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@@ -0,0 +1,655 @@
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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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+
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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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+
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+#include "internal.h"
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+
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+#include "internal.h"
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+
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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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+
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+#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
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+
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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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+
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+ if (PageLRU(page)) {
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+ struct zone *zone = page_zone(page);
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+
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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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+/*
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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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+ /*
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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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+
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+ return 0;
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+}
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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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+/*
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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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+
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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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+/*
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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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+/*
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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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+
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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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+
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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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+
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+ case PAGE_SUCCESS:
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+ goto retry;
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+
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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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+
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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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+
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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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+
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+unlock_retry:
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+ unlock_page(page);
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+
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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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+/*
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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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+ /*
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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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+ /*
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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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+ /*
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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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+
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+ write_lock_irq(&mapping->tree_lock);
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+
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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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+
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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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+ /*
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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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+
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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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+
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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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+/*
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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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+
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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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+
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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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+
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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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+ /*
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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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+/*
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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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+
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+ BUG_ON(PageWriteback(page)); /* Writeback must be complete */
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+
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+ rc = migrate_page_remove_references(newpage, page, 2);
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+
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+ if (rc)
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+ return rc;
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+
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+ migrate_page_copy(newpage, page);
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+
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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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+/*
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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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+
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+ if (!swapwrite)
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+ current->flags |= PF_SWAPWRITE;
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+
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+redo:
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+ retry = 0;
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+
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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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+
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+ cond_resched();
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+
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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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+
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+ if (to && list_empty(to))
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+ break;
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+
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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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+ /*
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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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+ /*
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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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+
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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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+
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+ newpage = lru_to_page(to);
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+ lock_page(newpage);
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+
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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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+
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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.
|
|
|
+ */
|
|
|
+ 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;
|
|
|
+}
|
Christoph Lameter