2 files changed, 25 insertions, 7 deletions

diff --git a/mm/migrate.c b/mm/migrate.c
index 4ee4ccacf986..857a987e3690 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);
 
diff --git a/mm/truncate.c b/mm/truncate.c
index 9838c050e2dd..c35c49e54fb6 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -84,7 +84,7 @@ EXPORT_SYMBOL(cancel_dirty_page);
 
 /*
  * If truncate cannot remove the fs-private metadata from the page, the page
- * becomes anonymous.  It will be left on the LRU and may even be mapped into
+ * becomes orphaned.  It will be left on the LRU and may even be mapped into
  * user pagetables if we're racing with filemap_fault().
  *
  * We need to bale out if page->mapping is no longer equal to the original