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Diffstat (limited to 'mm/migrate.c')
| -rw-r--r-- | mm/migrate.c | 3122 |
1 files changed, 3122 insertions, 0 deletions
diff --git a/mm/migrate.c b/mm/migrate.c new file mode 100644 index 000000000..fcb7eb6a6 --- /dev/null +++ b/mm/migrate.c @@ -0,0 +1,3122 @@ +// 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 <asm/tlbflush.h> + +#define CREATE_TRACE_POINTS +#include <trace/events/migrate.h> + +#include "internal.h" + +/* + * migrate_prep() needs to be called before we start compiling a list of pages + * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is + * undesirable, use migrate_prep_local() + */ +int migrate_prep(void) +{ + /* + * Clear the LRU lists so pages can be isolated. + * Note that pages may be moved off the LRU after we have + * drained them. Those pages will fail to migrate like other + * pages that may be busy. + */ + lru_add_drain_all(); + + return 0; +} + +/* Do the necessary work of migrate_prep but not if it involves other CPUs */ +int migrate_prep_local(void) +{ + lru_add_drain(); + + return 0; +} + +int isolate_movable_page(struct page *page, isolate_mode_t mode) +{ + struct address_space *mapping; + + /* + * Avoid burning cycles with pages that are yet under __free_pages(), + * or just got freed under us. + * + * In case we 'win' a race for a movable page being freed under us and + * raise its refcount preventing __free_pages() from doing its job + * the put_page() at the end of this block will take care of + * release this page, thus avoiding a nasty leakage. + */ + if (unlikely(!get_page_unless_zero(page))) + goto out; + + /* + * Check PageMovable before holding a PG_lock because page's owner + * assumes anybody doesn't touch PG_lock of newly allocated page + * so unconditionally 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; +} + +/* It should be called on page which is PG_movable */ +void putback_movable_page(struct page *page) +{ + struct address_space *mapping; + + VM_BUG_ON_PAGE(!PageLocked(page), page); + VM_BUG_ON_PAGE(!PageMovable(page), page); + VM_BUG_ON_PAGE(!PageIsolated(page), page); + + mapping = page_mapping(page); + mapping->a_ops->putback_page(page); + __ClearPageIsolated(page); +} + +/* + * Put previously isolated pages back onto the appropriate lists + * from where they were once taken off for compaction/migration. + * + * This function shall be used whenever the isolated pageset has been + * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range() + * and isolate_hugetlb(). + */ +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_write_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))) { + entry = make_device_private_entry(new, pte_write(pte)); + 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)) { + pte = pte_mkhuge(pte); + pte = arch_make_huge_pte(pte, vma, new, 0); + set_huge_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte); + if (PageAnon(new)) + hugepage_add_anon_rmap(new, vma, pvmw.address); + else + page_dup_rmap(new, true); + } else +#endif + { + set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte); + + if (PageAnon(new)) + page_add_anon_rmap(new, vma, pvmw.address, false); + else + page_add_file_rmap(new, false); + } + if (vma->vm_flags & VM_LOCKED && !PageTransCompound(new)) + mlock_vma_page(new); + + 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 = migration_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); + return; +out: + pte_unmap_unlock(ptep, ptl); +} + +void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, + unsigned long address) +{ + spinlock_t *ptl = pte_lockptr(mm, pmd); + pte_t *ptep = pte_offset_map(pmd, address); + __migration_entry_wait(mm, ptep, ptl); +} + +void migration_entry_wait_huge(struct vm_area_struct *vma, + struct mm_struct *mm, pte_t *pte) +{ + spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte); + __migration_entry_wait(mm, pte, ptl); +} + +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION +void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd) +{ + spinlock_t *ptl; + struct page *page; + + ptl = pmd_lock(mm, pmd); + if (!is_pmd_migration_entry(*pmd)) + goto unlock; + page = migration_entry_to_page(pmd_to_swp_entry(*pmd)); + if (!get_page_unless_zero(page)) + goto unlock; + spin_unlock(ptl); + put_and_wait_on_page_locked(page); + 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 += thp_nr_pages(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 migrate_page_move_mapping(struct address_space *mapping, + struct page *newpage, struct page *page, int extra_count) +{ + XA_STATE(xas, &mapping->i_pages, page_index(page)); + struct zone *oldzone, *newzone; + int dirty; + int expected_count = expected_page_refs(mapping, page) + extra_count; + int nr = thp_nr_pages(page); + + if (!mapping) { + /* Anonymous page without mapping */ + if (page_count(page) != expected_count) + return -EAGAIN; + + /* No turning back from here */ + newpage->index = page->index; + newpage->mapping = page->mapping; + if (PageSwapBacked(page)) + __SetPageSwapBacked(newpage); + + return MIGRATEPAGE_SUCCESS; + } + + oldzone = page_zone(page); + newzone = page_zone(newpage); + + xas_lock_irq(&xas); + 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; + } + + /* + * Now we know that no one else is looking at the page: + * no turning back from here. + */ + newpage->index = page->index; + newpage->mapping = page->mapping; + page_ref_add(newpage, nr); /* add cache reference */ + if (PageSwapBacked(page)) { + __SetPageSwapBacked(newpage); + if (PageSwapCache(page)) { + SetPageSwapCache(newpage); + set_page_private(newpage, page_private(page)); + } + } else { + VM_BUG_ON_PAGE(PageSwapCache(page), page); + } + + /* Move dirty while page refs frozen and newpage not yet exposed */ + dirty = PageDirty(page); + if (dirty) { + ClearPageDirty(page); + SetPageDirty(newpage); + } + + xas_store(&xas, newpage); + if (PageTransHuge(page)) { + int i; + + for (i = 1; i < nr; i++) { + xas_next(&xas); + xas_store(&xas, newpage); + } + } + + /* + * Drop cache reference from old page by unfreezing + * to one less reference. + * We know this isn't the last reference. + */ + page_ref_unfreeze(page, expected_count - 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 = page_memcg(page); + 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 (PageSwapBacked(page) && !PageSwapCache(page)) { + __mod_lruvec_state(old_lruvec, NR_SHMEM, -nr); + __mod_lruvec_state(new_lruvec, NR_SHMEM, nr); + } + 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(migrate_page_move_mapping); + +/* + * The expected number of remaining references is the same as that + * of migrate_page_move_mapping(). + */ +int migrate_huge_page_move_mapping(struct address_space *mapping, + struct page *newpage, struct page *page) +{ + 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; +} + +/* + * Gigantic pages are so large that we do not guarantee that page++ pointer + * arithmetic will work across the entire page. We need something more + * specialized. + */ +static void __copy_gigantic_page(struct page *dst, struct page *src, + int nr_pages) +{ + int i; + struct page *dst_base = dst; + struct page *src_base = src; + + for (i = 0; i < nr_pages; ) { + cond_resched(); + copy_highpage(dst, src); + + i++; + dst = mem_map_next(dst, dst_base, i); + src = mem_map_next(src, src_base, i); + } +} + +static void copy_huge_page(struct page *dst, struct page *src) +{ + int i; + int nr_pages; + + if (PageHuge(src)) { + /* hugetlbfs page */ + struct hstate *h = page_hstate(src); + nr_pages = pages_per_huge_page(h); + + if (unlikely(nr_pages > MAX_ORDER_NR_PAGES)) { + __copy_gigantic_page(dst, src, nr_pages); + return; + } + } else { + /* thp page */ + BUG_ON(!PageTransHuge(src)); + nr_pages = thp_nr_pages(src); + } + + for (i = 0; i < nr_pages; i++) { + cond_resched(); + copy_highpage(dst + i, src + i); + } +} + +/* + * Copy the page to its new location + */ +void migrate_page_states(struct page *newpage, struct page *page) +{ + int cpupid; + + if (PageError(page)) + SetPageError(newpage); + if (PageReferenced(page)) + SetPageReferenced(newpage); + if (PageUptodate(page)) + SetPageUptodate(newpage); + if (TestClearPageActive(page)) { + VM_BUG_ON_PAGE(PageUnevictable(page), page); + SetPageActive(newpage); + } else if (TestClearPageUnevictable(page)) + SetPageUnevictable(newpage); + if (PageWorkingset(page)) + SetPageWorkingset(newpage); + if (PageChecked(page)) + SetPageChecked(newpage); + if (PageMappedToDisk(page)) + SetPageMappedToDisk(newpage); + + /* Move dirty on pages not done by migrate_page_move_mapping() */ + if (PageDirty(page)) + SetPageDirty(newpage); + + if (page_is_young(page)) + set_page_young(newpage); + if (page_is_idle(page)) + set_page_idle(newpage); + + /* + * Copy NUMA information to the new page, to prevent over-eager + * future migrations of this same page. + */ + cpupid = page_cpupid_xchg_last(page, -1); + page_cpupid_xchg_last(newpage, cpupid); + + ksm_migrate_page(newpage, page); + /* + * Please do not reorder this without considering how mm/ksm.c's + * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache(). + */ + if (PageSwapCache(page)) + ClearPageSwapCache(page); + ClearPagePrivate(page); + set_page_private(page, 0); + + /* + * If any waiters have accumulated on the new page then + * wake them up. + */ + if (PageWriteback(newpage)) + end_page_writeback(newpage); + + /* + * 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 (PageReadahead(page)) + SetPageReadahead(newpage); + + copy_page_owner(page, newpage); + + if (!PageHuge(page)) + mem_cgroup_migrate(page, newpage); +} +EXPORT_SYMBOL(migrate_page_states); + +void migrate_page_copy(struct page *newpage, struct page *page) +{ + if (PageHuge(page) || PageTransHuge(page)) + copy_huge_page(newpage, page); + else + copy_highpage(newpage, page); + + migrate_page_states(newpage, page); +} +EXPORT_SYMBOL(migrate_page_copy); + +/************************************************************ + * Migration functions + ***********************************************************/ + +/* + * Common logic to directly migrate a single LRU page suitable for + * pages that do not use PagePrivate/PagePrivate2. + * + * Pages are locked upon entry and exit. + */ +int migrate_page(struct address_space *mapping, + struct page *newpage, struct page *page, + enum migrate_mode mode) +{ + int rc; + + BUG_ON(PageWriteback(page)); /* Writeback must be complete */ + + rc = migrate_page_move_mapping(mapping, newpage, page, 0); + + if (rc != MIGRATEPAGE_SUCCESS) + return rc; + + if (mode != MIGRATE_SYNC_NO_COPY) + migrate_page_copy(newpage, page); + else + migrate_page_states(newpage, page); + return MIGRATEPAGE_SUCCESS; +} +EXPORT_SYMBOL(migrate_page); + +#ifdef CONFIG_BLOCK +/* 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))) { + int i, nr = compound_nr(newpage); + + for (i = 0; i < nr; i++) + flush_dcache_page(newpage + i); + } + } +out: + return rc; +} + +static int __unmap_and_move(struct page *page, struct page *newpage, + int force, enum migrate_mode mode) +{ + int rc = -EAGAIN; + int page_was_mapped = 0; + struct anon_vma *anon_vma = NULL; + bool is_lru = !__PageMovable(page); + + if (!trylock_page(page)) { + if (!force || mode == MIGRATE_ASYNC) + goto out; + + /* + * It's not safe for direct compaction to call lock_page. + * For example, during page readahead pages are added locked + * to the LRU. Later, when the IO completes the pages are + * marked uptodate and unlocked. However, the queueing + * could be merging multiple pages for one bio (e.g. + * mpage_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_unmap(), page->mapcount goes down to 0 here. In this case, + * we cannot notice that anon_vma is freed while we migrates a page. + * This get_anon_vma() delays freeing anon_vma pointer until the end + * of migration. File cache pages are no problem because of page_lock() + * File Caches may use write_page() or lock_page() in migration, then, + * just care Anon page here. + * + * Only page_get_anon_vma() understands the subtleties of + * getting a hold on an anon_vma from outside one of its mms. + * But if we cannot get anon_vma, then we won't need it anyway, + * because that implies that the anon page is no longer mapped + * (and cannot be remapped so long as we hold the page lock). + */ + if (PageAnon(page) && !PageKsm(page)) + anon_vma = page_get_anon_vma(page); + + /* + * Block others from accessing the new page when we get around to + * establishing additional references. We are usually the only one + * holding a reference to newpage at this point. We used to have a BUG + * here if trylock_page(newpage) fails, but would like to allow for + * cases where there might be a race with the previous use of newpage. + * This is much like races on refcount of oldpage: just don't BUG(). + */ + if (unlikely(!trylock_page(newpage))) + goto out_unlock; + + if (unlikely(!is_lru)) { + rc = move_to_new_page(newpage, page, mode); + goto out_unlock_both; + } + + /* + * Corner case handling: + * 1. When a new swap-cache page is read into, it is added to the LRU + * and treated as swapcache but it has no rmap yet. + * Calling try_to_unmap() against a page->mapping==NULL page will + * trigger a BUG. So handle it here. + * 2. An orphaned page (see truncate_complete_page) might have + * fs-private metadata. The page can be picked up due to memory + * offlining. Everywhere else except page reclaim, the page is + * invisible to the vm, so the page can not be migrated. So try to + * free the metadata, so the page can be freed. + */ + if (!page->mapping) { + VM_BUG_ON_PAGE(PageAnon(page), page); + if (page_has_private(page)) { + try_to_free_buffers(page); + goto out_unlock_both; + } + } else if (page_mapped(page)) { + /* Establish migration ptes */ + VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma, + page); + try_to_unmap(page, TTU_MIGRATION|TTU_IGNORE_MLOCK); + page_was_mapped = 1; + } + + if (!page_mapped(page)) + rc = move_to_new_page(newpage, page, mode); + + if (page_was_mapped) + remove_migration_ptes(page, + rc == MIGRATEPAGE_SUCCESS ? newpage : page, false); + +out_unlock_both: + unlock_page(newpage); +out_unlock: + /* Drop an anon_vma reference if we took one */ + if (anon_vma) + put_anon_vma(anon_vma); + unlock_page(page); +out: + /* + * If migration is successful, decrease refcount of the newpage + * which will not free the page because new page owner increased + * refcounter. As well, if it is LRU page, add the page to LRU + * list in here. 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; +} + +/* + * 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) +{ + int rc = MIGRATEPAGE_SUCCESS; + struct page *newpage = NULL; + + if (!thp_migration_supported() && PageTransHuge(page)) + return -ENOMEM; + + if (page_count(page) == 1) { + /* page was freed from under us. So we are done. */ + ClearPageActive(page); + ClearPageUnevictable(page); + if (unlikely(__PageMovable(page))) { + lock_page(page); + if (!PageMovable(page)) + __ClearPageIsolated(page); + unlock_page(page); + } + 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); + + /* + * 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 migration is successful, releases reference grabbed during + * isolation. Otherwise, restore the page to right list unless + * we want to retry. + */ + if (rc == MIGRATEPAGE_SUCCESS) { + if (reason != MR_MEMORY_FAILURE) + /* + * We release the page in page_handle_poison. + */ + put_page(page); + } else { + if (rc != -EAGAIN) { + if (likely(!__PageMovable(page))) { + putback_lru_page(page); + goto put_new; + } + + lock_page(page); + if (PageMovable(page)) + putback_movable_page(page); + else + __ClearPageIsolated(page); + unlock_page(page); + put_page(page); + } +put_new: + if (put_new_page) + put_new_page(newpage, private); + else + put_page(newpage); + } + + return rc; +} + +/* + * Counterpart of unmap_and_move_page() for hugepage migration. + * + * This function doesn't wait the completion of hugepage I/O + * because there is no race between I/O and migration for hugepage. + * Note that currently hugepage I/O occurs only in direct I/O + * where no lock is held and PG_writeback is irrelevant, + * and writeback status of all subpages are counted in the reference + * count of the head page (i.e. if all subpages of a 2MB hugepage are + * under direct I/O, the reference of the head page is 512 and a bit more.) + * This means that when we try to migrate hugepage whose subpages are + * doing direct I/O, some references remain after try_to_unmap() and + * hugepage migration fails without data corruption. + * + * There is also no race when direct I/O is issued on the page under migration, + * because then pte is replaced with migration swap entry and direct I/O code + * will wait in the page fault for migration to complete. + */ +static int unmap_and_move_huge_page(new_page_t get_new_page, + free_page_t put_new_page, unsigned long private, + struct page *hpage, int force, + enum migrate_mode mode, int reason) +{ + int rc = -EAGAIN; + int 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))) { + putback_active_hugepage(hpage); + return -ENOSYS; + } + + 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 (page_private(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 = TTU_MIGRATION|TTU_IGNORE_MLOCK; + + 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_unmap(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 != -EAGAIN) + putback_active_hugepage(hpage); + + /* + * 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; +} + +/* + * migrate_pages - migrate the pages specified in a list, to the free pages + * supplied as the target for the page migration + * + * @from: The list of pages to be migrated. + * @get_new_page: The function used to allocate free pages to be used + * as the target of the page migration. + * @put_new_page: The function used to free target pages if migration + * fails, or NULL if no special handling is necessary. + * @private: Private data to be passed on to get_new_page() + * @mode: The migration mode that specifies the constraints for + * page migration, if any. + * @reason: The reason for page migration. + * + * The function returns after 10 attempts or if no pages are movable any more + * because the list has become empty or no retryable pages exist any more. + * The caller should call putback_movable_pages() to return pages to the LRU + * or free list only if ret != 0. + * + * Returns the number of pages that were not migrated, or an error code. + */ +int migrate_pages(struct list_head *from, new_page_t get_new_page, + free_page_t put_new_page, unsigned long private, + enum migrate_mode mode, int reason) +{ + int retry = 1; + int 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; + + 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); + else + rc = unmap_and_move(get_new_page, put_new_page, + private, page, pass > 2, mode, + reason); + + switch(rc) { + case -ENOMEM: + /* + * 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. + */ + if (is_thp) { + lock_page(page); + rc = split_huge_page_to_list(page, from); + unlock_page(page); + if (!rc) { + list_safe_reset_next(page, page2, lru); + 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, -ENOSYS, 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: + 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; + + 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_nodemask(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); + 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)) { + err = isolate_hugetlb(page, pagelist); + if (!err) + 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 incude 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; + + migrate_prep(); + + 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: + 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 = find_vma(mm, addr); + if (!vma || addr < vma->vm_start) + goto set_status; + + /* FOLL_DUMP to ignore special (like zero) pages */ + page = follow_page(vma, addr, FOLL_DUMP); + + err = PTR_ERR(page); + if (IS_ERR(page)) + goto set_status; + + err = page ? page_to_nid(page) : -ENOENT; +set_status: + *status = err; + + pages++; + status++; + } + + mmap_read_unlock(mm); +} + +/* + * Determine the nodes of a user array of pages and store it in + * a user array of status. + */ +static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages, + const void __user * __user *pages, + int __user *status) +{ +#define DO_PAGES_STAT_CHUNK_NR 16 + const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR]; + int chunk_status[DO_PAGES_STAT_CHUNK_NR]; + + while (nr_pages) { + unsigned long chunk_nr; + + chunk_nr = nr_pages; + if (chunk_nr > DO_PAGES_STAT_CHUNK_NR) + chunk_nr = DO_PAGES_STAT_CHUNK_NR; + + if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages))) + break; + + do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status); + + if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status))) + break; + + pages += chunk_nr; + status += chunk_nr; + nr_pages -= chunk_nr; + } + return nr_pages ? -EFAULT : 0; +} + +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_COMPAT +COMPAT_SYSCALL_DEFINE6(move_pages, pid_t, pid, compat_ulong_t, nr_pages, + compat_uptr_t __user *, pages32, + const int __user *, nodes, + int __user *, status, + int, flags) +{ + const void __user * __user *pages; + int i; + + pages = compat_alloc_user_space(nr_pages * sizeof(void *)); + for (i = 0; i < nr_pages; i++) { + compat_uptr_t p; + + if (get_user(p, pages32 + i) || + put_user(compat_ptr(p), pages + i)) + return -EFAULT; + } + return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags); +} +#endif /* CONFIG_COMPAT */ + +#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 int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page) +{ + int page_lru; + + VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page); + + /* Avoid migrating to a node that is nearly full */ + if (!migrate_balanced_pgdat(pgdat, compound_nr(page))) + return 0; + + if (isolate_lru_page(page)) + return 0; + + /* + * migrate_misplaced_transhuge_page() skips page migration's usual + * check on page_count(), so we must do it here, now that the page + * has been isolated: a GUP pin, or any other pin, prevents migration. + * The expected page count is 3: 1 for page's mapcount and 1 for the + * caller's pin and 1 for the reference taken by isolate_lru_page(). + */ + if (PageTransHuge(page) && page_count(page) != 3) { + putback_lru_page(page); + return 0; + } + + page_lru = page_is_file_lru(page); + mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_lru, + thp_nr_pages(page)); + + /* + * Isolating the page has taken another reference, so the + * caller's reference can be safely dropped without the page + * disappearing underneath us during migration. + */ + put_page(page); + return 1; +} + +bool pmd_trans_migrating(pmd_t pmd) +{ + struct page *page = pmd_page(pmd); + return PageLocked(page); +} + +/* + * Attempt to migrate a misplaced page to the specified destination + * node. Caller is expected to have an elevated reference count on + * the page that will be dropped by this function before returning. + */ +int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma, + int node) +{ + pg_data_t *pgdat = NODE_DATA(node); + int isolated; + int nr_remaining; + LIST_HEAD(migratepages); + + /* + * Don't migrate file pages that are mapped in multiple processes + * with execute permissions as they are probably shared libraries. + */ + if (page_mapcount(page) != 1 && page_is_file_lru(page) && + (vma->vm_flags & VM_EXEC)) + goto out; + + /* + * Also do not migrate dirty pages as not all filesystems can move + * dirty pages in MIGRATE_ASYNC mode which is a waste of cycles. + */ + if (page_is_file_lru(page) && PageDirty(page)) + goto out; + + isolated = numamigrate_isolate_page(pgdat, page); + if (!isolated) + goto out; + + list_add(&page->lru, &migratepages); + nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page, + NULL, node, MIGRATE_ASYNC, + MR_NUMA_MISPLACED); + if (nr_remaining) { + if (!list_empty(&migratepages)) { + list_del(&page->lru); + dec_node_page_state(page, NR_ISOLATED_ANON + + page_is_file_lru(page)); + putback_lru_page(page); + } + isolated = 0; + } else + count_vm_numa_event(NUMA_PAGE_MIGRATE); + BUG_ON(!list_empty(&migratepages)); + return isolated; + +out: + put_page(page); + return 0; +} +#endif /* CONFIG_NUMA_BALANCING */ + +#if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE) +/* + * Migrates a THP to a given target node. page must be locked and is unlocked + * before returning. + */ +int migrate_misplaced_transhuge_page(struct mm_struct *mm, + struct vm_area_struct *vma, + pmd_t *pmd, pmd_t entry, + unsigned long address, + struct page *page, int node) +{ + spinlock_t *ptl; + pg_data_t *pgdat = NODE_DATA(node); + int isolated = 0; + struct page *new_page = NULL; + int page_lru = page_is_file_lru(page); + unsigned long start = address & HPAGE_PMD_MASK; + + new_page = alloc_pages_node(node, + (GFP_TRANSHUGE_LIGHT | __GFP_THISNODE), + HPAGE_PMD_ORDER); + if (!new_page) + goto out_fail; + prep_transhuge_page(new_page); + + isolated = numamigrate_isolate_page(pgdat, page); + if (!isolated) { + put_page(new_page); + goto out_fail; + } + + /* Prepare a page as a migration target */ + __SetPageLocked(new_page); + if (PageSwapBacked(page)) + __SetPageSwapBacked(new_page); + + /* anon mapping, we can simply copy page->mapping to the new page: */ + new_page->mapping = page->mapping; + new_page->index = page->index; + /* flush the cache before copying using the kernel virtual address */ + flush_cache_range(vma, start, start + HPAGE_PMD_SIZE); + migrate_page_copy(new_page, page); + WARN_ON(PageLRU(new_page)); + + /* Recheck the target PMD */ + ptl = pmd_lock(mm, pmd); + if (unlikely(!pmd_same(*pmd, entry) || !page_ref_freeze(page, 2))) { + spin_unlock(ptl); + + /* Reverse changes made by migrate_page_copy() */ + if (TestClearPageActive(new_page)) + SetPageActive(page); + if (TestClearPageUnevictable(new_page)) + SetPageUnevictable(page); + + unlock_page(new_page); + put_page(new_page); /* Free it */ + + /* Retake the callers reference and putback on LRU */ + get_page(page); + putback_lru_page(page); + mod_node_page_state(page_pgdat(page), + NR_ISOLATED_ANON + page_lru, -HPAGE_PMD_NR); + + goto out_unlock; + } + + entry = mk_huge_pmd(new_page, vma->vm_page_prot); + entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); + + /* + * Overwrite the old entry under pagetable lock and establish + * the new PTE. Any parallel GUP will either observe the old + * page blocking on the page lock, block on the page table + * lock or observe the new page. The SetPageUptodate on the + * new page and page_add_new_anon_rmap guarantee the copy is + * visible before the pagetable update. + */ + page_add_anon_rmap(new_page, vma, start, true); + /* + * At this point the pmd is numa/protnone (i.e. non present) and the TLB + * has already been flushed globally. So no TLB can be currently + * caching this non present pmd mapping. There's no need to clear the + * pmd before doing set_pmd_at(), nor to flush the TLB after + * set_pmd_at(). Clearing the pmd here would introduce a race + * condition against MADV_DONTNEED, because MADV_DONTNEED only holds the + * mmap_lock for reading. If the pmd is set to NULL at any given time, + * MADV_DONTNEED won't wait on the pmd lock and it'll skip clearing this + * pmd. + */ + set_pmd_at(mm, start, pmd, entry); + update_mmu_cache_pmd(vma, address, &entry); + + page_ref_unfreeze(page, 2); + mlock_migrate_page(new_page, page); + page_remove_rmap(page, true); + set_page_owner_migrate_reason(new_page, MR_NUMA_MISPLACED); + + spin_unlock(ptl); + + /* Take an "isolate" reference and put new page on the LRU. */ + get_page(new_page); + putback_lru_page(new_page); + + unlock_page(new_page); + unlock_page(page); + put_page(page); /* Drop the rmap reference */ + put_page(page); /* Drop the LRU isolation reference */ + + count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR); + count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR); + + mod_node_page_state(page_pgdat(page), + NR_ISOLATED_ANON + page_lru, + -HPAGE_PMD_NR); + return isolated; + +out_fail: + count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR); + ptl = pmd_lock(mm, pmd); + if (pmd_same(*pmd, entry)) { + entry = pmd_modify(entry, vma->vm_page_prot); + set_pmd_at(mm, start, pmd, entry); + update_mmu_cache_pmd(vma, address, &entry); + } + spin_unlock(ptl); + +out_unlock: + unlock_page(page); + put_page(page); + return 0; +} +#endif /* CONFIG_NUMA_BALANCING */ + +#endif /* CONFIG_NUMA */ + +#ifdef CONFIG_DEVICE_PRIVATE +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)) { + for (addr = start; addr < end; addr += PAGE_SIZE) { + migrate->src[migrate->npages] = 0; + migrate->dst[migrate->npages] = 0; + migrate->npages++; + } + return 0; + } + + 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_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_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 = device_private_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_write_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 */ + entry = make_migration_entry(page, mpfn & + MIGRATE_PFN_WRITE); + 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; + } + + /* Only flush the TLB if we actually modified any entries */ + if (unmapped) + flush_tlb_range(walk->vma, start, end); + + arch_leave_lazy_mmu_mode(); + pte_unmap_unlock(ptep - 1, ptl); + + 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_migrate(&range, 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 + * migrate_page_move_mapping(), except that here we allow migration of a + * ZONE_DEVICE page. + */ +static bool migrate_vma_check_page(struct page *page) +{ + /* + * One extra ref because caller holds an extra reference, either from + * isolate_lru_page() for a regular page, or migrate_vma_collect() for + * a device page. + */ + int extra = 1; + + /* + * FIXME support THP (transparent huge page), it is bit more complex to + * check them than regular pages, because they can be mapped with a pmd + * or with a pte (split pte mapping). + */ + if (PageCompound(page)) + return false; + + /* Page from ZONE_DEVICE have one extra reference */ + if (is_zone_device_page(page)) { + /* + * Private page can never be pin as they have no valid pte and + * GUP will fail for those. Yet if there is a pending migration + * a thread might try to wait on the pte migration entry and + * will bump the page reference count. Sadly there is no way to + * differentiate a regular pin from migration wait. Hence to + * avoid 2 racing thread trying to migrate back to CPU to enter + * infinite loop (one stoping migration because the other is + * waiting on pte migration entry). We always return true here. + * + * FIXME proper solution is to rework migration_entry_wait() so + * it does not need to take a reference on page. + */ + 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) +{ + int flags = TTU_MIGRATION | TTU_IGNORE_MLOCK; + const unsigned long npages = migrate->npages; + const unsigned long start = migrate->start; + unsigned long addr, i, restore = 0; + + for (i = 0; i < npages; i++) { + struct page *page = migrate_pfn_to_page(migrate->src[i]); + + if (!page || !(migrate->src[i] & MIGRATE_PFN_MIGRATE)) + continue; + + if (page_mapped(page)) { + try_to_unmap(page, flags); + if (page_mapped(page)) + goto restore; + } + + if (migrate_vma_check_page(page)) + continue; + +restore: + migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; + migrate->cpages--; + restore++; + } + + for (addr = start, i = 0; i < npages && restore; addr += PAGE_SIZE, i++) { + struct page *page = migrate_pfn_to_page(migrate->src[i]); + + if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE)) + continue; + + remove_migration_ptes(page, page, false); + + migrate->src[i] = 0; + unlock_page(page); + restore--; + + if (is_zone_device_page(page)) + put_page(page); + else + putback_lru_page(page); + } +} + +/** + * 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 unback virtual + * address. 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 fails and thus inside the device driver 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, + unsigned long *dst) +{ + 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, 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; + + swp_entry = make_device_private_entry(page, vma->vm_flags & VM_WRITE); + 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(&range, + MMU_NOTIFY_CLEAR, 0, + NULL, + migrate->vma->vm_mm, + addr, migrate->end); + mmu_notifier_invalidate_range_start(&range); + } + migrate_vma_insert_page(migrate, addr, newpage, + &migrate->src[i], + &migrate->dst[i]); + continue; + } + + mapping = page_mapping(page); + + if (is_zone_device_page(newpage)) { + if (is_device_private_page(newpage)) { + /* + * For now only support private anonymous when + * migrating to un-addressable device memory. + */ + if (mapping) { + migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; + continue; + } + } else { + /* + * 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 */ |