1 files changed, 23 insertions, 2 deletions

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 5a37e2055717..67a33a5a1a93 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -604,15 +604,36 @@ static void bdi_wb_shutdown(struct backing_dev_info *bdi)
 
         /*
          * Finally, kill the kernel threads. We don't need to be RCU
-         * safe anymore, since the bdi is gone from visibility.
+         * safe anymore, since the bdi is gone from visibility. Force
+         * unfreeze of the thread before calling kthread_stop(), otherwise
+         * it would never exet if it is currently stuck in the refrigerator.
          */
-        list_for_each_entry(wb, &bdi->wb_list, list)
+        list_for_each_entry(wb, &bdi->wb_list, list) {
+                wb->task->flags &= ~PF_FROZEN;
                 kthread_stop(wb->task);
+        }
+}
+
+/*
+ * This bdi is going away now, make sure that no super_blocks point to it
+ */
+static void bdi_prune_sb(struct backing_dev_info *bdi)
+{
+        struct super_block *sb;
+
+        spin_lock(&sb_lock);
+        list_for_each_entry(sb, &super_blocks, s_list) {
+                if (sb->s_bdi == bdi)
+                        sb->s_bdi = NULL;
+        }
+        spin_unlock(&sb_lock);
 }
 
 void bdi_unregister(struct backing_dev_info *bdi)
 {
         if (bdi->dev) {
+                bdi_prune_sb(bdi);
+
                 if (!bdi_cap_flush_forker(bdi))
                         bdi_wb_shutdown(bdi);
                 bdi_debug_unregister(bdi);