migrate.c 23.4 KB
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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>
 * Christoph Lameter <clameter@sgi.com>
 */

#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>
#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 "internal.h"

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

/*
 * Isolate one page from the LRU lists. If successful put it onto
 * the indicated list with elevated page count.
 *
 * Result:
 *  -EBUSY: page not on LRU list
 *  0: page removed from LRU list and added to the specified list.
 */
int isolate_lru_page(struct page *page, struct list_head *pagelist)
{
	int ret = -EBUSY;

	if (PageLRU(page)) {
		struct zone *zone = page_zone(page);

		spin_lock_irq(&zone->lru_lock);
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		if (PageLRU(page) && get_page_unless_zero(page)) {
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			ret = 0;
			ClearPageLRU(page);
			if (PageActive(page))
				del_page_from_active_list(zone, page);
			else
				del_page_from_inactive_list(zone, page);
			list_add_tail(&page->lru, pagelist);
		}
		spin_unlock_irq(&zone->lru_lock);
	}
	return ret;
}

/*
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 * migrate_prep() needs to be called before we start compiling a list of pages
 * to be migrated using isolate_lru_page().
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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;
}

static inline void move_to_lru(struct page *page)
{
	if (PageActive(page)) {
		/*
		 * lru_cache_add_active checks that
		 * the PG_active bit is off.
		 */
		ClearPageActive(page);
		lru_cache_add_active(page);
	} else {
		lru_cache_add(page);
	}
	put_page(page);
}

/*
 * Add isolated pages on the list back to the LRU.
 *
 * returns the number of pages put back.
 */
int putback_lru_pages(struct list_head *l)
{
	struct page *page;
	struct page *page2;
	int count = 0;

	list_for_each_entry_safe(page, page2, l, lru) {
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		list_del(&page->lru);
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		move_to_lru(page);
		count++;
	}
	return count;
}

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/*
 * Restore a potential migration pte to a working pte entry
 */
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static void remove_migration_pte(struct vm_area_struct *vma,
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		struct page *old, struct page *new)
{
	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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	unsigned long addr = page_address_in_vma(new, vma);

	if (addr == -EFAULT)
		return;
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 	pgd = pgd_offset(mm, addr);
	if (!pgd_present(*pgd))
                return;

	pud = pud_offset(pgd, addr);
	if (!pud_present(*pud))
                return;

	pmd = pmd_offset(pud, addr);
	if (!pmd_present(*pmd))
		return;

	ptep = pte_offset_map(pmd, addr);

	if (!is_swap_pte(*ptep)) {
		pte_unmap(ptep);
 		return;
 	}

 	ptl = pte_lockptr(mm, pmd);
 	spin_lock(ptl);
	pte = *ptep;
	if (!is_swap_pte(pte))
		goto out;

	entry = pte_to_swp_entry(pte);

	if (!is_migration_entry(entry) || migration_entry_to_page(entry) != old)
		goto out;

	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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	flush_cache_page(vma, addr, pte_pfn(pte));
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	set_pte_at(mm, addr, ptep, pte);
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	if (PageAnon(new))
		page_add_anon_rmap(new, vma, addr);
	else
		page_add_file_rmap(new);

	/* No need to invalidate - it was non-present before */
	update_mmu_cache(vma, addr, pte);

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out:
	pte_unmap_unlock(ptep, ptl);
}

/*
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 * Note that remove_file_migration_ptes will only work on regular mappings,
 * Nonlinear mappings do not use migration entries.
 */
static void remove_file_migration_ptes(struct page *old, struct page *new)
{
	struct vm_area_struct *vma;
	struct address_space *mapping = page_mapping(new);
	struct prio_tree_iter iter;
	pgoff_t pgoff = new->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);

	if (!mapping)
		return;

	spin_lock(&mapping->i_mmap_lock);

	vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff)
		remove_migration_pte(vma, old, new);

	spin_unlock(&mapping->i_mmap_lock);
}

/*
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 * Must hold mmap_sem lock on at least one of the vmas containing
 * the page so that the anon_vma cannot vanish.
 */
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static void remove_anon_migration_ptes(struct page *old, struct page *new)
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{
	struct anon_vma *anon_vma;
	struct vm_area_struct *vma;
	unsigned long mapping;

	mapping = (unsigned long)new->mapping;

	if (!mapping || (mapping & PAGE_MAPPING_ANON) == 0)
		return;

	/*
	 * We hold the mmap_sem lock. So no need to call page_lock_anon_vma.
	 */
	anon_vma = (struct anon_vma *) (mapping - PAGE_MAPPING_ANON);
	spin_lock(&anon_vma->lock);

	list_for_each_entry(vma, &anon_vma->head, anon_vma_node)
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		remove_migration_pte(vma, old, new);
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	spin_unlock(&anon_vma->lock);
}

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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)
{
	if (PageAnon(new))
		remove_anon_migration_ptes(old, new);
	else
		remove_file_migration_ptes(old, new);
}

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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);

	get_page(page);
	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
 * 3 for pages with a mapping and PagePrivate 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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	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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	write_lock_irq(&mapping->tree_lock);

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	pslot = radix_tree_lookup_slot(&mapping->page_tree,
 					page_index(page));
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	if (page_count(page) != 2 + !!PagePrivate(page) ||
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			(struct page *)radix_tree_deref_slot(pslot) != page) {
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		write_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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#ifdef CONFIG_SWAP
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	if (PageSwapCache(page)) {
		SetPageSwapCache(newpage);
		set_page_private(newpage, page_private(page));
	}
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#endif
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	radix_tree_replace_slot(pslot, newpage);

	/*
	 * 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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	write_unlock_irq(&mapping->tree_lock);

	return 0;
}

/*
 * Copy the page to its new location
 */
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static void migrate_page_copy(struct page *newpage, struct page *page)
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{
	copy_highpage(newpage, page);

	if (PageError(page))
		SetPageError(newpage);
	if (PageReferenced(page))
		SetPageReferenced(newpage);
	if (PageUptodate(page))
		SetPageUptodate(newpage);
	if (PageActive(page))
		SetPageActive(newpage);
	if (PageChecked(page))
		SetPageChecked(newpage);
	if (PageMappedToDisk(page))
		SetPageMappedToDisk(newpage);

	if (PageDirty(page)) {
		clear_page_dirty_for_io(page);
		set_page_dirty(newpage);
 	}

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#ifdef CONFIG_SWAP
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	ClearPageSwapCache(page);
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#endif
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	ClearPageActive(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
 * pages that do not use PagePrivate.
 *
 * 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)
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{
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	struct writeback_control wbc = {
		.sync_mode = WB_SYNC_NONE,
		.nr_to_write = 1,
		.range_start = 0,
		.range_end = LLONG_MAX,
		.nonblocking = 1,
		.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.
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	 */
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	remove_migration_ptes(page, page);
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	rc = mapping->a_ops->writepage(page, &wbc);
	if (rc < 0)
		/* I/O Error writing */
		return -EIO;
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	if (rc != AOP_WRITEPAGE_ACTIVATE)
		/* unlocked. Relock */
		lock_page(page);

	return -EAGAIN;
}

/*
 * Default handling if a filesystem does not provide a migration function.
 */
static int fallback_migrate_page(struct address_space *mapping,
	struct page *newpage, struct page *page)
{
	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 (PagePrivate(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.
 */
static int move_to_new_page(struct page *newpage, struct page *page)
{
	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.
	 */
	if (TestSetPageLocked(newpage))
		BUG();

	/* Prepare mapping for the new page.*/
	newpage->index = page->index;
	newpage->mapping = page->mapping;

	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);

	if (!rc)
		remove_migration_ptes(page, newpage);
	else
		newpage->mapping = NULL;

	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,
			struct page *page, int force)
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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 rcu_locked = 0;
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	if (!newpage)
		return -ENOMEM;
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	if (page_count(page) == 1)
		/* page was freed from under us. So we are done. */
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		goto move_newpage;
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	rc = -EAGAIN;
	if (TestSetPageLocked(page)) {
		if (!force)
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			goto move_newpage;
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		lock_page(page);
	}

	if (PageWriteback(page)) {
		if (!force)
			goto unlock;
		wait_on_page_writeback(page);
	}
	/*
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	 * 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()
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	 * File Caches may use write_page() or lock_page() in migration, then,
	 * just care Anon page here.
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	 */
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	if (PageAnon(page)) {
		rcu_read_lock();
		rcu_locked = 1;
	}
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	/*
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	 * 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.
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	 */
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	if (!page->mapping) {
		if (!PageAnon(page) && PagePrivate(page)) {
			/*
			 * 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);
		}
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		goto rcu_unlock;
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	}

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	/* Establish migration ptes or remove ptes */
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	try_to_unmap(page, 1);
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	if (!page_mapped(page))
		rc = move_to_new_page(newpage, page);
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	if (rc)
		remove_migration_ptes(page, page);
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rcu_unlock:
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	if (rcu_locked)
		rcu_read_unlock();
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unlock:
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	unlock_page(page);
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	if (rc != -EAGAIN) {
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 		/*
 		 * 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);
 		move_to_lru(page);
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	}
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move_newpage:
	/*
	 * Move the new page to the LRU. If migration was not successful
	 * then this will free the page.
	 */
	move_to_lru(newpage);
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	if (result) {
		if (rc)
			*result = rc;
		else
			*result = page_to_nid(newpage);
	}
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	return rc;
}

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/*
 * migrate_pages
 *
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 * 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.
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 *
 * The function returns after 10 attempts or if no pages
 * are movable anymore because to has become empty
721
 * or no retryable pages exist anymore. All pages will be
G
Gabriel Craciunescu 已提交
722
 * returned to the LRU or freed.
C
Christoph Lameter 已提交
723
 *
724
 * Return: Number of pages not migrated or error code.
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Christoph Lameter 已提交
725
 */
726 727
int migrate_pages(struct list_head *from,
		new_page_t get_new_page, unsigned long private)
C
Christoph Lameter 已提交
728
{
729
	int retry = 1;
C
Christoph Lameter 已提交
730 731 732 733 734 735 736 737 738 739
	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;

740 741
	for(pass = 0; pass < 10 && retry; pass++) {
		retry = 0;
C
Christoph Lameter 已提交
742

743 744
		list_for_each_entry_safe(page, page2, from, lru) {
			cond_resched();
745

746 747
			rc = unmap_and_move(get_new_page, private,
						page, pass > 2);
748

749
			switch(rc) {
750 751
			case -ENOMEM:
				goto out;
752
			case -EAGAIN:
753
				retry++;
754 755 756 757
				break;
			case 0:
				break;
			default:
758 759
				/* Permanent failure */
				nr_failed++;
760
				break;
761
			}
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Christoph Lameter 已提交
762 763
		}
	}
764 765
	rc = 0;
out:
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Christoph Lameter 已提交
766 767 768
	if (!swapwrite)
		current->flags &= ~PF_SWAPWRITE;

769
	putback_lru_pages(from);
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Christoph Lameter 已提交
770

771 772
	if (rc)
		return rc;
C
Christoph Lameter 已提交
773

774
	return nr_failed + retry;
C
Christoph Lameter 已提交
775
}
776

777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800
#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;

801 802
	return alloc_pages_node(pm->node,
				GFP_HIGHUSER_MOVABLE | GFP_THISNODE, 0);
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
}

/*
 * 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.
 */
static int do_move_pages(struct mm_struct *mm, struct page_to_node *pm,
				int migrate_all)
{
	int err;
	struct page_to_node *pp;
	LIST_HEAD(pagelist);

	down_read(&mm->mmap_sem);

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

		/*
		 * A valid page pointer that will not match any of the
		 * pages that will be moved.
		 */
		pp->page = ZERO_PAGE(0);

		err = -EFAULT;
		vma = find_vma(mm, pp->addr);
835
		if (!vma || !vma_migratable(vma))
836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940
			goto set_status;

		page = follow_page(vma, pp->addr, FOLL_GET);
		err = -ENOENT;
		if (!page)
			goto set_status;

		if (PageReserved(page))		/* Check for zero page */
			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;

		err = isolate_lru_page(page, &pagelist);
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;
	}

	if (!list_empty(&pagelist))
		err = migrate_pages(&pagelist, new_page_node,
				(unsigned long)pm);
	else
		err = -ENOENT;

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

/*
 * Determine the nodes of a list of pages. The addr in the pm array
 * must have been set to the virtual address of which we want to determine
 * the node number.
 */
static int do_pages_stat(struct mm_struct *mm, struct page_to_node *pm)
{
	down_read(&mm->mmap_sem);

	for ( ; pm->node != MAX_NUMNODES; pm++) {
		struct vm_area_struct *vma;
		struct page *page;
		int err;

		err = -EFAULT;
		vma = find_vma(mm, pm->addr);
		if (!vma)
			goto set_status;

		page = follow_page(vma, pm->addr, 0);
		err = -ENOENT;
		/* Use PageReserved to check for zero page */
		if (!page || PageReserved(page))
			goto set_status;

		err = page_to_nid(page);
set_status:
		pm->status = err;
	}

	up_read(&mm->mmap_sem);
	return 0;
}

/*
 * Move a list of pages in the address space of the currently executing
 * process.
 */
asmlinkage long sys_move_pages(pid_t pid, unsigned long nr_pages,
			const void __user * __user *pages,
			const int __user *nodes,
			int __user *status, int flags)
{
	int err = 0;
	int i;
	struct task_struct *task;
	nodemask_t task_nodes;
	struct mm_struct *mm;
	struct page_to_node *pm = NULL;

	/* 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);
941
	task = pid ? find_task_by_vpid(pid) : current;
942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964
	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.
	 */
	if ((current->euid != task->suid) && (current->euid != task->uid) &&
	    (current->uid != task->suid) && (current->uid != task->uid) &&
	    !capable(CAP_SYS_NICE)) {
		err = -EPERM;
		goto out2;
	}

965 966 967 968 969
 	err = security_task_movememory(task);
 	if (err)
 		goto out2;


970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988
	task_nodes = cpuset_mems_allowed(task);

	/* Limit nr_pages so that the multiplication may not overflow */
	if (nr_pages >= ULONG_MAX / sizeof(struct page_to_node) - 1) {
		err = -E2BIG;
		goto out2;
	}

	pm = vmalloc((nr_pages + 1) * sizeof(struct page_to_node));
	if (!pm) {
		err = -ENOMEM;
		goto out2;
	}

	/*
	 * Get parameters from user space and initialize the pm
	 * array. Return various errors if the user did something wrong.
	 */
	for (i = 0; i < nr_pages; i++) {
A
Al Viro 已提交
989
		const void __user *p;
990 991 992 993 994 995 996 997 998 999 1000 1001 1002

		err = -EFAULT;
		if (get_user(p, pages + i))
			goto out;

		pm[i].addr = (unsigned long)p;
		if (nodes) {
			int node;

			if (get_user(node, nodes + i))
				goto out;

			err = -ENODEV;
1003
			if (!node_state(node, N_HIGH_MEMORY))
1004 1005 1006 1007 1008 1009 1010
				goto out;

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

			pm[i].node = node;
1011 1012
		} else
			pm[i].node = 0;	/* anything to not match MAX_NUMNODES */
1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035
	}
	/* End marker */
	pm[nr_pages].node = MAX_NUMNODES;

	if (nodes)
		err = do_move_pages(mm, pm, flags & MPOL_MF_MOVE_ALL);
	else
		err = do_pages_stat(mm, pm);

	if (err >= 0)
		/* Return status information */
		for (i = 0; i < nr_pages; i++)
			if (put_user(pm[i].status, status + i))
				err = -EFAULT;

out:
	vfree(pm);
out2:
	mmput(mm);
	return err;
}
#endif

1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055
/*
 * 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;

 	for(vma = mm->mmap; vma->vm_next && !err; vma = vma->vm_next) {
 		if (vma->vm_ops && vma->vm_ops->migrate) {
 			err = vma->vm_ops->migrate(vma, to, from, flags);
 			if (err)
 				break;
 		}
 	}
 	return err;
}