page = migration_entry_to_page(entry);
- get_page(page);
+ /*
+ * Once radix-tree replacement of page migration started, page_count
+ * *must* be zero. And, we don't want to call wait_on_page_locked()
+ * against a page without get_page().
+ * So, we use get_page_unless_zero(), here. Even failed, page fault
+ * will occur again.
+ */
+ if (!get_page_unless_zero(page))
+ goto out;
pte_unmap_unlock(ptep, ptl);
wait_on_page_locked(page);
put_page(page);
static int migrate_page_move_mapping(struct address_space *mapping,
struct page *newpage, struct page *page)
{
+ int expected_count;
void **pslot;
if (!mapping) {
return 0;
}
- write_lock_irq(&mapping->tree_lock);
+ spin_lock_irq(&mapping->tree_lock);
pslot = radix_tree_lookup_slot(&mapping->page_tree,
page_index(page));
- if (page_count(page) != 2 + !!PagePrivate(page) ||
+ expected_count = 2 + !!PagePrivate(page);
+ if (page_count(page) != expected_count ||
(struct page *)radix_tree_deref_slot(pslot) != page) {
- write_unlock_irq(&mapping->tree_lock);
+ spin_unlock_irq(&mapping->tree_lock);
+ return -EAGAIN;
+ }
+
+ if (!page_freeze_refs(page, expected_count)) {
+ spin_unlock_irq(&mapping->tree_lock);
return -EAGAIN;
}
radix_tree_replace_slot(pslot, newpage);
+ page_unfreeze_refs(page, expected_count);
/*
* Drop cache reference from old page.
* We know this isn't the last reference.
__dec_zone_page_state(page, NR_FILE_PAGES);
__inc_zone_page_state(newpage, NR_FILE_PAGES);
- write_unlock_irq(&mapping->tree_lock);
- if (!PageSwapCache(newpage)) {
+ spin_unlock_irq(&mapping->tree_lock);
+ if (!PageSwapCache(newpage))
mem_cgroup_uncharge_cache_page(page);
- }
return 0;
}
* establishing additional references. We are the only one
* holding a reference to the new page at this point.
*/
- if (TestSetPageLocked(newpage))
+ if (!trylock_page(newpage))
BUG();
/* Prepare mapping for the new page.*/
BUG_ON(charge);
rc = -EAGAIN;
- if (TestSetPageLocked(page)) {
+ if (!trylock_page(page)) {
if (!force)
goto move_newpage;
lock_page(page);