1 files changed, 16 insertions, 24 deletions

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 12a992b62576..0ae0df55000b 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -40,7 +40,7 @@ LIST_HEAD(bdi_list);
 /* bdi_wq serves all asynchronous writeback tasks */
 struct workqueue_struct *bdi_wq;
 
-void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2)
+static void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2)
 {
         if (wb1 < wb2) {
                 spin_lock(&wb1->list_lock);
@@ -376,13 +376,7 @@ static void bdi_wb_shutdown(struct backing_dev_info *bdi)
         mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
         flush_delayed_work(&bdi->wb.dwork);
         WARN_ON(!list_empty(&bdi->work_list));
-
-        /*
-         * This shouldn't be necessary unless @bdi for some reason has
-         * unflushed dirty IO after work_list is drained.  Do it anyway
-         * just in case.
-         */
-        cancel_delayed_work_sync(&bdi->wb.dwork);
+        WARN_ON(delayed_work_pending(&bdi->wb.dwork));
 }
 
 /*
@@ -402,21 +396,15 @@ static void bdi_prune_sb(struct backing_dev_info *bdi)
 
 void bdi_unregister(struct backing_dev_info *bdi)
 {
-        struct device *dev = bdi->dev;
-
-        if (dev) {
+        if (bdi->dev) {
                 bdi_set_min_ratio(bdi, 0);
                 trace_writeback_bdi_unregister(bdi);
                 bdi_prune_sb(bdi);
 
                 bdi_wb_shutdown(bdi);
                 bdi_debug_unregister(bdi);
-
-                spin_lock_bh(&bdi->wb_lock);
+                device_unregister(bdi->dev);
                 bdi->dev = NULL;
-                spin_unlock_bh(&bdi->wb_lock);
-
-                device_unregister(dev);
         }
 }
 EXPORT_SYMBOL(bdi_unregister);
@@ -487,8 +475,17 @@ void bdi_destroy(struct backing_dev_info *bdi)
         int i;
 
         /*
-         * Splice our entries to the default_backing_dev_info, if this
-         * bdi disappears
+         * Splice our entries to the default_backing_dev_info.  This
+         * condition shouldn't happen.  @wb must be empty at this point and
+         * dirty inodes on it might cause other issues.  This workaround is
+         * added by ce5f8e779519 ("writeback: splice dirty inode entries to
+         * default bdi on bdi_destroy()") without root-causing the issue.
+         *
+         * http://lkml.kernel.org/g/1253038617-30204-11-git-send-email-jens.axboe@oracle.com
+         * http://thread.gmane.org/gmane.linux.file-systems/35341/focus=35350
+         *
+         * We should probably add WARN_ON() to find out whether it still
+         * happens and track it down if so.
          */
         if (bdi_has_dirty_io(bdi)) {
                 struct bdi_writeback *dst = &default_backing_dev_info.wb;
@@ -503,12 +500,7 @@ void bdi_destroy(struct backing_dev_info *bdi)
 
         bdi_unregister(bdi);
 
-        /*
-         * If bdi_unregister() had already been called earlier, the dwork
-         * could still be pending because bdi_prune_sb() can race with the
-         * bdi_wakeup_thread_delayed() calls from __mark_inode_dirty().
-         */
-        cancel_delayed_work_sync(&bdi->wb.dwork);
+        WARN_ON(delayed_work_pending(&bdi->wb.dwork));
 
         for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
                 percpu_counter_destroy(&bdi->bdi_stat[i]);