[PATCH] page migration reorg
Centralize the page migration functions in anticipation of additional
tinkering. Creates a new file mm/migrate.c
1. Extract buffer_migrate_page() from fs/buffer.c
2. Extract central migration code from vmscan.c
3. Extract some components from mempolicy.c
4. Export pageout() and remove_from_swap() from vmscan.c
5. Make it possible to configure NUMA systems without page migration
and non-NUMA systems with page migration.
I had to so some #ifdeffing in mempolicy.c that may need a cleanup.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 548e023..fd572bb 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -42,18 +42,6 @@
#include "internal.h"
-/* possible outcome of pageout() */
-typedef enum {
- /* failed to write page out, page is locked */
- PAGE_KEEP,
- /* move page to the active list, page is locked */
- PAGE_ACTIVATE,
- /* page has been sent to the disk successfully, page is unlocked */
- PAGE_SUCCESS,
- /* page is clean and locked */
- PAGE_CLEAN,
-} pageout_t;
-
struct scan_control {
/* Incremented by the number of inactive pages that were scanned */
unsigned long nr_scanned;
@@ -304,7 +292,7 @@
* pageout is called by shrink_page_list() for each dirty page.
* Calls ->writepage().
*/
-static pageout_t pageout(struct page *page, struct address_space *mapping)
+pageout_t pageout(struct page *page, struct address_space *mapping)
{
/*
* If the page is dirty, only perform writeback if that write
@@ -372,7 +360,7 @@
return PAGE_CLEAN;
}
-static int remove_mapping(struct address_space *mapping, struct page *page)
+int remove_mapping(struct address_space *mapping, struct page *page)
{
if (!mapping)
return 0; /* truncate got there first */
@@ -570,481 +558,6 @@
return nr_reclaimed;
}
-#ifdef CONFIG_MIGRATION
-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.
- */
-unsigned long putback_lru_pages(struct list_head *l)
-{
- struct page *page;
- struct page *page2;
- unsigned long 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;
-}
-EXPORT_SYMBOL(swap_page);
-
-/*
- * 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>
- */
-
-/*
- * 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)
-{
- int rc;
-
- BUG_ON(PageWriteback(page)); /* Writeback must be complete */
-
- rc = migrate_page_remove_references(newpage, page, 2);
-
- if (rc)
- return rc;
-
- migrate_page_copy(newpage, page);
-
- /*
- * Remove auxiliary swap entries and replace
- * them with real ptes.
- *
- * Note that a real pte entry will allow processes that are not
- * waiting on the page lock to use the new page via the page tables
- * before the new page is unlocked.
- */
- remove_from_swap(newpage);
- return 0;
-}
-EXPORT_SYMBOL(migrate_page);
-
-/*
- * migrate_pages
- *
- * Two lists are passed to this function. The first list
- * contains the pages isolated from the LRU to be migrated.
- * The second list contains new pages that the pages isolated
- * can be moved to. If the second list is NULL then all
- * pages are swapped out.
- *
- * The function returns after 10 attempts or if no pages
- * are movable anymore because to has become empty
- * or no retryable pages exist anymore.
- *
- * Return: Number of pages not migrated when "to" ran empty.
- */
-unsigned long migrate_pages(struct list_head *from, struct list_head *to,
- struct list_head *moved, struct list_head *failed)
-{
- unsigned long retry;
- unsigned long 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;
-
-redo:
- retry = 0;
-
- list_for_each_entry_safe(page, page2, from, lru) {
- struct page *newpage = NULL;
- struct address_space *mapping;
-
- cond_resched();
-
- rc = 0;
- if (page_count(page) == 1)
- /* page was freed from under us. So we are done. */
- goto next;
-
- if (to && list_empty(to))
- break;
-
- /*
- * Skip locked pages during the first two passes to give the
- * functions holding the lock time to release the page. Later we
- * use lock_page() to have a higher chance of acquiring the
- * lock.
- */
- rc = -EAGAIN;
- if (pass > 2)
- lock_page(page);
- else
- if (TestSetPageLocked(page))
- goto next;
-
- /*
- * Only wait on writeback if we have already done a pass where
- * we we may have triggered writeouts for lots of pages.
- */
- if (pass > 0) {
- wait_on_page_writeback(page);
- } else {
- if (PageWriteback(page))
- goto unlock_page;
- }
-
- /*
- * Anonymous pages must have swap cache references otherwise
- * the information contained in the page maps cannot be
- * preserved.
- */
- if (PageAnon(page) && !PageSwapCache(page)) {
- if (!add_to_swap(page, GFP_KERNEL)) {
- rc = -ENOMEM;
- goto unlock_page;
- }
- }
-
- if (!to) {
- rc = swap_page(page);
- goto next;
- }
-
- newpage = lru_to_page(to);
- lock_page(newpage);
-
- /*
- * Pages are properly locked and writeback is complete.
- * Try to migrate the page.
- */
- mapping = page_mapping(page);
- if (!mapping)
- goto unlock_both;
-
- 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(newpage, page);
- goto unlock_both;
- }
-
- /*
- * Default handling if a filesystem does not provide
- * a migration function. We can only migrate clean
- * pages so try to write out any dirty pages first.
- */
- if (PageDirty(page)) {
- switch (pageout(page, mapping)) {
- case PAGE_KEEP:
- case PAGE_ACTIVATE:
- goto unlock_both;
-
- case PAGE_SUCCESS:
- unlock_page(newpage);
- goto next;
-
- case PAGE_CLEAN:
- ; /* try to migrate the page below */
- }
- }
-
- /*
- * Buffers are managed in a filesystem specific way.
- * We must have no buffers or drop them.
- */
- if (!page_has_buffers(page) ||
- 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;
-}
-
-/*
- * Isolate one page from the LRU lists and put it on the
- * indicated list with elevated refcount.
- *
- * Result:
- * 0 = page not on LRU list
- * 1 = page removed from LRU list and added to the specified list.
- */
-int isolate_lru_page(struct page *page)
-{
- int ret = 0;
-
- if (PageLRU(page)) {
- struct zone *zone = page_zone(page);
- spin_lock_irq(&zone->lru_lock);
- if (PageLRU(page)) {
- ret = 1;
- get_page(page);
- ClearPageLRU(page);
- if (PageActive(page))
- del_page_from_active_list(zone, page);
- else
- del_page_from_inactive_list(zone, page);
- }
- spin_unlock_irq(&zone->lru_lock);
- }
-
- return ret;
-}
-#endif
-
/*
* zone->lru_lock is heavily contended. Some of the functions that
* shrink the lists perform better by taking out a batch of pages