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-rw-r--r--mm/migrate.c30
1 files changed, 24 insertions, 6 deletions
diff --git a/mm/migrate.c b/mm/migrate.c
index 4ee4ccacf98..857a987e369 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -640,15 +640,33 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
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
- * and treated as swapcache but has no rmap yet.
- * Calling try_to_unmap() against a page->mapping==NULL page is
- * BUG. So handle it here.
+ * Corner case handling:
+ * 1. When a new swap-cache page is read into, it is added to the LRU
+ * and treated as swapcache but it has no rmap yet.
+ * Calling try_to_unmap() against a page->mapping==NULL page will
+ * trigger a BUG. So handle it here.
+ * 2. An orphaned page (see truncate_complete_page) might have
+ * fs-private metadata. The page can be picked up due to memory
+ * offlining. Everywhere else except page reclaim, the page is
+ * invisible to the vm, so the page can not be migrated. So try to
+ * free the metadata, so the page can be freed.
*/
- if (!page->mapping)
+ if (!page->mapping) {
+ if (!PageAnon(page) && PagePrivate(page)) {
+ /*
+ * Go direct to try_to_free_buffers() here because
+ * a) that's what try_to_release_page() would do anyway
+ * b) we may be under rcu_read_lock() here, so we can't
+ * use GFP_KERNEL which is what try_to_release_page()
+ * needs to be effective.
+ */
+ try_to_free_buffers(page);
+ }
goto rcu_unlock;
+ }
+
/* Establish migration ptes or remove ptes */
try_to_unmap(page, 1);