migrate.c 89.0 KB
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// SPDX-License-Identifier: GPL-2.0
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/*
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 * Memory Migration functionality - linux/mm/migrate.c
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 *
 * 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>
C
Christoph Lameter 已提交
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 * Christoph Lameter
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 */

#include <linux/migrate.h>
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#include <linux/export.h>
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#include <linux/swap.h>
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#include <linux/swapops.h>
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#include <linux/pagemap.h>
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#include <linux/buffer_head.h>
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#include <linux/mm_inline.h>
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#include <linux/nsproxy.h>
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#include <linux/pagevec.h>
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#include <linux/ksm.h>
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#include <linux/rmap.h>
#include <linux/topology.h>
#include <linux/cpu.h>
#include <linux/cpuset.h>
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#include <linux/writeback.h>
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#include <linux/mempolicy.h>
#include <linux/vmalloc.h>
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#include <linux/security.h>
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#include <linux/backing-dev.h>
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#include <linux/compaction.h>
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#include <linux/syscalls.h>
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#include <linux/compat.h>
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#include <linux/hugetlb.h>
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#include <linux/hugetlb_cgroup.h>
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#include <linux/gfp.h>
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#include <linux/pagewalk.h>
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#include <linux/pfn_t.h>
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#include <linux/memremap.h>
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#include <linux/userfaultfd_k.h>
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#include <linux/balloon_compaction.h>
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#include <linux/mmu_notifier.h>
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#include <linux/page_idle.h>
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#include <linux/page_owner.h>
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#include <linux/sched/mm.h>
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#include <linux/ptrace.h>
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#include <linux/oom.h>
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#include <linux/memory.h>
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#include <linux/random.h>
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55 56
#include <asm/tlbflush.h>

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#define CREATE_TRACE_POINTS
#include <trace/events/migrate.h>

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#include "internal.h"

62
int isolate_movable_page(struct page *page, isolate_mode_t mode)
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{
	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
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	 * so unconditionally grabbing the lock ruins page's owner side.
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	 */
	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);

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	return 0;
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out_no_isolated:
	unlock_page(page);
out_putpage:
	put_page(page);
out:
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	return -EBUSY;
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}

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static void putback_movable_page(struct page *page)
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{
	struct address_space *mapping;

	mapping = page_mapping(page);
	mapping->a_ops->putback_page(page);
	__ClearPageIsolated(page);
}

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/*
 * Put previously isolated pages back onto the appropriate lists
 * from where they were once taken off for compaction/migration.
 *
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 * 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().
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 */
void putback_movable_pages(struct list_head *l)
{
	struct page *page;
	struct page *page2;

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	list_for_each_entry_safe(page, page2, l, lru) {
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		if (unlikely(PageHuge(page))) {
			putback_active_hugepage(page);
			continue;
		}
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		list_del(&page->lru);
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		/*
		 * We isolated non-lru movable page so here we can use
		 * __PageMovable because LRU page's mapping cannot have
		 * PAGE_MAPPING_MOVABLE.
		 */
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		if (unlikely(__PageMovable(page))) {
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			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 {
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			mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
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					page_is_file_lru(page), -thp_nr_pages(page));
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			putback_lru_page(page);
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		}
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	}
}

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/*
 * Restore a potential migration pte to a working pte entry
 */
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static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma,
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				 unsigned long addr, void *old)
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{
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	struct page_vma_mapped_walk pvmw = {
		.page = old,
		.vma = vma,
		.address = addr,
		.flags = PVMW_SYNC | PVMW_MIGRATION,
	};
	struct page *new;
	pte_t pte;
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	swp_entry_t entry;

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	VM_BUG_ON_PAGE(PageTail(page), page);
	while (page_vma_mapped_walk(&pvmw)) {
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		if (PageKsm(page))
			new = page;
		else
			new = page - pvmw.page->index +
				linear_page_index(vma, pvmw.address);
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#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

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		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);
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		/*
		 * Recheck VMA as permissions can change since migration started
		 */
		entry = pte_to_swp_entry(*pvmw.pte);
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		if (is_writable_migration_entry(entry))
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			pte = maybe_mkwrite(pte, vma);
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		else if (pte_swp_uffd_wp(*pvmw.pte))
			pte = pte_mkuffd_wp(pte);
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220
		if (unlikely(is_device_private_page(new))) {
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			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));
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			pte = swp_entry_to_pte(entry);
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			if (pte_swp_soft_dirty(*pvmw.pte))
				pte = pte_swp_mksoft_dirty(pte);
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			if (pte_swp_uffd_wp(*pvmw.pte))
				pte = pte_swp_mkuffd_wp(pte);
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		}
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#ifdef CONFIG_HUGETLB_PAGE
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		if (PageHuge(new)) {
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			unsigned int shift = huge_page_shift(hstate_vma(vma));

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			pte = pte_mkhuge(pte);
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			pte = arch_make_huge_pte(pte, shift, vma->vm_flags);
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			if (PageAnon(new))
				hugepage_add_anon_rmap(new, vma, pvmw.address);
			else
				page_dup_rmap(new, true);
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			set_huge_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
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		} else
#endif
		{
			if (PageAnon(new))
				page_add_anon_rmap(new, vma, pvmw.address, false);
			else
				page_add_file_rmap(new, false);
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			set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
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		}
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		if (vma->vm_flags & VM_LOCKED && !PageTransCompound(new))
			mlock_vma_page(new);

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		if (PageTransHuge(page) && PageMlocked(page))
			clear_page_mlock(page);

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		/* No need to invalidate - it was non-present before */
		update_mmu_cache(vma, pvmw.address, pvmw.pte);
	}
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	return true;
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}

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/*
 * Get rid of all migration entries and replace them by
 * references to the indicated page.
 */
271
void remove_migration_ptes(struct page *old, struct page *new, bool locked)
272
{
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	struct rmap_walk_control rwc = {
		.rmap_one = remove_migration_pte,
		.arg = old,
	};

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	if (locked)
		rmap_walk_locked(new, &rwc);
	else
		rmap_walk(new, &rwc);
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}

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/*
 * 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.
 */
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void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
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				spinlock_t *ptl)
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{
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	pte_t pte;
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	swp_entry_t entry;
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	struct folio *folio;
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296
	spin_lock(ptl);
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	pte = *ptep;
	if (!is_swap_pte(pte))
		goto out;

	entry = pte_to_swp_entry(pte);
	if (!is_migration_entry(entry))
		goto out;

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	folio = page_folio(pfn_swap_entry_to_page(entry));
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	/*
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	 * Once page cache replacement of page migration started, page_count
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	 * is zero; but we must not call folio_put_wait_locked() without
	 * a ref. Use folio_try_get(), and just fault again if it fails.
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	 */
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	if (!folio_try_get(folio))
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		goto out;
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	pte_unmap_unlock(ptep, ptl);
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	folio_put_wait_locked(folio, TASK_UNINTERRUPTIBLE);
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	return;
out:
	pte_unmap_unlock(ptep, ptl);
}

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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);
}

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void migration_entry_wait_huge(struct vm_area_struct *vma,
		struct mm_struct *mm, pte_t *pte)
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{
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	spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte);
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	__migration_entry_wait(mm, pte, ptl);
}

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#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
{
	spinlock_t *ptl;
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	struct folio *folio;
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	ptl = pmd_lock(mm, pmd);
	if (!is_pmd_migration_entry(*pmd))
		goto unlock;
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	folio = page_folio(pfn_swap_entry_to_page(pmd_to_swp_entry(*pmd)));
	if (!folio_try_get(folio))
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		goto unlock;
	spin_unlock(ptl);
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	folio_put_wait_locked(folio, TASK_UNINTERRUPTIBLE);
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	return;
unlock:
	spin_unlock(ptl);
}
#endif

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static int expected_page_refs(struct address_space *mapping, struct page *page)
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{
	int expected_count = 1;

	/*
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	 * Device private pages have an extra refcount as they are
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	 * ZONE_DEVICE pages.
	 */
	expected_count += is_device_private_page(page);
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	if (mapping)
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		expected_count += compound_nr(page) + page_has_private(page);
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	return expected_count;
}

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/*
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 * Replace the page in the mapping.
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 *
 * The number of remaining references must be:
 * 1 for anonymous pages without a mapping
 * 2 for pages with a mapping
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 * 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
378
 */
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int folio_migrate_mapping(struct address_space *mapping,
		struct folio *newfolio, struct folio *folio, int extra_count)
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{
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	XA_STATE(xas, &mapping->i_pages, folio_index(folio));
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	struct zone *oldzone, *newzone;
	int dirty;
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	int expected_count = expected_page_refs(mapping, &folio->page) + extra_count;
	long nr = folio_nr_pages(folio);
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388
	if (!mapping) {
389
		/* Anonymous page without mapping */
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		if (folio_ref_count(folio) != expected_count)
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			return -EAGAIN;
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		/* No turning back from here */
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		newfolio->index = folio->index;
		newfolio->mapping = folio->mapping;
		if (folio_test_swapbacked(folio))
			__folio_set_swapbacked(newfolio);
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399
		return MIGRATEPAGE_SUCCESS;
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	}

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	oldzone = folio_zone(folio);
	newzone = folio_zone(newfolio);
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405
	xas_lock_irq(&xas);
406
	if (!folio_ref_freeze(folio, expected_count)) {
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		xas_unlock_irq(&xas);
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		return -EAGAIN;
	}

411
	/*
412
	 * Now we know that no one else is looking at the folio:
413
	 * no turning back from here.
414
	 */
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	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);
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		}
	} else {
425
		VM_BUG_ON_FOLIO(folio_test_swapcache(folio), folio);
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	}

428
	/* Move dirty while page refs frozen and newpage not yet exposed */
429
	dirty = folio_test_dirty(folio);
430
	if (dirty) {
431 432
		folio_clear_dirty(folio);
		folio_set_dirty(newfolio);
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	}

435
	xas_store(&xas, newfolio);
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	/*
438 439
	 * Drop cache reference from old page by unfreezing
	 * to one less reference.
440 441
	 * We know this isn't the last reference.
	 */
442
	folio_ref_unfreeze(folio, expected_count - nr);
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444
	xas_unlock(&xas);
445 446
	/* Leave irq disabled to prevent preemption while updating stats */

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	/*
	 * 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
454
	 * via NR_FILE_PAGES and NR_ANON_MAPPED if they
455 456
	 * are mapped to swap space.
	 */
457
	if (newzone != oldzone) {
458 459 460
		struct lruvec *old_lruvec, *new_lruvec;
		struct mem_cgroup *memcg;

461
		memcg = folio_memcg(folio);
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		old_lruvec = mem_cgroup_lruvec(memcg, oldzone->zone_pgdat);
		new_lruvec = mem_cgroup_lruvec(memcg, newzone->zone_pgdat);

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		__mod_lruvec_state(old_lruvec, NR_FILE_PAGES, -nr);
		__mod_lruvec_state(new_lruvec, NR_FILE_PAGES, nr);
467
		if (folio_test_swapbacked(folio) && !folio_test_swapcache(folio)) {
468 469
			__mod_lruvec_state(old_lruvec, NR_SHMEM, -nr);
			__mod_lruvec_state(new_lruvec, NR_SHMEM, nr);
470
		}
471
#ifdef CONFIG_SWAP
472
		if (folio_test_swapcache(folio)) {
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			__mod_lruvec_state(old_lruvec, NR_SWAPCACHE, -nr);
			__mod_lruvec_state(new_lruvec, NR_SWAPCACHE, nr);
		}
#endif
477
		if (dirty && mapping_can_writeback(mapping)) {
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			__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);
482
		}
483
	}
484
	local_irq_enable();
485

486
	return MIGRATEPAGE_SUCCESS;
487
}
488
EXPORT_SYMBOL(folio_migrate_mapping);
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490 491
/*
 * The expected number of remaining references is the same as that
492
 * of folio_migrate_mapping().
493 494 495 496
 */
int migrate_huge_page_move_mapping(struct address_space *mapping,
				   struct page *newpage, struct page *page)
{
497
	XA_STATE(xas, &mapping->i_pages, page_index(page));
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	int expected_count;

500
	xas_lock_irq(&xas);
501
	expected_count = 2 + page_has_private(page);
502 503
	if (page_count(page) != expected_count || xas_load(&xas) != page) {
		xas_unlock_irq(&xas);
504 505 506
		return -EAGAIN;
	}

507
	if (!page_ref_freeze(page, expected_count)) {
508
		xas_unlock_irq(&xas);
509 510 511
		return -EAGAIN;
	}

512 513
	newpage->index = page->index;
	newpage->mapping = page->mapping;
514

515 516
	get_page(newpage);

517
	xas_store(&xas, newpage);
518

519
	page_ref_unfreeze(page, expected_count - 1);
520

521
	xas_unlock_irq(&xas);
522

523
	return MIGRATEPAGE_SUCCESS;
524 525
}

526
/*
527
 * Copy the flags and some other ancillary information
528
 */
529
void folio_migrate_flags(struct folio *newfolio, struct folio *folio)
530
{
531 532
	int cpupid;

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	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);
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551
	/* Move dirty on pages not done by folio_migrate_mapping() */
552 553
	if (folio_test_dirty(folio))
		folio_set_dirty(newfolio);
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	if (folio_test_young(folio))
		folio_set_young(newfolio);
	if (folio_test_idle(folio))
		folio_set_idle(newfolio);
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	/*
	 * Copy NUMA information to the new page, to prevent over-eager
	 * future migrations of this same page.
	 */
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	cpupid = page_cpupid_xchg_last(&folio->page, -1);
	page_cpupid_xchg_last(&newfolio->page, cpupid);
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567
	folio_migrate_ksm(newfolio, folio);
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	/*
	 * Please do not reorder this without considering how mm/ksm.c's
	 * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
	 */
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	if (folio_test_swapcache(folio))
		folio_clear_swapcache(folio);
	folio_clear_private(folio);
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	/* page->private contains hugetlb specific flags */
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	if (!folio_test_hugetlb(folio))
		folio->private = NULL;
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	/*
	 * If any waiters have accumulated on the new page then
	 * wake them up.
	 */
584 585
	if (folio_test_writeback(newfolio))
		folio_end_writeback(newfolio);
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	/*
	 * 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.
	 */
592 593
	if (folio_test_readahead(folio))
		folio_set_readahead(newfolio);
594

595
	folio_copy_owner(newfolio, folio);
596

597
	if (!folio_test_hugetlb(folio))
598
		mem_cgroup_migrate(folio, newfolio);
599
}
600
EXPORT_SYMBOL(folio_migrate_flags);
601

602
void folio_migrate_copy(struct folio *newfolio, struct folio *folio)
603
{
604 605
	folio_copy(newfolio, folio);
	folio_migrate_flags(newfolio, folio);
606
}
607
EXPORT_SYMBOL(folio_migrate_copy);
608

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/************************************************************
 *                    Migration functions
 ***********************************************************/

613
/*
614
 * Common logic to directly migrate a single LRU page suitable for
615
 * pages that do not use PagePrivate/PagePrivate2.
616 617 618
 *
 * Pages are locked upon entry and exit.
 */
619
int migrate_page(struct address_space *mapping,
620 621
		struct page *newpage, struct page *page,
		enum migrate_mode mode)
622
{
623 624
	struct folio *newfolio = page_folio(newpage);
	struct folio *folio = page_folio(page);
625 626
	int rc;

627
	BUG_ON(folio_test_writeback(folio));	/* Writeback must be complete */
628

629
	rc = folio_migrate_mapping(mapping, newfolio, folio, 0);
630

631
	if (rc != MIGRATEPAGE_SUCCESS)
632 633
		return rc;

634
	if (mode != MIGRATE_SYNC_NO_COPY)
635
		folio_migrate_copy(newfolio, folio);
636
	else
637
		folio_migrate_flags(newfolio, folio);
638
	return MIGRATEPAGE_SUCCESS;
639 640 641
}
EXPORT_SYMBOL(migrate_page);

642
#ifdef CONFIG_BLOCK
643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680
/* 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;
}

681 682 683
static int __buffer_migrate_page(struct address_space *mapping,
		struct page *newpage, struct page *page, enum migrate_mode mode,
		bool check_refs)
684 685 686
{
	struct buffer_head *bh, *head;
	int rc;
687
	int expected_count;
688 689

	if (!page_has_buffers(page))
690
		return migrate_page(mapping, newpage, page, mode);
691

692
	/* Check whether page does not have extra refs before we do more work */
693
	expected_count = expected_page_refs(mapping, page);
694 695
	if (page_count(page) != expected_count)
		return -EAGAIN;
696

697 698 699
	head = page_buffers(page);
	if (!buffer_migrate_lock_buffers(head, mode))
		return -EAGAIN;
700

701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720
	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;
			}
721
			spin_unlock(&mapping->private_lock);
722 723 724 725 726 727
			invalidate_bh_lrus();
			invalidated = true;
			goto recheck_buffers;
		}
	}

728
	rc = migrate_page_move_mapping(mapping, newpage, page, 0);
729
	if (rc != MIGRATEPAGE_SUCCESS)
730
		goto unlock_buffers;
731

732
	attach_page_private(newpage, detach_page_private(page));
733 734 735 736 737 738 739 740

	bh = head;
	do {
		set_bh_page(bh, newpage, bh_offset(bh));
		bh = bh->b_this_page;

	} while (bh != head);

741 742 743 744
	if (mode != MIGRATE_SYNC_NO_COPY)
		migrate_page_copy(newpage, page);
	else
		migrate_page_states(newpage, page);
745

746 747
	rc = MIGRATEPAGE_SUCCESS;
unlock_buffers:
748 749
	if (check_refs)
		spin_unlock(&mapping->private_lock);
750 751 752 753 754 755 756
	bh = head;
	do {
		unlock_buffer(bh);
		bh = bh->b_this_page;

	} while (bh != head);

757
	return rc;
758
}
759 760 761 762 763 764 765 766 767 768 769

/*
 * 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);
}
770
EXPORT_SYMBOL(buffer_migrate_page);
771 772 773 774 775 776 777 778 779 780 781 782

/*
 * 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);
}
783
#endif
784

785 786 787 788
/*
 * Writeback a page to clean the dirty state
 */
static int writeout(struct address_space *mapping, struct page *page)
789
{
790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806
	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;

807
	/*
808 809 810 811 812 813
	 * 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.
814
	 */
815
	remove_migration_ptes(page, page, false);
816

817
	rc = mapping->a_ops->writepage(page, &wbc);
818

819 820 821 822
	if (rc != AOP_WRITEPAGE_ACTIVATE)
		/* unlocked. Relock */
		lock_page(page);

823
	return (rc < 0) ? -EIO : -EAGAIN;
824 825 826 827 828 829
}

/*
 * Default handling if a filesystem does not provide a migration function.
 */
static int fallback_migrate_page(struct address_space *mapping,
830
	struct page *newpage, struct page *page, enum migrate_mode mode)
831
{
832
	if (PageDirty(page)) {
833
		/* Only writeback pages in full synchronous migration */
834 835 836 837 838
		switch (mode) {
		case MIGRATE_SYNC:
		case MIGRATE_SYNC_NO_COPY:
			break;
		default:
839
			return -EBUSY;
840
		}
841
		return writeout(mapping, page);
842
	}
843 844 845 846 847

	/*
	 * Buffers may be managed in a filesystem specific way.
	 * We must have no buffers or drop them.
	 */
848
	if (page_has_private(page) &&
849
	    !try_to_release_page(page, GFP_KERNEL))
850
		return mode == MIGRATE_SYNC ? -EAGAIN : -EBUSY;
851

852
	return migrate_page(mapping, newpage, page, mode);
853 854
}

855 856 857 858 859 860
/*
 * 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.
861 862 863
 *
 * Return value:
 *   < 0 - error code
864
 *  MIGRATEPAGE_SUCCESS - success
865
 */
866
static int move_to_new_page(struct page *newpage, struct page *page,
867
				enum migrate_mode mode)
868 869
{
	struct address_space *mapping;
870 871
	int rc = -EAGAIN;
	bool is_lru = !__PageMovable(page);
872

873 874
	VM_BUG_ON_PAGE(!PageLocked(page), page);
	VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
875 876

	mapping = page_mapping(page);
877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894

	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 {
895
		/*
896 897
		 * In case of non-lru page, it could be released after
		 * isolation step. In that case, we shouldn't try migration.
898
		 */
899 900 901 902 903 904 905 906 907 908 909 910
		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));
	}
911

912 913 914 915 916
	/*
	 * 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) {
917 918 919 920 921 922 923 924 925 926 927
		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);
		}

		/*
928
		 * Anonymous and movable page->mapping will be cleared by
929 930 931 932
		 * free_pages_prepare so don't reset it here for keeping
		 * the type to work PageAnon, for example.
		 */
		if (!PageMappingFlags(page))
933
			page->mapping = NULL;
934

935
		if (likely(!is_zone_device_page(newpage)))
936 937
			flush_dcache_page(newpage);

938
	}
939
out:
940 941 942
	return rc;
}

943
static int __unmap_and_move(struct page *page, struct page *newpage,
944
				int force, enum migrate_mode mode)
945
{
946
	int rc = -EAGAIN;
947
	bool page_was_mapped = false;
948
	struct anon_vma *anon_vma = NULL;
949
	bool is_lru = !__PageMovable(page);
950

N
Nick Piggin 已提交
951
	if (!trylock_page(page)) {
952
		if (!force || mode == MIGRATE_ASYNC)
953
			goto out;
954 955 956 957 958 959 960

		/*
		 * 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.
961
		 * mpage_readahead). If an allocation happens for the
962 963 964 965 966 967 968
		 * 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)
969
			goto out;
970

971 972 973 974
		lock_page(page);
	}

	if (PageWriteback(page)) {
975
		/*
976
		 * Only in the case of a full synchronous migration is it
977 978 979
		 * 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
980
		 */
981 982 983 984 985
		switch (mode) {
		case MIGRATE_SYNC:
		case MIGRATE_SYNC_NO_COPY:
			break;
		default:
986
			rc = -EBUSY;
987
			goto out_unlock;
988 989
		}
		if (!force)
990
			goto out_unlock;
991 992
		wait_on_page_writeback(page);
	}
993

994
	/*
995
	 * By try_to_migrate(), page->mapcount goes down to 0 here. In this case,
996
	 * we cannot notice that anon_vma is freed while we migrates a page.
997
	 * This get_anon_vma() delays freeing anon_vma pointer until the end
998
	 * of migration. File cache pages are no problem because of page_lock()
999 1000
	 * File Caches may use write_page() or lock_page() in migration, then,
	 * just care Anon page here.
1001 1002 1003 1004 1005 1006
	 *
	 * 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).
1007
	 */
1008
	if (PageAnon(page) && !PageKsm(page))
1009
		anon_vma = page_get_anon_vma(page);
1010

1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021
	/*
	 * 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;

1022 1023 1024 1025 1026
	if (unlikely(!is_lru)) {
		rc = move_to_new_page(newpage, page, mode);
		goto out_unlock_both;
	}

1027
	/*
1028 1029 1030 1031 1032
	 * 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.
1033
	 * 2. An orphaned page (see truncate_cleanup_page) might have
1034 1035 1036 1037
	 * 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.
1038
	 */
1039
	if (!page->mapping) {
1040
		VM_BUG_ON_PAGE(PageAnon(page), page);
1041
		if (page_has_private(page)) {
1042
			try_to_free_buffers(page);
1043
			goto out_unlock_both;
1044
		}
1045 1046
	} else if (page_mapped(page)) {
		/* Establish migration ptes */
1047 1048
		VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma,
				page);
1049
		try_to_migrate(page, 0);
1050
		page_was_mapped = true;
1051
	}
1052

1053
	if (!page_mapped(page))
1054
		rc = move_to_new_page(newpage, page, mode);
1055

1056 1057
	if (page_was_mapped)
		remove_migration_ptes(page,
1058
			rc == MIGRATEPAGE_SUCCESS ? newpage : page, false);
1059

1060 1061 1062
out_unlock_both:
	unlock_page(newpage);
out_unlock:
1063
	/* Drop an anon_vma reference if we took one */
1064
	if (anon_vma)
1065
		put_anon_vma(anon_vma);
1066
	unlock_page(page);
1067
out:
1068 1069 1070 1071
	/*
	 * 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
1072 1073 1074 1075
	 * 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.
1076 1077
	 */
	if (rc == MIGRATEPAGE_SUCCESS) {
1078
		if (unlikely(!is_lru))
1079 1080 1081 1082 1083
			put_page(newpage);
		else
			putback_lru_page(newpage);
	}

1084 1085
	return rc;
}
1086

1087 1088 1089 1090
/*
 * Obtain the lock on page, remove all ptes and migrate the page
 * to the newly allocated page in newpage.
 */
1091
static int unmap_and_move(new_page_t get_new_page,
1092 1093
				   free_page_t put_new_page,
				   unsigned long private, struct page *page,
1094
				   int force, enum migrate_mode mode,
1095 1096
				   enum migrate_reason reason,
				   struct list_head *ret)
1097
{
1098
	int rc = MIGRATEPAGE_SUCCESS;
1099
	struct page *newpage = NULL;
1100

1101
	if (!thp_migration_supported() && PageTransHuge(page))
1102
		return -ENOSYS;
1103

1104 1105
	if (page_count(page) == 1) {
		/* page was freed from under us. So we are done. */
1106 1107
		ClearPageActive(page);
		ClearPageUnevictable(page);
1108 1109 1110 1111 1112 1113
		if (unlikely(__PageMovable(page))) {
			lock_page(page);
			if (!PageMovable(page))
				__ClearPageIsolated(page);
			unlock_page(page);
		}
1114 1115 1116
		goto out;
	}

1117 1118 1119 1120
	newpage = get_new_page(page, private);
	if (!newpage)
		return -ENOMEM;

1121
	rc = __unmap_and_move(page, newpage, force, mode);
1122
	if (rc == MIGRATEPAGE_SUCCESS)
1123
		set_page_owner_migrate_reason(newpage, reason);
1124

1125
out:
1126
	if (rc != -EAGAIN) {
1127 1128 1129
		/*
		 * A page that has been migrated has all references
		 * removed and will be freed. A page that has not been
1130
		 * migrated will have kept its references and be restored.
1131 1132
		 */
		list_del(&page->lru);
1133
	}
1134

1135 1136 1137 1138 1139 1140
	/*
	 * 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) {
1141 1142 1143 1144 1145 1146
		/*
		 * Compaction can migrate also non-LRU pages which are
		 * not accounted to NR_ISOLATED_*. They can be recognized
		 * as __PageMovable
		 */
		if (likely(!__PageMovable(page)))
1147
			mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
1148
					page_is_file_lru(page), -thp_nr_pages(page));
1149

1150
		if (reason != MR_MEMORY_FAILURE)
1151
			/*
1152
			 * We release the page in page_handle_poison.
1153
			 */
1154
			put_page(page);
1155
	} else {
1156 1157
		if (rc != -EAGAIN)
			list_add_tail(&page->lru, ret);
1158

1159 1160 1161 1162
		if (put_new_page)
			put_new_page(newpage, private);
		else
			put_page(newpage);
1163
	}
1164

1165 1166 1167
	return rc;
}

1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186
/*
 * 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,
1187 1188
				free_page_t put_new_page, unsigned long private,
				struct page *hpage, int force,
1189 1190
				enum migrate_mode mode, int reason,
				struct list_head *ret)
1191
{
1192
	int rc = -EAGAIN;
1193
	int page_was_mapped = 0;
1194
	struct page *new_hpage;
1195
	struct anon_vma *anon_vma = NULL;
1196
	struct address_space *mapping = NULL;
1197

1198
	/*
1199
	 * Migratability of hugepages depends on architectures and their size.
1200 1201 1202 1203 1204
	 * 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.
	 */
1205
	if (!hugepage_migration_supported(page_hstate(hpage))) {
1206
		list_move_tail(&hpage->lru, ret);
1207
		return -ENOSYS;
1208
	}
1209

1210 1211 1212 1213 1214 1215
	if (page_count(hpage) == 1) {
		/* page was freed from under us. So we are done. */
		putback_active_hugepage(hpage);
		return MIGRATEPAGE_SUCCESS;
	}

1216
	new_hpage = get_new_page(hpage, private);
1217 1218 1219 1220
	if (!new_hpage)
		return -ENOMEM;

	if (!trylock_page(hpage)) {
1221
		if (!force)
1222
			goto out;
1223 1224 1225 1226 1227 1228 1229
		switch (mode) {
		case MIGRATE_SYNC:
		case MIGRATE_SYNC_NO_COPY:
			break;
		default:
			goto out;
		}
1230 1231 1232
		lock_page(hpage);
	}

1233 1234 1235 1236 1237
	/*
	 * 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.
	 */
1238
	if (hugetlb_page_subpool(hpage) && !page_mapping(hpage)) {
1239 1240 1241 1242
		rc = -EBUSY;
		goto out_unlock;
	}

1243 1244
	if (PageAnon(hpage))
		anon_vma = page_get_anon_vma(hpage);
1245

1246 1247 1248
	if (unlikely(!trylock_page(new_hpage)))
		goto put_anon;

1249
	if (page_mapped(hpage)) {
1250
		bool mapping_locked = false;
1251
		enum ttu_flags ttu = 0;
1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266

		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;
		}
1267

1268
		try_to_migrate(hpage, ttu);
1269
		page_was_mapped = 1;
1270 1271 1272

		if (mapping_locked)
			i_mmap_unlock_write(mapping);
1273
	}
1274 1275

	if (!page_mapped(hpage))
1276
		rc = move_to_new_page(new_hpage, hpage, mode);
1277

1278
	if (page_was_mapped)
1279
		remove_migration_ptes(hpage,
1280
			rc == MIGRATEPAGE_SUCCESS ? new_hpage : hpage, false);
1281

1282
unlock_put_anon:
1283 1284 1285
	unlock_page(new_hpage);

put_anon:
H
Hugh Dickins 已提交
1286
	if (anon_vma)
1287
		put_anon_vma(anon_vma);
1288

1289
	if (rc == MIGRATEPAGE_SUCCESS) {
1290
		move_hugetlb_state(hpage, new_hpage, reason);
1291 1292
		put_new_page = NULL;
	}
1293

1294
out_unlock:
1295
	unlock_page(hpage);
1296
out:
1297
	if (rc == MIGRATEPAGE_SUCCESS)
1298
		putback_active_hugepage(hpage);
1299
	else if (rc != -EAGAIN)
1300
		list_move_tail(&hpage->lru, ret);
1301 1302 1303 1304 1305 1306

	/*
	 * If migration was not successful and there's a freeing callback, use
	 * it.  Otherwise, put_page() will drop the reference grabbed during
	 * isolation.
	 */
1307
	if (put_new_page)
1308 1309
		put_new_page(new_hpage, private);
	else
1310
		putback_active_hugepage(new_hpage);
1311

1312 1313 1314
	return rc;
}

1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328
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;
}

1329
/*
1330 1331
 * migrate_pages - migrate the pages specified in a list, to the free pages
 *		   supplied as the target for the page migration
1332
 *
1333 1334 1335
 * @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.
1336 1337
 * @put_new_page:	The function used to free target pages if migration
 *			fails, or NULL if no special handling is necessary.
1338 1339 1340 1341
 * @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.
1342
 * @ret_succeeded:	Set to the number of normal pages migrated successfully if
1343
 *			the caller passes a non-NULL pointer.
1344
 *
1345 1346
 * 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.
1347 1348
 * It is caller's responsibility to call putback_movable_pages() to return pages
 * to the LRU or free list only if ret != 0.
1349
 *
1350 1351 1352
 * Returns the number of {normal page, THP, hugetlb} that were not migrated, or
 * an error code. The number of THP splits will be considered as the number of
 * non-migrated THP, no matter how many subpages of the THP are migrated successfully.
1353
 */
1354
int migrate_pages(struct list_head *from, new_page_t get_new_page,
1355
		free_page_t put_new_page, unsigned long private,
1356
		enum migrate_mode mode, int reason, unsigned int *ret_succeeded)
1357
{
1358
	int retry = 1;
1359
	int thp_retry = 1;
1360
	int nr_failed = 0;
1361
	int nr_failed_pages = 0;
1362
	int nr_succeeded = 0;
1363 1364 1365
	int nr_thp_succeeded = 0;
	int nr_thp_failed = 0;
	int nr_thp_split = 0;
1366
	int pass = 0;
1367
	bool is_thp = false;
1368 1369 1370
	struct page *page;
	struct page *page2;
	int swapwrite = current->flags & PF_SWAPWRITE;
1371
	int rc, nr_subpages;
1372
	LIST_HEAD(ret_pages);
1373
	LIST_HEAD(thp_split_pages);
1374
	bool nosplit = (reason == MR_NUMA_MISPLACED);
1375
	bool no_subpage_counting = false;
1376

1377 1378
	trace_mm_migrate_pages_start(mode, reason);

1379 1380 1381
	if (!swapwrite)
		current->flags |= PF_SWAPWRITE;

1382
thp_subpage_migration:
1383
	for (pass = 0; pass < 10 && (retry || thp_retry); pass++) {
1384
		retry = 0;
1385
		thp_retry = 0;
1386

1387
		list_for_each_entry_safe(page, page2, from, lru) {
1388
retry:
1389 1390 1391 1392 1393
			/*
			 * THP statistics is based on the source huge page.
			 * Capture required information that might get lost
			 * during migration.
			 */
1394
			is_thp = PageTransHuge(page) && !PageHuge(page);
1395
			nr_subpages = compound_nr(page);
1396
			cond_resched();
1397

1398 1399
			if (PageHuge(page))
				rc = unmap_and_move_huge_page(get_new_page,
1400
						put_new_page, private, page,
1401 1402
						pass > 2, mode, reason,
						&ret_pages);
1403
			else
1404
				rc = unmap_and_move(get_new_page, put_new_page,
1405
						private, page, pass > 2, mode,
1406 1407 1408 1409 1410 1411 1412 1413 1414 1415
						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
			 */
1416
			switch(rc) {
1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430
			/*
			 * 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) {
1431 1432
					nr_thp_failed++;
					if (!try_split_thp(page, &page2, &thp_split_pages)) {
1433 1434 1435 1436
						nr_thp_split++;
						goto retry;
					}

1437
					nr_failed_pages += nr_subpages;
1438 1439 1440 1441
					break;
				}

				/* Hugetlb migration is unsupported */
1442 1443
				if (!no_subpage_counting)
					nr_failed++;
1444
				nr_failed_pages += nr_subpages;
1445
				break;
1446
			case -ENOMEM:
1447
				/*
1448 1449
				 * When memory is low, don't bother to try to migrate
				 * other pages, just exit.
1450
				 * THP NUMA faulting doesn't split THP to retry.
1451
				 */
1452
				if (is_thp && !nosplit) {
1453 1454
					nr_thp_failed++;
					if (!try_split_thp(page, &page2, &thp_split_pages)) {
1455
						nr_thp_split++;
1456 1457
						goto retry;
					}
1458

1459
					nr_failed_pages += nr_subpages;
1460 1461
					goto out;
				}
1462 1463 1464

				if (!no_subpage_counting)
					nr_failed++;
1465
				nr_failed_pages += nr_subpages;
1466
				goto out;
1467
			case -EAGAIN:
1468 1469 1470 1471
				if (is_thp) {
					thp_retry++;
					break;
				}
1472
				retry++;
1473
				break;
1474
			case MIGRATEPAGE_SUCCESS:
1475
				nr_succeeded += nr_subpages;
1476 1477 1478 1479
				if (is_thp) {
					nr_thp_succeeded++;
					break;
				}
1480 1481
				break;
			default:
1482
				/*
1483
				 * Permanent failure (-EBUSY, etc.):
1484 1485 1486 1487
				 * unlike -EAGAIN case, the failed page is
				 * removed from migration page list and not
				 * retried in the next outer loop.
				 */
1488 1489
				if (is_thp) {
					nr_thp_failed++;
1490
					nr_failed_pages += nr_subpages;
1491 1492
					break;
				}
1493 1494 1495

				if (!no_subpage_counting)
					nr_failed++;
1496
				nr_failed_pages += nr_subpages;
1497
				break;
1498
			}
1499 1500
		}
	}
1501
	nr_failed += retry;
1502
	nr_thp_failed += thp_retry;
1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520
	/*
	 * Try to migrate subpages of fail-to-migrate THPs, no nr_failed
	 * counting in this round, since all subpages of a THP is counted
	 * as 1 failure in the first round.
	 */
	if (!list_empty(&thp_split_pages)) {
		/*
		 * Move non-migrated pages (after 10 retries) to ret_pages
		 * to avoid migrating them again.
		 */
		list_splice_init(from, &ret_pages);
		list_splice_init(&thp_split_pages, from);
		no_subpage_counting = true;
		retry = 1;
		goto thp_subpage_migration;
	}

	rc = nr_failed + nr_thp_failed;
1521
out:
1522 1523 1524 1525 1526 1527
	/*
	 * 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);

1528
	count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
1529
	count_vm_events(PGMIGRATE_FAIL, nr_failed_pages);
1530 1531 1532
	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);
1533
	trace_mm_migrate_pages(nr_succeeded, nr_failed_pages, nr_thp_succeeded,
1534
			       nr_thp_failed, nr_thp_split, mode, reason);
1535

1536 1537 1538
	if (!swapwrite)
		current->flags &= ~PF_SWAPWRITE;

1539 1540 1541
	if (ret_succeeded)
		*ret_succeeded = nr_succeeded;

1542
	return rc;
1543
}
1544

1545
struct page *alloc_migration_target(struct page *page, unsigned long private)
1546
{
1547 1548
	struct migration_target_control *mtc;
	gfp_t gfp_mask;
1549 1550
	unsigned int order = 0;
	struct page *new_page = NULL;
1551 1552 1553 1554 1555 1556 1557 1558
	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);
1559

1560 1561 1562
	if (PageHuge(page)) {
		struct hstate *h = page_hstate(compound_head(page));

1563 1564
		gfp_mask = htlb_modify_alloc_mask(h, gfp_mask);
		return alloc_huge_page_nodemask(h, nid, mtc->nmask, gfp_mask);
1565
	}
1566 1567

	if (PageTransHuge(page)) {
1568 1569 1570 1571 1572
		/*
		 * clear __GFP_RECLAIM to make the migration callback
		 * consistent with regular THP allocations.
		 */
		gfp_mask &= ~__GFP_RECLAIM;
1573 1574 1575
		gfp_mask |= GFP_TRANSHUGE;
		order = HPAGE_PMD_ORDER;
	}
1576 1577
	zidx = zone_idx(page_zone(page));
	if (is_highmem_idx(zidx) || zidx == ZONE_MOVABLE)
1578 1579
		gfp_mask |= __GFP_HIGHMEM;

1580
	new_page = __alloc_pages(gfp_mask, order, nid, mtc->nmask);
1581 1582 1583 1584 1585 1586 1587

	if (new_page && PageTransHuge(new_page))
		prep_transhuge_page(new_page);

	return new_page;
}

1588 1589
#ifdef CONFIG_NUMA

1590
static int store_status(int __user *status, int start, int value, int nr)
1591
{
1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604
	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;
1605 1606 1607 1608
	struct migration_target_control mtc = {
		.nid = node,
		.gfp_mask = GFP_HIGHUSER_MOVABLE | __GFP_THISNODE,
	};
1609

1610
	err = migrate_pages(pagelist, alloc_migration_target, NULL,
1611
		(unsigned long)&mtc, MIGRATE_SYNC, MR_SYSCALL, NULL);
1612 1613 1614
	if (err)
		putback_movable_pages(pagelist);
	return err;
1615 1616 1617
}

/*
1618 1619
 * Resolves the given address to a struct page, isolates it from the LRU and
 * puts it to the given pagelist.
1620 1621 1622 1623 1624
 * 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
1625
 */
1626 1627
static int add_page_for_migration(struct mm_struct *mm, unsigned long addr,
		int node, struct list_head *pagelist, bool migrate_all)
1628
{
1629 1630 1631
	struct vm_area_struct *vma;
	struct page *page;
	unsigned int follflags;
1632 1633
	int err;

1634
	mmap_read_lock(mm);
1635 1636 1637 1638
	err = -EFAULT;
	vma = find_vma(mm, addr);
	if (!vma || addr < vma->vm_start || !vma_migratable(vma))
		goto out;
1639

1640 1641 1642
	/* FOLL_DUMP to ignore special (like zero) pages */
	follflags = FOLL_GET | FOLL_DUMP;
	page = follow_page(vma, addr, follflags);
1643

1644 1645 1646
	err = PTR_ERR(page);
	if (IS_ERR(page))
		goto out;
1647

1648 1649 1650
	err = -ENOENT;
	if (!page)
		goto out;
1651

1652 1653 1654
	err = 0;
	if (page_to_nid(page) == node)
		goto out_putpage;
1655

1656 1657 1658
	err = -EACCES;
	if (page_mapcount(page) > 1 && !migrate_all)
		goto out_putpage;
1659

1660 1661 1662
	if (PageHuge(page)) {
		if (PageHead(page)) {
			isolate_huge_page(page, pagelist);
1663
			err = 1;
1664
		}
1665 1666
	} else {
		struct page *head;
1667

1668 1669
		head = compound_head(page);
		err = isolate_lru_page(head);
1670
		if (err)
1671
			goto out_putpage;
1672

1673
		err = 1;
1674 1675
		list_add_tail(&head->lru, pagelist);
		mod_node_page_state(page_pgdat(head),
1676
			NR_ISOLATED_ANON + page_is_file_lru(head),
1677
			thp_nr_pages(head));
1678 1679 1680 1681 1682 1683 1684 1685 1686
	}
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:
1687
	mmap_read_unlock(mm);
1688 1689 1690
	return err;
}

1691 1692 1693 1694 1695 1696
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;

1697 1698 1699
	if (list_empty(pagelist))
		return 0;

1700 1701 1702 1703 1704 1705
	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
1706
		 * pages, so need to include the rest of the
1707 1708 1709 1710 1711 1712 1713 1714 1715 1716
		 * 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);
}

1717 1718 1719 1720
/*
 * Migrate an array of page address onto an array of nodes and fill
 * the corresponding array of status.
 */
1721
static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
1722 1723 1724 1725 1726
			 unsigned long nr_pages,
			 const void __user * __user *pages,
			 const int __user *nodes,
			 int __user *status, int flags)
{
1727 1728 1729 1730
	int current_node = NUMA_NO_NODE;
	LIST_HEAD(pagelist);
	int start, i;
	int err = 0, err1;
1731

1732
	lru_cache_disable();
1733

1734 1735 1736 1737
	for (i = start = 0; i < nr_pages; i++) {
		const void __user *p;
		unsigned long addr;
		int node;
1738

1739 1740 1741 1742 1743
		err = -EFAULT;
		if (get_user(p, pages + i))
			goto out_flush;
		if (get_user(node, nodes + i))
			goto out_flush;
1744
		addr = (unsigned long)untagged_addr(p);
1745 1746 1747 1748 1749 1750

		err = -ENODEV;
		if (node < 0 || node >= MAX_NUMNODES)
			goto out_flush;
		if (!node_state(node, N_MEMORY))
			goto out_flush;
1751

1752 1753 1754 1755 1756 1757 1758 1759
		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) {
1760 1761
			err = move_pages_and_store_status(mm, current_node,
					&pagelist, status, start, i, nr_pages);
1762 1763 1764 1765
			if (err)
				goto out;
			start = i;
			current_node = node;
1766 1767
		}

1768 1769 1770 1771 1772 1773
		/*
		 * 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);
1774

1775
		if (err > 0) {
1776 1777 1778
			/* The page is successfully queued for migration */
			continue;
		}
1779

1780 1781 1782 1783 1784
		/*
		 * 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);
1785 1786
		if (err)
			goto out_flush;
1787

1788 1789
		err = move_pages_and_store_status(mm, current_node, &pagelist,
				status, start, i, nr_pages);
1790 1791
		if (err)
			goto out;
1792
		current_node = NUMA_NO_NODE;
1793
	}
1794 1795
out_flush:
	/* Make sure we do not overwrite the existing error */
1796 1797
	err1 = move_pages_and_store_status(mm, current_node, &pagelist,
				status, start, i, nr_pages);
1798
	if (err >= 0)
1799
		err = err1;
1800
out:
1801
	lru_cache_enable();
1802 1803 1804
	return err;
}

1805
/*
1806
 * Determine the nodes of an array of pages and store it in an array of status.
1807
 */
1808 1809
static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
				const void __user **pages, int *status)
1810
{
1811 1812
	unsigned long i;

1813
	mmap_read_lock(mm);
1814

1815
	for (i = 0; i < nr_pages; i++) {
1816
		unsigned long addr = (unsigned long)(*pages);
1817 1818
		struct vm_area_struct *vma;
		struct page *page;
1819
		int err = -EFAULT;
1820

1821 1822
		vma = vma_lookup(mm, addr);
		if (!vma)
1823 1824
			goto set_status;

1825 1826
		/* FOLL_DUMP to ignore special (like zero) pages */
		page = follow_page(vma, addr, FOLL_DUMP);
1827 1828 1829 1830 1831

		err = PTR_ERR(page);
		if (IS_ERR(page))
			goto set_status;

1832
		err = page ? page_to_nid(page) : -ENOENT;
1833
set_status:
1834 1835 1836 1837 1838 1839
		*status = err;

		pages++;
		status++;
	}

1840
	mmap_read_unlock(mm);
1841 1842
}

1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859
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;
}

1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871
/*
 * 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];

1872 1873
	while (nr_pages) {
		unsigned long chunk_nr;
1874

1875 1876 1877 1878
		chunk_nr = nr_pages;
		if (chunk_nr > DO_PAGES_STAT_CHUNK_NR)
			chunk_nr = DO_PAGES_STAT_CHUNK_NR;

1879 1880 1881 1882 1883 1884 1885 1886 1887
		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;
		}
1888 1889 1890

		do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);

1891 1892
		if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
			break;
1893

1894 1895 1896 1897 1898
		pages += chunk_nr;
		status += chunk_nr;
		nr_pages -= chunk_nr;
	}
	return nr_pages ? -EFAULT : 0;
1899 1900
}

1901
static struct mm_struct *find_mm_struct(pid_t pid, nodemask_t *mem_nodes)
1902 1903 1904 1905
{
	struct task_struct *task;
	struct mm_struct *mm;

1906 1907 1908 1909 1910 1911 1912 1913 1914
	/*
	 * 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;
	}
1915 1916

	/* Find the mm_struct */
1917
	rcu_read_lock();
1918
	task = find_task_by_vpid(pid);
1919
	if (!task) {
1920
		rcu_read_unlock();
1921
		return ERR_PTR(-ESRCH);
1922
	}
1923
	get_task_struct(task);
1924 1925 1926

	/*
	 * Check if this process has the right to modify the specified
1927
	 * process. Use the regular "ptrace_may_access()" checks.
1928
	 */
1929
	if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
1930
		rcu_read_unlock();
1931
		mm = ERR_PTR(-EPERM);
1932
		goto out;
1933
	}
1934
	rcu_read_unlock();
1935

1936 1937
	mm = ERR_PTR(security_task_movememory(task));
	if (IS_ERR(mm))
1938
		goto out;
1939
	*mem_nodes = cpuset_mems_allowed(task);
1940
	mm = get_task_mm(task);
1941
out:
1942
	put_task_struct(task);
1943
	if (!mm)
1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962
		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))
1963 1964
		return -EINVAL;

1965 1966 1967 1968 1969 1970 1971
	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);

1972 1973 1974 1975 1976
	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);
1977 1978 1979 1980 1981

	mmput(mm);
	return err;
}

1982 1983 1984 1985 1986 1987 1988 1989
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);
}

1990 1991 1992 1993 1994 1995
#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,
1996
				   unsigned long nr_migrate_pages)
1997 1998
{
	int z;
1999

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
	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,
2010
				       ZONE_MOVABLE, 0))
2011 2012 2013 2014 2015 2016 2017
			continue;
		return true;
	}
	return false;
}

static struct page *alloc_misplaced_dst_page(struct page *page,
2018
					   unsigned long data)
2019 2020 2021 2022
{
	int nid = (int) data;
	struct page *newpage;

2023
	newpage = __alloc_pages_node(nid,
2024 2025 2026
					 (GFP_HIGHUSER_MOVABLE |
					  __GFP_THISNODE | __GFP_NOMEMALLOC |
					  __GFP_NORETRY | __GFP_NOWARN) &
2027
					 ~__GFP_RECLAIM, 0);
2028

2029 2030 2031
	return newpage;
}

2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048
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;
}

2049
static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
2050
{
2051
	int page_lru;
2052
	int nr_pages = thp_nr_pages(page);
2053

2054
	VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page);
2055

2056 2057 2058 2059
	/* Do not migrate THP mapped by multiple processes */
	if (PageTransHuge(page) && total_mapcount(page) > 1)
		return 0;

2060
	/* Avoid migrating to a node that is nearly full */
2061
	if (!migrate_balanced_pgdat(pgdat, nr_pages))
2062
		return 0;
2063

2064 2065
	if (isolate_lru_page(page))
		return 0;
2066

2067
	page_lru = page_is_file_lru(page);
2068
	mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_lru,
2069
			    nr_pages);
2070

2071
	/*
2072 2073 2074
	 * Isolating the page has taken another reference, so the
	 * caller's reference can be safely dropped without the page
	 * disappearing underneath us during migration.
2075 2076
	 */
	put_page(page);
2077
	return 1;
2078 2079 2080 2081 2082 2083 2084
}

/*
 * 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.
 */
2085 2086
int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
			   int node)
2087 2088
{
	pg_data_t *pgdat = NODE_DATA(node);
2089
	int isolated;
2090 2091
	int nr_remaining;
	LIST_HEAD(migratepages);
2092 2093
	new_page_t *new;
	bool compound;
2094
	int nr_pages = thp_nr_pages(page);
2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106

	/*
	 * 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;
2107 2108

	/*
2109 2110
	 * Don't migrate file pages that are mapped in multiple processes
	 * with execute permissions as they are probably shared libraries.
2111
	 */
2112 2113
	if (page_mapcount(page) != 1 && page_is_file_lru(page) &&
	    (vma->vm_flags & VM_EXEC))
2114 2115
		goto out;

2116 2117 2118 2119
	/*
	 * Also do not migrate dirty pages as not all filesystems can move
	 * dirty pages in MIGRATE_ASYNC mode which is a waste of cycles.
	 */
2120
	if (page_is_file_lru(page) && PageDirty(page))
2121 2122
		goto out;

2123 2124 2125 2126 2127
	isolated = numamigrate_isolate_page(pgdat, page);
	if (!isolated)
		goto out;

	list_add(&page->lru, &migratepages);
2128
	nr_remaining = migrate_pages(&migratepages, *new, NULL, node,
2129
				     MIGRATE_ASYNC, MR_NUMA_MISPLACED, NULL);
2130
	if (nr_remaining) {
2131 2132
		if (!list_empty(&migratepages)) {
			list_del(&page->lru);
2133 2134
			mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
					page_is_file_lru(page), -nr_pages);
2135 2136
			putback_lru_page(page);
		}
2137 2138
		isolated = 0;
	} else
2139
		count_vm_numa_events(NUMA_PAGE_MIGRATE, nr_pages);
2140 2141
	BUG_ON(!list_empty(&migratepages));
	return isolated;
2142 2143 2144 2145

out:
	put_page(page);
	return 0;
2146
}
2147
#endif /* CONFIG_NUMA_BALANCING */
2148
#endif /* CONFIG_NUMA */
2149

2150
#ifdef CONFIG_DEVICE_PRIVATE
2151
static int migrate_vma_collect_skip(unsigned long start,
2152 2153 2154 2155 2156 2157
				    unsigned long end,
				    struct mm_walk *walk)
{
	struct migrate_vma *migrate = walk->private;
	unsigned long addr;

2158
	for (addr = start; addr < end; addr += PAGE_SIZE) {
2159
		migrate->dst[migrate->npages] = 0;
2160
		migrate->src[migrate->npages++] = 0;
2161 2162 2163 2164 2165
	}

	return 0;
}

2166
static int migrate_vma_collect_hole(unsigned long start,
2167
				    unsigned long end,
2168
				    __always_unused int depth,
2169 2170 2171 2172 2173
				    struct mm_walk *walk)
{
	struct migrate_vma *migrate = walk->private;
	unsigned long addr;

2174 2175 2176 2177
	/* Only allow populating anonymous memory. */
	if (!vma_is_anonymous(walk->vma))
		return migrate_vma_collect_skip(start, end, walk);

2178
	for (addr = start; addr < end; addr += PAGE_SIZE) {
2179
		migrate->src[migrate->npages] = MIGRATE_PFN_MIGRATE;
2180
		migrate->dst[migrate->npages] = 0;
2181 2182
		migrate->npages++;
		migrate->cpages++;
2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195
	}

	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;
2196
	unsigned long addr = start, unmapped = 0;
2197 2198 2199 2200 2201
	spinlock_t *ptl;
	pte_t *ptep;

again:
	if (pmd_none(*pmdp))
2202
		return migrate_vma_collect_hole(start, end, -1, walk);
2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217

	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))
2218
				return migrate_vma_collect_skip(start, end,
2219 2220 2221 2222 2223 2224 2225
								walk);
		} else {
			int ret;

			get_page(page);
			spin_unlock(ptl);
			if (unlikely(!trylock_page(page)))
2226
				return migrate_vma_collect_skip(start, end,
2227 2228 2229 2230
								walk);
			ret = split_huge_page(page);
			unlock_page(page);
			put_page(page);
2231 2232 2233 2234
			if (ret)
				return migrate_vma_collect_skip(start, end,
								walk);
			if (pmd_none(*pmdp))
2235
				return migrate_vma_collect_hole(start, end, -1,
2236 2237 2238 2239 2240
								walk);
		}
	}

	if (unlikely(pmd_bad(*pmdp)))
2241
		return migrate_vma_collect_skip(start, end, walk);
2242 2243

	ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
2244 2245
	arch_enter_lazy_mmu_mode();

2246
	for (; addr < end; addr += PAGE_SIZE, ptep++) {
2247
		unsigned long mpfn = 0, pfn;
2248
		struct page *page;
2249
		swp_entry_t entry;
2250 2251 2252 2253
		pte_t pte;

		pte = *ptep;

2254
		if (pte_none(pte)) {
2255 2256 2257 2258
			if (vma_is_anonymous(vma)) {
				mpfn = MIGRATE_PFN_MIGRATE;
				migrate->cpages++;
			}
2259 2260 2261
			goto next;
		}

2262 2263 2264 2265 2266 2267 2268 2269 2270 2271
		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;

2272
			page = pfn_swap_entry_to_page(entry);
2273 2274 2275
			if (!(migrate->flags &
				MIGRATE_VMA_SELECT_DEVICE_PRIVATE) ||
			    page->pgmap->owner != migrate->pgmap_owner)
2276 2277
				goto next;

2278 2279
			mpfn = migrate_pfn(page_to_pfn(page)) |
					MIGRATE_PFN_MIGRATE;
2280
			if (is_writable_device_private_entry(entry))
2281 2282
				mpfn |= MIGRATE_PFN_WRITE;
		} else {
2283
			if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM))
2284
				goto next;
2285
			pfn = pte_pfn(pte);
2286 2287 2288 2289 2290
			if (is_zero_pfn(pfn)) {
				mpfn = MIGRATE_PFN_MIGRATE;
				migrate->cpages++;
				goto next;
			}
2291
			page = vm_normal_page(migrate->vma, addr, pte);
2292 2293 2294 2295
			mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
			mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
		}

2296 2297
		/* FIXME support THP */
		if (!page || !page->mapping || PageTransCompound(page)) {
2298
			mpfn = 0;
2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312
			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);

2313 2314 2315 2316 2317 2318 2319 2320
		/*
		 * 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;

2321
			migrate->cpages++;
2322 2323 2324
			ptep_get_and_clear(mm, addr, ptep);

			/* Setup special migration page table entry */
2325 2326 2327 2328 2329 2330
			if (mpfn & MIGRATE_PFN_WRITE)
				entry = make_writable_migration_entry(
							page_to_pfn(page));
			else
				entry = make_readable_migration_entry(
							page_to_pfn(page));
2331
			swp_pte = swp_entry_to_pte(entry);
2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342
			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);
			}
2343 2344 2345 2346 2347 2348 2349 2350 2351
			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);
2352 2353 2354

			if (pte_present(pte))
				unmapped++;
2355 2356 2357
		} else {
			put_page(page);
			mpfn = 0;
2358 2359
		}

2360
next:
2361
		migrate->dst[migrate->npages] = 0;
2362 2363
		migrate->src[migrate->npages++] = mpfn;
	}
2364
	arch_leave_lazy_mmu_mode();
2365 2366
	pte_unmap_unlock(ptep - 1, ptl);

2367 2368 2369 2370
	/* Only flush the TLB if we actually modified any entries */
	if (unmapped)
		flush_tlb_range(walk->vma, start, end);

2371 2372 2373
	return 0;
}

2374 2375 2376 2377 2378
static const struct mm_walk_ops migrate_vma_walk_ops = {
	.pmd_entry		= migrate_vma_collect_pmd,
	.pte_hole		= migrate_vma_collect_hole,
};

2379 2380 2381 2382 2383 2384 2385 2386 2387 2388
/*
 * 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)
{
2389
	struct mmu_notifier_range range;
2390

2391 2392 2393 2394 2395
	/*
	 * 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.
	 */
2396 2397
	mmu_notifier_range_init_owner(&range, MMU_NOTIFY_MIGRATE, 0,
		migrate->vma, migrate->vma->vm_mm, migrate->start, migrate->end,
2398
		migrate->pgmap_owner);
2399
	mmu_notifier_invalidate_range_start(&range);
2400

2401 2402 2403 2404
	walk_page_range(migrate->vma->vm_mm, migrate->start, migrate->end,
			&migrate_vma_walk_ops, migrate);

	mmu_notifier_invalidate_range_end(&range);
2405 2406 2407 2408 2409 2410 2411 2412
	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
2413
 * folio_migrate_mapping(), except that here we allow migration of a
2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432
 * 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;

2433 2434 2435 2436 2437 2438 2439 2440 2441
	/* 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
2442
		 * infinite loop (one stopping migration because the other is
2443 2444 2445 2446 2447
		 * 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.
		 */
2448
		return is_device_private_page(page);
2449 2450
	}

2451 2452 2453 2454
	/* For file back page */
	if (page_mapping(page))
		extra += 1 + page_has_private(page);

2455 2456 2457 2458 2459 2460 2461
	if ((page_count(page) - extra) > page_mapcount(page))
		return false;

	return true;
}

/*
2462
 * migrate_vma_unmap() - replace page mapping with special migration pte entry
2463 2464
 * @migrate: migrate struct containing all migration information
 *
2465 2466 2467 2468 2469 2470
 * Isolate pages from the LRU and replace mappings (CPU page table pte) with a
 * special migration pte entry and check 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.
2471
 */
2472
static void migrate_vma_unmap(struct migrate_vma *migrate)
2473 2474
{
	const unsigned long npages = migrate->npages;
2475
	unsigned long i, restore = 0;
2476 2477 2478 2479
	bool allow_drain = true;

	lru_add_drain();

2480
	for (i = 0; i < npages; i++) {
2481 2482 2483 2484 2485
		struct page *page = migrate_pfn_to_page(migrate->src[i]);

		if (!page)
			continue;

2486 2487 2488 2489 2490 2491 2492
		/* 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;
			}
2493

2494
			if (isolate_lru_page(page)) {
2495 2496 2497
				migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
				migrate->cpages--;
				restore++;
2498
				continue;
2499
			}
2500 2501 2502

			/* Drop the reference we took in collect */
			put_page(page);
2503 2504
		}

2505 2506
		if (page_mapped(page))
			try_to_migrate(page, 0);
2507

2508 2509 2510 2511
		if (page_mapped(page) || !migrate_vma_check_page(page)) {
			if (!is_zone_device_page(page)) {
				get_page(page);
				putback_lru_page(page);
2512 2513
			}

2514 2515 2516
			migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
			migrate->cpages--;
			restore++;
2517
			continue;
2518 2519 2520
		}
	}

2521
	for (i = 0; i < npages && restore; i++) {
2522 2523 2524 2525 2526 2527 2528 2529 2530
		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);
2531
		put_page(page);
2532 2533 2534 2535
		restore--;
	}
}

2536 2537
/**
 * migrate_vma_setup() - prepare to migrate a range of memory
2538
 * @args: contains the vma, start, and pfns arrays for the migration
2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554
 *
 * 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
2555 2556
 * page and with MIGRATE_PFN_VALID. Destination pages must be locked via
 * lock_page().
2557 2558 2559 2560 2561 2562 2563 2564 2565 2566
 *
 * 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
I
Ingo Molnar 已提交
2567 2568
 * allowing the caller to allocate device memory for those unbacked virtual
 * addresses.  For this the caller simply has to allocate device memory and
2569
 * properly set the destination entry like for regular migration.  Note that
I
Ingo Molnar 已提交
2570 2571
 * 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(),
2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590
 * 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
2591
 * both destination and source page are still locked, and the mmap_lock is held
2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637
 * 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_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);

2638 2639 2640 2641 2642 2643 2644 2645
/*
 * 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.
 */
2646 2647 2648
static void migrate_vma_insert_page(struct migrate_vma *migrate,
				    unsigned long addr,
				    struct page *page,
2649
				    unsigned long *src)
2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671 2672 2673 2674 2675 2676 2677 2678 2679 2680 2681 2682 2683 2684
{
	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.
	 *
2685
	 * pte_alloc_map() is safe to use under mmap_write_lock(mm) or when
2686 2687
	 * parallel threads are excluded by other means.
	 *
2688
	 * Here we only have mmap_read_lock(mm).
2689
	 */
2690
	if (pte_alloc(mm, pmdp))
2691 2692 2693 2694 2695 2696 2697 2698
		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;
2699
	if (mem_cgroup_charge(page_folio(page), vma->vm_mm, GFP_KERNEL))
2700 2701 2702 2703 2704 2705 2706 2707 2708
		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);

2709 2710 2711 2712
	if (is_zone_device_page(page)) {
		if (is_device_private_page(page)) {
			swp_entry_t swp_entry;

2713 2714 2715 2716 2717 2718
			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));
2719
			entry = swp_entry_to_pte(swp_entry);
2720 2721 2722 2723 2724 2725 2726
		} else {
			/*
			 * For now we only support migrating to un-addressable
			 * device memory.
			 */
			pr_warn_once("Unsupported ZONE_DEVICE page type.\n");
			goto abort;
2727
		}
2728 2729 2730 2731 2732 2733 2734 2735
	} 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);

2736 2737 2738
	if (check_stable_address_space(mm))
		goto unlock_abort;

2739 2740 2741
	if (pte_present(*ptep)) {
		unsigned long pfn = pte_pfn(*ptep);

2742 2743
		if (!is_zero_pfn(pfn))
			goto unlock_abort;
2744
		flush = true;
2745 2746
	} else if (!pte_none(*ptep))
		goto unlock_abort;
2747 2748

	/*
2749
	 * Check for userfaultfd but do not deliver the fault. Instead,
2750 2751
	 * just back off.
	 */
2752 2753
	if (userfaultfd_missing(vma))
		goto unlock_abort;
2754 2755

	inc_mm_counter(mm, MM_ANONPAGES);
2756
	page_add_new_anon_rmap(page, vma, addr, false);
2757
	if (!is_zone_device_page(page))
2758
		lru_cache_add_inactive_or_unevictable(page, vma);
2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 2769 2770 2771 2772 2773 2774 2775
	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;

2776 2777
unlock_abort:
	pte_unmap_unlock(ptep, ptl);
2778 2779 2780 2781
abort:
	*src &= ~MIGRATE_PFN_MIGRATE;
}

2782
/**
2783 2784 2785 2786 2787 2788 2789
 * 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.
 */
2790
void migrate_vma_pages(struct migrate_vma *migrate)
2791 2792 2793
{
	const unsigned long npages = migrate->npages;
	const unsigned long start = migrate->start;
2794 2795
	struct mmu_notifier_range range;
	unsigned long addr, i;
2796
	bool notified = false;
2797 2798 2799 2800 2801 2802 2803

	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;

2804 2805
		if (!newpage) {
			migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2806
			continue;
2807 2808 2809
		}

		if (!page) {
2810
			if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE))
2811 2812 2813
				continue;
			if (!notified) {
				notified = true;
2814

2815 2816 2817
				mmu_notifier_range_init_owner(&range,
					MMU_NOTIFY_MIGRATE, 0, migrate->vma,
					migrate->vma->vm_mm, addr, migrate->end,
2818
					migrate->pgmap_owner);
2819
				mmu_notifier_invalidate_range_start(&range);
2820 2821
			}
			migrate_vma_insert_page(migrate, addr, newpage,
2822
						&migrate->src[i]);
2823
			continue;
2824
		}
2825 2826 2827

		mapping = page_mapping(page);

2828 2829 2830 2831 2832 2833 2834 2835 2836 2837
		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;
				}
2838
			} else {
2839 2840 2841 2842 2843 2844 2845 2846 2847
				/*
				 * Other types of ZONE_DEVICE page are not
				 * supported.
				 */
				migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
				continue;
			}
		}

2848 2849 2850 2851
		r = migrate_page(mapping, newpage, page, MIGRATE_SYNC_NO_COPY);
		if (r != MIGRATEPAGE_SUCCESS)
			migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
	}
2852

2853 2854 2855 2856 2857
	/*
	 * 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.
	 */
2858
	if (notified)
2859
		mmu_notifier_invalidate_range_only_end(&range);
2860
}
2861
EXPORT_SYMBOL(migrate_vma_pages);
2862

2863
/**
2864 2865 2866 2867 2868 2869 2870 2871 2872 2873
 * 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.
 */
2874
void migrate_vma_finalize(struct migrate_vma *migrate)
2875 2876 2877 2878 2879 2880 2881 2882
{
	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]);

2883 2884 2885 2886 2887
		if (!page) {
			if (newpage) {
				unlock_page(newpage);
				put_page(newpage);
			}
2888
			continue;
2889 2890
		}

2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901
		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);

2902 2903 2904 2905
		if (is_zone_device_page(page))
			put_page(page);
		else
			putback_lru_page(page);
2906 2907 2908

		if (newpage != page) {
			unlock_page(newpage);
2909 2910 2911 2912
			if (is_zone_device_page(newpage))
				put_page(newpage);
			else
				putback_lru_page(newpage);
2913 2914 2915
		}
	}
}
2916
EXPORT_SYMBOL(migrate_vma_finalize);
2917
#endif /* CONFIG_DEVICE_PRIVATE */
2918

2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956 2957 2958 2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969 2970 2971 2972 2973 2974 2975 2976 2977 2978 2979 2980 2981 2982 2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011 3012 3013 3014 3015 3016 3017 3018 3019 3020 3021 3022 3023 3024 3025 3026 3027 3028 3029 3030 3031 3032 3033 3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049 3050
/*
 * 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:
 *
 *	{  nr=1, nodes[0]=1 }, // Node 0 migrates to 1
 *	{  nr=1, nodes[0]=2 }, // Node 1 migrates to 2
 *	{  nr=0, nodes[0]=-1 }, // Node 2 does not migrate
 *	{  nr=1, nodes[0]=4 }, // Node 3 migrates to 4
 *	{  nr=1, nodes[0]=5 }, // Node 4 migrates to 5
 *	{  nr=0, nodes[0]=-1 }, // Node 5 does not migrate
 *
 * Moreover some systems may have multiple slow memory nodes.
 * Suppose a system has one socket with 3 memory nodes, node 0
 * is fast memory type, and node 1/2 both are slow memory
 * type, and the distance between fast memory node and slow
 * memory node is same. So the migration path should be:
 *
 *	0 -> 1/2 -> stop
 *
 * This is represented in the node_demotion[] like this:
 *	{ nr=2, {nodes[0]=1, nodes[1]=2} }, // Node 0 migrates to node 1 and node 2
 *	{ nr=0, nodes[0]=-1, }, // Node 1 dose not migrate
 *	{ nr=0, nodes[0]=-1, }, // Node 2 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.
 */
#define DEFAULT_DEMOTION_TARGET_NODES 15

#if MAX_NUMNODES < DEFAULT_DEMOTION_TARGET_NODES
#define DEMOTION_TARGET_NODES	(MAX_NUMNODES - 1)
#else
#define DEMOTION_TARGET_NODES	DEFAULT_DEMOTION_TARGET_NODES
#endif

struct demotion_nodes {
	unsigned short nr;
	short nodes[DEMOTION_TARGET_NODES];
};

static struct demotion_nodes *node_demotion __read_mostly;

/**
 * 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)
{
	struct demotion_nodes *nd;
	unsigned short target_nr, index;
	int target;

	if (!node_demotion)
		return NUMA_NO_NODE;

	nd = &node_demotion[node];

	/*
	 * 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_nr = READ_ONCE(nd->nr);

	switch (target_nr) {
	case 0:
		target = NUMA_NO_NODE;
		goto out;
	case 1:
		index = 0;
		break;
	default:
		/*
		 * If there are multiple target nodes, just select one
		 * target node randomly.
		 *
		 * In addition, we can also use round-robin to select
		 * target node, but we should introduce another variable
		 * for node_demotion[] to record last selected target node,
		 * that may cause cache ping-pong due to the changing of
		 * last target node. Or introducing per-cpu data to avoid
		 * caching issue, which seems more complicated. So selecting
		 * target node randomly seems better until now.
		 */
		index = get_random_int() % target_nr;
		break;
	}

	target = READ_ONCE(nd->nodes[index]);

out:
	rcu_read_unlock();
	return target;
}

3051
#if defined(CONFIG_HOTPLUG_CPU)
3052 3053 3054
/* Disable reclaim-based migration. */
static void __disable_all_migrate_targets(void)
{
3055
	int node, i;
3056

3057 3058
	if (!node_demotion)
		return;
3059

3060 3061 3062 3063 3064
	for_each_online_node(node) {
		node_demotion[node].nr = 0;
		for (i = 0; i < DEMOTION_TARGET_NODES; i++)
			node_demotion[node].nodes[i] = NUMA_NO_NODE;
	}
3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081 3082 3083 3084 3085 3086 3087 3088 3089 3090
}

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.
 */
3091 3092
static int establish_migrate_target(int node, nodemask_t *used,
				    int best_distance)
3093
{
3094 3095
	int migration_target, index, val;
	struct demotion_nodes *nd;
3096

3097
	if (!node_demotion)
3098 3099
		return NUMA_NO_NODE;

3100 3101
	nd = &node_demotion[node];

3102 3103 3104 3105
	migration_target = find_next_best_node(node, used);
	if (migration_target == NUMA_NO_NODE)
		return NUMA_NO_NODE;

3106 3107 3108 3109 3110 3111 3112 3113 3114 3115 3116 3117 3118 3119 3120 3121 3122 3123 3124
	/*
	 * If the node has been set a migration target node before,
	 * which means it's the best distance between them. Still
	 * check if this node can be demoted to other target nodes
	 * if they have a same best distance.
	 */
	if (best_distance != -1) {
		val = node_distance(node, migration_target);
		if (val > best_distance)
			return NUMA_NO_NODE;
	}

	index = nd->nr;
	if (WARN_ONCE(index >= DEMOTION_TARGET_NODES,
		      "Exceeds maximum demotion target nodes\n"))
		return NUMA_NO_NODE;

	nd->nodes[index] = migration_target;
	nd->nr++;
3125 3126 3127 3128 3129 3130 3131 3132 3133 3134 3135 3136 3137 3138 3139

	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
3140 3141 3142
 * node1 migrates to can migrate to node0. Also one node can
 * be migrated to multiple nodes if the target nodes all have
 * a same best-distance against the source node.
3143 3144 3145 3146 3147 3148 3149 3150 3151 3152 3153
 *
 * 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;
3154
	int node, best_distance;
3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183

	/*
	 * 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);

3184 3185
	for_each_node_mask(node, this_pass) {
		best_distance = -1;
3186 3187

		/*
3188 3189 3190
		 * Try to set up the migration path for the node, and the target
		 * migration nodes can be multiple, so doing a loop to find all
		 * the target nodes if they all have a best node distance.
3191
		 */
3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209
		do {
			int target_node =
				establish_migrate_target(node, &used_targets,
							 best_distance);

			if (target_node == NUMA_NO_NODE)
				break;

			if (best_distance == -1)
				best_distance = node_distance(node, target_node);

			/*
			 * 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);
		} while (1);
3210 3211 3212 3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228
	}
	/*
	 * '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();
}
3229 3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241

/*
 * 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,
3242
						 unsigned long action, void *_arg)
3243
{
3244 3245 3246 3247 3248 3249 3250 3251 3252 3253
	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);

3254 3255 3256 3257 3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279 3280 3281 3282 3283 3284 3285 3286
	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);
}

3287 3288 3289 3290 3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302 3303 3304 3305
/*
 * 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;
}

3306 3307 3308 3309
static int __init migrate_on_reclaim_init(void)
{
	int ret;

3310 3311 3312 3313 3314
	node_demotion = kmalloc_array(nr_node_ids,
				      sizeof(struct demotion_nodes),
				      GFP_KERNEL);
	WARN_ON(!node_demotion);

3315 3316
	ret = cpuhp_setup_state_nocalls(CPUHP_MM_DEMOTION_DEAD, "mm/demotion:offline",
					NULL, migration_offline_cpu);
3317 3318 3319 3320 3321 3322 3323
	/*
	 * 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);
3324 3325 3326
	ret = cpuhp_setup_state(CPUHP_AP_MM_DEMOTION_ONLINE, "mm/demotion:online",
				migration_online_cpu, NULL);
	WARN_ON(ret < 0);
3327 3328 3329 3330 3331

	hotplug_memory_notifier(migrate_on_reclaim_callback, 100);
	return 0;
}
late_initcall(migrate_on_reclaim_init);
3332
#endif /* CONFIG_HOTPLUG_CPU */
3333 3334 3335 3336 3337 3338 3339 3340 3341 3342 3343 3344 3345 3346 3347 3348 3349 3350 3351 3352 3353 3354 3355 3356 3357 3358 3359 3360 3361 3362 3363 3364 3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375 3376 3377 3378 3379 3380 3381 3382 3383 3384 3385 3386 3387 3388 3389 3390 3391 3392 3393

bool numa_demotion_enabled = false;

#ifdef CONFIG_SYSFS
static ssize_t numa_demotion_enabled_show(struct kobject *kobj,
					  struct kobj_attribute *attr, char *buf)
{
	return sysfs_emit(buf, "%s\n",
			  numa_demotion_enabled ? "true" : "false");
}

static ssize_t numa_demotion_enabled_store(struct kobject *kobj,
					   struct kobj_attribute *attr,
					   const char *buf, size_t count)
{
	if (!strncmp(buf, "true", 4) || !strncmp(buf, "1", 1))
		numa_demotion_enabled = true;
	else if (!strncmp(buf, "false", 5) || !strncmp(buf, "0", 1))
		numa_demotion_enabled = false;
	else
		return -EINVAL;

	return count;
}

static struct kobj_attribute numa_demotion_enabled_attr =
	__ATTR(demotion_enabled, 0644, numa_demotion_enabled_show,
	       numa_demotion_enabled_store);

static struct attribute *numa_attrs[] = {
	&numa_demotion_enabled_attr.attr,
	NULL,
};

static const struct attribute_group numa_attr_group = {
	.attrs = numa_attrs,
};

static int __init numa_init_sysfs(void)
{
	int err;
	struct kobject *numa_kobj;

	numa_kobj = kobject_create_and_add("numa", mm_kobj);
	if (!numa_kobj) {
		pr_err("failed to create numa kobject\n");
		return -ENOMEM;
	}
	err = sysfs_create_group(numa_kobj, &numa_attr_group);
	if (err) {
		pr_err("failed to register numa group\n");
		goto delete_obj;
	}
	return 0;

delete_obj:
	kobject_put(numa_kobj);
	return err;
}
subsys_initcall(numa_init_sysfs);
#endif
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