From b20a35035f983f4ac7e29c4a68f30e43510007e0 Mon Sep 17 00:00:00 2001 From: Christoph Lameter Date: Wed, 22 Mar 2006 00:09:12 -0800 Subject: [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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/migrate.c | 655 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 655 insertions(+) create mode 100644 mm/migrate.c (limited to 'mm/migrate.c') diff --git a/mm/migrate.c b/mm/migrate.c new file mode 100644 index 000000000000..09f6e4aa87fc --- /dev/null +++ b/mm/migrate.c @@ -0,0 +1,655 @@ +/* + * 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 + * Hirokazu Takahashi + * Dave Hansen + * Christoph Lameter + */ + +#include +#include +#include +#include +#include /* for try_to_release_page(), + buffer_heads_over_limit */ +#include +#include +#include +#include +#include +#include +#include + +#include "internal.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; +} +EXPORT_SYMBOL(swap_page); + +/* + * 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 1; + } + + /* + * 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. + */ +int migrate_pages(struct list_head *from, struct list_head *to, + struct list_head *moved, struct list_head *failed) +{ + int retry; + 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; + +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; +} + +/* + * 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; +} -- cgit v1.2.3