summaryrefslogtreecommitdiff
path: root/mm/migrate.c
diff options
context:
space:
mode:
Diffstat (limited to 'mm/migrate.c')
-rw-r--r--mm/migrate.c74
1 files changed, 60 insertions, 14 deletions
diff --git a/mm/migrate.c b/mm/migrate.c
index d3f3f7f81075..4205b1d6049e 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -40,7 +40,8 @@
/*
* migrate_prep() needs to be called before we start compiling a list of pages
- * to be migrated using isolate_lru_page().
+ * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
+ * undesirable, use migrate_prep_local()
*/
int migrate_prep(void)
{
@@ -55,26 +56,29 @@ int migrate_prep(void)
return 0;
}
+/* Do the necessary work of migrate_prep but not if it involves other CPUs */
+int migrate_prep_local(void)
+{
+ lru_add_drain();
+
+ return 0;
+}
+
/*
* Add isolated pages on the list back to the LRU under page lock
* to avoid leaking evictable pages back onto unevictable list.
- *
- * returns the number of pages put back.
*/
-int putback_lru_pages(struct list_head *l)
+void 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) {
list_del(&page->lru);
dec_zone_page_state(page, NR_ISOLATED_ANON +
page_is_file_cache(page));
putback_lru_page(page);
- count++;
}
- return count;
}
/*
@@ -490,7 +494,8 @@ static int fallback_migrate_page(struct address_space *mapping,
* < 0 - error code
* == 0 - success
*/
-static int move_to_new_page(struct page *newpage, struct page *page)
+static int move_to_new_page(struct page *newpage, struct page *page,
+ int remap_swapcache)
{
struct address_space *mapping;
int rc;
@@ -525,10 +530,12 @@ static int move_to_new_page(struct page *newpage, struct page *page)
else
rc = fallback_migrate_page(mapping, newpage, page);
- if (!rc)
- remove_migration_ptes(page, newpage);
- else
+ if (rc) {
newpage->mapping = NULL;
+ } else {
+ if (remap_swapcache)
+ remove_migration_ptes(page, newpage);
+ }
unlock_page(newpage);
@@ -545,9 +552,11 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
int rc = 0;
int *result = NULL;
struct page *newpage = get_new_page(page, private, &result);
+ int remap_swapcache = 1;
int rcu_locked = 0;
int charge = 0;
struct mem_cgroup *mem = NULL;
+ struct anon_vma *anon_vma = NULL;
if (!newpage)
return -ENOMEM;
@@ -581,7 +590,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
}
/* charge against new page */
- charge = mem_cgroup_prepare_migration(page, &mem);
+ charge = mem_cgroup_prepare_migration(page, newpage, &mem);
if (charge == -ENOMEM) {
rc = -ENOMEM;
goto unlock;
@@ -604,6 +613,34 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
if (PageAnon(page)) {
rcu_read_lock();
rcu_locked = 1;
+
+ /* Determine how to safely use anon_vma */
+ if (!page_mapped(page)) {
+ if (!PageSwapCache(page))
+ goto rcu_unlock;
+
+ /*
+ * We cannot be sure that the anon_vma of an unmapped
+ * swapcache page is safe to use because we don't
+ * know in advance if the VMA that this page belonged
+ * to still exists. If the VMA and others sharing the
+ * data have been freed, then the anon_vma could
+ * already be invalid.
+ *
+ * To avoid this possibility, swapcache pages get
+ * migrated but are not remapped when migration
+ * completes
+ */
+ remap_swapcache = 0;
+ } else {
+ /*
+ * Take a reference count on the anon_vma if the
+ * page is mapped so that it is guaranteed to
+ * exist when the page is remapped later
+ */
+ anon_vma = page_anon_vma(page);
+ atomic_inc(&anon_vma->external_refcount);
+ }
}
/*
@@ -638,11 +675,20 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
skip_unmap:
if (!page_mapped(page))
- rc = move_to_new_page(newpage, page);
+ rc = move_to_new_page(newpage, page, remap_swapcache);
- if (rc)
+ if (rc && remap_swapcache)
remove_migration_ptes(page, page);
rcu_unlock:
+
+ /* Drop an anon_vma reference if we took one */
+ if (anon_vma && atomic_dec_and_lock(&anon_vma->external_refcount, &anon_vma->lock)) {
+ int empty = list_empty(&anon_vma->head);
+ spin_unlock(&anon_vma->lock);
+ if (empty)
+ anon_vma_free(anon_vma);
+ }
+
if (rcu_locked)
rcu_read_unlock();
uncharge: