mapping, page); |
| |
| if (!mapping->a_ops->isolate_page(page, mode)) |
| goto out_no_isolated; |
| |
| /* Driver shouldn't use PG_isolated bit of page->flags */ |
| WARN_ON_ONCE(PageIsolated(page)); |
| __SetPageIsolated(page); |
| unlock_page(page); |
| |
| return 0; |
| |
| out_no_isolated: |
| unlock_page(page); |
| out_putpage: |
| put_page(page); |
| out: |
| return -EBUSY; |
| } |
| |
| static void putback_movable_page(struct page *page) |
| { |
| struct address_space *mapping; |
| |
| mapping = page_mapping(page); |
| mapping->a_ops->putback_page(page); |
| __ClearPageIsolated(page); |
| } |
| |
| /* |
| * Put previously isolated pages back onto the appropriate lists |
| * from where they were once taken off for compaction/migration. |
| * |
| * This function shall be used whenever the isolated pageset has been |
| * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range() |
| * and isolate_huge_page(). |
| */ |
| void putback_movable_pages(struct list_head *l) |
| { |
| struct page *page; |
| struct page *page2; |
| |
| list_for_each_entry_safe(page, page2, l, lru) { |
| if (unlikely(PageHuge(page))) { |
| putback_active_hugepage(page); |
| continue; |
| } |
| list_del(&page->lru); |
| /* |
| * We isolated non-lru movable page so here we can use |
| * __PageMovable because LRU page's mapping cannot have |
| * PAGE_MAPPING_MOVABLE. |
| */ |
| if (unlikely(__PageMovable(page))) { |
| VM_BUG_ON_PAGE(!PageIsolated(page), page); |
| lock_page(page); |
| if (PageMovable(page)) |
| putback_movable_page(page); |
| else |
| __ClearPageIsolated(page); |
| unlock_page(page); |
| put_page(page); |
| } else { |
| mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + |
| page_is_file_lru(page), -thp_nr_pages(page)); |
| putback_lru_page(page); |
| } |
| } |
| } |
| |
| /* |
| * Restore a potential migration pte to a working pte entry |
| */ |
| static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma, |
| unsigned long addr, void *old) |
| { |
| struct page_vma_mapped_walk pvmw = { |
| .page = old, |
| .vma = vma, |
| .address = addr, |
| .flags = PVMW_SYNC | PVMW_MIGRATION, |
| }; |
| struct page *new; |
| pte_t pte; |
| swp_entry_t entry; |
| |
| VM_BUG_ON_PAGE(PageTail(page), page); |
| while (page_vma_mapped_walk(&pvmw)) { |
| if (PageKsm(page)) |
| new = page; |
| else |
| new = page - pvmw.page->index + |
| linear_page_index(vma, pvmw.address); |
| |
| #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION |
| /* PMD-mapped THP migration entry */ |
| if (!pvmw.pte) { |
| VM_BUG_ON_PAGE(PageHuge(page) || !PageTransCompound(page), page); |
| remove_migration_pmd(&pvmw, new); |
| continue; |
| } |
| #endif |
| |
| get_page(new); |
| pte = pte_mkold(mk_pte(new, READ_ONCE(vma->vm_page_prot))); |
| if (pte_swp_soft_dirty(*pvmw.pte)) |
| pte = pte_mksoft_dirty(pte); |
| |
| /* |
| * Recheck VMA as permissions can change since migration started |
| */ |
| entry = pte_to_swp_entry(*pvmw.pte); |
| if (is_writable_migration_entry(entry)) |
| pte = maybe_mkwrite(pte, vma); |
| else if (pte_swp_uffd_wp(*pvmw.pte)) |
| pte = pte_mkuffd_wp(pte); |
| |
| if (unlikely(is_device_private_page(new))) { |
| if (pte_write(pte)) |
| entry = make_writable_device_private_entry( |
| page_to_pfn(new)); |
| else |
| entry = make_readable_device_private_entry( |
| page_to_pfn(new)); |
| pte = swp_entry_to_pte(entry); |
| if (pte_swp_soft_dirty(*pvmw.pte)) |
| pte = pte_swp_mksoft_dirty(pte); |
| if (pte_swp_uffd_wp(*pvmw.pte)) |
| pte = pte_swp_mkuffd_wp(pte); |
| } |
| |
| #ifdef CONFIG_HUGETLB_PAGE |
| if (PageHuge(new)) { |
| unsigned int shift = huge_page_shift(hstate_vma(vma)); |
| |
| pte = pte_mkhuge(pte); |
| pte = arch_make_huge_pte(pte, shift, vma->vm_flags); |
| set_huge_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte); |
| if (PageAnon(new)) |
| hugepage_add_anon_rmap(new, vma, pvmw.address); |
| else |
| page_dup_rmap(new, true); |
| } else |
| #endif |
| { |
| set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte); |
| |
| if (PageAnon(new)) |
| page_add_anon_rmap(new, vma, pvmw.address, false); |
| else |
| page_add_file_rmap(new, false); |
| } |
| if (vma->vm_flags & VM_LOCKED && !PageTransCompound(new)) |
| mlock_vma_page(new); |
| |
| if (PageTransHuge(page) && PageMlocked(page)) |
| clear_page_mlock(page); |
| |
| /* No need to invalidate - it was non-present before */ |
| update_mmu_cache(vma, pvmw.address, pvmw.pte); |
| } |
| |
| return true; |
| } |
| |
| /* |
| * Get rid of all migration entries and replace them by |
| * references to the indicated page. |
| */ |
| void remove_migration_ptes(struct page *old, struct page *new, bool locked) |
| { |
| struct rmap_walk_control rwc = { |
| .rmap_one = remove_migration_pte, |
| .arg = old, |
| }; |
| |
| if (locked) |
| rmap_walk_locked(new, &rwc); |
| else |
| rmap_walk(new, &rwc); |
| } |
| |
| /* |
| * Something used the pte of a page under migration. We need to |
| * get to the page and wait until migration is finished. |
| * When we return from this function the fault will be retried. |
| */ |
| void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep, |
| spinlock_t *ptl) |
| { |
| pte_t pte; |
| swp_entry_t entry; |
| struct page *page; |
| |
| spin_lock(ptl); |
| pte = *ptep; |
| if (!is_swap_pte(pte)) |
| goto out; |
| |
| entry = pte_to_swp_entry(pte); |
| if (!is_migration_entry(entry)) |
| goto out; |
| |
| page = pfn_swap_entry_to_page(entry); |
| page = compound_head(page); |
| |
| /* |
| * Once page cache replacement of page migration started, page_count |
| * is zero; but we must not call put_and_wait_on_page_locked() without |
| * a ref. Use get_page_unless_zero(), and just fault again if it fails. |
| */ |
| if (!get_page_unless_zero(page)) |
| goto out; |
| pte_unmap_unlock(ptep, ptl); |
| put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE); |
| return; |
| out: |
| pte_unmap_unlock(ptep, ptl); |
| } |
| |
| void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, |
| unsigned long address) |
| { |
| spinlock_t *ptl = pte_lockptr(mm, pmd); |
| pte_t *ptep = pte_offset_map(pmd, address); |
| __migration_entry_wait(mm, ptep, ptl); |
| } |
| |
| void migration_entry_wait_huge(struct vm_area_struct *vma, |
| struct mm_struct *mm, pte_t *pte) |
| { |
| spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte); |
| __migration_entry_wait(mm, pte, ptl); |
| } |
| |
| #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION |
| void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd) |
| { |
| spinlock_t *ptl; |
| struct page *page; |
| |
| ptl = pmd_lock(mm, pmd); |
| if (!is_pmd_migration_entry(*pmd)) |
| goto unlock; |
| page = pfn_swap_entry_to_page(pmd_to_swp_entry(*pmd)); |
| if (!get_page_unless_zero(page)) |
| goto unlock; |
| spin_unlock(ptl); |
| put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE); |
| return; |
| unlock: |
| spin_unlock(ptl); |
| } |
| #endif |
| |
| static int expected_page_refs(struct address_space *mapping, struct page *page) |
| { |
| int expected_count = 1; |
| |
| /* |
| * Device private pages have an extra refcount as they are |
| * ZONE_DEVICE pages. |
| */ |
| expected_count += is_device_private_page(page); |
| if (mapping) |
| expected_count += compound_nr(page) + page_has_private(page); |
| |
| return expected_count; |
| } |
| |
| /* |
| * Replace the page in the mapping. |
| * |
| * The number of remaining references must be: |
| * 1 for anonymous pages without a mapping |
| * 2 for pages with a mapping |
| * 3 for pages with a mapping and PagePrivate/PagePrivate2 set. |
| */ |
| int 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 = expected_page_refs(mapping, &folio->page) + extra_count; |
| long nr = folio_nr_pages(folio); |
| |
| if (!mapping) { |
| /* Anonymous page without mapping */ |
| if (folio_ref_count(folio) != expected_count) |
| return -EAGAIN; |
| |
| /* No turning back from here */ |
| newfolio->index = folio->index; |
| newfolio->mapping = folio->mapping; |
| if (folio_test_swapbacked(folio)) |
| __folio_set_swapbacked(newfolio); |
| |
| return MIGRATEPAGE_SUCCESS; |
| } |
| |
| oldzone = folio_zone(folio); |
| newzone = folio_zone(newfolio); |
| |
| xas_lock_irq(&xas); |
| if (folio_ref_count(folio) != expected_count || |
| xas_load(&xas) != folio) { |
| xas_unlock_irq(&xas); |
| return -EAGAIN; |
| } |
| |
| if (!folio_ref_freeze(folio, expected_count)) { |
| xas_unlock_irq(&xas); |
| return -EAGAIN; |
| } |
| |
| /* |
| * Now we know that no one else is looking at the folio: |
| * no turning back from here. |
| */ |
| newfolio->index = folio->index; |
| newfolio->mapping = folio->mapping; |
| folio_ref_add(newfolio, nr); /* add cache reference */ |
| if (folio_test_swapbacked(folio)) { |
| __folio_set_swapbacked(newfolio); |
| if (folio_test_swapcache(folio)) { |
| folio_set_swapcache(newfolio); |
| newfolio->private = folio_get_private(folio); |
| } |
| } else { |
| VM_BUG_ON_FOLIO(folio_test_swapcache(folio), folio); |
| } |
| |
| /* Move dirty while page refs frozen and newpage not yet exposed */ |
| dirty = folio_test_dirty(folio); |
| if (dirty) { |
| folio_clear_dirty(folio); |
| folio_set_dirty(newfolio); |
| } |
| |
| xas_store(&xas, newfolio); |
| if (nr > 1) { |
| int i; |
| |
| for (i = 1; i < nr; i++) { |
| xas_next(&xas); |
| xas_store(&xas, newfolio); |
| } |
| } |
| |
| /* |
| * Drop cache reference from old page by unfreezing |
| * to one less reference. |
| * We know this isn't the last reference. |
| */ |
| folio_ref_unfreeze(folio, expected_count - nr); |
| |
| xas_unlock(&xas); |
| /* Leave irq disabled to prevent preemption while updating stats */ |
| |
| /* |
| * If moved to a different zone then also account |
| * the page for that zone. Other VM counters will be |
| * taken care of when we establish references to the |
| * new page and drop references to the old page. |
| * |
| * Note that anonymous pages are accounted for |
| * via NR_FILE_PAGES and NR_ANON_MAPPED if they |
| * are mapped to swap space. |
| */ |
| if (newzone != oldzone) { |
| struct lruvec *old_lruvec, *new_lruvec; |
| struct mem_cgroup *memcg; |
| |
| memcg = folio_memcg(folio); |
| old_lruvec = mem_cgroup_lruvec(memcg, oldzone->zone_pgdat); |
| new_lruvec = mem_cgroup_lruvec(memcg, newzone->zone_pgdat); |
| |
| __mod_lruvec_state(old_lruvec, NR_FILE_PAGES, -nr); |
| __mod_lruvec_state(new_lruvec, NR_FILE_PAGES, nr); |
| if (folio_test_swapbacked(folio) && !folio_test_swapcache(folio)) { |
| __mod_lruvec_state(old_lruvec, NR_SHMEM, -nr); |
| __mod_lruvec_state(new_lruvec, NR_SHMEM, nr); |
| } |
| #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 page *newpage, struct page *page) |
| { |
| XA_STATE(xas, &mapping->i_pages, page_index(page)); |
| int expected_count; |
| |
| xas_lock_irq(&xas); |
| expected_count = 2 + page_has_private(page); |
| if (page_count(page) != expected_count || xas_load(&xas) != page) { |
| xas_unlock_irq(&xas); |
| return -EAGAIN; |
| } |
| |
| if (!page_ref_freeze(page, expected_count)) { |
| xas_unlock_irq(&xas); |
| return -EAGAIN; |
| } |
| |
| newpage->index = page->index; |
| newpage->mapping = page->mapping; |
| |
| get_page(newpage); |
| |
| xas_store(&xas, newpage); |
| |
| page_ref_unfreeze(page, expected_count - 1); |
| |
| xas_unlock_irq(&xas); |
| |
| return MIGRATEPAGE_SUCCESS; |
| } |
| |
| /* |
| * Copy the 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); |
| 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); |
| 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 |
| ***********************************************************/ |
| |
| /* |
| * Common logic to directly migrate a single LRU page suitable for |
| * pages that do not use PagePrivate/PagePrivate2. |
| * |
| * Pages are locked upon entry and exit. |
| */ |
| int migrate_page(struct address_space *mapping, |
| struct page *newpage, struct page *page, |
| enum migrate_mode mode) |
| { |
| struct folio *newfolio = page_folio(newpage); |
| struct folio *folio = page_folio(page); |
| int rc; |
| |
| BUG_ON(folio_test_writeback(folio)); /* Writeback must be complete */ |
| |
| rc = folio_migrate_mapping(mapping, newfolio, folio, 0); |
| |
| if (rc != MIGRATEPAGE_SUCCESS) |
| return rc; |
| |
| if (mode != MIGRATE_SYNC_NO_COPY) |
| folio_migrate_copy(newfolio, folio); |
| else |
| folio_migrate_flags(newfolio, folio); |
| return MIGRATEPAGE_SUCCESS; |
| } |
| EXPORT_SYMBOL(migrate_page); |
| |
| #ifdef CONFIG_BLOCK |
| /* Returns true if all buffers are successfully locked */ |
| static bool buffer_migrate_lock_buffers(struct buffer_head *head, |
| enum migrate_mode mode) |
| { |
| struct buffer_head *bh = head; |
| |
| /* Simple case, sync compaction */ |
| if (mode != MIGRATE_ASYNC) { |
| do { |
| lock_buffer(bh); |
| bh = bh->b_this_page; |
| |
| } while (bh != head); |
| |
| return true; |
| } |
| |
| /* async case, we cannot block on lock_buffer so use trylock_buffer */ |
| do { |
| if (!trylock_buffer(bh)) { |
| /* |
| * We failed to lock the buffer and cannot stall in |
| * async migration. Release the taken locks |
| */ |
| struct buffer_head *failed_bh = bh; |
| bh = head; |
| while (bh != failed_bh) { |
| unlock_buffer(bh); |
| bh = bh->b_this_page; |
| } |
| return false; |
| } |
| |
| bh = bh->b_this_page; |
| } while (bh != head); |
| return true; |
| } |
| |
| static int __buffer_migrate_page(struct address_space *mapping, |
| struct page *newpage, struct page *page, enum migrate_mode mode, |
| bool check_refs) |
| { |
| struct buffer_head *bh, *head; |
| int rc; |
| int expected_count; |
| |
| if (!page_has_buffers(page)) |
| return migrate_page(mapping, newpage, page, mode); |
| |
| /* Check whether page does not have extra refs before we do more work */ |
| expected_count = expected_page_refs(mapping, page); |
| if (page_count(page) != expected_count) |
| return -EAGAIN; |
| |
| head = page_buffers(page); |
| if (!buffer_migrate_lock_buffers(head, mode)) |
| return -EAGAIN; |
| |
| if (check_refs) { |
| bool busy; |
| bool invalidated = false; |
| |
| recheck_buffers: |
| busy = false; |
| spin_lock(&mapping->private_lock); |
| bh = head; |
| do { |
| if (atomic_read(&bh->b_count)) { |
| busy = true; |
| break; |
| } |
| bh = bh->b_this_page; |
| } while (bh != head); |
| if (busy) { |
| if (invalidated) { |
| rc = -EAGAIN; |
| goto unlock_buffers; |
| } |
| spin_unlock(&mapping->private_lock); |
| invalidate_bh_lrus(); |
| invalidated = true; |
| goto recheck_buffers; |
| } |
| } |
| |
| rc = migrate_page_move_mapping(mapping, newpage, page, 0); |
| if (rc != MIGRATEPAGE_SUCCESS) |
| goto unlock_buffers; |
| |
| attach_page_private(newpage, detach_page_private(page)); |
| |
| bh = head; |
| do { |
| set_bh_page(bh, newpage, bh_offset(bh)); |
| bh = bh->b_this_page; |
| |
| } while (bh != head); |
| |
| if (mode != MIGRATE_SYNC_NO_COPY) |
| migrate_page_copy(newpage, page); |
| else |
| migrate_page_states(newpage, page); |
| |
| rc = MIGRATEPAGE_SUCCESS; |
| unlock_buffers: |
| if (check_refs) |
| spin_unlock(&mapping->private_lock); |
| bh = head; |
| do { |
| unlock_buffer(bh); |
| bh = bh->b_this_page; |
| |
| } while (bh != head); |
| |
| return rc; |
| } |
| |
| /* |
| * Migration function for pages with buffers. This function can only be used |
| * if the underlying filesystem guarantees that no other references to "page" |
| * exist. For example attached buffer heads are accessed only under page lock. |
| */ |
| int buffer_migrate_page(struct address_space *mapping, |
| struct page *newpage, struct page *page, enum migrate_mode mode) |
| { |
| return __buffer_migrate_page(mapping, newpage, page, mode, false); |
| } |
| EXPORT_SYMBOL(buffer_migrate_page); |
| |
| /* |
| * Same as above except that this variant is more careful and checks that there |
| * are also no buffer head references. This function is the right one for |
| * mappings where buffer heads are directly looked up and referenced (such as |
| * block device mappings). |
| */ |
| int buffer_migrate_page_norefs(struct address_space *mapping, |
| struct page *newpage, struct page *page, enum migrate_mode mode) |
| { |
| return __buffer_migrate_page(mapping, newpage, page, mode, true); |
| } |
| #endif |
| |
| /* |
| * Writeback a page to clean the dirty state |
| */ |
| static int writeout(struct address_space *mapping, struct page *page) |
| { |
| struct writeback_control wbc = { |
| .sync_mode = WB_SYNC_NONE, |
| .nr_to_write = 1, |
| .range_start = 0, |
| .range_end = LLONG_MAX, |
| .for_reclaim = 1 |
| }; |
| int rc; |
| |
| if (!mapping->a_ops->writepage) |
| /* No write method for the address space */ |
| return -EINVAL; |
| |
| if (!clear_page_dirty_for_io(page)) |
| /* Someone else already triggered a write */ |
| return -EAGAIN; |
| |
| /* |
| * A dirty page may imply that the underlying filesystem has |
| * the page on some queue. So the page must be clean for |
| * migration. Writeout may mean we loose the lock and the |
| * page state is no longer what we checked for earlier. |
| * At this point we know that the migration attempt cannot |
| * be successful. |
| */ |
| remove_migration_ptes(page, page, false); |
| |
| rc = mapping->a_ops->writepage(page, &wbc); |
| |
| if (rc != AOP_WRITEPAGE_ACTIVATE) |
| /* unlocked. Relock */ |
| lock_page(page); |
| |
| return (rc < 0) ? -EIO : -EAGAIN; |
| } |
| |
| /* |
| * Default handling if a filesystem does not provide a migration function. |
| */ |
| static int fallback_migrate_page(struct address_space *mapping, |
| struct page *newpage, struct page *page, enum migrate_mode mode) |
| { |
| if (PageDirty(page)) { |
| /* Only writeback pages in full synchronous migration */ |
| switch (mode) { |
| case MIGRATE_SYNC: |
| case MIGRATE_SYNC_NO_COPY: |
| break; |
| default: |
| return -EBUSY; |
| } |
| return writeout(mapping, page); |
| } |
| |
| /* |
| * Buffers may be managed in a filesystem specific way. |
| * We must have no buffers or drop them. |
| */ |
| if (page_has_private(page) && |
| !try_to_release_page(page, GFP_KERNEL)) |
| return mode == MIGRATE_SYNC ? -EAGAIN : -EBUSY; |
| |
| return migrate_page(mapping, newpage, page, mode); |
| } |
| |
| /* |
| * Move a page to a newly allocated page |
| * The page is locked and all ptes have been successfully removed. |
| * |
| * The new page will have replaced the old page if this function |
| * is successful. |
| * |
| * Return value: |
| * < 0 - error code |
| * MIGRATEPAGE_SUCCESS - success |
| */ |
| static int move_to_new_page(struct page *newpage, struct page *page, |
| enum migrate_mode mode) |
| { |
| struct address_space *mapping; |
| int rc = -EAGAIN; |
| bool is_lru = !__PageMovable(page); |
| |
| VM_BUG_ON_PAGE(!PageLocked(page), page); |
| VM_BUG_ON_PAGE(!PageLocked(newpage), newpage); |
| |
| mapping = page_mapping(page); |
| |
| if (likely(is_lru)) { |
| if (!mapping) |
| rc = migrate_page(mapping, newpage, page, mode); |
| else if (mapping->a_ops->migratepage) |
| /* |
| * Most pages have a mapping and most filesystems |
| * provide a migratepage callback. Anonymous pages |
| * are part of swap space which also has its own |
| * migratepage callback. This is the most common path |
| * for page migration. |
| */ |
| rc = mapping->a_ops->migratepage(mapping, newpage, |
| page, mode); |
| else |
| rc = fallback_migrate_page(mapping, newpage, |
| page, mode); |
| } else { |
| /* |
| * In case of non-lru page, it could be released after |
| * isolation step. In that case, we shouldn't try migration. |
| */ |
| VM_BUG_ON_PAGE(!PageIsolated(page), page); |
| if (!PageMovable(page)) { |
| rc = MIGRATEPAGE_SUCCESS; |
| __ClearPageIsolated(page); |
| goto out; |
| } |
| |
| rc = mapping->a_ops->migratepage(mapping, newpage, |
| page, mode); |
| WARN_ON_ONCE(rc == MIGRATEPAGE_SUCCESS && |
| !PageIsolated(page)); |
| } |
| |
| /* |
| * When successful, old pagecache page->mapping must be cleared before |
| * page is freed; but stats require that PageAnon be left as PageAnon. |
| */ |
| if (rc == MIGRATEPAGE_SUCCESS) { |
| if (__PageMovable(page)) { |
| VM_BUG_ON_PAGE(!PageIsolated(page), page); |
| |
| /* |
| * We clear PG_movable under page_lock so any compactor |
| * cannot try to migrate this page. |
| */ |
| __ClearPageIsolated(page); |
| } |
| |
| /* |
| * Anonymous and movable page->mapping will be cleared by |
| * free_pages_prepare so don't reset it here for keeping |
| * the type to work PageAnon, for example. |
| */ |
| if (!PageMappingFlags(page)) |
| page->mapping = NULL; |
| |
| if (likely(!is_zone_device_page(newpage))) |
| flush_dcache_page(newpage); |
| |
| } |
| out: |
| return rc; |
| } |
| |
| static int __unmap_and_move(struct page *page, struct page *newpage, |
| int force, enum migrate_mode mode) |
| { |
| int rc = -EAGAIN; |
| bool page_was_mapped = false; |
| struct anon_vma *anon_vma = NULL; |
| bool is_lru = !__PageMovable(page); |
| |
| if (!trylock_page(page)) { |
| if (!force || mode == MIGRATE_ASYNC) |
| goto out; |
| |
| /* |
| * It's not safe for direct compaction to call lock_page. |
| * For example, during page readahead pages are added locked |
| * to the LRU. Later, when the IO completes the pages are |
| * marked uptodate and unlocked. However, the queueing |
| * could be merging multiple pages for one bio (e.g. |
| * mpage_readahead). If an allocation happens for the |
| * second or third page, the process can end up locking |
| * the same page twice and deadlocking. Rather than |
| * trying to be clever about what pages can be locked, |
| * avoid the use of lock_page for direct compaction |
| * altogether. |
| */ |
| if (current->flags & PF_MEMALLOC) |
| goto out; |
| |
| lock_page(page); |
| } |
| |
| if (PageWriteback(page)) { |
| /* |
| * Only in the case of a full synchronous migration is it |
| * necessary to wait for PageWriteback. In the async case, |
| * the retry loop is too short and in the sync-light case, |
| * the overhead of stalling is too much |
| */ |
| switch (mode) { |
| case MIGRATE_SYNC: |
| case MIGRATE_SYNC_NO_COPY: |
| break; |
| default: |
| rc = -EBUSY; |
| goto out_unlock; |
| } |
| if (!force) |
| goto out_unlock; |
| wait_on_page_writeback(page); |
| } |
| |
| /* |
| * By try_to_migrate(), page->mapcount goes down to 0 here. In this case, |
| * we cannot notice that anon_vma is freed while we migrates a page. |
| * This get_anon_vma() delays freeing anon_vma pointer until the end |
| * of migration. File cache pages are no problem because of page_lock() |
| * File Caches may use write_page() or lock_page() in migration, then, |
| * just care Anon page here. |
| * |
| * Only page_get_anon_vma() understands the subtleties of |
| * getting a hold on an anon_vma from outside one of its mms. |
| * But if we cannot get anon_vma, then we won't need it anyway, |
| * because that implies that the anon page is no longer mapped |
| * (and cannot be remapped so long as we hold the page lock). |
| */ |
| if (PageAnon(page) && !PageKsm(page)) |
| anon_vma = page_get_anon_vma(page); |
| |
| /* |
| * Block others from accessing the new page when we get around to |
| * establishing additional references. We are usually the only one |
| * holding a reference to newpage at this point. We used to have a BUG |
| * here if trylock_page(newpage) fails, but would like to allow for |
| * cases where there might be a race with the previous use of newpage. |
| * This is much like races on refcount of oldpage: just don't BUG(). |
| */ |
| if (unlikely(!trylock_page(newpage))) |
| goto out_unlock; |
| |
| if (unlikely(!is_lru)) { |
| rc = move_to_new_page(newpage, page, mode); |
| goto out_unlock_both; |
| } |
| |
| /* |
| * Corner case handling: |
| * 1. When a new swap-cache page is read into, it is added to the LRU |
| * and treated as swapcache but it has no rmap yet. |
| * Calling try_to_unmap() against a page->mapping==NULL page will |
| * trigger a BUG. So handle it here. |
| * 2. An orphaned page (see truncate_cleanup_page) might have |
| * fs-private metadata. The page can be picked up due to memory |
| * offlining. Everywhere else except page reclaim, the page is |
| * invisible to the vm, so the page can not be migrated. So try to |
| * free the metadata, so the page can be freed. |
| */ |
| if (!page->mapping) { |
| VM_BUG_ON_PAGE(PageAnon(page), page); |
| if (page_has_private(page)) { |
| try_to_free_buffers(page); |
| goto out_unlock_both; |
| } |
| } else if (page_mapped(page)) { |
| /* Establish migration ptes */ |
| VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma, |
| page); |
| try_to_migrate(page, 0); |
| page_was_mapped = true; |
| } |
| |
| if (!page_mapped(page)) |
| rc = move_to_new_page(newpage, page, mode); |
| |
| if (page_was_mapped) |
| remove_migration_ptes(page, |
| rc == MIGRATEPAGE_SUCCESS ? newpage : page, false); |
| |
| out_unlock_both: |
| unlock_page(newpage); |
| out_unlock: |
| /* Drop an anon_vma reference if we took one */ |
| if (anon_vma) |
| put_anon_vma(anon_vma); |
| unlock_page(page); |
| out: |
| /* |
| * If migration is successful, decrease refcount of the newpage |
| * which will not free the page because new page owner increased |
| * refcounter. As well, if it is LRU page, add the page to LRU |
| * list in here. Use the old state of the isolated source page to |
| * determine if we migrated a LRU page. newpage was already unlocked |
| * and possibly modified by its owner - don't rely on the page |
| * state. |
| */ |
| if (rc == MIGRATEPAGE_SUCCESS) { |
| if (unlikely(!is_lru)) |
| put_page(newpage); |
| else |
| putback_lru_page(newpage); |
| } |
| |
| return rc; |
| } |
| |
| |
| /* |
| * node_demotion[] example: |
| * |
| * Consider a system with two sockets. Each socket has |
| * three classes of memory attached: fast, medium and slow. |
| * Each memory class is placed in its own NUMA node. The |
| * CPUs are placed in the node with the "fast" memory. The |
| * 6 NUMA nodes (0-5) might be split among the sockets like |
| * this: |
| * |
| * Socket A: 0, 1, 2 |
| * Socket B: 3, 4, 5 |
| * |
| * When Node 0 fills up, its memory should be migrated to |
| * Node 1. When Node 1 fills up, it should be migrated to |
| * Node 2. The migration path start on the nodes with the |
| * processors (since allocations default to this node) and |
| * fast memory, progress through medium and end with the |
| * slow memory: |
| * |
| * 0 -> 1 -> 2 -> stop |
| * 3 -> 4 -> 5 -> stop |
| * |
| * This is represented in the node_demotion[] like this: |
| * |
| * { 1, // Node 0 migrates to 1 |
| * 2, // Node 1 migrates to 2 |
| * -1, // Node 2 does not migrate |
| * 4, // Node 3 migrates to 4 |
| * 5, // Node 4 migrates to 5 |
| * -1} // Node 5 does not migrate |
| */ |
| |
| /* |
| * Writes to this array occur without locking. Cycles are |
| * not allowed: Node X demotes to Y which demotes to X... |
| * |
| * If multiple reads are performed, a single rcu_read_lock() |
| * must be held over all reads to ensure that no cycles are |
| * observed. |
| */ |
| static int node_demotion[MAX_NUMNODES] __read_mostly = |
| {[0 ... MAX_NUMNODES - 1] = NUMA_NO_NODE}; |
| |
| /** |
| * next_demotion_node() - Get the next node in the demotion path |
| * @node: The starting node to lookup the next node |
| * |
| * Return: node id for next memory node in the demotion path hierarchy |
| * from @node; NUMA_NO_NODE if @node is terminal. This does not keep |
| * @node online or guarantee that it *continues* to be the next demotion |
| * target. |
| */ |
| int next_demotion_node(int node) |
| { |
| int target; |
| |
| /* |
| * node_demotion[] is updated without excluding this |
| * function from running. RCU doesn't provide any |
| * compiler barriers, so the READ_ONCE() is required |
| * to avoid compiler reordering or read merging. |
| * |
| * Make sure to use RCU over entire code blocks if |
| * node_demotion[] reads need to be consistent. |
| */ |
| rcu_read_lock(); |
| target = READ_ONCE(node_demotion[node]); |
| rcu_read_unlock(); |
| |
| return target; |
| } |
| |
| /* |
| * Obtain the lock on page, remove all ptes and migrate the page |
| * to the newly allocated page in newpage. |
| */ |
| static int unmap_and_move(new_page_t get_new_page, |
| free_page_t put_new_page, |
| unsigned long private, struct page *page, |
| int force, enum migrate_mode mode, |
| enum migrate_reason reason, |
| struct list_head *ret) |
| { |
| int rc = MIGRATEPAGE_SUCCESS; |
| struct page *newpage = NULL; |
| |
| if (!thp_migration_supported() && PageTransHuge(page)) |
| return -ENOSYS; |
| |
| if (page_count(page) == 1) { |
| /* page was freed from under us. So we are done. */ |
| ClearPageActive(page); |
| ClearPageUnevictable(page); |
| if (unlikely(__PageMovable(page))) { |
| lock_page(page); |
| if (!PageMovable(page)) |
| __ClearPageIsolated(page); |
| unlock_page(page); |
| } |
| goto out; |
| } |
| |
| newpage = get_new_page(page, private); |
| if (!newpage) |
| return -ENOMEM; |
| |
| rc = __unmap_and_move(page, newpage, force, mode); |
| if (rc == MIGRATEPAGE_SUCCESS) |
| set_page_owner_migrate_reason(newpage, reason); |
| |
| out: |
| if (rc != -EAGAIN) { |
| /* |
| * A page that has been migrated has all references |
| * removed and will be freed. A page that has not been |
| * migrated will have kept its references and be restored. |
| */ |
| list_del(&page->lru); |
| } |
| |
| /* |
| * If migration is successful, releases reference grabbed during |
| * isolation. Otherwise, restore the page to right list unless |
| * we want to retry. |
| */ |
| if (rc == MIGRATEPAGE_SUCCESS) { |
| /* |
| * Compaction can migrate also non-LRU pages which are |
| * not accounted to NR_ISOLATED_*. They can be recognized |
| * as __PageMovable |
| */ |
| if (likely(!__PageMovable(page))) |
| mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + |
| page_is_file_lru(page), -thp_nr_pages(page)); |
| |
| if (reason != MR_MEMORY_FAILURE) |
| /* |
| * We release the page in page_handle_poison. |
| */ |
| put_page(page); |
| } else { |
| if (rc != -EAGAIN) |
| list_add_tail(&page->lru, ret); |
| |
| if (put_new_page) |
| put_new_page(newpage, private); |
| else |
| put_page(newpage); |
| } |
| |
| return rc; |
| } |
| |
| /* |
| * Counterpart of unmap_and_move_page() for hugepage migration. |
| * |
| * This function doesn't wait the completion of hugepage I/O |
| * because there is no race between I/O and migration for hugepage. |
| * Note that currently hugepage I/O occurs only in direct I/O |
| * where no lock is held and PG_writeback is irrelevant, |
| * and writeback status of all subpages are counted in the reference |
| * count of the head page (i.e. if all subpages of a 2MB hugepage are |
| * under direct I/O, the reference of the head page is 512 and a bit more.) |
| * This means that when we try to migrate hugepage whose subpages are |
| * doing direct I/O, some references remain after try_to_unmap() and |
| * hugepage migration fails without data corruption. |
| * |
| * There is also no race when direct I/O is issued on the page under migration, |
| * because then pte is replaced with migration swap entry and direct I/O code |
| * will wait in the page fault for migration to complete. |
| */ |
| static int unmap_and_move_huge_page(new_page_t get_new_page, |
| free_page_t put_new_page, unsigned long private, |
| struct page *hpage, int force, |
| enum migrate_mode mode, int reason, |
| struct list_head *ret) |
| { |
| int rc = -EAGAIN; |
| int page_was_mapped = 0; |
| struct page *new_hpage; |
| struct anon_vma *anon_vma = NULL; |
| struct address_space *mapping = NULL; |
| |
| /* |
| * Migratability of hugepages depends on architectures and their size. |
| * This check is necessary because some callers of hugepage migration |
| * like soft offline and memory hotremove don't walk through page |
| * tables or check whether the hugepage is pmd-based or not before |
| * kicking migration. |
| */ |
| if (!hugepage_migration_supported(page_hstate(hpage))) { |
| list_move_tail(&hpage->lru, ret); |
| return -ENOSYS; |
| } |
| |
| if (page_count(hpage) == 1) { |
| /* page was freed from under us. So we are done. */ |
| putback_active_hugepage(hpage); |
| return MIGRATEPAGE_SUCCESS; |
| } |
| |
| new_hpage = get_new_page(hpage, private); |
| if (!new_hpage) |
| return -ENOMEM; |
| |
| if (!trylock_page(hpage)) { |
| if (!force) |
| goto out; |
| switch (mode) { |
| case MIGRATE_SYNC: |
| case MIGRATE_SYNC_NO_COPY: |
| break; |
| default: |
| goto out; |
| } |
| lock_page(hpage); |
| } |
| |
| /* |
| * Check for pages which are in the process of being freed. Without |
| * page_mapping() set, hugetlbfs specific move page routine will not |
| * be called and we could leak usage counts for subpools. |
| */ |
| if (hugetlb_page_subpool(hpage) && !page_mapping(hpage)) { |
| rc = -EBUSY; |
| goto out_unlock; |
| } |
| |
| if (PageAnon(hpage)) |
| anon_vma = page_get_anon_vma(hpage); |
| |
| if (unlikely(!trylock_page(new_hpage))) |
| goto put_anon; |
| |
| if (page_mapped(hpage)) { |
| bool mapping_locked = false; |
| enum ttu_flags ttu = 0; |
| |
| if (!PageAnon(hpage)) { |
| /* |
| * In shared mappings, try_to_unmap could potentially |
| * call huge_pmd_unshare. Because of this, take |
| * semaphore in write mode here and set TTU_RMAP_LOCKED |
| * to let lower levels know we have taken the lock. |
| */ |
| mapping = hugetlb_page_mapping_lock_write(hpage); |
| if (unlikely(!mapping)) |
| goto unlock_put_anon; |
| |
| mapping_locked = true; |
| ttu |= TTU_RMAP_LOCKED; |
| } |
| |
| try_to_migrate(hpage, ttu); |
| page_was_mapped = 1; |
| |
| if (mapping_locked) |
| i_mmap_unlock_write(mapping); |
| } |
| |
| if (!page_mapped(hpage)) |
| rc = move_to_new_page(new_hpage, hpage, mode); |
| |
| if (page_was_mapped) |
| remove_migration_ptes(hpage, |
| rc == MIGRATEPAGE_SUCCESS ? new_hpage : hpage, false); |
| |
| unlock_put_anon: |
| unlock_page(new_hpage); |
| |
| put_anon: |
| if (anon_vma) |
| put_anon_vma(anon_vma); |
| |
| if (rc == MIGRATEPAGE_SUCCESS) { |
| move_hugetlb_state(hpage, new_hpage, reason); |
| put_new_page = NULL; |
| } |
| |
| out_unlock: |
| unlock_page(hpage); |
| out: |
| if (rc == MIGRATEPAGE_SUCCESS) |
| putback_active_hugepage(hpage); |
| else if (rc != -EAGAIN) |
| list_move_tail(&hpage->lru, ret); |
| |
| /* |
| * If migration was not successful and there's a freeing callback, use |
| * it. Otherwise, put_page() will drop the reference grabbed during |
| * isolation. |
| */ |
| if (put_new_page) |
| put_new_page(new_hpage, private); |
| else |
| putback_active_hugepage(new_hpage); |
| |
| return rc; |
| } |
| |
| static inline int try_split_thp(struct page *page, struct page **page2, |
| struct list_head *from) |
| { |
| int rc = 0; |
| |
| lock_page(page); |
| rc = split_huge_page_to_list(page, from); |
| unlock_page(page); |
| if (!rc) |
| list_safe_reset_next(page, *page2, lru); |
| |
| return rc; |
| } |
| |
| /* |
| * migrate_pages - migrate the pages specified in a list, to the free pages |
| * supplied as the target for the page migration |
| * |
| * @from: The list of pages to be migrated. |
| * @get_new_page: The function used to allocate free pages to be used |
| * as the target of the page migration. |
| * @put_new_page: The function used to free target pages if migration |
| * fails, or NULL if no special handling is necessary. |
| * @private: Private data to be passed on to get_new_page() |
| * @mode: The migration mode that specifies the constraints for |
| * page migration, if any. |
| * @reason: The reason for page migration. |
| * @ret_succeeded: Set to the number of pages migrated successfully if |
| * the caller passes a non-NULL pointer. |
| * |
| * The function returns after 10 attempts or if no pages are movable any more |
| * because the list has become empty or no retryable pages exist any more. |
| * It is caller's responsibility to call putback_movable_pages() to return pages |
| * to the LRU or free list only if ret != 0. |
| * |
| * Returns the number of pages that were not migrated, or an error code. |
| */ |
| int migrate_pages(struct list_head *from, new_page_t get_new_page, |
| free_page_t put_new_page, unsigned long private, |
| enum migrate_mode mode, int reason, unsigned int *ret_succeeded) |
| { |
| int retry = 1; |
| int thp_retry = 1; |
| int nr_failed = 0; |
| int nr_succeeded = 0; |
| int nr_thp_succeeded = 0; |
| int nr_thp_failed = 0; |
| int nr_thp_split = 0; |
| int pass = 0; |
| bool is_thp = false; |
| struct page *page; |
| struct page *page2; |
| int swapwrite = current->flags & PF_SWAPWRITE; |
| int rc, nr_subpages; |
| LIST_HEAD(ret_pages); |
| bool nosplit = (reason == MR_NUMA_MISPLACED); |
| |
| trace_mm_migrate_pages_start(mode, reason); |
| |
| if (!swapwrite) |
| current->flags |= PF_SWAPWRITE; |
| |
| for (pass = 0; pass < 10 && (retry || thp_retry); pass++) { |
| retry = 0; |
| thp_retry = 0; |
| |
| list_for_each_entry_safe(page, page2, from, lru) { |
| retry: |
| /* |
| * THP statistics is based on the source huge page. |
| * Capture required information that might get lost |
| * during migration. |
| */ |
| is_thp = PageTransHuge(page) && !PageHuge(page); |
| nr_subpages = thp_nr_pages(page); |
| cond_resched(); |
| |
| if (PageHuge(page)) |
| rc = unmap_and_move_huge_page(get_new_page, |
| put_new_page, private, page, |
| pass > 2, mode, reason, |
| &ret_pages); |
| else |
| rc = unmap_and_move(get_new_page, put_new_page, |
| private, page, pass > 2, mode, |
| reason, &ret_pages); |
| /* |
| * The rules are: |
| * Success: non hugetlb page will be freed, hugetlb |
| * page will be put back |
| * -EAGAIN: stay on the from list |
| * -ENOMEM: stay on the from list |
| * Other errno: put on ret_pages list then splice to |
| * from list |
| */ |
| switch(rc) { |
| /* |
| * THP migration might be unsupported or the |
| * allocation could've failed so we should |
| * retry on the same page with the THP split |
| * to base pages. |
| * |
| * Head page is retried immediately and tail |
| * pages are added to the tail of the list so |
| * we encounter them after the rest of the list |
| * is processed. |
| */ |
| case -ENOSYS: |
| /* THP migration is unsupported */ |
| if (is_thp) { |
| if (!try_split_thp(page, &page2, from)) { |
| nr_thp_split++; |
| goto retry; |
| } |
| |
| nr_thp_failed++; |
| nr_failed += nr_subpages; |
| break; |
| } |
| |
| /* Hugetlb migration is unsupported */ |
| nr_failed++; |
| break; |
| case -ENOMEM: |
| /* |
| * When memory is low, don't bother to try to migrate |
| * other pages, just exit. |
| * THP NUMA faulting doesn't split THP to retry. |
| */ |
| if (is_thp && !nosplit) { |
| if (!try_split_thp(page, &page2, from)) { |
| nr_thp_split++; |
| goto retry; |
| } |
| |
| nr_thp_failed++; |
| nr_failed += nr_subpages; |
| goto out; |
| } |
| nr_failed++; |
| goto out; |
| case -EAGAIN: |
| if (is_thp) { |
| thp_retry++; |
| break; |
| } |
| retry++; |
| break; |
| case MIGRATEPAGE_SUCCESS: |
| if (is_thp) { |
| nr_thp_succeeded++; |
| nr_succeeded += nr_subpages; |
| break; |
| } |
| nr_succeeded++; |
| break; |
| default: |
| /* |
| * Permanent failure (-EBUSY, etc.): |
| * unlike -EAGAIN case, the failed page is |
| * removed from migration page list and not |
| * retried in the next outer loop. |
| */ |
| if (is_thp) { |
| nr_thp_failed++; |
| nr_failed += nr_subpages; |
| break; |
| } |
| nr_failed++; |
| break; |
| } |
| } |
| } |
| nr_failed += retry + thp_retry; |
| nr_thp_failed += thp_retry; |
| rc = nr_failed; |
| out: |
| /* |
| * Put the permanent failure page back to migration list, they |
| * will be put back to the right list by the caller. |
| */ |
| list_splice(&ret_pages, from); |
| |
| count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded); |
| count_vm_events(PGMIGRATE_FAIL, nr_failed); |
| count_vm_events(THP_MIGRATION_SUCCESS, nr_thp_succeeded); |
| count_vm_events(THP_MIGRATION_FAIL, nr_thp_failed); |
| count_vm_events(THP_MIGRATION_SPLIT, nr_thp_split); |
| trace_mm_migrate_pages(nr_succeeded, nr_failed, nr_thp_succeeded, |
| nr_thp_failed, nr_thp_split, mode, reason); |
| |
| if (!swapwrite) |
| current->flags &= ~PF_SWAPWRITE; |
| |
| if (ret_succeeded) |
| *ret_succeeded = nr_succeeded; |
| |
| return rc; |
| } |
| |
| struct page *alloc_migration_target(struct page *page, unsigned long private) |
| { |
| struct migration_target_control *mtc; |
| gfp_t gfp_mask; |
| unsigned int order = 0; |
| struct page *new_page = NULL; |
| int nid; |
| int zidx; |
| |
| mtc = (struct migration_target_control *)private; |
| gfp_mask = mtc->gfp_mask; |
| nid = mtc->nid; |
| if (nid == NUMA_NO_NODE) |
| nid = page_to_nid(page); |
| |
| if (PageHuge(page)) { |
| struct hstate *h = page_hstate(compound_head(page)); |
| |
| gfp_mask = htlb_modify_alloc_mask(h, gfp_mask); |
| return alloc_huge_page_nodemask(h, nid, mtc->nmask, gfp_mask); |
| } |
| |
| if (PageTransHuge(page)) { |
| /* |
| * clear __GFP_RECLAIM to make the migration callback |
| * consistent with regular THP allocations. |
| */ |
| gfp_mask &= ~__GFP_RECLAIM; |
| gfp_mask |= GFP_TRANSHUGE; |
| order = HPAGE_PMD_ORDER; |
| } |
| zidx = zone_idx(page_zone(page)); |
| if (is_highmem_idx(zidx) || zidx == ZONE_MOVABLE) |
| gfp_mask |= __GFP_HIGHMEM; |
| |
| new_page = __alloc_pages(gfp_mask, order, nid, mtc->nmask); |
| |
| if (new_page && PageTransHuge(new_page)) |
| prep_transhuge_page(new_page); |
| |
| return new_page; |
| } |
| |
| #ifdef CONFIG_NUMA |
| |
| static int store_status(int __user *status, int start, int value, int nr) |
| { |
| while (nr-- > 0) { |
| if (put_user(value, status + start)) |
| return -EFAULT; |
| start++; |
| } |
| |
| return 0; |
| } |
| |
| static int do_move_pages_to_node(struct mm_struct *mm, |
| struct list_head *pagelist, int node) |
| { |
| int err; |
| struct migration_target_control mtc = { |
| .nid = node, |
| .gfp_mask = GFP_HIGHUSER_MOVABLE | __GFP_THISNODE, |
| }; |
| |
| err = migrate_pages(pagelist, alloc_migration_target, NULL, |
| (unsigned long)&mtc, MIGRATE_SYNC, MR_SYSCALL, NULL); |
| if (err) |
| putback_movable_pages(pagelist); |
| return err; |
| } |
| |
| /* |
| * Resolves the given address to a struct page, isolates it from the LRU and |
| * puts it to the given pagelist. |
| * Returns: |
| * errno - if the page cannot be found/isolated |
| * 0 - when it doesn't have to be migrated because it is already on the |
| * target node |
| * 1 - when it has been queued |
| */ |
| static int add_page_for_migration(struct mm_struct *mm, unsigned long addr, |
| int node, struct list_head *pagelist, bool migrate_all) |
| { |
| struct vm_area_struct *vma; |
| struct page *page; |
| unsigned int follflags; |
| int err; |
| |
| mmap_read_lock(mm); |
| err = -EFAULT; |
| vma = find_vma(mm, addr); |
| if (!vma || addr < vma->vm_start || !vma_migratable(vma)) |
| goto out; |
| |
| /* FOLL_DUMP to ignore special (like zero) pages */ |
| follflags = FOLL_GET | FOLL_DUMP; |
| page = follow_page(vma, addr, follflags); |
| |
| err = PTR_ERR(page); |
| if (IS_ERR(page)) |
| goto out; |
| |
| err = -ENOENT; |
| if (!page) |
| goto out; |
| |
| err = 0; |
| if (page_to_nid(page) == node) |
| goto out_putpage; |
| |
| err = -EACCES; |
| if (page_mapcount(page) > 1 && !migrate_all) |
| goto out_putpage; |
| |
| if (PageHuge(page)) { |
| if (PageHead(page)) { |
| isolate_huge_page(page, pagelist); |
| err = 1; |
| } |
| } else { |
| struct page *head; |
| |
| head = compound_head(page); |
| err = isolate_lru_page(head); |
| if (err) |
| goto out_putpage; |
| |
| err = 1; |
| list_add_tail(&head->lru, pagelist); |
| mod_node_page_state(page_pgdat(head), |
| NR_ISOLATED_ANON + page_is_file_lru(head), |
| thp_nr_pages(head)); |
| } |
| out_putpage: |
| /* |
| * Either remove the duplicate refcount from |
| * isolate_lru_page() or drop the page ref if it was |
| * not isolated. |
| */ |
| put_page(page); |
| out: |
| mmap_read_unlock(mm); |
| return err; |
| } |
| |
| static int move_pages_and_store_status(struct mm_struct *mm, int node, |
| struct list_head *pagelist, int __user *status, |
| int start, int i, unsigned long nr_pages) |
| { |
| int err; |
| |
| if (list_empty(pagelist)) |
| return 0; |
| |
| err = do_move_pages_to_node(mm, pagelist, node); |
| if (err) { |
| /* |
| * Positive err means the number of failed |
| * pages to migrate. Since we are going to |
| * abort and return the number of non-migrated |
| * pages, so need to include the rest of the |
| * nr_pages that have not been attempted as |
| * well. |
| */ |
| if (err > 0) |
| err += nr_pages - i - 1; |
| return err; |
| } |
| return store_status(status, start, node, i - start); |
| } |
| |
| /* |
| * Migrate an array of page address onto an array of nodes and fill |
| * the corresponding array of status. |
| */ |
| static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes, |
| unsigned long nr_pages, |
| const void __user * __user *pages, |
| const int __user *nodes, |
| int __user *status, int flags) |
| { |
| int current_node = NUMA_NO_NODE; |
| LIST_HEAD(pagelist); |
| int start, i; |
| int err = 0, err1; |
| |
| lru_cache_disable(); |
| |
| for (i = start = 0; i < nr_pages; i++) { |
| const void __user *p; |
| unsigned long addr; |
| int node; |
| |
| err = -EFAULT; |
| if (get_user(p, pages + i)) |
| goto out_flush; |
| if (get_user(node, nodes + i)) |
| goto out_flush; |
| addr = (unsigned long)untagged_addr(p); |
| |
| err = -ENODEV; |
| if (node < 0 || node >= MAX_NUMNODES) |
| goto out_flush; |
| if (!node_state(node, N_MEMORY)) |
| goto out_flush; |
| |
| err = -EACCES; |
| if (!node_isset(node, task_nodes)) |
| goto out_flush; |
| |
| if (current_node == NUMA_NO_NODE) { |
| current_node = node; |
| start = i; |
| } else if (node != current_node) { |
| err = move_pages_and_store_status(mm, current_node, |
| &pagelist, status, start, i, nr_pages); |
| if (err) |
| goto out; |
| start = i; |
| current_node = node; |
| } |
| |
| /* |
| * Errors in the page lookup or isolation are not fatal and we simply |
| * report them via status |
| */ |
| err = add_page_for_migration(mm, addr, current_node, |
| &pagelist, flags & MPOL_MF_MOVE_ALL); |
| |
| if (err > 0) { |
| /* The page is successfully queued for migration */ |
| continue; |
| } |
| |
| /* |
| * If the page is already on the target node (!err), store the |
| * node, otherwise, store the err. |
| */ |
| err = store_status(status, i, err ? : current_node, 1); |
| if (err) |
| goto out_flush; |
| |
| err = move_pages_and_store_status(mm, current_node, &pagelist, |
| status, start, i, nr_pages); |
| if (err) |
| goto out; |
| current_node = NUMA_NO_NODE; |
| } |
| out_flush: |
| /* Make sure we do not overwrite the existing error */ |
| err1 = move_pages_and_store_status(mm, current_node, &pagelist, |
| status, start, i, nr_pages); |
| if (err >= 0) |
| err = err1; |
| out: |
| lru_cache_enable(); |
| return err; |
| } |
| |
| /* |
| * Determine the nodes of an array of pages and store it in an array of status. |
| */ |
| static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, |
| const void __user **pages, int *status) |
| { |
| unsigned long i; |
| |
| mmap_read_lock(mm); |
| |
| for (i = 0; i < nr_pages; i++) { |
| unsigned long addr = (unsigned long)(*pages); |
| struct vm_area_struct *vma; |
| struct page *page; |
| int err = -EFAULT; |
| |
| vma = vma_lookup(mm, addr); |
| if (!vma) |
| goto set_status; |
| |
| /* FOLL_DUMP to ignore special (like zero) pages */ |
| page = follow_page(vma, addr, FOLL_DUMP); |
| |
| err = PTR_ERR(page); |
| if (IS_ERR(page)) |
| goto set_status; |
| |
| err = page ? page_to_nid(page) : -ENOENT; |
| set_status: |
| *status = err; |
| |
| pages++; |
| status++; |
| } |
| |
| mmap_read_unlock(mm); |
| } |
| |
| static int get_compat_pages_array(const void __user *chunk_pages[], |
| const void __user * __user *pages, |
| unsigned long chunk_nr) |
| { |
| compat_uptr_t __user *pages32 = (compat_uptr_t __user *)pages; |
| compat_uptr_t p; |
| int i; |
| |
| for (i = 0; i < chunk_nr; i++) { |
| if (get_user(p, pages32 + i)) |
| return -EFAULT; |
| chunk_pages[i] = compat_ptr(p); |
| } |
| |
| return 0; |
| } |
| |
| /* |
| * Determine the nodes of a user array of pages and store it in |
| * a user array of status. |
| */ |
| static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages, |
| const void __user * __user *pages, |
| int __user *status) |
| { |
| #define DO_PAGES_STAT_CHUNK_NR 16 |
| const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR]; |
| int chunk_status[DO_PAGES_STAT_CHUNK_NR]; |
| |
| while (nr_pages) { |
| unsigned long chunk_nr; |
| |
| chunk_nr = nr_pages; |
| if (chunk_nr > DO_PAGES_STAT_CHUNK_NR) |
| chunk_nr = DO_PAGES_STAT_CHUNK_NR; |
| |
| if (in_compat_syscall()) { |
| if (get_compat_pages_array(chunk_pages, pages, |
| chunk_nr)) |
| break; |
| } else { |
| if (copy_from_user(chunk_pages, pages, |
| chunk_nr * sizeof(*chunk_pages))) |
| break; |
| } |
| |
| do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status); |
| |
| if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status))) |
| break; |
| |
| pages += chunk_nr; |
| status += chunk_nr; |
| nr_pages -= chunk_nr; |
| } |
| return nr_pages ? -EFAULT : 0; |
| } |
| |
| static struct mm_struct *find_mm_struct(pid_t pid, nodemask_t *mem_nodes) |
| { |
| struct task_struct *task; |
| struct mm_struct *mm; |
| |
| /* |
| * There is no need to check if current process has the right to modify |
| * the specified process when they are same. |
| */ |
| if (!pid) { |
| mmget(current->mm); |
| *mem_nodes = cpuset_mems_allowed(current); |
| return current->mm; |
| } |
| |
| /* Find the mm_struct */ |
| rcu_read_lock(); |
| task = find_task_by_vpid(pid); |
| if (!task) { |
| rcu_read_unlock(); |
| return ERR_PTR(-ESRCH); |
| } |
| get_task_struct(task); |
| |
| /* |
| * Check if this process has the right to modify the specified |
| * process. Use the regular "ptrace_may_access()" checks. |
| */ |
| if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) { |
| rcu_read_unlock(); |
| mm = ERR_PTR(-EPERM); |
| goto out; |
| } |
| rcu_read_unlock(); |
| |
| mm = ERR_PTR(security_task_movememory(task)); |
| if (IS_ERR(mm)) |
| goto out; |
| *mem_nodes = cpuset_mems_allowed(task); |
| mm = get_task_mm(task); |
| out: |
| put_task_struct(task); |
| if (!mm) |
| mm = ERR_PTR(-EINVAL); |
| return mm; |
| } |
| |
| /* |
| * Move a list of pages in the address space of the currently executing |
| * process. |
| */ |
| static int kernel_move_pages(pid_t pid, unsigned long nr_pages, |
| const void __user * __user *pages, |
| const int __user *nodes, |
| int __user *status, int flags) |
| { |
| struct mm_struct *mm; |
| int err; |
| nodemask_t task_nodes; |
| |
| /* Check flags */ |
| if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL)) |
| return -EINVAL; |
| |
| if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE)) |
| return -EPERM; |
| |
| mm = find_mm_struct(pid, &task_nodes); |
| if (IS_ERR(mm)) |
| return PTR_ERR(mm); |
| |
| if (nodes) |
| err = do_pages_move(mm, task_nodes, nr_pages, pages, |
| nodes, status, flags); |
| else |
| err = do_pages_stat(mm, nr_pages, pages, status); |
| |
| mmput(mm); |
| return err; |
| } |
| |
| SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages, |
| const void __user * __user *, pages, |
| const int __user *, nodes, |
| int __user *, status, int, flags) |
| { |
| return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags); |
| } |
| |
| #ifdef CONFIG_NUMA_BALANCING |
| /* |
| * Returns true if this is a safe migration target node for misplaced NUMA |
| * pages. Currently it only checks the watermarks which crude |
| */ |
| static bool migrate_balanced_pgdat(struct pglist_data *pgdat, |
| unsigned long nr_migrate_pages) |
| { |
| int z; |
| |
| for (z = pgdat->nr_zones - 1; z >= 0; z--) { |
| struct zone *zone = pgdat->node_zones + z; |
| |
| if (!populated_zone(zone)) |
| continue; |
| |
| /* Avoid waking kswapd by allocating pages_to_migrate pages. */ |
| if (!zone_watermark_ok(zone, 0, |
| high_wmark_pages(zone) + |
| nr_migrate_pages, |
| ZONE_MOVABLE, 0)) |
| continue; |
| return true; |
| } |
| return false; |
| } |
| |
| static struct page *alloc_misplaced_dst_page(struct page *page, |
| unsigned long data) |
| { |
| int nid = (int) data; |
| struct page *newpage; |
| |
| newpage = __alloc_pages_node(nid, |
| (GFP_HIGHUSER_MOVABLE | |
| __GFP_THISNODE | __GFP_NOMEMALLOC | |
| __GFP_NORETRY | __GFP_NOWARN) & |
| ~__GFP_RECLAIM, 0); |
| |
| return newpage; |
| } |
| |
| static struct page *alloc_misplaced_dst_page_thp(struct page *page, |
| unsigned long data) |
| { |
| int nid = (int) data; |
| struct page *newpage; |
| |
| newpage = alloc_pages_node(nid, (GFP_TRANSHUGE_LIGHT | __GFP_THISNODE), |
| HPAGE_PMD_ORDER); |
| if (!newpage) |
| goto out; |
| |
| prep_transhuge_page(newpage); |
| |
| out: |
| return newpage; |
| } |
| |
| static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page) |
| { |
| int page_lru; |
| int nr_pages = thp_nr_pages(page); |
| |
| VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page); |
| |
| /* Do not migrate THP mapped by multiple processes */ |
| if (PageTransHuge(page) && total_mapcount(page) > 1) |
| return 0; |
| |
| /* Avoid migrating to a node that is nearly full */ |
| if (!migrate_balanced_pgdat(pgdat, nr_pages)) |
| return 0; |
| |
| if (isolate_lru_page(page)) |
| return 0; |
| |
| page_lru = page_is_file_lru(page); |
| mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_lru, |
| nr_pages); |
| |
| /* |
| * Isolating the page has taken another reference, so the |
| * caller's reference can be safely dropped without the page |
| * disappearing underneath us during migration. |
| */ |
| put_page(page); |
| return 1; |
| } |
| |
| /* |
| * Attempt to migrate a misplaced page to the specified destination |
| * node. Caller is expected to have an elevated reference count on |
| * the page that will be dropped by this function before returning. |
| */ |
| int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma, |
| int node) |
| { |
| pg_data_t *pgdat = NODE_DATA(node); |
| int isolated; |
| int nr_remaining; |
| LIST_HEAD(migratepages); |
| new_page_t *new; |
| bool compound; |
| int nr_pages = thp_nr_pages(page); |
| |
| /* |
| * PTE mapped THP or HugeTLB page can't reach here so the page could |
| * be either base page or THP. And it must be head page if it is |
| * THP. |
| */ |
| compound = PageTransHuge(page); |
| |
| if (compound) |
| new = alloc_misplaced_dst_page_thp; |
| else |
| new = alloc_misplaced_dst_page; |
| |
| /* |
| * Don't migrate file pages that are mapped in multiple processes |
| * with execute permissions as they are probably shared libraries. |
| */ |
| if (page_mapcount(page) != 1 && page_is_file_lru(page) && |
| (vma->vm_flags & VM_EXEC)) |
| goto out; |
| |
| /* |
| * Also do not migrate dirty pages as not all filesystems can move |
| * dirty pages in MIGRATE_ASYNC mode which is a waste of cycles. |
| */ |
| if (page_is_file_lru(page) && PageDirty(page)) |
| goto out; |
| |
| isolated = numamigrate_isolate_page(pgdat, page); |
| if (!isolated) |
| goto out; |
| |
| list_add(&page->lru, &migratepages); |
| nr_remaining = migrate_pages(&migratepages, *new, NULL, node, |
| MIGRATE_ASYNC, MR_NUMA_MISPLACED, NULL); |
| if (nr_remaining) { |
| if (!list_empty(&migratepages)) { |
| list_del(&page->lru); |
| mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + |
| page_is_file_lru(page), -nr_pages); |
| putback_lru_page(page); |
| } |
| isolated = 0; |
| } else |
| count_vm_numa_events(NUMA_PAGE_MIGRATE, nr_pages); |
| BUG_ON(!list_empty(&migratepages)); |
| return isolated; |
| |
| out: |
| put_page(page); |
| return 0; |
| } |
| #endif /* CONFIG_NUMA_BALANCING */ |
| #endif /* CONFIG_NUMA */ |
| |
| #ifdef CONFIG_DEVICE_PRIVATE |
| static int migrate_vma_collect_skip(unsigned long start, |
| unsigned long end, |
| struct mm_walk *walk) |
| { |
| struct migrate_vma *migrate = walk->private; |
| unsigned long addr; |
| |
| for (addr = start; addr < end; addr += PAGE_SIZE) { |
| migrate->dst[migrate->npages] = 0; |
| migrate->src[migrate->npages++] = 0; |
| } |
| |
| return 0; |
| } |
| |
| static int migrate_vma_collect_hole(unsigned long start, |
| unsigned long end, |
| __always_unused int depth, |
| struct mm_walk *walk) |
| { |
| struct migrate_vma *migrate = walk->private; |
| unsigned long addr; |
| |
| /* Only allow populating anonymous memory. */ |
| if (!vma_is_anonymous(walk->vma)) |
| return migrate_vma_collect_skip(start, end, walk); |
| |
| for (addr = start; addr < end; addr += PAGE_SIZE) { |
| migrate->src[migrate->npages] = MIGRATE_PFN_MIGRATE; |
| migrate->dst[migrate->npages] = 0; |
| migrate->npages++; |
| migrate->cpages++; |
| } |
| |
| return 0; |
| } |
| |
| static int migrate_vma_collect_pmd(pmd_t *pmdp, |
| unsigned long start, |
| unsigned long end, |
| struct mm_walk *walk) |
| { |
| struct migrate_vma *migrate = walk->private; |
| struct vm_area_struct *vma = walk->vma; |
| struct mm_struct *mm = vma->vm_mm; |
| unsigned long addr = start, unmapped = 0; |
| spinlock_t *ptl; |
| pte_t *ptep; |
| |
| again: |
| if (pmd_none(*pmdp)) |
| return migrate_vma_collect_hole(start, end, -1, walk); |
| |
| if (pmd_trans_huge(*pmdp)) { |
| struct page *page; |
| |
| ptl = pmd_lock(mm, pmdp); |
| if (unlikely(!pmd_trans_huge(*pmdp))) { |
| spin_unlock(ptl); |
| goto again; |
| } |
| |
| page = pmd_page(*pmdp); |
| if (is_huge_zero_page(page)) { |
| spin_unlock(ptl); |
| split_huge_pmd(vma, pmdp, addr); |
| if (pmd_trans_unstable(pmdp)) |
| return migrate_vma_collect_skip(start, end, |
| walk); |
| } else { |
| int ret; |
| |
| get_page(page); |
| spin_unlock(ptl); |
| if (unlikely(!trylock_page(page))) |
| return migrate_vma_collect_skip(start, end, |
| walk); |
| ret = split_huge_page(page); |
| unlock_page(page); |
| put_page(page); |
| if (ret) |
| return migrate_vma_collect_skip(start, end, |
| walk); |
| if (pmd_none(*pmdp)) |
| return migrate_vma_collect_hole(start, end, -1, |
| walk); |
| } |
| } |
| |
| if (unlikely(pmd_bad(*pmdp))) |
| return migrate_vma_collect_skip(start, end, walk); |
| |
| ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl); |
| arch_enter_lazy_mmu_mode(); |
| |
| for (; addr < end; addr += PAGE_SIZE, ptep++) { |
| unsigned long mpfn = 0, pfn; |
| struct page *page; |
| swp_entry_t entry; |
| pte_t pte; |
| |
| pte = *ptep; |
| |
| if (pte_none(pte)) { |
| if (vma_is_anonymous(vma)) { |
| mpfn = MIGRATE_PFN_MIGRATE; |
| migrate->cpages++; |
| } |
| goto next; |
| } |
| |
| if (!pte_present(pte)) { |
| /* |
| * Only care about unaddressable device page special |
| * page table entry. Other special swap entries are not |
| * migratable, and we ignore regular swapped page. |
| */ |
| entry = pte_to_swp_entry(pte); |
| if (!is_device_private_entry(entry)) |
| goto next; |
| |
| page = pfn_swap_entry_to_page(entry); |
| if (!(migrate->flags & |
| MIGRATE_VMA_SELECT_DEVICE_PRIVATE) || |
| page->pgmap->owner != migrate->pgmap_owner) |
| goto next; |
| |
| mpfn = migrate_pfn(page_to_pfn(page)) | |
| MIGRATE_PFN_MIGRATE; |
| if (is_writable_device_private_entry(entry)) |
| mpfn |= MIGRATE_PFN_WRITE; |
| } else { |
| if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) |
| goto next; |
| pfn = pte_pfn(pte); |
| if (is_zero_pfn(pfn)) { |
| mpfn = MIGRATE_PFN_MIGRATE; |
| migrate->cpages++; |
| goto next; |
| } |
| page = vm_normal_page(migrate->vma, addr, pte); |
| mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE; |
| mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0; |
| } |
| |
| /* FIXME support THP */ |
| if (!page || !page->mapping || PageTransCompound(page)) { |
| mpfn = 0; |
| goto next; |
| } |
| |
| /* |
| * By getting a reference on the page we pin it and that blocks |
| * any kind of migration. Side effect is that it "freezes" the |
| * pte. |
| * |
| * We drop this reference after isolating the page from the lru |
| * for non device page (device page are not on the lru and thus |
| * can't be dropped from it). |
| */ |
| get_page(page); |
| migrate->cpages++; |
| |
| /* |
| * Optimize for the common case where page is only mapped once |
| * in one process. If we can lock the page, then we can safely |
| * set up a special migration page table entry now. |
| */ |
| if (trylock_page(page)) { |
| pte_t swp_pte; |
| |
| mpfn |= MIGRATE_PFN_LOCKED; |
| ptep_get_and_clear(mm, addr, ptep); |
| |
| /* Setup special migration page table entry */ |
| if (mpfn & MIGRATE_PFN_WRITE) |
| entry = make_writable_migration_entry( |
| page_to_pfn(page)); |
| else |
| entry = make_readable_migration_entry( |
| page_to_pfn(page)); |
| swp_pte = swp_entry_to_pte(entry); |
| if (pte_present(pte)) { |
| if (pte_soft_dirty(pte)) |
| swp_pte = pte_swp_mksoft_dirty(swp_pte); |
| if (pte_uffd_wp(pte)) |
| swp_pte = pte_swp_mkuffd_wp(swp_pte); |
| } else { |
| if (pte_swp_soft_dirty(pte)) |
| swp_pte = pte_swp_mksoft_dirty(swp_pte); |
| if (pte_swp_uffd_wp(pte)) |
| swp_pte = pte_swp_mkuffd_wp(swp_pte); |
| } |
| set_pte_at(mm, addr, ptep, swp_pte); |
| |
| /* |
| * This is like regular unmap: we remove the rmap and |
| * drop page refcount. Page won't be freed, as we took |
| * a reference just above. |
| */ |
| page_remove_rmap(page, false); |
| put_page(page); |
| |
| if (pte_present(pte)) |
| unmapped++; |
| } |
| |
| next: |
| migrate->dst[migrate->npages] = 0; |
| migrate->src[migrate->npages++] = mpfn; |
| } |
| arch_leave_lazy_mmu_mode(); |
| pte_unmap_unlock(ptep - 1, ptl); |
| |
| /* Only flush the TLB if we actually modified any entries */ |
| if (unmapped) |
| flush_tlb_range(walk->vma, start, end); |
| |
| return 0; |
| } |
| |
| static const struct mm_walk_ops migrate_vma_walk_ops = { |
| .pmd_entry = migrate_vma_collect_pmd, |
| .pte_hole = migrate_vma_collect_hole, |
| }; |
| |
| /* |
| * migrate_vma_collect() - collect pages over a range of virtual addresses |
| * @migrate: migrate struct containing all migration information |
| * |
| * This will walk the CPU page table. For each virtual address backed by a |
| * valid page, it updates the src array and takes a reference on the page, in |
| * order to pin the page until we lock it and unmap it. |
| */ |
| static void migrate_vma_collect(struct migrate_vma *migrate) |
| { |
| struct mmu_notifier_range range; |
| |
| /* |
| * Note that the pgmap_owner is passed to the mmu notifier callback so |
| * that the registered device driver can skip invalidating device |
| * private page mappings that won't be migrated. |
| */ |
| mmu_notifier_range_init_owner(&range, MMU_NOTIFY_MIGRATE, 0, |
| migrate->vma, migrate->vma->vm_mm, migrate->start, migrate->end, |
| migrate->pgmap_owner); |
| mmu_notifier_invalidate_range_start(&range); |
| |
| walk_page_range(migrate->vma->vm_mm, migrate->start, migrate->end, |
| &migrate_vma_walk_ops, migrate); |
| |
| mmu_notifier_invalidate_range_end(&range); |
| migrate->end = migrate->start + (migrate->npages << PAGE_SHIFT); |
| } |
| |
| /* |
| * migrate_vma_check_page() - check if page is pinned or not |
| * @page: struct page to check |
| * |
| * Pinned pages cannot be migrated. This is the same test as in |
| * folio_migrate_mapping(), except that here we allow migration of a |
| * ZONE_DEVICE page. |
| */ |
| static bool migrate_vma_check_page(struct page *page) |
| { |
| /* |
| * One extra ref because caller holds an extra reference, either from |
| * isolate_lru_page() for a regular page, or migrate_vma_collect() for |
| * a device page. |
| */ |
| int extra = 1; |
| |
| /* |
| * FIXME support THP (transparent huge page), it is bit more complex to |
| * check them than regular pages, because they can be mapped with a pmd |
| * or with a pte (split pte mapping). |
| */ |
| if (PageCompound(page)) |
| return false; |
| |
| /* Page from ZONE_DEVICE have one extra reference */ |
| if (is_zone_device_page(page)) { |
| /* |
| * Private page can never be pin as they have no valid pte and |
| * GUP will fail for those. Yet if there is a pending migration |
| * a thread might try to wait on the pte migration entry and |
| * will bump the page reference count. Sadly there is no way to |
| * differentiate a regular pin from migration wait. Hence to |
| * avoid 2 racing thread trying to migrate back to CPU to enter |
| * infinite loop (one stopping migration because the other is |
| * waiting on pte migration entry). We always return true here. |
| * |
| * FIXME proper solution is to rework migration_entry_wait() so |
| * it does not need to take a reference on page. |
| */ |
| return is_device_private_page(page); |
| } |
| |
| /* For file back page */ |
| if (page_mapping(page)) |
| extra += 1 + page_has_private(page); |
| |
| if ((page_count(page) - extra) > page_mapcount(page)) |
| return false; |
| |
| return true; |
| } |
| |
| /* |
| * migrate_vma_prepare() - lock pages and isolate them from the lru |
| * @migrate: migrate struct containing all migration information |
| * |
| * This locks pages that have been collected by migrate_vma_collect(). Once each |
| * page is locked it is isolated from the lru (for non-device pages). Finally, |
| * the ref taken by migrate_vma_collect() is dropped, as locked pages cannot be |
| * migrated by concurrent kernel threads. |
| */ |
| static void migrate_vma_prepare(struct migrate_vma *migrate) |
| { |
| const unsigned long npages = migrate->npages; |
| const unsigned long start = migrate->start; |
| unsigned long addr, i, restore = 0; |
| bool allow_drain = true; |
| |
| lru_add_drain(); |
| |
| for (i = 0; (i < npages) && migrate->cpages; i++) { |
| struct page *page = migrate_pfn_to_page(migrate->src[i]); |
| bool remap = true; |
| |
| if (!page) |
| continue; |
| |
| if (!(migrate->src[i] & MIGRATE_PFN_LOCKED)) { |
| /* |
| * Because we are migrating several pages there can be |
| * a deadlock between 2 concurrent migration where each |
| * are waiting on each other page lock. |
| * |
| * Make migrate_vma() a best effort thing and backoff |
| * for any page we can not lock right away. |
| */ |
| if (!trylock_page(page)) { |
| migrate->src[i] = 0; |
| migrate->cpages--; |
| put_page(page); |
| continue; |
| } |
| remap = false; |
| migrate->src[i] |= MIGRATE_PFN_LOCKED; |
| } |
| |
| /* ZONE_DEVICE pages are not on LRU */ |
| if (!is_zone_device_page(page)) { |
| if (!PageLRU(page) && allow_drain) { |
| /* Drain CPU's pagevec */ |
| lru_add_drain_all(); |
| allow_drain = false; |
| } |
| |
| if (isolate_lru_page(page)) { |
| if (remap) { |
| migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; |
| migrate->cpages--; |
| restore++; |
| } else { |
| migrate->src[i] = 0; |
| unlock_page(page); |
| migrate->cpages--; |
| put_page(page); |
| } |
| continue; |
| } |
| |
| /* Drop the reference we took in collect */ |
| put_page(page); |
| } |
| |
| if (!migrate_vma_check_page(page)) { |
| if (remap) { |
| migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; |
| migrate->cpages--; |
| restore++; |
| |
| if (!is_zone_device_page(page)) { |
| get_page(page); |
| putback_lru_page(page); |
| } |
| } else { |
| migrate->src[i] = 0; |
| unlock_page(page); |
| migrate->cpages--; |
| |
| if (!is_zone_device_page(page)) |
| putback_lru_page(page); |
| else |
| put_page(page); |
| } |
| } |
| } |
| |
| for (i = 0, addr = start; i < npages && restore; i++, addr += PAGE_SIZE) { |
| struct page *page = migrate_pfn_to_page(migrate->src[i]); |
| |
| if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE)) |
| continue; |
| |
| remove_migration_pte(page, migrate->vma, addr, page); |
| |
| migrate->src[i] = 0; |
| unlock_page(page); |
| put_page(page); |
| restore--; |
| } |
| } |
| |
| /* |
| * migrate_vma_unmap() - replace page mapping with special migration pte entry |
| * @migrate: migrate struct containing all migration information |
| * |
| * Replace page mapping (CPU page table pte) with a special migration pte entry |
| * and check again if it has been pinned. Pinned pages are restored because we |
| * cannot migrate them. |
| * |
| * This is the last step before we call the device driver callback to allocate |
| * destination memory and copy contents of original page over to new page. |
| */ |
| static void migrate_vma_unmap(struct migrate_vma *migrate) |
| { |
| const unsigned long npages = migrate->npages; |
| const unsigned long start = migrate->start; |
| unsigned long addr, i, restore = 0; |
| |
| for (i = 0; i < npages; i++) { |
| struct page *page = migrate_pfn_to_page(migrate->src[i]); |
| |
| if (!page || !(migrate->src[i] & MIGRATE_PFN_MIGRATE)) |
| continue; |
| |
| if (page_mapped(page)) { |
| try_to_migrate(page, 0); |
| if (page_mapped(page)) |
| goto restore; |
| } |
| |
| if (migrate_vma_check_page(page)) |
| continue; |
| |
| restore: |
| migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; |
| migrate->cpages--; |
| restore++; |
| } |
| |
| for (addr = start, i = 0; i < npages && restore; addr += PAGE_SIZE, i++) { |
| struct page *page = migrate_pfn_to_page(migrate->src[i]); |
| |
| if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE)) |
| continue; |
| |
| remove_migration_ptes(page, page, false); |
| |
| migrate->src[i] = 0; |
| unlock_page(page); |
| restore--; |
| |
| if (is_zone_device_page(page)) |
| put_page(page); |
| else |
| putback_lru_page(page); |
| } |
| } |
| |
| /** |
| * migrate_vma_setup() - prepare to migrate a range of memory |
| * @args: contains the vma, start, and pfns arrays for the migration |
| * |
| * Returns: negative errno on failures, 0 when 0 or more pages were migrated |
| * without an error. |
| * |
| * Prepare to migrate a range of memory virtual address range by collecting all |
| * the pages backing each virtual address in the range, saving them inside the |
| * src array. Then lock those pages and unmap them. Once the pages are locked |
| * and unmapped, check whether each page is pinned or not. Pages that aren't |
| * pinned have the MIGRATE_PFN_MIGRATE flag set (by this function) in the |
| * corresponding src array entry. Then restores any pages that are pinned, by |
| * remapping and unlocking those pages. |
| * |
| * The caller should then allocate destination memory and copy source memory to |
| * it for all those entries (ie with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE |
| * flag set). Once these are allocated and copied, the caller must update each |
| * corresponding entry in the dst array with the pfn value of the destination |
| * page and with the MIGRATE_PFN_VALID and MIGRATE_PFN_LOCKED flags set |
| * (destination pages must have their struct pages locked, via lock_page()). |
| * |
| * Note that the caller does not have to migrate all the pages that are marked |
| * with MIGRATE_PFN_MIGRATE flag in src array unless this is a migration from |
| * device memory to system memory. If the caller cannot migrate a device page |
| * back to system memory, then it must return VM_FAULT_SIGBUS, which has severe |
| * consequences for the userspace process, so it must be avoided if at all |
| * possible. |
| * |
| * For empty entries inside CPU page table (pte_none() or pmd_none() is true) we |
| * do set MIGRATE_PFN_MIGRATE flag inside the corresponding source array thus |
| * allowing the caller to allocate device memory for those unbacked virtual |
| * addresses. For this the caller simply has to allocate device memory and |
| * properly set the destination entry like for regular migration. Note that |
| * this can still fail, and thus inside the device driver you must check if the |
| * migration was successful for those entries after calling migrate_vma_pages(), |
| * just like for regular migration. |
| * |
| * After that, the callers must call migrate_vma_pages() to go over each entry |
| * in the src array that has the MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag |
| * set. If the corresponding entry in dst array has MIGRATE_PFN_VALID flag set, |
| * then migrate_vma_pages() to migrate struct page information from the source |
| * struct page to the destination struct page. If it fails to migrate the |
| * struct page information, then it clears the MIGRATE_PFN_MIGRATE flag in the |
| * src array. |
| * |
| * At this point all successfully migrated pages have an entry in the src |
| * array with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag set and the dst |
| * array entry with MIGRATE_PFN_VALID flag set. |
| * |
| * Once migrate_vma_pages() returns the caller may inspect which pages were |
| * successfully migrated, and which were not. Successfully migrated pages will |
| * have the MIGRATE_PFN_MIGRATE flag set for their src array entry. |
| * |
| * It is safe to update device page table after migrate_vma_pages() because |
| * both destination and source page are still locked, and the mmap_lock is held |
| * in read mode (hence no one can unmap the range being migrated). |
| * |
| * Once the caller is done cleaning up things and updating its page table (if it |
| * chose to do so, this is not an obligation) it finally calls |
| * migrate_vma_finalize() to update the CPU page table to point to new pages |
| * for successfully migrated pages or otherwise restore the CPU page table to |
| * point to the original source pages. |
| */ |
| int migrate_vma_setup(struct migrate_vma *args) |
| { |
| long nr_pages = (args->end - args->start) >> PAGE_SHIFT; |
| |
| args->start &= PAGE_MASK; |
| args->end &= PAGE_MASK; |
| if (!args->vma || is_vm_hugetlb_page(args->vma) || |
| (args->vma->vm_flags & VM_SPECIAL) || vma_is_dax(args->vma)) |
| return -EINVAL; |
| if (nr_pages <= 0) |
| return -EINVAL; |
| if (args->start < args->vma->vm_start || |
| args->start >= args->vma->vm_end) |
| return -EINVAL; |
| if (args->end <= args->vma->vm_start || args->end > args->vma->vm_end) |
| return -EINVAL; |
| if (!args->src || !args->dst) |
| return -EINVAL; |
| |
| memset(args->src, 0, sizeof(*args->src) * nr_pages); |
| args->cpages = 0; |
| args->npages = 0; |
| |
| migrate_vma_collect(args); |
| |
| if (args->cpages) |
| migrate_vma_prepare(args); |
| if (args->cpages) |
| migrate_vma_unmap(args); |
| |
| /* |
| * At this point pages are locked and unmapped, and thus they have |
| * stable content and can safely be copied to destination memory that |
| * is allocated by the drivers. |
| */ |
| return 0; |
| |
| } |
| EXPORT_SYMBOL(migrate_vma_setup); |
| |
| /* |
| * This code closely matches the code in: |
| * __handle_mm_fault() |
| * handle_pte_fault() |
| * do_anonymous_page() |
| * to map in an anonymous zero page but the struct page will be a ZONE_DEVICE |
| * private page. |
| */ |
| static void migrate_vma_insert_page(struct migrate_vma *migrate, |
| unsigned long addr, |
| struct page *page, |
| unsigned long *src) |
| { |
| struct vm_area_struct *vma = migrate->vma; |
| struct mm_struct *mm = vma->vm_mm; |
| bool flush = false; |
| spinlock_t *ptl; |
| pte_t entry; |
| pgd_t *pgdp; |
| p4d_t *p4dp; |
| pud_t *pudp; |
| pmd_t *pmdp; |
| pte_t *ptep; |
| |
| /* Only allow populating anonymous memory */ |
| if (!vma_is_anonymous(vma)) |
| goto abort; |
| |
| pgdp = pgd_offset(mm, addr); |
| p4dp = p4d_alloc(mm, pgdp, addr); |
| if (!p4dp) |
| goto abort; |
| pudp = pud_alloc(mm, p4dp, addr); |
| if (!pudp) |
| goto abort; |
| pmdp = pmd_alloc(mm, pudp, addr); |
| if (!pmdp) |
| goto abort; |
| |
| if (pmd_trans_huge(*pmdp) || pmd_devmap(*pmdp)) |
| goto abort; |
| |
| /* |
| * Use pte_alloc() instead of pte_alloc_map(). We can't run |
| * pte_offset_map() on pmds where a huge pmd might be created |
| * from a different thread. |
| * |
| * pte_alloc_map() is safe to use under mmap_write_lock(mm) or when |
| * parallel threads are excluded by other means. |
| * |
| * Here we only have mmap_read_lock(mm). |
| */ |
| if (pte_alloc(mm, pmdp)) |
| goto abort; |
| |
| /* See the comment in pte_alloc_one_map() */ |
| if (unlikely(pmd_trans_unstable(pmdp))) |
| goto abort; |
| |
| if (unlikely(anon_vma_prepare(vma))) |
| goto abort; |
| if (mem_cgroup_charge(page_folio(page), vma->vm_mm, GFP_KERNEL)) |
| goto abort; |
| |
| /* |
| * The memory barrier inside __SetPageUptodate makes sure that |
| * preceding stores to the page contents become visible before |
| * the set_pte_at() write. |
| */ |
| __SetPageUptodate(page); |
| |
| if (is_zone_device_page(page)) { |
| if (is_device_private_page(page)) { |
| swp_entry_t swp_entry; |
| |
| if (vma->vm_flags & VM_WRITE) |
| swp_entry = make_writable_device_private_entry( |
| page_to_pfn(page)); |
| else |
| swp_entry = make_readable_device_private_entry( |
| page_to_pfn(page)); |
| entry = swp_entry_to_pte(swp_entry); |
| } else { |
| /* |
| * For now we only support migrating to un-addressable |
| * device memory. |
| */ |
| pr_warn_once("Unsupported ZONE_DEVICE page type.\n"); |
| goto abort; |
| } |
| } else { |
| entry = mk_pte(page, vma->vm_page_prot); |
| if (vma->vm_flags & VM_WRITE) |
| entry = pte_mkwrite(pte_mkdirty(entry)); |
| } |
| |
| ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl); |
| |
| if (check_stable_address_space(mm)) |
| goto unlock_abort; |
| |
| if (pte_present(*ptep)) { |
| unsigned long pfn = pte_pfn(*ptep); |
| |
| if (!is_zero_pfn(pfn)) |
| goto unlock_abort; |
| flush = true; |
| } else if (!pte_none(*ptep)) |
| goto unlock_abort; |
| |
| /* |
| * Check for userfaultfd but do not deliver the fault. Instead, |
| * just back off. |
| */ |
| if (userfaultfd_missing(vma)) |
| goto unlock_abort; |
| |
| inc_mm_counter(mm, MM_ANONPAGES); |
| page_add_new_anon_rmap(page, vma, addr, false); |
| if (!is_zone_device_page(page)) |
| lru_cache_add_inactive_or_unevictable(page, vma); |
| get_page(page); |
| |
| if (flush) { |
| flush_cache_page(vma, addr, pte_pfn(*ptep)); |
| ptep_clear_flush_notify(vma, addr, ptep); |
| set_pte_at_notify(mm, addr, ptep, entry); |
| update_mmu_cache(vma, addr, ptep); |
| } else { |
| /* No need to invalidate - it was non-present before */ |
| set_pte_at(mm, addr, ptep, entry); |
| update_mmu_cache(vma, addr, ptep); |
| } |
| |
| pte_unmap_unlock(ptep, ptl); |
| *src = MIGRATE_PFN_MIGRATE; |
| return; |
| |
| unlock_abort: |
| pte_unmap_unlock(ptep, ptl); |
| abort: |
| *src &= ~MIGRATE_PFN_MIGRATE; |
| } |
| |
| /** |
| * migrate_vma_pages() - migrate meta-data from src page to dst page |
| * @migrate: migrate struct containing all migration information |
| * |
| * This migrates struct page meta-data from source struct page to destination |
| * struct page. This effectively finishes the migration from source page to the |
| * destination page. |
| */ |
| void migrate_vma_pages(struct migrate_vma *migrate) |
| { |
| const unsigned long npages = migrate->npages; |
| const unsigned long start = migrate->start; |
| struct mmu_notifier_range range; |
| unsigned long addr, i; |
| bool notified = false; |
| |
| for (i = 0, addr = start; i < npages; addr += PAGE_SIZE, i++) { |
| struct page *newpage = migrate_pfn_to_page(migrate->dst[i]); |
| struct page *page = migrate_pfn_to_page(migrate->src[i]); |
| struct address_space *mapping; |
| int r; |
| |
| if (!newpage) { |
| migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; |
| continue; |
| } |
| |
| if (!page) { |
| if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE)) |
| continue; |
| if (!notified) { |
| notified = true; |
| |
| mmu_notifier_range_init_owner(&range, |
| MMU_NOTIFY_MIGRATE, 0, migrate->vma, |
| migrate->vma->vm_mm, addr, migrate->end, |
| migrate->pgmap_owner); |
| mmu_notifier_invalidate_range_start(&range); |
| } |
| migrate_vma_insert_page(migrate, addr, newpage, |
| &migrate->src[i]); |
| continue; |
| } |
| |
| mapping = page_mapping(page); |
| |
| if (is_zone_device_page(newpage)) { |
| if (is_device_private_page(newpage)) { |
| /* |
| * For now only support private anonymous when |
| * migrating to un-addressable device memory. |
| */ |
| if (mapping) { |
| migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; |
| continue; |
| } |
| } else { |
| /* |
| * Other types of ZONE_DEVICE page are not |
| * supported. |
| */ |
| migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; |
| continue; |
| } |
| } |
| |
| r = migrate_page(mapping, newpage, page, MIGRATE_SYNC_NO_COPY); |
| if (r != MIGRATEPAGE_SUCCESS) |
| migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; |
| } |
| |
| /* |
| * No need to double call mmu_notifier->invalidate_range() callback as |
| * the above ptep_clear_flush_notify() inside migrate_vma_insert_page() |
| * did already call it. |
| */ |
| if (notified) |
| mmu_notifier_invalidate_range_only_end(&range); |
| } |
| EXPORT_SYMBOL(migrate_vma_pages); |
| |
| /** |
| * migrate_vma_finalize() - restore CPU page table entry |
| * @migrate: migrate struct containing all migration information |
| * |
| * This replaces the special migration pte entry with either a mapping to the |
| * new page if migration was successful for that page, or to the original page |
| * otherwise. |
| * |
| * This also unlocks the pages and puts them back on the lru, or drops the extra |
| * refcount, for device pages. |
| */ |
| void migrate_vma_finalize(struct migrate_vma *migrate) |
| { |
| const unsigned long npages = migrate->npages; |
| unsigned long i; |
| |
| for (i = 0; i < npages; i++) { |
| struct page *newpage = migrate_pfn_to_page(migrate->dst[i]); |
| struct page *page = migrate_pfn_to_page(migrate->src[i]); |
| |
| if (!page) { |
| if (newpage) { |
| unlock_page(newpage); |
| put_page(newpage); |
| } |
| continue; |
| } |
| |
| if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE) || !newpage) { |
| if (newpage) { |
| unlock_page(newpage); |
| put_page(newpage); |
| } |
| newpage = page; |
| } |
| |
| remove_migration_ptes(page, newpage, false); |
| unlock_page(page); |
| |
| if (is_zone_device_page(page)) |
| put_page(page); |
| else |
| putback_lru_page(page); |
| |
| if (newpage != page) { |
| unlock_page(newpage); |
| if (is_zone_device_page(newpage)) |
| put_page(newpage); |
| else |
| putback_lru_page(newpage); |
| } |
| } |
| } |
| EXPORT_SYMBOL(migrate_vma_finalize); |
| #endif /* CONFIG_DEVICE_PRIVATE */ |
| |
| #if defined(CONFIG_HOTPLUG_CPU) |
| /* Disable reclaim-based migration. */ |
| static void __disable_all_migrate_targets(void) |
| { |
| int node; |
| |
| for_each_online_node(node) |
| node_demotion[node] = NUMA_NO_NODE; |
| } |
| |
| static void disable_all_migrate_targets(void) |
| { |
| __disable_all_migrate_targets(); |
| |
| /* |
| * Ensure that the "disable" is visible across the system. |
| * Readers will see either a combination of before+disable |
| * state or disable+after. They will never see before and |
| * after state together. |
| * |
| * The before+after state together might have cycles and |
| * could cause readers to do things like loop until this |
| * function finishes. This ensures they can only see a |
| * single "bad" read and would, for instance, only loop |
| * once. |
| */ |
| synchronize_rcu(); |
| } |
| |
| /* |
| * Find an automatic demotion target for 'node'. |
| * Failing here is OK. It might just indicate |
| * being at the end of a chain. |
| */ |
| static int establish_migrate_target(int node, nodemask_t *used) |
| { |
| int migration_target; |
| |
| /* |
| * Can not set a migration target on a |
| * node with it already set. |
| * |
| * No need for READ_ONCE() here since this |
| * in the write path for node_demotion[]. |
| * This should be the only thread writing. |
| */ |
| if (node_demotion[node] != NUMA_NO_NODE) |
| return NUMA_NO_NODE; |
| |
| migration_target = find_next_best_node(node, used); |
| if (migration_target == NUMA_NO_NODE) |
| return NUMA_NO_NODE; |
| |
| node_demotion[node] = migration_target; |
| |
| return migration_target; |
| } |
| |
| /* |
| * When memory fills up on a node, memory contents can be |
| * automatically migrated to another node instead of |
| * discarded at reclaim. |
| * |
| * Establish a "migration path" which will start at nodes |
| * with CPUs and will follow the priorities used to build the |
| * page allocator zonelists. |
| * |
| * The difference here is that cycles must be avoided. If |
| * node0 migrates to node1, then neither node1, nor anything |
| * node1 migrates to can migrate to node0. |
| * |
| * This function can run simultaneously with readers of |
| * node_demotion[]. However, it can not run simultaneously |
| * with itself. Exclusion is provided by memory hotplug events |
| * being single-threaded. |
| */ |
| static void __set_migration_target_nodes(void) |
| { |
| nodemask_t next_pass = NODE_MASK_NONE; |
| nodemask_t this_pass = NODE_MASK_NONE; |
| nodemask_t used_targets = NODE_MASK_NONE; |
| int node; |
| |
| /* |
| * Avoid any oddities like cycles that could occur |
| * from changes in the topology. This will leave |
| * a momentary gap when migration is disabled. |
| */ |
| disable_all_migrate_targets(); |
| |
| /* |
| * Allocations go close to CPUs, first. Assume that |
| * the migration path starts at the nodes with CPUs. |
| */ |
| next_pass = node_states[N_CPU]; |
| again: |
| this_pass = next_pass; |
| next_pass = NODE_MASK_NONE; |
| /* |
| * To avoid cycles in the migration "graph", ensure |
| * that migration sources are not future targets by |
| * setting them in 'used_targets'. Do this only |
| * once per pass so that multiple source nodes can |
| * share a target node. |
| * |
| * 'used_targets' will become unavailable in future |
| * passes. This limits some opportunities for |
| * multiple source nodes to share a destination. |
| */ |
| nodes_or(used_targets, used_targets, this_pass); |
| for_each_node_mask(node, this_pass) { |
| int target_node = establish_migrate_target(node, &used_targets); |
| |
| if (target_node == NUMA_NO_NODE) |
| continue; |
| |
| /* |
| * Visit targets from this pass in the next pass. |
| * Eventually, every node will have been part of |
| * a pass, and will become set in 'used_targets'. |
| */ |
| node_set(target_node, next_pass); |
| } |
| /* |
| * 'next_pass' contains nodes which became migration |
| * targets in this pass. Make additional passes until |
| * no more migrations targets are available. |
| */ |
| if (!nodes_empty(next_pass)) |
| goto again; |
| } |
| |
| /* |
| * For callers that do not hold get_online_mems() already. |
| */ |
| static void set_migration_target_nodes(void) |
| { |
| get_online_mems(); |
| __set_migration_target_nodes(); |
| put_online_mems(); |
| } |
| |
| /* |
| * This leaves migrate-on-reclaim transiently disabled between |
| * the MEM_GOING_OFFLINE and MEM_OFFLINE events. This runs |
| * whether reclaim-based migration is enabled or not, which |
| * ensures that the user can turn reclaim-based migration at |
| * any time without needing to recalculate migration targets. |
| * |
| * These callbacks already hold get_online_mems(). That is why |
| * __set_migration_target_nodes() can be used as opposed to |
| * set_migration_target_nodes(). |
| */ |
| static int __meminit migrate_on_reclaim_callback(struct notifier_block *self, |
| unsigned long action, void *_arg) |
| { |
| struct memory_notify *arg = _arg; |
| |
| /* |
| * Only update the node migration order when a node is |
| * changing status, like online->offline. This avoids |
| * the overhead of synchronize_rcu() in most cases. |
| */ |
| if (arg->status_change_nid < 0) |
| return notifier_from_errno(0); |
| |
| switch (action) { |
| case MEM_GOING_OFFLINE: |
| /* |
| * Make sure there are not transient states where |
| * an offline node is a migration target. This |
| * will leave migration disabled until the offline |
| * completes and the MEM_OFFLINE case below runs. |
| */ |
| disable_all_migrate_targets(); |
| break; |
| case MEM_OFFLINE: |
| case MEM_ONLINE: |
| /* |
| * Recalculate the target nodes once the node |
| * reaches its final state (online or offline). |
| */ |
| __set_migration_target_nodes(); |
| break; |
| case MEM_CANCEL_OFFLINE: |
| /* |
| * MEM_GOING_OFFLINE disabled all the migration |
| * targets. Reenable them. |
| */ |
| __set_migration_target_nodes(); |
| break; |
| case MEM_GOING_ONLINE: |
| case MEM_CANCEL_ONLINE: |
| break; |
| } |
| |
| return notifier_from_errno(0); |
| } |
| |
| /* |
| * React to hotplug events that might affect the migration targets |
| * like events that online or offline NUMA nodes. |
| * |
| * The ordering is also currently dependent on which nodes have |
| * CPUs. That means we need CPU on/offline notification too. |
| */ |
| static int migration_online_cpu(unsigned int cpu) |
| { |
| set_migration_target_nodes(); |
| return 0; |
| } |
| |
| static int migration_offline_cpu(unsigned int cpu) |
| { |
| set_migration_target_nodes(); |
| return 0; |
| } |
| |
| static int __init migrate_on_reclaim_init(void) |
| { |
| int ret; |
| |
| ret = cpuhp_setup_state_nocalls(CPUHP_MM_DEMOTION_DEAD, "mm/demotion:offline", |
| NULL, migration_offline_cpu); |
| /* |
| * In the unlikely case that this fails, the automatic |
| * migration targets may become suboptimal for nodes |
| * where N_CPU changes. With such a small impact in a |
| * rare case, do not bother trying to do anything special. |
| */ |
| WARN_ON(ret < 0); |
| ret = cpuhp_setup_state(CPUHP_AP_MM_DEMOTION_ONLINE, "mm/demotion:online", |
| migration_online_cpu, NULL); |
| WARN_ON(ret < 0); |
| |
| hotplug_memory_notifier(migrate_on_reclaim_callback, 100); |
| return 0; |
| } |
| late_initcall(migrate_on_reclaim_init); |
| #endif /* CONFIG_HOTPLUG_CPU */ |