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656 lines
15 KiB
C
656 lines
15 KiB
C
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/*
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* Memory Migration functionality - linux/mm/migration.c
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*
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* Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter
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*
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* Page migration was first developed in the context of the memory hotplug
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* project. The main authors of the migration code are:
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*
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* IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
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* Hirokazu Takahashi <taka@valinux.co.jp>
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* Dave Hansen <haveblue@us.ibm.com>
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* Christoph Lameter <clameter@sgi.com>
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*/
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#include <linux/migrate.h>
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#include <linux/module.h>
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#include <linux/swap.h>
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#include <linux/pagemap.h>
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#include <linux/buffer_head.h> /* for try_to_release_page(),
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buffer_heads_over_limit */
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#include <linux/mm_inline.h>
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#include <linux/pagevec.h>
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#include <linux/rmap.h>
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#include <linux/topology.h>
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#include <linux/cpu.h>
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#include <linux/cpuset.h>
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#include <linux/swapops.h>
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#include "internal.h"
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#include "internal.h"
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/* The maximum number of pages to take off the LRU for migration */
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#define MIGRATE_CHUNK_SIZE 256
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#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
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/*
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* Isolate one page from the LRU lists. If successful put it onto
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* the indicated list with elevated page count.
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*
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* Result:
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* -EBUSY: page not on LRU list
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* 0: page removed from LRU list and added to the specified list.
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*/
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int isolate_lru_page(struct page *page, struct list_head *pagelist)
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{
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int ret = -EBUSY;
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if (PageLRU(page)) {
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struct zone *zone = page_zone(page);
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spin_lock_irq(&zone->lru_lock);
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if (PageLRU(page)) {
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ret = 0;
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get_page(page);
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ClearPageLRU(page);
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if (PageActive(page))
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del_page_from_active_list(zone, page);
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else
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del_page_from_inactive_list(zone, page);
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list_add_tail(&page->lru, pagelist);
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}
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spin_unlock_irq(&zone->lru_lock);
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}
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return ret;
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}
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/*
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* migrate_prep() needs to be called after we have compiled the list of pages
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* to be migrated using isolate_lru_page() but before we begin a series of calls
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* to migrate_pages().
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*/
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int migrate_prep(void)
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{
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/* Must have swap device for migration */
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if (nr_swap_pages <= 0)
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return -ENODEV;
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/*
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* Clear the LRU lists so pages can be isolated.
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* Note that pages may be moved off the LRU after we have
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* drained them. Those pages will fail to migrate like other
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* pages that may be busy.
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*/
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lru_add_drain_all();
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return 0;
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}
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static inline void move_to_lru(struct page *page)
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{
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list_del(&page->lru);
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if (PageActive(page)) {
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/*
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* lru_cache_add_active checks that
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* the PG_active bit is off.
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*/
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ClearPageActive(page);
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lru_cache_add_active(page);
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} else {
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lru_cache_add(page);
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}
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put_page(page);
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}
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/*
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* Add isolated pages on the list back to the LRU.
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*
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* returns the number of pages put back.
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*/
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int putback_lru_pages(struct list_head *l)
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{
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struct page *page;
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struct page *page2;
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int count = 0;
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list_for_each_entry_safe(page, page2, l, lru) {
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move_to_lru(page);
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count++;
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}
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return count;
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}
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/*
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* Non migratable page
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*/
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int fail_migrate_page(struct page *newpage, struct page *page)
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{
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return -EIO;
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}
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EXPORT_SYMBOL(fail_migrate_page);
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/*
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* swapout a single page
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* page is locked upon entry, unlocked on exit
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*/
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static int swap_page(struct page *page)
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{
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struct address_space *mapping = page_mapping(page);
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if (page_mapped(page) && mapping)
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if (try_to_unmap(page, 1) != SWAP_SUCCESS)
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goto unlock_retry;
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if (PageDirty(page)) {
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/* Page is dirty, try to write it out here */
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switch(pageout(page, mapping)) {
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case PAGE_KEEP:
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case PAGE_ACTIVATE:
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goto unlock_retry;
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case PAGE_SUCCESS:
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goto retry;
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case PAGE_CLEAN:
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; /* try to free the page below */
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}
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}
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if (PagePrivate(page)) {
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if (!try_to_release_page(page, GFP_KERNEL) ||
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(!mapping && page_count(page) == 1))
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goto unlock_retry;
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}
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if (remove_mapping(mapping, page)) {
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/* Success */
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unlock_page(page);
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return 0;
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}
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unlock_retry:
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unlock_page(page);
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retry:
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return -EAGAIN;
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}
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EXPORT_SYMBOL(swap_page);
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/*
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* Remove references for a page and establish the new page with the correct
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* basic settings to be able to stop accesses to the page.
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*/
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int migrate_page_remove_references(struct page *newpage,
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struct page *page, int nr_refs)
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{
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struct address_space *mapping = page_mapping(page);
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struct page **radix_pointer;
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/*
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* Avoid doing any of the following work if the page count
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* indicates that the page is in use or truncate has removed
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* the page.
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*/
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if (!mapping || page_mapcount(page) + nr_refs != page_count(page))
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return -EAGAIN;
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/*
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* Establish swap ptes for anonymous pages or destroy pte
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* maps for files.
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*
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* In order to reestablish file backed mappings the fault handlers
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* will take the radix tree_lock which may then be used to stop
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* processses from accessing this page until the new page is ready.
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*
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* A process accessing via a swap pte (an anonymous page) will take a
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* page_lock on the old page which will block the process until the
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* migration attempt is complete. At that time the PageSwapCache bit
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* will be examined. If the page was migrated then the PageSwapCache
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* bit will be clear and the operation to retrieve the page will be
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* retried which will find the new page in the radix tree. Then a new
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* direct mapping may be generated based on the radix tree contents.
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*
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* If the page was not migrated then the PageSwapCache bit
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* is still set and the operation may continue.
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*/
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if (try_to_unmap(page, 1) == SWAP_FAIL)
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/* A vma has VM_LOCKED set -> permanent failure */
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return -EPERM;
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/*
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* Give up if we were unable to remove all mappings.
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*/
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if (page_mapcount(page))
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return -EAGAIN;
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write_lock_irq(&mapping->tree_lock);
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radix_pointer = (struct page **)radix_tree_lookup_slot(
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&mapping->page_tree,
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page_index(page));
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if (!page_mapping(page) || page_count(page) != nr_refs ||
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*radix_pointer != page) {
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write_unlock_irq(&mapping->tree_lock);
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return 1;
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}
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/*
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* Now we know that no one else is looking at the page.
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*
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* Certain minimal information about a page must be available
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* in order for other subsystems to properly handle the page if they
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* find it through the radix tree update before we are finished
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* copying the page.
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*/
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get_page(newpage);
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newpage->index = page->index;
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newpage->mapping = page->mapping;
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if (PageSwapCache(page)) {
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SetPageSwapCache(newpage);
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set_page_private(newpage, page_private(page));
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}
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*radix_pointer = newpage;
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__put_page(page);
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write_unlock_irq(&mapping->tree_lock);
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return 0;
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}
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EXPORT_SYMBOL(migrate_page_remove_references);
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/*
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* Copy the page to its new location
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*/
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void migrate_page_copy(struct page *newpage, struct page *page)
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{
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copy_highpage(newpage, page);
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if (PageError(page))
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SetPageError(newpage);
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if (PageReferenced(page))
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SetPageReferenced(newpage);
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if (PageUptodate(page))
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SetPageUptodate(newpage);
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if (PageActive(page))
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SetPageActive(newpage);
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if (PageChecked(page))
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SetPageChecked(newpage);
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if (PageMappedToDisk(page))
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SetPageMappedToDisk(newpage);
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if (PageDirty(page)) {
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clear_page_dirty_for_io(page);
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set_page_dirty(newpage);
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}
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ClearPageSwapCache(page);
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ClearPageActive(page);
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ClearPagePrivate(page);
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set_page_private(page, 0);
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page->mapping = NULL;
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/*
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* If any waiters have accumulated on the new page then
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* wake them up.
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*/
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if (PageWriteback(newpage))
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end_page_writeback(newpage);
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}
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EXPORT_SYMBOL(migrate_page_copy);
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/*
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* Common logic to directly migrate a single page suitable for
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* pages that do not use PagePrivate.
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*
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* Pages are locked upon entry and exit.
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*/
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int migrate_page(struct page *newpage, struct page *page)
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{
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int rc;
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BUG_ON(PageWriteback(page)); /* Writeback must be complete */
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rc = migrate_page_remove_references(newpage, page, 2);
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if (rc)
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return rc;
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migrate_page_copy(newpage, page);
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/*
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* Remove auxiliary swap entries and replace
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* them with real ptes.
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*
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* Note that a real pte entry will allow processes that are not
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* waiting on the page lock to use the new page via the page tables
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* before the new page is unlocked.
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*/
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remove_from_swap(newpage);
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return 0;
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}
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EXPORT_SYMBOL(migrate_page);
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/*
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* migrate_pages
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*
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* Two lists are passed to this function. The first list
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* contains the pages isolated from the LRU to be migrated.
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* The second list contains new pages that the pages isolated
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* can be moved to. If the second list is NULL then all
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* pages are swapped out.
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*
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* The function returns after 10 attempts or if no pages
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* are movable anymore because to has become empty
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* or no retryable pages exist anymore.
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*
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* Return: Number of pages not migrated when "to" ran empty.
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*/
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int migrate_pages(struct list_head *from, struct list_head *to,
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struct list_head *moved, struct list_head *failed)
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{
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int retry;
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int nr_failed = 0;
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int pass = 0;
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struct page *page;
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struct page *page2;
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int swapwrite = current->flags & PF_SWAPWRITE;
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int rc;
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if (!swapwrite)
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current->flags |= PF_SWAPWRITE;
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redo:
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retry = 0;
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list_for_each_entry_safe(page, page2, from, lru) {
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struct page *newpage = NULL;
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struct address_space *mapping;
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cond_resched();
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rc = 0;
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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 next;
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if (to && list_empty(to))
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break;
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/*
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* Skip locked pages during the first two passes to give the
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* functions holding the lock time to release the page. Later we
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* use lock_page() to have a higher chance of acquiring the
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* lock.
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*/
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rc = -EAGAIN;
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if (pass > 2)
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lock_page(page);
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else
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if (TestSetPageLocked(page))
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goto next;
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/*
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* Only wait on writeback if we have already done a pass where
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* we we may have triggered writeouts for lots of pages.
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*/
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if (pass > 0) {
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wait_on_page_writeback(page);
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} else {
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if (PageWriteback(page))
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goto unlock_page;
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}
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/*
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* Anonymous pages must have swap cache references otherwise
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* the information contained in the page maps cannot be
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* preserved.
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*/
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if (PageAnon(page) && !PageSwapCache(page)) {
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if (!add_to_swap(page, GFP_KERNEL)) {
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rc = -ENOMEM;
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goto unlock_page;
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}
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}
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if (!to) {
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rc = swap_page(page);
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goto next;
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}
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newpage = lru_to_page(to);
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lock_page(newpage);
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/*
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* Pages are properly locked and writeback is complete.
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* Try to migrate the page.
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*/
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mapping = page_mapping(page);
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if (!mapping)
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goto unlock_both;
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if (mapping->a_ops->migratepage) {
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/*
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* Most pages have a mapping and most filesystems
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* should provide a migration function. Anonymous
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* pages are part of swap space which also has its
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* own migration function. This is the most common
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* path for page migration.
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*/
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rc = mapping->a_ops->migratepage(newpage, page);
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goto unlock_both;
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}
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/*
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* Default handling if a filesystem does not provide
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* a migration function. We can only migrate clean
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* pages so try to write out any dirty pages first.
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*/
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if (PageDirty(page)) {
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switch (pageout(page, mapping)) {
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case PAGE_KEEP:
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case PAGE_ACTIVATE:
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goto unlock_both;
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case PAGE_SUCCESS:
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unlock_page(newpage);
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goto next;
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case PAGE_CLEAN:
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; /* try to migrate the page below */
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}
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}
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/*
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* Buffers are managed in a filesystem specific way.
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* We must have no buffers or drop them.
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*/
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if (!page_has_buffers(page) ||
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||
|
try_to_release_page(page, GFP_KERNEL)) {
|
||
|
rc = migrate_page(newpage, page);
|
||
|
goto unlock_both;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* On early passes with mapped pages simply
|
||
|
* retry. There may be a lock held for some
|
||
|
* buffers that may go away. Later
|
||
|
* swap them out.
|
||
|
*/
|
||
|
if (pass > 4) {
|
||
|
/*
|
||
|
* Persistently unable to drop buffers..... As a
|
||
|
* measure of last resort we fall back to
|
||
|
* swap_page().
|
||
|
*/
|
||
|
unlock_page(newpage);
|
||
|
newpage = NULL;
|
||
|
rc = swap_page(page);
|
||
|
goto next;
|
||
|
}
|
||
|
|
||
|
unlock_both:
|
||
|
unlock_page(newpage);
|
||
|
|
||
|
unlock_page:
|
||
|
unlock_page(page);
|
||
|
|
||
|
next:
|
||
|
if (rc == -EAGAIN) {
|
||
|
retry++;
|
||
|
} else if (rc) {
|
||
|
/* Permanent failure */
|
||
|
list_move(&page->lru, failed);
|
||
|
nr_failed++;
|
||
|
} else {
|
||
|
if (newpage) {
|
||
|
/* Successful migration. Return page to LRU */
|
||
|
move_to_lru(newpage);
|
||
|
}
|
||
|
list_move(&page->lru, moved);
|
||
|
}
|
||
|
}
|
||
|
if (retry && pass++ < 10)
|
||
|
goto redo;
|
||
|
|
||
|
if (!swapwrite)
|
||
|
current->flags &= ~PF_SWAPWRITE;
|
||
|
|
||
|
return nr_failed + retry;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Migration function for pages with buffers. This function can only be used
|
||
|
* if the underlying filesystem guarantees that no other references to "page"
|
||
|
* exist.
|
||
|
*/
|
||
|
int buffer_migrate_page(struct page *newpage, struct page *page)
|
||
|
{
|
||
|
struct address_space *mapping = page->mapping;
|
||
|
struct buffer_head *bh, *head;
|
||
|
int rc;
|
||
|
|
||
|
if (!mapping)
|
||
|
return -EAGAIN;
|
||
|
|
||
|
if (!page_has_buffers(page))
|
||
|
return migrate_page(newpage, page);
|
||
|
|
||
|
head = page_buffers(page);
|
||
|
|
||
|
rc = migrate_page_remove_references(newpage, page, 3);
|
||
|
|
||
|
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);
|
||
|
|
||
|
/*
|
||
|
* Migrate the list 'pagelist' of pages to a certain destination.
|
||
|
*
|
||
|
* Specify destination with either non-NULL vma or dest_node >= 0
|
||
|
* Return the number of pages not migrated or error code
|
||
|
*/
|
||
|
int migrate_pages_to(struct list_head *pagelist,
|
||
|
struct vm_area_struct *vma, int dest)
|
||
|
{
|
||
|
LIST_HEAD(newlist);
|
||
|
LIST_HEAD(moved);
|
||
|
LIST_HEAD(failed);
|
||
|
int err = 0;
|
||
|
unsigned long offset = 0;
|
||
|
int nr_pages;
|
||
|
struct page *page;
|
||
|
struct list_head *p;
|
||
|
|
||
|
redo:
|
||
|
nr_pages = 0;
|
||
|
list_for_each(p, pagelist) {
|
||
|
if (vma) {
|
||
|
/*
|
||
|
* The address passed to alloc_page_vma is used to
|
||
|
* generate the proper interleave behavior. We fake
|
||
|
* the address here by an increasing offset in order
|
||
|
* to get the proper distribution of pages.
|
||
|
*
|
||
|
* No decision has been made as to which page
|
||
|
* a certain old page is moved to so we cannot
|
||
|
* specify the correct address.
|
||
|
*/
|
||
|
page = alloc_page_vma(GFP_HIGHUSER, vma,
|
||
|
offset + vma->vm_start);
|
||
|
offset += PAGE_SIZE;
|
||
|
}
|
||
|
else
|
||
|
page = alloc_pages_node(dest, GFP_HIGHUSER, 0);
|
||
|
|
||
|
if (!page) {
|
||
|
err = -ENOMEM;
|
||
|
goto out;
|
||
|
}
|
||
|
list_add_tail(&page->lru, &newlist);
|
||
|
nr_pages++;
|
||
|
if (nr_pages > MIGRATE_CHUNK_SIZE)
|
||
|
break;
|
||
|
}
|
||
|
err = migrate_pages(pagelist, &newlist, &moved, &failed);
|
||
|
|
||
|
putback_lru_pages(&moved); /* Call release pages instead ?? */
|
||
|
|
||
|
if (err >= 0 && list_empty(&newlist) && !list_empty(pagelist))
|
||
|
goto redo;
|
||
|
out:
|
||
|
/* Return leftover allocated pages */
|
||
|
while (!list_empty(&newlist)) {
|
||
|
page = list_entry(newlist.next, struct page, lru);
|
||
|
list_del(&page->lru);
|
||
|
__free_page(page);
|
||
|
}
|
||
|
list_splice(&failed, pagelist);
|
||
|
if (err < 0)
|
||
|
return err;
|
||
|
|
||
|
/* Calculate number of leftover pages */
|
||
|
nr_pages = 0;
|
||
|
list_for_each(p, pagelist)
|
||
|
nr_pages++;
|
||
|
return nr_pages;
|
||
|
}
|