migrate.c 30.9 KB
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C
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/*
 * Memory Migration functionality - linux/mm/migration.c
 *
 * Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter
 *
 * Page migration was first developed in the context of the memory hotplug
 * project. The main authors of the migration code are:
 *
 * IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
 * Hirokazu Takahashi <taka@valinux.co.jp>
 * Dave Hansen <haveblue@us.ibm.com>
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 * Christoph Lameter
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 */

#include <linux/migrate.h>
#include <linux/module.h>
#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/memcontrol.h>
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#include <linux/syscalls.h>
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#include <linux/hugetlb.h>
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#include <linux/gfp.h>
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#include "internal.h"

#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))

/*
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 * migrate_prep() needs to be called before we start compiling a list of pages
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 * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
 * undesirable, use migrate_prep_local()
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 */
int migrate_prep(void)
{
	/*
	 * Clear the LRU lists so pages can be isolated.
	 * Note that pages may be moved off the LRU after we have
	 * drained them. Those pages will fail to migrate like other
	 * pages that may be busy.
	 */
	lru_add_drain_all();

	return 0;
}

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/* Do the necessary work of migrate_prep but not if it involves other CPUs */
int migrate_prep_local(void)
{
	lru_add_drain();

	return 0;
}

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/*
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 * Add isolated pages on the list back to the LRU under page lock
 * to avoid leaking evictable pages back onto unevictable list.
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 */
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void putback_lru_pages(struct list_head *l)
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{
	struct page *page;
	struct page *page2;

	list_for_each_entry_safe(page, page2, l, lru) {
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		list_del(&page->lru);
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		dec_zone_page_state(page, NR_ISOLATED_ANON +
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				page_is_file_cache(page));
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		putback_lru_page(page);
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	}
}

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/*
 * Restore a potential migration pte to a working pte entry
 */
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static int remove_migration_pte(struct page *new, struct vm_area_struct *vma,
				 unsigned long addr, void *old)
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{
	struct mm_struct *mm = vma->vm_mm;
	swp_entry_t entry;
 	pgd_t *pgd;
 	pud_t *pud;
 	pmd_t *pmd;
	pte_t *ptep, pte;
 	spinlock_t *ptl;

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	if (unlikely(PageHuge(new))) {
		ptep = huge_pte_offset(mm, addr);
		if (!ptep)
			goto out;
		ptl = &mm->page_table_lock;
	} else {
		pgd = pgd_offset(mm, addr);
		if (!pgd_present(*pgd))
			goto out;
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		pud = pud_offset(pgd, addr);
		if (!pud_present(*pud))
			goto out;
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		pmd = pmd_offset(pud, addr);
		if (!pmd_present(*pmd))
			goto out;
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		ptep = pte_offset_map(pmd, addr);
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		if (!is_swap_pte(*ptep)) {
			pte_unmap(ptep);
			goto out;
		}

		ptl = pte_lockptr(mm, pmd);
	}
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 	spin_lock(ptl);
	pte = *ptep;
	if (!is_swap_pte(pte))
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		goto unlock;
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	entry = pte_to_swp_entry(pte);

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	if (!is_migration_entry(entry) ||
	    migration_entry_to_page(entry) != old)
		goto unlock;
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	get_page(new);
	pte = pte_mkold(mk_pte(new, vma->vm_page_prot));
	if (is_write_migration_entry(entry))
		pte = pte_mkwrite(pte);
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#ifdef CONFIG_HUGETLB_PAGE
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	if (PageHuge(new))
		pte = pte_mkhuge(pte);
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#endif
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	flush_cache_page(vma, addr, pte_pfn(pte));
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	set_pte_at(mm, addr, ptep, pte);
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	if (PageHuge(new)) {
		if (PageAnon(new))
			hugepage_add_anon_rmap(new, vma, addr);
		else
			page_dup_rmap(new);
	} else if (PageAnon(new))
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		page_add_anon_rmap(new, vma, addr);
	else
		page_add_file_rmap(new);

	/* No need to invalidate - it was non-present before */
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	update_mmu_cache(vma, addr, ptep);
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unlock:
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	pte_unmap_unlock(ptep, ptl);
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out:
	return SWAP_AGAIN;
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}

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/*
 * Get rid of all migration entries and replace them by
 * references to the indicated page.
 */
static void remove_migration_ptes(struct page *old, struct page *new)
{
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	rmap_walk(new, remove_migration_pte, old);
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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.
 *
 * This function is called from do_swap_page().
 */
void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
				unsigned long address)
{
	pte_t *ptep, pte;
	spinlock_t *ptl;
	swp_entry_t entry;
	struct page *page;

	ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
	pte = *ptep;
	if (!is_swap_pte(pte))
		goto out;

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

	page = migration_entry_to_page(entry);

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	/*
	 * Once radix-tree replacement of page migration started, page_count
	 * *must* be zero. And, we don't want to call wait_on_page_locked()
	 * against a page without get_page().
	 * So, we use get_page_unless_zero(), here. Even failed, page fault
	 * will occur again.
	 */
	if (!get_page_unless_zero(page))
		goto out;
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	pte_unmap_unlock(ptep, ptl);
	wait_on_page_locked(page);
	put_page(page);
	return;
out:
	pte_unmap_unlock(ptep, ptl);
}

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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.
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 */
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static int migrate_page_move_mapping(struct address_space *mapping,
		struct page *newpage, struct page *page)
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{
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	int expected_count;
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	void **pslot;
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	if (!mapping) {
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		/* Anonymous page without mapping */
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		if (page_count(page) != 1)
			return -EAGAIN;
		return 0;
	}

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	spin_lock_irq(&mapping->tree_lock);
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	pslot = radix_tree_lookup_slot(&mapping->page_tree,
 					page_index(page));
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	expected_count = 2 + page_has_private(page);
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	if (page_count(page) != expected_count ||
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			(struct page *)radix_tree_deref_slot(pslot) != page) {
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		spin_unlock_irq(&mapping->tree_lock);
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		return -EAGAIN;
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	}

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	if (!page_freeze_refs(page, expected_count)) {
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		spin_unlock_irq(&mapping->tree_lock);
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		return -EAGAIN;
	}

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	/*
	 * Now we know that no one else is looking at the page.
	 */
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	get_page(newpage);	/* add cache reference */
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	if (PageSwapCache(page)) {
		SetPageSwapCache(newpage);
		set_page_private(newpage, page_private(page));
	}

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	radix_tree_replace_slot(pslot, newpage);

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	page_unfreeze_refs(page, expected_count);
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	/*
	 * Drop cache reference from old page.
	 * We know this isn't the last reference.
	 */
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	__put_page(page);
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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
	 * via NR_FILE_PAGES and NR_ANON_PAGES if they
	 * are mapped to swap space.
	 */
	__dec_zone_page_state(page, NR_FILE_PAGES);
	__inc_zone_page_state(newpage, NR_FILE_PAGES);
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	if (PageSwapBacked(page)) {
		__dec_zone_page_state(page, NR_SHMEM);
		__inc_zone_page_state(newpage, NR_SHMEM);
	}
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	spin_unlock_irq(&mapping->tree_lock);
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	return 0;
}

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/*
 * The expected number of remaining references is the same as that
 * of migrate_page_move_mapping().
 */
int migrate_huge_page_move_mapping(struct address_space *mapping,
				   struct page *newpage, struct page *page)
{
	int expected_count;
	void **pslot;

	if (!mapping) {
		if (page_count(page) != 1)
			return -EAGAIN;
		return 0;
	}

	spin_lock_irq(&mapping->tree_lock);

	pslot = radix_tree_lookup_slot(&mapping->page_tree,
					page_index(page));

	expected_count = 2 + page_has_private(page);
	if (page_count(page) != expected_count ||
	    (struct page *)radix_tree_deref_slot(pslot) != page) {
		spin_unlock_irq(&mapping->tree_lock);
		return -EAGAIN;
	}

	if (!page_freeze_refs(page, expected_count)) {
		spin_unlock_irq(&mapping->tree_lock);
		return -EAGAIN;
	}

	get_page(newpage);

	radix_tree_replace_slot(pslot, newpage);

	page_unfreeze_refs(page, expected_count);

	__put_page(page);

	spin_unlock_irq(&mapping->tree_lock);
	return 0;
}

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/*
 * Copy the page to its new location
 */
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void migrate_page_copy(struct page *newpage, struct page *page)
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{
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	if (PageHuge(page))
		copy_huge_page(newpage, page);
	else
		copy_highpage(newpage, page);
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	if (PageError(page))
		SetPageError(newpage);
	if (PageReferenced(page))
		SetPageReferenced(newpage);
	if (PageUptodate(page))
		SetPageUptodate(newpage);
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	if (TestClearPageActive(page)) {
		VM_BUG_ON(PageUnevictable(page));
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		SetPageActive(newpage);
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	} else if (TestClearPageUnevictable(page))
		SetPageUnevictable(newpage);
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	if (PageChecked(page))
		SetPageChecked(newpage);
	if (PageMappedToDisk(page))
		SetPageMappedToDisk(newpage);

	if (PageDirty(page)) {
		clear_page_dirty_for_io(page);
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		/*
		 * Want to mark the page and the radix tree as dirty, and
		 * redo the accounting that clear_page_dirty_for_io undid,
		 * but we can't use set_page_dirty because that function
		 * is actually a signal that all of the page has become dirty.
		 * Wheras only part of our page may be dirty.
		 */
		__set_page_dirty_nobuffers(newpage);
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 	}

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	mlock_migrate_page(newpage, page);
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	ksm_migrate_page(newpage, page);
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	ClearPageSwapCache(page);
	ClearPagePrivate(page);
	set_page_private(page, 0);
	page->mapping = NULL;

	/*
	 * If any waiters have accumulated on the new page then
	 * wake them up.
	 */
	if (PageWriteback(newpage))
		end_page_writeback(newpage);
}

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

/* Always fail migration. Used for mappings that are not movable */
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int fail_migrate_page(struct address_space *mapping,
			struct page *newpage, struct page *page)
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{
	return -EIO;
}
EXPORT_SYMBOL(fail_migrate_page);

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/*
 * Common logic to directly migrate a single page suitable for
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 * pages that do not use PagePrivate/PagePrivate2.
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 *
 * Pages are locked upon entry and exit.
 */
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int migrate_page(struct address_space *mapping,
		struct page *newpage, struct page *page)
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{
	int rc;

	BUG_ON(PageWriteback(page));	/* Writeback must be complete */

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	rc = migrate_page_move_mapping(mapping, newpage, page);
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	if (rc)
		return rc;

	migrate_page_copy(newpage, page);
	return 0;
}
EXPORT_SYMBOL(migrate_page);

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#ifdef CONFIG_BLOCK
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/*
 * Migration function for pages with buffers. This function can only be used
 * if the underlying filesystem guarantees that no other references to "page"
 * exist.
 */
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int buffer_migrate_page(struct address_space *mapping,
		struct page *newpage, struct page *page)
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{
	struct buffer_head *bh, *head;
	int rc;

	if (!page_has_buffers(page))
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		return migrate_page(mapping, newpage, page);
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	head = page_buffers(page);

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	rc = migrate_page_move_mapping(mapping, newpage, page);
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	if (rc)
		return rc;

	bh = head;
	do {
		get_bh(bh);
		lock_buffer(bh);
		bh = bh->b_this_page;

	} while (bh != head);

	ClearPagePrivate(page);
	set_page_private(newpage, page_private(page));
	set_page_private(page, 0);
	put_page(page);
	get_page(newpage);

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

	} while (bh != head);

	SetPagePrivate(newpage);

	migrate_page_copy(newpage, page);

	bh = head;
	do {
		unlock_buffer(bh);
 		put_bh(bh);
		bh = bh->b_this_page;

	} while (bh != head);

	return 0;
}
EXPORT_SYMBOL(buffer_migrate_page);
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#endif
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/*
 * Writeback a page to clean the dirty state
 */
static int writeout(struct address_space *mapping, struct page *page)
494
{
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	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;

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	/*
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	 * 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.
519
	 */
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	remove_migration_ptes(page, page);
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522
	rc = mapping->a_ops->writepage(page, &wbc);
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	if (rc != AOP_WRITEPAGE_ACTIVATE)
		/* unlocked. Relock */
		lock_page(page);

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	return (rc < 0) ? -EIO : -EAGAIN;
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}

/*
 * Default handling if a filesystem does not provide a migration function.
 */
static int fallback_migrate_page(struct address_space *mapping,
	struct page *newpage, struct page *page)
{
	if (PageDirty(page))
		return writeout(mapping, page);
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	/*
	 * Buffers may be managed in a filesystem specific way.
	 * We must have no buffers or drop them.
	 */
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	if (page_has_private(page) &&
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	    !try_to_release_page(page, GFP_KERNEL))
		return -EAGAIN;

	return migrate_page(mapping, newpage, page);
}

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/*
 * 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.
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 *
 * Return value:
 *   < 0 - error code
 *  == 0 - success
561
 */
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static int move_to_new_page(struct page *newpage, struct page *page,
						int remap_swapcache)
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{
	struct address_space *mapping;
	int rc;

	/*
	 * Block others from accessing the page when we get around to
	 * establishing additional references. We are the only one
	 * holding a reference to the new page at this point.
	 */
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	if (!trylock_page(newpage))
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		BUG();

	/* Prepare mapping for the new page.*/
	newpage->index = page->index;
	newpage->mapping = page->mapping;
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	if (PageSwapBacked(page))
		SetPageSwapBacked(newpage);
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	mapping = page_mapping(page);
	if (!mapping)
		rc = migrate_page(mapping, newpage, page);
	else if (mapping->a_ops->migratepage)
		/*
		 * Most pages have a mapping and most filesystems
		 * should provide a migration function. Anonymous
		 * pages are part of swap space which also has its
		 * own migration function. This is the most common
		 * path for page migration.
		 */
		rc = mapping->a_ops->migratepage(mapping,
						newpage, page);
	else
		rc = fallback_migrate_page(mapping, newpage, page);

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	if (rc) {
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		newpage->mapping = NULL;
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	} else {
		if (remap_swapcache)
			remove_migration_ptes(page, newpage);
	}
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	unlock_page(newpage);

	return rc;
}

/*
 * Obtain the lock on page, remove all ptes and migrate the page
 * to the newly allocated page in newpage.
 */
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static int unmap_and_move(new_page_t get_new_page, unsigned long private,
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			struct page *page, int force, int offlining)
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{
	int rc = 0;
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	int *result = NULL;
	struct page *newpage = get_new_page(page, private, &result);
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	int remap_swapcache = 1;
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	int rcu_locked = 0;
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	int charge = 0;
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	struct mem_cgroup *mem = NULL;
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	struct anon_vma *anon_vma = NULL;
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	if (!newpage)
		return -ENOMEM;
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	if (page_count(page) == 1) {
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		/* page was freed from under us. So we are done. */
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		goto move_newpage;
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	}
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	/* prepare cgroup just returns 0 or -ENOMEM */
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	rc = -EAGAIN;
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	if (!trylock_page(page)) {
638
		if (!force)
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			goto move_newpage;
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		lock_page(page);
	}

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	/*
	 * Only memory hotplug's offline_pages() caller has locked out KSM,
	 * and can safely migrate a KSM page.  The other cases have skipped
	 * PageKsm along with PageReserved - but it is only now when we have
	 * the page lock that we can be certain it will not go KSM beneath us
	 * (KSM will not upgrade a page from PageAnon to PageKsm when it sees
	 * its pagecount raised, but only here do we take the page lock which
	 * serializes that).
	 */
	if (PageKsm(page) && !offlining) {
		rc = -EBUSY;
		goto unlock;
	}

657
	/* charge against new page */
658
	charge = mem_cgroup_prepare_migration(page, newpage, &mem);
659 660 661 662 663 664
	if (charge == -ENOMEM) {
		rc = -ENOMEM;
		goto unlock;
	}
	BUG_ON(charge);

665 666
	if (PageWriteback(page)) {
		if (!force)
667
			goto uncharge;
668 669 670
		wait_on_page_writeback(page);
	}
	/*
671 672 673 674
	 * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
	 * we cannot notice that anon_vma is freed while we migrates a page.
	 * This rcu_read_lock() delays freeing anon_vma pointer until the end
	 * of migration. File cache pages are no problem because of page_lock()
675 676
	 * File Caches may use write_page() or lock_page() in migration, then,
	 * just care Anon page here.
677
	 */
678 679 680
	if (PageAnon(page)) {
		rcu_read_lock();
		rcu_locked = 1;
681

682 683 684 685
		/* Determine how to safely use anon_vma */
		if (!page_mapped(page)) {
			if (!PageSwapCache(page))
				goto rcu_unlock;
686

687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706
			/*
			 * We cannot be sure that the anon_vma of an unmapped
			 * swapcache page is safe to use because we don't
			 * know in advance if the VMA that this page belonged
			 * to still exists. If the VMA and others sharing the
			 * data have been freed, then the anon_vma could
			 * already be invalid.
			 *
			 * To avoid this possibility, swapcache pages get
			 * migrated but are not remapped when migration
			 * completes
			 */
			remap_swapcache = 0;
		} else {
			/*
			 * Take a reference count on the anon_vma if the
			 * page is mapped so that it is guaranteed to
			 * exist when the page is remapped later
			 */
			anon_vma = page_anon_vma(page);
707
			get_anon_vma(anon_vma);
708
		}
709
	}
710

711
	/*
712 713 714 715 716 717 718 719 720 721
	 * Corner case handling:
	 * 1. When a new swap-cache page is read into, it is added to the LRU
	 * and treated as swapcache but it has no rmap yet.
	 * Calling try_to_unmap() against a page->mapping==NULL page will
	 * trigger a BUG.  So handle it here.
	 * 2. An orphaned page (see truncate_complete_page) might have
	 * fs-private metadata. The page can be picked up due to memory
	 * offlining.  Everywhere else except page reclaim, the page is
	 * invisible to the vm, so the page can not be migrated.  So try to
	 * free the metadata, so the page can be freed.
722
	 */
723
	if (!page->mapping) {
724
		if (!PageAnon(page) && page_has_private(page)) {
725 726 727 728 729 730 731 732
			/*
			 * Go direct to try_to_free_buffers() here because
			 * a) that's what try_to_release_page() would do anyway
			 * b) we may be under rcu_read_lock() here, so we can't
			 *    use GFP_KERNEL which is what try_to_release_page()
			 *    needs to be effective.
			 */
			try_to_free_buffers(page);
733
			goto rcu_unlock;
734
		}
735
		goto skip_unmap;
736 737
	}

738
	/* Establish migration ptes or remove ptes */
739
	try_to_unmap(page, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
740

741
skip_unmap:
742
	if (!page_mapped(page))
743
		rc = move_to_new_page(newpage, page, remap_swapcache);
744

745
	if (rc && remap_swapcache)
746
		remove_migration_ptes(page, page);
747
rcu_unlock:
748 749

	/* Drop an anon_vma reference if we took one */
750 751
	if (anon_vma)
		drop_anon_vma(anon_vma);
752

753 754
	if (rcu_locked)
		rcu_read_unlock();
755 756 757
uncharge:
	if (!charge)
		mem_cgroup_end_migration(mem, page, newpage);
758 759
unlock:
	unlock_page(page);
760

761
	if (rc != -EAGAIN) {
762 763 764 765 766 767 768
 		/*
 		 * A page that has been migrated has all references
 		 * removed and will be freed. A page that has not been
 		 * migrated will have kepts its references and be
 		 * restored.
 		 */
 		list_del(&page->lru);
K
KOSAKI Motohiro 已提交
769
		dec_zone_page_state(page, NR_ISOLATED_ANON +
770
				page_is_file_cache(page));
L
Lee Schermerhorn 已提交
771
		putback_lru_page(page);
772
	}
773 774

move_newpage:
L
Lee Schermerhorn 已提交
775

776 777 778 779
	/*
	 * Move the new page to the LRU. If migration was not successful
	 * then this will free the page.
	 */
L
Lee Schermerhorn 已提交
780 781
	putback_lru_page(newpage);

782 783 784 785 786 787
	if (result) {
		if (rc)
			*result = rc;
		else
			*result = page_to_nid(newpage);
	}
788 789 790
	return rc;
}

N
Naoya Horiguchi 已提交
791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876
/*
 * 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,
				unsigned long private, struct page *hpage,
				int force, int offlining)
{
	int rc = 0;
	int *result = NULL;
	struct page *new_hpage = get_new_page(hpage, private, &result);
	int rcu_locked = 0;
	struct anon_vma *anon_vma = NULL;

	if (!new_hpage)
		return -ENOMEM;

	rc = -EAGAIN;

	if (!trylock_page(hpage)) {
		if (!force)
			goto out;
		lock_page(hpage);
	}

	if (PageAnon(hpage)) {
		rcu_read_lock();
		rcu_locked = 1;

		if (page_mapped(hpage)) {
			anon_vma = page_anon_vma(hpage);
			atomic_inc(&anon_vma->external_refcount);
		}
	}

	try_to_unmap(hpage, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);

	if (!page_mapped(hpage))
		rc = move_to_new_page(new_hpage, hpage, 1);

	if (rc)
		remove_migration_ptes(hpage, hpage);

	if (anon_vma && atomic_dec_and_lock(&anon_vma->external_refcount,
					    &anon_vma->lock)) {
		int empty = list_empty(&anon_vma->head);
		spin_unlock(&anon_vma->lock);
		if (empty)
			anon_vma_free(anon_vma);
	}

	if (rcu_locked)
		rcu_read_unlock();
out:
	unlock_page(hpage);

	if (rc != -EAGAIN) {
		list_del(&hpage->lru);
		put_page(hpage);
	}

	put_page(new_hpage);

	if (result) {
		if (rc)
			*result = rc;
		else
			*result = page_to_nid(new_hpage);
	}
	return rc;
}

C
Christoph Lameter 已提交
877 878 879
/*
 * migrate_pages
 *
880 881 882
 * The function takes one list of pages to migrate and a function
 * that determines from the page to be migrated and the private data
 * the target of the move and allocates the page.
C
Christoph Lameter 已提交
883 884 885
 *
 * The function returns after 10 attempts or if no pages
 * are movable anymore because to has become empty
886
 * or no retryable pages exist anymore. All pages will be
G
Gabriel Craciunescu 已提交
887
 * returned to the LRU or freed.
C
Christoph Lameter 已提交
888
 *
889
 * Return: Number of pages not migrated or error code.
C
Christoph Lameter 已提交
890
 */
891
int migrate_pages(struct list_head *from,
892
		new_page_t get_new_page, unsigned long private, int offlining)
C
Christoph Lameter 已提交
893
{
894
	int retry = 1;
C
Christoph Lameter 已提交
895 896 897 898 899 900 901 902 903 904
	int nr_failed = 0;
	int pass = 0;
	struct page *page;
	struct page *page2;
	int swapwrite = current->flags & PF_SWAPWRITE;
	int rc;

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

905 906
	for(pass = 0; pass < 10 && retry; pass++) {
		retry = 0;
C
Christoph Lameter 已提交
907

908 909
		list_for_each_entry_safe(page, page2, from, lru) {
			cond_resched();
910

911
			rc = unmap_and_move(get_new_page, private,
912
						page, pass > 2, offlining);
913

914
			switch(rc) {
915 916
			case -ENOMEM:
				goto out;
917
			case -EAGAIN:
918
				retry++;
919 920 921 922
				break;
			case 0:
				break;
			default:
923 924
				/* Permanent failure */
				nr_failed++;
925
				break;
926
			}
C
Christoph Lameter 已提交
927 928
		}
	}
929 930
	rc = 0;
out:
C
Christoph Lameter 已提交
931 932 933
	if (!swapwrite)
		current->flags &= ~PF_SWAPWRITE;

934
	putback_lru_pages(from);
C
Christoph Lameter 已提交
935

936 937
	if (rc)
		return rc;
C
Christoph Lameter 已提交
938

939
	return nr_failed + retry;
C
Christoph Lameter 已提交
940
}
941

N
Naoya Horiguchi 已提交
942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987
int migrate_huge_pages(struct list_head *from,
		new_page_t get_new_page, unsigned long private, int offlining)
{
	int retry = 1;
	int nr_failed = 0;
	int pass = 0;
	struct page *page;
	struct page *page2;
	int rc;

	for (pass = 0; pass < 10 && retry; pass++) {
		retry = 0;

		list_for_each_entry_safe(page, page2, from, lru) {
			cond_resched();

			rc = unmap_and_move_huge_page(get_new_page,
					private, page, pass > 2, offlining);

			switch(rc) {
			case -ENOMEM:
				goto out;
			case -EAGAIN:
				retry++;
				break;
			case 0:
				break;
			default:
				/* Permanent failure */
				nr_failed++;
				break;
			}
		}
	}
	rc = 0;
out:

	list_for_each_entry_safe(page, page2, from, lru)
		put_page(page);

	if (rc)
		return rc;

	return nr_failed + retry;
}

988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011
#ifdef CONFIG_NUMA
/*
 * Move a list of individual pages
 */
struct page_to_node {
	unsigned long addr;
	struct page *page;
	int node;
	int status;
};

static struct page *new_page_node(struct page *p, unsigned long private,
		int **result)
{
	struct page_to_node *pm = (struct page_to_node *)private;

	while (pm->node != MAX_NUMNODES && pm->page != p)
		pm++;

	if (pm->node == MAX_NUMNODES)
		return NULL;

	*result = &pm->status;

1012
	return alloc_pages_exact_node(pm->node,
1013
				GFP_HIGHUSER_MOVABLE | GFP_THISNODE, 0);
1014 1015 1016 1017 1018 1019
}

/*
 * Move a set of pages as indicated in the pm array. The addr
 * field must be set to the virtual address of the page to be moved
 * and the node number must contain a valid target node.
1020
 * The pm array ends with node = MAX_NUMNODES.
1021
 */
1022 1023 1024
static int do_move_page_to_node_array(struct mm_struct *mm,
				      struct page_to_node *pm,
				      int migrate_all)
1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040
{
	int err;
	struct page_to_node *pp;
	LIST_HEAD(pagelist);

	down_read(&mm->mmap_sem);

	/*
	 * Build a list of pages to migrate
	 */
	for (pp = pm; pp->node != MAX_NUMNODES; pp++) {
		struct vm_area_struct *vma;
		struct page *page;

		err = -EFAULT;
		vma = find_vma(mm, pp->addr);
1041
		if (!vma || !vma_migratable(vma))
1042 1043 1044
			goto set_status;

		page = follow_page(vma, pp->addr, FOLL_GET);
1045 1046 1047 1048 1049

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

1050 1051 1052 1053
		err = -ENOENT;
		if (!page)
			goto set_status;

1054 1055
		/* Use PageReserved to check for zero page */
		if (PageReserved(page) || PageKsm(page))
1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071
			goto put_and_set;

		pp->page = page;
		err = page_to_nid(page);

		if (err == pp->node)
			/*
			 * Node already in the right place
			 */
			goto put_and_set;

		err = -EACCES;
		if (page_mapcount(page) > 1 &&
				!migrate_all)
			goto put_and_set;

1072
		err = isolate_lru_page(page);
1073
		if (!err) {
1074
			list_add_tail(&page->lru, &pagelist);
1075 1076 1077
			inc_zone_page_state(page, NR_ISOLATED_ANON +
					    page_is_file_cache(page));
		}
1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088
put_and_set:
		/*
		 * Either remove the duplicate refcount from
		 * isolate_lru_page() or drop the page ref if it was
		 * not isolated.
		 */
		put_page(page);
set_status:
		pp->status = err;
	}

1089
	err = 0;
1090 1091
	if (!list_empty(&pagelist))
		err = migrate_pages(&pagelist, new_page_node,
1092
				(unsigned long)pm, 0);
1093 1094 1095 1096 1097

	up_read(&mm->mmap_sem);
	return err;
}

1098 1099 1100 1101 1102 1103 1104 1105 1106 1107
/*
 * Migrate an array of page address onto an array of nodes and fill
 * the corresponding array of status.
 */
static int do_pages_move(struct mm_struct *mm, struct task_struct *task,
			 unsigned long nr_pages,
			 const void __user * __user *pages,
			 const int __user *nodes,
			 int __user *status, int flags)
{
1108
	struct page_to_node *pm;
1109
	nodemask_t task_nodes;
1110 1111 1112
	unsigned long chunk_nr_pages;
	unsigned long chunk_start;
	int err;
1113 1114 1115

	task_nodes = cpuset_mems_allowed(task);

1116 1117 1118
	err = -ENOMEM;
	pm = (struct page_to_node *)__get_free_page(GFP_KERNEL);
	if (!pm)
1119
		goto out;
1120 1121 1122

	migrate_prep();

1123
	/*
1124 1125
	 * Store a chunk of page_to_node array in a page,
	 * but keep the last one as a marker
1126
	 */
1127
	chunk_nr_pages = (PAGE_SIZE / sizeof(struct page_to_node)) - 1;
1128

1129 1130 1131 1132
	for (chunk_start = 0;
	     chunk_start < nr_pages;
	     chunk_start += chunk_nr_pages) {
		int j;
1133

1134 1135 1136 1137 1138 1139
		if (chunk_start + chunk_nr_pages > nr_pages)
			chunk_nr_pages = nr_pages - chunk_start;

		/* fill the chunk pm with addrs and nodes from user-space */
		for (j = 0; j < chunk_nr_pages; j++) {
			const void __user *p;
1140 1141
			int node;

1142 1143 1144 1145 1146 1147
			err = -EFAULT;
			if (get_user(p, pages + j + chunk_start))
				goto out_pm;
			pm[j].addr = (unsigned long) p;

			if (get_user(node, nodes + j + chunk_start))
1148 1149 1150
				goto out_pm;

			err = -ENODEV;
1151 1152 1153
			if (node < 0 || node >= MAX_NUMNODES)
				goto out_pm;

1154 1155 1156 1157 1158 1159 1160
			if (!node_state(node, N_HIGH_MEMORY))
				goto out_pm;

			err = -EACCES;
			if (!node_isset(node, task_nodes))
				goto out_pm;

1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171
			pm[j].node = node;
		}

		/* End marker for this chunk */
		pm[chunk_nr_pages].node = MAX_NUMNODES;

		/* Migrate this chunk */
		err = do_move_page_to_node_array(mm, pm,
						 flags & MPOL_MF_MOVE_ALL);
		if (err < 0)
			goto out_pm;
1172 1173

		/* Return status information */
1174 1175
		for (j = 0; j < chunk_nr_pages; j++)
			if (put_user(pm[j].status, status + j + chunk_start)) {
1176
				err = -EFAULT;
1177 1178 1179 1180
				goto out_pm;
			}
	}
	err = 0;
1181 1182

out_pm:
1183
	free_page((unsigned long)pm);
1184 1185 1186 1187
out:
	return err;
}

1188
/*
1189
 * Determine the nodes of an array of pages and store it in an array of status.
1190
 */
1191 1192
static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
				const void __user **pages, int *status)
1193
{
1194 1195
	unsigned long i;

1196 1197
	down_read(&mm->mmap_sem);

1198
	for (i = 0; i < nr_pages; i++) {
1199
		unsigned long addr = (unsigned long)(*pages);
1200 1201
		struct vm_area_struct *vma;
		struct page *page;
1202
		int err = -EFAULT;
1203 1204

		vma = find_vma(mm, addr);
1205 1206 1207
		if (!vma)
			goto set_status;

1208
		page = follow_page(vma, addr, 0);
1209 1210 1211 1212 1213

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

1214 1215
		err = -ENOENT;
		/* Use PageReserved to check for zero page */
1216
		if (!page || PageReserved(page) || PageKsm(page))
1217 1218 1219 1220
			goto set_status;

		err = page_to_nid(page);
set_status:
1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241
		*status = err;

		pages++;
		status++;
	}

	up_read(&mm->mmap_sem);
}

/*
 * 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];

1242 1243
	while (nr_pages) {
		unsigned long chunk_nr;
1244

1245 1246 1247 1248 1249 1250
		chunk_nr = nr_pages;
		if (chunk_nr > DO_PAGES_STAT_CHUNK_NR)
			chunk_nr = DO_PAGES_STAT_CHUNK_NR;

		if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages)))
			break;
1251 1252 1253

		do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);

1254 1255
		if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
			break;
1256

1257 1258 1259 1260 1261
		pages += chunk_nr;
		status += chunk_nr;
		nr_pages -= chunk_nr;
	}
	return nr_pages ? -EFAULT : 0;
1262 1263 1264 1265 1266 1267
}

/*
 * Move a list of pages in the address space of the currently executing
 * process.
 */
1268 1269 1270 1271
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)
1272
{
1273
	const struct cred *cred = current_cred(), *tcred;
1274 1275
	struct task_struct *task;
	struct mm_struct *mm;
1276
	int err;
1277 1278 1279 1280 1281 1282 1283 1284 1285 1286

	/* Check flags */
	if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
		return -EINVAL;

	if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
		return -EPERM;

	/* Find the mm_struct */
	read_lock(&tasklist_lock);
1287
	task = pid ? find_task_by_vpid(pid) : current;
1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303
	if (!task) {
		read_unlock(&tasklist_lock);
		return -ESRCH;
	}
	mm = get_task_mm(task);
	read_unlock(&tasklist_lock);

	if (!mm)
		return -EINVAL;

	/*
	 * Check if this process has the right to modify the specified
	 * process. The right exists if the process has administrative
	 * capabilities, superuser privileges or the same
	 * userid as the target process.
	 */
1304 1305
	rcu_read_lock();
	tcred = __task_cred(task);
1306 1307
	if (cred->euid != tcred->suid && cred->euid != tcred->uid &&
	    cred->uid  != tcred->suid && cred->uid  != tcred->uid &&
1308
	    !capable(CAP_SYS_NICE)) {
1309
		rcu_read_unlock();
1310
		err = -EPERM;
1311
		goto out;
1312
	}
1313
	rcu_read_unlock();
1314

1315 1316
 	err = security_task_movememory(task);
 	if (err)
1317
		goto out;
1318

1319 1320 1321 1322
	if (nodes) {
		err = do_pages_move(mm, task, nr_pages, pages, nodes, status,
				    flags);
	} else {
1323
		err = do_pages_stat(mm, nr_pages, pages, status);
1324 1325 1326 1327 1328 1329 1330
	}

out:
	mmput(mm);
	return err;
}

1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341
/*
 * Call migration functions in the vma_ops that may prepare
 * memory in a vm for migration. migration functions may perform
 * the migration for vmas that do not have an underlying page struct.
 */
int migrate_vmas(struct mm_struct *mm, const nodemask_t *to,
	const nodemask_t *from, unsigned long flags)
{
 	struct vm_area_struct *vma;
 	int err = 0;

1342
	for (vma = mm->mmap; vma && !err; vma = vma->vm_next) {
1343 1344 1345 1346 1347 1348 1349 1350
 		if (vma->vm_ops && vma->vm_ops->migrate) {
 			err = vma->vm_ops->migrate(vma, to, from, flags);
 			if (err)
 				break;
 		}
 	}
 	return err;
}
1351
#endif