fix rcu_read_lock() in page migraton
In migration fallback path, write_page() or lock_page() will be called.
This causes sleep with holding rcu_read_lock().
For avoding that, just do rcu_lock if the page is Anon.(this is enough.)
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/migrate.c b/mm/migrate.c
index 37c73b9..e2fdbce 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -611,6 +611,7 @@
int rc = 0;
int *result = NULL;
struct page *newpage = get_new_page(page, private, &result);
+ int rcu_locked = 0;
if (!newpage)
return -ENOMEM;
@@ -636,8 +637,13 @@
* we cannot notice that anon_vma is freed while we migrates a page.
* This rcu_read_lock() delays freeing anon_vma pointer until the end
* of migration. File cache pages are no problem because of page_lock()
+ * File Caches may use write_page() or lock_page() in migration, then,
+ * just care Anon page here.
*/
- rcu_read_lock();
+ if (PageAnon(page)) {
+ rcu_read_lock();
+ rcu_locked = 1;
+ }
/*
* This is a corner case handling.
* When a new swap-cache is read into, it is linked to LRU
@@ -656,7 +662,8 @@
if (rc)
remove_migration_ptes(page, page);
rcu_unlock:
- rcu_read_unlock();
+ if (rcu_locked)
+ rcu_read_unlock();
unlock: