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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>
#include <linux/pagemap.h>
#include <linux/buffer_head.h>
#include <linux/mm_inline.h>
#include <linux/pagevec.h>
#include <linux/rmap.h>
#include <linux/topology.h>
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/swapops.h>
#include "internal.h"
/* The maximum number of pages to take off the LRU for migration */
#define MIGRATE_CHUNK_SIZE 256
#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);
if (PageLRU(page)) {
ret = 0;
get_page(page);
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;
}
/*
* migrate_prep() needs to be called after we have compiled the list of pages
* to be migrated using isolate_lru_page() but before we begin a series of calls
* to migrate_pages().
*/
int migrate_prep(void)
{
/* Must have swap device for migration */
if (nr_swap_pages <= 0)
return -ENODEV;
/*
* 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)
{
list_del(&page->lru);
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) {
move_to_lru(page);
count++;
}
return count;
}
/*
* Non migratable page
*/
int fail_migrate_page(struct page *newpage, struct page *page)
{
return -EIO;
}
EXPORT_SYMBOL(fail_migrate_page);
/*
* swapout a single page
* page is locked upon entry, unlocked on exit
*/
static int swap_page(struct page *page)
{
struct address_space *mapping = page_mapping(page);
if (page_mapped(page) && mapping)
if (try_to_unmap(page, 1) != SWAP_SUCCESS)
goto unlock_retry;
if (PageDirty(page)) {
/* Page is dirty, try to write it out here */
switch(pageout(page, mapping)) {
case PAGE_KEEP:
case PAGE_ACTIVATE:
goto unlock_retry;
case PAGE_SUCCESS:
goto retry;
case PAGE_CLEAN:
; /* try to free the page below */
}
}
if (PagePrivate(page)) {
if (!try_to_release_page(page, GFP_KERNEL) ||
(!mapping && page_count(page) == 1))
goto unlock_retry;
}
if (remove_mapping(mapping, page)) {
/* Success */
unlock_page(page);
return 0;
}
unlock_retry:
unlock_page(page);
retry:
return -EAGAIN;
}
/*
* Remove references for a page and establish the new page with the correct
* basic settings to be able to stop accesses to the page.
*/
int migrate_page_remove_references(struct page *newpage,
struct page *page, int nr_refs)
{
struct address_space *mapping = page_mapping(page);
struct page **radix_pointer;
/*
* Avoid doing any of the following work if the page count
* indicates that the page is in use or truncate has removed
* the page.
*/
if (!mapping || page_mapcount(page) + nr_refs != page_count(page))
return -EAGAIN;
/*
* Establish swap ptes for anonymous pages or destroy pte
* maps for files.
*
* In order to reestablish file backed mappings the fault handlers
* will take the radix tree_lock which may then be used to stop
* processses from accessing this page until the new page is ready.
*
* A process accessing via a swap pte (an anonymous page) will take a
* page_lock on the old page which will block the process until the
* migration attempt is complete. At that time the PageSwapCache bit
* will be examined. If the page was migrated then the PageSwapCache
* bit will be clear and the operation to retrieve the page will be
* retried which will find the new page in the radix tree. Then a new
* direct mapping may be generated based on the radix tree contents.
*
* If the page was not migrated then the PageSwapCache bit
* is still set and the operation may continue.
*/
if (try_to_unmap(page, 1) == SWAP_FAIL)
/* A vma has VM_LOCKED set -> permanent failure */
return -EPERM;
/*
* Give up if we were unable to remove all mappings.
*/
if (page_mapcount(page))
return -EAGAIN;
write_lock_irq(&mapping->tree_lock);
radix_pointer = (struct page **)radix_tree_lookup_slot(
&mapping->page_tree,
page_index(page));
if (!page_mapping(page) || page_count(page) != nr_refs ||
*radix_pointer != page) {
write_unlock_irq(&mapping->tree_lock);
return -EAGAIN;
}
/*
* Now we know that no one else is looking at the page.
*
* Certain minimal information about a page must be available
* in order for other subsystems to properly handle the page if they
* find it through the radix tree update before we are finished
* copying the page.
*/
get_page(newpage);
newpage->index = page->index;
newpage->mapping = page->mapping;
if (PageSwapCache(page)) {
SetPageSwapCache(newpage);
set_page_private(newpage, page_private(page));
}
*radix_pointer = newpage;
__put_page(page);
write_unlock_irq(&mapping->tree_lock);
return 0;
}
EXPORT_SYMBOL(migrate_page_remove_references);
/*
* Copy the page to its new location
*/
void migrate_page_copy(struct page *newpage, struct page *page)
{
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);
}
ClearPageSwapCache(page);
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);
}
EXPORT_SYMBOL(migrate_page_copy);
/*
* Common logic to directly migrate a single page suitable for
* pages that do not use PagePrivate.
*
* Pages are locked upon entry and exit.
*/
int migrate_page(struct page *newpage, struct page *page)
{
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